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Application of power ultrasound to cementitious materials: Advances, issues and perspectives

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Novel techniques such as power ultrasound (PUS) are currently under consideration to improve the hydration of cementitious materials and to promote the effectiveness of replacing supplementary cementitious materials; SCMs, in terms of mechanical, microstructural and transport properties. This could enhance the properties of cementitious composites, reduce the quantity of waste materials, as well as decreasing the CO2 footprint of cementitious materials. A handful of studies have investigated this promising field and little is known about the mechanisms by which the ultrasound acts in cement-based systems. This paper outlines the possible mechanisms involved on the effects of PUS as a method to promote cement hydration kinetics of Portland cement and binary blends. It also reviews and analyses previous research conducted mostly on the dispersing effects of PUS on the enhancement of pozzolanic reactivity of SCMs in cementitious systems. This review concludes with some perspectives on research needed to gain a fundamental understanding of this emerging field.
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Application of Power Ultrasound to Cementitious Materials: Advances, Issues and
Perspectives
Eshmaiel Ganjiana, Ahmad Ehsania, Timothy J. Masonb, Mark Tyrera
a Coventry University, Faculty of Engineering and Computing, Built & Natural Environment Research Centre, Coventry, UK
b Coventry University, Faculty of Health and Life Sciences, Coventry, UK
Abstract
Novel techniques such as power ultrasound (PUS) are currently under consideration to improve the hydration of cementitious materials
and to promote the effectiveness of replacing supplementary cementitious materials; SCMs, in terms of mechanical, microstructural and
transport properties. This could enhance the properties of cementitious composites, reduce the quantity of waste materials, as well as
decreasing the CO2 footprint of cementitious materials. A handful of studies have investigated this promising field and little is known
about the mechanisms by which the ultrasound acts in cement-based systems. This paper outlines the possible mechanisms involved on
the effects of PUS as a method to promote cement hydration kinetics of Portland cement and binary blends. It also reviews and analyses
previous research conducted mostly on the dispersing effects of PUS on the enhancement of pozzolanic reactivity of SCMs in cementitious
systems. This review concludes with some perspectives on research needed to gain a fundamental understanding of this emerging field.
Keywords: Power ultrasound, Cementitious materials, Supplementary cementitious materials, Hydration, Sonocrystallization
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Contents
1. Introduction .....................................................................................................................................................................................................................................
2. Ultrasonication .................................................................................................................................................................................................................................
2.1. Background ...............................................................................................................................................................................................................................
2.2. Conventional power ultrasound ........................................................................................................................................................................................
2.3. Acoustic cavitation phenomena and cement-based materials .............................................................................................................................
3. Mechanisms of Portland cement hydration .........................................................................................................................................................................
4. Effect of PUS on crystallisation of inorganic materials .....................................................................................................................................................
5. Influence of PUS on cementitious systems ...........................................................................................................................................................................
5.1. Challenges in cement-based systems .............................................................................................................................................................................
5.2. Postulated mechanisms concerning the phenomenon ............................................................................................................................................
5.3. Parameters influencing the cavitation phenomena in cement-based materials ............................................................................................
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6. Studies on the influence of PUS on cementitious materials ..........................................................................................................................................
6.1. Portland cement ......................................................................................................................................................................................................................
6.2. SCMs ............................................................................................................................................................................................................................................
7. Conclusion and future perspectives ........................................................................................................................................................................................
References ..............................................................................................................................................................................................................................................
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1. Introduction
Traditional Portland cement-based concrete has provided the foundation for the built environment for
almost 200 years. The focus of modern concrete structures is high performance, design for long lifetime and
to be aesthetically pleasing. According to the Mineral Products Association (MPA) cement fact sheet [1],
however, “the demands for sustainable development have placed a huge responsibility on the construction
sector to continually improve existing processes, products and practices, and to innovate in order to reduce
both energy used in service and embodied energy in products together with emission of greenhouse gases
during manufacture”.
The kinetic mechanisms of ordinary Portland cement (OPC) hydration and the complex, interdependent
chemical and microstructural phenomena which control the characterization of cement hydration products
have not been completely understood. However, major efforts have been placed on the sustainable use and
enhancing the perceived performance of OPC in cement-based composites.
Replacing part of Portland cement clinker by using alternative supplementary cementitious materials (SCMs)
like fly ash (PFA), ground granulated blast furnace slag (GGBS), silica fume (SF), calcined clays and natural
pozzolans in blended cements or utilising SCMs separately as a partially substitute additive in mortar/concrete
systems represents a viable solution to reduce carbon footprint [2]. A few benefits have been investigated in
cement-based materials incorporating SCMs including the improvement in consistency and the fresh concrete
properties [3], decreased hydration heat evolution [4], improved mechanical/structural properties such as long-
term strength development [5], enhanced durability [6-8] and reduced autogenous shrinkage [9]. However, the
use of SCMs often causes longer setting times [10], lower early strength development [5] and an increase in
drying shrinkage [9,11].
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Several methodologies have been studied to overcome the drawbacks and improve the efficiency of OPC
and SCMs in cementitious systems which include three main methods: thermal, mechanical, and chemical. The
heat treatment i.e. thermal activation can be divided into calcination [12-14] and elevated temperature curing
[15]. The former has been found highly contingent on limiting factors including the reactivity of the amorphous
phases and also the decrease of specific surface area and soluble fraction and the increase of crystalline
fraction. The latter often causes lower strength development in cementitious materials incorporating SCMs at
later ages [16,17].
Mechanical methods have been extensively utilised to enhance the pozzolanic activity of some types of
SCMs by grinding them into ultrafine powders for a prolonged period of time. This decreases the particle size
distribution and increases the dissolution rate of pozzolans, which accelerates the pozzolanic reaction rate and
consequently the strength development of concrete containing SCMs. However, controversial results are also
obtained regarding the correlation between the fixed free portlandite (CH) and the pozzolans’ surface area as
well as insignificant ultimate strength improvement [16-19]. Moreover, the more fine the particles, the more
chance of aggregation and agglomeration due to the interaction forces between particles inside the matrix.
The utilization of chemical accelerators (like CaCl2) to accelerate the early-age cement hydration has been
investigated. The chloride ions, however, adversely interfere with various hydration products and could also
cause depassivation of steel in reinforced concrete triggering corrosion and cracking of concrete [20]. Other
types of chemicals have also been identified that have shortcomings for long-term strength and durability of
cement-based composites [21,22]. Surface treatment of GGBS with chemical activator(s) [23] changes the
properties of their surface layer, which accelerates the rate of pozzolanic reactions, enhances strength
development rate, and increases the ultimate strength of cement-based composites. Nevertheless, some of
the most effective chemicals, such as caustic alkalis are not cost effective, user/eco-friendly or are not practically
feasible [24].
Furthermore, concretes subjected to high temperature curing at early ages attain higher early-age
compressive and splitting tensile strengths but significantly lower long-term strengths and elastic modulus
than those subjected to normal temperatures [25]. Whilst the addition of heterogenous nucleation sites (with
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added synthetic C-S-H particles or limestone) were also found to be effective on cement hydration acceleration
[26], this approach is still very expensive and practically limited.
Power Ultrasound has been used over a wide range of applications in materials science, from surface
cleaning and degassing, to particle dispersion and the production of nanostructures. Although some of these
applications have been investigated extensively, others, such as the use of PUS to control the properties and
performance of cementitious materials and enhancing the properties of SCMs incorporating composites are
yet to be reviewed and hold new, exciting possibilities. Several ultrasound techniques have been used to
characterise the setting and hardening processes of cement pastes, mortar and concrete, providing an overall
evaluation of mechanical strength, porosity, permeability and durability of cementitious composites [27]. A few
studies have focused on the effect of power ultrasound on the performance of early age hydration reactions
in cementitious matrices as well as composites incorporating SCMs. In this paper, a review of the literature on
the effects of PUS on the early age hydration kinetics of PC and binary blends, together with some underlying
mechanisms involved is presented. The future for applications of PUS in cement-based materials will also be
considered.
2. Ultrasonication
2.1. Background
The first reports of the chemical and biological effects of ultrasound were published in the early 20th century
[28-30]. However, it took many years for industry to adopt ultrasound as a more general energy source to drive
a range of chemical and processing operations. In 1972, Neppiras reviewed the main applications of power
ultrasound (PUS) in industry; which at that time was referred to as macrosonics [31]. The major applications lay in
cleaning, plastic and metal welding, wire and tube-drawing, ultrasonic machining, teeth descaling and the
extraction of chemicals from plants. He also listed some “minor applications” which have since become rather
more important. These included shaking and sieving [32], electrolytic processes [33], crystallization [34],
emulsification [35], dispersion [36], depolymerisation [37], degassing, the production of aerosols, drying,
defoaming and sterilization [38].
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The various strands of the applications of power ultrasound in the chemistry and material processing fields
were later to be brought together under the umbrella title of sonochemistry. The first ever international
conference on sonochemistry was held at Warwick University in the UK in April 1986 and sonochemistry was
further established as a subject in its own right with the publication of two major reviews [39,40].
2.2. Conventional power ultrasound
Conventional power ultrasound (PUS) is used in the frequency range between 20 kHz and 100 kHz (Fig. 1)
and is able to generate acoustic cavitation in a liquid and cavitation is the driving force for sonochemical
reactions. PUS is generally at a lower frequency range than that used for diagnostic ultrasound which is in the
MHz range.
The most common way of generating ultrasound is by exposing a piezoelectric ceramic transducer to a high
frequency alternating electric current. Under the influence of this electrical field the piezoelectric material
expands and contracts producing a high frequency mechanical vibration. This vibrational motion can be
transferred into and through any liquid medium, inducing cavitation and associated physical and chemicals
effects [41-43].
100 101 102 103 104 105 106 107
Frequency (Hz)
Fig. 1: Illustration of frequency spectrum from infrasound to ultrasound
2.3. Acoustic cavitation phenomena and cement-based materials
The chemical and physical effects of PUS in a liquid medium have been universally acknowledged to be the
consequence of acoustic cavitation. This is the formation, growth, and collapse of gaseous microbubbles in the
liquid phase (Fig. 2). Ultrasound is transmitted through a material in the same way as any sound wave via a
Infrasound Sound Ultrasound
Humanhearing
16Hz16kHz
PowerUltrasound
20kHz100kHz
Cleaning,Welding,Dispersion,
Degassing,Sonochemistry
Extendedrange
100kHz2MHz
Medical&destruction
Highfrequency
2MHz200MHz
Medicaldiagnostic
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series of compression and rarefaction cycles. During rarefaction, provided that the negative pressure is strong
enough to overcome the intermolecular forces binding the fluid, the fluid is literally torn apart producing tiny
cavities (microbubbles) throughout the medium. In the succeeding compression cycle if cavities were enclosing
a vacuum, they would collapse almost instantaneously. However, during cavity formation a small amount of
gas or vapour is drawn in from the surrounding liquid. As a result, the succeeding compression cycle may not
totally collapse the bubbles and so they will grow slightly larger in the next rarefaction cycle with a further
intake of gas and vapour. The process is known as rectified diffusion. The bubble will not grow indefinitely,
there will be an equilibrium size for any bubble in an acoustic field (this depends on frequency). Some bubbles
will continue to resonate in this stable state but many will become unstable and collapse, generating
microspots of extreme conditions of temperature and pressure. Based on the theory which has been put
forward to explain the energy release involved with cavitation, each cavitation bubble acts as a localised
microreactor which generates instantaneous temperatures and pressures on collapse of several thousand
degrees and over one thousand atmospheres respectively [41]. This phenomenon has led to the most popular
and widely accepted theory regarding the explanation of the effects of cavitation collapse the “hot spot” theory
[44]. The implosion of cavitation bubbles results in the formation of “shock waves” (strong pressure waves) and
“jet streams” inducing a “microstreaming” effect, causing jets of liquid to be directed to the solid surface of
any material suspended in the liquid and resulting in particle size reduction, particle collisions and surface
activation/cleaning. The release of shock waves and the effect of microstreaming together may also cause
intensive shear forces inside the liquid medium [43]. It is these effects which make PUS attractive to the cement-
based materials industry. Here, the systems are heterogeneous and material hydration is important during the
transformation of a fluid suspension into a solid at room temperature with minimal bulk volume change.
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Fig. 2. Schematic illustration of the process of acoustic cavitation: the formation, growth and implosive collapse of bubbles in a liquid
irradiated with high intensity ultrasound. Reproduced courtesy of Xu et al. [45]
3. Mechanisms of Portland cement hydration
Many modelling and experimental works explain the phenomena occurring during cement clicker hydration
and that of blended systems. It is universally hypothesised that the Portland cement hydration in which
transformation of anhydrous to hydrate phases occurs is basically a dissolution-precipitation process [46]. It
has been found that due to the congruently charge balanced dissolution of all the anhydrous phases, crystal
structure would preclude the unrestricted dissolution of certain phases without others. So, during the hydration
progress, the potential hydration products would intrinsically have a higher stability than the anhydrous phases
[46-48].
The hydration of tricalcium silicate (C3S) referred to as alite, as the most important constituent of Portland
cement clinker (accounting for 50-70% by mass) has been extensively investigated. Since its reaction kinetics
mostly resemble those of Portland cement, alite is being considered to serve as a reliable model in studying
Portland cement hydration [49]. The principal product of alite hydration is calcium-silicate-hydrates (C-S-H), a
nearly amorphous phase, which primarily contributes to the strength and volume stability in cementitious
materials [50]. Classical theories of hydration indicated that the surface of cement grains begins to be covered
by nuclei of the C-S-H gel formed and grown within a few seconds after initially mixing with water. Remaining
stable only in the induction period (which occurs because the size and number of growing regions are small);
this impermeable metastable C-S-H phase has a greater solubility than C-S-H and a lower solubility than alite.
Other researchers found two types of C-S-H during the initial stages of hydration including low density C-S-H
and high density C-S-H [50,51] . However, according to the most leading theory known as the nucleation
theory, it has been postulated that the induction period is controlled by the changes in ion concentration in
the solution rather than the presence of inhibiting hydration layers formed on the surface of alite grains. Once
the alite grains become covered with hydration products, the rate of hydration becomes controlled by the rate
of diffusion through this layer and decreases slowly for weeks or months. The theory proposed that the
hydration of alite is mostly controlled by solution controlled dissolution/diffusion and nucleation with
densifying growth mechanisms (Table 1). According to the nucleation theory, the rate of hydration during the
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induction period is dominated by nucleation and growth of C-S-H formed at the early stage and this period
ends when the growth of C-S-H starts. During early stages of hydration, the primary hydrates precipitate on
the surface of alite, but not as a continuous membrane (Fig. 3) [46,51-54]
Table 1. Identified phenomena controlling early hydration kinetics, summarized from [52,54]
Mechanism Overall kinetic behaviour Reaction stage
Dissolution
dissolving alite grain and releasing ions into the pore
solution
Up to the end
of the induction
period
Diffusion
transport of solution components through the pore
volume of cement paste
Nucleation
initiator of precipitation of solids heterogeneously on
solid surface or homogenously in solution
Up to main
heat evolution
peak
Growth
surface attachment, incorporation of molecular units
into the structure of crystalline or amorphous solids
It has also been postulated that the nucleation/growth mechanism might be a continuous process, implying
that existing C-S-H nanostructures stimulate the formation and expansion of new products outward from the
original nucleation site [53]. Overall, it seems that crystallisation plays a significant role in cement-based
materials hydration, controlling early and long-term properties of cementitious composites.
Fig. 3. Schematic representation of alite grain hydration at early stages (a) an anhydrous alite grain (b) the alite grain surface subjected
to water with C-S-H formed, along with etch pits (dissolution voids) formation (c) finally stable nuclei of C-S-H and CH initiate growing,
Reprinted courtesy of Juilland et al. [55]
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4. Effect of PUS on crystallisation of inorganic materials
Power ultrasound has proved to be extremely useful in crystallisation processes. It serves a number of roles
in the initiation of seeding and subsequent crystal formation and growth. This may be due to cavitation bubbles
acting as nuclei for crystal growth or by the disruption of seeds/nuclei already present within the medium thus
increasing the number of nuclei present in the solution. These effects have been examined in cementitious
system by the addition of synthetic C-S-H [26] or nanomaterials [56]. The Insonation of gels formed from
sodium aluminate and sodium silicate leads to increases in the nucleation and crystallisation rates for the
formation of zeolites by up to 6-fold and 3-fold respectively at 85°C [57]. The zeolite formed in the ultrasonic
field shows reduced particle size and a narrower size distribution compared with those produced by
conventional methodology. It was suggested that the reduction in particle size was due to an increase in the
number of crystallisation nuclei and their dispersion by the acoustic field. The rate of nucleation was shown to
increase with increasing irradiation intensity and this was also accompanied by a reduction in particle size
[57,58].
One of the most relevant research findings relating to the effects of PUS on crystallisation involving
cementitious materials is found in the studies carried out on the precipitation of calcium carbonate by Nishida
[59]. He examined the influence of ultrasonic irradiation on the precipitation rate of a supersaturated solution
of calcium carbonate (CaCO3). He observed that PUS accelerated the precipitation of CaCO3. He identified
macrostreaming as a dominant factor of this phenomena rather than microstreaming which is generally known
as one of major physical effects of cavitation. In a newer study, Boels et al. [60] investigated the seeded
crystallisation of calcite affected by the PUS. The measurement of volumetric crystal growth rate of calcite seed
crystals showed that the ultrasonic irradiation considerably increased the crystallisation rate and surface area
available for crystal growth and also caused disruption of conglomerates of single crystals.
Other experiments were carried out on salts like Barium sulphate (BaSO4) [61,62] and Potassium sulphate
(K2SO4) [63]. Guo et al. [61,62] studied the effect of ultrasound on crystallisation and the homogeneous
nucleation of BaSO4 and concluded that the induction time significantly decreased with increasing PUS energy
due to the accelerated diffusion process. Likewise, the effect of ultrasound on primary nucleation of K2SO4
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investigated by Lyczko et al. [63] showed a significant reduction in induction time and accordingly the
nucleation mechanism enhancement. Promotion of the dissolution-precipitation of the aluminium hydroxide-
water system affected by the moderate sonication was documented by Enomoto et al. [64]. A study [65] of the
influence of PUS in controlling the supersaturation, nucleation and crystal growth during the acid–base reaction
crystallisation showed the effectiveness of mixing, deagglomeration, reduction of both the induction period
and metastable zone width of the crystallisation and also the modulation of the crystal size and size
distribution. Similarly, the potential of PUS on controlling the crystallisation process of a type of antibiotics
(roxithromycin) through the inducing accelerated nucleation, reduction of the induction time, suppressing
agglomeration and changing crystal habit were investigated by Gou et al. [66]
Overall, the studies completed on the effect of PUS on the precipitation of inorganic materials generally
suggest that ultrasonication provides enhanced dissolution-precipitation, and consequently more nucleation
sites and surface area for a more efficient growth of crystals. Therefore, this may be a promising approach for
promoting the crystallisation properties of hydration products in cementitious materials.
5. Influence of PUS on cementitious systems
5.1. Challenges in cement-based systems
It has been recognised that aggregation or agglomeration can be induced between particles due to the
interaction forces between particles of colloidal/suspension systems (including the electrical double layer, van
der Waals, Born, hydration and steric forces) [67]. During these processes, primary particles stick to each other,
and spontaneously form irregular particle clusters, flocs, or aggregates held together by these weak forces that
can be separated. So, large irregular agglomerates embedded in cement-based composites can significantly
reduce the effectiveness of clinker cement and SCMs to participate in hydration as well as the pozzolanic
reaction and consequently improve all those positive properties which pozzolans can bring to them. In terms
of microstructural chemical reactions, the presence of SCM agglomerates leads to the formation of a C-S-H
with a much higher calcium to silicate (Ca/Si) molar ratio than usual in cementitious composites [68,69].
Generally, in cement chemistry and concrete technology, there are several challenges associated with hydration
of Portland cement and SCMs particles which might be approached by PUS application:
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Aggregation/agglomeration of cementitious materials; controlling packing density and hydration rate.
Pore structure of hardened cement-based materials which significantly affects the mechanical properties
and durability [70].
Penetration/diffusion (dissolution) of anhydrous phases in the fluid suspension of cementitious materials
during the hydration process occurs at the rapid slow down in reaction stage at the beginning of hydration
leading to a period of slow reaction known as induction time and continues through the growth process
after the acceleration period; controlling early age and long term properties of cementitious materials
[46,50].
Hydration rate after acceleration period (growth of hydration products) appears to be even slower
compared to crystalline hydrates, most probably due to the lack of available surface area and space for
hydration; controlling the long-term properties of cementitious materials [46].
Hydration products can act as deposit/cover on the cement/SCMs particles and hinder further reactions [46].
Complex hydration kinetics; this appears to make each of the phases hydrate at a rate different from the
others and are also affected in presence of each other [46].
5.2. Postulated mechanisms concerning the phenomenon
It is thought that the most promising effects of PUS will relate to the homogenising and dispersion of
cementitious particles through a colloidal cement system, leading to the deagglomeration of particle clusters . This
will enhance the effectiveness of SCMs in the secondary hydration reactions. The intensity of cavitational effects
which depends on the size and type of material presented in the medium, can lead to mechanical disaggregation
and dispersion of loosely held clusters, the removal of surface coatings by abrasion, and enhance mass transfer to
the surface.
Power ultrasound might also be influential on the crystallisation process of different hydration phases in a
cementitious system. Furthermore, exfoliation of Portland cement and the anhydrous and hydrated phases of
SCMs through the generation of surface damages triggered by the effects of cavitation bubble collapse might
control the rate of hydration products and ultimately the properties of cementitious composites. The key
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mechanical effects of PUS offer an opportunity to overcome the types of challenges associated with
cementitious materials outlined in the Table 2.
In recent years, the application of ultrasonic treatment to disperse different types of powder and
nanoparticles in an aqueous and non-aqueous solution as well as high viscosity polymer solution has been
explored [36]. Despite the limited efforts to characterise the ultrasonic dispersion of densified silica fume and
apply it to cementitious systems (as well as one study carried out concerning the characterisation of the PUS
effect on hydration and fluidity of cement/slag blended suspension), still relatively little is known about the
effects of PUS on Portland cement and SCMs incorporated in cementitious systems. This review will focus on
research carried out on the capability of PUS to improve the properties of cementitious materials. First, a
discussion will be made on the potential beneficial effects of cavitation on cementitious materials, followed by
some comments on the limited number of results published related to practical applications of PUS to Portland
cement and SCMs.
Table 2. Proposed physical/mechanical effects of ultrasound cavitation tailored for cementitious materials
Systems Postulated/investigated effects of PUS Expected results in cementitious materials
Homogenous (in absence of pre-existing crystal; liquid bulk)
Enhanced mass and heat transfer from and
onto the surface due to microstreaming
[34,43,71]
Intensification/accelerated transportation of anhydrous cementitious
materials and hydration phases/products
Degassing of suspension [43] Highly critical to pore structure of cement-based materials systems
mainly air entrapped voids and air entrained voids (generated by air
entrained agents) controlling both mechanical and transport
properties
Enhancing crystallization/precipitation
(technically known as “sonocrystallisation”)
[34]
Reduction of the induction time
Enhancing homogenous nucleation and growth of stable hydration
products
Reduction of metastable zone width
Heterogeneous (in
presence of wall or
Breaking up/erosion of the surface structure
(surface damages) due to shock waves
and/or jet streams [34,43,72]
Modifying the morphology of crystals/hydration products
Allow penetration of phases entered in hydration reaction by affecting
etch pits in the surface
Release of hydration products from cementitious materials surfaces
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Allow penetration of particles already covered with hydration products
by removal/release of formed hydration precipitates away
Degradation of large solid particles due to
shear forces induced by shock waves and
microstreaming [34,41,43,72,73]
Reduction of particle size and agglomeration
Increase surface area of cement particles and SCMs
Homogenising and Dispersion of anhydrous cementitious particles and
hydrated phases
High velocity collisions and accelerated
motion of particles [34,43,74]
More effective mass transfer, consequently intensification of those
effects occur in homogenous systems
Enhancing crystallization/precipitation [34] Reduction of the induction time
Enhancing heterogeneous nucleation and growth of stable hydration
products
Reduction of metastable zone width
5.3. Parameters influencing the cavitation phenomena in cement-based materials
It has been found that some external parameters have a great influence on cavitation as the most important
phenomenon to induce sonochemical effects. Understanding these factors helps to provide condition in which
the sonochemical effects are optimised. Some of the most influential factors affecting the sonochemical effects
with regards to cement-based system are reviewed in Table 3.
Table 3. Review of some factors influencing the cavitation phenomena in cement-based materials
Parameters Sonochemistry perspective Cementitious materials perspective
Frequency
At higher frequencies, the rarefaction/compression cycle
becomes shorter than the time required to permit the molecules
to be pulled apart, making the cavitation difficult or impossible
to achieve. Moreover, for a determined power level, the
threshold in changing physical effects might be reached and so
no further changes could be observed as a result of sonication.
Frequencies usually opted for typical crystallisation fall in the
range between 15 and 40 kHz which its variable was found to
have the same influence on nucleation and growth [28]
initiation of acoustic cavitation using combined low
and high-frequency which might have substantial
effects on the hydration crystallisation of
cementitious materials.
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Intensity (Power Input)
Whilst an increase in ultrasound intensity will provide an
increase in the sonochemical effects, the barrier effect of larger
and longer lived bubble formation to the transfer of acoustic
energy, possibility of transducer material fracture and great loss
in efficiency of power transfer from the source as a result of
decoupling phenomena need to be considered [28,34].
An increase in ultrasound power intensity is
expected to cause heavier flow, enhanced mass
transfer in the media and the driving force of
crystallisation, leading to the higher the
crystallisation rate.
Temperature
Apart from a decrease in viscosity and surface tension, any
increase in temperature will raise the vapour pressure of a
medium and therefore will cause an easier cavitation with a less
violent collapse. However, at higher temperatures, a large
number of cavitation bubbles are generated because of the
approaching solvent boiling point. Acting as a barrier to sound
waves transmission, these will cushion the ultrasonic energy
from the source
In the cementitious systems, the intensive increase
and decrease in temperature will markedly
accelerate and slow down the hydration rates,
leading to a relatively fast and slow initial setting
times, respectively, and adversely affected
microstructure and hardening properties.
Therefore, practical and technical considerations
need to be taken when applying the PUS.
Gas bubbles
dissolved gas and small gas bubbles in a fluid act as nuclei for
cavitation, promoting cavitation and are then removed.
Degassing and defoaming characterisation of PUS
is expected to be highly critical as the products of
the hydration process consist of a pore system
governing the properties of cement-based
systems. The effect of PUS on the stability of
entrained air bubbles has also needs to be
understood.
6. Studies on the influence of PUS on cementitious materials
6.1. Portland cement
An experimental study performed by Rößler [75] and Peters [76] represents the first officially published
experiment carried out on the influence of PUS on initial setting, hardening and hydration characterisation of
Portland cement (CEM I 42.4R). In order to guarantee a uniformly continuous sonication until providing the
required specific energy input, a flow-through cell sonication set-up equipped with a laboratory ultrasonic horn
was utilised (UIP 1000hd, Hielscher, Germany). The set-up provided a constant frequency of 20 kHz and
different amplitudes adjustable by a booster.
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In the first part of the study, the research aimed to highlight the effect of PUS on setting and hardening of
a cement suspension (with a w/c ratio of 0.37). The practical limitations regarding the use of PUS in concrete
production, namely the initial setting time, temperature rise due to the ultrasound application and the minimal
period of PUS treatment were considered. So, the optimal PUS parameters emerged to be 43µm (ultrasonic
horn with front face diameter of 0.9 cm2) and 75 J/mL for the PUS amplitude and specific energy input,
respectively. The results of initial setting time demonstrated that ultrasound treatment shifts the initial setting
time of cement paste to an earlier time. Moreover, the influence of PUS on cement hydration was evaluated by
means of analysing the isothermal differential conduction calorimetry and the non-destructive ultrasonic P-
wave velocity and microstructural study of cement suspension as well as the compressive strength
development of mortars [76].
The results of isothermal heat release demonstrated that PUS accelerates the heat release rate limited to
the hydration acceleration period, whereas the total heat release was unaffected by the PUS treatment (Fig. 4).
Relying on the correlation between the P-wave velocity test results and the strength development of
cementitious materials; it was deduced that an improved strength development of sonicated cement
suspension limited to only the first 16 hours was most probably due to the accelerated cement hydration [76].
Fig. 4. Isothermal heat release rate and total heat of reference and sonicated cement suspension (w/c: 0.37 with 0.1 wt% SP)
during first 72 hours of hydration, Reprinted courtesy of Peters [76]
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The enhanced compressive strength of mortars during the 24 hours of hydration as well as microstructure
analysis of cement suspension (Fig. 5) underscored the PUS effectiveness on accelerating the cement hydration,
confirming the results obtained from the hydration heat release and setting time examination [76].
(a) 3 hours and 30 minutes hydration
(b) 5 hours hydration
(c) 6 hours and 30 minutes hydration
Fig. 5. SEM micrographs of reference (left) and PUS treated (right) cement suspension microstructure (w/c: 0.37 with 0.1 wt% SP),
Reprinted courtesy of Peters [76]
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Furthermore, in-depth investigations were performed on the characterisation of model substance hydration
(synthesised alite) in order to evaluate primary (homogenous) and heterogeneous crystallisation and
precipitation (nucleation and growth) of C-S-H phases. The former examination was conducted on clear Ca-Si
solution and the latter was performed on diluted alite suspension. The results of electrical conductivity
measurement and determination of Ca and Si ion concentration by the ICP-OES (Inductively Coupled Plasma-
Optical Emission Spectroscopy) showed that PUS accelerates the kinetics of alite hydration but does not alter
the reaction path. It was hypothesised that the mechanism of hydration acceleration facilitated by the
ultrasound introduction would be dominated by the precipitation enhancement of very early C-S-H phases.
Besides, it was postulated that the shock waves induced by the cavitation phenomenon is mostly responsible
for increasing the particle collisions, leading to localised erosion effects and the removal of initial C-S-H
precipitates away from alite surfaces. Consequently, not only do the alite grain surfaces remain unwrapped
with C-S-H products, but also detached C-S-H precipitates provide additional sites for triggering more C-S-H
phases growth. It was proposed that other PUS effects like hot spot and jet streams were accounted for a minor
significance [76].
The positive influence of PUS on fluidity and the generation of homogenous fresh cement paste was also
confirmed by Peters by performing mini slump flow spreading time and V-funnel flow time examinations. Further
observation was carried out to briefly characterise the hydration process of GGBS under the influence of PUS.
Acceleration of GGBS blended cement hydration was deduced based on the initial setting time, compressive
strength evaluation of mortars and isothermal heat release rate examination. Nevertheless, the isothermal heat
calorimetry test on pure GGBS suspension incorporating CH showed that PUS application only slightly accelerates
GGBS [76].
Recently, Resonance Acoustic mixing (RAM) technology that combines the principals of reciprocating movement
agitator mixing and bubble acoustic micro-streaming mixing was employed by Vandenberg and Wille [77] to
evaluate its efficiency for mixing Ultra-high performance mortar. The results presented reduced flow and workability
properties while improved mechanical properties in specimens mixed with RAM. Although an increase in hydration
kinetics and change microstructural development of mixtures compared to a standard table paddle mixer were
concluded, the study was not engaged to perform microstructural study and quantitative reasoning.
18
Overall, although some test results confirm the positive influence of PUS on cement hydration, some other
examination results are not reflective of an entirely significant effect of hydration enhancement. More research,
especially quantification of hydration is needed to gain a fundamental understanding about the mechanisms
in which PUS affects cementitious systems.
6.2 SCMs
The mechanical effects of cavitation are already being used in generation of nanostructures and
nanoparticles [36]. These physical effects also have been postulated to provide a reduction in the size of
densified or agglomerated particles by applying the forces of cavitation, breaking of agglomerates and
aggregates. In this section, the studies performed to characterise the effects of PUS on SCMs have been
overviewed.
It has been reported that silica fume as a SCM will significantly reduce both the interfacial transition zone
between the aggregates and bulk cement paste and the deposition of a portlandite rim, resulting in
improvement in fresh properties, mechanical strength and durability properties in cement-based materials [78-
81]. However, the continuous interaction of individual spheres of silica fume particles promotes the formation
of agglomerates. As in most silica-fume-bearing cementitious composites, the silica fume is introduced in its
densified (agglomerated) form, and the agglomerates are likely to remain at least partly undispersed especially
in normal concrete mixing [69,82]. This inhibits the complete transformation of silica rich gel into different
morphological types of C-S-H through the pozzolanic reaction and consequently leaves a large number of
unhydrated or partly reacted remnants of silica fume particles in the hardened cement paste [83]. As for all
SCMs, the un-reacted silica fume particles might reduce the effectiveness of pozzolanic reactions and adversely
affect the positive contribution of them for improving mechanical and durability properties of cement-based
composites [84].
Some studies (Table 4) have been carried out to deal with the dispersion of silica fume by utilizing the PUS
approach, as an alternative to enhance its pozzolanic activity. Overall, it has been inferred that the sonication
process generally shifts the particle size distribution towards smaller particle sizes, comparatively raising the
volume content of sub-micrometric particles in the PUS treated silica fume suspension.
19
Gapinski and Scanlon [82] recommended a sonication process to break and disperse the bonded silica fume
agglomerates.
20
Table 4: Summary of PUS Studies on Silica fume
Author,
Year
Testing Materials Sonication approach Test equipment & Conditions Characterisation Approach
Gapinski
& Scanlon;
2006 [82]
Densified silica fume (as received sample) Built in 600 watt ultrasound 0.010% sodium pyro-phosphate solution as the surfactant custom-built laser scattering particle size analyser with and a
Martinez-
Velandia
et al.; 2008
[85]
3 types of densified silica fume with different
granulometric distribution
1 type No-densifeid silica fume
1 type of Milled densified silica fume
Sonicator S-3000, Misonix
Max. 600 watts; 20kHz
Different sonication power: 141 (2.26 watt/g)
and 168 (2.69 watt/g) (corresponding to 80
and 100 % of the maximum power of
sonication probe)
Different sonication time: 2, 4, 6, 8, 10, 12,
14, 16, 18, and 20 minutes.
600 ml precipitate beaker suspended in water
Different SF/water ratio
Temperature: 20-35 °C
Granulometric distribution curves analysis by calculation of mean
particle diameters, 10, 50, and 90% percentiles and the volume of
particles with a diameter lower than 1 µm (Submicrometric particles)
Laser diffraction granulometric (LDG) analysis (Mastersizer 2000,
Malvern Instruments);
Specific surface area (SSA) measurement by BET method (Tristar 3000,
Micromeritics)
Martinez-
Velandia
et al.; 2011
[84]
1 type of densified silica fume (supplied by
Ferroatlantica, Sabon, Spain)
Sonicated silica fume by the procedure stated
on the previous work [85]
Cement: CEM I-52.5R
Superplasticizer Melment 240 (Bettor S.L)
Sonicator S-3000, Misonix
Max. 600 watts; 20kHz
Different sonication power, watts (watt/g):
60 (0.96), 81 (1.30), 111 (1.78), and 141 (2.26)
Different sonication time: 5, 10, 15, 20, 25
minutes.
Preparation of cement mortars according to EN 196-1:1996
procedure :
5, 10 and 15% cement replacement by silica fume; Water/cm:
0.35; Curing time: 7 and 28 days
600 ml precipitate beakers suspended in water (228.4 ml)
Different SF/water ratio
Temperature: 20-35 °C
Mortars was ground in acetone and dried for 30 min at 60 °C
Laser diffraction granulometric (LDG) analysis
SEM micrographs (JEOL JSM 6300)
Calculation of the strength activity index (SAI)
Study of fixation of hydrated lime by:
TGA/DTG analysis (TGA Mettler-Toledo 850 thermobalance, 35-600 °C
at 10 °C/min)
21
Rodriguez
et al.; 2012
[68]
3 commercial densified silica fume
2 non-densified silica fume with different
particle size distribution
Cement paste: CEM-I 52.5R, silica fume
sonicated suspension, Cement replacement
10%
Sonicator S-3000, Misonix
Max. 600 watts;
Output frequency: 20kHz
Sonication time: 10 minutes
Aqueous dispersion: 5 g of SF and 20 g of water in a
precipitate beaker of 50ml
water/binder ratio: 0.4
Temperature kept steady at maximum 40 °C using an external
cooling bath
PUS treated particles characterization by SEM micrographs, XRD
analysis, laser diffraction analysis (DLA), zeta potential measurement
and TEM micrographs,
Microstructural characterization of cement paste samples affected by
sonication treatment by TGA/DTG and SEM/EDS analyses
Rodriguez
et al.; 2012
[86]
1 commercial densified silica fume (supplied
by Elkem Silicon Materials, 940D)
Cement: CEM I-52.5R
Sonicator S-3000, Misonix
Max. 600 watts;
Output frequency: 20kHz
Sonication time: 15 minutes
Aqueous dispersion: solid to liquid ratio of 0.20
Temperature kept steady at maximum 40 °C using an external
cooling bath
40 mm Cubic samples of mortar containing blended cements
with 5, 10 and 20% cement replacement by densified and
sonicated silica fume admixtures
Water to binder ratio: 0.3 / Superplasticizer (Glenium ACE31,
BASF)
PUS treated particles characterization by TEM micrographs
Paste characterization on blended cement pastes with w/b:0.5 and 10
wt% substitution of silica fume for cement by XRD, TGA/DTG and
MAS-NMR analysis
Compressive strength development test (7, 28 and 60 days of curing)
Pore size distribution of mortar specimens (28 days) by MIP
(AutoPore IV 9500, MIC)
Microstructural characterization by SEM/EDS analyses
Hashem et
al.; 2015
[87]
Commercial ultra-fine silica fume with particle
size ranging from 625 nm to 48 nm
Concrete mixture: 65% coarse aggregates and
35% fine aggregate
Polycarboxylate admixture (Glenium C315
SCC)
Ultrasonication Bath (FALC Instruments) 150
watts, Frequencies 40 and 59 kHz
Power set on 70 watts (according to 50%
power) and 135 watts (100% power)
Frequency set to 59 kHz
Different sonication time: 7, 15, 60, 150
minutes.
600 ml precipitate beaker
Different liquid/powder ratio: 1.5, 2.4, 6, 10 and 12
Mechanical homogenizer (rotor-stator) with working speeds of
9500, 13500 and 24000 rpm
Temperature kept steady at maximum 40 °C using built-in
heater
Concrete mixtures, by 1, 5 and 10% untreated silica fume and
1% treated silica fume
Particle size analysis, calculating mean. Range, D50, D80, D20 and sub
micrometre sizes.
TEM micrographs of treated particles (JEOL JEM-1230)
Zeta potential measurement (Zeta Sizer 2000, Malvern Instruments)
Compressive strength measurement of concrete
22
Martinez-Velandia et al. [85] studied the granulometric properties and deagglomeration of the different
types of silica fume affected by PUS. The study confirmed the effectiveness of the PUS treatment on the
granulometric distribution [85].
In order to investigate the effectiveness of sonicated silica fume particles on the pozzolanic reactivity in
cementitious system, Martinez-Velandia et al. [84] Introduced their optimised homogenous suspensions of
silica fume treated by the means of the sonication process [85] to cement mortars. Sonicated silica fume
incorporated mortars showed an increase of 10 to 15% in the compressive strength especially for longer
sonication times and higher sonication power levels. The thermogravimetric study also confirmed the activation
of the pozzolanic reactions (fixations of free portlandite) [84].
Rodriguez et al. [68] found that sonication treatment introduced to densified silica fume contributes to an
increase in the volume of particles of smaller sizes and also the enhancement of its reactivity by a de-
agglomeration mechanism, improving dispersion.
The effect of sonicated densified silica fume on the hydration products, performance and pore structures
of blended cement based pastes was the topic for another study carried out by Rodriguez et al. [86]. The results
of the compressive strength development study showed that applying the sonicated silica fume promotes
higher mechanical strength in cement mortar specimens so that a desirable mechanical performance can be
achieved using a smaller content of SCMs. Moreover, the results of XRD, TGA/DTG analysis indicated that PUS
treated silica fume shows higher pozzolanic reactivity, associated with higher consumption of portlandite
through the hydration process compared with the densified silica fume admixture. Based on the results of
MAS-NMR spectroscopy analysis, this causes the formation of an aluminium-rich C-S-H with a structure of
longer chain length and lower Ca/Si ratio which is a more stable binding phase. The pore size distribution study
of cement mortar specimens also showed that the incorporation of sonicated silica fume induces a significant
decrease by more than 20% in the volume of large pores (with diameters larger than 10 µm) as well as a
reduction in total porosity.
23
Hashem et al. [87] studied the sonication process parameters for the preparation of nanoparticles of silica
fume and used the optimum sample to investigate the pozzolanic reactivity by introducing it to a concrete
mixture. Based on the results obtained, the optimum sub-nanometric particle distributions of ultrasound
treated silica fume correspond to the experimental condition: sonication power/frequency/process time: 135
watts/ 40 kHz/ 60 min; homogenizer speed of 24000 rpm and liquid/water ratio of 6. Introducing this optimised
sample into cementitious system by 1% cement replacement; the sonicated silica fume incorporated concrete
showed 10 and 20% enhancement in compressive strength compared to the reference silica fume and control
mixtures, respectively. Sharobim et al. [88] found that sonicated nano-silica enhances compressive strength of
concrete and the microstructure of the cement matrix. As it is evident, all the reviewed studies have investigated
the dispersion improvement of silica fume and nano-silica in the cementitious matrix whilst failing to address
the kinetics of cement-based materials hydration under the effect of ultrasound.
Askarinejad et al. [89] characterised the natural pozzolans’ nanostructures affected by introducing the PUS
irradiation to bulk natural pozzolans by SEM and XRD as well as studying the pozzolanic activity by TG/DTA
analysis and mortar’s compressive strength index. Similar to the results obtained from the studies carried out
on the effect of PUS on densified silica fume, the results demonstrated that the pozzolanic reactivity of natural
pozzolans was enhanced by applying PUS in optimised conditions.
Overall, It is evident that ultrasonic treatment has been shown to be a favourable alternative in enhancing
the efficiency of densified silica fume and natural pozzolans in the following forms: improved dispersion of
agglomerates (especially sub-micrometre particles leading to a much wider particle distribution and enhancing
the pozzolanic activity associated with a lower amount of unreacted particles), and comparative mechanical
performance using a lower dosage of SCMs replacing part of Portland cement. However, very little is known
about the PUS influences on SCMs and extensive specific research is needed to clarify the mechanisms in which
PUS influences Portland cement and SCMs hydration.
7. Conclusion and future perspectives
This review has surveyed existing research in the field of PUS applications in cementitious materials. In doing
so, some specific research areas have been identified which are needed to make progress in both a
24
fundamental understanding of such applications and to push forward the development and uses of ultrasound
techniques for cement-based composites. Amongst these the authors suggest the following lines of
investigation:
The effect of PUS on Portland cement hydration is not yet fully understood. More studies need to be
conducted to confirm the effects of cavitation on cementitious materials, and at the same time clarify its
mechanisms. The only undertaken study has focused on limited characterisation of alite hydration which is
only considered as a binary system of Ca and Si ions in cement hydration. However, the effect of exposing
PUS to complex systems of ternary compositions of CaO-SiO2-Al2O3 need to be thoroughly investigated.
Overall, the authors believe that it is now time to expand the horizon of ultrasound-assisted crystallisation
studies known as “sonocrystallisation” to cement hydration products. The aim should be to develop advanced
theories regarding the homogenous and heterogeneous nucleation and growth of cement hydration affected
by ultrasound irradiation.
De-agglomeration and gaining an enhanced particle size distribution has been the primary focus of nearly
all studies carried out in the use of PUS to promote SCMs properties. In addition, microstructural studies on
cementitious composites have failed to reveal an in-depth analysis of the hydration as well as mechanical
and durability properties characterisation. Therefore, it is necessary to study the kinetics and mechanism of
PUS affected cementitious blended systems in which the hydraulic reaction of SCMs could lead to more
complex hydration phases in combination with cavitational effects. The first step in fulfilling this objective
may be to develop an analytical approach to qualify and quantify the reaction of SCMs independently of
the cement clinker phases. Then, the intermixing levels of hydration phase compositions in blended systems
(i.e. PC-silica fume, PC-slag, PC-PFA, PC-natural pozzolan) subjected to PUS should be investigated.
The fresh state properties of cementitious materials markedly dominate the practical aspects of their usage
in the field. In addition to the initial setting time, the characterisation of rheological parameters (i.e. yield
stress and viscosity) of sonicated cement-based systems need to be well established.
Expanding the practice of sonicated cement paste to concrete system should be pursued in future studies.
It would require the development and manufacturing of ultrasound equipment tailored for concrete, and
more notably, scaled up sonochemical processes.
25
The influence of the degassing (de-airing or de-foaming) effect of PUS especially in present of air-entrained
admixtures needs to be investigated.
Studies on the influence of PUS on the crystallisation of hydration products in the presence of
superplasticisers needs to be performed.
The study regarding the influence of high frequency as well as combined low and high frequency ultrasound
exposure on sonocrystallisation of cementitious materials hydration needs to be carried out.
The generated heat due to the cavitation phenomenon during the PUS practice which could adversely affect
initial setting needs to be addressed.
It is hoped that further research progress in this field will drive the commercial utilisation of PUS in the
construction industry.
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pozzolan, Ultrasonics Sonochemistry 19 (2012) 119-124.
... When CO2 gases are supplied under ultrasonic vibration, they firstly react with Ca(OH)2 which is precipitated from the initial hydration to produce flocculent CaCO3 crystals. The solid surfaces suspended in the liquid are damaged dramatically due to the "cavitation effect" of the ultrasonic wave [38]. When an ultrasonic wave radiates and spreads throughout the paste, it will produce numerous small bubbles in the paste, which will break continuously. ...
... When CO 2 gases are supplied under ultrasonic vibration, they firstly react with Ca(OH) 2 which is precipitated from the initial hydration to produce flocculent CaCO 3 crystals. The solid surfaces suspended in the liquid are damaged dramatically due to the "cavitation effect" of the ultrasonic wave [38]. When an ultrasonic wave radiates and spreads throughout the paste, it will produce numerous small bubbles in the paste, which will break continuously. ...
... When CO2 gases are supplied under ultra Ca(OH)2 which is precipitated from the initial hy crystals. The solid surfaces suspended in the liquid "cavitation effect" of the ultrasonic wave [38]. W spreads throughout the paste, it will produce nu which will break continuously. ...
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To realize high-efficiency CO2 absorption by fresh cement paste, ultrasonic vibration technology is introduced into the CO2 absorption test device used in this study. Influences of ultrasonic frequency on the CO2 absorption rate (CO2 AR) and the ultimate absorption amount of fresh cement paste are analyzed. Furthermore, the influencing laws of the CO2 absorption amount (CO2 AA) on the fluidity, pore distribution, and mechanical properties of cement paste under ultrasonic vibrating agitation are analyzed by measuring the variations of the CO2 AA of cement paste. Results demonstrate that ultrasonic vibrating agitation not only can increase the CO2 AR and ultimate absorption amount of fresh cement paste, but also can optimize the internal pore structure of materials and compressive strength of cement-based materials.
... This physical effect reduces the size of solid particles or agglomerates through the power of cavitation, which destroys agglomerates and aggregates. Ultrasonic activation has been shown to increase pozzolanic efficiency, increase the dispersion of agglomerates (especially submicrometer particles to cause a much wider distribution of particles), and increase pozzolanic activity through a lower number of unreacted particles (Ganjian et al., 2018). Ultrasonic activation can distribute particles more homogeneously, increase flow capability, and reduce film thickness, thereby supporting penetration of the sealer into homogeneous dentinal tubules (Duque et al., 2018) (Vivan et al., 2017). ...
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Objective: To compare the penetration of premixed calcium silicate-based sealers (CSBS) and premixed calcium silicate pozzolan-based sealers (CSPBS) with and without ultrasonic activation into dentinal tubules. Material and Methods: Thirty-two samples of mandibular premolar teeth were divided into four groups: Group I: CSBS without ultrasonic activation; Group II: CSBS with ultrasonic activation; Group III: CSPBS without ultrasonic activation; Group IV: CSPBS with ultrasonic activation. Activation was done using an ultrasonic device (P-5 Newtron XS; Satelec, Mount Laurel, NJ) for 3 seconds. Sealer penetration was observed using a confocal laser scanning microscope (CLSM, Olympus Corporation, Tokyo, Japan), and the maximum penetration sealer was measured from the root canal wall to the point of maximum penetration using an ImageJ software (NIH, Bethesda, MD, USA) measuring instrument. Results: There was a significant difference in dentinal tubules' penetration between CSBS and CSPBS with and without ultrasonic activation (p = 0.009). The mean penetration of CSBS was 638.13 µm, CSBS with ultrasonic activation was 651.50 µm, CSPBS was 580.13 µm, and CSPBS with ultrasonic activation was 914.25 µm. Conclusion: CSPBS with ultrasonic activation showed the best penetration into dentinal tubules. Keywords: Dentine tubule penetration, calcium silicate pozzolan-based sealer, calcium silicate-based sealer, ultrasonic.
... As the cavitation kicks in, splitting bubble clusters undergoing chaotic shape oscillations close to the aggregate, plus the induced acoustic microstreaming force push the surrounding liquid to penetrate inside the agglomerate reaching air pockets and grooves or capillaries. The oscillation of μB clusters as well as the incoming AW/SW near the agglomerate then excites the liquid inside, creating overpressure to nucleate more tiny vigorously oscillating microbubbles that generate large shear forces [54,55] leading to de-agglomeration and fragmentation of the oxide particles within the bulk liquid. These sequence of events as demonstrated in Fig. 10b is clearly evident with experimental observations made in Fig. 5 (a-f), which highlight the sono-capillary effect occurring on the surface of the aggregate. ...
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Ultrasonic de-agglomeration and dispersion of oxides is important for a range of applications. In particular, in liquid metal, this is one of the ways to produce metal-matrix composites reinforced with micron and nano sized particles. The associated mechanism through which the de-agglomeration occurs has, however, only been conceptualized theoretically and not yet been validated with experimental observations. In this paper, the influence of ultrasonic cavitation on SiO2 and MgO agglomerates (commonly found in lightweight alloys as reinforcements) with individual particle sizes ranging between 0.5 and 10 μm was observed for the first time in-situ using high-speed imaging. Owing to the opacity of liquid metals, a de-agglomeration imaging experiment was carried out in de-ionised water with sequences captured at frame rates up to 50 kfps. In-situ observations were further accompanied by synchronised acoustic measurements using an advanced calibrated cavitometer, to reveal the effect of pressure amplitude arising from oscillating microbubbles on oxide de-agglomeration. Results showed that ultrasound-induced microbubble clusters pulsating chaotically, were predominantly responsible for the breakage and dispersion of oxide agglomerates. Such oscillating cavitation clusters were seen to capture the floating agglomerates resulting in their immediate disintegration. De-agglomeration of oxides occurred from both the surface and within the bulk of the aggregate. Microbubble clusters oscillating with associated emission frequencies at the subharmonic, 1st harmonic and low order ultra-harmonics of the driving frequency were deemed responsible for the breakage of the agglomerates.
... High-frequency ultra-sonic dispersion can cause high-speed liquid jets (up to 1000 km/h) and create high pressure between liquid and mixture particles, colliding them into smaller particles [44,45]. Thus this technique could have a very positive effect on some mixtures, which contain Nano/micro fillers with very low specific surface areas (for example Nano-SiO 2 , TiO 2 , Al 2 O 3 , Fe 2 O 3 , carbon Nano-tubes, carbon Nanofibres, Nano clays, graphene oxide, and graphite oxide). ...
Article
h i g h l i g h t s High-frequency ultra-sonic dispersion decreases porosity of ultra-high performance concrete. High-frequency ultra-sonic dispersion smethod increases hydration process of Portland cement. High-frequency ultra-sonic dispersion can be applied with decent technology to prepare ultra-high performance concrete. High-frequency ultra-sonic dispersion can significantly speed up the hydration process of UHPC mix. a b s t r a c t This article is the continuous research on the successful attempt to utilize glass powder in ultra-high performance concrete. The previous study showed, that glass powder has a positive effect on the Portland cement hydration process, however, one problem was unable to overcome: about half the amount of unreacted clinker mineral remained in the composition, even when thermal treatment was applied. This research proposes a successful adaptation of the ultra-sonic dispersion method. The proposed method allowed to increase even further hydration process of the binder as well to develop a more favourable microstructure. Experiment research was investigated by XRD analysis, Chapelle, semi-adiabatic calorimetry, 29 Si MAS NMR, mercury intrusion porosimetry, and compressive strength test methods. Results revealed, that high-frequency ultra-sonic dispersion can significantly increase the hydration degree of binder and the compressive strength up to 16%.
... In the context of physical activation, power ultrasound has been Adapted from reference [31] with permission from Elsevier. applied to the acceleration of early-age alite reaction in PC and their applications to cementitious materials have been very recently reviewed [141]. This application is interesting for PCs but it could become more relevant for BCs. ...
Article
Belite cements, BCs, containing mainly belite, alite and calcium aluminates, are currently used as low heat cements. These binders produce high amounts of C–S–H gel and have very good durability properties which are reviewed. Additional advantages include: (i) lower limestone demand, with lower associated CO2 emissions; (ii) lower energy demand; (iii) lower kiln operating temperature, which means lowering CO2 and NOx emissions from fuel burning; and (iv) lower temperature increase at early hydration age. However, early-age strength developments are not competitive with those of Portland cements. Hence, to improve their early-age strength developments is a research priority known as activation. This enhancement can be attained by three compatible approaches: (i) chemical, (ii) physical; and (iii) admixture activations. The current research status for BCs activation is reviewed including: cost-effective element substitutions to stabilize high-temperature forms; fast cooling, milling and mild temperature hydration as physical activation; and the use of C–S–H seeds as admixture activation. After discussion of the resulting microstructures, a research outlook is exercised.
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The acceleration of very early age cement hydration by C-S-H seeding is getting attention from scholars and field applications because the enhanced early age features do not compromise later age performances. This acceleration could be beneficial for several low-CO2 cements as a general drawback is usually the low very early age mechanical strengths. However, the mechanistic understanding of this acceleration in commercial cements is not complete. Reported here is a contribution to this understanding from the study of the effects of C-S-H gel seeding in one Portland cement and two belite cements at two widely studied water–cement ratios, 0.50 and 0.40. Two commercially available C-S-H nano-seed-based admixtures, i.e., Master X-Seed 130 and Master X-Seed STE-53, were investigated. A multi-technique approach was adopted by employing calorimetry, thermal analysis, powder diffraction (data analysed by the Rietveld method), mercury intrusion porosimetry, and mechanical strength determination. For instance, the compressive strength at 1 day for the PC (w/c = 0.50) sample increased from 15 MPa for the unseeded mortar to 24 and 22 MPs for the mortars seeded with the XS130 and STE53, respectively. The evolution of the amorphous contents was determined by adding an internal standard before recording the powder patterns. In summary, alite and belite phase hydrations, from the crystalline phase content evolutions, are not significantly accelerated by C-S-H seedings at the studied ages of 1 and 28 d for these cements. Conversely, the hydration rates of tetracalcium alumino-ferrate and tricalcium aluminate were significantly enhanced. It is noted that the degrees of reaction of C4AF for the PC paste (w/c = 0.40) were 10, 30, and 40% at 1, 7, and 28 days. After C-S-H seeding, the values increased to 20, 45, and 60%, respectively. This resulted in larger ettringite contents at very early ages but not at 28 days. At 28 days of hydration, larger amounts of carbonate-containing AFm-type phases were determined. Finally, and importantly, the admixtures yielded larger amounts of amorphous components in the pastes at later hydration ages. This is justified, in part, by the higher content of amorphous iron siliceous hydrogarnet from the enhanced C4AF reactivity.
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The influence of the direct application of power ultrasound (PUS) at several frequencies and power densities to Portland cement (PC) pastes is investigated in detail. Two PC pastes at water-to-cement ratios of 0.50 and 0.80 were studied. The composition of the pore solution and hydrates after introducing PUS irradiation for various periods were examined using ICP-OES, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The results indicate for the first time that applied PUS used in this study, can disturb the early formation of ettringite whilst appreciably promoting the formation of amorphous aluminium hydroxide hydrate by considerably releasing the aluminium ions into the pore solution. Moreover, PUS can increase carbonates by intensifying the carbonation in the PC systems particularly the system with higher water content. The present research concludes that ultrasound could be a promising technique to enhance ternesite hydration in ternesite-rich belitic calcium sulphoaluminate cements.
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Nowadays, Nano silica (SN) appears to be one of the most attractive cement additives. Its incorporation improves the mechanical and physical properties of concrete. The aim of the current research is to develop a new method for preparation of nano silica fume particles using indirect sonication. The effects of the process parameters on the particles size have been investigated. These parameters include sonication power, sonication frequency, homogenizer speed, sonication time, and liquid/solid ratio. The prepared samples were monitored for particle size distribution, and level of dispersion using transmission electron microscope (TEM). The effect of the prepared nano silica fume on the ultimate properties of the concrete mixtures has been determined and compared with the original silica fume. Results obtained showed that, the proposed technique yield NS particles with average size of 57 nm and about 91% from the total particles having particle size less than 100 nm. Application of NS as cement additives (substitution) enhanced the reactivity of the produced nano silica fume, as its cement substitution by 1% resulted in compressive strength equivalent to that reached with 10% of the original silica fume substitution.
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Nano-silica had been investigated as a partial replacement of cement by many researchers, regardless its high agglomeration specially when mixed to water. Sonication is one of the methods used to de-agglomerate nano-silica particles and to improve the dispersion of nano-silica in cement matrix. This research aims to reach the optimum indirect sonication time and solid to liquid ratio that enhances the dispersion of nano-silica and consequently increases its reactivity in high strength concrete. Particle size distribution of the sonicated nano-silica particles and the corresponding specific surface area were the main keys governing the optimization process of the studied parameters. Using the optimum solid to liquid ratio with the corresponding sonication time, slump and the compressive strength of concrete were examined and compared with those without nano-silica. In addition the microstructural analysis using SEM , and XRD helped in confirming the compressive strength results. The results revealed that the optimum solid to liquid ratio is 1:10. Moreover for every concentration, there is an optimum indirect sonication time. The optimum sonication time found to be 5 minutes for solid to liquid ratio 1:10. By using the optimum concentration an improvement in compressive strength of 32% and 24% after 7 and 28 days were reached as compared to the control mix. Where in terms of slump, there is no change in the flowability of concrete due to the incorporation of nano-silica in concrete at the same mix proportions. 1.INTRODUCTION IGH strength concrete is characterized by its high mechanical and durability properties. These superior properties can be achieved by using high cementitious content with very low water to cementitious materials and lowering maximum aggregate size. The use of pozzolanic materials (silica fume, ground granulated blast furnace slag, and fly ash) is essential for the production of high strength concrete [1-2]. Silica fume belongs to the category of highly pozzolanic materials because of its high purity and consists of silica in non-crystalline form with a high specific surface and could be effectively promot the strength development of concrete, compared to the other pozzolanic materials [3]. On the other hand the development of nanotechnology can produce silica in another form with a higher specific area, and more functions compared to conventional silica fume [4-5]. This can be explained that nano-silica can improve the strength and durability characterizes of cement and concrete [6-7-8]. This improvement was due to their fine size which can fill the pores of the cement matrix. Also, due to the nucleation site effect and the pozzolnaic reactivity of the nano-silica which improves the microstructure of the cement composites [9]. Nano-silica should be dispersed to de-agglomerate its particles , in order to optimize the utilization of the nano-silica par ticles within the cement matrix. Sonication is one of the dispersion methods used to improve the effectiveness of nano-silica to modify its granulometric distribution and to improve its densification [10-11]. Serag et al [12] had studied the reactivity of nano-silica using different techniques; homegenizier, stirrer and indirect sonication. The results indicated that the reactivity significantly enhanced by the use of indirect sonica-tor. Elkady et al [13] investigated the effect of changing the indirect sonication time on the dispersion and the reactivity of nano-silica as a cement substation in concrete mixes. The results showed that; 5 minutes of indirect sonication to nano-silica prior being added to concrete leads to an improvement in workability and gaining in compressive strength reached 33% compared to the control mix. The effect of solid to liquid ratio, and the time of sonication weren't taken into consideration as factors affecting the sonication process. Nazari and Riahi [14] had found an improvement in the compressive strength reaches 33% than the control mix when using 4% na-no-silica as a cement replacement. However, E. Ghafari et al. [15] had studied the effect of using two different types of na-no-silica in UHPC. When using nano-silica at a fixed dosage 5% of the cement weight, the compressive strength was improved by 11.4% and 5.9% after 7 and 28 days, respectively than mixes containing 0% nano-silica. The flexural strength was improved by 28.6% and 14.3% after 7 and 28 days, respectively , and the water absorption was reduced by 36% than without nano-silica. This paper aims to find the optimum dispersion of Nano-Silica particles, through studying the effect of different solid to liquid ratios on the particle size distribution and specific surface area of the sonicated nano-silica particles. The effect of optimum solid to liquid ratio of nano-silica and sonication time on the fresh (workability), and hardened (compressive strength and absorption) properties of nano-silica high strength con-H ———————————————— • A. Maher El-Tair is currently pursuing PhD degree program in civil engineering in
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This paper presents the results of an industrial trial for the production of calcined clay to be used as pozzolan in cement manufacture. For the trial, a wet-process clinker rotary kiln was modified to process on dry basis the low grade kaolinitic clay used as raw material. The kaolinitic clay deposit was chosen through a screening based on geologic, chemical and mineralogical criteria, and a confirmation of reactivity with an experimental protocol at lab scale. During the calcination trial technological parameters such as rotation speed, fuel pressure and outer temperature of calcined clay were measured and coupled with the reactivity of the samples tested, thus, preliminary estimations of operational parameters can be made. The trial proved that it is possible to produce a reactive pozzolan at industrial scale by implementing small conversions on existing equipment of a typical clinker plant.
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Full-text available
This paper focuses on the characterization of setting and hardening of accelerated cementitious matrices by ultrasound propagation velocity, correlating these processes with chemical parameters and the phase evolution obtained by in situ XRD. Evolution of temperature and determination of setting times complemented this analysis. The technique employed provided a continuous monitoring of the setting and hardening of the hydrating matrix and was susceptible to changes in accelerator reactivity and phase composition. Results showed that ettringite formed by accelerator reaction improves the solid-phase interconnectivity and increases initial ultrasound velocity. P-wave propagation during the acceleration period is directly proportional to alite and C3A degrees of hydration. The influence of AFm phases to increase ultrasound velocity is stronger than ettringite and C-S-H. Based on an extensive statistical analysis, multivariate linear regressions were established between ultrasound velocity and the main chemical properties influencing its evolution, leading to a better comprehension of how these parameters are related.
Book
Supplementary cementing materials (SCMs), such as fly ash, slag, silica fume, and natural pozzolans, make a significant difference to the properties of concrete but are rarely understood in any detail. SCMs can influence the mechanical properties of concrete and improve its durability in aggressive environments. Supplementary Cementing Materials in Concrete covers the chemical, physical, and mineralogical properties of SCMs; their chemical reactions; and the resulting changes in the microstructure of concrete. The author links the properties of the material at the microstructural level with its behavior in laboratory tests, and, in turn, to the performance of the material in concrete structures under field exposure. He explains how SCMs influence the mechanical properties of concrete and improve its durability and also covers how various SCMs influence hydration reactions and the evolution of the pore structure and pore-solution composition. However, SCMs are not a panacea for concrete and improper use may be injurious to certain properties. Achieving the maximum benefit from SCMs requires an understanding of the materials and how they impact concrete properties under various conditions. Drawing on the author’s 30 years of experience, this book helps engineers and practitioners to optimize the use of supplementary cementing materials to improve concrete performance.
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Book
The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.
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The compressive strength, free and restrained drying shrinkage and cracking resistance of concrete under drying condition were investigated for ternary cementitious systems containing Portland cement, slag and fly ash. The restrained shrinkage test (ring test) was carried out following ASTM C1581. The results showed that the increased replacement level of slag or fly ash from 0 to 50% led to a gradual decrease in 28d compressive strength of concrete. The free drying shrinkage increased with the increase of slag content, but reduced with the fly ash content. The cracking resistance was well related to the free drying shrinkage of concrete, other factors such as strength also showed certain effects on cracking resistance of concrete. The cracking resistance of concrete was enhanced with the addition of fly ash while weakened with the slag replacement level up to 50%.
Thesis
Ein aktuelles Thema in der Forschung der Betonindustrie ist die gezielte Steuerung des Erstarrens und der Entwicklung der (Früh)Festigkeit von Betonen und Mörteln. Aus ökonomischer Sicht sind außerdem die Reduktion der CO2-Emission und die Schonung von Ressourcen und Energie wichtige Forschungsschwerpunkte. Eine Möglichkeit zum Erreichen dieser Ziele ist es, die Reaktivität/Hydratation der silikatischen Klinkerphasen gezielt anzuregen. Neben den bereits bekannten Möglichkeiten der Hydratationsbeschleunigung (u.a. Wärmebehandlung, Zugabe von Salzen) bietet die Anwendung von Power-Ultraschall (PUS) eine weitere Alternative zur Beschleunigung der Zementhydratation. Da bis zum jetzigen Zeitpunkt noch keine Erfahrungen zum Einsatz von PUS in der Zementchemie vorliegen, sollen mit der vorliegenden Arbeit grundlegende Kenntnisse zum Einfluss von PUS auf das Fließ- und Erstarrungsverhalten von Zementsuspensionen erarbeitet werden. Dazu wurde die Arbeit in fünf Hauptuntersuchungsabschnitte aufgeteilt. Im ersten Teil wurden optimale PUS-Parameter wie Amplitude und Energieeintrag ermittelt, die eine effiziente Beschleunigung der Portlandzement(CEM I)hydratation bei kurzen Beschallzeiten und begrenzter Zementleimtemperaturerhöhung erlauben. Mit Hilfe unabhängiger Untersuchungsmethoden (Bestimmung des Erstarrungsbeginns, der Festigkeitsentwicklung, zerstörungsfreier Ultraschallprüfung, isothermer Wärmeflusskalorimetrie, hochauflösender Rasterelektronmikroskopie (REM) wurde die Wirkung von PUS auf den Hydratationsverlauf von CEM I-Suspensionen charakterisiert. Die Ergebnisse zeigen, dass die Behandlung von CEM I-Suspensionen mit PUS grundsätzlich ein beschleunigtes Erstarren und eine beschleunigte (Früh)Festigkeitsentwicklung hervorruft. Anhand von REM-Untersuchungen konnte eindeutig nachgewiesen werden, dass die Beschleunigung der CEM I-Hydratation mit einer beschleunigten Hydratation der Hauptklinkerphase Alit korreliert. Auf Grundlage dieser Erkenntnisse wurden die Ursachen der Aktivierung der Alithydratation untersucht. Dazu wurden Untersuchungen an Einzelsystemen des CEM I (silikatische Klinkerphase) durchgeführt. Es ist bekannt, das die Hydratation der Hauptklinkerphase Alit (in der reinen Form Tricalciumsilikat 3CaO*SiO2; C3S) durch Lösungs-/Fällungsreaktionen (Bildung von Calcium-Silikat-Hydrat Phasen, C-S-H Phasen) bestimmt wird. Mit Hilfe von Untersuchungen zur Auflösung (C3S) und Kristallbildung (C-S-H Phasen) in Lösungen und Suspensionen (Aufzeichnung der elektrischen Leitfähigkeit sowie Bestimmung der Ionenkonzentrationen der wässrigen Phase, REM-Charakterisierung der Präzipitate) wurde die Beeinflussung dieser durch eine PUS-Behandlung charakterisiert. Die Ergebnisse zeigen, dass in partikelfreien Lösungen (primäre Keimbildung) eine PUS-Behandlung keinen Einfluss auf die Kinetik der Kristallisation von C-S-H Phasen hervorruft. Das heißt, auch die durch PUS eingetragene Energie reicht offensichtlich nicht aus, um in Abwesenheit von Oberflächen die C-S-H Phasen Bildung zu beschleunigen. Das weist darauf hin, dass die Bildung von C-S-H Phasen nicht durch eine Beschleunigung von Ionen in der Lösung (erhöhte Diffusion durch Anwendung von PUS) hervorgerufen wird. Eine Beschleunigung des Kristallisationsprozesses (Keimbildung und Wachstum von C-S-H Phasen) durch PUS wird nur in Anwesenheit von Partikeln in der Lösung (Suspension) erzielt. Das belegen Ergebnisse, bei denen die Bildung erster C-S-H Phasen bei geringer Übersättigung (heterogene Keimbildung, in Anwesenheit von Oberflächen) erfolgt. Unter diesen Bedingungen konnte gezeigt werden, dass PUS innerhalb der ersten 30 Minuten der Hydratation eine erhöhte Fällung von ersten C-S-H Phasen bewirkt. Diese fungieren dann vermutlich während der Haupthydratation als Keim bzw. geeignete Oberfläche zum beschleunigten Aufwachsen von weiteren C-S-H Phasen. Weiterhin ist vorstellbar, dass (in Analogie zu anderen Bereichen der Sonochemie) PUS durch Kavitation Schockwellen hervorruft, welche Partikel und wässriges Medium beschleunigen und damit erhöhte Partikelbewegungen und -kollisionen induziert. Dies wiederum bewirkt, dass die anfänglich auf der C3S-Oberfläche gebildeten C-S-H Phasen teilweise wieder entfernt werden. Damit ist das Inlösunggehen von Ca- und Si-Ionen aus dem C3S weiterhin möglich. Um den genauen Mechanismus weiter zu charakterisieren sollten mit geeigneten Methoden weitere Untersuchungen durchgeführt werden. Im zweiten Teil der Arbeit wurde der Einfluss von PUS auf das Fließverhalten von CEM I-Suspensionen untersucht. Aus der Anwendung von PUS in anderen technischen Bereichen sind unter anderem Effekte wie das Entlüften, das Homogenisieren und das Dispergieren von Suspensionen und Emulsionen mittels PUS bekannt. Mit Hilfe der Bestimmung des Luftporengehaltes, Sedimentationsversuchen und cryo-SEM Untersuchungen wurde der Einfluss von PUS auf CEM I-Suspensionen charakterisiert. Die Ergebnisse belegen, dass durch PUS eine verbesserte Homogenität und Dispergierung der CEM I-Suspension erzielt wird. Damit wird für CEM I-Suspensionen unterschiedlichster w/z-Werte eine verbesserte Fließfähigkeit festgestellt. Ergebnisse der Bestimmung von Ausbreitmaßen und Trichterauslaufzeiten zeigen, dass PUS einen direkten Einfluss vor allem auf die Viskosität der CEM I-Suspensionen besitzt. Werden Fließmitteln (FM) der CEM I-Suspension zugegeben, wird nicht in jedem Fall eine verbesserte Fließfähigkeit festgestellt. Hier scheint unter bestimmten Voraussetzungen (w/z-Wert, FM-Gehalt, PUS) die Reaktion zwischen Aluminat- und Sulfatphase des Klinkers gestört. Zur eindeutigen Klärung dieses Sachverhaltes bedarf es jedoch weiterer quantitativer Untersuchungen zum Reaktionsumsatz. Im dritten Teil der Arbeit wurden die am CEM I gewonnenen Erkenntnisse zum Einfluss von PUS auf die Hydratation an Portland-Hüttensand(HÜS)-Zement-Systemen verifiziert. Dafür wurden auch in diesem Teil der Arbeit zunächst die optimalen PUS-Parameter festgelegt und der Einfluss auf das Erstarrung- und Erhärtungsverhalten dokumentiert. Untersuchungsmethoden sind unter anderem die Bestimmung des Erstarrungsbeginns und der (Früh)Festigkeitsentwicklung, Temperaturaufzeichnungen und isothermale Wärmeflusskalorimetrie sowie REM. Die Ergebnisse zeigen, dass auch die Reaktion von HÜS-Zementen durch PUS beschleunigt wird. Weiterführende Untersuchungen belegen, dass die erzielte Beschleunigung vorwiegend auf der Beschleunigung der Alitkomponente des CEM I beruht. Im Fokus der Teile vier und fünf dieser Arbeit stand die Anwendbarkeit der PUS-Technik unter praktischen Bedingungen. Zum einen wurde die Anwendbarkeit von PUS in fertig gemischten Mörteln beurteilt. Anhand des Vergleichs wichtiger Frisch- und Festmörteleigenschaften unterschiedlich hergestellter Mörtel (beschallt im Anschluss an konventionelle Mischtechnik, beschallt im Anschluss an Suspensionsmischtechnik mit anschließender Zumischung der Gesteinskörnung und nicht beschallt) wird gezeigt, dass im Fall von Mörteln mit hohem Leimanteil eine durch PUS induzierte beschleunigte Festigkeitsentwicklung auch mit herkömmlichen Mischabläufen (ohne aufwendige Umstellung des Mischprozesses) möglich ist. Abschließend wird untersucht, ob der Herstellungsprozess von Wandbauteilen im Fertigteilwerk durch den Einsatz von PUS optimiert werden kann und ob eine Einbindung der PUS-Technik in den Fertigungsprozess ohne größeren Aufwand möglich ist. Dazu wurden in einem ersten Schritt die Frisch- und Festbetoneigenschaften eines aktuell angewendeten selbstverdichtenden Betons im Labormaßstab (Mörtel) in Abhängigkeit einer PUS-Behandlung dokumentiert und mit der seiner unbeschallten Referenz verglichen. Aufgrund der durch PUS verursachten verbesserten Fließ- und Festigkeitseigenschaften kann die beschallte Mörtelrezeptur hinsichtlich Fließmittelgehalt und Dauer der Wärmebehandlung optimiert werden. Somit werden ca. 30 % der Fließmittelzugabe und 40 % der Dauer der Wärmebehandlung eigespart. Eine Einbindung der PUS-Technik in das betrachtete Fertigteilwerk ist nach Überprüfung der konstruktiven Gegebenheiten der Fertigungsstrukturen ohne größeren Aufwand möglich.