Figure 3 - available via license: Creative Commons Attribution-NonCommercial 4.0 International
Content may be subject to copyright.
Photograph of a sample of concrete containing pebble aggregate after the fracture test by the wedge splitting method.
Source publication
The objective of this work was to compare the fracture energy of mortar and concretes produced with crushed rock and pebble aggregates using zero, 10, 20, 30 and 40% of aggregates mixed with standard mortar and applying the wedge splitting method to achieve stable crack propagation. The samples were cast in a special mold and cured for 28 days, aft...
Contexts in source publication
Context 1
... 1 illustrates the behavior of the pebble and crushed rock aggregates in the concretes under study. At least five fractured samples of each composition were used to count the aggregates, based on the fractured surfaces illustrated in Figures 3 and 4. The detached, fractured and mixed aggregates were counted using a stereoscopic microscope. ...
Similar publications
Abstract:
In this study, the silica fume was added to C20 concrete and the interrelated load-deformation and time-deformation relations of the two different straight and pin beam samples have been examined. For that purpose, the silica fume amounting 16% of the cement was added to the concrete mixture in standard measures. The 4 of the prepared 8 b...
The objective of this search is to study the impact of the maximum size, type and content of coarse aggregate (CA) on the mechanical properties of Modified Reactive Powder Concrete (MPRC) in terms of compressive (fcu) and flexural (fr) strengths. (32) Mixes of MRPC are designed, mixed, molded and tested. The results showed that high (fcu) can be ac...
Introduction
The aim of the present study was to evaluate and compare the compressive strength (CS) of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cement when mixed with propylene glycol (PG).
Methods and Materials
Twenty four custom-made split molds with 5 holes in each were prepared. Molds were allocated into eight groups...
An experimental program has been carried out to investigate the effect of edge-slope on compressive strength of concrete specimens. In this study, effect of such slope was investigated by testing 100 standard cylinder specimens and 40 standard cubes. When molds are put on a slanted place, wet concrete starts to flow through the open end of mold. It...
Aim:
The present study was conducted with the objective of evaluating the effect of different liquid-to-powder ratios on setting time of white mineral trioxide aggregate (WMTA) and the effect of adding disodium hydrogen phosphate (Na2HPO4) to white MTA (NAMTA).
Materials and methods:
Sixty samples were prepared in plastic annular molds with a di...
Citations
... Pebble B, in particular, demonstrates a higher degree of roundness. Bond strength is one of the critical factors determining the overall mechanical performance of concrete, as it dictates the rate and extent of crack propagation within the material under external forces [27]. Crushed stone, derived from quarried bedrock, presents a Bond strength is one of the critical factors determining the overall mechanical performance of concrete, as it dictates the rate and extent of crack propagation within the material under external forces [27]. ...
... Bond strength is one of the critical factors determining the overall mechanical performance of concrete, as it dictates the rate and extent of crack propagation within the material under external forces [27]. Crushed stone, derived from quarried bedrock, presents a Bond strength is one of the critical factors determining the overall mechanical performance of concrete, as it dictates the rate and extent of crack propagation within the material under external forces [27]. Crushed stone, derived from quarried bedrock, presents a distinct angularity on its surface, as shown in Figure 6a. ...
... Crushed stone, derived from quarried bedrock, presents a distinct angularity on its surface, as shown in Figure 6a. This angularity promotes strong Bond strength is one of the critical factors determining the overall mechanical performance of concrete, as it dictates the rate and extent of crack propagation within the material under external forces [27]. Crushed stone, derived from quarried bedrock, presents a distinct angularity on its surface, as shown in Figure 6a. ...
Bolivia has abundant pebbles, while the supply of crushed stone is limited and unstable. Thus, the resource utilization of local pebble as a coarse aggregate and the guarantee of concrete durability are the key scientific issues in the Sucre Highway Project. In this paper, a comparative analysis was conducted of the performance of crushed stone concrete and pebble concrete. Additionally, the impact of fly ash on the water permeability resistance of concrete was investigated. The results indicate that the apparent density, bulk density, and void ratio of pebbles are lower than those of crushed stone, and the aggregate gradation of pebbles is dispersed. The type of aggregate is the primary factor influencing the splitting tensile strength of concrete, with the main failure modes of pebble concrete being slurry cracking, aggregate crushing, and interface debonding. While aggregate and fly ash have a minor effect on compressive strength, they significantly impact flexural tensile strength; however, all concretes meet the requirements for extra-heavy, very heavy, and heavy traffic load levels. In terms of impermeability, fly ash effectively mitigates the negative impact of aggregate type on the impermeability of concrete. These findings support the application of pebble concrete in the highway project.
... Specifically, sea pebbles are used as a coarse aggregate (referred to hereafter as sea pebble concrete, SPC) due to their accessibility and abundant reserves. Over the years, the use of pebbles as a coarse aggregate in island reef construction engineering has proven feasible [8,9]. Because of its superior performance in fluidity, self-compaction, and pumpability, hydraulic structure codes recommend using pebbles as a coarse aggregate in large-scale concrete structures like infilled piles and foundations [10][11][12]. ...
Obtaining river or sea pebbles from local resources for concrete production is considered an economical and eco-friendly alternative, particularly in marine and island-offshore engineering. However, the resulting changes in the mechanical properties of these concrete have attracted attention. This study investigates the compressive behavior of concretes where river or sea pebbles partially (i.e., 33% and 67%) or fully (i.e., 100%) replace traditional gravel as coarse aggregate, using a noncontact full-field deformation measurement system based on digital image correlation (DIC). Compared to the traditional gravel concrete (GC), compressive strengths of the river pebble concrete (RPC) at constitution rates of 33%, 67%, and 100% decreased by 6.5%, 29.8%, and 38.9% while those values of the sea pebble concrete (SPC) decreased by 13.1%, 32.7%, and 44.3%, respectively. Meanwhile, SPC exhibited slightly lower compressive strength than RPC. The peak strains of both SPC and RPC decreased at lower substitution rates, although their stress-strain curves resembled those of GC. In contrast, RPC and SPC at higher substitution rates exhibited a noticeable stage of load hardening. Full-field deformation data and interfacial characteristics indicated that the compressive failure modes of both RPC and SPC showed significant interfacial slipping between pebbles and mortar with increasing coarse aggregate substitution rates. In comparison, fractures in coarse aggregate and mortar were observed in damaged GC. The study demonstrated that the spatio-temporal compressive deformation response and failure modes of SPC and RPC were distinct due to the introduction of pebbles, providing insights for engineering applications of river/sea pebble concrete in practical offshore or island construction projects.
... This observation was an indication of the reactivity of the limestone sand with the cement paste and the formation of calcium aluminate hydrates. As already confirmed in previous studies on coarse aggregates [40,76,77], the rough surface and the mineralogy of crushed limestone sand in the equivalent mix EM, have favored better interlocking and better continuity between the paste and the aggregate, thus a better cement-aggregate interface. ...
In the context of sustainable development and environmental protection, the current study aims to give scientific evidence of the feasibility of replacing natural siliceous sand with crushed limestone sand in concrete. It assesses the effect of this replacement by comparing concretes without natural sand to a reference mix incorporating natural sand. For fixed water-to-cement ratio, cement content, and coarse aggregates proportions, and for different dosages of admixture to reach the same slump, the results proved that the concrete containing natural sand required more admixture to reach the same slump value as the crushed limestone sand concrete. For the same workability, the compressive and flexural strengths were not affected by the total replacement of natural sand with crushed sand. The three types of concrete fell within the same range of durability even though scanning electron microscope (SEM) analysis seemed to reveal a better paste-fine aggregate interface for crushed sand concrete. The concrete properties could be maintained when using crushed limestone sand conforming to the standard grading requirements, as the only fine aggregate in concrete.
... However, it is worth noting that despite this deviation, it achieved the desired strength target of 70% on day 2 of hardening. Figure 3 displays an image of the microstructure of the fracture of the sample of RHC containing MCU-95, captured with a ZEISS Axio Vert.A1 microscope via reflection shooting at a magnification of ×500. Figure 3 demonstrates that the cement stone with the addition of MCU-95 had a more homogeneous structure than the cement stone without additives [37]. The addition of active SiO2 created conditions for the formation of a structure with the densest packing of crystals, consisting mainly of low-base calcium silicate hydroxide (Ca5(OH)2Si6O16- Figure 3 demonstrates that the cement stone with the addition of MCU-95 had a more homogeneous structure than the cement stone without additives [37]. ...
... Figure 3 displays an image of the microstructure of the fracture of the sample of RHC containing MCU-95, captured with a ZEISS Axio Vert.A1 microscope via reflection shooting at a magnification of ×500. Figure 3 demonstrates that the cement stone with the addition of MCU-95 had a more homogeneous structure than the cement stone without additives [37]. The addition of active SiO2 created conditions for the formation of a structure with the densest packing of crystals, consisting mainly of low-base calcium silicate hydroxide (Ca5(OH)2Si6O16- Figure 3 demonstrates that the cement stone with the addition of MCU-95 had a more homogeneous structure than the cement stone without additives [37]. The addition of active SiO 2 created conditions for the formation of a structure with the densest packing of crystals, consisting mainly of low-base calcium silicate hydroxide (Ca 5 (OH) 2 Si 6 O 16 -4H 2 O ⇒ (CaO/SiO 2 < 1.5)), which confirmed the theory presented in [38]. ...
... Figure 4 below illustrates the effect of MCU-95 on the kinetics of strength gain of RHC during the early ages of curing, where SD stands for standard deviation. Figure 3 demonstrates that the cement stone with the addition of MCU-95 had a more homogeneous structure than the cement stone without additives [37]. The addition of active SiO2 created conditions for the formation of a structure with the densest packing of crystals, consisting mainly of low-base calcium silicate hydroxide (Ca5(OH)2Si6O16-4H2O(СаО/SiO2˂1.5)), which confirmed the theory presented in [38]. ...
This article presents the results of research conducted to determine the possibility of accelerating strength gain and enhancing the operational reliability of concrete. The study tested the effects of modern modifiers on concrete in order to select the composition of rapid hardening concrete (RHC) with better frost resistance characteristics. A basic composition of RHC grade C 25/30 was developed using traditional concrete calculations. Based on the analysis of previous studies by other authors, two basic modifiers (microsilica and calcium chloride (CaCl2)) and a chemical additive (a hyperplasticizer based on polycarboxylate esters) were selected. Then, a working hypothesis was adopted to find optimal and effective combinations of these components in the concrete composition. In the course of experiments, the most effective combination of additives for obtaining the best RHC composition was deduced by modeling the average strength values of samples in the early ages of curing. Further, RHC samples were tested for frost resistance in an aggressive environment at the ages of 3, 7, 28, 90, and 180 days to determine operational reliability and durability. The test results showed a real possibility of accelerating concrete hardening by 50% at the age of 2 days and achieving up to 25% strength gain by using both microsilica and calcium chloride (CaCl2). The best frost resistance indicators were observed in the RHC compositions with microsilica replacing part of the cement. The frost resistance indicators also improved with an increase in the amount of microsilica.
... There is also no difference in the so-called crack path. When comparing the fracture behavior of the LCs, as shown in Fig. 6, with the rupture of a conventional concrete, in the latter it is easily observable that most of the aggregates of gravel are intact, although some aggregates can be separated from the concrete matrix [45]. ...
This work presents the production of expanded clay aggregates (EA) by firing at 1300 °C (EA/1300), a high temperature for EA production. Therefore, the material was produced in an attempt to maximize lightness. Initially, it was characterized the natural clay and the expanded clay aggregate. The EA/1300 had a density of 0.56 kg/dm³ and a strength of 0.13 MPa, reaching an expansion of 645%, while the EA/1250, clay aggregate fired at 1250 °C and produced for comparison, had a density of 0.85 kg/dm³, a strength of 0.80 MPa, and an expansion of 415%. Subsequently, it was made a lightweight concrete (LC/1300) evaluating its physical and mechanical properties. The LC/1300 had an average compressive strength of ∼4 MPa, and a density of 1.22 kg/dm³. The LC/1250 had a density of 1.43 kg/dm³ and a compressive strength of ∼10 MPa. Despite the strength reduction, it was concluded that EA/1300 can be a viable material for the production of lightweight concrete (LC), particularly as concrete artifacts, non-structural blocks, void filling, and in thermal and acoustic insulation applications. This novel material showed low density, with a reduction of 15% in relation to the LC/1250, maintaining the properties of lightweight concrete with EA – chemical inertness and fireproof – and with a strength higher than commercial lightweight concrete with polymeric aggregates.
... In contrast, the ITZ of the smooth natural sand is weaker and the sand grains could be detached from the cement paste after reaching the ultimate load when the plastic wastes with a smooth surface are used as an alternative to natural sand (Saikia and De Brito, 2014), as demonstrated in Figure I.36. Similarly, when studying the coarse aggregates, (Ribeiro et al., 2011) show that the aggregates could be dislodged from the matrix in case of a weak bond or be fractured without dislodgment in case of a better bond. They have found that the surface roughness of the crushed aggregate provides a good anchorage that exhibits the second behavior and favors a strong interface between the cement paste and the aggregate. ...
... Likewise, the microstructural studies led on coarse aggregates show that the limestone coarse aggregate contributes to a better anchorage between the cement paste and the aggregate compared to the siliceous aggregate with a smooth surface (Ribeiro et al., 2011;Bentz et al., 2015). (Monteiro et al., 1985) also detect an epitaxial growth of some hydration products on the limestone coarse aggregates surface that is not detected in the ITZ of quartzite aggregate. ...
In Lebanon, good quality natural siliceous sand becomes rarely available, and for environmental reasons, its extraction is subjected to governmental restrictions. This problem affects the construction sector through the cost and the quality of concrete. Moreover, this sand is too fine to be used alone as fine aggregate in concrete mixes. Therefore, to meet the grading requirement of the ASTM C33, the standard applied in Lebanon, this sand is currently mixed with an appropriate proportion of a coarser crushed limestone sand which compensates the fineness of the natural sand. Accordingly, finding an alternative to natural sand in concrete becomes essential to reduce its economic and environmental problems and to avoid the dependency of the construction field on its quality and availability in the Lebanese market. After a literature review of existing alternatives around the world, it seems that the replacement of natural sand by the local crushed limestone sand could be an appropriate solution in the Lebanese context due to the abundance and good quality of this sand. Hence, the current study is the first in this country that aims to give scientific evidence of this solution before being applied in the Lebanese market. Its objective is to assess the effect on the concrete performance of the total replacement of natural siliceous sand by crushed limestone sand. In order to respond to the objective of the study, the behaviors of concrete mixes incorporating normalized crushed sands without natural sand are compared to those of reference concrete containing the conventional combination of natural sand and crushed sand, to verify that their performances could be maintained, for three normal strength concrete mixes and one high strength concrete. Since the crushed sand, provided currently from the limestone quarries, is too coarse to directly replace the natural sand, the first step consists of constructing two types of normalized crushed sand conforming to the standard grading requirements. For each type of fine aggregate, the fresh concrete properties, mechanical behavior, and durability are investigated. The effects of the mineralogy, morphology, and particle size distribution of fine aggregates on these various properties are then evaluated. A microstructural analysis is also conducted to depict the variations at the interface between the cement paste and the different types of sand grains and to try to explain the differences that could exist at the macro scale between the different types of concrete. Furthermore, since the production of the normalized crushed limestone sand could impose many industrial and economic constraints to limit the high percentage of fines, the performance of normal and high strength concretes, incorporating crushed sand with a percentage of fines (< 75 µm sieve) exceeding the limit imposed by ASTM C33 (7%), is evaluated following a performance-based approach. For fixed water to cement ratio, cement content, and coarse aggregates proportions, and for different dosages of admixture to reach the same slump value, the results prove that the concrete performance could be maintained when using the normalized crushed limestone sand conforming to the standard grading requirements or the fine crushed limestone sand with a high percentage of fines. Additionally, the overview on the economic and environmental impacts on the Lebanese context verifies the feasibility of the use of crushed limestone sand as the only fine aggregate.
... In fact, being less angular (see Fig. 2), less rough (see Fig. 3) and stiffer (see Table 2) than crushed granite particles, the river gravels present a lower adhesion (i.e., matrix-aggregate bond) with the surrounding cement mortar. For this reason, even though the river gravel aggregates present higher compressive strength (see Table 2), the concrete mixtures produced with them present a weaker Interfacial Transition Zones (ITZs) in comparison with the ordinary concrete mixtures produced with crushed granite aggregates [54,55] and, as a consequence, it determines a more fragile fracture (see Fig. 6) and a lower compressive strength (the mixtures MP and MJ displayed values 15% and 10% lower, respectively, than MG mixture at 28 days). Moreover, the more fragile failure behavior characterizing the concrete mixture incorporating river gravels is confirmed by the results reported in Fig. 7 in terms of measured strain at peak stress. ...
This study reports the results of a comprehensive experimental campaign aimed at demonstrating the feasibility of using river gravels in substitution of ordinary crushed aggregates for the production of high strength Steel Fiber-River Gravel-Self Compacting Concrete (SFRGSCC). Due to geomorphological reasons, the river gravels represent the most common type of aggregates used in Amazon region for ordinary structural concrete production but only few researches focused on the use of this kind of raw material for the production of high performance cement-based composites. In fact, the river gravels present different intrinsic characteristic in comparison with crushed rocks such as, higher density and elastic modulus, rounded shape with a smoother surface and a more brittle behavior. As a consequence, when embedded in a cement-based matrix they can significantly affect the rheology and mechanical performance of both self-compacting concrete matrices (RGSCC) and Fiber Reinforced Concrete (SFRGSCC).
... In this experimental setup, large specimens of the size of bricks can be tested. 5,8,[20][21][22][23][24][25][26][27][28][29][30] Most data produced using the wedge-splitting test are reported for pure magnesia, magnesia spinel and magnesia carbon refractories, 5,8,9,[24][25][26][27] which are out of the scope of this paper. A relatively low number of studies provide data for high alumina castables and alumina-based shaped materials. ...
... A relatively low number of studies provide data for high alumina castables and alumina-based shaped materials. 20,22,23,[28][29][30] Ribeiro and Rodrigues 22 applied the wedge splitting method to characterise fracture energy of two high-alumina refractory castables. Miyaji et al. 29 analysed five different castable formulations and introduced a figure of merit derived from the Load-Displacement curve to evaluate the thermal shock damage resistance. ...
Basic relationships between the microstructure and the texture of refractories and their toughness have been established. A series of commercial materials has been chosen in order to highlight the influence of microstructural characteristics on fracture behaviour and associated toughness. Silica, silica–alumina and silica–alumina–zirconia based shaped refractories and a calcium aluminate cement bonded concrete have been analysed. Extensive microstructural characterisation has been performed using a combination of techniques, including chemical analysis by X-ray fluorescence, X-ray diffraction, reflected light optical microscopy and scanning electron microscopy with analysis by dispersive energies. Fracture has been characterised using stable fracture tests of SENB tested in 3 point bending. Stability was reached in displacement and crack mouth opening displacement controlled tests. Size effect has been analysed by using two different specimen sizes and relative notch lengths. For the range of microstructures studied, the obtained results have allowed to characterise toughness and establish the relationships toughness-microstructure and texture.
... Here, the initial notch was made by inserting a steel plate into the specimens during the casting and the plate was taken out after one day. The use of special moulds to produce notch and grooves in mortar samples has been widely reported [28]. However, this method is generally applicable for concretes with small aggregate size. ...
In the present paper, the well-known wedge splitting test (WST) is applied on specimens with
different geometries (S= 150, 200, 300 mm) and variants of the specimens’ configurations. K-calibration (B1)
and T-stress (B2) calibration curves for such specimens are introduced. The objective was to compare and
discuss the values of the calibration curves dependent on the specimen’s geometries and on three different
specimens' configurations: homogenous specimen; specimen with marble plates forming the groove for load
application and specimen with glued marble plates.
... Here, the initial notch was made by inserting a steel plate into the specimens during the casting and the plate was taken out after one day. The use of special moulds to produce notch and grooves in mortar samples has been widely reported [28]. However, this method is generally applicable for concretes with small aggregate size. ...
In the present paper, the well-known wedge splitting test is applied on specimens made from foam concrete. In the case of this material the whole test specimens cannot be made from foam concrete but the rectangular groove, needed for the load transmission pieces, has to be made of stiffer material (typically marble). K-calibration (B1) and T-stress (B2) calibration curves for such specimens are introduced. The objective was to compare and discuss the calibration curves for the homogeneous case, the case with marble parts and the case with marble parts considering the glued marble/foam concrete interface
