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Corrigendum to "Effect of Nano-gypsum on Mechanical Properties of Cement Admixed Marginal Silty Soil" [Construction and Building Materials 408 (2023) 133639]
Abstract
Even though the chemical stabilization is by far the most common ground improvement technique, very few studies have been conducted on the joint incorporation of two or more additives (cement-nanogypsum mix) to stabilise soft soil. This study investigates the effect on the mechanical properties of cement-stabilised silty soft soil (CSS) using nano-gypsum (NG). Unconfined compression strength (UCS) test trials were conducted to achieve
soft soil conditions. The effect of NG and cement on soft soil was investigated by performing Atterberg limit, compaction, UCS, and Direct shear tests. The soil was treated with four percentages (10%, 15%, 20%, and 25%) of cement and with three percentages (1%, 1.5%, and 2%) of NG by its dry unit weight. The test results showed that the plasticity index of the soil was reduced significantly by the addition of stabilizers (Cement-NG mix) making the soil stiffer. The compaction tests suggested that optimum cement content was 20% for CSS and for cement-NG mix maximum strength was achieved at cement: NG proportion of 20:1. The unconfined compression strength (UCS) was increased by 9.11 times in comparison to untreated soft soil at cement: NG proportion of 20:1.5. The direct shear test (DST) suggested that there was an increase in cohesion by 4.44 times in comparison to the untreated sample at the soil–cement-NG combination of 78.5: 20: 1.5. However, the angle of internal friction remained almost unchanged. The development of cementitious substances was confirmed through XRD spectroscopy. Microstructural and chemical properties were observed using combined FESEM-EDAX analysis and Fourier transform infrared spectroscopy (FTIR). The multivariate linear regression (MLR) predictive model was developed for the unconfined compressive strength and failure strain as a function of various parameters considered in the study. The test results demonstrated that the combination of cement and NG can result in remarkable improvement in the geotechnical properties of soft soil. The use of NG may also reduce the demand for cement in deep cement mixing technique, which eventually reduces the carbon footprint and renders the ground improvement technique, ecologically beneficial.
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Fused deposition modeling (FDM) printed polymers are rarely used as a structural material due to anisotropic and low mechanical properties compared with conventional composites. In recent years, greater need has been expressed for recycling of materials, such as recyclable FDM, at the end of service life to reduce environmental pollution and manufacture cost. However, how the amount of resin uptake in the skin and skin/core interphase affects the bending and shear performance of the sandwich composites when replacing the low strength and ductile core (conventional core) with a high strength and brittle core (FDM printed PLA (polylactic acid) core) still remains unclear. A new manufacturing routine is needed to improve the incorporation of FDM printed polymers in composite structures. In this work, FDM printed PLA was used as core material and sandwiched between two unidirectional glass fiber reinforced polymer (GFRP) skins to form a sandwich composite by compression-molding (CM) process, which provides a good manufacturing strategy for skin/core interphase modification. The significance of the CM process is proved by investigating the effect of resin uptake on bending and in-plane/out-of-plane shear performances. Current first order shear deformation (FSDT) theory lacks a direct connection between the in-plane shear stress and out-of-shear stress in the core region of sandwich composites. With the help of DIC, a connection between the in-plane shear and the out-of-plane shear strain was built and in-plane shear properties can acquire through out-of-plane shear properties, hence reducing the redundancy of sample preparation or the need for simulation. A significant improvement was found compared with the optimized resin uptake (Optimized resin uptake range: 20.43%–22.86 wt%) 3D-printed PLA core sandwich composite and lowest performance sandwich composite (Improvement: in-plane shear strength (∼34%)/modulus (∼29%), out-of-plane shear strength (∼25%)/modulus (∼31%), specific peak bending load (∼19%)). Compared with balsa core sandwich composites, the 3D-printed cores are suitable for use in composite sandwich structures in many applications with a satisfactory strength-to-weight ratio.
The interfacial bonding strength of the two deposited layers under the material extrusion process is always considered a shortcoming in the 3D-printed part. To address this issue, an extra polymer coating is added to the extruded filament by adding another self-designed nozzle concentrically to the original nozzle on the 3D printing head. Three filaments were used in the fabrication process: continuous carbon fiber as reinforcement filament, polylactic acid (PLA) filament as polymer substrate filament, and carbon nanotube (CNT)/PLA filament as polymer coating filament. In addition, the effect of CNT concentration on the 3D-printed thin-walled cylinder CNT/PLA/continuous carbon fiber (CF) composite was investigated by compressive buckling tests. Compared with 3D-printed thin-walled cylinder PLA/CF composite, the buckling loads were enhanced by 16.7%, 32.5%, 40.7%, and 50.1% under 5 wt%, 10 wt%, 15 wt%, and 20 wt% CNT concentration in the PLA polymer filament. This new 3D printing design creates a new possible solution to strengthen the 3D-printed part and can border the application of 3D-printed parts by varying polymer coating type through modifying the nanofiller-modified polymer filament.
A comprehensive experimental programme was undertaken to study the parametric effect on mechanical behaviour of fine-grained soils by inclusion of glass fibres. The behaviour of both unreinforced and reinforced soil specimens under uni-axial compression was systematically investigated corresponding to fibre length, fibre content, soil density, moisture content and loading rate. The unconfined compression strength test (UCS) results confirmed the reliance of UCS improvement index (I UCS) on the selected parameters. For 18 mm fibre length and 0.9% fibre content, UCS improvement index of 71.68% was observed. The interface morphologies were studied by analysing the failure patterns and microstructural mechanisms through scanning electron microscopy. Artificial neural network (ANN) was used to develop an estimation model of the relationship between soil strength and different reinforcement parameters. This study is expected to help in better understanding of mechanical behaviour of FRS and its subsequent application in the field.
Abstract: Cement paste is the most common construction material being used in the construction
industry. Nanomaterials are the hottest topic worldwide, which affect the mechanical properties of
construction materials such as cement paste. Cement pastes containing carbon nanotubes (CNTs) are
piezoresistive intelligent materials. The electrical resistivity of cementitious composites varies with
the stress conditions under static and dynamic loads as carbon nanotubes are added to the cement
paste. In cement paste, electrical resistivity is one of the most critical criteria for structural health
control. Therefore, it is essential to develop a reliable mathematical model for predicting electrical
resistivity. In this study, four different models—including the nonlinear regression model (NLR),
linear regression model (LR), multilinear regression model (MLR), and artificial neural network model (ANN)—were proposed to predict the electrical resistivity of cement paste modified with carbon nanotube. Furthermore, the correlation between the compressive strength of cement paste and the electrical resistivity model has also been proposed in this study and compared with models in the literature. In this respect, 116 data points were gathered and examined to develop the models, and 56 data points were collected for the proposed correlation model. Most critical parameters influencing the electrical resistivity of cement paste were considered during the modeling process—i.e., water
to cement ratio ranged from 0.2 to 0.485, carbon nanotube percentage varied from 0 to 1.5%, and curing time ranged from 1 to 180 days. The electrical resistivity of cement paste with a very large number ranging from 0.798–1252.23 Ω.m was reported in this study. Furthermore, various statistical assessments such as coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE), scatter index (SI), and OBJ were used to investigate the performance of different models. Based on statistical assessments—such as SI, OBJ, and R2—the output results concluded that the artificial neural network ANN model performed better at predicting electrical resistivity for cement paste than the LR, NLR, and MLR models. In addition, the proposed correlation model
gives better performance based on R2, RMSE, MAE, and SI for predicting compressive strength as a function of electrical resistivity compared to the models proposed in the literature.
Silty soil has the characteristics of low natural moisture content and poor viscosity, and the strength and deformation required for foundation engineering can be satisfied by reinforcing and improving the silt. In order to study the reinforcement and improvement effects of polypropylene (PP) fiber and fly ash (FA) on cement–silty soil, an unconfined compressive strength (UCS) test, scanning electron microscope (SEM) test, and X-ray diffraction (XRD) analysis test were carried out. Cement (mixed amounts are 4%, 8%, 12%, and 16% of dry soil mass) was used as the basic modifier, and PP fiber (mixed amounts are 0%, 0.15%, 0.3%, and 0.45% of dry soil mass) compounded with FA (adding amounts of 0%, 5%, 10%, and 15% of dry soil mass) were used as an external admixture of cement–silty soil to study the mechanical properties, curing mechanism, and microstructure of the modified soil in different ages of 7 d, 14 d, 28 d, and 60 d. The test results show that with the increase in cement and curing age, the UCS of the modified soil increases, and with the increase in the PP fiber and FA, the UCS of the modified soil first increases and then decreases; there is an optimal content of FA and PP fiber, which are 10 and 0.15%, respectively. A large amount of C-S-H and AFt substances are produced inside the modified soil to cover the surface of soil particles or fill in the pores between soil particles, forming a tight spatial network structure and improving the mechanical properties of the cement–soil. The intensity of the diffraction peaks of the mineral components within the modified soils is more influenced by the cement and age, and the effect of FA is weaker. The stress–strain curve of the modified soil is divided into elastic stage, plastic deformation stage, and strain-softening stage, and the specimens in each stage have corresponding deformation characteristics. By analyzing the behavioral characteristics and curing improvement mechanism of modified soil from the duo perspective of macro-mechanical properties and microstructural composition, it can provide some basis for the engineering application of silty soil.
The effectiveness of the use of waste fly ash (FA) and cement (OPC) in the stabilization of subgrade soils and the reasons likely to influence the degree of stabilization were investigated. Incorporating waste fly ash (FA) and cement (OPC) as additives leads to significant environmental and economic contributions to soil stabilization. This study involves laboratory tests to obtain the Atterberg limit, free swell index (FSI), the unconfined compressive strength (UCS), the California bearing ratio (CBR), and the scanning electron microscope (SEM). The test results for the subgrade soil illustrate that the Atterberg limit, plasticity index, and free swell index are decreasing with the addition of different proportions of fly ash and cement, i.e., 0%, 5%, 10%, 15%, and 20% and 0%, 2%, 4%, 6%, and 8%, respectively. The CBR value of untreated soil is 2.91%, while the best CBR value of fly ash and cement mixture treated soil is 10.12% (20% FA+8% OPC), which increases 71.34% from the initial value. The UCS of untreated soil is 86.88 kPa and treated soil with fly ash and cement attains a maximum value of 167.75 kPa (20% FA+8% OPC), i.e., increases by 48.20% from the initial value. The tests result show that the stability of a subgrade soil can be improved by adding fly ash and cement. While effectiveness and usability of waste FA and cement are cost-effective and environmentally friendly alternatives to expansive soil for pavement and any other foundation work in the future.
Micropiles, on account of their versatility, can serve as both a new foundation and a long-term option for prevailing foundations without disturbing the subgrade underneath. They can improve highway facilities, historically significant structures, or distressed structures. The present laboratory model study is conducted on a square footing installed with micropiles all around it and subjected to vertical concentric loading. A parametric analysis based on the impact of five micropile parameters is also performed. The results obtained from this study reveal that the inclination of micropiles has little effect on ultimate vertical load but can profoundly impact the horizontal load. As the diameter of micropiles is progressively increased from 10 to 20 mm, the bearing capacity improves by around 27%. As the micropile spacing decreases from five times diameter (5d) to three times diameter (3d), the footing system’s bearing capacity increases nearly by 22.2%. The bearing capacity ratio shows a reduction beyond the value of L/b = 2. Installing micropiles nearer to the footing edge (ED/b = 0.3) provided approximately 76% improvement with respect to the unreinforced footing. The optimum value of the different parameters is equal to L/b = 2, d = 20 mm, ED/b = 0.3, and S/d = 3. There is a 98% improvement in bearing capacity at the optimum values for 30° inclined micropiles.
In recent years, Nano-technology significantly invaded the field of Geotechnical engineering, particularly in soil stabilisation techniques. Stabilisation of weak soil is envisioned to modify various soil characteristics by the addition of natural or synthetic materials into the virgin soil. In the present study, laboratory experiments were executed to investigate the influence of nano-silica particles in the consistency limits, compressive strength of the soft clay blended with cement. The results revealed that the high compressibility behaviour of soft clay modified to medium-stiff condition with fewer dosages of cement and nano-silica. The mechanism behind the strength development is verified with the previous researches as well as from Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction test (XRD) and Scanning Electron Microscopy (SEM) analysis. Based on the results, the presence of nano-silica in soft clay blended with cement has a positive effect on the behaviour of soil. This technique proves to be very economical and less detrimental to the environment.
The nanoparticles are basically the smallest particles known in the soil environment. Soil being a particulate material and its essential particles have a different size range. On the other hand, nanoparticles range between 1 and 100 nm and most properties of nanoparticles are size-dependent. In this paper, an experimental study was conducted to study the improvement of strength characteristics of soil treated with SiO2 nanomaterial. Also, X-ray diffraction tests were performed on collected soil samples and nanomaterial. Furthermore, scanning electron microscope analysis was performed to identify the underlying mechanisms of nanomaterials. Soft soils of two types were collected and were treated with nano-silica (SiO2) additive at percentages of 0.5%, 1.0%, 1.5%, and 2.0%. The test outcomes revealed that the unconfined compressive strength increased significantly with increasing percentage of nano-silica. Moreover, a decrease in maximum dry density and increase in optimum moisture content of treated soil were observed. The addition of nanoparticles increased the sample’s reactivity even at an early age and subsequently strength was increased. Therefore, the main aim of this paper was to stabilize soft soil deposits for utilization of various geotechnical applications for sustainable environment.
Sands reinforced by hydraulic binders (cement) have constituted in recent decades a major asset for the expansion of several areas of engineering. The mechanical behavior of sand-cement mixtures has undergone some controversies studied on the Chlef sand. In this paper, we present an experimental study to investigate the mechanical behavior of a sandy soil reinforced by a hydraulic binder (cement), using the direct shear apparatus emphasizing on the shear strength characteristics and the vertical deformation variation of cemented reinforced sand. The parameters used in this study are mainly: relative density (Dr = 80%), normal stress (σn = 100, 200, 400 kPa), water content (3, 7 and 10%), cement content (2.5, 5, 7.5 and 10 %) and cure time (7, 14 and 28 days). The experimental results show that the mechanical characteristics in terms of internal cohesion (C) and internal frication angle (φ) give a better mechanical performance with the binder inclusion, and the cure conditions play an effective role on the improvement of the shear strength. This result also showed that 10% of the cement content gave us a maximum value of shear strength and an optimal influence on the mechanical characteristics. The addition of cement not only improves the shear strength of soil, but also provides diversity in the resistance against the deformations imposed load, which can be established by a dilatant character.
In this study, the effects of metakaolin clay (MK) on the rheological properties, setting time, compressive strength, and toughness of cement grouts with water-cement ratios (w/c) of 0.6 and 1.0 were investigated. Based on the information in the literature, the amount of MK used in various mix designs varied up to 10 % by the weight of cement. The compressive stress–strain behavior of cement grout modified with MK was investigated up to 90 days of curing. The addition of 10 % of MK increased the apparent viscosity of the cement grout from 20 cP to 62 cP and from 13 cP to 44 cP with w/c ratios of 0.6 and 1, respectively. Setting time of cement grout mixes with a w/c ratio of 1.0 had longer initial and final setting times than the grout mixes with a w/c ratio of 0.6. The addition of 10 % MK increased the compressive strength of the cement grouts with w/c ratios of 0.6 and 1 from 8 MPa (1,175 psi) to 30.1 MPa (4,366 psi) and from 2.4 MPa (348 psi) to 17.8 MPa (2,582 psi) after 90 days of curing, respectively. The addition of 10 % MK increased the toughness of the cement grouts with w/c ratios of 0.6 and 1 from 1.42 J·m−3 to 2.27 J·m−3 and from 0.94 J·m−3 to 1.38 J·m−3 after 90 days of curing, respectively. The Vipulanandan p–q model was used to predict the changes in stress-stain behavior with curing time. The Vipulanandan rheological model also has a limit on the shear stress were as the other model did not have a limit. Based on the Vipulanandan rheological model, the maximum shear stresses produced by the portland cement grouts with w/c ratios of 0.6 and 1 with 0 MK were 58 Pa and 33 Pa, respectively. The addition of 10 % MK to the Portland cement (PC) grouts increased the maximum shear stresses by 155 % and 136 % for w/c ratios of 0.6 and 1, respectively.
Soft ground improvement techniques have become most practical and popular methods to increase soil strength, soil stiffness and reduce soil compressibility including the soft Bangkok clay. This paper focuses on comparative performances of prefabricated vertical drain (PVD) using surcharge, vacuum and heat preloading as well as the cement-admixed clay of Deep Cement Mixing (DCM) and Stiffened DCM (SDCM) methods. The Vacuum-PVD can increase the horizontal coefficient of consolidation, Ch, resulting in faster rate of settlement at the same magnitudes of settlement compared to Conventional PVD. Several field methods of applying vacuum preloading are also compared. Moreover, the Thermal PVD and Thermal Vacuum PVD can increase further the coefficient of horizontal consolidation, Ch, with the associated reduction of kh/ks values by reducing the drainage retardation effects in the smear zone around the PVD which resulted in faster rates of consolidation and higher magnitudes of settlements. Furthermore, the equivalent smear effect due to non-uniform consolidation is also discussed in addition to the smear due to the mechanical installation of PVDs. In addition, a new kind of reinforced deep mixing method, namely Stiffened Deep Cement Mixing (SDCM) pile is introduced to improve the flexural resistance, improve the field quality control, and prevent unexpected failures of the Deep Cement Mixing (DCM) pile. The SDCM pile consists of DCM pile reinforced with the insertion of precast reinforced concrete (RC) core. The full scale test embankment on soft clay improved by SDCM and DCM piles was also analysed. Numerical simulations using the 3D PLAXIS Foundation finite element software have been done to understand the behavior of SDCM and DCM piles. The simulation results indicated that the surface settlements decreased with increasing lengths of the RC cores, and, at lesser extent, increasing sectional areas of the RC cores in the SDCM piles. In addition, the lateral movements decreased by increasing the lengths (longer than 4 m) and, the sectional areas of the RC cores in the SDCM piles. The results of the numerical simulations closely agreed with the observed data and successfully verified the parameters affecting the performances and behavior of both SDCM and DCM piles.
A major source of electrical energy is thermal power, which results in large quantities of coal ashes. Fly ash, which is produced from the combustion of pulverised coal, has an important place among industrial by-products. Currently, in India, more than 180 Mt of fly ash is being generated annually, posing the dual problem of environmental pollution and difficulty in disposal. This calls for establishing strategies to use the product as an engineered construction
material in geotechnical applications for which the mechanical behaviour of soil–fly-ash mixes is an important consideration. In this study, high-calcium (class C) and low-calcium (class F) fly ashes in different proportions by weight were added to expansive soil to evaluate the effect of fly ashes on the strength behaviour of soil–fly-ash mixtures. Compacted clay–fly-ash samples were cured for 7 and 28 d and subjected to unconfined compression tests. It was found that 20% of class C fly ash is the optimum quantity to improve the characteristics of expansive soil, compared with 60% of class F fly ash. The main objective of the study was to illustrate the beneficial effects of fly ashes on the mechanical behaviour of fly-ash-treated expansive soil.
This paper presents the results of an experimental investigation carried out to evaluate the effect of fly ash (FA) on fine sand compaction and its suitability as a material for embankments. The literature review demonstrates the lack of research on stabilization of sandy material using FA. The study is concerned with the role of FA content in stabilized soil physical characteristics. The main aim of this paper is to determine the optimum quantity of FA content for stabilization of this type of soil. This is achieved through particle size distribution and compaction (standard proctor) tests. The sand was stabilized with three proportions of FA (5%, 10% and 15%) and constant cement content of 3% was used as an activator. For better comparison, the sand was also stabilized by 3% cement only so that the effect of FA could be observed more clearly. The results were in line with the literature for other types of soil, i.e. as the % of FA increases, reduction in maximum dry density and higher optimum moisture content were observed.
Soil stabilization, using a variety of stabilizers, is a common method used by engineers and designers to enhance the properties of soil. The use of nanomaterials for soil stabilization is one of the most active research areas that also encompass a number of disciplines, including civil engineering and construction materials. Soils improved by nanomaterials could provide a novel, smart, and eco-and environment-friendly construction material for sustainability. In this case, carbon nanomaterials (CNMs) have become candidates for numerous applications in civil engineering. The main objective of this paper is to explore improvements in the physical properties of UKM residual soil using small amounts (0.05, 0.075, 0.1, and 0.2%) of nanocarbons, that is, carbon nanotube (multiwall carbon nanotube (MWCNTs)) and carbon nanofibers (CNFs). The parameters investigated in this study include Atterberg's limits, optimum water content, maximum dry density, specific gravity, pH, and hydraulic conductivity. Nanocarbons increased the pH values from 3.93 to 4.16. Furthermore, the hydraulic conductivity values of the stabilized fine-grained soil samples containing MWCNTs decreased from 2.16í µí°¸−µí°¸− 09 m/s to 9.46í µí°¸−µí°¸− 10 m/s and, in the reinforcement sample by CNFs, the hydraulic conductivity value decreased to 7.44í µí°¸−µí°¸− 10 m/s. Small amount of nanocarbons (MWCNTs and CNFs) decreased the optimum moisture content, increased maximum dry density, reduced the plasticity index, and also had a significant effect on its hydraulic conductivity.
Clayey soils in Syria cover a total area of more than 20,000 km2 of the country, most of which are located in the southwestern region. In many places of the country, the clayey soils caused severe damage to infrastructures. Extensive studies have been carried out on the stabilization of clayey soils using lime. Syria is rich in both lime and natural pozzolana. However, few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils. The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils. Natural pozzolana and lime are added to soil within the range of 0%−20% and 0%−8%, respectively. Consistency, compaction, California bearing ratio (CBR) and linear shrinkage properties are particularly investigated. The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent. Analysis results of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) show significant changes in the microstructure of the treated clayey soil. A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.
It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite can be commercially available and effectively used in soil stabilization in road construction. However, the influence and effectiveness of zeolite on the properties of cemented sand systems have not been completely explored. In this study, based on an experimental program, the effects of zeolite on the characteristics of cemented sands are investigated. Stabilizing agent includes Portland cement of type II and zeolite. Results show the improvements of unconfined compressive strength (UCS) and failure properties of cemented sand when the cement is replaced by zeolite at an optimum proportion of 30% after 28 days. The rate of strength improvement is approximately between 20% and 78%. The efficiency of using zeolite increases with the increases in cement amount and porosity. Finally, a power function of void-cement ratio and zeolite content is demonstrated to be an appropriate method to assess UCS of zeolite-cemented mixtures.
The stabilization of soils with additives is a chemical method that can be used to improve soils with weak engineering properties. Although the effects of non-traditional additives on the geotechnical properties of tropical soils has been an subject of investigation in recent years, the effects of magnesium chloride (MgCl2) on the macro- and micro-structural characteristics of peat soil have not been fully studied. This study investigates the effect of MgCl2 on the physico-chemical characteristics of tropical peat. Unconfined compression strength (UCS) tests were performed as an index of soil improvement in treated samples. In addition, the micro-structural characteristics of untreated and treated peat were investigated using various spectroscopic and microscopic techniques such as X-ray Diffractometry (XRD), Energy-Dispersive X-ray Spectrometry (EDAX), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer, Emmett, and Teller (N2-BET) surface area analysis. From an engineering point of view, the results indicated that the strength of MgCl2-stabilized peat improved significantly. The degree of improvement was approximately 6 times stronger than untreated peat, after a 7-day curing period. Additionally, the micro-structural study revealed that the stabilization process led to a few changes in the mineralogical, morphological, and molecular characteristics of the selected peat. The pores of the peat were filled by newly formed crystalline compounds known as magnesium aluminate hydrate (M-A-H).
This paper presents the physical characteristics, index properties, unconfined compressive strength and compressibility characteristics of cement-treated soft Bangkok clay. The cement-treated samples have reduced water contents and the reduction ceased after 30% cement content. The changes in the liquid limit were insignificant while the plastic limit significantly increased. The unconfined compressive strength increased from 15 kPa to 35 kPa with cement content of 10% to 20% for curing time of 28 days. The undrained behavior of cement-treated clays corresponded to 3 zones, namely: Zone I (untreated), Zone II (treated), and Zone III (softening part). Phase transformation was manifested by the abrupt change in the curvature of the stress paths. Higher cement content as much as 10% to 25% was found effective in reducing the compressibility of the clay. For cement-treated clays, the coefficient of consolidation increased by 12 to 19 times with the highest increase at 15% cement content. The reduction of compression index, Cc, reached optimum also at 15% cement content.
There is considerable uncertainty in the determination of effective stress strength parameters of cemented soils from undrained triaxial tests. Large negative excess pore pressures are generated at relatively large strains (typically 4-5% for cemented silty sand) in isotropically consolidated undrained (CIU) tests, which results in gas coming out of solution during shear and significant variability in the measured peak deviator stress. In this study, different failure criteria for weakly cemented sands were evaluated based on the results of CIU and isotropically consolidated drained triaxial compression tests conducted on samples of artificially cemented sand. The use of (A) over bar =0 as a failure criterion eliminates the variability between the undrained tests and also ensures that the mobilized failure strength is not based on the highly variable negative excess pore pressures. In addition, the resulting strains to failure are comparable to the strains to failure for the drained tests. Mohr-Coulomb strength parameters thus estimated from the undrained tests are generally lower than strength parameters obtained from drained tests, and the difference between the failure envelopes from undrained tests increases as the level of cementation increases. This divergence is attributed to differences in the stiffness of the cemented soil under the different loading conditions. The stiffness under undrained loading conditions decreases with increasing cementation due to an increase in the generation of positive excess pore pressure at low strains.
This paper investigates the effect of recycled polyester fiber, produced from polyethylene (PET) bottles, in combination with nano-SiO2 as a new stabilizer to improve the mechanical properties of soils. We intend to study the effect of adding nano-SiO2 and recycled polyester fiber on soil engineering properties, especially the shear strength and unconfined compressive strength (UCS), using clayey soil with low liquid limit. Three different combinations of fiber-soil ratios ranging between 0.1% and 0.5% as well as three different combinations of nano-soil ratios ranging between 0.5% and 1% are used. The shear strength and UCS of treated specimens are obtained from direct shear test and unconfined compression test, respectively. Results of this study show that the addition of recycled polyester fiber and nano-SiO2 increases the strength of soil specimens. Both the shear strength and UCS are improved by increasing the contents of recycled polyester fiber and nano-SiO2 in the soil mixture. The increase in the nano-SiO2 content leads to a reduction in failure strain, but the increase in the content of recycled polyester fiber leads to an increase in failure strain. The increase in the contents of recycled polyester fiber and nano-SiO2 leads to an increase in elastic modulus of soils. Based on the test results, the addition of recycled polyester fiber improves the mechanical properties of soils stabilized with nano-SiO2 as well as the recycled polyester fiber has a positive effect on soil behaviors.
To investigate the soil-pile interactive performance under lateral loads, a set of laboratory model tests was conducted on remoulded test bed of soft clay and medium dense sand. Then, a simplified boundary element analysis had been carried out assuming floating pile. In case of soft clay, it has been observed that lateral loads on piles can initiate the formation of a gap, soil heave and the tension crack in the vicinity of the soil surface and the interface, whereas in medium dense sand, a semi-elliptical depression zone can develop. Comparison of test and boundary element results indicates the accuracy of the solution developed. However, in the boundary element analysis, the possible shear stresses likely to be developed at the interface are ignored in order to simplify the existing complex equations. Moreover, it is unable to capture the influence of base restraint in case of a socketed pile. To bridge up this gap and to study the influence of the initial stress state and interface parameters, a field based case-study of laterally-loaded pile in layered soil with socketed tip is explored and modelled using the finite element method. The results of the model have been verified against known field measurements from a case-study. Parametric studies have been conducted to investigate the influence of the coefficient of lateral earth pressure and the interface strength reduction factor on the results of the model.
In order to improve soft soil strength, a mixture of incinerated sewage sludge ash (SSA) and cement was applied as a soil stabilizer. The intended mix ratio for SSA and cement was 3:1. A-6 clay was selected as the untreated soil. In this study, 15% of clay soil was replaced by SSA/cement to produce the treated soil specimens. Then, four different volumes, namely 0, 1, 2, and 3%, of nano-Al2O3 were mixed with the treated soil as an additive. Tests such as compaction, pH values, Atterberg limits, unconfined compressive strength (UCS), swell potential, California bearing ratio (CBR), and permeability were performed. The results indicate that both UCSs and CBR values of untreated soil were greatly improved by the use of 15% SSA/cement. Moreover, a 1% addition of nano-Al2O3 enhanced the treated soil in terms of both UCS and CBR values. Furthermore, the swell potential was effectively reduced by the use of 15% SSA/cement as compared with untreated soil and the 1% nano-Al2O3 additive fraction offered the best performance. From this study, we conclude that 15% of SSA/cement replacement could effectively stabilize A-6 clay soil, and 1% of nano-Al2O3 additive may be the optimum amount to add to the soil.
Cylindrical specimens of a Devonian Red Marl with various amounts of lime (calcium hydroxide) were prepared and cured in a moist environment at various temperatures (25, 50, 75 degree C) from 1 to 24 weeks. As the gel forms and develops within the cured clay-lime composites, there is a general refinement in pore structure. Mercury porosimetry shows significant changes in pore size distribution within the clay-lime composites as the lime content, curing time, and curing temperature are increased. These changes are shown to be a result of the formation of increasing amounts of cementitious gel. The formation and growth of this gel results in appreciable increases in strength and are accompanied by a general decrease in permeability, although total porosity is in fact found to increase. This is accounted for in terms of a pore blocking mechanism by the developing gel.
The results of the effects of electrolyte type and concentration, nanoparticle concentration, pH, and temperature on the mobility and aqueous stability of polyethylene glycol (PEG)-coated silica nanoparticles are presented. Nanoparticle mobility was evaluated based on the ability to inhibit montmorillonite swelling in aqueous solutions through visual swelling tests, and the results were quantified in terms of the swelling index. The presence of PEG-coated silica nanoparticles was found to have a positive influence on the inhibition of clay swelling only in the presence of electrolytes. Quantification of nanoparticle stability in the presence of montmorillonite particles was achieved using ultraviolet–visible (UV–vis) spectrophotometry. At the highest concentration of montmorillonite dispersion studied, interaction between the dispersed montmorillonite particles and PEG-coated silica nanoparticles resulted in nanoparticle aggregation as indicated by increased turbidity and absorbance readings. Both nanoparticle concentration and montmorillonite dispersion concentration, in addition to the presence and concentration of NaCl, were found to strongly influence the stability of the mixture.
This paper studies the effects of sodium-based alkaline activators and class F fly ash on soil stabilisation. Using the unconfined compressive strength test (UCS), the effectiveness of this binder is compared with that of a common cement-based binder. Influence of the activator/ash ratio, sodium oxide/ash ratio and sodium hydroxide concentration was also analysed. Sodium hydroxide concentrations of 10, 12.5 and 15 molal were used for the alkaline-activated specimens (AA), with activator/ash ratios between 1 and 2.5 and ash percentages of 20, 30 and 40 %, relatively to the total solids (soil + ash). UCS was determined at curing periods of 7, 28, 90 and 365 days, and the most effective mixtures were analysed for mineralogy with XRD. The results showed a clear increase in strength with decreasing activator/ash ratio (up to a maximum of 43.4 MPa), which is a positive result since the activator is the most expensive component in the mixture. Finally, UCS results of the cement and AA samples, at 28 days curing, were very similar. However, AA results proved to be just between 20 and 40 % of the maximum UCS obtained at 1 year curing, while cement results at 28 days are expected to be between 80 and 90 % of its maximum.
This paper presents an experimental study performed on four types of soils mixed with three types of nano-material of different percentages. The expansion and shrinkage tests were conducted to investigate the effect of three type of nano-materials (nano-clay, nano-alumina, and nano-copper) additive on repressing strains in compacted residual soil mixed with different ratios of bentonite (S1 = 0 % bentonite, S2 = 5 % bentonite, S3 = 10 % bentonite, and S4 = 20 % bentonite). The soil specimens were compacted under the condition of maximum dry unit weight and optimum water content (w
opt) using standard compaction test. The physical and mechanical results of the treated samples were determined. The untreated soil values were used as control points for comparison purposes. It was found that with the addition of optimum percentage of nano-material, both the swell strain and shrinkage strain reduced. The results show that nano-material decreases the development of desiccation cracks on the surface of compacted samples without decrease in the hydraulic conductivity.
In this first of a two-part review, this review discusses the potential of graphene to be utilized as a reinforcing filler in cementitious composite to enhance their functional performance. The incorporation of graphene into concrete can address issues such as brittleness, low tensile strength, and permeability. Graphene offers great potential as a concrete additive because of its remarkable features such as efficient heat and electrical conductivity , as well as remarkable strength. Several forms of graphene such as graphene oxide (GO), graphene nanoplatelets (GNPs), and functionalized graphene (FG), have been tested, and all have shown improvements in compressive, flexural, and tensile strengths compared to ordinary Portland cement (OPC). The two-dimensional nature of graphene allows it to have a high specific surface area, making it an attractive construction and building material. The use of graphene in concrete can help lower global CO 2 emissions, making the construction industry more sustainable. The incorporation of a very small quantity of graphene can increase the strength of conventional concrete, reducing the environmental footprint. The article discusses the results of a life cycle assessment (LCA) study, which indicates that making 1 kg of commercial GNPs resulted in lower CO 2 emissions than OPC. The adoption of graphene as a 21st-century material grew extensively in many applications such as computing, energy, medicine, optics, and material science, and now it can be used to improve the concrete's mechanical and durability capabilities.
In this study, the use of glass fiber and cement kiln dust (CKD) as stabilizing agents for a typical silty soil is investigated. Fibers with three lengths (12 mm, 18 mm and 24 mm) were added as percentages of soil’s dry weight (0.3%, 0.6%, 0.9%, and 1.2%), the cement kiln dust (CKD) was added in three percentages by dry weight
of soil (7%, 14% and 21%). The subgrade strength was evaluated in terms of laboratory California bearing ratio (CBR) tests in soaked and unsoaked environment to simulate both dry and inundated conditions for field applications. Chemical and microstructural changes were monitored with Fourier transform infrared spectroscopy (FTIR) and integrated FESEM-EDAX analysis respectively. IITPAVE software was used to compute actual strains on pavement layers and determine the optimum thickness of the pavement sections for untreated and treated subgrade. In comparison to the untreated soil, the overall pavement thickness reduced by approximately 44% when designed on improved subgrade. The cost reduction, using the improved subgrade material was approximately 37.5%. Because the actual strains were significantly lesser than the permissible values, the structural performance of the pavement designed on improved subgrade was enhanced against subgrade rutting and fatigue cracking. The optimum CKD–fiber combination was found to be 14% CKD and 0.6% fiber. The laboratory test results indicated that the proposed ground improvement technique can be effective for subgrade improvement of low-volume roads and also serve as a sustainable disposal solution of CKD.
The scarcity of construction land has pushed the practice of using agricultural land and floodplains as construction zones, which require chemical and mechanical reinforcements for strength enhancement and affect the environment adversely. These reinforcement techniques require excavation and recompaction of the soil at the site. The primary objective of this research is to investigate the application of an in situ form of reinforcement with relatively small carbon footprint than other renovation techniques that can be adopted without excavation in the form of micropiles. An experimental and numerical study was conducted with a square footing on the sand confined by miniature aluminum micropiles. Finite element analysis using ABAQUS was validated from the acquired experimental data, and a parametric study was performed to analyze the effect of the slenderness ratio, depth ratio, proximity ratio, spacing, and inclination of the micropiles. The results obtained from this study reveal that the inclination of micropiles has little effect on the ultimate vertical load. As the slenderness ratio of micropiles is progressively decreased from 40 to 20, the bearing capacity improves by around 27%. Installing micropiles nearer to the footing edge provided approximately 76% improvement with respect to the unreinforced footing.
The conventional soil stabilization methods using additives such as cement and lime are losing scope owing to their nonenvironment-friendly nature. This inspires the use of industrial by-products in soil modifcation for sustainable development.
This paper presents the results of an extensive laboratory investigation on mechanical properties of fber reinforced Karewa
soil stabilized with cement kiln dust (CKD). A total of 11 groups of samples were prepared at four diferent percentages of
glass fber (i.e., 0.3%, 0.6%, 0.9% and 1.2%) and three percentages of CKD (i.e., 7%, 14% and 21%) each by dry unit weight
of soil. For determination of optimum soil–CKD–fber mixes, standard proctor compaction and pH tests were conducted.
The strength improvement was evaluated by performing unconfned compression strength and split tensile strength tests after
curing of 7, 14 and 28 days. The stress–strain patterns of fber reinforced and CKD-treated samples displayed strain hardening
and strain softening characteristics, respectively. The strength test results revealed an improvement of 9.6 times as that of
untreated soil at CKD content of 14% and fber content 0.9%. The technical benefts of combining two ground improvement
techniques (chemical stabilization and fber reinforcement) are evident in the present study. The formation of cementitious
products due to CKD-addition was afrmed through XRD spectroscopy. Microstructural analysis was conducted using feld
emission scanning electron microscopy and an apparent change in pore volume distribution was observed, with both size and
amount of micro and macropores considerably reduced signifying increased number of particle contacts per unit volume.
In this study, several mathematical, soft computing, and machine learning modeling tools are used to develop a dependable model for forecasting the compressive strength of cement mortar modified with metakaolin (MK) additive and predicting the effect of MK and a maximum diameter of the fine aggregate (MDA) on the compressive strength of the mortar. In this regard, 230 datasets were collected from literature with a wide-ranging mix of proportion and curing time. Water to binder ratio (w/b) ranged between 0.36 and 0.6 (by the weight of dry cement), sand to binder ratio 2 to 3, metakaolin content 0–30%, and curing time up to 90 days. Multivariate regression spline (MARS), multiexpression programming (MEP), nonlinear regression (NLR), and artificial neural network (ANN) models were used. Several assessment tools were utilized to quantify the performance of the proposed models, such as coefficient of determination (R2), root mean squared error (RMSE), mean absolute error (MAE), scatter index (SI), and Taylor diagram. Based on the modeling result, the performance of the MARS model is better than MEP, NLR, and ANN models with high R2 and low RMSE and MAE. The MARS, MEP, and ANN excellently predicted the compressive strength based on the scatter index. The parametric analysis of MK and MDA revealed that the ANN model successfully predicted the influence of the mentioned model inputs and optimum MK content for improving long- and short-term compressive strength.
The susceptibility of soil to frost action is a major distress for engineering infrastructure constructed over it in regions that experience seasonal freezing and thawing. The soil deposits which are not otherwise problematic for use as a subgrade/foundation material can become very problematic under seasonal freeze-thaw. Since presence of dissolved salts in pore water depresses the freezing-point and increases the unfrozen water content, it can be ascertained that pore water salinity can affect soil frost susceptibility due to seasonal temperature variations by reducing the total ice content during freezing. An experimental investigation was carried out to assess the effect of pore water solute content on the behaviour of a frost susceptible soil subjected to freeze-thaw cycles in a laboratory test setup as per ASTM D5918-13. The presence of solute primarily depressed the freezing point of the soil. The heave rate, maximum heave and the frost penetration depth was found to decrease with increasing solute concentration in pore water. The effect on the thaw-CBR value, variation in water migration pattern and micro-structural changes along the depth of the sample was also examined. It was found that the presence of solutes negates the undesirable effects during freezing by controlling ice segregation, frost penetration and heaving of the soil which in turn limit the adverse weakening during thawing. The destruction to soil at micro-structural level was also restricted in the samples containing solute in their pore water.
Marble has been widely used as a construction material for many centuries. Due to its wide use, managing of marble wastes has become a pressing issue for authorities as of the environmental threat driven by its increased stockpiles in roadside or abandoned lands. This study investigates a new use of marble waste in weak field soils as subgrade application using additive based stabilization. Raw marble waste was first stabilized with Fly ash based – Portland Pozzolana Cement (PPC) having various PPC content (0.5 to 10%) to investigate the behaviour changes of physical and mechanical characteristics. Then, the modified matrix with cement (1% and 10%) was further stabilized using nano materials of 0.1% reduce Graphene Oxide (rGO) powder by weight in order to enhance the strength properties. The improvements in strengths and mechanisms were characterised using detailed morphological studies to identify new formations of elements, functional groups and microstructure changes during stabilization process. Results showed significant increase of strength in the modified matrix (800% increase of CBR and 3MPa increase of UCS from negligible strength) compared to raw marble waste due to the efficacy of adopted stabilization in the current study. Outcomes revealed that the novel marble matrix derived from this research using wastes and additives does not only indicate great potential in replacing weak subgrade soil which usually is the route problem for many road defects, but also provides an efficient solution for waste management crisis.
Polymer-based nanocomposites due to their advantages such as corrosion resistance, adequate mechanical properties, and low cost are widely used in modern technologies. The increasing application of these nanocomposites, and hence their welding seems unavoidable. In this paper, a novel hot tool in the friction stir welding process is used for butt welding nanocomposite plates of 5 mm thick containing polypropylene, ethylene-propylene-diene monomerand Cloisite 15A. Response surface method is used to design experiments and determine the effect of process parameters such as tool rotational speed, welding speed, tool shoulder temperature, and clay content on weld tensile strength. The results show that although increasing clay content in the base material increases its tensile strength but decreases the weld tensile strength; such that in the specimens with 0, 3, and 6% clay content, the weld tensile strength equals 94, 80, and 61 percent of the respective base materials.
The present study investigated the effect of zinc oxide (ZnO) nanoparticles on the geotechnical properties of lime-stabilized silty clay soil using uniaxial compressive strength, direct shear and Californian bearing ratio tests as well as scanning electron microscopy of the improved microstructure of the specimens. The optimum lime content of 6% increased the strength of the soil specimens. Tests on the specimens cured for 7 days showed that their strength increased with an increase in the soil cohesion and cement bonds. The ultimate strength was recorded at the optimum nano-ZnO content of 1.5. The nano-ZnO acted as a filler in the lime and ZnO-stabilized specimens, causing formation of smaller crystals and increasing reactivity, which increased the strength of the soil specimens. SEM micrographs revealed a more homogenous and finer microstructure with a lower surface porosity with the addition of nano-ZnO.
In this study, the effect of nano-calcium carbonate (nano-CaCO3) as an additive to the cement paste was evaluated and quantified. Microstructure tests, experimental tests, and modeling were conducted to predict the cement paste’s rheological properties namely yield stress (yield point), shear stress limit, viscosity, and stress at the failure of cement at fresh and hardened stages. The cement paste modified with nano-CaCO3 was tested at a water-to-cement ratio of 0.35 with 0.45 and temperatures ranging from 25 to 75 ⁰C. The addition of nano-CaCO3 increased the shear stress limit and the yield stress (so) by
10.28 to 51.35% and 14.36 to 91.4%, based on the nano-CaCO3 content, w/c, and temperature of the test. TGA tests showed that the 1% nano-CaCO3 additive reduces the weight loss of the cement at 800 ⁰C by 76% due to interacting with the nano-CaCO3 with the cement paste. The nonlinear regressions (NLR) model and Artificial Neural Network (ANN) technical approaches were used for the qualifications of the flow of slurry and stress at the failure of the cement paste modified with nano-CaCO3. Based on
the statistical assessments of R and RMSE, the rheological properties such as yield stress, plastic viscosity, shear stress limit and compressive strength of cement paste modified with nano-CaCO3 can be well predicted in terms of w/c, nano-CaCO3 content, temperature, and curing time using two different simulation techniques. Based on the statistical assessments such as coefficient of correlation (R), root mean square
error (RMSE), the NLR model is the most effective model to estimate rheological properties and compressive strength of the cement and it is performing better than the ANN model.
The durability and safety of cement-treated foundation in marine environment has been drawn close attention because many offshore, coastal and marine engineering are under construction in these years. Effect of compound nano-CaCO3 addition on strength development and microstructure of cement-stabilized soil in marine environment was studied in this paper by uniaxial compressive test and micro-structure analysis methods including X-ray Diffraction Analysis (XRD), Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP). Results showed that marine environment had great influence on the strength and durability of cement-stabilized soil and compound nano-CaCO3 addition could effectively improve the compressive strength of cement-stabilized soil at early and late age due to the nucleation and nano-filling function. Furthermore, compound nano-CaCO3 addition was helpful to reduce the corrosion speed and increase the compaction degree of cement-stabilized soil in marine environment.
Various applications of nanocomposites were a good motivation to start a study on this wide spreading field of science. Current research is an investigation on incorporating different percentages of TiO2 nanoparticle as reinforcement to a base material which here is poly methyl methacrylate (PMMA). In this study various percentages of TiO2 (0.5, 1 and 2 wt%) were added to pure PMMA and effect of this combination on the mechanical properties of produced composite by performing several tests was investigated and compared to the base material. For producing samples, materials were compounded by melting compounding method using a twin screw extruder followed by injecting molding process. SEM images showed that almost all percentage of TiO2 nanoparticles have been mixed suitably through base matrix. Rockwell hardness R, impact and tensile tests were carried out on all specimens. Almost all of the results illustrated that combination of TiO2 nanoparticle with PMMA, improves mechanical properties of composite. The results also indicated amazing effect of TiO2 nanoparticles on improvements of impact and flexural strengths. Highest recorded impact strength showed 229% increase in samples containing 2 wt% nanoparticles compared to the base material.
Combinations of cement kiln dust and fly ash were used to develop cementitious material through mechanochemical activation. Mixture combinations made with two different proportions were subjected to various grinding regimes to activate the material. Properties, including particle size distribution, initial time of set, heat of hydration, and compressive strength of the new material were determined. Mechanical grinding resulted in mechanochemical activation of the material, with vibratory grinding more effective than ball mill grinding. Activation was confirmed through X-ray diffraction analysis and no correlation was found between activation and the mean particle size of the material. Although not all the properties of the material tested were comparable to those of portland cement, the results indicate the potential for significant improvement.
The evolution of nanotechnology provides materials with new properties and over the last years a lot of effort has been put to introduce nano-particles into cement pastes in order to improve their properties and to produce materials of better performance. In the present research work, nano-SiO2 produced by pyrolysis and with specific area of 200 m2/g has been added at different percentages (0%, 0.5%, 1%, 2% and 5%) to high-strength cement pastes. These pastes were tested for their mechanical and structural properties at different ages. Nanoparticles act as nuclei for crystallization and large, idiomorphic crystals of Ca–Si composition were formed assisting, up to a certain percentage, in producing materials with dense structure, reduced porosity and improved strength.