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Noncorrosive reinforcement materials facilitate producing structural concrete with seawater and sea sand. This study investigated the properties of seawater and sea sand concrete (SSC), considering the curing age (3, 7, 14, 21, 28, 60, and 150 d) and strength grade (C30, C40, and C60). The compressive behavior of SSC was obtained by compressive tests and digital image correction (DIC) technique. Scanning electron microscope (SEM) and X-ray powder diffraction (XRD) methods were applied to understand the microstructure and hydration products of cement in SSC. Results revealed a 30% decrease in compressive strength for C30 and C40 SSC from 60 to 150 d, and a less than 5% decrease for C60 from 28 to 150 d. DIC results revealed significant cracking and crushing from 80% to 100% of compressive strength. SEM images showed a more compact microstructure in higher strength SSC. XRD patterns identified Friedel’s salt phase due to the chlorides brought by seawater and sea sand. The findings in this study can provide more insights into the microstructure of SSC along with its short- and long-term compressive behavior.

Agricultural solid waste is used in several sectors due to its low cost, lightweight, and enhanced environmental friendliness. The present work aims to study the impact of date seed waste (DSW) on physic-mechanical properties and the firing resistivity of cement pastes (CPs). The Portland cement (PC) is individually added with 2.5, 5, 10, and 15 wt% of DSW. The chemical composition of raw materials was investigated by using FTIR analyses. SEM techniques studied the microstructure of raw materials and hardened CPs. An experimental Taguchi method and an analysis of variance (ANOVA) were employed in this study to evaluate the most optimal and significant conditions of the process. The CPs-mix, which contains 2.5 wt% of DSW (MDS-2.5/A), showed the highest compressive strength values at all ages of hydration compared with other mixes and M0-mix. According to the results of this investigation, DSW showed a negative effect on the water consistency values of CPs at all ages of hydration. It was also observed that hardened DSW-CPs increased significantly with a rising in DWS content up to 15wt% at all curing ages. Particularly in the case of MDS-2.5/A-mixes, the DSW increased the firing resistance of the CPs. Finally, the Taguchi analysis revealed that the best parameters are 2.5 wt% DSW and 28 days of curing time. When it comes to the optimal fire resistance values, it becomes 2.5 wt% of DSW at 250 °C. This study revealed that DSW affects both compressive strength and fire resistance from the technical and economic points of view.

Fly ash-based geopolymer is a crucial application for tackling climate change, limiting the production of greenhouse emissions. The main aim of this study was to determine the effect of the fundamental parameters on compressive strength to ensure a feasible and effective solidification of mine tailings. Three sodium hydroxide (NaOH) molarities (5, 8, and 10 M) and sodium silicate (Na2SiO3) were combined to form the alkaline solution. Four fly ash (FA) proportions (28%, 44%, 54, and 61%) of the dry mix and mine tailings (MT) were utilized as raw materials. This study demonstrated that both 25 °C and 65 °C have a considerable effect on the mechanical properties of geopolymers. The UCS value increased with an increase in NaOH molarity. In addition, the highest Unconfined Compressive Strength (UCS) value was achieved (36.04 MPa) at 10 M. Furthermore, the results also showed that UCS values kept decreasing with the increase of SiO2/Al2O3 and Na2O/SiO2 ratios. The optimal UCS values found were in the range of 0.28–0.38 liquid/solid ratio. It has been concluded that the previously mentioned parameters have a strong influence on the mechanical strength of fly ash-based geopolymer with the new proposed FA proportion.

Excessive accumulation of waste materials has presented a serious environmental problem on a global scale. This has prompted many researchers to utilise agricultural, industrial, and by-product waste materials as the replacement of aggregate in the concrete matrix. In this present study, the prediction and optimisation of coconut shell (CA) content as the replacement of fine aggregate were evaluated based on the mechanical properties of the concrete (M30). Based on the suggested design array from the response surface methodology (RSM) model, experimental tests were carried out to achieve the goal of this study. The collected data was used to develop mathematical predictive equations using both GEP and RSM models. Analysis of variance (ANOVA) was also taken into account to appraise and verify the performance of the proposed models. Based on the results, the optimum content of replacing CA was 50%. In particular, the compressive, tensile, and flexural strength obtained after 28 days of curing were 46.2, 3.74, and 8.06 MPa, respectively, from the RSM model and 46.18, 3.85, and 7.99 MPa, respectively, from the GEP model. The obtained values were superior to those of the control concrete sample (43.12, 3.51 and 7.14 MPa, respectively). Beyond the optimum content, a loss in strength was observed. It was also found that both the GEP and RSM models exhibited high prediction accuracy with strong correlations (R2 = 0.97 and 0.95, respectively). In addition, minimum prediction error (RMSE

Ground improvement by permeation grouting is widely utilized for improving engineering properties of soil. The accurate evaluation of a region improved by grouting is a critical issue to ensure the performance of grouting; nevertheless, current methods to evaluate the area of grouted bulbs under the ground are not well-documented. This study aims to use cross-hole electrical resistivity tomography (CHERT) to evaluate a grouted bulb region by considering the effect of electrode configuration at laboratory scale using a cylindrical container filled with saturated sand. Curing time monitoring was also conducted on grouted bulbs with various recovered Carbon Black (rCB) concentrations. Based on the inverted result, the predicted area of the grouted bulb was addressed, and then the error value between the actual and predicted areas was examined. The results of this study show that CHERT can be employed to assess the location and area of a grouted bulb. Also, it was observed that electrode spacing, damping factor, and curing time had significant influences on the image resolution and error value. Unlike the above-mentioned factors, change of rCB concentration ratio had only a slight effect on the image resolution. Thus, the use of a small amount of rCB as an additive material to enhance the grout strength can also provide a distinct contrast of measured resistivity between the grouted bulb and surrounding soil. In this study, a grouted bulb containing 3% of rCB is recommended based on the test results on strength characteristics. In addition, CHERT measuring can be conducted even in early stages of curing, during which it exhibits a better electrical resistivity contrast between the objective area and the surrounding soil.

Building with earth is an ancient technique which has been the object of numerous studies during the last decade, due to sustainable properties of the material. To improve the mechanical properties and the durability of earthen material, hydraulic binders are usually added (e.g. cement or lime). Other binders with lower carbon footprint are investigated to reduce the environmental impact of stabilised earth material. The present paper investigated a geopolymer-stabilised compacted earth (GSCE). The geopolymer was obtained by using fly ash and an alkaline activator solution (a mixture of Na2SiO3 and NaOH). First, a parametric study was performed to identify the important factors to be investigated. Then, 360 specimens were manufactured and tested under uniaxial compression, to investigate influences of different factors on the compressive strength: Na2SiO3/NaOH ratio (1, 1.5 and 2); the mixing procedure; curing temperature (ambient, 60 and 90 °C) and evolution of compressive strength as a function of time (7, 14, 28, 56, 90 and 180 days). The scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy techniques were applied to investigate the microstructure of GSCE specimens. The geopolymerisation in the specimens was verified by using these techniques. It was shown that the chemical bond C-H (a product of reactions between the activator and CO2 in the air) influenced the evolution of the compressive strength in function of time. The results showed, that after 28 days, the compressive strength of GSCE continued to increase 20–25% until 56 days. The unstabilised and cement-stabilised specimens were also tested and compared with GSCE specimens.

This work aims to study the effects of the curing temperature (40 to 80° C) and the composition of the activating solution (SiO2/Na2O molar ratio of 1 to 1.7) on the process of geopolymerization of fly ash and metakaolin-based matrices. A unique combination of three experimental techniques was used for this purpose: rheology, electrical conductivity, and calorimetry. Correlation among the results indicates that increasing the curing temperature of metakaolin-based mixtures promotes the dissolution of the amorphous phases and therefore favors the formation of the geopolymer phase. However, too rapid dissolution leads to early gelation, which slows down further dissolution and prevents the formation of the geopolymer phase. This explains the existence of a peak compressive strength of about 55 MPa at 60 °C. Mixtures based on fly ash behave differently: increasing the temperature up to 80 °C impacts favorably the dissolution of the vitreous phase and the formation of the geopolymer phase, which results in a continuous increase in the compressive strength up to 57 MPa. Moreover, for both sources of aluminosilicate, it is found that SiO2/Na2O molar ratio of 1.2 provides the suitable alkalinity and the right content of soluble silicate necessary for a good geopolymerization rate.

A comprehensive experimental research was undertaken to investigate the association of undrained shear strength with B-ratio, void ratio, confinement pressure, and principal stress difference at failure of zeolite-lime-treated fine sands. For this purpose, a series of undrained triaxial shearing tests were performed on samples comprising several lime-activated zeolites. With regard to the experimental evidence, a novel trend-adjusted (TA) growth forecast was performed with exponential smoothing to extend curing ages beyond the conditions of the experimental program. Then, hybridization of the artificial neural network (ANN) was done by feeding the network with feature adjusted shear resistance values against void ratio, B-ratio, confining pressure, and binding agents over extension of projected curing period. The proposed TA-ANN model showed a boosted optimization in input selection and high accuracy and confidence rate in predicting undrained shear resistance while including extended curing periods. Finally, results of variable importance and sensitivity analysis indicate a significant impact of underlying degree of saturation to the final shear resistance followed by void ratio, confinement pressure, and zeolite content.

Soil stabilization using nano-additives is one of the trending developments of the decade. Many novel nano-stabilizers were tested by researchers for ground improvement applications. However, the capability of such materials in soil stabilization needs further detailed practical investigations beyond the controlled research environment. On the other hand, many well-proven nano-based stabilizers have constraints like availability, cost, difficulty in implementation method, and the practical feasibility of such usages. Among many well-established additives, nano-silica is one such material that was under research for over a decade and showed promising results for use as a soil stabilizer. Hence, the present work proposes a comprehensive review on characteristics of nano-silica, including its physical nature; its influence on curing methods and ageing, its behavior upon adding with soil and other additive materials in terms of strength improvement, hydraulic conductivity and compressibility; reaction mechanism in various soil and additives and a discussion on the gaps that need to be addressed to transfer this technology to field practices. Literature studies indicate that nano-silica as a sole-additive improved the soil strength and it acted as a strength enhancer for cement, lime and fiber treated soils. Also, nano-silica helps in reducing hydraulic conductivity and compression index of the soil. Further, an analysis on the minimum strength improvement with nano-silica on various types of soils is discussed based on the reported literature. With promising results from the review, further advancements on eco-friendly and cost-effective biogenic production methods would establish nano-silica as a competitive additive in the field of geotechnical engineering.

It has been established that during heat treatment of mixtures of waste activated sludge (WAS) and Fe2O3 under the conditions of oxygen deficiency at 800–1000 °C, reactive carbon, which initiates the reduction of Fe2O3 to Fe and the formation of C–FexOy mixtures, forms. Based on these compacted mixtures, having different electrical resistivity (from ~ 10–4 up to 10–1 Ω·m), it is possible to fabricate heating elements, whose working temperature ranges from ~ 100 °C up to 600 °C. Such heating elements can be used in the construction industry to accelerate the curing of concrete and its low temperature heating.

The optimization of clay soils stabilization was investigated in this work using the application of response surface methodology. The main advantage of the response surface methodology is considered to be the robust structural reliability method to determine the best condition in the geotechnical system. In addition, it will also improve experimental design, strength performance, process efficiency, time management, and cost reduction. This work illustrates the optimum conditions of bacterial calcium carbonate precipitation (BCCP) application which significantly improve clay soils strength. There are four main parameters that need to be considered and evaluated, i.e., types of microorganisms, cementing materials, the molarity of cementing medium, and curing period. Each parameter in BCCP experiments was analyzed to evaluate the most impactful one. The results showed that the optimum condition occurred when using Sporosarcina pasteurii with 0.53 M of eggshell solution (ES) cementing materials and 4.11 days curing period. The unconfined compressive strength at the optimum conditions is 503.52 kPa.

This study aims to assess the long-term efficiency of silica fume used in the production of concrete exposed to sulfate solutions and seawater. The sulfate solutions used in the study were sodium sulfate and magnesium sulfate, and the seawater was provided from Black sea. The experimentation has continued for 4 years. The sulfate ion concentration of the sodium and magnesium sulfate solutions was adjusted to be 1300 ppm, which would be equivalent to the sulfate ion concentration of the seawater used in the test program. The total binder was 350 kg/m3, and cement was replaced by silica fume at a ratio of 10%. The concrete prisms produced were 40 × 40 × 160 mm standard prisms. In order to evaluate the efficiency of silica fume preventing sulfate attack, mass variation along with strength change has been taken into consideration as well as observational evaluation implemented throughout the experimentation. Concrete prisms cured under standard curing conditions were also produced for comparison purposes. Considering the compressive strength, seawater seemed particularly detrimental for concrete that does not contain silica fume. Hence, regarding the compressive strength change of concrete, it is realized that it is worth to take particularly into account the seawater effect in addition to the effect of sulfate solutions. The strength deterioration process of concrete prisms immersed in sodium and magnesium sulfate solutions seemed to be associated with the loss of stiffness and cohesiveness rather than expansion and cracking as opposed to the deterioration observed in case of seawater immersion. Visible cracks were formed in the prisms that did not contain silica fume immersed in seawater.

The present work focused on the durability performance of copper slag (CS) and processed granulated blast furnace slag (PGBS) as a partial replacement (0% to 50%) for natural fine aggregate (NFA) in concrete, cured for 365 days. This work was carried out to determine the ingression of chloride, sulphate, and sodium ions. Compressive strength test and splitting tensile test conducted for the specimens showed that PGBS concrete attained higher strength followed by CS concrete when compared to conventional concrete. The ingression of chloride and sulphate ions decreased in both CS and PGBS concrete after 90 days of curing. Sodium ions ingression also decreased after 180 days of curing. Microstructure studies were carried out using scanning electron microscope (SEM) which showed the dense formation of C–S–H gel in the matrix and high amount of Ca and Si ions in CS and PGBS concrete was observed using energy-dispersive spectroscopy (EDS) analysis. The basic properties like particle size and water absorption of CS and PGBS aggregates have majorly contributed in the reduction in voids in concrete. PGBS concrete has found to be an effective alternative in terms of performance, cost, availability, and environmentally friendly when compared to already exiting CS aggregates and NFA.

Cemented paste backfill system used for the storage of tailings underground also serves as support against subsidence due to roof loads. Therefore, paste backfill materials should be optimized according to strength, environment, and cost requirements. The main purpose of this study is to determine the ratio and optimal particle size distribution of zeolite which is one of the natural pozzolanic materials and can substitute cement in paste backfill. As a result of the experiments without zeolite, it was determined that paste backfill materials with the cement ratio of 9% and 11% can be used for ground support instead of the cemented paste backfill reference samples with 80% solid content. Then, zeolite-substituted samples were prepared in 2 different particle sizes of − 90 μm and − 180 μm at cement ratios of 5%, 10%, 15%, and 20%. Then, the effects of the paste backfill materials on the strength of curing periods of 28, 56, and 90 days were examined. As a result, it was found that 9% cemented paste backfills with 15% zeolite substitutes (− 90 μm) and 11% cemented paste backfills with 10% zeolite substitutes (− 180 μm) could be used in paste backfill. Also, 11% cemented paste backfills with 10% zeolite substitutes (− 180 μm) provide better strength depending on the curing times.

The effects of Na-montmorillonite (Na-Mt) content and curing age on enzyme-induced carbonate precipitation (EICP)-treated soil were studied. First, the effects of Na-Mt addition on the urease activity, Ca2+ precipitation rate, and pH of the solution were analyzed through tube tests. Then, Na-Mt-modified EICP was used to reinforce silty sand in the Yellow River flooding area in China. The solidification effect and action mechanism of Na-Mt were investigated via the unconfined compressive strength (UCS) test, calcium carbonate content (CCC) measurement, X-ray diffraction, and scanning electron microscope analyses, wherein soil treated by conventional EICP and soil treated with Na-Mt alone were considered the control group. Na-Mt improved the urease activity and Ca2+ precipitation rate, lowered the pH, increased the CaCO3 production through chelation, then regulated the morphology of the CaCO3 crystals and facilitated the formation of densely aggregated calcite. The CCC and mechanical parameters increased rapidly during the first 7 days of curing, and then slowed down. The incorporation of 8% Na-Mt enhanced the UCS and Ca2+ utilization ratio at curing age of 7 days by 1.4 and 2.72 times, respectively, compared with that of traditional EICP; and the optimal Na-Mt content was identified to be 8%. At Na-Mt contents lower than 8%, the mathematically expressed improvement effect of the Na-Mt-modified EICP on the soil strength was greater than the arithmetic sum of that when these two approaches applied individually; this result confirms that the Na-Mt-modified EICP technique proposed herein is an efficient approach for solidifying fine-grained soil.

Acid mine drainage presents an important threat to cementitious structures. This study is aimed at investigating the effect of cellulose nanocrystals (CNCs) on the acid resistance of cementitious composites. CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%, 0.4vol%, 1.0vol%, and 1.5vol%. After 28 d of standard curing, the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d. The unconfined compressive strength (UCS) test, the density, water absorption, void volume test, and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion. It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples. Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures. The mixture with 0.4vol% CNC showed a reduced mass change and length change indicating its improved acid resistance.

Paper-based friction materials are porous materials that exhibit anisotropy; they exhibit random pore sizes and quantities during their preparation, thereby rendering the control of their pore structure difficult. Composites with different pore structures are obtained by introducing chemical foaming technology during their preparation to regulate their pore structure and investigate the effect of pore structure on the properties of paper-based friction materials. The results indicate that the skeleton density, total pore area, average pore diameter, and porosity of the materials increase after chemical foaming treatment, showing a more open pore structure. The addition of an organic chemical foaming agent improves the curing degree of the matrix significantly. Consequently, the thermal stability of the materials improves significantly, and the hardness and elastic modulus of the matrix increase by 73.7% and 49.4%, respectively. The dynamic friction coefficient increases and the wear rate is reduced considerably after optimizing the pore structure. The wear rate, in particular, decreases by 47.7% from 2.83 × 10−8 to 1.48 × 10−8 cm3/J as the foaming agent content increases. Most importantly, this study provides an effective method to regulate the pore structure of wet friction materials, which is conducive to achieving the desired tribological properties.

The objective of the investigation was to develop turmeric powder with improved quality using an instant decompression-assisted steam curing (IDASC) process. The IDASC treatment was administered on peeled turmeric slices in the ICPD treatment chamber, which was further followed by hot air drying of the treated slices (IDASC-HAD). The process conditions, namely, treatment pressure (TP), treatment time (TT) and temperature of drying (TD) were optimized for the minimization of hot air drying time (DT) and maximization of the yellowness value (YV) and curcumin content (CC) of the turmeric powder, by the application of an approach which combines the benefits of particle swarm optimization (PSO) with the response surface methodology (RSM). Micro-structure of the IDASC-HAD-treated turmeric slices were observed based on scanning electron microscopy (SEM) image. Turmeric powder obtained by the IDASC-HAD approach was compared with the conventional product for various functional properties. The best quality turmeric powder with DT of 325 min and YV and CC of 60 and 5.05%, respectively, was obtained under the optimum process conditions of the IDASC-HAD process, namely, TP of 3 atm, TT of 50 s and TD of 57 °C. The IDASC-HAD-based turmeric powder samples exhibited higher values of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), total phenolic content (TPC) and total flavonoid content (TFC) as compared to the conventionally produced ones. The improvements in the particle size and micro-structural characteristics were justified from the results of SEM. Turmeric powder produced by the IDASC-HAD method as applied to turmeric slices can be asserted as a product with improved antioxidant properties, which may have application in development of beverages with potential health benefits.

Improving the engineering properties of low-strength soft clay in an environmentally friendly way becomes a challenge in coastal areas. Conventional ground treatment techniques for marine clay using cement can cause significant environmental pollution. In this study, the potential use of industrial waste residue-based binder (IWRB), a silicate-based chemical modified by a powdery polymer, as a substitute for Portland cement (PC) is investigated. Collected marine clay was treated with various IWRB-to-PC ratios (0:8, 4:4, 2:6 and 8:0 wt. %) to measure the mechanical properties, through unconfined compression (UC) test and one-dimensional consolidation (ODC) test, and the microstructural and mineralogical characters, through scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The strength and the deformation of specimens treated with mixed IWRB and PC in a ratio of 1:1 were similar to those improved with PC alone, but the toughness was significantly improved. The microstructural results demonstrated that the cementitious compounds (C–S–H and C–A–S–H) increased significantly in the early curing stage of marine clay treated with IWRB, contributing to the improvement of mechanical properties. It is suggested that IWRB can be an effective substitute for PC to reduce the cost and environmental pollution.

Geopolymer is an environment-friendly cementitious material, which can effectively immobilize heavy metals. However, the existing study on solidification/stabilization (S/S) of heavy metal contaminated soil using geopolymer is very limited. In order to investigate the effects of geopolymer produced by activating fly ash (FA) and ground granulated blast-furnace slag (GGBS) (FA + GGBS) with composite activator of Na2SiO3 and NaOH on environmental and engineering properties of Pb2+ and Cd2+ contaminated soil, a series of tests including soil pH, leachate pH and electrical conductivity (EC), toxicity leaching, UCS and pH-dependent tests were conducted at different curing times. Additionally, scanning electron microscopy/energy dispersive spectroscope (SEM/EDS), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were performed to analyze the micro mechanism of FA + GGBS based geopolymer solidified contaminated soil. The results indicated that the UCS and pH of soil increased steadily with FA + GGBS content and curing time increasing. Moreover, as FA + GGBS content and curing time increased, the leached Pb2+, Cd2+ concentration decreased significantly, and the concentration was closely related to the pH of leachate. Compared with Cd2+, the solidification ratio of FA + GGBS based geopolymer for Pb2+ was lower. Besides, the leached Pb2+ and Cd2+ concentrations decreased first and then increased with increasing pH of extraction fluid. Microscopic analysis showed that the gel products of FA + GGBS based geopolymer were mainly C-(N)-A-S–H gels. However, the geopolymer structure became looser due to the existence of Pb2+ or Cd2+. The formation of Cd(OH)2 was the primary solidification mechanism of Cd2+, while Pb2+ was mainly immobilized in geopolymer structure by ion exchange. The MIP results showed that the volume of inter-aggregate pores between 0.01 and 1 μm reduced with increasing FA + GGBS content of solidified soil.

This study aims to evaluate experimentally the potential of expansive soil stabilization using different additives: zeolitic tuff (ZT), lime, and a combination of lime and ZT. Four different percentages of ZT (10%, 20%, 25%, and 30%), three percentages of lime (2%, 4%, and 6%), and variable percentages of their combinations were used to stabilize the soil for pavement subbase application. Atterberg limits, pH, compaction, linear shrinkage, swelling, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests were performed on treated and untreated soil specimens at different curing times. Results showed that ZT additives effectively reduced the plasticity, linear shrinkage, and swell potential in addition to increase the maximum dry unit weight, UCS, and CBR. The results of this study were supported by a microstructural analysis using scanning electron microscopy (SEM) associated with the energy-dispersive X-ray spectroscopy (SEM/EDX) technique. It was determined that the UCS and CBR values for the 4% lime stabilized soil increased by 22% and 70%, respectively, after the addition of 25% ZT. Based on evaluation of the results, an optimum mixture of 25% ZT and 4% lime stabilized soil can be used in pavement subbase applications as it achieved the minimum strength target.

Sodium chloride (NaCl) is commonly used as a curing/preservative agent for raw hides and skins in tanneries and is removed through a soaking process with total dissolved solids (TDS) and other organic pollutants in effluent, causing significant pollution load to the environment. Hence, the present study evaluated to apply dried neem leaf powder (DNL) as an additive to reduce the usage of salt in skin processing and preservation. To make certain of DNL antimicrobial properties, solvent extracts were performed against proteolytic bacteria isolated from raw skins. Initial characterization of DNL revealed the presence of bioactive compounds nimbolide and dehydro salannol and acetone extract with 16.9-mm, 10-mm and 8-mm zone of inhibition against Salmonella sp., E. coli sp. and Bacillus sp. identified using phenotypic conventional biochemical screening method. Further, skin curing experiments were carried out using four different treatments of DNL (10% 15%, 20% and 25% w/w) along with 15% w/w of conventional salt to obtain an optimum concentration for pilot-scale studies. Thus, the application of optimal DNL (15%) and salt (15%) resulted in no physical changes such as smell and hair slip and was taken for further studies for hydroxyproline activity, pollution load and organoleptic properties along compared with control 40% salt. DNL-aided salt less preservation of freshly flayed goat skins at ambient condition showed no hair slip or putrefaction during the preservation period with significant reduction of TDS (86%) and chloride (71%) in soak liquors compared to conventional salt preservation and enhanced organic load requiring additional treatment. However, the application of the organoleptic, physical and hydrothermal properties of resulting leathers produced from the DNL applied skins was on par with results of leather obtained from conventional salt. Thus, our results demonstrate DNL-aided salt less preservation method is able to reduce the amount of salt for preservation of goat skins significantly, leading to reduced salinity issues during leather processing.

The main objective of this experimental work is to investigate the effect of partial replacement of cement with limestone powder on the permeability of concrete, especially in severe curing conditions. For this evaluation, 5%, 15% and 30% cement of concrete mix design were replaced by limestone powder and two different curing conditions applied to the concrete samples. Some of the concrete specimens were submerged in seawater till the age of the test, whereas others were cured in standard conditions. A series of tests, including the Rapid Chloride Penetration Test (RCPT), water penetration test under pressure, and water absorption test were carried out at ages 7, 28 and 90 days to evaluate the permeability of concrete containing limestone. The results show that the penetration of chloride ion increases with the increase in limestone content in concrete. For seawater conditions, samples with 5% and 15% limestone had less chloride permeability than the control sample. For concrete with 30% limestone powder, the permeability significantly increases for both curing conditions. In the normal conditions, water penetration depth and water absorption increased with the increase in limestone content. This trend was observed for the water penetration depth of samples in seawater, but like RCPT results, the water absorption of samples containing up to 15% had less permeability to the control sample. The compressive strength of all specimens cured in seawater was reduced compared to the standard curing condition.

The investigation aims to check the effect of variation of gypsum and water content on the engineering properties of expansive soil by different experiments, namely, mini compaction test, Atterberg limit’s test, and unconfined compressive strength test along with microstructural analysis. The effect of gypsum (0%, 2%, 4%, 6%, 8%, and 10%), water content (ωopt − 3%, ωopt, and ωopt + 3%), and curing period up to 28 days on the strength of bentonite-gypsum mixtures was highlighted. The results of bentonite-gypsum mixtures showed an increment in maximum dry unit weight and decrement in the optimum water content up to 4% inclusion of gypsum. A gradual reduction in the liquid limit and plastic limit of bentonite-gypsum mixtures was observed with the increase in gypsum content and curing period. The unconfined compressive strength of the bentonite-gypsum mixtures increased continuously with the increase in gypsum content, water content, and curing period. The microstructural behavior of bentonite-gypsum mixtures showed evidence of pozzolanic product formation along with densification of the composite. The multiple regression analysis was also carried out to establish the relationship between the strength and maximum dry unit weight, liquidity index, and the additive content as well as curing period.

The search for new materials to replace Portland cement (PC) has increased due to the high release of carbon dioxide (CO2) and the exploration of raw materials for its production. In this case, supersulfated cement (SSC) appears as an option. SSC consists of up to 90% blast furnace slag and small percentages of calcium sulfate and alkaline activator. This cement has some characteristics similar to PC with the advantage of using less raw material. However, some studies have identified the instability of the ettringite formed in the hydration of SSC although this phenomenon has not been studied in detail in previous research. Therefore, this study aimed to evaluate the behavior of different supersulfated cement compositions, comparing the hydration processes, and identifying the influence of their chemical composition on the instability of ettringite. Microstructural analyses of XRD, TGA, and SEM showed instability of the phases formed from all SSC compositions at 49 days of curing. Mechanical strength and calorimetry analyses showed the best behavior using gypsum as a source of calcium sulfate. Also, the SSC with the highest calcium sulfate content showed lower instability of ettringite and greater compressive strength.

This study seeks to investigate the time and the temperature of the formation of the composites faujasite-geopolymer gels in the reaction medium, and also study the compressive strengths and the microstructural properties of the hardened composites after curing at room temperature. Sodium waterglass from rice husk ash, incandescent and fluorescent bulbs known as low-value silica-rich wastes were used as hardeners for the preparation of the composites at room temperature. The X-ray patterns of the composites using sodium waterglass from incandescent and fluorescent bulbs indicate the reflection peaks of faujasite-Na and the broad hump structure belonging to the geopolymer networks. Whereas the one using sodium waterglass from rice husk ash shows only the broad hump structure. The semi-adiabatic results show that geopolymer gels are formed after 18 min at the temperature of the reaction medium of 38 °C in the composites when sodium waterglass from rice husk ash was used as a hardener. Whereas they are formed after 10 min at the temperature of the reaction medium of 34 and 43 °C in the composites using sodium waterglass from incandescent and fluorescent bulbs, respectively. Zeolite type faujasite-Na is formed after 72 and 40 min at the temperature of the system at 76 and 90 °C in the composites using sodium waterglass from incandescent and fluorescent bulbs, respectively. The increase in the temperature of the reaction medium leads to the crystallization of faujasite. The compressive strengths of the hardened composites using sodium waterglass from rice husk ash is higher (47.54 MPa) compared to those from the incandescent bulb (22.42 MPa) and the fluorescent bulb (12.53 MPa). It was found that faujasite-geopolymer composites could be obtained at non-hydrothermal condition using sodium waterglass from incandescent and fluorescent bulbs. It appears that the formation of faujasite in the structure of geopolymer cements decreases the compressive strength of the composites.

For the resource utilization of the solid waste coking sulfur paste and the improvement of performance of the asphalt mixture, a method for preparing modified asphalt mixture with coking sulfur paste modifier (CSPM) is herein proposed. Compared with the matrix asphalt mixture, the Marshall stability of the 30% CSPM modified asphalt mixture increased by 38.3%, the dynamic stability increased by nearly one time (reaching 1847.5 times/mm), the splitting strength ratio increased by 39.3% while the splitting tensile strength decreased by 11.7%. After curing, the performance of the CSPM modified asphalt mixture was further improved. The results show that CSPM improved the high temperature stability and water damage resistance of the asphalt mixture, and the low-temperature anti-cracking performance of that was slightly reduced. Chemical analysis of asphalt binders shows that a little sulfur reacted with asphalt to produce polysulfide compounds (R-Sx-R′), and a part of sulfur existed in the form of crystalline sulfur which was further increased after curing. The presence of crystalline sulfur as an inorganic filler is the key point for improving the high temperature stability and water resistance performance of modified asphalt mixture.

The shallow spread foundations are one of the widely used foundation types for low-rise, low-cost or commercial buildings. However, it is not possible to use this type of foundation for soils with low bearing capacity or capable of excessive settlements. In these cases, stabilized soil layers overlying insufficient soil may be alternative to the high-cost foundation systems. As the temperature of the soils depends mostly on air temperature for shallow depths, curing conditions of the stabilized soil layers are affected by the air temperature. The effect of curing temperature on the pressure-settlement relation of the layered soil is a gap in the literature. This study investigates the effect of Bayburt tuff on pressure-settlement characteristics of layered soil for various curing temperatures. The specific objectives of this paper are to (1) examine the effect of using the waste tuffs as a stabilization agent in layered soils, (2) evaluate the usability of response surface methodology (RSM) to estimate shear strength parameters (c, ϕ), unconfined compression strength, and secant modulus of the stabilized soil with less experiment, (3) investigate the effect of dimensions of the stabilized soil block (length, with and thickness) on pressure-settlement relations under various curing temperature (T = 3 °C, 13 °C, 23 °C, 33 °C, 43 °C). This study comprises experimental and numerical parts. In the experimental part, strength parameters (c, ϕ) and secant modulus of stabilized soil samples were estimated with response surface methodology for various curing temperatures (3 °C, 23 °C, 43 °C). The effects of curing temperature on shear strength and Bulk’s modulus parameters were determined with the derived RSM model. In the numerical part of the study plate load test was simulated with the derived 2D axisymmetric FE model. The parameters required for the FE analyses were determined with the derived RSM model. As a result of the study, it was seen that it is possible to estimate experimental parameters accurately using the RSM approach with fewer tests. Bayburt tuff and lime mixtures increase the stiffness of the layered soil. The curing temperature has considerable effects on the pressure-settlement relationship up to a certain value. After a certain value increasing curing temperature has no considerable effects on the stiffness of the layered soil.

The main objective of this work is to evaluate the combined effect of two natural pozzolan varieties (black and red) with different grain sizes (fine powder

Long-term material dependency on natural resources has caused a heavy toll on the environment and biodiversity of natural systems. To explore the effectiveness of the usage of unconventional materials in geotechnical applications, an attempt is made towards the application of calcium lignosulphonate, a by-product of the paper industry in soil stabilization techniques in the place of conventional additives such as lime, cement and fly ash. These materials can harm the environment and also increase the carbon footprint due to emissions during their production. The present study focuses on stabilizing a potential expansive soil by using lignosulphonate (LS) in proportions ranging from 0.5% to 3% and 6%. The strength and swell parameters of treated and untreated soil are evaluated under curing periods ranging from 0 to 28 days. The strength aspects of the soil-lignosulphonate composites are evaluated under different moisture states and also after allowing a longer interaction period between LS and soil through the pre-compaction mellowing process. The interaction mechanism is also substantiated with microstructural studies. An average strength improvement of the order of 2 is depicted by the treated soil for an optimum LS content of 1.5%. The treated soil also showed a considerable decrease in swell potential and swell pressure, than untreated soil. The manuscript primarily focuses on the behaviour of LS-amended expansive soil in terms of strength and swelling characteristics and the technique to augment the interaction mechanism of the LS-soil composites.

This article aims to evaluate the mass transport properties in concretes with different contents of polypropylene microfiber (0% and 1%, by concrete volume) and crystalline admixture (0%, 1%, and 3%, by cement mass). Water absorption by immersion, water absorption by capillarity, and air permeability tests were performed to evaluate the properties of mass transport. Images of the microstructure of the concretes were used to support the hypotheses discussed. The tests were performed immediately after curing (28 days) and after curing plus 35 and 70 days of wetting and drying cycles. The combined use of polypropylene microfibers and crystalline admixtures may increase the properties of mass transport at an early age. Nevertheless, the nucleation of hydrated phases around polypropylene microfibers contributed to the densification of the concrete pores over time. The crystalline admixture can close larger pores and reduce connectivity between them in the first ages (first 35 days). However, the effect of crystalline admixtures in filling capillary voids requires more time to occur (around 70 days). The void index was reduced between 0 and 70 days by 47%, 42%, and 44% for reference, F + 1CA, and F + 3CA concrete mixtures, respectively.

Geopolymer concrete is generally composed of alumina–silicate materials combined with alkaline solution. Geopolymer concrete plays a vital role to safeguard the environment by way of eliminating cement in concrete. The agricultural and industrial disposals include rice husk ash and flyash can be used as binding material and it is activated using alkaline solution. Concrete structures usually constitutes significant portion across the nation which include piers, dams, canals and so on. The durability property of concrete is to be addressed properly to ensure the safety of the structure. The current paper investigates the strength and durability characteristics of combined effects of rice husk ash, flyash, GGBS and nano TiO2 geopolymer concrete specimens. Incorporation of GGBS and rice husk ash enhances the concrete properties significantly. Addition of GGBS eliminates the curing of concrete under controlled environment.

Both electrolytic manganese solid waste (EMSW) and phosphogypsum (PG) are solid waste that can cause serious pollution to the environment. Therefore, we try to solidify/stabilize heavy metal ions without adding other curing agents. We found that the Mn2+, Ni2+, Zn2+, Pb2+ and Cd2+ concentrations are 2432.00, 1.47, 3.80, 0.22 and 0.06 mg/L in the EMSW liquid leaching, and 0.26, 2.14, 8.62, 2.79 and 0.57 mg/L in the PG liquid leaching. The optimum conditions for synergistic stabilization/solidification are as follows: The ratio of EMSW to PG is 1:3, the stirring time is 2 h, and the solid–liquid ratio is 1:5. Under these conditions, the Mn2+, Ni2+, Zn2+, Pb2+ and Cd2+ concentrations in leaching liquid were reduced to 599.10, 0.33, 0.56, 0.06 and 0.01 mg/L, and the corresponding curing rates were 75.37%, 77.79%, 85.39%, 72.52% and 77.61%, respectively. When the Ni2+, Zn2+, Cu2+, Pb2+ and Cd2+ concentrations were within the permitted level for the GB8978-1996 test suggested by China’s environmental protection law, the residual manganese content in the leaching liquid of cured EMSW was too high to reach the emission standard. This work indicates that the synergistic stabilization/solidification of heavy metal ions has certain application potential.

The current research evaluated the effect of expansive clay stabilization using a combination of cement (0, 2, 5, 8%) with electric arc furnace slag (EAF) and ladle furnace slag (LF) ranging from 0 to 20% to reduce cement consumption as an environmentally friendly technique. To this end, a set of laboratory tests were conducted on the stabilized and unstabilized samples after 1, 3, 7, and 28 days of curing to evaluate the responses of agents on the clay sample. To evaluate the durability of the samples, they were subjected to 7 freeze–thaw cycles (F-T), so that each cycle lasted 48 h, 24 h for freezing at − 15 °C, and 24 h for thawing at 24 °C. The results show that the swelling of the clay sample can be fully eliminated upon addition of 5% cement and 10% EAF after 7 days of stabilization. Moreover, an improvement in the UCS value of the stabilized samples is observed over the time even for those exposed to F-T cycles, particularly in the cases of LF. Overall, it can be stated that the use of waste materials in soil improvement can play a very important role that needs to be addressed more and more as a suitable alternative to conventional additives.

This paper presents the mechanical behaviour of concrete mixes made with recycled aggregate by replacing the natural aggregate with crushed concrete from pavement demolition. The purpose of this study was to determine the feasibility of using recycled aggregate from pavement demolition to make new concrete for pavement applications. Considering a control mix without recycled aggregate (RCA0) designed for a compressive strength of 34 MPa, two types of concrete mixes with 50% (RCA50) and 100% (RCA100) replacement percentage of natural coarse aggregate by recycled aggregate were made. The resulting concrete specimens were tested at three different curing ages, 7, 14, and 28 days. The results of this study showed that the compressive and flexural strengths decreased for all two mixes as the recycled aggregate content increased, while the density was slightly affected. A new model based on multiple linear regression analysis of the data from this study and other 14 studies from the literature was developed. The model can be used to predict the compressive strength of general-use concrete mixes with recycled aggregate (20–40 MPa) considering both the recycled aggregate content and the curing age of concrete. A good correlation was found between the compressive strength and the two parameters investigated. Given the predictions of this model, it is recommended not to use more than 30% recycled concrete aggregate in the production of new concrete in order not to affect its strength.

Melina wood torrefied at 260 °C for 60 min was agglomerated with lean grade coal fines into composite briquettes using pitch as binder. Torrefied biomass (3%–20%) and coal fines (80%–97%) were blended together to produce the composite briquettes under a hydraulic press (28 MPa). The briquettes were cured at 300 °C. Density, water resistance, drop to fracture, impact resistance, and cold crushing strength were evaluated for the composite briquettes. The proximate, ultimate, and calorific value analyses were carried out according to different ASTM standards. Microstructural studies were carried out using scanning electron microscope and electron probe microanalyzer equipped with energy dispersive x-ray. Fourier Transform Infrared Spectrophotometer (FTIR) was used to obtain the functional groups in the raw materials and briquettes. The density of the composite briquettes ranged from 0.92 to 1.31 g/cm3 after curing. Briquettes with 95%). The highest cold crushing strength of 4 MPa was obtained for briquettes produced from 97% coal fines and 3% torrefied biomass. The highest drop to fracture (54 times/2 m) and impact resistance index (1350) were obtained for the sample produced from 97% coal and 3% torrefied biomass. The fixed and elemental carbons of the briquettes showed a mild improvement compared to the raw coal. The peaks from FTIR spectra for the briquettes shows the presence of aromatic C=C bonds and phenolic OH group. The composite briquettes with up to 20% torrefied biomass can all be useful as fuel for various applications.

It is required for a pavement quality concrete to achieve a flexural strength of 4.5 MPa after 28 days of curing. To open the traffic early before 28 days, it is advisable that such strength is achieved early. Along with this, an additional self-compaction ability would make the construction easier and speedy. Pozzolans are supposed to delay the hydration and give higher long-term strength but high concrete strength could only be achieved with special curing procedures. Possible pavement curing procedures matching site conditions has not been explored. In this paper, we have initially made a plain cement concrete of 28 days compressive strength 70 MPa (equivalent to 7 days flexural strength of 4.5 MPa) and have done trials on this concrete while changing the binder constituents, aggregate proportions as well as application of site curing methods to achieve the same strength with even lesser binder contents. This study utilizes ground granulated blast furnace slag (GGBS), fly ash (FA) and silica fume (SF) for achieving early strength with reduced shrinkage in pavement quality self-compacting concrete (PQSCC) under normal water (23 °C) and hot water (40 °C) for full 24 h, and steam (60 °C) curing for 2 h in 6 h cycle (four cycles in 24 h). CaCl2 was also added @1.5% by weight of binding material. Results indicate that steam curing performs well even without CaCl2 whereas hot water curing has to be complemented with CaCl2 to achieve high strength. It was possible to substitute 60% cement while maintaining high strength (> 40 MPa) after 7 days of steam curing without CaCl2, though highest compressive strength was observed with steam curing of samples containing CaCl2. Special curing is advantageous for all mixes but steam curing highly improves shrinkage resistance of GGBS dominant mixes. New mix design formula which combines high packing density theory and Okamura and Ozawa method was highly effective in complimenting the properties.

Curing temperature has been reported to have significant effect on the early and long-term strength development of cementitious systems such as concrete, mortar, cement-stabilised granular soil, and cement-stabilised clay. For cement-stabilised clays, elevated curing temperature is reported to enhance both early and long-term strength, which is different from that of concrete, mortar, and cemented granular soil. Presently, long-term physio-chemical studies were limited in the literature to fully explain this behaviour. At the same time, sand impurities in clay, which are commonly encountered in the field, have not been considered thoroughly in previous studies. Discussion on methodologies to evaluate temperature sensitivity and its consequence on strength development of cement-stabilised soil is limited. This paper aims to address these knowledge gaps by conducting unconfined compressive and physio-chemical tests on Portland blast furnace cement (CEM III/C) and ordinary Portland cement (CEM I)-stabilised kaolin clay with and without sand impurities cured at different temperatures (cement classification is based on BS EN 197-1 (BSI 2011). It is found that the distinct temperature effects on long-term strength behaviour are mainly attributed to both increased strength-enhancing materials in the cement-soil system and the presence of fine-grained clay particles. A generic method of evaluating temperature sensitivity on cementitious systems with a novel approach to incorporate temperature effect on strength development of cement-stabilised clayey soil is proposed and validated with data obtained from published literature on similar materials.

Peat is an exceptionally problematic soil for construction purposes and is often stabilized by traditional stabilizers (like cement), which emits 0.95-ton carbon dioxide (CO2) per ton of cement during their production. Alkali-activated ground granulated blast furnace slag (GGBS) with its low carbon dioxide (approximately 0.07-ton CO2) emissions and higher strength gain provides a promising substitute to traditional stabilizers. Therefore, this study presents the viability of alkali-activated GGBS-stabilized Indian peat. The three types of peats (sapric, fibric, and hemic) were collected to cover a wide range of variations of fibre (6–73%) and organic content (21–79%). The sodium hydroxide (NaOH) molarities (M) of 6, 9, 12, and 15 were used to activate specimens, with GGBS percentages of 10, 20, and 30% by weight of dry peat and alkali/binder ratios of 0.5, 0.7, and 0.9. The test results show that the UCS of peat-GGBS depends on the molarity of NaOH, A/B, electrical conductivity (EC), pH, curing period, and organic content of the peat-GGBS matrix. The optimum combination for the peat-GGBS blend is 20% GGBS, NaOH molarity of 9, and A/B ratio of 0.7. Furthermore, it was found that UCS increases with the curing period and decreases with organic content (OC). The formation of aluminium silicate, sodium aluminosilicate, and potassium aluminosilicate responsible for strength gain is confirmed by XRD. The FESEM micrographs reveal that these products result in the filling of pore spaces to form a smooth and dense soil-binder matrix.

International audience; This study aims at investigating the lime treatment effect on the changes in microstructure and water retention property of compacted saline soil, with consideration of the aggregate size effect. Two soil powders with different maximum aggregate sizes (Dmax = 0.4 and 5 mm) were prepared and stabilized by 2% lime. The microstructure, total suction and matric suction were determined at various curing times. Results showed that the lime treatment caused a rapid decrease in micro-pores and an increase in macro-pores due to the flocculation of soil particles. During curing, the percentage of micro-pores decreased and that of nano-pores increased slightly. Due to the modification of microstructure, the matric suction increased significantly at 90-day curing. However, the curing time effect on the total suction was insignificant. This was due to the fact that the Ca2+ and Mg2+ in soil pore water and the Ca2+ from hydrated lime were consumed in the precipitations of CaCO3 and Mg(OH)2, cation exchanges and pozzolanic reaction, resulting in a reduction in osmotic suction. Therefore, the increase in total suction was slight, as the increase in matric suction was balanced by the decrease in osmotic suction. The treated specimens with larger aggregates exhibited a larger modal size and thus had a smaller air entry value. The aggregate size effect on the water retention property of total suction and matric suction was found to be insignificant, which could be explained by the similar pore size distribution at micro-pore range and the same soil mineralogy for specimens with different aggregates.

Dispersive soils are susceptible to phenomena of internal and external erosion when in contact with relatively pure water due to its particle’s tendency to deflocculation and suspension. This problem can be addressed through the employment of calcium-based materials such as lime and/or ordinary Portland cement, which are environmental harmful materials. Hence, this paper proposes the stabilization of a dispersive soil through the employment of a binder composed by ground waste glass powder and carbide lime derived from the production of acetylene gas, two residues. Specifically, it evaluates the effect of the dry unit weight, the amount of ground glass powder, the carbide lime content and the curing period on the unconfined compressive strength of compacted soil-ground glass powder-carbide lime blends through a 2k factorial design approach. Moreover, the dispersibility is assessed via Pinhole tests. The strength results could be successfully correlated to the adjusted porosity/binder content index and the statistical analysis revealed the great effect of the controllable variables, with the exception of the amount of carbide lime. The Pinhole tests revealed that the proposed binders suppressed the dispersibility tendency.

Silica or silica-precursor systems are attractive for the protection of wood against biotic and abiotic damages and for improvement of the fire resistance. Alkali metal silicate solutions, also known as water glasses, colloidal silica (nanosilica dispersions) and other inorganic–organic hybrids resulting from the sol-gel chemistry of alkoxysilane compounds, are products available for this purpose. These chemicals are increasingly considered to formulate wood modification products or to develop surface coatings. This review article is focused on in-depth treatments of wood through dipping, soaking or vacuum-pressure impregnation methods. The techniques used to convert monomers and low molecular weight silicate species in water glasses into less soluble and leaching-resistant silica particles, such as heat treatment, acid treatment and reactions with multivalent metal cation salts, are discussed. The similarities and differences between the various raw-impregnation materials and the properties of the final products are highlighted. Water glasses after appropriate curing, colloidal silica and tetraalkoxysilane-based formulations all lead to deposition of silica particles (SiO2) at the surface of the cell walls, in lumens and pores. Low molecular weight organosilanes and other organo-modified formulations that are able to penetrate the wood cell walls and react with wood components are good dimensional stabilizers. The treated wood exhibits, in general, increased mechanical properties (strength, hardness) and improved resistance to biodegradation and fire retardancy. The efficiency of the treatments can significantly be enhanced to a level fulfilling the requirements for industrial applications by the addition of biocides, ultraviolet absorbers or antioxidants, fireproofing compounds (boron or phosphorus-based compounds, multivalent metal salts) and hydrophobic alkylalkoxysilanes. Silica acts as a barrier/support to many of these additives preventing them from leaching.

Global concrete demand is causing depletion of natural resources at an alarming rate. Self-compacting concrete (SCC) is an innovative solution as it uses less aggregates; however, the drawback of SCC is that high cement content is required compared to conventional concrete. Considering that cement production emits 7% of carbon dioxide (CO2) gas emissions, the use of high content of cement in SCC production is concerning. Though the high powder content of SCC may be of a concern, however, it allows the opportunity to substitute the cement content with supplementary cementitious materials. This experimental work was therefore conducted to reduce the cement content by substituting it with waste materials, such as eggshell powder (ESP) and palm oil fuel ash (POFA), and develop an eco-efficient SCC. The cement content was partially substituted by 0 to 5% ESP and 0 to 15% POFA by weight of total binder. A total of 90 cubes of 100 mm and 60 cylinders of 100 × 200 mm dimension were prepared to evaluate the compressive and splitting tensile strengths, modulus of elasticity, and Poisson’s ratio. Furthermore, the environmental impact assessment was conducted to assess the embodied CO2 and eco-strength efficiency of the developed eco-efficient SCC. It was found that the combination of POFA and ESP increased pozzolanic reactivity, developing additional calcium silicate hydrate gels, thus increasing strength. The combination of 2.5% ESP and 5% POFA (a total of 7.5% cement substitution) was deemed to be the optimal combination as it provided better strength in SCC after 28 days of curing, which leads to 9.66% higher compressive strength than the control SCC. Furthermore, the developed SCC was observed to be eco-friendly as it reduced embodied carbon ranging from 3.86 to 15.33% and eco-efficiency ranging from 2.38 to 15.48% on 28 days compared to the control SCC.

It is of great significance to study the soil pore structure for soil reinforcement and ground treatment because it can be used to evaluate the solidification effect and explain the curing mechanism. The pore and compression characteristics of clay from Wuhan in China before and after solidification by ionic soil stabilizer (ISS) in different soil initial states were studied by the use of standard consolidation test, environmental scanning electron microscope analysis, specific surface area (SSA) test, and analysis by PCAS software. Results show that the influence sequence of soil initial states on the change of pore characteristics and ISS-solidification effectiveness was as follows: reducing initial water content + remolding soil > reducing initial water content > remolding soil > natural soil with high initial water content. Besides, loading can also increase the solidification effect. Compared to random and chaotic pore directions of natural clay, remolded solidified clay had a more certain direction after curing and compression. In addition, the total pore number and SSA decreased from 1190 to 756 by 36.47% and 109.690 m2/g to 87.837 m2/g by 19.92% respectively. Results indicate that ISS-clay solidification effect in practical engineering is closely related to the soil initial pre-curing state and can lead to the change of pore direction, decrease of pore number, reduction of pore size and porosity, and formation of larger aggregates.

After ordinary Portland cement (OPC) concrete, geopolymer concrete (GPC) is the most advanced form of concrete. GPC has many advantages including improved strength and durability properties. High early age strength and ambient curing of GPC helps to reduce the construction time. Factors such as binder materials, alkali-activated solution, and curing methods control GPC’s strength properties. Moreover, when industrial byproducts such as fly ash and ground granulated blast-furnace slag (GGBS) are added to GPC, this leads to advantages such as reduced carbon dioxide emission, ability to reuse of waste materials, thus saving valuable lands from getting converted into dump yards, cost reduction, and so on. Moreover, the energy required for the extraction of raw materials is also reduced. In this paper, GPC’s strength and durability characteristics, its mix design procedure, its effect of fibers on mechanical properties, and its structural performance are comprehensively reviewed. Moreover, the development of high-strength GPC using fly ash with sodium hydroxide as an alkaline solution under oven curing condition is highlighted. To develop GPC from different binder materials, trial and error methods are proposed. Rangan’s mix design procedure is used for fly ash-based GPC. Moreover, the inclusion of fibers, it was found, improves the ductile nature of GPC. Suggestions and scope for future GPC-related research are also included.

Environmental threats posed by the cement manufacturing industry and agro-industrial waste discharge have shifted the direction of research towards building sustainable construction without compromising the technical merits of the developed binders. Date palm trees are one of the highest numbers of trees in the world whose generated wastes can be beneficially recycled and reused by the concrete industry. In this study, ordinary Portland cement (OPC) and date palm frond ash (DPFA)-based binders were synthesized by varying ratio of DPFA/(OPC + DPFA) between the range of 0 to 0.3 at an interval of 0.1. Both base materials were characterized by physical, chemical, and thermal techniques. The developed binders were assessed by flow, setting time, and compressive strength up to 360 days of curing. Scanning electron microscopy (SEM) was performed to complement the strength results. It is postulated that the DPFA/(OPC + DPFA) ratio of up to 0.2 outperforms the DPFA-free binder in terms of the overall performance. The properties of binders were negatively affected by the total precursor composition ratio of CaO/SiO2 and Al2O3/SiO2 below 2.06 and 0.18, respectively. The optimum synergy of OPC–DPFA resulted in superior microstructural density attributed to the uniform skeletal framework of gel products. Strengths, weaknesses, opportunities, and threats analysis of the use of DPFA in cementitious materials showed that there is a high potential for its use in terms of sustainability and economic benefits. However, various weaknesses and threats associated with the use of DPFA as a cementitious material need to be resolved.

The present research focuses on the varying proportion of lateritic fine aggregates in High strength concrete (HSC). Concrete mixes of M60 grade were produced by replacing manufactured sand with laterite in the ratio of 25 to 100 percent (by weight), and properties of the mixes are studied. To attain high strength mix, 10% micro silica and 10% of fly ash (FA) were added to all mixes. Mechanical properties were studied after 7, 28, 56, and 90 days of curing, and laterized specimens achieved approximately 12 percent higher compressive strength than control specimens, whereas the split-tensile and flexural strengths increased up to 11.14% and 12.83%, respectively. The results indicated that 25% substitution of laterite was the optimum percentage in HSC concrete. Microstructural studies of optimum mix and reference mix were conducted at 28 days to better morphological and mineralogical understanding of the laterized HSC. Durability parameters such as water penetration depth, chloride ion permeability, and sorptivity exhibited higher values for laterite mixes than the control mixes. The flexural behavior of Reinforced HSC beams using lateritic aggregates was investigated, and the load-carrying capacity of laterized beams was reported to be 11.3 percent higher than control beams. The study results indicate that HSC can be achieved with partial substitution with lateritic fine aggregates and proves that laterite can replace conventional aggregates.

Stabilization of sand by the deep mixing method increases its unconfined compressive strength (UCS) so that it can be used as a foundation for infrastructure. This paper presents research work on physicomechanical properties of soil–cement columns installed in the central area of Vietnam, which consists of sandy clay, fine sand, medium sand, and coarse sand. Two types of cement were mixed with these soils in amounts of 150–350 kg/m3 at a water-cement ratio of 0.6. Approximately 80 soil–cement samples were prepared and cured at standard moist conditions and then tested for unconfined compressive strengths and flexural strengths at 7, 14, 28, and 56 days. The maximum unconfined compressive strength of the soil–cement was 10 MPa after 56-day curing for the coarse sand mixed with 350 kg/m3 cement. The Bayesian Model Averaging and the Principal Component Analysis Methods were used to evaluate the influence of different variables on the UCS of the cement-stabilized soil. The analysis shows that the UCS of the soil–cement depended on the contents of SiO2, SO3, K2O in the soil, the soil grain size, the cement content, and the curing time. The prediction equations allow the determination of unconfined compressive strength and flexural strength of cement-stabilized sand by the wet mixing method used as a ground improvement method for foundations.

Sugarcane bagasse ash is used as a pozzolan in concrete. Although studies on sugarcane bagasse ash blended concrete are available, investigation on the influence of different curing methods in the performance of bagasse ash and marble waste blended concrete is essential. Therefore, the present study focuses on the effect of eight types of curing methods on the strength and durability of bagasse ash and marble waste based concrete. Sugarcane bagasse ash (20 %) and marble waste (25 %) were used at their optimum levels as a pozzolan and fine aggregates in concrete. Compressive strength, water permeability, sorptivity and abrasive resistance of concrete for different curing methods were studied. River sand and crusher sand were used as primary fine aggregate. Strength and durability performance of concrete specimens was comparable for moist curing, jute bag curing and straw curing. Normal water curing is found to be beneficial than other curing methods. Water cured bagasse ash and marble waste blended specimens had higher strength (36 %) and lesser permeability (18.8 %) than ambient cured specimens. Although variations in the abrasive wear are observed in the SCBA and MW blended concrete specimens, it is lesser than the permissible limit of 10 mm.