Unconfined Compressive Strength Research Articles

Experimental study on root-reinforced soils (R2S) and soil root (S-R) interaction in nature

ABSTRACT Biotechnical stabilization, involving vegetation such as trees and shrubs, is commonly employed to reinforce/stabilize soil masses. This research aimed to examine the interaction between soil and roots, focusing on two grass species readily found locally in Kashmir valley: a standard turf grass and a flood channel grass known for its extensive root system. Variables included root length, vegetation type, and root percentage, while strength assessments such as Unconfined Compressive Strength (UCS) tests and Direct Shear Tests (DST) were conducted. Three soils, including two naturally occurring and one artificially prepared in the laboratory, were examined for studies on S-R interaction. UCS values increased considerably for different soil types with the maximum enhancement seen in artificial soil wherein the UCS increased from 65 kPa to almost 400 kPa. Cohesion (c) also showed enhancement from 21 kPa in the control sample to 29 kPa for 1.0% root content and 25 mm root length. Micro-structural analysis was performed and the micrographs clearly showed signs of root surface roughness, adherence of soil particles and interlocking between the grains and root fibers. By stabilizing soil masses, roots can play an important role in slope stability, soil conservation, and other geotechnical applications.

Improving the thermal-mechanical performance of bio-treated backfill materials by addition of magnetic iron oxide nanoparticles (nano-Fe3O4)

The thermal conductivity of backfill materials directly affects the heat transfer efficiency between energy geo-structures and the surrounding stratum. Microbially induced carbonate precipitation (MICP) possesses great potential for improving the thermal conductivity of backfill materials. Magnetic iron oxide nanoparticles (i.e., nano-Fe3O4) have been proven to enhance bacterial biochemical activity by altering the permeability of bacterial biofilms, thus potentially improving the MICP process. It was supposed to enhance the thermal conductivity of backfill materials, allowing for applying energy geo-structures in arid environments. In this study, MICP in a solution environment was conducted to analyze bacterial urease activity and morphology of precipitation at varying nano-Fe3O4 contents. Additionally, sand columns treated with MICP and different nano-Fe3O4 contents were performed to obtain the thermal conductivity and unconfined compressive strength (UCS) through the transient plane source (TPS) method and uniaxial compression (UC) experiment. The mineral type, precipitation morphology, and microstructure were identified using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanism of the effect of nano-Fe3O4 on bacterial urease activity and thermal-mechanical behaviors was also discussed. The results indicated that the nano-Fe3O4 could enhance bacterial urease activity and promote vaterite precipitation in the solution environment. Conversely, when applied to MICP-treated sand, nano-Fe3O4 could facilitate calcite formation. Increasing the nano-Fe3O4 content showed a positive correlation with increased thermal conductivity and UCS. Specifically, the optimal values of thermal conductivity and UCS increased by 2.42 times and 2.39 times, respectively, compared to MICP-treated specimens without nano-Fe3O4. Microstructure analysis revealed that calcite precipitation at the particle contact served a dual function: cementing particles, thereby improving the mechanical strength and simultaneously acting as a "thermal bridge" to enhance the thermal conductivity. Furthermore, this study provides a new perspective on utilizing magnetized bacteria to reinforce specific locations within rocks and soils in the presence of an external magnetic field.

Engineering properties optimization of dispersive soil by calcium silicate waste—The role of steel-making slag

Steel slag (SS) is a byproduct that comes from the production of crude steel in alkaline oxidation furnaces. Resource utilization of steel slag, a calcium-silicon solid waste, is an urgent problem. This paper investigates a solid waste disposal method that applies different steel slag contents to modify dispersive soil. The engineering properties and modification mechanisms of dispersive soil specimens are studied and revealed by performing microstructure, mineral evolution, unconfined compressive strength (UCS), and tensile strength analysis. The pinhole test, mud ball crumb test (BCT), and mud cube crumb test (CCT) were carried out to determine the dispersivity of the soil specimens. Results show that when the steel slag content increases from 1% to 10%, the unconfined compressive strength and tensile strength increase by 176.05% and 75.40%, respectively. For soil specimens without curing time under 50 mm water head, the weight loss of the specimen with 10% steel slag content decreases by 72.03% compared to specimens with 1% steel slag content. Microstructural and mineralogical analyses indicate that the hydration reaction of steel slag changes the ionic composition of the soil and generates reaction products with effects such as filling and connection. To sum up, steel slag effectively improves water stability and mechanical properties of dispersive soil.

Unconfined compressive strength prediction of rock materials based on machine learning

It is costly, time-consuming, and difficult to measure unconfined compressive strength (UCS) using typical laboratory procedures, particularly when dealing with weak, extremely porous, and fractured rock. By efficiently choosing the variables from a subset of the dataset that includes the Schmidt hammer rebound number (SRn), bulk density (BD), bulk tensile strength (BTS), dry density (DD) test, p-wave velocity test (Vp), and point load index test (Is(50)), this study seeks to establish predictive models for the UCS of rocks. A prediction model for UCS was prepared using K-nearest neighbor (KNN). KNN was preferred over machine learning algorithms because it is simple, versatile, and interpretable. It is particularly useful when it has limited training time, faces non-parametric data with changing distributions, or requires straightforward explanations for predictions. In order to improve KNN’s prediction performance in this research, two optimization procedures (namely, Alibaba and the Forty Thieves (AFT) and Improved Manta-Ray Foraging Optimizer (IMRFO)) were used. Through comparison of KNN single modal performance with that of optimized versions, it is concluded that the KNIM (KNN model optimized with IMRFO) is an excellent possible applicant for the forecast of the UCS of rocks. This study’s results showed that the KNIM model is more suitable than the KNN single model and its counterpart KNAF in terms of accuracy as its correlation of determination (R2) values were 1.1% and 2% higher than KNN and KNAF and its root mean squared error (RMSE) values were 37.9% and 43.7% lower than KNN and KNAF. The improvement in R2 and RMSE values for the KNIM model compared to KNN and KNAF is highly significant for the reliability and accuracy of the predictive model. R2, measuring the proportion of variance predictable in the dependent variable (UCS of rocks) from the independent variables (model predictions), signifies a better fit to observed data. The elevated R2 values for KNIM indicate a stronger correlation with actual UCS values, enhancing the model’s accuracy in representing underlying patterns. Additionally, the reduction in RMSE values for KNIM implies that its predictions are, on average, closer to actual UCS values, contributing to a more accurate and reliable estimation of rock strength.

Study on mechanical properties and microstructure of metakaolin-slag-calcium carbide residue synergistic solidifying waste engineering mud

Utilizing MSC composite materials (M-Metakaolin(MK)), S-Slag, C-Calcium carbide residue (CCR)), the waste engineering mud produced through the drilling and grouting pile construction method was solidified.Through the analysis of unconfined compressive strength (UCS), X-ray diffraction (XRD), and scanning electron microscope (SEM) on solidified engineering mud test blocks, the influence of complex factors such as slag content, CCR content, and curing time on the solidification efficiency of engineering mud was investigated, and the microscopic mechanism was analyzed.Concurrently, supplementary tests were carried out to ascertain the pH and water content of the cured mud.The results indicated that the 7-day unconfined compressive strength of cured mud specimens could achieve 3 MPa when incorporating 12 % MK, 8 % slag, and 6 % CCR.The optimal pH for the curing mud is determined to be 11.25, correlating with a water content of 84 %.The destructive strains corresponding to the peak stresses of the cured mud at different curing times ranged from 1.6 % to 2.5 % and generally decreased with increasing peak stresses.The XRD and SEM analyses have demonstrated that the enhancement in the strength of the cured mud can be attributed to the processes of hydration and polymerization, resulting in the generation of gel products such as calcium silicate hydrate (CSH) and aluminosilicate-Na hydrate (NASH). These products are responsible for the adsorption of clay and bentonite particles, thereby efficiently occupying the structural voids.The research findings have the potential to provide theoretical support for the development of environmentally friendly and low-carbon MSC gelling materials, as well as their application in soil reinforcement, notably in the context of engineered mud solidification.

Research on strength and microscopic characteristics of lime-activated fly ash-slag solidified sludge under high temperature effect.

To explore the reaction mechanism of sludge, slag, lime, and fly ash in high temperature environments, the unconfined compressive strength (UCS) test was hereby implemented to study the effect on curing age, curing temperature, slag content and fly ash content about the strength of sludge. Scanning electron microscopy (SEM) was used to observe the microscopic composition of the substance, and X-ray diffraction (XRD) was used to analyze the mineral composition at the micro level to further disclose its reinforcement mechanism. The experimental results demonstrate the difference in the strength measured by different dosage of curing agent, and results indicate that the strength of high temperature curing sample was obviously higher than that of low temperature curing sample. When the curing temperature rises, the pozzolanic reaction and hydration reaction between materials are accelerated, and a certain amount of gel products are produced, playing a precipitation and bonding role between particles. The 28 days and 90 days strengths of the sludge samples with 20% fly ash and 80% slag dosing at 40°C were 1139 KPa and 1194 KPa, which were 1.4 and 1.1 times of that of pure cement solidified sludge. At 60°C, the strength of 14 days, 28 days and 90 days were 802 KPa, 1298 KPa and 1363 KPa, which were 1.1, 1.5 and 1.3 times of that of pure cement solidified sludge. Under the influence of an alkaline environment, the silicon-aluminum grid structure was interconnected into a denser network structure, and the compressive strength of lime-activated fly ash-slag was thus continuously enhanced. Affected by the high temperature, lime-activated fly ash-slag solidified sludge could significantly improve the middle and late strength of the sample. The research showed that the new solidification material can replace partly the concrete curing agent, thereby alleviating the carbon emission and environmental pollution problems arising from cement solidified sludge.

Evaluation of mechanical properties and potential environmental applications of biomimetic mineralized composites

With the growing emphasis on environmental protection, there has been extensive research on new green cementitious materials suitable for different conditions. This study focuses on the influence of key environmental factors on proposed biomimetic mineralized composites (BMC) using polyacrylic acid (PAA) as a modifier, based on the biomimetic chemistry induced carbonate precipitation (BCICP) method. The environmental factors examined include the cementing matrices type, the magnesium ions concentration, and the cementing solution pH. The samples treated under various conditions were evaluated for their unconfined compressive strength (UCS) and calcium carbonate content, and their microstructure was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results demonstrate that the BMC treatment could achieve high-strength cementation for both Toyoura sand and Fujian quartz sand, with a more pronounced enhancement observed for Toyoura sand. Magnesium ions reduce the cementation effect, and they cannot fully replace calcium ions in participating in the cementation process. Moreover, the cementing solution pH significantly influences the cementation effect, with the best acid-base condition for PAA to modify BMC sand samples found at a pH of 11.5. Overall, the BMC exhibits high performance under various environmental conditions. These findings could provide valuable insights into the influence of environmental factors and the potential applications of BMC in diverse environments.

Prediction of axial capacity of corrosion-affected RC columns strengthened with inclusive FRP

The primary cause behind the degradation of reinforced concrete (RC) structures is the propagation of corrosion in the steel-RC structures. Nowadays, numerous retrofitting techniques are available in the construction sector. Fiber-reinforced polymer (FRP) is one of the efficient rehabilitation measures that can be implemented on corroded structures to enhance structural capacities. However, the estimation of axial strength of FRP-strengthened columns affected by corrosion has been a challenging and tedious task in the laboratory as well as on the site. Considering such shortcomings, the prediction of axial capacity can be done using various analytical methods and artificial intelligence (AI) techniques. In this study, a comprehensive dataset of circular columns was extracted from the literature to predict the axial strength of FRP-wrapped and unstrengthened RC corroded columns. The laboratory results from the assembled dataset were compared to corresponding values estimated using relevant design codes provided by American Concrete Institute (ACI 440.2R-17 and ACI 318-19), and Bureau of Indian Standard (IS 456:2000). Five machine learning models were employed on columns to predict the axial load carrying capacity of FRP-strengthened and un-strengthened RC corroded columns. The results discovered that the extreme gradient boosting (XGBoost) model achieves superior accuracy with the least errors and could be used by the scientific community and FRP applicators to forecast the axial performance of corroded columns strengthened with and without FRP. The findings from the design codes revealed that prediction errors were available in high margins. Furthermore, feature importance analysis was conducted using the Shapley Additive exPlanation algorithm to know the contribution and influence of each input parameter on axial capacity. The feature analysis found that unconfined compressive strength of concrete plays an important role in deciding the axial capacity of columns. Moreover, to enhance the precision of axial capacity computation and improving the overall efficacy in engineering practice, a web-based user-friendly interface was developed for FRP applicators and engineers to simplify the process.

Experiment on MICP-solidified calcareous sand with different rubber particle contents and sizes

Microbially induced calcite precipitation (MICP) is a new environmentally friendly technology, with the ability to improve the mechanical properties of calcareous sand. Rubber is a high-compressibility material with a higher damping ratio than that of calcareous sand. In this study, calcareous sand was replaced by equal volume contents (0%, 1%, 3%, 5%, 7%, and 9%) and different sizes (0–1, 1–2, and 2–3 mm) of rubber, and a series of water absorption and unconfined compressive strength (UCS) tests were conducted on MICP-solidified rubber–calcareous sand (MRS). The results showed that the water absorption is reduced when the rubber content is larger. The UCS of 0–1-mm MRS decreased with the increase in rubber content. For 1–2-mm and 2–3-mm MRS, the UCS was improved by 11.30% and 15.69%, respectively, compared with the clean sand. Adding rubber promoted the formation of calcium carbonate, but the strength and stiffness of rubber particles were lower than those of the calcareous sand. Therefore, higher rubber content weakened the sand frame bearing system, and the UCS decreased when the rubber content was more than 5%. Moreover, a large amount of 0–1-mm rubber led to the increase in transverse deformation of the samples, which caused the acceleration of the destruction of the sand structure. The water absorption of 0–1-mm MRS was higher than that of 1–2-mm and 2–3-mm MRS, but the UCS of 0–1-mm MRS was lower. The best rubber size is 1–2 mm and 2–3 mm, and the best rubber content is 3%–5%. The outcome of this study may, in the authors’ view, prove beneficial in improving the strength of calcareous sand when it is reinforced by MICP-combined rubber.

Strength characteristics and mix design of full-depth reclamation of asphalt pavement with cement

The research presents the strength characteristics and theoretical mix design of full-depth reclamation (FDR) with cement for road maintenance and rehabilitation. The reclaimed aggregates used in the study were pulverized and blended on the investigation site by the recycler machine. The FDR mix design covered the reclaimed asphalt pavement (RAP), reclaimed base, and reclaimed subbase courses. The unconfined compressive strength (UCS) was tested on the FDR with cement under different mix proportions, cement content, moisture content, and curing time. Two factors that affect the UCS of FDR, viz., moisture-induced packing density and moisture for cement hydration, were observed. The mix proportion with 40 % RAP required at least 6 % cement to stabilize the FDR for use as a bound base course as per the standard, while the effective limit of cement content for FDR was 9 %. The strength prediction model of FDR with cement was presented theoretically based on the modified soil-moisture/cement ratio concept. The verification of the proposed strength model was performed using 7 and 28-day UCS from another investigation site. The design recommendations for FDR with cement were summarized. This discovery could offer a cost-effective and precise method for the mix design of FDR with cement.

The Effects of Hydroxypropyl Methyl Cellulose and Metakaolin on the Properties of Self-Compacting Solidified Soil Based on Abandoned Slurry.

As a new type of backfill material, Self-compacting solidified soil (SCSS) takes the abandoned slurry of cast-in-place piles after dewatering and reduction as the main raw material, which brings a problem of coordinating the working performance with the mechanical property under the condition of high mobility. In this paper, hydroxypropyl methyl cellulose (HPMC) and metakaolin were introduced as additives to solve this problem. First, the workability and mechanical properties of SCSS were regulated and optimized by means of the water seepage rate test, the flowability test, and the unconfined compressive strength test. Second, this study also used X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the effects of HPMC and metakaolin on the physical phase and microstructure of SCSS. In this way, the results showed that there was a significant impact on the flowability of SCSS, that is, when the dosage reached 0.3%, the water seepage rate of SCSS was reduced to less than 1%, and the compressive strength at 7 days reached its peak. At the same time, HPMC weakened the strength growth of SCSS in the age period of 7 days to 14 days. However, the addition of metakaolin promoted its compressive strength. XRD analysis showed that the additives had no significant effects on the physical phases. And, from the SEM results, it can be seen that although the water-retaining effect of HPMC makes hydration of cement more exhaustive, more ettringite (AFt) can be observed in the microstructure. In addition, it can be observed that the addition of metakaolin can generate more hydrated calcium silicate (C-S-H) due to the strong surface energy possessed by metakaolin. As a result of the above factors, SCSS filled the voids between particles and improved the interface structure between particles, thus enhanced the compressive strength.

Properties and microstructure of soil solidified by titanium slag-flue gas desulfurized gypsum-Portland cement composites as solidifiers

Using Portland cement for soil solidification has sustainability issues due to high energy-consumption and carbon emissions. An innovative approach suggests using titanium slag and flue gas desulfurized gypsum as substitutes for Portland cement for soil solidification. This study systematically evaluates the effects of titanium slag-flue gas desulfurized gypsum-Portland cement composite (TS-FGD-OPC composite) solidifier on the performance of solidified soils. The evaluation includes assessing the unconfined compressive strength (UCS), elastic modulus, moisture content, and leachate pH value. Additionally, the hydration process and microstructure development of the solidified soils are characterized through the XRD, TG-DSC, BET, and SEM tests. The results indicate that the although its compressive strength is much lower, TS-FGD-OPC composite can be used as soil solidifier. With the titanium slag content increase, the TS-FGD-OPC composite solidifier brings the solidified soils to have lower UCS, elastic modulus and leachate pH value, and higher plastic deformation and moisture content. However, to get the same UCS, the utilization of the TS-FGD-OPC composite solidifier can bring the significant reduction of the Portland cement consumption. At the same dosage, the TS-FGD-OPC composite incorporating 50 % titanium slag and 20 % flue gas desulfurized gypsum yields an UCS achieving up to 92.5 % of that in pure Portland cement solidified soil. This is attributed to the filling of pores between soil particles with hydration products and unhydrated particles, resulting in the densification of the solidified soils and the cohesion increase of soil particles. The findings confirm the feasibility of substituting Portland cement with titanium slag and flue gas desulfurized gypsum to prepare an effective and environmentally friendly soil solidifier, to reduce the demand for Portland cement in soil solidification.

Study on the Unconfined Compressive Strength Property and Mechanism of Soda Residue Soil

Study on the Unconfined Compressive Strength Property and Mechanism of Soda Residue Soil

Effect of bone ash and rice husk ash on the unconfined compressive strength of silt soil

This study investigated the soil stabilization potential of ash obtained from the calcination of cattle bones and ash produced by burning rice husks on silty soil. After the cattle bones were first crushed and burned, they were calcined at 800°C for 1 hour, allowed to cool, ground, and sieved with a sieve with a 75-micrometer opening to obtain bone ash (BA). To get rice husk ash (RHA), rice husks were burned, ground, and sieved through a 75-micrometer aperture. A silt soil sample taken from a depth of 3-4 meters from the center of Sakarya Province in Yenigün District of Adapazarı district was used to stabilize it. RHA was added as ground and unground, 10% by weight of the samples, BA as 7% by weight of the samples, and BA and RHA as 7% BA + 10% RHA by weight of the samples. Unconfined compressive strength (UCS) tests were performed for this research. The results showed that the UCS value increased with the addition of BA and RHA as the curing time increased for 7% BA, 7%BA+10% RHA, and 10% ground RHA, while 10% unground RHA lost strength. Caused Therefore, 7%BA+10%RHA can be used to increase the UCS value of the soil. Instead of allowing bones to be disposed of in the environment, calcined bone ash should be encouraged to sustain people's livelihood on stabilized soils.

Enhancing concrete crack healing: Revealing the synergistic impacts of multicomponent microbial repair systems

Small cracks in concrete can develop into larger cracks, reducing the service life of concrete structures. Therefore, the early prevention of fine crack progression is crucial. In this study, a multimicrobial system composed of Bacillus megaterium and Saccharomyces cerevisiae was used to repair concrete cracks, and its repair efficiency was evaluated through fracture healing observations, permeability tests, acoustic time value detection, and unconfined compressive strength tests. Additionally, scanning electron microscopy, energy dispersion spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were used to analyze the concrete repair mechanism of the multicomponent microbial system. The results showed that when the ratio of S. cerevisiae to B. megaterium in the microbial system was 30 %:70 %, the calcium carbonate (CaCO3) yield increased by 10 %, and the mineralization deposition effect was optimal. Under the synergistic action of the two microorganisms, fracture healing proceeded quickly and the pore structure within the fracture became denser, significantly improving the permeability and strength repair rates of the sample and reducing the pulse velocity. For cracks 1.5 mm in width, the permeability and strength repair rates were 63 % and 35.12 %, respectively. The pulse velocity was reduced from 140 µs to 65 µs. The crack filler is mainly composed of CaCO3 crystals 5–10 µm in size, and the total calcium content of the multicomponent repair system was as high as 39.5 %, which was significantly higher than that of the single component repair system (36.1 %). The results indicate that the multicomponent microbial repair system maintains a higher calcium precipitation activity in a high-strength alkaline concrete environment and produces denser CaCO3 deposits, indicating good repair ability. These repair properties improve the overall performance of concrete. This study confirms the strong potential of multimicrobial systems for efficient, cost-effective, and environmentally-friendly concrete crack repair.

Improving Soft Subgrade Stability Using a Novel Sustainable Activated Binder Derived from By-Products

Soft soil concerns, due to high compressibility and low bearing capacity, prompted an investigation into stabilizing clay soil. Traditionally, binder including cement or lime has been used as stabilizers though a current requirement of alternatives is stem from environmental concerns. The study focused on the viability of using a novel binary activated blended binder composed of environmentally friendly materials, namely ground granulated blast furnace slag (GGBS) activated by cement kiln dust (CKD). The experimental work included investigating the impact of the developed binders on the Atterberg limits, standard Proctor compaction, California Bearing Ratio (CBR), unconfined compressive strength (UCS), and field-emission scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy. CBR tests were conducted after 7 days of curing or soaking, while UCS and SEM analyses were conducted after 7 and 28 days of curing. A fixed binder ratio of 9% was maintained, with GGBS blended at 25%, 50%, and 75% with CKD. For comparison, samples of untreated and treated soils with unary binders from GGBS and CKD were also prepared. Results indicated that activated binders notably decreased soil plasticity and maximum dry density, while elevating optimum moisture content, CBR, and UCS, especially in later stages of treated soil and unary GGBS binder. Unary CKD binder exhibited a similar trend to activated binders. The activating of 25% GGBS with 75% CKD provided the optimum binder which increased the mechanical strengths by about 6 times than untreated soil. SEM revealed substantial formations of C-S-H and C-A-H gel, along with ettringite, intensifying with time. This research provides viable outcomes for stabilizing clay soil using environmentally friendly binders, demonstrating significant improvements in soil properties, particularly when using the binary activated blended binder consisting of GGBS and CKD.Graphical

Effect of layered polyethylene terephthalate (Geopet) for reinforcing stabilized sand with fly ash

Purpose This study aims to examine the reuse of plastic and fly ash (FA) to improve the soil and achieve sustainable development goals. Design/methodology/approach Sand from the Anzali port was reinforced with Geopet (GP) and stabilized with FA plus 3% sodium hydroxide. The GP was placed in FA-stabilized soil and the California bearing ratio (CBR), and unconfined compressive strength (UCS) tests were performed on samples at the optimum moisture content. Findings The results showed that the improvement in the optimum CBR was 174.9%. The UCS increased 15.25% and 48.65% in soil reinforced with three layers of GP plus 15% FA over those containing 10% and 5% FA, respectively. Additionally, the current analysis used response surface methodology (RSM) to investigate the impact of FA percentage, GP layers and their interaction on CBR. The results highlight the efficacy of the used RSM model, as evidenced by the significantly low p-value (<0.0001). Originality/value This demonstrates the suitability and effectiveness of RSM for evaluating CBR in this scientific study.

Carbon emissions assessment of cement mixing piles for soft loess improvement and carbon emission reduction using white mud-cement composite material

During the highway construction in the soft loess region of Northwestern China, there are always tens of thousands of cement mixing piles were used. Which generates a large amount of carbon emissions, thereby affecting the environment. The Simplified Energy and Emissions Assessment Model (SEEAM) is used to quantify carbon emissions considering monitoring data of IoT (Internet-of-Things) system. To reduce the error of the carbon emissions of large samples, Monte Carlo simulation was used to quantify carbon emissions based on the small samples. The results showed that cement had a 47,530.78 t carbon missions contributing the 95.64 % of the total carbon emissions. To concurrently ensure strength and reduce carbon emissions, this study investigates the unconfined compressive strength variations in white mud-cement composite material solidified soft loess. It indicated that 10 % and 20 % white mud provided an alkaline environment and nucleation sites for cement hydration reactions, combining the filling voids. According to the observation results of TG and SEM, the content of 10 % white mud increased the quantity of early hydration product CSH in cement. Which maintained a high level of strength by comparing the cement solidified soft loess. In addition, when the white mud content is 50 %, the white mud-cement composite material reduced 576 % carbon emissions in the cement mixing pile engineering. This study can provide guidance for the selection of engineering construction design schemes, as low-carbon emission schemes are conducive to green and sustainable development of the environment.

Sustainable use of recycled glass powder-based geopolymer of organic soil stabilization

The foundation of any structure and construction of roads are most affected by different problems when it is constructed on weak soil such as organic soil for example. The use of recycled glass powder as a precursor in geopolymers improves soil properties (enhancing bearing capacity and reducing compressibility), as well as prevents glass waste from accumulating in landfills. The recycled glass powder (RGP) was added to the soil with different percentages(5,10,15,20 and 25)%. Sodium hydroxide (NaOH) is used as an alkaline solution. The chemical composition of RGP and the organic soil are determined by the X-ray fluorescence (XRF) test. Unconfined compressive strength (UCS) was conducted to investigate the mechanical behavior of specimens. The results show that increase in UCS in 7 and 14 days for the specimens treated with geopolymer compared to the natural soil specimens. The highest UCS value was 7.86 MPa at a curing time of 14 days and a curing temperature of 65C⁰ with 20% RGP.

Monitoring of early curing stage of cemented soil using polymer optical fiber sensors and microscopic observation

Deep cement mixing (DCM) piles are widely utilized for reinforcing soft clay foundations, particularly in coastal regions where soil stability is critical. Monitoring the quality and early-stage behavior of cemented soil is essential to ensure the effectiveness of DCM pile projects in meeting design requirements. Innovative methods for on-site monitoring are necessary to enhance the reliability and efficiency of these reinforcement techniques. In this study, a novel approach is proposed utilizing polymer optical fiber (POF) sensors based on physical optical sensing principles to monitor the initial hydration degree and overall quality of cemented soil during the early curing stage. The proposed method relies on the principle of physical optical sensing, where POF sensors are employed to measure changes in reflected light intensity (LI) and temperature in cemented soil. Two crucial variables, namely the initial water content and the amount of cement, are considered in analyzing their impact on the LI and temperature changes over time. Unconfined compressive strength (UCS) tests and scanning electron microscopy (SEM) analysis are conducted on cemented soil samples with varying water-cement ratios to investigate their mechanical properties and microstructure evolution. The results of the UCS tests indicate that higher initial water content prolongs the initial hydration reaction time required for cemented soil with different cement contents. Analysis of LI curves reveals a rapidly rising trend as the hydration reaction progresses, particularly evident in samples with higher initial water content. SEM analysis further demonstrates that a stable POF LI corresponds to the completion of the hydration process, with hydrated gel formation resulting in a more compact microstructure and smaller voids. The findings highlight the significant influence of cement quantity and initial water content on the mechanical strength and microstructure of cemented soil. By analyzing changes in reflected LI and temperature, the proposed monitoring method provides valuable insights into the early-stage behavior and quality of cemented soil during the curing process. This innovative use of POF sensors for on-site monitoring offers a novel approach to evaluating cemented soil in DCM pile projects.