Improvement In Unconfined Compressive Strength Research Articles

Freeze-thaw durability of clayey soils stabilized by alkaline-activated kaolin and recycled cement kiln dust

Weak soils pose significant challenges for civil engineering projects, particularly in cold regions. Stabilizing such soils with additives is a common practice to enhance their geotechnical properties. This research aimed to evaluate the durability of clayey soils stabilized by alkaline-activated kaolin at 10, 25, and 50%, along with 10% recycled cement kiln dust (CKD). The stabilization process involved curing the soils at different temperatures (40, 60, and 80°C) for varying durations (1, 7, 14, and 28 days). The stabilized soils underwent 5, 10, and 20 freeze-thaw (F-T) cycles to evaluate their durability. The results indicated F-T cycling led to a reduction in the unconfined compressive strength (UCS) of unstabilized soils, with a more pronounced impact as the number of cycles increased. However, this adverse effect was mitigated by additive stabilization. The improvement in UCS in stabilized soils was directly linked to the additive content, curing duration, and temperature. Both additives demonstrated superior resistance to F-T cycles, with CKD outperforming kaolin. These findings provide guidelines for utilizing kaolin and CKD for earthwork applications in cold regions with economic and sustainability advantages.

Combined effect of fiber and degree of stabilization on the early age behavior of cement bound granular mixtures

Abstract An investigation has been undertaken to study the effect of fiber-reinforcement and different degrees of stabilization on the early age mechanical behavior of cement bound granular mixtures intended to be used as a base layer within pavement structure. Waste plastic fibers (WPF) recycled from soft drink bottles were used at 1% by the mass of aggregate to reinforce cemented mixtures. To stabilize different mixtures, cement content of 3%, 5%, and 7% by the mass of aggregate and by the weight of aggregate and fiber were used for conventional and fiber-reinforced cement bound granular mixture (CCBGM& FRCBGM), respectively. The examined properties include unconfined compressive strength (UCS), indirect tensile strength (ITS), bulk density, and ultrasonic pulse velocity (UPV). The results showed a significant improvement in UCS and ITS as the cement amount increased for both types of mixtures. Incorporating PET fibers at cement content of 5% and 7% resulted in a noticeable improvement of ITS compared to the conventional mixtures while a marginal enhancement in the UCS occurred due to fiber-reinforcement. Both bulk density and UPV were increased as cement content increased, while both were decreased due to the inclusion of waste plastic fibers (WPF). Hence, utilizing waste plastic fiber has a positive and promising effect on the pavement structure from sustainability, integrity, and economic points of view.

Comparative study on the effect of SRB and Sporosarcina pasteurii on the MICP cementation and solidification of lead–zinc tailings

The production of tailings sand due to mining and smelting activities is one of the reasons for the accelerated environmental pollution caused by heavy metals, drawing social attention to the management of tailings sand. Microbially induced carbonate precipitation (MICP) is an environmentally friendly soil remediation technique that is gradually becoming the preferred method for soil stabilisation and heavy metal pollution control. To address the issues of heavy metal pollution release and the loose particle structure of lead–zinc tailings sand (LZTS), this study employs a layered MICP approach. The solidification effects of two typical mineralising bacteria, sulfate-reducing bacteria (SRB) and Sporosarcina pasteurii, on LZTS, were compared for the first time. The results show that the maximum unconfined compressive strength (UCS) of SRB cemented solidified lead–zinc tailings sand (SRB-CS-LZTS) specimens is 0.22 MPa, while that of S. pasteurii cemented solidified lead–zinc tailings sand (SP-CS-LZTS) specimens is 0.95 MPa. Compared with the UCS of SRB-CS-LZTS, the UCS of SP-CS-LZTS increased by 3.32 times. The effect of S. pasteurii on the improvement of UCS and immobilisation of heavy metal ions was greater than that of SRB. The immobilisation effect of SRB on SO42- in the LZTS was better than that of S. pasteurii. Compared with SRB, the biological CaCO3 formed by S. pasteurii exhibited stronger adhesion and was more suitable for the cementation and solidification of LZTS. This study uses MICP technology to treat LZTS, aligning with the green environmental concept and providing a reference for the bioremediation of multiple heavy metals in tailing areas.

Embodied Energy in the Production of Guar and Xanthan Biopolymers and Their Cross-Linking Effect in Enhancing the Geotechnical Properties of Cohesive Soil

Traditional soil stabilization techniques, such as cement and lime, are known for their menacing effect on the environment through heavy carbon emissions. Sustainable soil stabilization methods are grabbing attention, and the utilization of biopolymers is surely one among them. Recent studies proved the efficiency of biopolymers in enhancing the geotechnical properties to meet the requirements of the construction industry. The suitability of biopolymer application in different soils is still unexplored, and the carbon footprint analysis (CFA) of biopolymers is crucial in promoting the biopolymers as a promising sustainable soil stabilization method. This study attempts to investigate the out-turn of cross-linked biopolymer on soils exhibiting different plasticity characteristics (Medium & High compressibility) and to determine the Embodied carbon factor (ECF) for the selected biopolymers. Guar (G) and Xanthan (X) biopolymers were cross-linked at different proportions to enhance the geotechnical properties of soils. Atterberg’s limits, Compaction characteristics, and Unconfined Compressive Strength were chosen as performance indicators, and their values were analyzed at different combinations of biopolymers before and after cross-linking. The test results have shown that Atterberg’s limits of the soils increased with the addition of biopolymers, and it is attributed to the formation of hydrogels in the soil matrix. Compaction test results reveal that the Optimum Moisture Content (OMC) of biopolymer-modified soil increased, and Maximum Dry Density (MDD) reduced due to the resistance offered by hydrogel against compaction effort. Soils amended with biopolymers and cured for 14, 28, and 60 days have shown an appreciable improvement in Unconfined Compressive Strength (UCS) results. Microlevel analysis was carried out using SEM (Scanning Electron Microscopy) and FTIR (Fourier-transform infrared spectroscopy) to formulate the mechanism responsible for the alteration in targeted performance indicators due to the cross-linking of biopolymers in the soil. The embodied energy in the production of both Guar and Xanthan biopolymers was calculated, and the obtained ECF values were 0.087 and 1.67, respectively.

Micro- and nano- bentonite to improve the strength of clayey sand as a nano soil-improvement technique

Nano-additives results in the formation of nano-cementation (NC). This process is recently used to improve the durability of various building materials. NC used to improve the strength of untreated soil materials, also known as nano soil-improvement (NSI). In few years, the role of nano-additives in various types of soils were developed. In this research, the role of micro- and nano- size of bentonite as soil stabilizer was evaluated as first few research to improve geotechnical properties of soils. Nano-additives prepared by micro- and nano- sizes of bentonite were blend with four formulations. These formulations of micro- and nano- additives at concentrations of 0, 1, 2, and 3%, namely 0% Micro-Bentonite, 1% Micro-Bentonite, 2% Micro-Bentonite, 3% Micro-Bentonite, 0% Nano-Bentonite, 1% Nano-Bentonite, 2% Nano-Bentonite, and 3% Nano-Bentonite, respectively. These formulations of micro- and nano- additives were separately added to soil. Specimens with 3% nano-bentonite showed significant improvement in unconfined compressive strength (UCS) of soil that was more than 2.3-times higher than control specimen in 7-d curing time. Also the performance of micro-bentonite resulted in improvement in UCS of soil that was more than 1.1-times higher than control specimen at 7-d curing time. The secant modulus at 50% of peak stress (E50) of the samples treated with micro- and nano- additives increased in comparison to untreated specimens. Further, X-ray fluorescence (XRF), scanning electron microscopy, and X-ray diffraction analyses characterized micro- and nano- structures of soil specimens, and showed the performance of nano-additives in improving strength of soils. Results show that nano-bentonite as a type of nano-additives is an effective means of increasing the strength of soils. This research shows the significant of nano-bentonite in soil improvement, as a NSI technique.

Effect of incorporating discarded facial mask fiber on mechanical properties of MICP–treated sand

Responding to environmental challenges associated with the waste generated from discarded facial mask fiber (DFMF), this study introduces an innovative approach to integrate DFMF as a beneficial additive to Microbial-induced calcium carbonate precipitation (MICP) technology - an eco-friendly soil stabilization method. Despite its merit of enhancing soil strength and permeability, MICP often incurs substantial soil brittleness. The incorporation of DFMF, a material conventionally destined for landfill, demonstrates an enhancement in the ductility of MICP–treated sand. Various proportions of DFMF were incorporated (0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% by weight), leading to an observable improvement in unconfined compressive strength (UCS), splitting tensile strength (STS) and in the microstructural configuration of MICP-treated sand. The presence of DFMF fostered bacterial immobilization, catalyzed CaCO3 production, and culminated in an optimum DFMF content at 0.2%. This not only mitigated soil brittleness by introducing ductility via calcite precipitation but also culminated in a “sand particles-fibers-sand particles” spatial configuration, reducing the weakening effect of water on MICP-treated sand samples. This study, therefore, highlights the potential of DFMF as a promising additive in MICP-treated sand, thereby offering an effective method for recycling and reusing discarded facial mask fibers.

Baseline investigation on soil solidification through biocementation using airborne bacteria.

Microbial induced carbonate precipitation (MICP) through the ureolysis metabolic pathway is one of the most studied topics in biocementation due to its high efficiency. Although excellent outcomes have proved the potential of this technique, microorganisms face some obstacles when considering complicated situations in the real field, such as bacterial adaptability and survivability issues. This study made the first attempt to seek solutions to this issue from the air, exploring ureolytic airborne bacteria with resilient features to find a solution to survivability issues. Samples were collected using an air sampler in Sapporo, Hokkaido, a cold region where sampling sites were mostly covered with dense vegetation. After two rounds of screening, 12 out of 57 urease-positive isolates were identified through 16S rRNA gene analysis. Four potentially selected strains were then evaluated in terms of growth pattern and activity changes within a range of temperatures (15°C-35°C). The results from sand solidification tests using two Lederbergia strains with the best performance among the isolates showed an improvement in unconfined compressive strength up to 4-8MPa after treatment, indicating a high MICP efficiency. Overall, this baseline study demonstrated that the air could be an ideal isolation source for ureolytic bacteria and laid a new pathway for MICP applications. More investigations on the performance of airborne bacteria under changeable environments may be required to further examine their survivability and adaptability.

Impact on the Geotechnical Properties of Soil mixed with Terrazyme

The financial sustainability and serviceability of any project after standard performance are the most crucial requirements in emerging nations like India. Hence there is a need to find the best possible ways to satisfy the performance as well as economic criteria. The stabilization of soil with bio-enzyme is a revolutionary technique which becoming popular worldwide. Recently there are many bio-enzymes available for soil stabilization such as Fujibeton, renolith, Perma-Zyme, Terrazyme, etc. These enzymes have been proven to be very effective and economical as well as environment friendly in nature. The efficiency of bio-enzyme depends upon the amount of dosage, types of soil and curing period. One such type of bio-enzyme, Terrazyme has been used in the present work. This study shows the effect of Terrazyme on stabilization of soil. Including the improvement in unconfined compressive strength, shear strength and the Atterberg’s limits. The enzyme treated soil shows significant improvement in strength parameters of soil and little improvement in liquid and plastic limit of the soil.

Assessment of bauxite residue stabilized with lime and graphene oxide as a geomaterial for road applications

Negative traits of bauxite residue (BR) include low shear strength, inconsistent compaction characteristics and dispersion, render it unsuited geomaterial for engineering applications. The present study aims at stabilizing BR with the combination of lime (L) and graphene oxide (GO) in suitable proportions and investigating their impact on improvement in engineering properties (viz., density, unconfined compressive strength (UCS), dispersion, and durability). Lime of 2-10% and GO of 0.05-0.1% dosages (% weight of BR) are selected for experimentation purpose. Results demonstrate that L and GO together, not the individual additive, is effective to stabilize BR. A substantial improvement in UCS from 710 kPa of raw BR to 3890 kPa after treating with 10% L and 0.1% GO with 60 days curing period has been observed. 6% L and 0.05% GO for strength only in the short-term, and 10% L and 0.05% GO in durability aspect in the long-term are found as optimum dosages. Drastic decline in turbidity from 453 to 83 NTU establishes that L (6%) and GO (0.05%) addition completely alleviates dispersion behavior in BR. Though GO addition is trivial, its effect on strength and durability enhancement of BR is significant. Cementitious gel formations and bonding mechanism leading to particle aggregations are evidenced as the reason behind the improvement in strength and durability of BR. To verify the applicability of amended BR, the obtained findings are compared vis-à-vis with standards, which illustrated that the amended BR could be an excellent resource material in road construction, especially in base or sub-base courses.

Resilient Characteristics of Polymer Emulsion-Treated Sandy Soil

The current pavement design guidelines, for example, Mechanistic-Empirical Pavement Design Guide (MEPDG), heavily rely on the resilient moduli of pavement materials. Some locally available pavement materials may not meet the design requirements and often require the application of efficient stabilizers. Therefore, the characterization of natural and treated subgrade soils using resilient modulus is important for the design of durable flexible pavements. A research study was designed and conducted to investigate the effect of polymer emulsion treatment on the resilient characteristics of sandy soil, which is used in constructing highways and airport surfaces. A commercially available polymer emulsion was used to stabilize cohesionless soil, and an attempt was made to understand the influence of polymer emulsion dosage and curing time on the strength and resilient characteristics of treated soil mixtures. Several laboratory tests were conducted on mixtures prepared with different dosages and curing times to evaluate the improvement in unconfined compressive strength and resilient moduli properties of treated sandy soil. Multiple regression analyses were conducted on resilient moduli test results using two- and three-parameter models and identified the best model exhibiting a good fit with the experimental data. A case study was demonstrated using the resilient moduli of untreated and polymer emulsion-treated soil to determine the thickness of airfield pavement. Overall, the outcome of the study is expected to assist the state and federal agencies in stabilizing and using problematic sandy soils for constructing various pavement structures.

Hybrid gradient boosting with meta-heuristic algorithms prediction of unconfined compressive strength of stabilized soil based on initial soil properties, mix design and effective compaction

In the investigation, hybrid Gradient Boosting (GB) with four optimization techniques named Simulated Annealing (SA), Random Restart Hill Climbing (RRHC), Particle Swarm Optimization (PSO) and Evolution Strategy Optimization (ESO) are used to develop machine learning models for predicting unconfined compressive strength (UCS) of stabilized soils based on initial soil properties, mix design and effective compaction. The results show that the hybrid model GB_PSO can successfully predict the UCS of stabilized soils with high performance R2 = 0.9655, RMSE = 0.1633 MPa for testing part. The feature importance analyses are performed with using GB_PSO based Permutation Importance of Sklearn library and Shapley Additive Explanations (SHAP value), which reveal that maximum dry density (MDD), linear shrinkage (LS), and Gravel content are the most important characteristics in the UCS prediction performance of the GB_PSO model. The partial dependence plot (PDP) analysis consisting of PDP 1D and PDP 2D show respectively the impact way of each feature on the UCS and the interactions between initial soil properties, mix design and effective compaction in the UCS improvement of stabilized soil. The PDP analysis show that (i) the LS is the most important criterion in determining the success of improving the UCS of stabilized soil, (ii) the predominance of effective compaction over other conditions on the improvement of UCS. The present investigation can be considered to be new insights for better understanding process of stabilized soil and UCS improvement.

Assessment of alkali-induced heave in soil and its stabilisation using slag

Soil–alkali-interaction results in unexpected heaving and other negative effects of soil properties, which can lead to complete failure of structures. An investigation was carried out on the impact of highly concentrated sodium hydroxide alkali on the heaving behaviour of low-plasticity clay. The effect of ground-granulated blast-furnace slag as a stabiliser for alkali-interacted soil was also investigated. The interaction of alkali with the soil showed heaving up to 5.25% after 30 days, while a slag content of 20% showed maximum suppression of heave. The alkali-interacted soil stabilised with slag was also compared with un-interacted soil mixed with slag. There was a marginal increase in friction angle with an increase in curing period, and a significant increase in cohesion for both. A substantial improvement in unconfined compressive strength was also evident with increased slag content and curing period. The results were supported by microstructural examinations. The application of slag as a liquid-based stabiliser for alkali-interacted soil was also conducted using electrokinetics. Statistical analysis indicated that the curing period was a dominant parameter in affecting the compressive strength of un-interacted soil while, for alkali-interacted soil, slag content was more dominant.

Feasibility of lime and biopolymer treatment for soft clay improvement: a comparative and complementary approach

Highway pavement infrastructure projects which involve soil improvement should be executed, ensuring environmental sustainability. In the present study, guar gum (GG) and lime were assessed for the purpose of soft clay stabilization. The experimental program for the soil stabilization employed a two-stage process. The initial stage involves treatment of the soil with various percentages of lime (3, 5, 7, and 9%) and GG (0.6, 1.0, 1.4, and 1.8%), maintaining the same material acquisition cost and considering curing (0, 7, 14, and 28 days) for the unconfined compressive strength (UCS). In the second experimental stage, a complementary approach in which 3% lime was combined with GG at various percentages (0.1, 0.2, and 0.3%) was employed. The tests conducted include UCS, California bearing ratio (CBR), and strength loss resistance (SLR). Results show that the sole use of lime and GG resulted in significant improvement in the UCS, albeit lime was better. While UCS improved with curing time for the lime-stabilized soil, UCS gain for GG occurred only for up to 7 days curing because biodegradation of GG by microbes in the soil ensues on further curing. Lime-GG stabilization resulted in better UCS and CBR improvement with curing than lime stabilization; however, lime stabilization yielded better SLR. The optimum additive content for strength improvement was obtained at 3% lime + 0.3% GG. Microstructural analysis indicated cementation in the stabilized soil. Predictive models for the UCS were developed based on regression methods. Model evaluation revealed that Gaussian process model provided the best UCS prediction.

Improvement of Unconfined Compressive Strength of Soft Clay using Microbial Calcite Precipitates

The precipitation of calcite induced via microorganisms (MICP) is a technique that has been developed as an innovative sustainable ground improvement method utilizing ureolytic bacteria to soil strengthening and stabilization. Locally isolated Bacillus Sonorensis from Iraqi soil samples were found to have high abilities in producing urease. This study aims to use the MICP technique in improving the undrained shear strength of soft clay soil using two native urease producing bacteria that help in the precipitation of calcite to increase the cementation between soil particles. Three concentrations of each of the locally prepared Bacillus sonorensis are used in this study for cementation reagent (0.25M, 0.5M, and 1M) during the period of treatment. The results showed that the native isolated bacteria have high activity in bindings the soil particles together. The results of unconfined compressive strength tests showed that using MICP helps increase the undrained shear strength of soil by (3-5 times) for C11 types of native isolates, but the D11 was (1.5-2 times) because two types have different activity. This study's main finding is using the native urease-producing bacteria isolated from Iraqi soil in the MICP technique for the biocementation of soil, which is considered one of the sustainable techniques in the construction industry.

Chemical Treatment of a Highly Expansive Clay Using a Liquid Ionic Soil Stabilizer

Expansive soils for residential projects are often treated with liquid ionic soil stabilizer (LISS) using deep pressurized injection method. Liquid ionic soil stabilizers have a long history of application in practice. However, there is limited knowledge and experimental evidence of their stabilization mechanism and effectiveness. This paper summarizes the research that investigated the effects of liquid ionic stabilizers on key engineering properties of a highly expansive clay from Carrollton, Texas, through comprehensive physical and mechanical testing and microscopic observation of untreated and treated soils. Test results before and after treatment were analyzed for two different treatment ratios: 1:300 and 1:150, showing a 53% swell reduction for treated soil compacted at the optimum moisture content (OMC) for treated soil, and 25% swell reduction for treated soil compacted at the OMC for the untreated soil. There was no significant improvement in unconfined compressive strength; noticeable improvement in stiffness was observed. The microscopic analysis showed a marked change in morphology and quantitative element composition, thus suggesting the occurrence of a reasonable degree of stabilization.

Enhancement of geotechnical properties of municipal sewage sludge for sustainable utilization as engineering construction material

Abstract The present study demonstrates potential utilization of lime-stabilized sewage sludge (SS) for construction purposes. SS samples were constituted using 0, 2, 4, 6 and 8% of lime by weight of the SS and cured for 7, 14 and 28 d. Stability of the lime-modified SS was evaluated through determination of geotechnical, microstructural and mineralogical properties. A large improvement in unconfined compressive strength (UCS) from 207 kPa to 1102 kPa was achieved after 28 d of curing SS with 6% lime. The improvement in UCS is attributed to formation of cementing compounds as a result of pozzolanic reactions. Marked reductions in swell pressure of 47, 51, 54 and 58% were obtained with the 2, 4, 6 and 8% lime treatments. Also, the plasticity index decreased with increasing lime content for different curing periods, indicating the SS becomes much more workable and less expansive. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) after lime treatment confirmed formation of the new compounds responsible for the improved engineering properties of SS. The study concludes that lime treatment can be an alternative to stabilize SS for potential use as a construction material for subbase of flexible pavement as per IRC (Indian Road Congress) 37–2012 guidelines.

Energy Absorption, Secant Modulus and Compressive Strength of Fiber Reinforced High Fly Ash Content Cement Treated Soil

This paper presents the results of an experimental investigation that was conducted to study the behavior of fiber-reinforced, high fly ash content and cement treated soil specimens under unconfined compression tests. The effect of fiber inclusions, curing time and fly ash-cement (FA/C) ratio on unconfined compressive strength (UCS), energy absorption (EA), secant modulus of elasticity (ES) and brittleness index (IB) have been studied. Fly ash of 50% and 70%, and cement content of 1.5% and 2% by weight of soil were used in this study. The fly ash and cement as a cementing agent played a significant role in increasing the compressive strength. The unreinforced mix specimens showed a significant improvement in UCS. The fiber inclusions further increased the compressive strength and improved the ductility of the mix specimens. The increase in fiber inclusion was observed to have an increasing effect on UCS, energy absorption, and secant modulus. The increase in curing period (0, 7, 14 and 28 days) also had similar effect on UCS, EA, and ES. However, the increase in fiber content decreased the brittleness index whereas the increase in FA/C ratio increased the brittleness index of the mix specimens. The study suggests a viable method for improving UCS and reduce brittleness of the soil media which may be beneficial for subgrade stabilization.

Experimental Investigation on Strength and Bearing Capacity Improvement of a High Plasticity Clayey Subgrade Soil Using Lime

Limited connectivity and poor infrastructure of roads acts as a roadblocks hampering the socio-economic development of one region. In order to overall development of these regions an effort should be given to cultivate well established road network. But due to scarcity of good quality soil PWD engineers are often forced to build roads over the weak soil which directly affects the strength and durability of the road. It is therefore essential to improve the engineering properties of such problematic soil with suitable stabilization technique as and when encountered. Lime stabilization is one such well known chemical stabilization technique extensively used to improve the poor subgrade condition and it is recommended by several codes in INDIA. This paper attempts to study the effect of lime on strength and bearing capacity improvement of soft clayey soil. A series of UCS and CBR tests are conducted with different percentages of lime (i.e. 3, 5, 7 and 9%) and at different curing period to assess the potential of lime in strength improvement. Test results indicate that strength, stiffness and bearing capacity of the soil is considerably improved after lime amendment. Both unconfined compressive strength (UCS) and California bearing ration (CBR) improved up to 7% of lime beyond that it decreases. The improvement of UCS and CBR is found approx three and five fold as compared to original soil. Underlying mechanisms of this improvement is further scrutinized by microstructural analysis such as X-ray diffraction (XRD), Field Emission scanning electron microscope (FESEM) with Energy dispersive X-Ray Analysis (EDAX). Apparent formation of some new peaks in XRD analysis and change of textural and structural morphology of clayey soils obtained from FESEM confirms the formation of cementitious compounds in the lime stabilized soil.

Improving Road Construction on Sabkha Soil by Using Lime Stabilization and Groundwater Table Monitoring

Abstract This research focuses on the possibility of using hydrated lime as an agent to enhance the properties of sabkha soil, such as maximum dry density, optimum water content, liquid limit, plasticity index, maximum strength, and compressibility. A series of laboratory tests was conducted on selected soil treated with 0, 3, 6, 9 and 12 % of lime by weight of dry sabkha soil. It was found that the addition of lime to a soil generally results in a reduction of moisture content with reference to compaction and strength, and it leads to an improvement in unconfined compressive strength by the percentage of lime added when compared to the untreated mix. It was found that the addition of the lime to a soil generally results in different decreases in settlement and to different increases in maximum dry density and strength. It was observed that values for consolidation tests indicate that a minimal reduction in void ratio points to failure or collapse not being produced as expected. However, the reduction in void ratio, regardless of its amount, increases with an increase of sustained pressure, and it can be concluded that the sabkha soil possesses low compressibility despite its high salt content. Moreover, the concern of failure upon the coverage of a sabkha area by water, rather than the compressibility of sabkha, must be of main consideration in road construction. Therefore, anticipation of the need for water drainage is necessary to avoid such failure.

Assessment of the Load–Deformation Behaviour of Rubber Fibre–Reinforced Cemented Clayey Soil

The utilisation of end-of-life tires nowadays has become a matter of great distress across the globe when left unattended. These tires have been proved to be a malady on the environment causing severe pollution and health hazards. Hence, the potential use of end-of-life tires has been crucial, especially due to the uncontrolled population rise in urban areas which demands construction on undesirable soil. This paper examines the load–deformation behaviour of rubber fibre–reinforced cemented clayey soil through laboratory tests such as unconfined compressive strength (UCS) and split tensile strength (STS) tests. The clayey soil was stabilised with 3 and 6% cement content, and the inclusion level of rubber fibres was kept at 0, 2.5, 5, 7.5 and 10%. A total of 360 specimens, 180 specimens each for the UCS and STS tests, were prepared in accordance with their optimum moisture content and maximum dry unit weight and cured for 7, 14 and 28 days. The study revealed that adding rubber fibres (up to 2.5%) to clayey soil leads to marginal improvement in UCS and STS. Note that by inclusion of rubber fibres to cemented clayey soil causes a decrease of UCS and STS. Maximum increase of absolute toughness and toughness index of cemented clayey soil was observed with the addition of 7.5% rubber fibres. Test results showed that inspite of the decrease in UCS and STS of cemented clayey soil with the augmentation of rubber fibre content, there were decreases in initial stiffness and improvements on ductility and hardening in the post-peak region. From this study, it could be concluded that rubber fibres up to 7.5% can be incorporated in the cemented clayey soil.