Rice Husk Ash Dosage Research Articles

Exploring sustainable solutions for soil stabilization through explainable Gaussian process-assisted multi-objective optimization

The adoption of sustainable solutions in soil stabilization has piqued the interest of the scientific community due to the potential reduction in carbon footprint. In this regard, the research community has started looking for the alternate sustainable solutions to limit the quantity of conventionally used ecologically unfriendly soil stabilizers like lime and cement by utilizing the agricultural and industrial by-products. The production of conventional soil stabilizers (lime and cement) is extremely energy-intensive and contributes tons of greenhouse gases to the atmosphere. In general, evaluating suitability of these additives requires in-lab investigation of soil samples with varying additive concentrations and curing periods, making this approach both resource and time-intensive. Hence, this article proposes a computational framework for accelerated characterization of soil-stabilization by using the coupled experimental-Gaussian process (GP) based machine learning (ML) model. The dataset utilized for constructing the GP models consists of input features such as the stabilizer content (lime and rice husk ash (RHA)), coir fiber content, and curing period (measured in days). The target responses are the strength measures of the stabilized soil, such as unconfined compressive strength (UCS), split tensile strength (STS), and California bearing ratio (CBR). The proposed computational framework is deployed to perform multi-objective genetic algorithm (MOGA)-based optimization to achieve maximum engineering performance from stabilized soil. The presented study demonstrated that with the optimal dosage of rice husk ash (agricultural by-product), and cashew nut shell liquid (CNSL) treated coir fiber, the requirement for lime dosage may be significantly reduced while maintaining the engineering performance of the soil. The presented computational framework can be extended to any construction practices for ensuring the strategic selection of the control variables for optimizing the desired performance.

Strength Performance of Concrete Containing Rice Husk Ash as Cement Replacement in Presence of Polypropylene Fiber

This study focuses on the utilization of Rice Husk Ash (RHA) as partial replacement of Ordinary Portland Cement (OPC) in concrete in addition with Polypropylene (PP) fiber. The main goal of this study was to decrease dependence on OPC and address environmental waste generated through rice mills. This study considered concrete cubes prepared through 1:2:4 ration with 0.50 water-cement ratio with and without RHA and PP fibers. The water curing was done for 7 and 28 days, with three specimens for each proportion, and the average value was considered as the result. It was observed that the compressive strength of M2 concrete which containing 10% RHA was noticed 7% higher than the control mix concrete and declared as 10% RHA as optimum dosage. Next, the performance in terms of compressive strength of concrete containing optimum dosage of RHA in presence of PP fibers of three different lengths were also evaluated and found that the 0.1% of PP fiber of 0.5 inches length gives the 25% higher strength performance as compared to the control mix and 17% higher than the concrete containing 10% RHA only at the age of 28days. Hence, this study concluded that the replacing OPC cement with 10% RHA produces satisfactory strength performance and incorporation of PP fiber gives better strength performances.

Influence of rice husk ash on the mechanical properties of ultra-high strength engineered cementitious composites (UHS-ECC).

Generally, UHS-ECC should consume massive cement, which is negative to its sustainability as cement production leads to 8% of global CO2 emissions. To decrease the cost of production and carbon emissions of UHS-ECC, rice husk ash was employed to replace the cement as a supplementary cementitious material in this study. Experiment results illustrate that blending rice husk ash (RHA) would decrease the fluidity of mortar. Furthermore, the green UHS-ECC shows a maximum compressive strength of 130.3 MPa at 28 days when RHA content was 20% of cement. The ultimate tensile strength of UHS-ECCs first increased and then decreased, while both tensile strain and strain energy presented an opposite tendency. At the micro-scale, if RHA content was lower than 20% of cement, incorporating RHA can significantly decreasing fiber bridging complementary energy of UHS-ECC, thus reducing pseudo strain hardening energy (PSHenergy) index, which finely agrees with the degradation of ductility of UHS-ECCs. To guarantee the features of ultra-high strength, acceptable workability, and high tensile ductility, the RHA dosage should not be in excess 20% of cement. These researched results are prospected to the contribution of pozzolanic RHA on the efficient usage of sustainable UHS-ECC.

Mechanical properties evolution of clays treated with rice husk ash subjected to freezing-thawing cycles

Rapidly growing urbanization and industrialization drive the continued development of soil stabilization and ground improvement techniques. Rice husk ash (RHA) is widely regarded as a highly promising construction material in civil engineering due to its excellent pozzolanic properties and has garnered significant attention from researchers. This paper presents an experimental study and a micro-mechanical discussion on the role of RHA in the mechanical improvement of soil. RHA was mixed with the native soil in varying proportions, ranging from 0% to 12%. Several laboratory tests were conducted, including standard proctor compaction tests, Atterberg limit tests, freeze-thaw tests, unconfined compression tests, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The results indicated that the optimal moisture content (OMC) of the soil mixture increased while the maximum dry density (MDD) decreased with higher RHA dosage. The Atterberg limits of the soil mixture exhibited a positive correlation with the RHA content. A substantial enhancement in the soil's strength, stiffness, and ductility was observed upon the incorporation of RHA. It was noted that the strength loss of the untreated samples and those with 12% RHA was 34.91% and 12.89%, respectively, following 12 freeze-thaw cycles. Furthermore, XRD test results revealed that the treated specimen had an identical mineral composition to the control specimen, with no generation of hydration products. SEM analysis also highlighted that the filling effect of RHA significantly reduced pore content and pore connectivity within the soil, accompanied by a shift in the specimen's pores from mesopores to small and micropores. The excellent thermal insulation and heat retention properties of RHA, along with its pore-refining effect, make a positive contribution to enhancing the frost resistance of the specimens. These findings contribute to guiding the effective application of RHA in civil engineering, offering eco-friendly solutions for biomass waste management, and promoting the sustainable development of construction materials.

Sequential treatment of surfactant-laden wastewater using low-cost rice husk ash coagulant and activated carbon: Modeling, optimization, characterization, and techno-economic analysis

Treating surfactant-laden wastewater by a sequential coagulation/flocculation (C/F) and adsorption process was investigated. The treatment process performance was modeled and optimized using response surface methodology (RSM) and artificial neural network (ANN). C/F using rice husk ash (RHA) coagulant provided 42.3 % surfactant removal at 3.79 g/L RHA dosage, pH 3.6, and 23 min slow-mixing time. For adsorption onto granular activated carbon (GAC), 96.5 % surfactant removal was maintained at 10 g/L GAC and pH = 4.5. The ANN model showed better predictive capabilities for C/F and adsorption than RSM. By applying real wastewater, the combined system effluent contained 367 ± 2.4, 18.4 ± 1.2, 4.2 ± 0.2, and 0.95 ± 0.06 mg/L for TDS, COD, oil-grease, and surfactants, respectively, with almost complete removals of turbidity and TSS. The integrated system exhibited a profitability scenario with 6.3 years payback period. The study output is beneficial for designing full-scale systems of surfactant-laden wastewater treatment and predicting the associated performance under various operating conditions.

Thixotropic evaluation of a highly-workable and a flowable concrete made with Rice Husk Ash

Thixotropic behaviour of a Highly-Workable Concrete (HWC) and a Flowable Concrete (FC) containing varying volumetric dosages (10%, 15%, and 20%) of Rice Husk Ash (RHA) has been investigated using a coaxial cylinder concrete rheometer. The parameters to evaluate the thixotropic behaviour were RHA dosage and grade of concrete. The experiments showed that concrete exhibits a high degree of thixotropy when proportioned with a binary binder containing RHA. The influence of RHA on thixotropy was more pronounced in the HWC than in the FC. The measured thixotropic indices for the HWC, i.e., initial peak stress, thixotropic index, structuration rate, structure parameter, and reduction in apparent viscosity, increased with the increase in RHA dosage, compared to the control concrete. However, the influence of RHA in the case of the FC on all the thixotropic parameters was not significant. As the concrete grade increased from M − 30 to M − 50 in the HWC, thixotropic parameters in the RHA blended concrete increased significantly compared to the control concrete.

Preparation and Microstructure of Alkali-Activated Rice Husk Ash-Granulated Blast Furnace Slag Tailing Composite Cemented Paste Backfill.

At present, the research on rice hull ash and cement-based materials as cementitious materials continues to deepen. Low-cost rice hull ash replaces part of Portland cement, which plays a dual role in saving material costs and improving environmental benefits. In this study, alkali-activated rice husk ash (RHA) and ground granulated blast furnace slag (GGBS) were used to prepare cementitious material. The influence of RHA dosage on the strength, slump degree, and coagulation time of cementitious material was studied. On this basis, tailing was used as an aggregate based on the orthogonal design method and the bone–gel ratio, modulus, and alkali content were taken as variable factors, with strength and slump degree taken as the targets. A new cemented paste backfill (CPB) was prepared and mix ratio optimization was carried out. The strength formation mechanism of cementitious material and CPB was explored by combining scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results of this study show that with the increase in RHA mixing, the unconfined compressive strength (UCS) of the gelling material purification slurry showed a tendency first to increase and then decrease. When the amount of RHA was about 10%, the internal structure became denser, more C-S-H gel was generated, and greater strength could be obtained. The specific surface area of RHA is high, and a small amount of RHA can fill the internal pores, making the internal structure of concrete more dense. The active silica content in RHA is relatively high. The addition of RHA can appropriately improve the strength of the material, which is of certain significance to our material research. Finally, the micro-analysis of RHA-GGBS clean slurry, the analysis of influencing factors of fluidity and strength, and the optimal mix proportion of alkali-activated RHA-GGBS-based backfill are put forward.

Rice Husk Ash (RHA) Based Concrete: Workability and Compressive Strength with Different Dosages and Curing Ages

Abstract To reduce the consumption of cement in construction industry has been a hot area of consideration now days due to high evolution of CO2 gases during its production. Since decades efforts are made to replace cement with cementitious materials; minerals, agricultural, industrial by products etc. A few are fly ash, ground granulated blast furnace slag, silica fume, rice husk ash etc. These cementitious materials are often adopted as partial replacement of cement. However, their effectiveness and suitability as cementitious material depends upon their properties and the source of the production. Pakistan is an agricultural country and one of the major crops is Rice crop. It produces a substantial amount of rice husk during the processing g of the rice. A substantial amount of Rice Husk Ash (RHA) is produced on the burning of rice husk used as fuel in the rice mills while generating steam for parboiling process of rice grains. This ash causes the environmental problems also if not dumped properly. RHA is believed to have siliceous properties which may be used as supplementary cementitious material in concrete. As the suitability of supplementary cementitious materials is dependent upon the source of rice husk, temperature of burning of husk, its fineness and other properties. This study is focused on to determine the effect of rice husk ash produced by burning of the rice husk obtained from the local rice mills. Experimental investigation carried includes the determination of workability and compressive strength of concrete with different dosage of RHA from 5% to 30% with an increment of 5% tested at 1day, 3days, 7days and 28 days of the age of concrete. The results are compared with corresponding concrete without RHA and tested at the same ages. The results show the reduction in both the parameter; workability and compressive strength due to RHA particularly at its higher dosage beyond 10% by weight of cement.

Utilization of ceramic waste powder and rice husk ash as a partial replacement of cement in concrete

Ceramic waste powder (CWP) and rice husk ash (RHA) are one of the highly produced waste materials from tiles industry and rice processing units respectively. Using these materials in concrete as a part replacement for cement offers several advantages like reducing the burden on landfills, reducing the construction cost by replacing costly cement and improvement in performance of concrete etc. due to their mineral composition. In the current study, an effort was made to partly replace the cement with CWP and RHA. Concrete design mix was carried out by using 0, 5, 10, 15 and 20% CWP and varied proportions of RHA were tried on the optimum CWP for cement replacement (0, 5, 10, 15, 20%). Tests were carried out on the fresh and hardened concrete specimens to study the mechanical properties of concrete. Analysis of the test results indicate that 15% CWP yielded best results and 10-15% RHA in combine proportion was found to be the optimum replacement of cement offering higher strength when assessed to the conventional concrete. Maximum compressive strength achieved at 15% CWP and 15% RHA whereas, the flexural strength and split tensile strength were attained at 15% CWP and 10% RHA dosage.

Removal of doxycycline hydrochloride from aqueous solution by rice husk ash using response surface methodology and disposability study.

The huge demand and consumption of DOX, its incomplete metabolism, and complex behavior in atmosphere are causing a great ecological issue, which needs to be solved. In the present study, the suitability of rice husk ash (RHA) for the greater sorption efficiency of DOX antibiotic was investigated. Furthermore, disposability study of exhausted RHA was performed using solidification technique and leachate had undergone toxicity test to evaluate the DOX encapsulation ability. The central composite design under RSM was employed for the design of experiment and optimization of adsorption parameters. RHA was characterized using various techniques such as XRD, SEM (EDX), FTIR, BET, and zeta potential analysis. The influence of various adsorption parameters, like initial DOX concentration (C0), RHA dosage (m), incubation-time period (t), and pH were examined on the performance in terms of DOX elimination % (X1) and adsorptive capacity (mg/g) (X2). At optimized conditions, the obtained X1 and X2 were 98.85% and 17.74 mg/g, respectively. Moreover, the kinetics data suited well to the pseudo–second-order model. Freundlich, Langmuir, and Redlich-Peterson (R-P) isotherm models were applied, out of which Langmuir model best performed under optimized conditions; m = 5 g/L, t = 85.85 min, DOX concentration = 89.73 mg/L, and pH = 6. The bacterial toxicity test of leachate confirmed complete encapsulation of DOX by solidification technique.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-18961-1.

Effect of rice husk ash (RHA) dosage on pore structural and mechanical properties of cemented paste backfill

Reducing solid waste emission is the development direction of cleaner production in the future. This paper proposes to use the agricultural solid waste rice husk ash (RHA) as an alternative cementitious material for the underground filling of mines. The pore structure and mechanical properties of cemented paste backfill with different RHA dosages (RCPB) are analyzed. The results reveal that: (1) The pore structure of RCPB is divided into three types: micropores (<0.1 μm), secondary pores (0.1–100 μm), and main pores (>100 μm). The total number of micropores accounts for the largest proportion, followed by secondary pores and main pores. The total volume of secondary pores accounts for the largest proportion, followed by micropores and main pores. (2) The porosity decreases and the UCS increases with the increase of RHA dosage and curing time. The UCS decreases linearly with the increase of RHA dosage. The UCS has a linear negative correlation with porosity. (3) The cracks of RCPB initiated at the yield point, gradually expanded at the peak point, and finally penetrated at the post-peak point. The failure mode of RCPB is mainly a tensile failure, accompanied by a small number of secondary tensile cracks. (4) The hydration products of RCPB are mainly C–S–H and AFt gels. The greater the RHA dosage and CT, the more hydration products, the fewer pores, the greater the strength, and the greater the average gray value. The outcome of this work will afford a new ideas and methods for using solid waste (Rice husk) as backfilling.

Research on the Mechanical Strengths and the Following Corrosion Resistance of Inner Steel Bars of RPC with Rice Husk Ash and Waste Fly Ash

In this paper, the slump flow and mechanical strengths (compressive and flexural strengths) of the reactive powder concrete (RPC) with rice husk ash (RHA) and waste fly ash (WFA) were investigated. The following corrosion resistance of steel bars-reinforced specimens was researched. The ultrasonic sound, the mass loss rate, the electrical resistance, and the electrical resistance time history curves were determined to reflect the corrosion resistance of steel bars. The influence of NaCl freeze–thaw cycles and dry–wet alternations was considered. Results showed that the addition of RHA and WFA demonstrated a negative effect on the fluidity of fresh RPC. The fluidity of fresh RPC with WFA was lower. Moreover, RHA and WFA could effectively improve the mechanical strengths of hardened RPC, and the enhancing effect of RHA was higher. The increasing dosage of RHA could improve the corrosion resistance of steel bars in RPC when the specimens were exposed to the environment of NaCl freeze–thaw cycles and dry–wet alternations. However, when WFA was added, the effect was the opposite. The steel bars in RPC corroded more seriously when the specimens were exposed to the environment of NaCl dry–wet alternations than the environment of NaCl freeze–thaw cycles.

A comparative study and combined application of RSM and ANN in adsorptive removal of diuron using biomass ashes

Abstract Biomass ashes like rice husk ash (RHA), bagasse fly ash (BFA), were used for aqueous phase removal of a pesticide, diuron. Response surface methodology (RSM) and artificial neural network (ANN) were successfully applied to estimate and optimize the conditions for the maximum diuron adsorption using biomass ashes. The effect of operational parameters such as initial concentration (10–30 mg/L); contact time (0.93–16.07 h) and adsorbent dosage (20–308 mg) on adsorption were studied using central composite design (CCD) matrix. Same design was also employed to gain a training set for ANN. The maximum diuron removal of 88.95 and 99.78% was obtained at initial concentration of 15 mg/L, time of 12 h, RHA dosage of 250 mg and at initial concentration of 14 mg/L, time of 13 h, BFA dosage of 60 mg respectively. Estimation of coefficient of determination (R 2) and mean errors obtained for ANN and RSM (R 2 RHA = 0.976, R 2 BFA = 0.943) proved ANN (R 2 RHA = 0.997, R 2 BFA = 0.982) fits better. By employing RSM coupled with ANN model, the qualitative and quantitative activity relationship of experimental data was visualized in three dimensional spaces. The current approach will be instrumental in providing quick preliminary estimations in process and product development.

The Effect of Rice Husk Ash and Goat Manure on the Growth of Spinach (Amaranthus gangetius)

In the period of the last ten years increased market demand for spinach makes the outlook very promising so it is less optimal for the growth of spinach caused by the soil fertility is low so that the provision of organic material can improve soil fertility through the improvement of soil chemical to support the growth of red spinach. This study aims to determine the dosage of rice husk ash and dose of manure as well as the interaction of dosage that is optimal for the growth and yield of spinach. this research, land villa, Pasir mas which failed to compass with a height of 26 meters above sea level labuhanbatu district in August until December 2020.Research design using group factorial consisting of two factors. The first factor of rice husk ash (A) consists of 4 levels, namely : A0 = 0 ton/ha (control), A1 = 1 ton/ha equivalent to 50 g/m2 (the recommended dose), A2 = 1.5 tons/ha, equivalent to 75 g/m2. The second factor, namely the granting of goat manure (K) with three levels, namely : K0 = 0 ton/ha (control) K1 = 2 ton/ha, equivalent to 200 g/m2 (the recommended dose), K2 = 4 ton/ha, equivalent to 400 g/m2, K3 = 6 ton/ha, equivalent to 600 g/m2. The Parameters measured were plant height (cm), number of leaves (strands), Weight per Plant Sample (g). The results showed that the administration of goat manure 4 ton/ha, equivalent to 400 g/m2 can increase plant height, leaf number, and weight per plant of spinach while the provision of 1.5 ton/ha, equivalent to 75 g/m2 can increase plant height, number of leaves plant spinach

Experimental study on the freezing resistance and microstructure of alkali-activated slag in the presence of rice husk ash

This study illustrates the significant influences of rice husk ash (RHA) addition on the mechanical properties, freezing resistance and microstructure of alkali-activated slag (AAS) material. The results indicate that the incorporation of rice husk ash enhanced the compressive strength, and reduced the mass loss percentage and compressive strength loss percentage during freeze-thaw cycles, improving the freezing resistance of hardened AAS pastes evidently. The primary reasons for this optimization are the synergistic functions from the potential filling effect of RHA particles and gels enrichment in nature and content of AAS samples. The former refined the capillary pores definitely and the later was responsible for the development of compressive strength. However, the excessive contents (more than 20%) of rice husk ash did make a side effect on the development of freezing resistance and microstructure of AAS samples, which was likely related to the structure of rice husk ash itself. The dosage of rice husk ash used in AAS should be within 20% when considering the achievement of better comprehensive properties.

Ofloxacin adsorptive interaction with rice husk ash: Parametric and exhausted adsorbent disposability study

The present study investigates the adsorptive interaction of rice husk ash (RHA) with Ofloxacin (OFL) antibiotic. The OFL loaded RHA was studied for its disposability by solidification to find its possible use as a building material. Further, toxicity analysis of leachate from the solidified RHA was also studied for probable leaching of OFL. The effects of adsorption parameters such as initial pH, the dosage of RHA (m), initial OFL concentration (C0), and contact time (t) on the responses % OFL removal (X1) and adsorption capacity (mg/g) (X2) were evaluated using the central composite design (CCD) based on response surface method (RSM). Kinetic and thermodynamic studies were performed at optimized parameters, and adsorption equilibrium data were illustrated by using Langmuir, Redlich-Peterson (R-P), and Tempkin isotherm models. Optimum condition was found as m = 7.94 g/L, t = 430 min and pH = 6, and at this actual responses X1 and X2 were evaluated as 79.71% and 6.28 mg/g, respectively. Pseudo-first-order kinetic fitted best for the adsorption kinetic data. Toxicity analysis of leachate from solidified RHA indicated that most of the OFL was encapsulated inside the cement and the OFL present in leachate is not sufficient to eradicate the growth of E.coli and Bacillus subtilis.

Growth Response of Red Spinach (Amaranthus Gangeticus) by Giving Cow Manure and Rice Husk Ash.

The increase in market demand red spinach (Amaranthus Gangeticus) makes the prospects very promising less than optimal for the growth of red spinach (Amaranthus Gangeticus) because soil fertility is low so that the provision of organic material can improve soil fertility through the improvement of the physical, chemical, and biological soil so that it can support the growth of red spinach. This study aims to determine the dose of manure, the dosage of rice husk ash as well as the interaction of dosage that is optimal for the growth and yield of red spinach.this research was conducted experimental farm of the faculty of science and technology with a height of 28 meters above sea level Labuhanbatu district in March to October 2020. Research design using group factorial consisting of two factors. The first factor, namely the granting of cow manure (L) with three levels, namely : L0 = 0 ton/ha (control) L1 = 2 ton/ha, equivalent to 200 g/m2 (the recommended dose), L2 = 4 ton/ha, equivalent to 400 g/m2, L3 = 6 ton/ha, equivalent to 600 g/m2. The second factor, rice husk ash (A) consists of 4 levels, namely : A0 = 0 ton/ha (control), A1 = 1 ton/ha equivalent to 50 g/m2 (the recommended dose), A2 = 1.5 tons/ha, equivalent to 75 g/m2.The Parameters measured were plant height (cm), number of leaves (strands), Weight per Plant Sample (g). The results showed that the administration of cow manure 4 ton/ha, equivalent to 400 g/m2 can increase plant height, leaf number, and weight per Plant of amaranth red. The provision of 1.5 tons/ha, equivalent to 75 g/m2 can increase plant height, the number of leaves plant red spinach (Amaranthus Gangeticus).Keywords: Rice Husk Ash, Red Spinach, Cow Manure, Plant Growth

Suitable pretreatment process for rice husk ash towards dosage optimization and its effect on properties of cementitious mortar

AbstractPretreatment processes on rice husk ash (RHA) influence its properties and in turn, the performance of concrete. However, most of the available literature captures only the influence of the RHA usage in concrete without focusing on the systematic pretreatment process and optimization of RHA dosage on physical and chemical perspective. Further, the replacements were done on weight basis, leading to higher binder volume and inaccuracies in the performance evaluation. The main objective of the present study is to adopt adequate pretreatment process and to systematically optimize the RHA dosage (vol. %) towards better strength and durability properties. Hence, the current study focuses on understanding the nature of RHA through characterization, followed by suitable pretreatment processes for enhancing the properties of RHA. The enhancement in the chemical activity of the treated RHA was assessed through pozzolanic activity tests (strength activity index, lime consumption test, and soluble silica). Based on the physical properties (particle size, surface area, and packing density), chemical characteristics (strength activity index) and the energy required, the grinding time (30 min) was optimized rationally. The optimized dosage of RHA (20% by vol.) was evaluated for its performance through fresh, mechanical, and durability properties. From the results, it is evident that adequate pretreatment, along with systematically optimized RHA dosage yields enhanced performance in concrete properties.

Justification of strength properties of microstructural changes in the black cotton soil stabilized with rice husk ash and carbide lime in the presence of sodium salts

Black cotton soils exhibit high shrinkage and swelling characteristics due to the variation in moisture content. To overcome this problem, many techniques are adopted, among which is the soil stabilization technique. Rapid industrialization and urbanization lead to the generation of waste products; the major by-products are rice husk ash (RHA) and carbide lime (CL). These by-products show excellent pozzolanic property. In this paper, an attempt has been made to stabilize black cotton soil with rice husk ash (RHA) along with carbide lime (CL) and other additives. Based on strength test results, the optimum dosage of RHA and CL was found to be 20% and 8%, respectively. The effect of sodium salts on index properties and unconfined compression strength (UCC) test at different moulding water contents for immediate testing and at different days of curing are studied. Results show that plasticity index of the soil treated with additives was decreased both for immediate and for 7 days of curing period due to the decrease in diffuse double-layer thickness. Soil–RHA–CL composite treated with 1% sodium chloride and 1% sodium hydroxide improves the Unconfined compression strength and shows a better strength compared to carbide lime-treated soil due to the formation of alkali silicate and alkali aluminate hydrated gel along with other cementitious products. The microstructural changes in the stabilized composite can be observed with XRD and SEM analysis. The addition of carbide lime and salts binds the particle with hydrated gel and shows denser environment compared to unstabilized soil.

Stabilization of a Subgrade Composed by Low Plasticity Clay with Rice Husk Ash

The construction of road works in the world has always been a challenge for engineering, especially in areas where the conditions and types of soil are not adequate for the execution of this type of projects. The present investigation has as main objective to determine the influence that has the rice husk ash (RHA) to stabilize the subgrade layer of a pavement, composed of a low resistance clayey soil. RHA is a waste and pollutant material for the environment; therefore that its use can be considered as an economic and ecological alternative. Thus, several tests were carried out where it proved the value of CBR increased from 4.30% to 20.70%, by adding a 20% RHA dosage, achieving its optimum value to be considered a very good subgrade. In this way, it is possible to affirm that the addition of RHA improves the geotechnical properties of the soil.