Resilient Modulus Values Research Articles

Prediction of Resilient Modulus Value of Cohesive and Non-Cohesive Soils Using Artificial Neural Network.

This paper investigates the application of Artificial Neural Networks (ANNs) for predicting the resilient modulus (Mr) of subgrade and subbase soils, which is a critical parameter in pavement design. Utilizing a dataset of 1683 Mr observations, the ANN model incorporates eight input variables, including soil gradation, plasticity, and stress conditions. The model was optimized using a quasi-Newton method, achieving high predictive accuracy, with a coefficient of determination (R2) of 0.9613 and low error rates for both selection and testing datasets. To further enhance model interpretability, SHAP (SHapley Additive exPlanations) analysis was conducted, revealing the significant influence of specific input parameters, such as saturation ratio, plasticity index and soil gradation, on Mr predictions. This study underscores the potential of ANNs as a practical tool for estimating resilient modulus, offering a reliable alternative to conventional laboratory testing methods. The findings suggest that integrating ANNs into pavement design processes can lead to more accurate predictions of pavement performance, ultimately supporting the development of more efficient and durable road structures.

Feasibility of Using Ferronickel Slag as a Sustainable Alternative Aggregate in Hot Mix Asphalt

Ferronickel slag (FNS) is a byproduct produced during ferronickel alloy manufacturing, primarily used in the manufacturing of stainless steel and iron alloys. This material is produced by cooling molten slag with water or air, posing significant disposal challenges, as improper storage in industrial yards can lead to environmental contamination. This study investigates the chemical and mineralogical characteristics of reduction ferronickel slag (RFNS) and its potential use as an alternative aggregate in hot mix asphalt (HMA). The research is based on the practical application of HMA containing RFNS in an experimental area, specifically the parking lot used by buses transporting employees of Anglo American, located at the Codemin Industrial Unit in Niquelândia, Goiás, Central Brazil. Chemical analysis revealed that RFNS primarily consists of MgO, Fe2O3, and SiO2, which are elements with minimal environmental impact. The lack of significant calcium content minimizes concerns about expansion issues commonly associated with calcium-rich slags. The X-ray diffractogram indicates a predominantly crystalline structure with minerals like Laihunite and Magnetite, which enhances wear and abrasion resistance. HMA containing 40% RFNS was tested using the Marshall methodology, and a small experimental area was subsequently constructed. The HMA containing RFNS met regulatory specifications and technological controls, achieving an average resilient modulus value of 6323 MPa. Visual inspections conducted four years later confirmed that the pavement remained in excellent condition, validating RFNS as a durable and effective alternative aggregate for asphalt mixtures. The successful application of RFNS not only demonstrates its potential for local road paving near industrial areas but also underscores the importance of sustainable waste management solutions. This research highlights the value of academia–industry collaboration in advancing environmentally responsible practices and reinforces the contribution of RFNS to enhancing local infrastructure and promoting a more sustainable future.

Cement-based and alkali-activated controlled low-strength materials made from cup lump rubber for use as road materials

This research explores the use of cup lump rubber (CLR), an agricultural by-product, as a component in controlled low-strength material (CLSM) for pavement applications in road construction. Two distinct CLSM mixtures were developed: one based on cement and the other on alkali activation. The study evaluated the workability, mechanical properties, and microstructures of both CLSM formulations. Key fresh properties, including slump flow, setting time, and bleeding, were analysed to assess their impact on the self-compaction process. Mechanical characteristics such as unconfined compressive strength, resilient modulus, and wave velocities were also measured. Some CLSM mixtures, both cement-based and alkali-activated, were found to meet the requirements for soil cement bases and subbases. Notably, the resilient modulus values showed significant improvement after 28 days, with certain mixtures achieving subbase-quality gravel standards. The study concludes by recommending the use of both cement-based and alkali-activated CLSMs in pavement design, highlighting their potential to enhance the field of pavement engineering.

Comparative study on in-situ resilient modulus of subgrade estimated using in-situ modulus detector

This study presents a comprehensive evaluation of the resilient modulus of unsaturated subgrade soils using a novel in-situ modulus detector (IMD) along with various laboratory and field-testing methods. The current study employs several testing devices, including bender elements, standard dynamic cone penetrometer, and crosshole-type dynamic cone penetrometer (CDP), to assess the reliability of the IMD in estimating the resilient modulus profiles of small-scale homogeneous subgrade models in unsaturated conditions. The index properties, compaction and strength characteristics of the compacted soils, are evaluated. The resilient modulus values obtained from the IMD are compared with those obtained from repeated load triaxial tests under various stress states. Experimental results show a decrease in the penetration depth per blow with increased dry unit weight. In addition, elastic modulus and shear wave velocity increase with soil density. The resilient modulus estimated from the IMD increase with both depth and soil density. A robust correlation has been established between the resilient modulus values estimated from the IMD and those estimated from the CDP or bender element tests. Furthermore, the resilient moduli estimated from the universal model and the IMD demonstrate linear relationships with a coefficient of determination greater than 0.8. Thus, the IMD may be useful for the in-situ evaluation of resilient modulus in unsaturated subgrade soils, considering influencing factors such as soil density and confining pressure.

Heavy rainfall and moisture susceptibility of pavement foundation: A case study coupling finite element method and MnROAD moisture monitoring data

The Midwest region, including Minnesota, has been experiencing increased heavy precipitation events due to climate change, and the Minnesota Department of Transportation (MnDOT) is currently investigating the effect of climate change on pavement foundation and other transportation assets. As part of this effort, a study was conducted to investigate the impact of heavy rainfall on pavement foundation performance by focusing on moisture dynamics and resilient modulus changes in the pavement base layer. This study is aimed at understanding the adverse effects of heavy rainfall on moisture fluxes within pavement foundation and corresponding stiffness of the base aggregate layer. A two-step approach was adopted for predicting changes in saturation when estimating corresponding resilient modulus values using the resilient modulus prediction equation employed in AASHTOWare Pavement Mechanistic-Empirical (ME) Design. PLAXIS 3D, a finite-element analysis tool, was utilized to simulate the movement of moisture within the pavement layers under varying heavy rainfall scenarios. By incorporating predicted saturation from PLAXIS 3D simulations into the Pavement ME equation, corresponding resilient modulus values were estimated for the base layer. To ensure its accuracy and reliability, the model was validated using field sensor data from the MnROAD facility. Multiple linear regression models were developed to provide a means for estimating resilient modulus changes due to heavy rainfall. This study highlights the importance of considering moisture effects in pavement design and maintenance in regions prone to heavy rainfall events, and findings can be used by transportation agencies as part of their transportation/geotechnical asset management programs.

Sustainable Reclaimed Asphalt Emulsified Granular Mixture for Pavement Base Stabilization: Prediction of Mechanical Behavior Based on Repeated Load Triaxial Tests

The stabilization of asphalt pavement bases with granular soil and aggregates emulsified with asphalt is a widely used technique in road construction and maintenance. It aims to improve the mechanical properties and durability of the lower pavement layers. Currently, there is no consensus on the most suitable method for designing emulsified granular aggregates with reclaimed asphalt pavement (RAP), as it is very complex. Therefore, the methodology is generally based on compliance with one or more volumetric or mechanical parameters established in the highway regulations for conventional asphalt mixtures, which does not guarantee the optimization and characterization of the recycled mixture in the base course. In this study, granular mixtures were developed, including five with emulsion and one emulsion-free as a control mix. Granular RAP mixes were designed in this study, including five with emulsion and one emulsion-free as a control mix. The five mixes ranged from 1% to 5% emulsion and were characterized by multi-stage triaxial tests with repeated load resilient modulus (RM) and permanent deformation (PD) to evaluate their mechanical behavior. The results showed that the mixes had RM values between 350 and 500 MPa, consistent with literature values. However, they showed similar levels of accumulated deformation to the control mix without RAP emulsion. The sample with 1 % RAP emulsion exhibited a satisfactory RM value and better performance in PD than the control mix (5 mm) and showed accumulated PD values of up to 4 mm. In contrast, the other samples exhibited deformations of up to 6 mm. In this study, the multi-stagge triaxial RM and PD tests were found to be an effective predictive method for characterizing the behavior of RAP materials in base courses, regardless of the types of admixtures contained. Multi-stage resilient modulus and PD tests can be considered as a predictive method for the behavior of milled material in base courses. They were able to provide initial data for interpreting the behavior of ETB mixtures.

Research on correlation between dynamic resilient modulus and CBR of coarse-grained chlorine saline soil

A large area of coarse-grained saline soil is distributed in saline soil areas, and chlorine saline soil with a high salt content is a typical representative. The dynamic resilient modulus was accurately predicted using the California-bearing ratio (CBR) value to determine the relationship between the dynamic resilient modulus of coarse-grained chloride saline soil and its CBR value. Indoor dynamic triaxial tests and CBR tests were conducted to investigate the evolution of the dynamic resilient modulus (MR) and CBR of coarse-grained chlorine saline soil under the influence of the stress level, water content, and salt content. The test results showed that the dynamic resilient modulus increased with an increase in the confining pressure and bulk stress and decreased as the deviator stress increased; however, the CBR increased with an increase in the corresponding unit pressure. The higher the salt and water contents, the more obvious the influence of stress on the dynamic resilient modulus and CBR value. Under the same stress level, the decrease in the dynamic resilient modulus and CBR gradually increased with increasing salt and moisture content, and the effect of salt tended to be more significant than that of water. Based on the correlation between the dynamic resilient modulus and CBR revealed by the experiment, a more widely applicable model was selected from the existing theoretical models related to CBR for the regression analysis of the test data, and a prediction model of the dynamic resilient modulus based on the CBR value was proposed (MR = 21.06CBR0.52). This prediction model had a high correlation coefficient (R2 = 0.893) and could effectively predict the dynamic resilient modulus of coarse-grained chlorine saline soil using CBR values. The results provide a simple and reliable method for determining the design parameters of a coarse-grained saline soil subgrade.

Performance Study on Laterite Road Base Stabilised with Emulsions Incorporating Biochar

This study explores the utilisation of biochar as an innovative and sustainable additive to emulsions for stabilising laterite road base material in pavements, with the environmental benefit of sequestering atmospheric carbon and stable form storing. A diverse range of design mixtures for the treated road base material with the proposed biochar–emulsion binder was developed for experimental validation and subsequent steps encompassed an array of laboratory tests to scrutinise the engineering attributes of the mixtures. The tests were selected to assess various properties such as unconfined compressive strength, tensile strength, resilient modulus, flexural modulus, fatigue life, and deformation characteristics. To gain practical insights from real-world conditions, two field trials were also conducted to evaluate the performance of the stabilised road base. The findings revealed that a design mix incorporating 5% biochar and 6% emulsion delivered an average unconfined compressive strength (UCS) of 1.5 MPa, which adheres to the standard UCS range for cemented lightly bound base course material. The optimal ratio of biochar to emulsion was identified as 1:1.6, which delivered a higher resilient modulus value than did the minimum stipulated by the literature for average daily traffic in the first year of design. As the temperature rose, the stabilised laterite base exhibited a reduction in its flexural modulus; however, it demonstrated minimal susceptibility to fluctuations in frequency. The deformation observed in the wheel-tracking tests for mixtures of the optimum biochar-to-emulsion ratio was less than 1 mm, which is remarkably lower than the maximum requirement outlined in the literature (i.e., 15 mm). Furthermore, visual inspection post-testing detected minimal cracking. These findings indicate that the integration of biochar and emulsion in the construction of road pavements is a promising technique that could contribute to carbon sequestration and climate change mitigation without sacrificing pavement performance. The successful field trials provided further evidence of the feasibility of this novel technique.

Predicting resilient modulus: A data driven approach integrating physical and numerical techniques

Resilient modulus (MR) is an important parameter in the design of pavement that helps to characterize the quality of sub-grade materials. Generally, it is not determined experimentally due to time consuming, uneconomical, laborious and lack of advanced equipment in many laboratories. The aim of this research is to determine MR values using experimental (Ultrasonic pulse velocity (UPV) and Cyclic Triaxial) and Artificial neural network (ANN) techniques. For experimental study twenty-four soil samples comprising of coarse and fine-grained soils were collected from different locations. For ANN modelling, Input variables comprised of essential soil Atterberg limits (liquid limit, plastic limit, plasticity index) and compaction properties (maximum dry density, optimum moisture content). The validation of ANN model is done by comparing its results with the experimentally evaluated MR from UPV and Cyclic Triaxial test. Experimental results showed that Cyclic Triaxial test yielded resilient modulus value that was 5 % more than obtained from the UPV test. Moreover, results showed that modulus of resilience (MR) values determined by UPV, and artificial neural network (ANN) modelling have significant closeness with the cyclic triaxial results of resilient modulus; thus, making it a significant development in predicting resilient modulus efficiently.

Mechanical characterization of an alternative laterite gravel used as pavement material

Laterite gravels have been successfully adopted as pavement materials in the field. Despite that, they are often rejected in material selection processes because of its base on traditional gradation and consistency limits requirements. To allow a deeper evaluation of such material found abundantly in tropical countries, along to characterizing traditional parameters, repeated load triaxial tests were performed in a Laterite Gravel from Acre/Brazil to evaluate its elastic and plastic behavior through Resilient Modulus (RM) and Permanent Deformation (PD), respectively. In addition, a simulation was conducted in the MeDiNa software, based on the test results considering stress states that are usually applied in pavement layers. The material showed RM values higher than 500 MPa, which was considered high compared to materials such as Quartz and Granite. It was also observed low permanent deformation (below 1 mm for higher tensions applied) and accommodation of displacement (shakedown) for most specimens. The simulation results showed low rutting prediction for the Laterite Gravel applied in highway pavement layers. Thus, the results indicated that the lateritic gravel can be adopted in the composition of base or subbase layers of flexible pavements, even though some limits of the parameters specified by traditional specifications were violated, as expected. In addition, we also highlight the need for adoption of new material selection strategies that are based on key mechanical characteristics to avoid discarding potentially well performing materials.

Desain lapisan Perkerasan Jalan Pada Ruas Jalan Desa Mbangga – Woloboa Kecamatan Wolowaru Kabupaten Ende

The Mbangga-Woloboa road section, Rindiwawo Village, Wolowaru District is included in the local road type with rigid pavement and a road width of 3 meters. Every year the condition of the Mbangga-Woloboa road section experiences damage, where several parts of the road have many holes and when it rains there are lots of puddles of water, which is very disturbing for road users. Even though the Ministry of Public Works, with the available funds, has repaired the existing damage by overlaying it repeatedly, it has not been able to solve the existing problem completely because the road condition has deteriorated again before it reaches its design life. Therefore, it needs to be redesigned by repairing the subgrade layer and replacing the road surface layer with new rigid pavement according to the load of vehicles passing through the road. So by using the AASHTO method, the traffic growth rate (i) of the planned road is 5.23% per year with collector road class. The effective Resilient Modulus (MR) value on the road section is 2770 psi with a CBR value of 1.87%, and DDT 2.70 kg/cm2. The thickness of the pavement layer is found to be D1 = 13 cm, D2 = 20 cm, and D3 = 41 cm.

Stiffness, rutting, and fatigue performance evaluation of cement-natural rubber latex stabilized recycled concrete aggregate

ABSTRACT The stiffness, rutting, and fatigue performance of cement-natural rubber latex (NRL) stabilized recycled concrete aggregate (RCA) were evaluated under cyclic loading. The RCA was stabilized with 3% cement content and dry rubber content to cement (r/c) ratios at 5%, 10% and 15%. The performance evaluation was carried out through advanced experiments, including indirect tensile resilient modulus test, indirect tensile fatigue test, and rutting susceptibility test using a Hamburg wheel tracking device. The results indicated that the r/c ratio of 10% was optimum for cement-NRL stabilized RCA (3C10R-RCA), which exhibited the optimum performance in terms of permanent deformation, fatigue cracking, and rutting susceptibility. The indirect tensile fatigue life of 3C10R-RCA was found to be 79.3% greater than that of the 3% cement stabilized RCA (3C-RCA), while the rut depth of 3C10R-RCA was 8% lower. Although the resilient modulus value of 3C10R-RCA was slightly lower than that of 3C-RCA, the tensile permanent deformation was found to be lower, which is associated with the lower rut depth. As a result of the significant improvement in fatigue life and rutting performance, the resistance to fatigue cracking and premature failure of cement-NRL stabilized RCA were improved.

Using Cyclic CBR Method to Determine Resilient Modulus of Hydraulic Binder Stabilised Road Pavement Base Layers

The mechanistic-empirical (E-M) design of pavement structures requires knowledge of the elastic modulus of the layers comprising the structure. The necessary cyclic (dynamic) triaxial testing is expensive and cumbersome for low-volume forest and agricultural roads. Opiyo (1995) developed a method called cyclic CBR (cCBR) to determine the resilient modulus (Mr) of granular road construction materials using CBR testing equipment. The present study tested the cCBR method on silty, fine sand stabilised with lime and a lime-cement mixture. For the test, 24 test specimens were prepared by adding 3, 5 and 7% pure lime and a 70–30 lime-cement mixture at the targeted 8–23% water content. Three metrics were used to express the bearing capacity of the specimens: (1) the commonly used CBR% value, (2) the Mr value calculated as a function of load force and elastic deformation determined as a result of the cCBR test, and (3) the resilient modulus calculated from the CBR value. The experimental results showed that the initial water content had a greater effect on the bearing capacity than the binder dosage. The present study found the cCBR procedure to be feasible. The test results were converted to a resilient modulus value using the formula developed by Opiyo and Molenaar, respectively. The calculated resilient modulus values from the CBR value exhibited a wide variation. Uzan's formula provided similar results to those calculated by Molenaar's formula. A 250 m long experimental road section was also constructed to verify the laboratory data. Based on the laboratory tests, five different 50 m long stabilisation layers were built. The bearing capacity data measured with the handheld BC-1 LFWD and KUAB-FWD equipment verified Molenaar's formula.

Mechanical properties of unbound limestone aggregates replaced by recycled glass aggregate for pavement in Canada/Quebec

This study investigated the use of recycled glass aggregate (RG) as unbound base/subbase material. The experimental tests included compaction, Los Angeles, Micro-Deval, and California bearing ratio (CBR) tests. In this regard, a fine proportion of course limestone aggregate (MG20) was replaced by RG with size ranging from 0 to 5 mm based on the volumetric method. Adding RG to the coarse aggregate improved durability in wet conditions, which is more representative of the field condition of Canada/Quebec, but decreased in dry conditions. CBR values decreased with increasing RG inclusion, but all blends with 0%–100% RG in the fine fraction of MG20 met minimum requirements for unbound granular layers in Quebec. A simple model predicting the resilient modulus values of these materials based on CBR values at different stress levels was suggested. This equation estimates Mr values of various aggregate-RG blends under a wide range of mean stresses based on their CBR values.

Resilient response and strength of highly expansive clay subgrade stabilized with recycled concrete aggregate and granulated blast furnace slag

In urban areas, due to urban development and lack of space, roads may be built on the expansive clay subgrade. Expansive clay soils increase in volume when in contact with water and shrink by losing water. Recycled concrete aggregates (RCA) are one of the components of construction and demolition (C&D) wastes that can be used instead of natural resources in road construction projects. In this research, a combined method of mechanical and chemical stabilization was used to evaluate the use of RCA as a mechanical stabilizer and granulated blast furnace slag (GBS) as a chemical stabilizer to improve the strength and resilience characteristics of expansive clay subgrade. Laboratory results showed that adding RCA wastes to expansive clay subgrade reduced atterberg limits (LL, PL, and PI) and optimum water content (OWC) and increased the maximum dry density (MDD), California bearing ratio (CBR), and uniaxial compression strength (UCS). Expansive clay subgrade with 20 % RCA was treated with GBS chemical stabilizer in order to achieve a minimum 7 days target strength of 1.7 MPa for subbase application. A series of repeated load triaxial (RLT) tests were performed according to the AASHTO T307 procedure and resilient modulus (Mr) values of the stabilized clay subgrade specimen were evaluated at different curing times under cyclic loading. Also, the proposed Mechanistic-Empirical pavement design Guide (MEPDG) model was used to predict Mr values in different confining and deviator stresses which showed a good correlation with the measured Mr values. Finally, the improvement of the clay subgrade stabilized with RCA and GBS was also supported by SEM analysis. The results obtained from this research showed that the use of RCA, in addition to reducing disposed waste and environmental pollution, can improve the physical and mechanical characteristics of expansive clay Subgrade layers.

Elastan-Polyurethane Treatment for the Stability Improvement of Coal-Fouled Ballast

This study assesses the performance of coal-fouled ballast upon treatment with a hydrophobic elastomeric polyurethane, Elastan [Elastan-stabilized fouled ballast (ESFB)] and compares it with ballast that was initially clean but became fouled after its treatment during the track service life [fouled Elastan-stabilized ballast (FESB)]. The cyclic test results revealed that the performance of ESFB was significantly poorer compared with FESB for similar levels of fouling. The ESFB had undergone higher extent of deformations and had exhibited lower damping and resilient modulus values when compared with FESB. However, the extent of breakage of ballast particles was almost similar in both ESFB and FESB samples. Further, the extent of shear strains developed in ESFB samples, especially at higher void contamination index (VCI) values and loading frequencies, exceeded the shear strain at which breakage of bonds occurred under direct shear loading conditions. Accordingly, the critical loading frequency and fouling content up to which the polyurethane-based treatment is effective is proposed in the current study. In addition, the deformations of both stabilized and unstabilized ballast are seen to be directly influenced by the interface shear strength of ballast.

Dynamic resilient modulus of heavy-haul subgrade silt subjected to freeze-thaw cycles: Experimental investigation and evolution analysis

To investigate dynamic resilient modulus (MR) of heavy-haul subgrade silt, especially in seasonal frozen regions, a series of dynamic triaxial tests were performed after various freeze-thaw (FT) cycles. The specifically designed loading sequence was proposed for determining MR, which reflected the stress characteristics of subgrade induced by heavy-haul traffic load. Furthermore, the effects of numbers of FT cycles, initial moisture content, freezing temperature, deviator stress and confining stress were comprehensively considered as state variables. The results revealed that MR showed a decreasing trend with increase of numbers of FT cycles, where the attenuation stages for dynamic resilient modulus were divided into three stages, namely, rapid attenuation, slow attenuation and gradual cessation of attenuation. Then, the increase of initial moisture content and decrease of freezing temperature led to a decrease in MR, where the higher initial moisture content was, the more obvious deterioration effect was. Meanwhile, when the freezing temperature decreased to −15 °C, the appearance of the freeze shrinkage effect inhibited the damage to the soil skeleton, and the attenuation trend of MR was alleviated. The ensuing discoveries were that confining stress and deviator stress had hardening and softening effects on the thawed silt, respectively, leading to the increase and decrease in MR. In particular, when the initial water content was higher, the softening effect caused by deviator stress was more significant. To enhance the practicability, the predicted model for determining MR was proposed that included the coupled effects of the above variables. Furthermore, the fatigue life of typical asphalt pavement structures was calculated considering the damaged dynamic resilient modulus of silt subgrade duo to the freeze-thaw cycles. The outcomes illustrated that fatigue life of pavement structures with semi-rigid and flexible base reduced by 17.5% and 22.5%, respectively, via adopting the dynamic resilient modulus values under maximum attenuation state. This study could supply meaningful reference for safe and sustainable design of heavy-haul subgrade and asphalt pavement in seasonal frozen regions.

Stiffness evaluation of Forta Fibre Reinforced Asphalt Concrete (FRAC) mixture under different pulse repetition load

Pavement structure can be designed either as a flexible or a rigid pavement based on its structural behaviour, with flexible pavements being frequently favored due to its advantages. One of the major problems that normally occurred in road construction was pavement distresses due to the quality of the materials. Numerous studies were carried out to explore sustainable ways to improve the pavement performance especially on modification of the asphaltic concrete in construction phases. This paper investigates the effect of Forta-Fi fiber on stiffness performance of hot mix asphalt mixture (HMA). In this respect, conventional asphalt binder grade 60/70 and Nominal Maximum Aggregate Size (NMAS) 12.5mm were used in the preparation of asphalt mixture specimens as specified in Superpave mix design method. Performance of modified samples incorporating 0.3, 0.5 and 0.7% of total mixture were evaluated for resilient modulus accordance to ASTM D4123 using Universal Testing Machine (UTM). The samples were tested at 25°C and 40°C with pulse repetition period 1000ms, 2000ms and 3000ms to simulate low, medium and high volume of traffic. As a result, the resilient modulus values of modified asphalt mixture improved 38% with 0.3% additive of Forta-Fi at 25°C with 3000ms pulse repetition period, while at 40°C with 3000ms pulse repetition period improved 23% with 0.5% additive of Forta-Fi. Based on these studies, the addition of fibers reinforcement into the asphalt mixture has a significant effect on resilient modulus of fibers reinforced asphalt mixture.

Neural network modeling of rutting performance for sustainable asphalt mixtures modified by industrial waste alumina

Considerable efforts have been devoted to developing a sustainable approach to road construction. The use of recycled concrete aggregate (RCA) obtained from construction-demolished concrete as a substitute for natural aggregate (NA) has increased interest. However, the inferior performance of the resulting RCA mixtures requires adding other improvement materials. To build on the few existing works in this area, the present study investigated the role of waste alumina (Al) as a reinforcement agent when added at rates of 1 %, 2 %, and 3 % by mixture weight. The experimental program consisted of volumetric properties analysis accompanying the Marshall test, dynamic creep test, and wheel tracking test. This study revealed that RCA-mixtures reached their typical Marshall and volumetric properties at 4.5 % binder content recording an increasing increment of 10 % compared to NA-mixtures which needed only 4.1 % binder content. Overall, all the utilized Al dosages improved the rutting resistance; optimally, 2 % of Al decreased the rutting depth by 26 %. This dosage also increased the index of plastic deformation, resilient modulus, and flow number values by 30 %, 16 %, and 23 %, respectively. The artificial neural network statistical technique produced a robust model (R 2 = 0.995) correlating the performed tests’ outcomes with rutting values.

Estimation of Stiffness of Non-Cohesive Soil in Natural State and Improved by Fiber and/or Cement Addition under Different Load Conditions

The aim of this study was to compare the stiffness of gravelly sand under various load conditions-static conditions using the CBR test and cyclic conditions using the resilient modulus test. The tests were conducted on natural soil and soil improved by the addition of polypropylene fibers and/or 1.5% cement. The impacts of the compaction and curing time of the stabilized samples were also determined. The soil was sheared during the Mr tests, even after fiber reinforcement, so the resilient modulus value for the unbound sand could not be obtained. The cement addition improved Mr, and the curing time also had an impact on this parameter. The fiber addition increased the value of the resilient modulus. The CBR value of the compacted gravelly sand was relatively high. It increased after adding 0.1% fibers in the case of the standard compacted samples. The greater fiber addition lowered the CBR value. For the modified compacted samples, each addition of fibers reduced the CBR value reduced the CBR value. The addition of cement influenced the CBR increase, which was also affected by the compaction method and the curing time. The addition of fibers to the stabilized sample improved the CBR value. The relationship Mr=f(CBR) obtained for all data sets was statistically significant but characterized by a large error of estimate.