Subbase Materials Research Articles

The Influence of Polypropylene Fiber and Silica Fume on the Mechanical Properties of No-Fine Concrete with Recycled Aggregate

No-Fines Concrete is a type of concrete produced without fine aggregate or sand. Because of its high porosity, it allows rainwater to seep into the ground, directly replenishing the groundwater aquifer. With a design load of three tons, no-fine concrete can be utilized as pavement for rural roads. Additionally, this type of concrete can be utilized as a sub-base material in both flexible and rigid pavements. Aside from No-Fines Concrete's permeability properties, asphalt overlays are another option. This research studied the impact of silica fume and polypropylene fiber on the properties of no-fine concrete with recycled aggregate. The ratios of cement to aggregate and water to cement were 1:4 and 0.3, respectively. The recycled aggregate was demolished reactive powder concrete used in percentages of 10, 20, and 30% as a substitution for coarse aggregate by volume. The recycled aggregate percentage of 10% was the optimal percentage as it showed the least adverse effect on the no-fine concrete mixes. The polypropylene fiber was then added to the no-fine concrete mixes with 10% recycled aggregate in the percentages of 0.5, 1, and 1.5% by volume. The optimum percentage of polypropylene fiber was 0.5%, which improved the mechanical properties of no-fine concrete. Silica fume was used as a partial substitution for cement at a percentage of 10% and added to no-fine concrete mix with 10% recycled aggregate. The results show that using 10% silica fume and 0.5% polypropylene fiber with 10% recycled aggregate increased the splitting tensile strength, flexural strength, compressive strength, and modulus of elasticity by (22.54 and 40.32%), (22.22 and 35%), (21 and 35.37%), and (22 and 38.19%) compared to reference mix (NC) and the no-fine concrete mix with 10% recycled aggregate (RNC10), respectively. In comparison, the dry density was higher by (1.34%) than RNC10 and lower by (0.68%) than NC.

Comparative Study on Physical Characterization of Reclaimed Asphalt Pavement and Natural Aggregate in Flexible Pavement

Reclaimed Asphalt Pavement (RAP) has gained significant attention in recent years as a sustainable alternative to natural aggregate in road construction. This study presents a comparison of the physical attributes of RAP and natural aggregate, with a focus on their potential use as base and subbase materials in flexible pavements. The physical attributes of RAP and natural aggregate were evaluated using standard laboratory tests, including particle size distribution, specific gravity, water absorption, impact value test, Los Angles Abrasion test, flakiness and elongation test. The research concluded that RAP is comparable to natural aggregate in terms of particle size distribution and bulk density but has lower water absorption, impact, and abrasion values. The results shows that RAP is almost 53% more tougher that natural aggregate when tested for Aggregated Impact test and 30% more harder than natural aggregate when compared by Los Angeles abrasion test. Also, heatmap was used to analyse the relationship between physical attributes of natural aggregate and reclaimed asphalt pavement which depicted 93% similarity The findings suggest that RAP has the potential to replace natural aggregate in flexible pavements, further study is required to determine its long-term performance and durability.

Application of Class C Fly Ash and Quarry Dust Mix for Utilization as Subbase Material in Flexible Pavement

Application of Class C Fly Ash and Quarry Dust Mix for Utilization as Subbase Material in Flexible Pavement

Performance of Reinforced Subbase Materials by Geogrid as Abase Layer Under Weak Subgrade

The current study examines how an unpaved road behaves when it is installed on top of a soft clay layer that's been strengthened at the subgrade/subbase interface with a single layer of geogrid type SS2 is used to reinforce a laboratory model, and cycling load is used to apply repeated loads to the model. Subbases with and without reinforcement over soft subgrade were built in a sizable test box. (1000 mm×1000 mm×1000 mm). The test results show that using a geogrid reinforcement layer enhances the number of cycles and stress distribution while decreasing displacement on the soft subgrade surface on reinforced models compared to similar unreinforced ones for the same rutting value (85 mm). The rate of increase in failure time is about (6.12, 3.7, and 1.7) for 150, 230, and 300 mm thickness, respectively. The rate of redaction in vertical stress is about (18, 12.5, and 7.1) % for 150 mm, 230 mm, and 300 mm thickness, respectively.

Evaluation of carbonated incineration bottom ash using exhaust gas and CO2 discharged from waste incineration facilities as ground material

This study focused on a carbonation treatment that immobilizes trace elements such as lead (Pb) in incineration bottom ash (IBA) using the exhaust gas and the refined carbon dioxide generated (CO2) recovered at the Japan's first incineration facility, which recovers CO2 in the gaseous form. This study describes (1) the bearing capacity of IBA from the municipal solid waste (MSW) obtained through the California bearing ratio (CBR) test to investigate the possibility of using IBA as a base course material, (2) mechanical characteristics of IBA using the cone index test, to investigate the possibility of using as an embankment material, and (3) leaching properties of IBA from MSW obtained through a single batch leaching test and the long-term outdoor exposure of the leaching test to evaluate the effect of carbonation treatments. Results reveal that there was no effect of trace components not included in the separated and recovered CO2, and that the effect of carbonation could be obtained even if the exhaust gas was used directly. The carbonated IBA can be applied as a sub-base course material based on its mechanical properties, regardless of the carbonation conditions. In addition, carbonated IBA can be used as an embankment material owing to its sufficient cone index value. Regarding the heavy metal and metalloid leaching behavior, it was revealed that all the IBA samples satisfied the soil environmental standards set by the Ministry of the Environment, Japan, except for Cr (VI). The long-term leaching characteristics of carbonated IBA showed that Pb could be immobilized over a long period.

Influence of cohesion on California bearing ratio of clay–gravel mixtures

An understanding of the behavior of cohesive sediment is required to solve various engineering problems such as scour around bridge elements, mitigation of soil erosion, pavement design, river bed degradation, stable channel design. Pavement foundation designers principally use the California bearing ratio (CBR) to describe the subgrade and subbase materials and their strength. Several laboratory experiments were done to study the variation in the CBR of cohesive mixtures comprised of clay–gravel mixtures. Nine different clay–gravel mixtures were used in which the clay content varies from 10% to 50% by weight. The variation of the CBR with clay percentage, moisture content, and undrained shear strength parameters was studied. The CBR value reduces with the increase in the moisture content and clay fraction in the mixtures and increases with an increase in the dry density of the mixture under unsoaked conditions. The CBR also increases with the increase of the angle of internal friction of clay–gravel mixtures. A functional relation has been identified to estimate the CBR of clay–gravel mixtures. Using multiple linear regression analysis (MLRA), a relation is proposed to estimate the CBR of clay–gravel mixtures under unsoaked conditions. A statistical analysis was done to judge the behavior of the pertinent variables on the CBR. The proposed relation predicts the CBR of clay–gravel mixtures very well. Artificial neural network (ANN) analysis using R programming was also done to determine the effects of the pertinent variables on the CBR. ANN methodology was applied to predict the contribution of each variable. Three different methods: Garson algorithm, Olden algorithm, and Lek's profile model are used to assess the influence of variable parameters. The Olden algorithm and Lek's profile both show positive association of cohesion with CBR in an unsoaked condition. The role of moisture content was found to be marginally negative in the Olden algorithm and Lek's profile results. It is found that both the ANN and MLRA models are accurate in predicting the CBR of clay–gravel mixtures. It was further found that the MLRA and ANN models are reliable and rapid tools for correct assessment of the CBR of cohesive soil mixtures using the basic soil properties.

Engineering Structural Strength Properties of Lateritic Soil-Cement Mix for Road Pavement Stability

Qualitative construction materials in highway pavement prompted addition of cement at different proportion of 2 - 10% to lateritic soils for enhanced performance. Engineering geological tests were performed on the soil-cement mixture to determine their highway pavement suitability for durable road construction. Furthermore, modelling of the strength characteristics of the mixture presents the correlation between the structural properties and cement mix. Thus, increase in soil-cement California bearing ratio (CBR) and unconfined compressive strength (UCS) values with higher cement mix of 8%, revealed enhanced soil improvement. The soil strength is also affected by the curing period. Better quality strength characteristics obtained decreases pavement thickness with reduced cost in road construction. Relationship between the soil strength properties and cement mix content are represented by polynomial model. This reveals stronger bearing capacity of soil cement mix cured in 14 days with R2 ≥ 0.8. The lateritic soil cement mix at 8% cement content could serve as highway subbase and base construction materials. Cement mix having positive effects on soil geotechnical properties are indication of its effectiveness in enhancing volume stability of different soils. Prolong curing time is essential for compacted soil cement mix for enhanced geotechnical engineering properties and to improve the quality of lateritic soil used as road construction materials. Thus, cement-stabilized lateritic soil reduces cost of road construction, its persistent failure, human and environmental losses.

Effects of subbase materials on phosphorous attenuation in permeable pavement system and correlation between pollution attenuation and subbase materials

AbstractIn this study, laboratory models of six permeable pavement system (PPS) columns with various subbase configurations were examined for phosphorus attenuation. Experiments were carried out under varying intensities and durations of rainfall to investigate possible PPS modifications to enhance the performance of phosphorus attenuation and the likelihood of phosphorus leaching back to infiltration. The results show the inefficiencies of phosphate attenuation in the conventional PPS structure. During long‐duration rainfall events, phosphates can be leached back to the infiltrate through the conventional PPS structure. The intensity of rainfall affects the attenuation of total phosphorus through the six permeable pavement columns. To achieve an enhanced phosphate attenuation, the findings of this study suggest modifying the PPS structure by incorporating thin sand layers in the subbase. Also, the correlation between pollutant attenuation and subbase materials is found. Finally, design modification of PPS is recommended to enhance the pollutant attenuation capacity of the PPS.

Reliability-Based Design Optimization of Chemically Stabilized Coal Gangue

Abstract The coal gangue (CG) is a noncombustible waste mechanically separated from coal during the sorting or coal washing phase of mining. Because of the negative implications of unscientific disposal of CG, there is a need to utilize it in bulk civil engineering works. More precisely, the application of CG in earthworks facilitates its bulk application. The present study aims to evaluate the unconfined compressive strength (UCS) characteristics of lime- and gypsum-treated CG. The lime and gypsum dosages were varied from 2 to 6 % and 0.5 to 1.5 %, respectively. The influence of lime and gypsum addition on the UCS was evaluated for varying curing periods (CPs) of 7, 14, and 28 days. An exponential model is developed to evaluate UCS based on the experimental data using lime content, gypsum content, and CP. Further, attempts were made to estimate the optimum amounts of lime and gypsum content for satisfactory UCS performance of stabilized CG using target reliability-based design optimization (TRBDO). Furthermore, carbon footprint analysis (CFA) was performed to quantify the environmental benefits attainable by applying CG as subbase material in the pavement. The results showed that the maximum dry density increased from 1.74 to 1.84 g/cc for 4 % lime addition. The UCS of CG linearly increased with an increase in lime dosage, gypsum dosage, and CP. The highest increment of 1,050 % was attained for 1.5 % gypsum and 6 % lime addition. The CFA results indicate that CG’s procurement (embodied) emissions are substantially higher, with an 88 % share in overall emissions. From the reliability studies, it is noted that the TRBDO is helpful in predicting the optimum dosages of lime and gypsum for the satisfactory performance of pavements.

Hydrological, mineralogical and geotechnical characterisation of soils from Douala (coastal, cameroon): potential used in road construction

The life span of pavements in coastal areas is diminutive due to high traffic levels. In this study, soils from different localities (Dibamba, Bekoko and Lendi) in the Douala coastal area were investigated, for their hydrological, mineralogical and geotechnical properties. This is to determine their potential used as raw material in the sub-base or base layer for road construction. Hydrological analysis of data for the past twenty years revealed that the average annual temperature stood at 27.5 °C with average precipitation of about 433.1mm. Average relative humidity was 82% throughout the year. XRD/XRF analysis were carried on the different soil samples and revealed quartz ranges from 52 -72%, kaolinite (20–35%); goethite (4–5%), anatase (3–4%) and feldspar (0–4%). The mineralogical content of these soils was similar to silico-aluminous-ferruginuos-titanous soils characterized by high silica content (43.52–66.4%), moderate alumina (13.5–31%), low content of Fe2O3 (2.5–3.2%) and TiO2 (1.2–2.02%). The silica/sesquioxide ratio of the various sample ranged from 1:1 to 1:3 indicating that the samples from Bekoko are non-lateritic, those of Dibamba are lateritic while the soils from Lendi are true laterite soils. The laterites are suitable for the sub base layer of road pavements. Specific density of investigated samples ranges between 2.12 and 2.32 g/cm3 a result of low degree of laterization. The percentage of clay in the fine fraction for samples from Bekoko, Dibamba and Lendi stood at 24.5%, 19.0% and 14.9% respectively. These values are lower than 35% which is the standard value recommended for sub-base material by the CEBTP. The Atterberg limits range from 11.50 to 22.4% hence samples from Lendi are the low plasticity while those of Bekoko and Dibamba have a moderate plasticity with low swelling potentials. Soil samples from Dibamba and Bekoko were of the A-7-6 group while Lendi soil samples were of the A-7-5 group which correspond to clayey soils and hence classified as poor materials for road construction according to American Association of State Highway and Transportation Officials (AASHTO) classification. The Unified Soil Classification System (USCS) revealed that, the majority of samples collected in the study area belonged to the SM group (silty sand) except DIB1 and LEN1 samples which pertain to SC group (clayey sand). The average of the maximum dry density (MDD) values stood at 1.9 g/cm3 with an average moisture content of 11% corresponding to the lower limit recommended for the use as sub-base materials. The value of CBR range between 8.6 and 28,2% which correspond to class S4 and can be used as raw material for the foundation layer of low traffic (T1) in the CEBTP standard. If those materials are treated with coarse gravel, cement and/or bitumen, they can be used on sub-base and base layer of high traffic (T2/T3).

Laboratory and Field Evaluation of Stabilized Fly Ash as an Alternative Material for Sustainable Pavements

Thermal power plants in India produce a large quantity of fly ash, which is harmful to the environment. Underutilization of fly ash and the scarcity of natural minerals have created the need for an unusual construction strategy to prevent huge waste dumps on valuable land and to preserve fast-depleting resources. A study was conducted to determine the efficacy of lime-stabilized fly ash blended with quarry fines as flexible pavement subbase materials. The laboratory investigations were conducted to determine compaction characteristics, unconfined compressive strength, California bearing ratio (CBR), and durability to obtain the optimal quarry fines, fly ash, and lime (QFL) mix. The durability of QFL mixes was studied using 12 wetting–drying cycles. Using the strength and durability criteria specified by the Indian Road Congress, the optimum mix proportion of 40Q:60F+3L was determined. Pavement analyses were performed using the IITPAVE program. The QFL mix was observed to be superior to conventional granular subbase (GSB) layer material in terms of service life and cost-effectiveness. A field investigation was carried out on trial test sections constructed using the optimum QFL mix and GSB in the subbase layer of pavement. Field dry density and dynamic cone penetrometer (DCP) tests were performed on the compacted subgrade and subbase layers to assess the desired quality assurance in the construction of test sections. The early structural performance assessment of pavement sections using a falling weight deflectometer (FWD) test indicated that QFL could effectively replace conventional GSB.

Stabilization/Solidification of Petroleum Oil-Contaminated Soil using Different Stabilizers to Deliver a Pavement Subbase Material

Stabilization/Solidification of Petroleum Oil-Contaminated Soil using Different Stabilizers to Deliver a Pavement Subbase Material

Road Performance Investigation on Fiber-Reinforced Recycled Cement Base Material.

The characteristics of the materials used in early buildings in China have led to a large proportion of discarded red bricks among the construction waste generated by demolishing abandoned buildings. The application of red brick aggregate with a particle size ≤5 mm and red brick powder with particle size 0.125~0.75 mm (referred to as recycled brick powder) was studied in this study after the crushing of waste red brick in road structures. The research results will provide a theoretical basis for the whole-grain recycling of waste red brick aggregate. The aggregate of red brick with a particle size smaller than 2 mm was mixed with different amounts of cement soil and fiber to prepare a cement-stable binder for the sub-base material. The recycled brick powder of 0.125~0.75 mm was used to replace the quartz sand with different substitution rates. As pavement materials, different amounts of fiber were used to prepare fiber-reinforced recycled-brick-powder cementitious composites. The optimal mixing ratio of the two materials was evaluated from the mechanical properties. The results showed that the optimal mixing ratio of the cement-stable binder was as follows: waste-red-brick-aggregate content was 50%, cement content was 4%, and fiber content was 0.2%. The optimum ratio of fiber-reinforced recycled-brick-powder cementitious composites was determined to be as follows: the replacement rate of recycled brick powder is 25%, and the content of PVA fiber is 1%. The regression analysis was used to fit the equations between the fiber content and the 7d unconfined compressive strength and the tensile strength of the cement-stabilized binder for different red-brick-aggregate admixtures at 4% cement content. A scanning electron microscope was used to observe the failure modes of the fiber. The influence of failure modes, such as pulling out, fracture, and plastic deformation, on the mechanical properties was expounded.

Extraction and characterization of microplastics in Landfill-Mined-Soil-like-Fractions: A novel methodology

Utilization of Landfill-mined-soil-like-fractions (LFMSF), a major constituent of landfill mined residues and resembles organic soil, is essential for landfill mining activity to be a sustainable practice. In this context, the potential utilization schemes of LFMSF such as compost, buffering material, landfill biocover, road subbase, and structural fill material were explored by earlier researchers. However, as the LFMSF originates from unscientifically created landfills/dumpsites (UCLDs) and/or engineered landfills (ELFs) that contain microplastics (MPs), there exists a school of thought that its utilization might contaminate the geoenvironment in the long run. Hence, it becomes mandatory to investigate their presence in LFMSF which unfortunately has not been attempted. In this context, to estimate the presence of MPs in LFMSF, it would be prudent to adopt the methodologies applied for their extraction and characterization in the organic-rich solid matrices (ORSMs). However, limitations associated with the existing protocols of (i) organic matter removal and (ii) ultrasonication in their extraction and characterization call for developing appropriate methodologies. Keeping this in view, a novel methodology for extraction and characterization of MPs in ORSMs by incorporating modifications to the existing protocols was developed and the details are presented. Further, the efficacy of the proposed methodology when employed for extracting MPs from the standard ORSMs and LFMSF has been verified. Subsequently, this methodology was adopted to estimate the concentration of MPs present in the LFMSF samples obtained from four different UCLDs/ELF. It was observed that the concentration of MPs in LFMSF samples varies between 23361.11 ± 1927.77 and 42066.67 ± 1713.02 particles/kg. Moreover, light-density polymer (i.e., polyethylene and polypropylene) based MPs amount to ≈50 % of their total concentration. In authors’ opinion, the proposed methodology should be applied to (i) extract and characterize the MPs present in other ORSMs and (ii) develop protocols/guidelines for utilizing LFMSF for different sustainable development applications.

Literature Review on Effects of Saturation on Soil Subgrade Strength

Abstract: Subgrade is the layer of soil on which the subbase or pavement is constructed, give support to the remaining part of the pavement system. It is critical for highway engineers to begin a subgrade with a California Bearing Ratio (CBR) value of at least 10. Lot of Researches shows that if a subgrade has a CBR value less than 10, the subbase material will divert under traffic loadings in the same way as the subgrade and cause pavement degradation. The subbase, the layer of aggregate material just below the pavement, gives drainage and stability to the pavement. Undrained water in the pavement substantiate layers can freeze and expand, rising internal pressures on the pavement structure. Additionally, flowing water can move soil particles that clog drains and, in fusion with traffic, pump fines from the subbase or subgrade. It is therefore essential that highway engineers develop a strong, permeable subbase with longitudinal subdrains. This paper provides a literature review on effects of saturation on soil subgrade strength.

INVESTIGATING CAUSES OF FLEXIBLE PAVEMENT FAILURE: A CASE STUDY OF THE BAKO TO NEKEMTE ROAD, OROMIA, ETHIOPIA

Most of the roads constructed in Ethiopia fail prematurely before serving the design life due to various causes arising from many factors. One of the roads that failed before reaching its design lifetime is the Bako to Nekemte Trunk Road. This road was constructed and opened to traffic in 2013. The design pavement life was estimated at 20 years. However; pavement failures have manifested since 2014 after it was opened for traffic. The main objective of this research was to investigate the cause for the failure of flexible pavement on the Bako to Nekemte road segment. To achieve this objective, the study was followed by the experimental research type and purposive sampling method. Also, field observation and pavement condition survey methods for data collection were used. The asphalt, base course, subgrade, and sub-base layer material sampled from the road segment are the material used for this study. Different pavement failures such as rutting, pothole, alligator cracking, raveling, edge cracking, depression, and corrugation were observed along the road section. For estimations of pavement condition index, the road was divided into five different sections based on distress densities, which were measured during the pavement condition survey. From those five sections, four sections were selected for the determination of the Pavement Condition Index (PCI). Using systematic random sampling 159 sample units were evaluated for Pavement Condition Rating (PCR) and the result shows 1.89% excellent, 8.18% very good, 20.13% good, 31.45% fair, 18.87 % poor, 18.24% very poor, and 1.26% failed. Based on PCI value, samples of pavement layer were taken from failed surface condition (1), poor surface condition (2), and none distressed area (1) for comparison purposes. Different quality tests like Atterberg limit, wash gradation, soil classification, compaction test, California Bearing Ratio (CBR), Los Angeles Abrasion (LAA), Flakiness Index ( FI), Aggregate Crushing Value (ACV), Ten percent fines value (TFV), bitumen content, and gradation of asphalt were carried out. The results of these tests were compared with ERA specifications to identify the probable cause of pavement failure. The study found that the cause for failure of flexible pavement in the case of Bako to Nekemte was: insufficient and absence of side drainage structure, traffic loading, poor gradation of base course and sub-base material, and poor quality of subgrade soil. The study also recommended that the road urgently needed routine maintenance as a treatment option to reduce further deterioration and extend its service time.

Utilization of Waste Dust from Asphalt Concrete Manufacturing as a Sustainable Subbase Course Material in Pavement Structures

High calcium waste dust from asphalt concrete manufacturing was utilized to stabilize low-quality lateritic soil as a subbase course material in road structures. Asphalt waste dust up to 30 percent by weight (wt%) was incorporated into the solely lateritic soil and the mixture of lateritic soil containing 5 wt% Portland cement. The asphalt waste dust was successfully used as a subbase course material in road structures according to the standard specifications of pavement materials issued by the Thailand Department of Highways. The minimum 20 wt% asphalt waste dust induced a sufficiently high California bearing ratio, optimized plastic index, liquid limit, and swelling index of soil above the minimum standard requirements for a subbase course material. The fine particles of asphalt waste dust showed filler-like properties to reduce the voids and generated a very dense surface in the stabilized lateritic soil samples. With the small content of cement mixes, a decrease in the calcite phase in the soil stabilized with asphalt waste dust indicated a partial promotion of CaCO3 from the asphalt waste dust in the cement hydration reaction. The very high strength (CBR > 250%) of these stabilized soil samples approached the standard for base course material (CBR ≥ 80%), which was beyond the expectation for the subbase material (CBR ≥ 25%). Thus, recycling-waste dust from asphalt concrete manufacturing can be used as an effectively sustainable subbase course and base course materials in further generation for road construction purposes.

Engineering properties of marginal lateritic soil stabilized with one-part high calcium fly ash geopolymer as pavement materials

This research investigated the engineering and microstructure properties of marginal lateritic soil (MLS) stabilized with one-part high calcium fly ash geopolymer. High calcium fly ash (FA), a by-product of an electrical power plant in Thailand was used as a starting material and solid sodium hydroxide (NH) in flake form was used as an alkali activator. The influences of NH content, soaking conditions, and curing time were studied. The unconfined compressive strength (UCS), indirect tensile strength (ITS), and microstructure were investigated. Test results showed that the use of one-part high calcium FA geopolymer (OP-G) to stabilize MLS can improve the engineering properties noticeably. The samples with 20% NH content yielded the maximum 7-day UCS of 1930 kPa and 2800 kPa under soaked and unsoaked conditions, respectively, corresponding to the maximum 7-day ITS of 270 kPa and 400 kPa. The 28-day UCS and 28-day ITS of MLS samples stabilized with OP-G were higher than the 7-day UCS and 7-day ITS of samples. This indicated the continued reaction of the OP-G stabilized MLS. The 7-day soaked UCS of the stabilized MLS was higher than 689 kPa required for subbase materials according to the Department of Highway (DOH), Thailand. The total cost, cost/UCS ratio, and CO2 emission of OP-G were lower than those of two-part geopolymer stabilized MLS samples. The outcomes of this research thus support the utilization of OP-G as an alternative to Portland cement in treating MLS for use as pavement materials.

Lateritic Soil Improvement Using Lime and MOFIC

This study investigates the effects of mucilage from Opuntia ficus-indica cladode (MOFIC), a bio-modifier, on Lime-stabilized Lateritic soil's durability and index features. Specifically, this research assessed the alterations to the Atterberg limits, compaction characteristics, California bearing ratio (CBR), index values and the unconfined compressive strength (UCS) properties of the soil samples and the stabilised samples through laboratory experiments. Lime + MOFIC was added to the soil at 0%, 2%, 4%, 8%, 12% and 16% wt (%) of soil. The result confirms alteration in the index and strength characteristics of the soil upon the addition of MOFIC to the Lime-treated Lateritic soil. The geotechnical characteristics of the soil improved from a subgrade soil to a subbase material upon the addition of 2% of LIME + MOFIC; with the presence of Lime + MOFIC at 2–4%, the bearing capacity of the soil improved from a subgrade material to a subbase material according to the Nigerian General Specification. The highest CBR value in Lime-stabilised was 56%, while the CBR value of Lime + MOFIC-stabilised soil was 70%. This represents a 20% increment in CBR. The presence of polysaccharides in MOFIC enhanced the soil binding attributes of the Lime and hence accelerated the strength properties of the soil. The promotion of green construction and reduction in environmental impacts of using Lime motivates the use of MOFIC in the study. Based on the result of the experimental research, MOFIC is thereby recommended as an eco-friendly alternative for enhancing engineering properties of pavements interlayers. The addition of MOFIC improved the index and strength properties of pavement interlayer material in road construction.

Eco-friendly stabilization of highway lateritic soil with cow bone powder admixed lime and plastic granules reinforcement

Modernization, industrialization and rapid changes in the modern lifestyle have resulted in massive waste materials in the environment. Scientists are continuously evolving innovative ways for efficient reuse/recycling and the safe disposal of waste materials. This study explores potential waste materials reuse in additive stabilization of a fair to poor highway lateritic soil (clay with low plasticity/silty clay) as a sub-base material and the impact of such additives in reducing the lime content during soil stabilization treatment. Soil samples obtained from road construction burrow pit in Ado-Ekiti, south-west, Nigeria were classified as CL group (clay with low plasticity), according to the Unified Soil Classification System (USCS) and A-6 material (silty clay) which is fairly poor highway material. Hydrated lime, Cow bone and plastic wastes were also locally sourced. Geotechnical tests (Compaction, Unconfined Compressive Strength test, direct shear and consolidation test) were carried out on the control and stabilized samples according to BS 1990. The results of the Unconfined Compressive Strength tests revealed that the 90 % lateritic soil +10 % lime and a combination of 6 % lime +7 % cow bone powder +1 % plastic waste (6 % L +7 % CBP + 1.0 %PP) mixes produced the best result for the lime stabilized and waste-lime stabilized soil samples, respectively. The direct shear tests, indicated a reduction in the soil’s cohesion (c) from 38 kN/m 2 to 28 kN/m 2 and an improvement in the angle of internal friction ( ϕ ) from 29º to 45º for the optimum waste-lime mix. 10 % lime (L 10 ) sample recorded comparatively lower c and ϕ values of 33 kN/m 2 and 41º, respectively. The mix (6 % L +7 % CBP + 1.0 % PP) had improved the unsoaked and soaked CBR of 61.7 % and 37.6 %, respectively compared to the lime stabilized soil which recorded lower values of 57.8 % and 31.3 %, respectively. The permeability of the soil was reduced from 3.22e-03 cm/s to 9.12e-04 cm/s on the application of 10 % lime however the waste-lime optimal mix produced a lower value of 5.26e-04 cm/s. The results of the consolidation tests also revealed that the 6 % L +7 % CBP +1.0 % PP sample had a lower coefficient of volume compressibility (Mv) of 1.065e-04 m 2 /kN than the untreated samples which is 1.365e-04 m 2 /kN implying the stabilized mix is less susceptible to compressibility than the untreated samples. The durability results revealed that the sample recorded a strength of 201.7 kPa after being subjected to 3 wet-dry (w-d) cycles for 6 % L +7 % CBP +1.0 % PP sample, while the 10 % lime stabilized soil was found to have a strength of 148.5 kPa strength. Based on the findings, it can be concluded that the 6 % L +7 % CBP +1.0 % PP mix performed better than the 10 % lime stabilized mix with the waste materials substituting for 4 % of the lime and producing better results in terms of suitability as a highway sub-base material. • The partial replacement of lime improved weak highway lateritic soils. • Waste materials (cow bone powder and plastic granules) were suitably reused. • Near-zero emissions processing of stabilization additives was achieved. • Cleaner and energy-saving methods were employed for the disposal of waste. • Reduced weather sensitivity and compressibility were achieved for the soil mixture.