Road Base Course Research Articles

Geotechnical Assessment of Selected Lateritic Soils in Southwest Nigeria for Road Construction and Development of Artificial Neural Network Mathematical Based Model for Prediction of the California Bearing Ratio

Investigation of the geotechnical characteristics of eighteen different lateritic soils within southwest Nigeria was carried out to determine their suitability for road construction. To achieve this goal, the lateritic soils samples were subjected to different laboratory tests, including specific gravity, Atterberg limits, grain size analysis, California bearing ratio, and compaction, in accordance with the ASTM standard procedure. The results of the tests showed that the specific gravity varied between 2.55 and 2.81; the linear shrinkage varied between 6.68% and 10.98%; the liquid limit varied between 37.17% and 56.93%; the plastic limit ranged from 19.47% to 37.14%; the plasticity index ranged from 3.81% to 30.29%; the fine sand content ranged from 37.07% to 62..93%; the fines content ranged from 36.4% to 60.9%; the maximum dry density ranged from 1747 kg/m3 to 2056 kg/m3 ; the optimum moisture content ranges from 10.94% to 20.51%; the un-soaked California bearing ratio ranged from 14.7% to 45.6%; and the soaked California bearing ratio ranged from 10% to 31%. Based on these results, all the studied soils can be used as road subgrade, while none except Loc.5/S1 is suitable for road subbase. However, none of the soils meets up with the requirement for road base course. The suitability of laterite for the construction of road depends largely on the California bearing ratio. However, laboratory tests for determining the California bearing ratio is tedious, time consuming and costly. As a result of this difficulty, there is a need to develop soft computing models to predict laterite California bearing ratio from index properties with cheap and simple tests. Thus, the experimental datasets of the eighteen studied lateritic soils were used to create and train artificial neural network (ANN) models to predict California bearing ratio from liquid limits, plasticity index, linear shrinkage, fine sand content and fines content. The proposed ANN models were compared with the multiple linear regression models proposed in this study and various regression based models suggested in the literature via statistical analyses. Based on the model comparison, the proposed ANN models outperformed the rest of the models; they presented the highest R 2 and the lowest RMSE, MAPE and MAE values. Thus, the ANN models are validated. To enhance the practical application of the proposed ANN models, they were transformed into simple mathematical equations, which gave the same predictions as the direct ANN models. Thus, they can be used for practical purposes.

Pavement Performance of Fine-Grained Soil Stabilized by Fly Ash and Granulated Blast Furnace Slag-Based Geopolymer as Road Base Course Material

Pavement Performance of Fine-Grained Soil Stabilized by Fly Ash and Granulated Blast Furnace Slag-Based Geopolymer as Road Base Course Material

A method to detect uniformity of road base course based on impact imaging technology

The damage of road base course has the characteristics of strong concealment and difficulty in detecting. For this reason, the impact imaging method has been used for detection of road base course. This paper discussed systematically collection points setting, excitation mode and data processing method. Through the application in testing for highway pavement base before and after grouting maintenance, the results show that the method is simple and accurate. The detection results can be displayed in a two-dimensional image form and it is easy to be used in road maintenance. This method can be used to identify and locate the damages of the pavement base, to judge the uniformity of the pavement base structure. It can also be used to evaluate the effectiveness of internal damage after grouting repairing.

Recycled concrete aggregate and cinder gravel as base course construction materials

In this research, the potential use of recycled concrete aggregate (RCA) and CG as a base course construction material was investigated. A laboratory test involving the mechanical stabilization of RCA and CG was conducted to examine their physical properties. Eight samples of RCA blended with CG in varying proportions from 0% to 100 % with 10 % variation were studied. The laboratory test results indicate that 100 % CG yields specific gravity (SG), aggregate crushing value (ACV), aggregate impact value (AIV), Los Angeles abrasion (LAA), flakiness index (FI), elongation index (EI), plasticity index (PI), water absorption, soundness, and California bearing ratio (CBR) values of 2,54 %, 38,37 %, 20,10 %, 33,17 %, 5,59 %, 12,09 %, 0,90 %, 3,52 %, 10,60 %, and 38,08 %, respectively. The results for 100% RCA show SG, ACV, AIV, LAA, FI, EI, PI, water absorption, soundness, and CBR values of 2,70 %, 9,56 %, 5,30 %, 9,20 %, 15,30 %, 15,84 %, NP, 0,23 %, 1,49 %, and 105,87 %, respectively. These results also fail to meet the gradation requirements based on ERA standard specifications. Therefore, mechanical stabilization was adopted to improve the physical properties of the samples. Blending 60 % RCA with 40 % CG resulted in SG, ACV, AIV, LAA, FI, EI, PI, water absorption, soundness, and CBR values of 2,65 %, 19,46 %, 10,70 %, 10,88 %, 16,15 %, 22,01 %, NP, 0,26 %, 2,09 %, and 101,98 %, respectively. At this proportion, the gradation aligns with the required ERA standard specifications for GB2 and GB3 materials. Therefore, CG up to 40 % by weight with 60 % RCA is viable for road base course construction, especially when readily available or nearby.

EXPLORING THE POTENTIAL OF RED ASH AND MARBLE CHIPS AS ALTERNATIVES IN BASE COURSE MATERIAL VIA BLENDING WITH CRUSHED STONE AGGREGATE

Despite its abundance, red ash has compaction issues owing to its lightweight, rough circular surface, and high porosity. The usage of conventional base course materials across the country incurs shipping expenses and takes time, slowing down projects because they are only widely available in limited areas across the country. In this study, non-probably sampling approach was used to examine the potential for employing red ash and marble chips as an alternative base course material by mixing them with crushed stone aggregate (CSA). In order to accomplish the goal of this study, an experimental test was conducted via trial and error, focusing on the mechanical stabilization of red ash and marble chips. Their physical characteristics were subsequently assessed through laboratory testing. In the laboratory, nine (9) samples of red ash and marble chips blended with CSA in varying percentages (0, 5, 10, 15, 20, 25, and 30 percent) were examined. The laboratory test results showed that 100% red ash and marble chips gave; CBR, SG, AIV, ACV, LAA, FI, EI, water absorption, and soundness: 55.4%, 2.38%, 18.20%, 26.34%, 19.69%, 5.59%, 12.09%, 2.5% and 13.80 and 83.6%, 2.63%, 19.70%, 26.41%, 19.75%, 23.2%, 16.9%, 1.24% and 12.22 respectively. Several of these test results align with the Ethiopian Road Authority (ERA) standard specifications; however, the findings from the CBR, water absorption, and soundness tests do not. Thus, mechanical stabilization was employed to improve the samples' physical characteristics. Experimental results are obtained by mixing 20% red ash, 20% marble chips, and 60% CSA. The values for CBR, SG, AIV, ACV, LAA, FI, EI, water absorption, and soundness are 102.5%, 2.55, 14.23%, 19.84%, 7.92%, 18.61%, 20.77%, 0.83%, and 7.38, respectively. The CBR, water absorption, and soundness characteristics all meet the necessary ERA standard specifications for crushed weathered rock (GB2) and natural coarsely graded granular materials (GB3) at this particular proportion. Hence, it is recommended to incorporate red ash up to 20% and marble chips up to 20% by weight, alongside 60% CSA, for constructing road base courses, particularly when these materials are reasonably accessible from construction sites and are widely available in the area.

Geopolymer as stabilising materials in pavement constructions: A review

Construction in weak or soft soil needs soil stabilization. The most popular stabilizers are fly ash, cement, and lime to stabilize a road pavement's base, subbase, and subgrade courses. Cement is a crucial component of many construction materials for the entire world. However, it has particular environmental problems and the long-term durability of soil-cement combinations, which impacts life. The production process of this cement requires a tremendous amount of energy and produces a large quantity of carbon dioxide, resulting in environmental pollution. To get out of this problem, researchers have found an alternative by using geopolymers. This paper gives a state-of-the-art review of geopolymer-based soil stabilization for road pavements. It discusses how weak and soft soils are stabilized with waste materials forming geopolymers, thus enhancing their properties to use as pavement materials. The paper also reviews the utilization of various wastes as base materials for geopolymer towards stabilizing soil for road construction as circular construction. Towards end the paper highlighted the future research agendas.

Effects of sodium chloride crystallization on shear characteristics of road base aggregates under unsaturated state

The precipitation and intrusion of sodium chloride into pavement structures is inevitable in coastal regions, which can affect the mechanical properties of the road base courses. To investigate this problem, samples with sodium chloride solution were cured in a thermostatic chamber until they reached the specified states of sodium chloride precipitation within the pores. A critical crystallization degree ( ωc) was discovered by computerized tomography scan, corresponding to the start of the formation of porous salt crust cementing the soil particles. A series of unsaturated large-scale triaxial shear tests were then conducted under various states of salt crystallization. The results showed that in the early stages of crystallization (i.e., ω < ωc), the peak stress and internal friction angle decreased with ω because of the coating and lubricating effects of salt powders, while the apparent cohesion remained constant. When ω > ωc, owing to the increasing adsorption and cementation effects of the salt crust, rapid growth was observed for the peak stress, internal friction angle, and apparent cohesion of the road base aggregates. Considering the influence of salt precipitation, a modified shear strength criterion that can predict the shear strength of the salinized road base aggregates was formulated.

Investigation of the performance of cement-stabilized magnesium slag as a road base material

The harmless, resource-saving, and large-scale utilization of magnesium slag (MS) from industrial waste has become an important topic for road research. The use of MS as a substitute for aggregate is a practical and efficient way to dispose of it. However, there is a lack of systematic research on how to standardize its use in road construction. The objective of this study was to investigate the applicability and feasibility of using MS for cement stabilized base course materials. The influence of different cement dosages, curing age, and gradation on the strength, stiffness and stability of cement-stabilized magnesium slag mixture (CMSM) was investigated, and the actual road performance of CMSM was analyzed by paving a test road. The results showed that the mechanical properties of the CMSM met the requirements for road base courses under medium-to-light traffic when the cement dosage was above 5%. The unconfined compressive strength loss rate of the CMSM was less than 13% for an immersion time of 1 to 7 days, and after 5 freeze–thaw cycles, the frost resistance coefficient of the CMSM was more than 85%. The performance of the CMSM was most affected by cement dosage and curing age, closely followed by mixture grading type. MS can enhance the development of the pozzolanic reaction, resulting in improved strength and compactness of CMSM. Overall, CMSM exhibited exceptional road performance and could reduce aggregate costs by 25% to 35%. The use of MS as an aggregate for road base courses offers a sustainable solution that not only maximizes the use of solid wastes, but also avoids the potential safety hazards and environmental pollution caused by improper disposal and stockpiling of MS.

Utilization of coal fly ash to enhance the bearing capacity of road base

Coal is responsible for the generation of around 38 percent of the power that is used throughout the entire planet. In the last two decades, there has been a rise in the number of chances for recycling and usage of fly ash from coal combustion due to its hydrophobic and cementitious properties. However, there is still limited commercialization of coal fly ash (CFA) in road construction. The focus of this research is to determine the bearing capacity of a CFA-treated crusher run used as a road base course. In order to determine the appropriate percentage of CFA, the crusher run was mixed with various percentages of Class F CFA, including 10%, 15%, 20%, and 25%. The proctor Compaction test (PCT), soaked and unsoaked California Bearing Ratio (CBR) tests, and Unconfined Compressive Strength Test (UCST) were then used to evaluate the bearing capacity of the CFA-treated crusher. The result shows that as the percentage of CFA increased, the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) decreased compared with the control specimen. The soaked and unsoaked CBR of the CFA-treated crusher run with 20% CFA increased by approximately 32% and 26% respectively that of the control specimen. Therefore, it is proven that utilization of CFA up to 20% into crusher run could enhance the bearing capacity of the road base.

Investigation of the influence of bitumen emulsion and Reclaimed Asphalt Pavement content on the mechanical properties of Bitumen Stabilised Materials with high fine particle content

Cold recycling technology is gaining popularity as an economically and environmentally effective way of pavement rehabilitation. The main benefits of the use of cold recycling mixtures (CRMs) in road base courses are associated with the reduction of raw materials consumption by replacing them with recycled materials such as Reclaimed Asphalt Pavement (RAP), as well as the decrease in energy consumption during production and paving compared to Hot Mix Asphalt (HMA). Bitumen Stabilised Materials (BSMs), described as non-continuously bound CRMs, exhibit granular and viscoelastic materials properties due to the presence of local bituminous bonds and a reduced amount of cement. Their mechanical properties are still being investigated.In this paper, Bitumen Stabilised Materials with bitumen emulsion (BSM-E) were investigated. Mixtures characterised by high fine particle content and designed with different Reclaimed Asphalt Pavement (RAP) and bitumen emulsion contents were subjected to Indirect Tensile Strength (ITS) tests at 25°C. TSR water resistance parameter for the mixtures was calculated. Test results were analysed using two-way ANOVA statistical tests.The laboratory test results showed that BSM-E mixtures exhibited different trends of an increase in ITSdry, ITSwet and TSR values as a function of bitumen emulsion content, depending on the RAP amount used. The statistical significance of the effects of bitumen emulsion content, RAP content, and the interaction between these two factors on the tested ITS values was proven.

Mechanical Properties, Dry Shrinkage, and Water Penetration of Reusing Fine and Ultrafine Recycled Concrete Aggregate.

The effect of fine and ultrafine recycled concrete aggregate (RCA) on road construction still lacks investigation. This study investigates the properties of fine and ultrafine RCA, further, the influence of the different proportions of ultrafine RCA on the long-term performance of the designed matrix. The fine and ultrafine RCA are thoroughly characterized. Simultaneously, the mechanical properties, shrinkage properties, and water penetration of the designed matrix are evaluated. The results indicate that RCA shows low density, high porosity, and high water absorption. Furthermore, elevated ultrafine RCA contents result in higher compressive strength of up to 43.14% at 90 days and higher resistance of water penetration of up to 50% at 28 days due to the refined microstructure. However, higher drying shrinkage is observed with higher ultrafine RCA, which is associated with the high water absorption of the ultrafine RCA. The understanding of the utilization of ultrafine RCA in the construction of road base courses has been explored.

Effect of Metakaolin on Strength Properties of Lateritic Soil Intended for Use as Road Construction Material

An excellent all-weather road is essential in providing reliable transportation services that comprise social and economic development elements. However, in most cases, the road has to be constructed on a soft foundation soil where large deformations usually occur, which causes increases in maintenance costs and leads to interruption of traffic service, especially during the wet season. It is necessary to stabilize or improve the in-situ soils. This study explores the potential of using metakaolin to improve the geotechnical properties of lateritic soil for road construction materials. The soil classifies as A-6(4) and CL according to the American Association of State Highway and Transport Officials and the Unified Soil Classification System. The soil was treated with 5, 17.5 and 30 % concentrations of metakaolin by dry weight and was compacted using three compaction energies: British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) tests were carried out to evaluate the effect of metakaolin on the soil investigated. Results showed a general improvement in the engineering properties of the soil with an increase in metakaolin content, particularly when compacted at the BSH energy level. However, the results did not meet the 1500-3000 kN/m 2 7 days UCS criterion stipulated by the Nigerian General Specification for road base courses. However, 30 % lateritic soil/metakaolin blended soil compacted using WAS and BSH energy levels suffice for use as sub-base in road construction, having met the 750-1500 kN/m 2 7 days UCS criterion stipulated by the Nigerian General Specification. The Peak CBR value for the treated soil, compacted using the three energy levels of BSL, WAS, and BSH, occurred at 30 % metakaolin concentration with corresponding soaked CBR values of 17, 23 and 31 %. The Nigerian General Specification recommends a nominal strength criterion of a soaked CBR value of 30 and 80 % to be attained by material to be used as sub-base and base course in road construction. Based on the above criterion, only the 30 % metakaolin treated blend compacted at the BSH energy level met the 30 % requirement for sub-base materials.

Monitoring road base course construction progress by photogrammetry-based 3D reconstruction

Infrastructure industry is a significant contributor to a country's economy, but it is beset by cost overruns and delays. Therefore, project monitoring is essential to determine project performance by comparing the site progress to the schedule baseline. However, manual tracking lacks the precision and efficiency. The ability to quickly and accurately identify differences is important to implement essential measures to reduce the impact of delays. This paper aims to build a technology-assisted progress monitoring framework for road base course construction. A case study is carried out on a road construction site using an Unmanned Aerial Vehicle to capture as-built data in a timely manner. Photogrammetry is used to generate point cloud model as the 3 D geometrical representative of the site. Percentage of Completion is computed as an indication for the progress of the construction along with the location of the work performed and the quantity of the material used. The framework produced a detailed and accurate construction progress report with evidence support from point cloud data which allows the visualization of the actual construction site in three dimensions. The findings reveal that the framework enables accurate and efficient tracking of road base course construction progress as well as schedule comparison.

Assessment of Modulus Attenuation of Cement and Lime-Fly Ash Semi-Rigid Road Base Materials

For asphalt pavement structures, semi-rigid road base course has to sustain repeated high-axle load during its service life and the performance of semi-rigid road base materials directly influences the durability of pavement structures. The dynamic compressive resilience modulus of two commonly used semi-rigid road base materials, cement stabilized aggregates (CSG) and lime-fly ash stabilized aggregates (LFSG) were evaluated at different frequencies using a Universal Testing Machine (UTM). The results showed that LFSG had higher dynamic modulus than that of CSG and the load frequency had less influence on the dynamic modulus of these two semi-rigid road base materials. The four-point bending test was applied to measure the flexural-bending strength and the fatigue life of these two semi-rigid materials. A higher flexural-bending strength of LFSG indicated its better bearing capacity than that of CSG. The fatigue life of LFSG and CSG decreased with the increase of stress–strength ratio and the LFSG performed better in terms of fatigue resistance. The fatigue damage models of CSG and LFSG based on Stress-Life (S-N) curve are established. As per incremental-recursive mechanics, a general modulus degradation model was established and verified by the results of full-scale accelerate loading test. This model cannot only be used to predict the fatigue deterioration of semi-rigid road base materials under different stress levels, but is also able to calculate the current bending elastic modulus based on its initial modulus value.

High industrial solid waste road base course binder: Performance regulation, hydration characteristics and practical application

The recycling ratio of industrial solid waste, e.g., steel slag (SS), phosphogypsum (PG) is still comparatively low in developing countries. This work aims to utilize industrial solid waste in a sustainable slow-setting slight-expansive road base course binder (RBCB) production involving the performance regulation, hydration characteristics and practical application. The results indicates that RBCB obtained the ideal retarding effect without additional retarder and avoided the strength loss which caused by the fast hardening during the rolling compaction process. The relatively high content of PG preferably stimulated the pozzolanic activity of fly ash (FA), and more effectively compensated the shrinkage through inhibiting the conversion of AFt to AFm in the later hydration stage. In addition, SS adjusted the setting time, improved the strength and regulated the expansion ratio of RBCB. Each kilometer of road base course absorbed 688.8 t solid wastes and saved 6.53% cost of materials compared with P·S 32.5 (Portland slag cement, strength grade is 32.5) in practical application. Excellent pavement performance, obvious environmental and economic benefits were achieved in the field experiment of RBCB containing high solid wastes. This investigation provides a promising and value-added way for the utilization of various original solid waste.

Case Study on the Effect of Recycled Asphalt Layer Parameters on the Bearing Capacity of the Pavement

Numerous ways to use recycled asphalt (RA) in the road base course will provide both environmental and economic benefits, allowing to recycle and utilise this initially waste material in road or pavement reconstruction projects. However, the properties and parameters of RA necessary for the application of reclaimed asphalt pavement (RAP) in a new pavement structure in most cases are not detectable in the design stage, which complicates design and construction process. The purpose of this paper is to study possibilities for evaluating the performance and parameters of RA, as well as to review the possibilities, methods and applications for RA testing. Data for this case study were obtained from recently completed road structures in the form of FWD measurements, together with lab explored parameters of drilled pavement cores. Based on that data, the relationships between the main pavement structural parameters, such as modulus on the surface of the pavement, compressive strength of RA core segment, thickness of bound layers and back calculated modulus were examined. On the way to exploring different analytical approaches, two approximation models were developed and compared, using the obtained data: by directly approximating the obtained data and after processing them with artificial neural network (ANN).

Unconfined Compressive Strength of Chemical Stabilised Recycled Asphalt Pavement (RAP) and Crusher Run Mixture for Road Base Course Application

Due to depletion of natural resources and rising awareness of environmental preservation, the road construction practitioners are always seeking alternative materials and technology to make the industry more sustainable in pavement construction. This paper examines the chemical stabilisation of Recycled Asphalt Pavement (RAP) materials and Crusher Run (CR) mixtures with a proprietary chemical binder as a potential way forward. The materials were mixed in ratios of 0, 25, 50, and 75% RAP replacement of CR, with the chemical stabiliser added in dosages between 2-4% per dry weight of the materials. Compacted and cured for 7 days as per requirements of the local authority, the samples were then subjected to the Unconfined Compression Test where the strength UCS (qu7) was recorded. Triple samples were tested for each case to ensure reliability of the results obtained. It was found that with RAP substitution, the UCS is inversely proportionate to ratio RAP used in the mixture, while UCS is directly proportional to dosage chemical added. Besides, It is technical viable to partially replace CR with RAP during chemical stabilization for road base course application.

Study of the Stiffness of the Bitumen Emulsion Based Cold Recycling Mixes for Road Base Courses.

The benefits of the use of cold recycling mixtures (CRMs) in pavement rehabilitation are associated with both the reduction of natural resource consumption by replacing them with recycled materials and the reduction of energy consumption during their production and paving. The evolution of the stiffness of CRMs in road construction and the fatigue life of pavements with CRM base layers are still being investigated. In this paper, CRMs with 1% cement content, called bitumen-stabilized materials with bitumen emulsion (BSM-Es), were examined. Mixtures that were differentiated in terms of Reclaimed Asphalt Pavement (RAP) content, as well as the amount and type of bitumen emulsions, were subjected to indirect tensile stiffness modulus (ITSM) tests at 5 °C, 13 °C, and 20 °C. The thermal sensitivities of the BSM-E mixtures were analyzed. BSM-E mixture stiffness modulus levels at various temperatures were determined using a statistical approach. On the basis of the results obtained, a discussion on the mechanistic-empirical design of flexible pavements with BSM-E base layers is presented. The potential benefits of using BSM-E materials in road construction in certain aspects of pavement life are indicated.

EXPERIMENTAL STUDY ON APPLICATION OF MARBLE WASTE AS CONVENTIONAL AGGREGATE FOR BASE COURSE MATERIALS

Recently, highway and construction industries utilize a substantial quantity of conventional aggregates. The increasing demands for conventional aggregate cause an increase in the cost of construction, reduction of natural resource, and continuing deterioration of the earth's surface. On the other hand, the waste generated from the marble industries during the process of cutting and polishing was increasing day by day all over the world. In Ethiopia, the use of Marble Waste Aggregate materials in road construction as a base course material was not well-known, and it was simply wasted at every place where the marble production was continuing. Therefore, this paper focused on evaluating the possibility of using marble waste aggregate as conventional aggregate in the base course layer of flexible pavements by experimental method. To achieve the objectives of the research, mechanical stabilization and laboratory tests have been carried out at different percentage replacement of Conventional Aggregate by (0%, 20%, 40%, 50%, 60%, 80%, and 100%) of Marble Waste Aggregate weights. Marble wastes materials are collected from Burayyu city, Alisha marble processing industry. The laboratory test results for MWA indicated SG, ACV, AIV, LAA, Flakiness Index , Elongation Index, Plastic Index, Water Absorption, and CBR of 2.74%, 23.63%, 26.21%, 27.03%, 26.48%, 13.29%, Non Plastic, 0.50% and 73.3%, respectively. These test results fulfilled the ERA standard specification for some tests, and it showed marginal quality values to the standard specification for GB2 and GB3 base course materials. CBR and gradation test results shown failure to meet the standard specification. Thus, mechanical stabilization was done to improve the mechanical and physical properties of Marble Waste Aggregate. Blending of 80%MWA with 20% CA results in SG, ACV, AIV, LAA, Flakiness Index, Elongation Index, Plastic Index, Water Absorption, and CBR of 2.83%, 18.2%, 21.52%, 22.58%, 23.79%, 16.29%, Non Plastic, 0.80%,and 82.5% respectively. At this proportion the gradation also observed to fit with the required ERA standard specification of GB2 and GB3 materials. Therefore, the use of marble waste aggregate up to 80% by weight is recommended for road base course layer, when it is found near to the construction site and in places where the materials are abundantly available.

Recycling of cement kiln dust from cement plants to improve mechanical properties of road pavement base course

In the study, the potential of reuse of cement kiln dust (CKD) to improve the stability properties of the base course of road pavements was investigated. CKD was characterized chemically and physically. The results revealed that addition of CKD improved the mechanical properties of the base course significantly. The results showed a significant increase in California Bearing Ratio, from 234.5% measured for untreated base to 334.4%, 362.7% and 384.6% for CKD content of 5%, 15% and 25%, respectively. In terms of chemical composition, CKD is similar to cement. Scanning electron microscope images showed that the average particle size is approximately 0.5 microns. The granules are mainly spherically shaped, with cubic crystals of sodium and potassium salts. The leachability study of CKD in the base course revealed that heavy metal concentrations in CKD are fixed and insoluble in water.