Pavement Base Course Research Articles

Development of a sustainable stabilized macadam road base using steel slag as supplementary cementitious material

As the main waste product of iron and steel industry, steel slag possesses considerable cementitious activity, making it a promising alternative to cement in Cement Stabilized Macadam (CSM). However, CSM was inevitably exposed to groundwater and rainwater when served as the pavement base course, leading to concerns over poor early strength and potential pollutant leakage, which are the main factors that may hinder the widespread utilization of steel slag in CSM base. To address these issues, this study investigated the feasibility of using steel slag powder to produce CSM. Steel Slag Powder-Cement Stabilized Macadam (SSCSM) samples were prepared and the hydration products, microstructure, mechanical properties, water damage resistance and heavy metal ions leaching behavior were investigated. The results show that the nucleation effect of steel slag powder accelerates the early hydration, but the C-S-H produced by hydration is not sufficient to form a stable hydration product network, so the microstructure of SSCSM is looser than that of CSM. The addition of steel slag powder improved the shrinkage performance of SSCSM, and the mechanical properties and heavy metal ion leaching concentration of SSCSM meet the engineering application requirements when the steel slag powder replacement level does not exceed 30 %. It was also found that the addition of steel slag powder promoted the development of pores in SSCSM samples after dry-wet cycles, resulting in the reduction of water damage resistance. Compared with conventional CSM, the use of SSCSM can not only reduce 4 % of raw material cost and 23.5 % of equivalent CO2 emission, but also mitigate the heavy metal ions leaching risk associated with steel slag, making it an effective and sustainable solution for steel slag recycling.

Stabilization of lateritic soil with Portland cement and crushed granite for pavement base courses

The aim of this work is to propose reconstituted materials, by cement-based improvement of lateritic gravels and joint cement improvement and lithostabilization, that are technically suitable for use in base courses. The study focused on two (02) different lateritic gravels, LG1 with a fine content of 24% and LG2 with a fine content of 15%. For lithostabilization, 0/25 granite crushed stone was used and the cement used was CEM II/B-LL 42.5. For cement improvement, three (03) cement contents (1%; 1.5% and 2%) were studied, and for joint stabilization, the granite crushed content was set at 10%, with only the cement content varying by 1%, 1.5% and 2%. The mixes were obtained by adding the cement mass calculated from the total gravel mass collected and the cement rate studied to the raw gravel or to a mixture of 90% gravel and 10% granite crushed stone. The results of physical-mechanical tests such as the Atterberg limits, Modified Proctor and California bearing index of stabilized materials were analyzed in comparison with the initial values of raw materials without stabilization. The results show that cement increases the plasticity index but improves the bearing capacity of lateritic gravels better than joint stabilization. However, joint stabilization does improve gravel bearing capacity compared with untreated raw gravel. For use as a base course in accordance with CEBTP specifications [3], in addition to the 10% granite crushed content, LG1 must be upgraded to at least 1.5% cement and LG2 to 1%.

Effects of Ground Coal Bottom Ash and Calcium Chloride on the Compaction Properties of Cement Stabilized Cold In-Place Recycling (CIPR) Pavement Base Course

Effects of Ground Coal Bottom Ash and Calcium Chloride on the Compaction Properties of Cement Stabilized Cold In-Place Recycling (CIPR) Pavement Base Course

Enhancing the Geotechnical Properties of Black Cotton Soil using Terrazyme

Abstract: The cost, performance, durability, and time of every project are its most crucial components. Black cotton soil, due to its strong swelling and shrinkage qualities, also known as expansive clay soil and regur soil, presents considerable difficulties in building and agriculture. Building on black cotton soil has its challenges, including foundation and road settlement, among others. Due to the shortcomings of conventional soil stabilizing technologies, new ways for enhancing the engineering properties of soil are being investigated. There is a demand for the creation of novel techniques to enhance the geotechnical properties of soil due to the inefficiency and high costs associated with conventional methods. Study examines the use of terrazyme, a state-of-the-art enzymatic soil stabilizer, to improve the geotechnical properties of black cotton soil, optimum moisture content, maximum dry density, liquid limit, plastic limit, plasticity index, and CBR test, which are used for pavement base courses, sub-base courses, and sub-grades.

Performance of Alkali-Activated Fly Ash Stabilized High Percentage RAP Aggregates as a Pavement Base Course: Laboratory and Field Perspectives

Performance of Alkali-Activated Fly Ash Stabilized High Percentage RAP Aggregates as a Pavement Base Course: Laboratory and Field Perspectives

Assessment of performance characteristics of pavement base course incorporating reclaimed asphalt pavement and asphaltenes

Asphalt pavement is demolished and milled at the end of its service life, resulting in an enormous amount of waste material known as reclaimed asphalt pavement (RAP). Using cold recycling techniques, it is possible to reuse RAP for base course construction. However, using a high amount of RAP could have negative effects on the mechanical properties and durability of the base course. In this study, to improve the performance of asphalt emulsion recycled base course prepared with RAP, asphaltenes derived from Alberta oil-sands bitumen was added to the mixture. The performance properties of the selected mixtures were investigated at high, intermediate, and low temperatures. Testing results and statistical analysis revealed that asphaltenes enhances the high and intermediate temperature performance of the modified mixes significantly. The low-temperature creep compliance of asphaltenes-modified mixtures was slightly lower than the unmodified mixtures, however, the low-temperature properties of the modified mixes were not significantly affected.

Utilization of recycled concrete aggregates for pavement base courses – A detailed laboratory study

Pavement construction and maintenance have become prevalent globally due to increasing traffic volumes and higher vehicular axle weights, driven by population growth and technological advancements. However, the extensive reliance on natural resources raises concerns about their long-term availability and sustainability. An emerging trend in construction involves the application of alternative materials, such as demolished waste and industrial by-products, as substitutes for natural materials like aggregates. This study examined strength properties, including unconfined compressive strength (UCS), flexural strength, elastic modulus, indirect tensile strength (ITS) and the performance aspects of durability, shrinkage, and fatigue. Cement stabilized recycled concrete aggregate (CSRCA) mixes were prepared by varying the percentage of natural coarse aggregate (NCA) and recycled concrete aggregate (RCA) from 0% to 100% and cement content from 3% to 7%. The experimental findings demonstrated that the cement content had a more significant impact on the strength and performance characteristics of CSRCA mixes than RCA content. The mixes with RCA replacement up to 50% and a cement content of 5% satisfy the strength and durability criteria recommended by IRC 37. A higher proportion of RCA was found to have a detrimental effect on mechanical properties and fatigue characteristics. It was found that the CSRCA mixes with 50% RCA replacement to NCA can be used as a base layer instead of a conventional cement-treated base (CTB) for flexible pavement.

Variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement and marginal lateritic soil blends in tropical climate

This article investigated the effects of temperature on the variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) as a sustainable bound base course of flexible pavement. A site investigation to assess the temperature profile of highway pavement in the northeast of Thailand was conducted to find the temperature variation of pavement structure in tropical country. Laboratory tests including unconfined compressive strength (UCS), modulus of elasticity (E50), and indirect tensile strength (ITS) tests were conducted on cement-stabilized RAP and MLS blends at varying mix proportions and temperatures. It is evident that the temperature significantly affects the strength and stiffness of specimens containing RAP due to the presence of bitumen covering the RAP aggregate. The additional MLS and cement can reduce the viscoelasticity of RAP aggregate. The strength reduction due to the temperature is characteristic of the RAP mixtures with MLS and cement. The normalized relationships of UCS and temperature and the empirical correlations between E50 and ITS versus UCS were presented. This set of relationships is a valuable tool for the mix design of cement-stabilized RAP and MLS blends as a bound base course in tropical countries.

Rock Aggregate Size Influence on Physical Degradation of Laminate Sedimentary Rocks in Flexible Pavement

Rock aggregates are the most fundamental material of highways, railroads, and other construction activities. Degradation of aggregate is the disintegration of aggregate due to the wheel load and moisture saturation causing loss of support in unbound granular layer and reduction of drainage in pavement materials. Sedimentary rocks from different quarries were evaluated to determine the influence of aggregate size on the degradation of materials. This study is to find out the effect of size on physical parameters of aggregate used in flexible and rigid pavement. The performance of river rock and crushed rock physical properties has been tested and compared. In order to determine the effect of aggregate size on their degradation properties, different sieve ranges were selected. The sieve sizes are graded into four categories according to Indian Standard sieve: R1 (20 mm-16 mm), R2 (16 mm-12.5 mm), R3 (12.5 mm-10 mm), and R4 (10 mm-4.75 mm) for degradation test such as, aggregate impact value (AIV), aggregate crushing value (ACV), water absorption (WA) and weathering test such as soundness and slake durability. It is observed that the larger size of aggregate has given better resistance against impact load, abrasion, weathering action and water absorption compare to smaller size over the same volume of rock. The rate at which aggregate degradation occurs is influenced by size. Along with the wheel load, environmental factors including moisture and temperature changes are the primary causes of the early degradation of aggregate. The river rock has a better resistance against degradation and weathering action as it has lesser lamination (a small scale sequence of fine rock layer). Adoption of larger size aggregate in the pavement base course is suggested to withstand the effect of environmental action and wheel load, especially on the friable and quickly disintegrated rock. Arating value, rating index and regression equation have been developed for aggregate degradation. Keywords: Particle Size, Properties of Rock, Weathering, Slake Durability, Degradation Index

Experimental study on iron ore tailings sand and municipal solid waste incineration fly ash used in semi-rigid base of asphalt pavement

In order to co-dispose and effectively utilize the bulk solid waste of iron ore tailings (IOT) sand and hazardous solid waste of municipal solid waste incineration (MSWI) fly ash, a study on using them in pavement base course is carried out in this paper. In this work, cement and fly ash (with a ratio of 1:3) were used as stabilizing materials. IOT was used as aggregate, while MSWI fly ash was used as a part of the cementitious material or as a partial replacement for the aggregate in the road base. The samples were tested for unconfined compressive strength, indirect tensile strength, drying shrinkage, temperature shrinkage and toxicity leaching. XRD and SEM-EDS were also used to analyze the changes in structure and properties. The results showed that the samples incorporated with washed ash instead of IOT had greater strength development. The unconfined compressive strength of the unconstrained samples decreased after partially replacing cement and fly ash. At the same time, the drying shrinkage rate became larger compared to the group without adding MSWI fly ash. The leaching results of toxic substances showed that most of the lead and zinc contents were easily diffused into the environment. However, after cement hardening, the leaching rate of various heavy metals was significantly reduced, which was far below the threshold of national standards.

The effect of flakiness and elongation index on the compressive and splitting tensile strength of cement treated aggregate crushed stone

The reality of road construction shows that, for routes with unfavorable mining conditions, the aggregate crushed stone bases for road pavement are often unstable, unable to meet the requirements for load-bearing capacity and load distribution to lower layers, leading to various types of deformation and damage on the road surface, such as rutting, cracks, and potholes. Using cement treated aggregate crushed stone bases for road pavement is an effective solution to address this problem. This article presents the research results on the effect of the flakiness and elongation index on the compressive and splitting tensile strength of 5% cement treated aggregate crushed stone. The study shows that when the flakiness and elongation index increased from 14% to 22%, the compressive and splitting tensile strength at 14 days of the age of 5% cement treated aggregate crushed stone decreased by 36,54% and 31,02%, respectively. The 5% cement treated aggregate crushed stone with flakiness and elongation index ranging from 18% to 22%, as studied in this research, still meets the strength requirements for use as pavement base course for class 3 roads and lower.

Experimental Study of Pervious Concrete for Application to Pavement Base Course

Experimental Study of Pervious Concrete for Application to Pavement Base Course

Performance assessment of three alkali-treated fly ashes as a pavement base-course material

Alkali-treated fly ash can efficiently serve as a construction material for various purposes. The efficacy of these alkali-treated fly ash must be critically studied for their proper usage in real-life scenarios. In the present study, the effectiveness of an alkali-treated low calcium fly ash (Class F) as a pavement base course material in the pre and post-construction period of the pavement has been investigated. The low calcium fly ash (Class F) was treated with three different alkalis, namely sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2), to study the influence of alkali type, its dose and curing period on the compressive strength and permeability characteristics of alkali-treated fly ash samples as these properties would prominently influence its behavior as a base course. In addition, the microstructural study of different alkali-treated ash samples was done to correlate the microstructural developments with these engineering properties. It was observed that 12% NaOH-treated fly ash samples, 16% KOH, and 16% Ca(OH)2-treated fly ash samples at 28 curing days show an optimum compressive strength value for a stabilized base material in pavements as per various guidelines. Finally, the usability of these optimized alkali-treated fly ash samples as a base material was investigated through a numerical study of a simple two-layered pavement structure. The surface and interface deformations of the pavement under various loading conditions revealed that these optimized alkali-treated fly ashes serve as a better base course than granular material. Also, of the chosen three alkali-treated fly ashes, optimized Ca(OH)2-stabilized fly ash performs comparatively better than others in terms of compressive strength and resisting deformation for these typical pavements.

Preparation of controlled low-strength materials from alkali-excited red mud-slag-iron tailings sand and a study of the reaction mechanism.

To address the low utilization of fines in iron tailings sand (IOTs), a controlled low-strength material (CLSM) was prepared from a combination of fine IOTs and red mud (RM) slag. The 7-day unconfined compressive strength (7-d UCS), slump and cost were used as evaluation indicators, and 16 sets of tests were designed with the Box-Behnken design (BBD) response surface method. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) were used to study the microscopic morphology and reaction mechanism of the CLSM samples made with the optimal ratios. The results show that the best matching ratio for the alkali-activated RM-slag-IOTs CLSM was a sand ratio of 0.797, an NaOH dose of 3.667% and a mass concentration of 80.657%, and the 7d-UCS, slump and cost indicators verified the feasibility of applying the CLSM to the base course of pavement. Alkali activation of the CLSM also showed that the RM-slag cementation system produced new substances. Internal calcium-silicate-hydrogel (C-S-H) and calcium-aluminosilicate-hydrogel (C-A-S-H) agglomerates were the main sources of strength, and hydration products were interwoven to form a dense structure with crystals as the framework and gels as fillers.

Evaluation of Strength Properties of Sand Stabilized with Wood Fly Ash (WFA) and Cement

The article describes the laboratory evaluation of mixtures of sand modified with wood fly ash (WFA) and additionally stabilized with different amounts of cement. Laboratory research includes determining the California Bearing Ratio (CBR), compressive and indirect tensile strengths of the mixtures, and the resistance of mixtures to freezing/thawing cycles. The aim of the research is to determine if WFA, an alternative material, can improve sand bearing capacity and contribute to strength development while reducing necessary cement amounts and satisfying the technical regulation for use in pavement base courses. The test results obtained show that WFA has a considerable stabilization effect on the sand mixture and improves its load bearing capacity. By adding a small quantity of the cement, the hydraulic reaction in the stabilized mixture is more intense and results in greater strengths and an improved resistance to freezing. The test results show that, by replacement of part of the sand with WFA (in the quantity of 30%), greater strengths can be achieved in relation to the mixture of only sand and cement. Additionally, the content of cement necessary for the stabilization of sand (usually 8–12%) is considerably reduced, which enables cost savings in the construction of pavement structures.

Airport Pavement Stiffness Monitoring and Assessment of Mechanical Stabilization using Bender Element Field Sensor

The bender element (BE) field sensor is a newly developed embedded pavement instrumentation that measures shear wave velocity to estimate constructed layer moduli of unbound aggregate bases and subbases. This paper presents findings related to monitoring stiffness characteristics of airport pavement base courses instrumented with BE field sensors and tested under full-scale accelerated pavement testing during Construction Cycle 9 (CC9) of the National Airport Pavement Test Facility (NAPTF) by the U.S. Federal Aviation Administration (FAA). The CC9 aggregate base courses were constructed following FAA’s P-209 specification for a geosynthetic experiment using a biaxial geogrid installed at the bottom of the 8-in. (203-mm) thick base in the north test section, while the control pavement in the south test section was built without a geogrid. Two BE field sensors were installed in the north and south test sections approximately 1 in. (25 mm) above the base–subbase interface. Multiple stages of aircraft gear loads, including static dual-gear, dynamic slow-roll (moving wheel), and dynamic proof-roll, were applied to the test sections. BE field sensor data collected throughout multiple loading stages were used to investigate the stiffness characteristics of the pavement base. These preliminary tests conducted at the NAPTF CC9 experiment revealed the effects of static and dynamic aircraft gear loads on the stiffness of the aggregate base layer and how confinement influenced the moduli of the geogrid-stabilized base. Further, previously observed anti-shakedown effects caused by vehicle load wander could be quantified through changing base course modulus and deformation behavior from the BE field sensor data analysis.

Asserting the Applicability of Copper Slag and Fly Ash as Cemented Base Materials in Flexible Pavement from a Full-Scale Field Study

This research made innovative use of copper slag and fly ash in the construction of a cemented base course of flexible pavement. A full-scale field study evaluated the structural and functional performance of flexible pavement test sections constructed using various combinations of copper slag and fly ash (Class F or Class C) with and without lime. Various performance parameters, namely deflection basin parameters, dissipated energy, back-calculated elastic modulus, service life ratio, and roughness index, were evaluated for flexible pavement test sections constructed with 250-mm-thick conventional granular base [wet-mix macadam (WMM)], 150-mm- and 250-mm-thick copper slag–Class F fly ash–lime (CFL) (70% copper slag +23% Class F fly ash +7% lime) and copper slag–Class C fly ash (CCF) (40% copper slag +60% Class C fly ash) base layers. Falling weight deflectometer tests and bump integrator tests were performed in situ; laboratory tests, namely unconfined compression and resilient modulus tests, were performed on core samples. The average elastic moduli, back-calculated from six FWD tests conducted over 15 months after construction, for CCF and CFL base were 430 and 602 MPa, which are more than 3 times that of WMM. Significant waste utilization up to 1,348 tons of copper slag and 945 tons of fly ash per kilometer length of road can be achieved by using CCF and CFL mixes in base layers of flexible pavement with a service life ratio as high as 1.78 and cost efficiency of 17.4%.

Performance comparison of asphalt emulsion stabilized granular base modified with cement or asphaltenes

Asphalt emulsion is a common material used for pavement base course stabilization, and cement is usually added as an active filler to improve the stability of asphalt emulsion mixtures further. However, using cement in these mixes has several drawbacks, including high material costs and environmental issues. On the other hand, asphaltenes is a waste by-product derived from the processing of Alberta oil-sands bitumen that could be used for the same purpose. This investigation compares the impact of cement and asphaltenes as additives to asphalt emulsion-stabilized layers. To compare the performance properties, cement- and asphaltenes-modified mixtures are prepared at different concentrations. The performance properties of the modified mixtures are investigated by conducting a series of tests including Marshall stability, indirect tensile strength, IDEAL-CT, and tensile strength ratio. In addition, to evaluate low-temperature cracking resistance of the mixtures, indirect tensile strength test is conducted at 0 °C and –10 °C.

An experimental investigation on geotechnical properties of a clayey soil stabilised with lime and zeolite in base and subbase courses

Zeolite is often exploited to reduce the consumption of lime in the treatment of problematic clays and to help further enhance the soil stabilisation process in pavement base and subbase courses. For the mix design of the proposed pavement materials, 8% lime was first opted, according to pH tests, as the optimum content and its different portions were then replaced by zeolite inclusion. A comprehensive set of Atterberg limits, standard Proctor, unconfined compression and unconsolidated undrained (UU) triaxial tests was performed on lime and zeolite stabilised specimens. Zeolite addition into the mixture increased the maximum dry unit weight and decreased the optimum moisture content. The least plasticity index and the highest unconfined compressive strength were attained at 25% of lime replacement with zeolite, deemed to be the optimum mixing content. Results of UU triaxial tests on the optimum mixtures also confirmed the marked improvement of shear strength parameters.

Meso-cracking characteristics of rubberized cement-stabilized aggregate by discrete element method

As a sustainable solution, embedding rubber inclusions in the semi-rigid pavement base course can ensure the consumption of a large amount of waste tire pollution and improve the mechanical properties of cement-treated base materials. The rubber modification has a potential effect on reducing the possibility of pavement reflective cracks caused by base cracking. This paper aims to investigate the meso-cracking characteristics of rubberized cement-stabilized aggregate (RCSA) mixtures and to quantitatively evaluate the influence of rubber inclusion content and particle size through numerical simulation. The rubber particle size of 0.6–4.75 mm was selected. The virtual RCSA samples were prepared by replacing similar-size aggregates with rubber particles based on the reference mixtures without rubber. Five volumetric replacement contents (20%, 40%, 60%, 80% and 100%) of three gradation ranges (0.6–1.18 mm, 1.18–2.36 mm, and 2.36–4.75 mm) were adopted. An indirect diametric tensile (IDT) simulation test was adopted to obtain the investigated performance of IDT strength, static stiffness, toughness and toughness index. The simulation results show that the incorporation of rubber inclusion has a negative effect on the IDT strength of the RCSA sample. However, material extensibility and post-peak toughness are improved and stiffness is reduced with increasing rubber replacement percentage. The optimal rubber content of the investigated mixtures should be controlled within 80% of the corresponding aggregate gradation volume, which is conducive to controlling the reduction of the overall strength and the play of the extensibility. The strength reduction and ductility improvement of modified concrete are positively correlated with the particle size of rubber inclusion. The modified RCSA mixture with a smaller rubber particle size could ensure a higher IDT strength and extensibility. For the investigated sample, the best comprehensive modification effect can be obtained using the finer rubber substitute with a particle size of 0.6–1.18 mm. The rubber inclusion acts similarly to a cavity defect, which will result in fracture preferring to occur adjacent to the rubber aggregate. Ignoring the adverse effect of strength, the practical implication of rubber incorporation is to improve the ductile behaviour of the RCSA mixture and reduce base cracking. The present numerical simulation methods have the potential to investigate the meso-cracking mechanism of RCSA. It also provides a theoretical guidance for the gradation design of rubberized mixtures.