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Reclaimed asphalt pavement (RAP) is widely utilized as a green base/subbase material. Still, this material can only be used in small amounts in asphalt concrete mixtures. Many studies have shown that a large amount of RAP replacement could make asphalt pavements less effective. The goal of this study is to evaluate the mechanical properties of asphalt concrete made with 100% RAP aggregate and crushed polyethylene terephthalate (PET) bottles. The effect of adding PET to RAP aggregate was investigated with PET contents ranging from 0% to 1.0% by weight of RAP aggregate. The improved static and dynamic performances of the RAP asphalt concrete were assessed via the Marshall stability, the strength index (SI), the indirect tensile strength (ITS), the indirect tensile fatigue (ITF), the indirect tensile resilient modulus (IT MR), and the resistance to rutting tests. The optimum PET content of 0.6% provided the best performance across all experimental testing, resulting in a 25% improvement in Marshall stability, 19% in SI, 69% in ITS, 11% in IT MR , 270% in ITF, and 80% in rutting resistance compared to 0% PET content. Furthermore, it has been determined that an increase in ITS results in a corresponding increase in IT MR , exhibiting a linear correlation. After carefully analyzing the cyclic test data, a model for fatigue distress was suggested. This study's results will aid in developing sustainable pavement options, including RAP and PET, from both an economic and environmental standpoint. • PET is used as a polymer additive for RAP asphalt concretes. • The influence of PET content on mechanical properties is discussed. • The distress model for PET modified RAP asphalt concretes is proposed. • PET increased the adhesion among aggregate and asphalt cement and also the stifness. [ABSTRACT FROM AUTHOR]

• Evaluation of compressive and flexural strengths for NRL-concrete. • Evaluation of microstructure for NRL-concrete. • Suggestion of cost-effective mix design of NRL-concrete pavement. In this research study, natural rubber latex (NRL) was used as a "green" additive to improve the flexural strength properties of concrete pavements. The mechanical compressive and flexural strengths of NRL modified concrete were investigated, using various water-to-cement (w/c) and dry rubber content-to-cement (r/c) ratios and curing times. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses techniques were used to examine the mechanical strength development of modified concrete. The results indicated that the compressive strength of NRL-concrete decreased with increasing the r/c ratio at all w/c ratios and curing times, whilst the highest flexural strengths were found at the optimal r/c = 0.58%, 1.16%, and 1.73% for w/c = 0.3, 0.4, and 0.5, respectively. The w/c ≤ 0.4 and r/c ≤ 2.31 as well as w/c = 0.5 and r/c = 0.58 to 1.73 were found to be applicable to NRL-concrete pavements, as the compressive and flexural strengths met the minimum requirements specified by the Department of Highways, Thailand. A mix design chart was proposed for NRL-concrete pavements, to facilitate the determination of effective mix ingredient based on operation and material cost to meet both economical and engineering criteria. [ABSTRACT FROM AUTHOR]

• Cement and natural rubber latex were used as a combined additive to improve studied blends. • The UCS in the three first w-d cycles was promoted by the high temperature. • The NRL film reduced the porosity and increased the particles bonding within the matrix. • The NRL additive increased the w-d cycles resistance of cement-stabilized samples. This research was conducted to assess the role of natural rubber latex (NRL) in improving the durability of cement stabilized lateritic soil and recycled materials blends against wetting–drying (w-d) cycles. 70% and 50% by weight of recycled materials, including steel slag (SS) and recycled concrete aggregate (RCA) were replaced for Lateritic soil (LS) and 5% cement by weight of dry aggregate was used in this research. The dry NRL to cement (r/c) ratios of 0%, 3%, 5%, and 10% were the influence factor that were investigated. The unconfined compressive strength (UCS), physical and weight loss, water absorption, and microstructural analysis were performed to evaluate the influence of NRL on the durability of cement-NRL stabilized SS:LS and RCA:LS by comparison with those of control cement-stabilized mixtures (without NRL). The results indicated that the UCS development of all mixtures was found to be similar in that the UCS value increased up to the third w-d cycle and gradually decreased thereafter. The microstructural analysis result indicated that the increase of UCS during the w-d cycles can be attributed to the high temperature, which promotes the moisture diffusivity of cementitious materials and thus increases chemical reaction and strength development. However, with further increase of w-d cycles, the strength reduction was attributed to the Ca2+ leaching from the cement-stabilized materials during the soaking stages and the dissolution of cementitious products. In addition, the crack propagation and extension gradually caused the crumbling of samples and microcracks, resulting in the deterioration and strength loss of samples. It was evident that the formation of the NRL films filled up the pore spaces and microcrack, acting as NRL film crack-bridging mechanism, resulting in the enhanced interparticle bonding strength and durability. [ABSTRACT FROM AUTHOR]

• Natural rubber latex is used as a polymer additive for cement stabilized recycled materials. • The influence of dry rubber to cement ratio, curing time, and soil/recycled material ratios is discussed. • The relationship between strength and microstructural characteristics is discussed. • The optimum dry rubber to cement ratio can improve the mechanical properties of the mixtures. • Polymer firms increased the interparticle bond strength and matrix of mixtures. Soil replacement with medium-graded waste materials is an effective means to improve the physical properties of marginal soil prior to cement stabilization and to minimize the input of cement at the target mechanical properties. Natural rubber latex possesses superior elastic properties, which can improve the fatigue properties of cement stabilized material. This research aims to study the influence of NRL on the strength development of cement stabilized lateritic soil (LS) and recycled aggregate blends as a sustainable pavement base. The steel slag (SS) and recycled concrete aggregate (RCA) replacement ratios of 50% and 70% were studied. The cement content of 5% by weight and dry rubber to cement (r/c) ratios of 0%, 3%, 5%, and 10% were investigated. The r/c ratio was found to be a significant effect on the compactability, unconfined compressive strength (UCS), and indirect tensile (ITS) of cement stabilized SS:LS and RCA:LS blends. The microstructural analyses using scanning electron microscopy and X-ray diffraction indicated that the degree of cement hydration of cement-NRL stabilized SS/RCA:LS blends decreased with increasing NRL content due to the retardation of thicker NRL films. However, at the optimum r/c ratio, the coexistence between cement hydration products and NRL films can reduce the pore space and enhance the interparticle bond strength, resulting in UCS and ITS development of cement-NRL stabilized blends. Although the optimum r/c ratio indicating the maximum UCS and ITS of cement-NRL stabilized SS:LS and RCA:LS sample were found to be different, the percent improvement by NRL is practically the same. The r/c ratio is a dominant factor affecting the interparticle bond strength, hence the relationship between UCS and ITS was developed, which is cost-effective and time-saving for geotechnical and pavement engineering design. The result from this research is a demonstration of the effective usage of natural rubber latex and recycled materials in sustainable pavement applications. [ABSTRACT FROM AUTHOR]

Abstract: Fly ash and biomass ash have been widely accepted as waste materials substituting Portland cement. In this paper, the role of these two ashes on the strength development of cement admixed low-swelling Bangkok clay is investigated via unconfined compressive (UC) test and thermal gravity (TG) analysis. Fly ash and biomass ash are dispersing materials, increasing the reactive surface of the cement grains. The pozzolanic reaction does not play any significant role on the strength development with time since the amount of Ca(OH)2 is insufficient to react with the ashes. The contribution of the dispersing effect to the strength development is regarded akin as an addition of cement. Based on this premise, the clay–water/cement ratio hypothesis for blended cement admixed clay is proposed for analyzing and assessing the strength development. Even with the difference in water content, cement content and ash content, the blended cement admixed clay samples having the same clay–water/cement ratio, wc /C possess practically the same stress–strain response and strength. The relationship among strength, clay–water/cement ratio, and curing time for the blended cement admixed Bangkok clay is finally developed and verified. It is useful to assess the strength at any curing time wherein water content, cement content, and ash content vary over a wide range by using the test result of a single laboratory trial. For the economic mix design (the most effective dispersing effect), an addition of 25% ash is recommended. It can save on the input of cement up to 15.8%. [ABSTRACT FROM AUTHOR]

Road maintenance projects require innovative, economical, and environmental solutions. This study evaluated recycled asphalt pavement (RAP) as a greener aggregate alternative to natural aggregate for the maintenance of asphalt concrete in flexible pavements. The mechanistic performance of warm mix and cold mix asphalt concretes using recycled asphalt pavement (RAP) was furthermore investigated in this study. The bitumen binders used were asphalt cement AC60/70 for warm mix asphalt concrete and asphalt emulsion CMS-2 h for cold mix asphalt concrete. Laboratory tests undertaken include Marshall stability and flow, indirect tensile strength, indirect resilient modulus, indirect tensile fatigue, and permanent deformation were performed to ascertain the true performance of RAP-AC60/70 and RAP-CMS-2 h mixtures as maintenance asphalt concretes. The laboratory test results of RAP-AC60/70 and RAP-CMS-2 h mixtures were compared with those of a conventional warm mix asphalt concrete using limestone and asphalt cement AC60/70. The results indicated that the overall performance of both RAP-AC60/70 and RAP-CMS-2 h mixtures was comparable to the Limestone-AC60/70 mixtures. The total material cost of RAP-60/70 and RAP-CMS-2 h mixtures was approximately 60% lower than Limestone-AC60/70 mixture. However, the RAP-CMS-2 h mixture had more advantages than RAP-60/70 in terms of maintenance operation and carbon footprint emission. The usage of RAP with both CMS-2 h for repairing pavement deterioration was found to provide a more cost-effective and greener solution. [ABSTRACT FROM AUTHOR]

• NRL was used to modify the w-d cycles of the cement-stabilized RCA. • The r/c = 10% was the optimum ratio for cement-NRL stabilized RCA. • At r/c = 10%, the UCSs after 12 w-d cycles met requirement for high-volume road. • Stable cross-linked matrix improved durability of cement-NRL stabilized RCA. In this study, natural rubber latex (NRL) was used as a polymer additive to modify the durability against wetting and drying (w-d) cycles of the cement-stabilized recycled concrete aggregate (RCA) when used as a pavement base/subbase material. This research investigated the performance of cement-stabilized RCA and cement-NRL stabilized RCA at various dry rubber-to-cement (r/c) ratios against w-d cycles. The weight loss, unconfined compressive strength (UCS), rate of deterioration, modulus of elasticity, and microstructural analysis of the studied samples before and after being subjected to w-d cycles were performed. The r/c ratio of 10% was found to be the optimum r/c ratio for cement-NRL stabilized RCA, which provided the best performance for all test results. The weight loss was found to increase, while the UCS value subsequently decreased with an increase of w-d cycles for all studied samples. At the optimum r/c ratio, the UCS results of cement-NRL stabilized after 12 w-d cycles were still higher than the minimum requirement (UCS > 2.413 MPa) for a high-volume traffic road. In addition, its modulus of elasticity was higher than that of cement-stabilized RCA samples. This indicated that the NRL additive could enhance the ductility of cement-stabilized RCA. The microstructural analysis illustrated that the formation of a stable cross-linked matrix between the cement hydration products and NRL films could improve the durability against the w-d cycles of cement-stabilized RCA as a pavement base material. [ABSTRACT FROM AUTHOR]

• Volume expansions of EAF slag after soaking under water at room temperature and 80 °C, and 2 wt% acetic acid are investigated. • Calcium acetate and calcite due to 2 wt% acetic acid soaking results in a significant reduction in the volume expansion. • CBR of the EAF slag soaked in 2 wt% of acetic acid meets the minimum requirement. • Leached heavy and hazardous elements of EAF slag are within the permissible limits of USEPA. This research aims to obtain insights into the expansion catalyzation mechanisms of (i) water at room temperature and 80 °C, and (ii) acetic acid on the Electric Arc Furnace (EAF) slag before use as aggregates in road materials. The volume expansions of the EAF slag after soaking under various conditions were investigated. The results indicated that the soaking of EAF slag in 2 wt% acetic acid was the most effective technique to minimize the volume expansion before usage as construction materials when compared to the soaking of EAF slag in water at high temperature of 80 °C. The lowest value of 0.12 % was found for the specimens soaked in the 2 wt% acetic acid for five days. The specimens soaked in the 2 wt% acetic acid for soaking times < 5 days met the criteria for safe use as aggregates in base materials according to the local road authority. The soaking of EAF slag in 2 wt% acetic acid has shown dissolved Calcium (Ca) from unstable mineralogy phases forming calcium acetate and calcite. The California bearing ratio (CBR) values of EAF slag soaked in 2 wt% of acetic acid, for all soaking periods, were slightly lower than those of the specimens soaked in water due to the lower surface particle strength caused by the acid corrosion. The CBR values were however found to meet the minimum requirement corresponding to the Thailand's Department of Highways (DH-S210/2547). Toxicity characteristic leaching procedure analysis (TCLP) of EAF slag has shown that leachates contained heavy and hazardous elements within the permissible limits according to USEPA. The outcome of this research will promote the usage of EAF slag treated with acetic acid in sustainable road applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper analyzes the strength development in cement-stabilized silty clay based on microstructural considerations. A qualitative and quantitative study on the microstructure is carried out using a scanning electron microscope, mercury intrusion pore size distribution measurements, and thermal gravity analysis. Three influential factors in this investigation are water content, curing time, and cement content. Cement stabilization improves the soil structure by increasing inter-cluster cementation bonding and reducing the pore space. As the cement content increases for a given water content, three zones of improvement are observed: active, inert and deterioration zones. The active zone is the most effective for stabilization where the cementitious products increase with cement content and fill the pore space. In the active zone, the effective mixing state is achieved when the water content is 1.2 times the optimum water content. In this state, the strength is the greatest because of the highest quantity of cementitious products. In the short stabilization period, the volume of large pores (larger than 0.1μm) increases because of the input of coarser particles (unhydrated cement particles) while the volume of small pores (smaller than 0.1μm) decreases because of the solidification of the cement gel (hydrated cement). With time, the large pores are filled with the cementitious products; thus, the small pore volume increases, and the total pore volume decreases. This causes the strength development over time. [Copyright &y& Elsevier]