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In this investigation, four types of sands as alternatives to river sand, namely, crushed sand (CS), marine sand, fine recycled concrete aggregate (FRCA), and fine reclaimed asphalt pavement (FRAP), were studied for their potential for cement-concrete pavement applications. Initially, the physicochemical and morphological characteristics of these sands were understood and later linked to the hydration kinetics and the behavior of cement-mortar systems in both the fresh and hardened states. Due to their evenly graded particle size distribution, CS and FRCA exhibited higher packing densities despite having more gradient angularity, whereas the interlocking capacity of FRAP was found to be affected by the agglomerated particles. Morphology, fineness modulus, and chemical composition of the sands were observed to be the dominating parameters affecting the hydration kinetics and thus the performance of the mortar mixes. Improving these parameters, especially the grain size distribution, could help in enhancing the potential of these sands for pavement applications. [ABSTRACT FROM AUTHOR]

Pavement engineers are paying attention to the stabilization of granular layers in the modern era of sustainable construction. A well-drained pavement can extend the service life to its design life if properly designed and maintained. The water infiltrating into the pavement causes detrimental effects and reduces the service life of the pavement. The open-graded cement-stabilized macadam (OGCSM) can act as a drainage layer in sustainable pavements. Cement cannot be considered as a long-term sustainable material due to its high carbon footprint. This paper investigated the suitability of a supplementary cementitious material, ground granulated blast furnace slag (GGBFS), as a partial replacement of cement in OGCSM, a drainage layer in pavements. The strength and permeability characteristics of the mix were studied using an unconfined compressive strength (UCS) test and specially fabricated permeameters, respectively. OGCSM was optimized at 7% cement content, and cement in the OGCSM was partially substituted with GGBFS at various replacement levels. The mix was optimized at 80% replacement of cement with GGBFS, which satisfied the specified requirements for strength, permeability, and durability. The UCS, coefficient of effective permeability, and water resistance index of the optimized mix were 2.88 MPa, 60.58 m/day and 96.33%, respectively. The morphology and mineralogy characteristics of the optimized mix were determined to justify the strength gain in cementitious mixtures. The porosity of the OGCSM mix was estimated as 25.86% using computed tomography (CT) scanned images. The subsurface drainage design was carried out using drainage requirements in pavements (DRIP 2.0) software, and the quality of drainage was rated as good. [ABSTRACT FROM AUTHOR]

This paper presents research about a mixture design method of pavement concrete coblending rubber and fiber into ordinary concrete. Mechanical-based tests regarding the compressive strength, elastic modulus, splitting tensile strength, flexural strength, and four-point bending stiffness were conducted to evaluate the flexural toughness of concrete, and a slab-based three-point bending test was designed to evaluate the bending toughness improvement of the road pavement concrete slab. The results indicated that with the increase in single rubber content, the compressive strength and elastic modulus of concrete decreased continuously. The rubber concrete specimen remained relatively complete in appearance during destruction, showing the satisfied ductile failure characteristics to pavement usage with the optimal rubber content of 10%. After adding basalt fiber (BF) or polypropylene fiber (PPF), with the increase of fiber content, the bending stiffness of concrete decreased, the corresponding deflection of peak load increased continuously, and the bending deformation capacity of concrete could be significantly enhanced. Compared with the reference group, when the rubber content is 10%, and basalt fiber content is 0.5%–2%, the equivalent initial bending strength of fiber-reinforced rubber concrete is increased by 105.4%–164.4%. In general, BF is better than PPF in improving the toughness of rubber concrete, and the optimal dosage of BF is 1% of concrete volume in this test. When loaded to the limit load, the deflection of the basalt fiber–reinforced rubber concrete slab in the middle of the bottom span was about four times higher than that of the benchmark concrete slab, the bending deformation capacity and toughness of the basalt fiber–reinforced rubber cement concrete slab have been greatly improved. From the test results, the mixture design method of flexible pavement cement concrete based on rubber and fiber coblending was proposed, which contributes to the development of flexible materials for concrete pavement. [ABSTRACT FROM AUTHOR]

An investigation was carried out to analyze the flexural fatigue performance of pavement quality concrete (PQC) of M40 and M50 grades, made with conventional materials out of which river sand (RS) was replaced by copper slag (CS) by varying concentrations to the extent of 100% by volume. Experiments were conducted in the laboratory to determine the 90-day flexural strength of PQC samples (100×100×500 mm) under four-point loading. Based on respective flexural strength, repeated loads were applied for the conduct of flexural fatigue tests of PQC specimens at stress levels of 0.7, 0.8, and 0.9, each at 1 Hz frequency. In terms of fatigue life distributions, the flexural fatigue performance of several PQC mixtures has been evaluated. Three methods were used to estimate various parameters for the Weibull distribution. It is observed that the fatigue life distribution of both M40 and M50 grade PQC mixes made with CS can be modeled by a two-parameter Weibull distribution with a correlation coefficient of more than 0.95. The estimation of fatigue life of PQC mixes has also been done at different failure probabilities. The 90-day flexural strength of PQC mixes (both grades) with CS replacing RS, increased compared with conventional PQC. Further, X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) images of PQC mixes confirmed the homogeneity of the concrete. The fatigue performance was also enhanced with CS replacing RS. The goodness-of-fit test also indicated that the present model is valid at the 5% significance level for PQC (both grades) made with CS. [ABSTRACT FROM AUTHOR]