Kumari Monu

The complete segregation of bricks from construction and demolition waste is quite challenging, leading to a reduction in the quality and suitability of recycled concrete aggregates (RCA) for rigid pavement applications. This investigation fundamentally studied the effect of brick waste (BW) on the performance of pavement quality concrete (PQC) made with RCA with the aim of identifying the tolerance limit of different BW fractions (coarse and fine) in RCA. This was achieved by mapping the fresh and hardened state behavior of PQC as well as mortar post-inclusion of BW fractions (0%–30%). Contrary to the general perception, the intermixing of BW in RCA was found to be beneficial, as it overcomes the negative effects of hydrated cement mortar paste present in RCA. The presence of BW in RCA resulted in 9%–36%, 15%–25%, and 5%–17% increases in the workability, compressive strength, and modulus of rupture of PQC, respectively. These increases have been attributed to the better morphology of BW compared with RCA and natural aggregates. In addition, BW possesses some pozzolanic reactivity, which facilitates chemical bonding between the aggregate surface and surrounding mortar paste. In fact, BW grains were found to retain moisture, leading to a reduction in the drying shrinkage of PQC by 54%–115%. Based on this study, the presence of 10%–15% BW in RCA could be considered as a threshold limit.

Cold-mix asphalt is a greener alternative to pavement construction, processed at 10–40 °C, which is typically lower than other techniques like warm-mix asphalt and hot-mix asphalt. Huge amounts of construction and demolition waste, such as broken bricks, recycled concrete aggregates, reclaimed asphalt pavement, ceramic waste, etc., are generated every year due to the acceleration in infrastructure development. The production of such massive amounts causes landfilling issues, and their disposal is a serious issue nowadays. This study examines the effect of binary blended fillers on the performance of cold asphalt mixes using emulsified binders and 50% reclaimed asphalt pavement materials. Moreover, three types of binary blended fillers (BBFs), cement, fly ash, and Stabil Road, were used at different dosages. Overall, 500 samples were prepared for the mix design, and the optimum emulsion content was determined as 11% and 9% for the CM and 50R mixes, respectively, based on the Marshall stability peak value and volumetric properties such as voids in the mineral aggregates, total voids, and dry density. The moisture susceptibility of the recycled cold-mix asphalt (RCMA) mixture was evaluated using the tensile strength ratio. Cantabro abrasion loss was used to assess the cohesion resistance of the mixtures. The dynamic response of the mixes to the applied load was evaluated using the resilient modulus. The results of the present study reveal that using BBFs in the RCMA improved the inter-particle bonding and strength. Furthermore, BBF incorporation enhanced the performance of the recycled cold-mix asphalt.

Mechanical foaming of bitumen is a popular technique employed to reduce the viscosity of binder for ensuring coating of aggregates at lower temperature. The potential of this technique is being utilized widely for producing sustainable reclaimed-asphalt pavement (RAP) inclusive mixtures, but usage of recycled concrete-aggregates (RCA) in foamed technology is very scanty. The present study is the first of its kind attempting to investigate the optimum proportion of hydrophobic RAP aggregates and hydrophilic RCA (separately as well as combined) for the preparations of foam-mix asphalt (FMA). It was observed that incorporation of RCA in FMA affects the quality of mixes but RCA inclusive FMA was found to qualify the stipulated specifications for pavement applications. From the present study, it is found that up to 20% RCA and 40% RAP proportions individually could be utilized for the preparation of foam mixes. Also, it is interesting to note that delayed hydration of residual cement grains could enhance the performance of FMA. Furthermore, 30% RCA coupling with 10% RAP was found to exhibit acceptable performance. The present study suggests that 0.1% fiber reinforcement could enhance the performance of the foam mixes considerably.

The present study investigates the potential of RAP for various layers of flexible and concrete pavements. Natural aggregates were replaced in different proportions by the coarse RAP and fine RAP, for preparations of granular subbase, wet mix Macadam, dry lean concrete, dense bituminous Macadam and Plain concrete mixes. Utilisation of both fractions of RAP resulted in reductions in the optimum moisture content (OMC) and maximum dry density of granular subbase and wet mix Macadam mixes, whereas, incorporation of the same was found to increase the OMC of dry lean concrete mixes. Incorporation of coarse RAP doesn’t affect much the engineering properties of base and subbase layers in comparison to fine RAP. Improving the gradation of fine RAP was found to increase its suitability in all the considered mixes. Similarly, utilisation of coarse RAP was found to improve the workability of concrete mixes, however, significant reductions in strength properties were noted. It was observed that as the strength requirement of layer increases, the negative impact of RAP on strength properties also increases linearly, suggesting incorporating a higher fraction of RAP in lower layers and a lower usage of the same for wearing course of the pavement.