Influence of Shape of Reclaimed Concrete Aggregate Treated with Geopolymer on Flexible Pavement Design

Abstract

Pakistan confronts financial issues as a developing nation. Road construction is vital to a country's prosperity, but it's expensive. In poor countries like Pakistan, where resources are scarce, it's important to employ cost-saving innovations in road design and construction. The thickness of the pavement has a major impact on the overall price tag of a road construction project. This study focuses on designing cost-effective flexible pavements by replacing RCAs for the subbase layer without decreasing durability and life span. Construction and demolition operations generate tons of debris each year. Construction debris is a waste of time, money, and resources. Here, recycling is a great option that has been overlooked in the building industry. Recycled materials from building and tearing down structures are a viable source for the massive quantities of aggregates needed for roads subbase layer construction. In this research work the influence of different shapes (elongated, cone, angular and mix) of RCAs treated with the geopolymer is made from fly ash were examined as well as in contrast to the fresh aggregates. A comprehensive laboratory evaluation of quality, compaction and strength characteristics of RCAs was undertaken using gradation, Los Angeles abrasion, flakiness & elongation index value, aggregate crushing & Impact value, modified proctor test, soaked California bearing ratio (CBR(s)) tests. When taking into account the LA abrasion value, flakiness, and elongation indices, the quality of different shapes of RCAs (Elongated, Cone, Angular, and Mix) has been compared to that of Fresh aggregates. To create the geopolymer of Class F status, derived from fly ash particles of fly ash were combined using a silicate of sodium (Na2SiO3) and sodium hydroxide (NaOH). The 12-M of NaOH solution was prepared and class F fly ash was taken 20% by weight of soil improve the strength characteristics of RCAs. There were five different weight percentages (0, 5, 10, and 20%) of fly ash based Geopolymer applied as additives in all shapes of RCAs and 10% by weight of soil in all shapes of fresh aggregates, as adding 10% geopolymer content gives high strength to the aggregates and enhanced the geotechnical characteristics under study. Flexible pavement subbases with observed CBR(s) values are acceptable. The thickness of flexible pavement using the CBR(s) values were derived using Excel spread sheets. Moreover, cost benefits analysis was performed by estimating the construction cost on 1 km road comparing the RCAs and fresh aggregates. The proposed recycling technique also provides a cost-effective, sustainable, and environmentally safe form of flexible pavement while reducing the need for fresh material in the subbase layer.