Sustainable pavement quality concrete utilizing coal bottom ash in rural roads: mechanistic design and sustainability analysis

Concrete pavements play a vital role in the development of any economy. Pavement quality concrete (PQC) behaves differently from conventional concrete due to its requirements for sustaining repeated loads from traffic. The construction of PQC is resource-intensive and costly because of the different raw materials involved. River sand (RS), which is used as fine aggregate in PQC, creates the depletion of natural river sand, affecting the environment and ecology. Coal bottom ash (CBA) is a waste material that can replace RS and promote sustainability. This study consists of five levels of RS replacement with CBA in M40 grade PQC mixes ranging from 0% to 100%. It was found that the PQC mix containing 50% CBA had higher compressive and flexural strength at 90 days of curing as compared to the control PQC mix with no CBA replacement. At this optimal replacement level, the PQC mixes performed better in terms of abrasion resistance and resistance against chloride ion penetration. The thickness of a typical design pavement was reduced by 3.03% with the use of 50% CBA, and the effective cost of construction also reduced by 3.85%. A life cycle analysis revealed 4.01% carbon reduction, indicating potential viability of the use of CBA as fine aggregate in concrete pavements.