Utilizing pond ash as fine aggregates in sustainable green concrete pavement – A case study

Abstract

According to a recent estimate, more than 75 major accidents related to coal ash ponds have been reported between 2010 and 2020 which have resulted not only in loss of life and property, but also in extensive pollution of land, water, and air around the accident sites. In order to promote mass consumption in lieu of disposal, this study was aimed at utilizing the unused coal ash as fine aggregates in concrete pavements. In this regard, a pilot study was undertaken at NTPC Mouda wherein M25 grade pavement quality concrete (PQC) was used for casting a 500 m stretch of road inside the power plant premises. The mix design was prepared at VNIT Nagpur utilizing coarse and fine pond ash from NTPC Mouda as fine aggregates. OPC 43 grade of cement along with locally procured crushed stone aggregates were used. A compatible hyper-plasticizer was also used to maintain the workability and rheology of the concrete. The concrete was laid manually and was observed to attain its final setting within 600 min. The segment was cured for 28-days and finally, cores were extracted to evaluate the in-situ compressive strength of PQC and ascertain its durability. A 28-day compressive strength of 29.3 MPa along with reduced chloride ion permeability and abrasion loss indicate that the suggested approach of utilizing pond ash as fine aggregates in concrete roads is a sustainable alternative to conventionally used mix designs. Hence, the said approach will be a “greener” approach towards PQC construction reducing the dependency on natural river sand. Owing to the abundance of coal ash available in ash dykes, it is also expected that the suggested approach will prove cost-effective in terms of unit cost of concrete production.