Influence of curing method on characteristics of environment-friendly angular shaped cold bonded fly ash aggregates

Abstract

A large quantity of natural aggregate is being used for the construction of roads, buildings, and mega-structures that affect the environment. It is also noticed that the scarcity of good quality aggregate in some regions of the country leads to an increase in the cost of aggregates. Some efforts have been made to find out a substitute for natural coarse aggregates. Several processes for the production of fly ash aggregates have been developed in the past and some of these were commercialized. These processes are very costly and time-consuming resulting in the non-use of these aggregates on a large scale in civil engineering applications. It is also found that the pelletization process manufactures round-shaped aggregates that have negligible interlocking properties leading to lower load-bearing capacity. In this study, the effect of various curing methods on the strength of fly ash-lime mixes are investigated through the unconfined compressive strength, aggregate impact value, X-ray Diffraction pattern, and scanning electron microscope images. From this study, the hot water curing method has been found as more effective for the hardening of the fly ash aggregates and suggested for further study. Secondly, the rapid and economical four-step process for the production of angular shaped high strength fly ash aggregate has been proposed in the paper. This method for producing fly ash aggregate comprises simple four steps of mixing, compaction, curing, and crushing. The aggregates made with the said process have dense structure, angular in shape for better interlocking, excellent mechanical properties such as toughness and hardness, and high durability. These aggregates also fulfill the Indian specifications for road aggregate and the requirement of structural concrete aggregates. The bulk utilization of this fly ash aggregates in the civil infrastructures can solve two problems with one effort: (a) Fly ash disposal problem and (b) Provision of needed construction aggregates, thus protecting natural diminishing resources of aggregates.