Investigating the Effects of Partial Fly Ash Replacement with Limestone Powder in Concrete

ABSTRACT Fly ash has traditionally served as a supplementary cementitious material in the production of concrete, enhancing its mechanical and durability properties through pozzolanic activity. However, with the ongoing decommissioning of coal-fired power plants due to environmental concerns and the shift toward renewable energy sources, the anticipated shortage of fly ash has materialized, prompting the exploration of alternatives for producing durable and sustainable concretes. One promising substitute for fly ash is limestone powder (LP), which garnered attention in recent years for its cost-effectiveness and widespread availability, primarily as a partial replacement for cement in cement-based materials. This study investigated the feasibility of using LP as a substitute for fly ash, aiming to assess its potential impact on concrete properties by formulating seven concrete mixtures, including a control mixture with 70 % cement and 30 % fly ash out of total cementitious materials. Various levels of fly ash replacement with LP, ranging from 5 to 100 %, were explored in the LP modified mixtures. Fresh and hardened properties of the concrete were evaluated to assess the impact of LP substitution for fly ash. The findings revealed that reducing the fly ash content led to increased air content and porosity, consequently lowering mechanical strength. Nonetheless, replacing fly ash up to 30 % with LP resulted in reduced drying shrinkage by 47 % compared with that of the control mixture. Furthermore, the susceptibility to chloride ion ingress was assessed using the rapid chloride permeability test, with charge passed values ranging between 2,000 and 4,000 coulombs, indicating a moderate level of susceptibility. Moreover, LP modified mixtures exhibited superior resistance to freeze-thaw cycles compared with the control mixture. These results underscore the potential of LP as a viable alternative to fly ash in concrete production, offering enhanced durability and sustainability.