In the quest for sustainable construction materials, a recent study led by Hari Krishna Subramaniam from the Centre for Innovative Construction Technology (CICT) at Universiti Malaya and Cement Industries of Malaysia Berhad (CIMA) has shed new light on the potential of finely ground fly ash (FA) to revolutionize cement formulations. Published in the Journal of Civil Engineering and Management, the research explores how the fineness of Class F fly ash can significantly enhance the performance of Type I and Type II Ordinary Portland Cement (OPC) mortars, offering a promising path towards greener construction practices.
The study focused on mechanically grinding fly ash to achieve different levels of fineness, specifically 90% (GFA1) and 98% (GFA2) passing through a 45-µm sieve. These finely ground fly ashes were then used to replace OPC at varying levels—10%, 30%, and 50% by weight. The comprehensive testing regimen included evaluating compressive strength, water demand, setting time, heat of hydration, acid resistance, and microstructural analysis.
One of the most compelling findings was the reduction in water demand. “We observed a significant decrease in water demand by up to 6.3% for Type I and 5.9% for Type II OPC mortars at 30% fly ash replacement,” Subramaniam noted. This reduction not only optimizes the use of water but also enhances the overall efficiency of the cement mixture.
The study also highlighted the long-term strength benefits of using finely ground fly ash. Mortars with 10% GFA2 achieved an impressive compressive strength of 58.6 MPa at 56 days, demonstrating the potential for high-performance, sustainable construction materials. “The enhanced fineness of fly ash leads to improved particle packing and hydration, which contributes to the increased strength and durability of the mortars,” explained Subramaniam.
Type II OPC blends, known for their superior sulfate resistance, exhibited remarkable acid resistance. The study found that mass loss was reduced by up to 43% in mortars with 50% GFA2 replacement compared to Type I OPC. This superior performance is attributed to the lower C₃A content and denser microstructures in Type II OPC, making it an ideal choice for applications requiring high durability and resistance to harsh environments.
The research also delved into the heat of hydration, a critical factor in large-scale construction projects. The study revealed a decrease of 10.9% in hydration heat for Type II OPC, which was further reduced by 40% with 50% fly ash replacement. This reduction in heat generation is particularly beneficial for large pours and mass concrete applications, where thermal cracking can be a significant concern.
Microstructural analysis confirmed the enhanced compactness and reduced ettringite formation in fly ash-modified mortars, correlating with improved durability. “The finer particles of fly ash fill the voids more effectively, leading to a denser microstructure and better overall performance,” Subramaniam added.
The implications of this research are far-reaching, particularly for the energy sector and construction industry. By optimizing the use of fly ash, a byproduct of coal combustion, the study provides a sustainable alternative to traditional cement formulations. This not only reduces the reliance on clinker, a major source of carbon emissions, but also promotes the circular economy by utilizing industrial byproducts.
As the world moves towards net-zero carbon goals, the findings of this study offer a viable path for the construction industry to reduce its carbon footprint. “The use of finely ground fly ash in cement formulations is a step towards achieving sustainable construction practices,” Subramaniam concluded. “It not only enhances the performance of cement but also contributes to a greener future.”
Published in the Journal of Civil Engineering and Management, this research provides critical insights for optimizing greener cement formulations, particularly in regions prioritizing Type II OPC for sulfate resistance and moderate heat applications. The study’s findings are set to shape future developments in the field, paving the way for more sustainable and efficient construction practices.