SLIIT International Conference On Engineering and Technology,Industry Connect Papers Vol. 04 [SICET] 2025

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Open Access
Mechanical Properties of OPC-Fly Ash Blended Cement Mortar Samples Utilizing Fly Ash from Sri Lankan Power Plants
(Faculty of Engineering, 2025-09-09) Maduwantha, N; Kulasuriya, C
This paper presents findings of an investigation of the compressive strength and water absorption of fly ash blended cement mortar samples made using fly ash (FA) generated in power plants in Sri Lanka. Ordinary Portland Cement (OPC) was substituted partially by 10%, 20%, 30% and, 40% of FA by weight. The control mixture was made up entirely of 100% OPC. The ratio of Cement is to sand was 1:2.75 by volume. Three water to binder ratios were used in preparing mortar samples as 0.375, 0.4, and 0.425. A total of 180 mortar cubes of 50mm x 50 mm x 50mm were prepared and the mortar cubes were water cured. The mortar samples were tested for water absorption at age of 28 days and compressive strength at the ages of 3, 7, and 28 days. The test results show that water absorption increased with FA content, while compressive strength decreased slightly at early ages but remained within an acceptable range. At 28 days, FA replacement had no significant negative impact on strength, and the water absorption was inversely related to compressive strength and density. These findings indicate that OPC can be partially replaced by up to 40% FA without compromising mechanical performance, offering benefits in reducing CO2 emissions, conserving energy, and promoting sustainable construction materials.