Experimental Study on Portland Pozzolana Cement and Citric Acid Influence on Compressive Strength of Reinforced Concrete

Abstract

In Ethiopia, the construction industry relies heavily on Ordinary Portland Cement (OPC) for structural applications due to its rapid early strength development. However, the widespread use of OPC contributes to high production costs and increased carbon emissions associated with cement manufacturing. Therefore, there is a growing need to evaluate more sustainable alternatives, such as Portland Pozzolana Cement (PPC), potentially enhanced with organic admixtures, to meet structural performance requirements while reducing environmental impact.

This study investigates the combined effect of partially replacing Ordinary Portland Cement (OPC) with Portland Pozzolana Cement (PPC) and adding citric acid as a chemical admixture on the compressive strength, setting time, and workability of reinforced concrete. Concrete samples of C-30 grade were prepared using OPC, PPC, and PPC modified with varying dosages of citric acid (0.1–0.4% by weight of Portland Pozzolana Cement). Experimental results indicated that citric acid acts as a retarder and water-reducing agent, improving the workability and extending the setting time without significantly compromising strength. The optimal dosage was determined to be 0.3% citric acid, which resulted in a 55% increase in slump, a delay in setting time of 1 hr 50 min (initial) and 3 hr 10 min (final), a comparable 28-day compressive strength to OPC mixes and a cost reduction of 258.86 Ethiopian birr per cubic meter of concrete. The combined use of PPC and citric acid demonstrated improved performance and cost effectiveness compared to OPC-based mixes, promoting sustainable concrete production suitable for the Ethiopian construction industry.