Experimental Investigation on the Effect of Superplasticizers and Retarders on Workability and Strength Properties of High Strength Concrete

High strength concrete (HSC) is widely used in modern construction due to its superior mechanical and durability properties. However, achieving adequate workability at low water–cement ratios remains a major challenge. This study investigates the effect of polycarboxylate ether (PCE) based superplasticizers and retarders on the workability, strength, and durability properties of M60 grade high strength concrete. Concrete mixes were prepared with varying dosages of superplasticizer (0.8%, 1.0%, and 1.2% by weight of cement) and combined dosages of superplasticizer with retarder (0.2% and 0.4%). Fresh concrete properties such as slump, slump retention, compaction factor, and setting time were evaluated. Hardened concrete properties including compressive strength, split tensile strength, flexural strength, and water absorption were assessed at 7, 28, and 56 days. The results indicate that superplasticizers significantly improve workability and strength, while the combined use of superplasticizer and retarder provides excellent workability retention without adversely affecting long- term strength and durability. The study demonstrates that an optimum combination of chemical admixtures is essential for the practical application of high strength concrete.