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Abstract

This study investigates the effect of Chemrite SP-303 superplasticizer on the strength of concrete, focusing on its impact on compressive and tensile strengths. Basic concrete constituents, including crushed angular coarse aggregates (maximum size 9.5 mm), natural river sand, Ordinary Portland Cement (grade 42.5), tap water, and Chemrite SP-303, were utilized in the experimental work. Four concrete mixes were prepared with varying dosages of Chemrite SP-303, ranging from 0.4% to 2% of the cement mass, using the method, termed RGW, which involved replacing gauging water with the superplasticizer. A control mix, designed for a 28-day compressive strength of 25 N/mm², contained no superplasticizer, while the other mixes incorporated the superplasticizer at increments of 0.5% up to 1.5%. The workability of the fresh concrete was evaluated using the slump test, after which the concrete was cast into standard 6" x 12" cylinders. 48 cylinders were subjected to curing periods of 7, 14, and 28 days, and then tested for compressive and split tensile strengths. Results indicated that superplasticizer addition generally improved compressive strength, with the most significant gains observed at dosages ranging from 0.5% to 1.5%. Beyond this range, the strength tended to decrease. The study also highlighted that water reduction of up to 22.93% was achieved with superplasticizer use, contributing to strength improvements. For optimal results, superplasticizers should be used at the manufacturer-recommended dosage, balancing between improved workability and strength. This research underscores the importance of precise superplasticizer dosing in enhancing concrete performance while maintaining workability. Recommendations include thorough testing of cement properties for each replacement percentage and careful handling of superplasticizers to achieve desired concrete strength and workability.