Comparison of Molasses and Sika Plastiment VZ as Set-Retarders  in High-Strength Self-Compacting Concrete

This research addresses the need for sustainable and cost-effective alternatives to commercial set retarders in high-strength self-compacting concrete (HS-SCC) production. The reliance on commercial set-retarding admixtures increases construction costs and may have environmental implications, highlighting the need for more economical and eco-friendly alternatives. This study compares molasses, a by-product of sugar production, with Sika Plastiment VZ, a widely used commercial set retarder. The research evaluates their impacts on key HS-SCC properties, including setting time, compressive strength, tensile strength, and modulus of elasticity. Laboratory experiments were conducted using mixtures containing silica fume, a superplasticiser (Viscocrete 1003), and varying dosages of molasses and Plastiment VZ (0.2, 0.4, and 0.6% by weight of cement). The results showed that a 0.4% molasses dosage achieved the best performance, with a compressive strength of 67.43 MPa, well above the design target of 45 MPa and a tensile strength of 4.83 MPa. These findings demonstrate that molasses is a viable and sustainable alternative to commercial set retarders, offering comparable or superior performance in HS-SCC production. It is recommended that the long-term effects of molasses and its compatibility with other concrete compositions be further explored.