Performance Evaluation of Sodium Trimetaphosphate (STMP) Modified Gum Arabic as an Agricultural-based Superplasticizer on Fresh and Hardened Properties of Self-Compacting Concrete

This study evaluates the performance of Sodium Trimetaphosphate (STMP) modified Gum Arabic (MGA) as a sustainable bio-admixture for Self-Compacting Concrete (SCC). comparing its fresh, rheological, and mechanical properties against raw Gum Arabic (GA) and a commercial synthetic superplasticizer (SP). Under standardized laboratory procedures, SCC mixes were formulated using Portland Cement (CEM II/A-LL, 42.5) with incremental admixture dosages (0.5%, 1.0%, and 1.5% by binder weight) at a constant water-to-binder ratio of 0.40. Fresh properties were evaluated using Abram’s slump flow, V-funnel flow time, and L-box blocking ratio (h2/h1). Rheological yield stress was derived via an indirect slump-flow methodology, Mechanical strength was assessed using displacement-controlled compression and tensile tests at 28 days, supplemented by X-ray Diffraction (XRD) for mineralogical phase analysis. Experimental results established 1.0% concentration as the optimal saturation threshold across all formulations. At this dosage, 1.0% MGA achieved a slump flow spread of 645 mm, which is 3.73% lower than both 1.0% GA (670 mm) and 1.0% SP (670 mm), yet fully satisfying EFNARC (2005) deformability criteria. In viscosity assessments, MGA demonstrated superior discharge efficiency, recording a V-funnel time of (20.32 s) a 63.71% reduction compared to GA (56.00 s) and a 32.27% reduction compared to SP (30.00 s). Passing ability tests yielded an L-box ratio of 0.91 for MGA, which is 1.09% lower than GA (0.92) and 3.19% lower than SP (0.94), well above the 0.80 non-blocking threshold. Rheological modelling revealed that MGA significantly reduced internal shear resistance, achieving a yield stress of 57.94 Pa and 8.44% reduction compared to GA (63.28 Pa) and a 3.16% reduction compared to SP (59.83 Pa). In hardened state testing, 1.0% MGA attained a 28-day compressive strength of (40.67 N/mm2) (Grade C32/40, representing a 0.12% increase over GA (40.62 N/mm2) and a 0.39% increase over SP (40.51N/mm2). MGA also achieved a 28-day split tensile strength of (4.59 N/mm2), XRD patterns confirmed the formation of dense Calcium Silicate Hydrate (C-S-H) gel without adverse phase shifts. STMP modification successfully enhances the anionic charge density of raw GA, establishing MGA as a viable high-performance replacement for synthetic superplasticizers.