EFFECTIVENESS OF GUM ARABIC AS A SUPERPLASTICIZER IN SELF-COMPACTING CONCRETE

Abstract

Self compacting concrete is a type of concrete that flows under its own weight and does not require compaction to expel the entrapped air. Admixtures are added in concrete in order to obtain out-of-the ordinary properties and/or in concrete with non-convectional technology. Use of admixtures in self compacting concrete is inevitable. However, the commercially available admixtures are synthetic and produced using petrol fuels and resulting concrete is therefore non ecological. In addition, most of superplasticizers require a viscosity modifying agent which introduces a new component into the concrete further complicating their action. The objective of this study was to investigate the suitability of Gum Arabic as a superplasticizer in self compacting concrete at different dosages and w-p ratio while using polycarboxylate ether based superplasticizer as control. Cleaned Gum Arabic was dissolved in water and later oven dried at 1100C until a slime was formed; which was ground and dissolved in 30% of the mixing water at different dosages. With a target of 660-750mm and 36 MPa compressive strength, an optimum dosage of 8% at w-p of 1.0, 0.9, and 0.8 was achieved with a spread flow of 680mm; the concrete was stable with no bleeding and/or segregation. W-p ratio of 0.8 and 4% by weight of cement dosage of Gum Arabic produced self compacting concrete with a compressive strength of 21MPa at 28 days. The cost of producing one cubic meter of concrete using Gum Arabic admixture was higher than polycarboxylate ether superplasticizer. Gum Arabic however, produces ecological self compacting concrete and its use in production of concrete will expand the market for farmers and therefore promoting the country’s economy. It was recommended that, chemical composition, structure and molecular mass of Kenyan Gum Arabic be studied; other structural elements of self compacting concrete using Gum Arabic admixture be investigated as well as combining Gum Arabic with other bio materials and studying their effect in concrete.