Improvement of Tensile Strength of Unreinforced Concrete Slabs

Abstract

Thin Spray-on Liner (TSL) is extensively used in underground support systems to enhance strength and ductility of rocks and shotcrete. Its effect on strength and ductility of concrete shell elements was intended through this study. The type of TSL used was Polyurea which was applied in variable thicknesses on the tension face of slabs of uniform dimensions, varying strengths, and varying with respect to presence/absence of light reinforcing steel. These variants were to be compared against control specimens (having no coating application). A test setup was devised to apply uniformly distributed load to load the slabs in flexure until failure. Load-displacement graphs obtained from the tests were processed to arrive at predetermined parameters of peak load, yield load, ductility, yield secant stiffness and energy dissipation. It was concluded that with increasing thicknesses of Polyurea coating, there was a significant increase in both the tensile strength and ductility of the slabs. Effect of Polyurea on concrete of varying strengths, however, was negligible. Furthermore, energy dissipation was greater for slabs applied with Polyurea.