Effects of high rebar casting temperature on porosity and Ca/Si ratio at steel-concrete interface of reinforced concrete

This study investigates effects of elevated rebar casting temperature on the interfacial porosity and Ca/Si ratio of the steel-concrete interface by scanning electron microscopy (SEM). Experimental variables including rebar casting temperatures of 25 degrees C, 40 degrees C, 55 degrees C, 70 degrees C, and 85 degrees C, water/cement ratios of 0.30, 0.45, and 0.60, and rebar diameters of 10 and 20 mm are considered. Large capillary pores of steel-concrete interface (SCI) were quantified by back scattered electron (BSE) imaging and Ca/Si ratio of hydration products of SCI were obtained by energy-dispersive X-ray (EDX) spectroscopy. The results were analyzed by using statistical methods (ANOVA analysis and Pearson correlation analysis). Results indicate that the average interfacial porosity and the average Ca/Si ratio can increase as a result of heated rebar effects. Heated rebar effects can be enhanced by increasing rebar diameter. Impact ranges of the heated rebar effects are also presented.