Evaluation of concrete-steel bond strength in wet mix sprayed concrete

Abstract

The high performance obtained in wet mix sprayed concrete has extended the field of applications of this technique. In some of these applications, such as in diaphragm walls or bridge rehabilitation, the structure may be subjected to bending moments, so conventional reinforcement is regularly used. In this context it is important to assure adequate bond between steel rebar and the sprayed concrete. It is well known that sprayed concrete presents smaller size coarse aggregate, higher mortar content and higher porosity than conventional concrete. Therefore, differences in the bond behaviour are expected. This paper presents a specific procedure in order to evaluate concrete-steel bond strength in sprayed concrete. The proposed test is based on pull-out method using a test panel specimen. The experimental program includes tests performed in conventional and sprayed concrete. The results obtained show the viability of the method, which could be easily applicable in the case of sprayed concrete. The tests performed indicate that, despite the intrinsic scatter, the bond behaviour is similar to that of conventional concrete.