Evaluation of bond strength between sand concrete as new repair material and ordinary concrete substrate (The surface roughness effect)

Abstract

In the present work, a great deal of importance is attached to sand concrete as a new repair material. An investigation was conducted to evaluate the bond strength and the type of failure in composite concrete bi-layers. The test specimens under study were made of an ordinary concrete substrate and sand concrete (repair material). The substrate was prepared from ordinary concrete of two different classes of strength, i.e. the first one contains a superplasticizer (OCS) and the other has no superplasticizer (OC). To this purpose, four different surfaces used as substrates, namely low roughness (LRG), high roughness (HRG), drilled holes (DH), and combination of high roughness with drilled holes (HRGDH) surfaces were prepared. For the repair materials, two mixes of sand concrete were selected, namely sand concrete with 100% of limestone filler (SCL), on one hand, and sand concrete with 50% of limestone filler and 50% of glass powder (SCG), on the other. Two adhesion tests (flexure test, and splitting test) were performed in order to evaluate the response of the composite test specimens under loading, by determining the mode of failure produced after the test. The results of splitting strength obtained showed that the sand concrete gives remarkable bond strength of 2.54 MPa for cylindrical specimens and 317 MPa for cubic specimens. These values present a good to excellent bond quality, depending on the strength level of ordinary concrete, reflecting a good adhesion to the substrate, which manifested a positive monolithic response. These performances allowed us to consider the sand concrete as a good cementitious repair material.