BOND STRENGTH OF NEW TO OLD CONCRETE IN SANDSTONE AND GRANITE CONCRETE SPECIMENS

Due to the increased level of construction in Malaysia at present and in future, traditional aggregate for use in concrete will become scarce or even more expensive. In Sabah particularly, granite aggregate is scarce and the average production of sandstone aggregates including river pebbles is about 12 million tonnes. Crushed aggregate production is about 6.5 million tonnes, which is more than 54%of total aggregates. Therefore, in places there is a scarcity of suitable materials for economic consideration may necessitate experimenting with suitable locally occurring substitute materials. Concreting bonding is an important area particularly in construction using prefabrication method namely precast and semi precast units. Precast and semi precast concrete units are used widely in the construction industry because of advantages of labour reduction, short construction duration and cost effectiveness. Many constructions have failed due to the debonding that occurs in semi precast concrete slab. The bond performance between the old and the new concrete plays an important role in the structural performance (Abu-Tair et. al, 2000, Bonaldo et. al, 2005). Failing to bond properly will cause shrinkage and finally crack that may promote the corrosion of steel reinforcement due to the penetration of chloride ions, water and other hazardous substances. Bonding as well depends on the structuring of the fresh concrete in direct contact with the old surface (Calres-Gibergues et al, 1993). In this paper, the effectiveness of different types of binder in bonding the new and the old concrete was studied. The experimental work included the usual construction method of binding the new and old concrete and also polymer-based bonding agent. The results of the study on granite concrete slab and sandstone concrete slab are compared.