Influence of the interface cementing agent on the bond strength of interface

The influence of different interface cementing agents on the bond strength of interface between the new and old concretes is studied in order to find out the most favorable interface cementing agent. A layer of interface cementing agent about 1.5-2 mm thick is brushed on the surface of the preprocessed old concrete and then the new concrete is poured on it. After 28 day standard curing, the split strength of the bond interface is tested; the test result is used to reflect the influence of different interface cementing agents on the bond strength between the new and old concretes. The testing results show that the mixture of cement and UEA and the agent including 95% cement and 5% silica ash can dramatically improve the bond strength between the new and old concretes, compared with the interface without brushing the interface cementing agent, brushing the interface cementing agent can improve bond strength by 88.7%. It is concluded that with the increase of W/B, the impact of interface cementing agent on the bond strength decreases, and adding mineral admixture and UEA to the interface cementing agent can dramatically improve bond strength between the new and old concretes, when the W/B and dosage of the agent are the same, the effects of adding silica ash is better than that of adding fly ash.