EFFECTS OF THE CHARACTERISTICS OF THE AIR BUBBLE SYSTEM, CURING TYPE,SURFACE FINISHING AND SILICA FUME ON SCALING RESISTANCE OF HIGH-PERFORMANCE CONCRETE

In Canada, high-performance concretes (HPCs) are increasingly used in construction and repair, particularly for its durability, which is dis tinctly superior compared with ordinary concrete. The current tendency is to provide for a spacing factor of air bubbles lower than 230 mu m in all HPCs that are subjected to freeze-thaw cycles. This choice is basically the outcome of an ongoing controversy as to the necessity of providing a good network of entrained air bubbles to protect HPCs aga inst freeze-thaw cycles. In the future, the optimal use of HPC will de pend, among other factors, on a better understanding of minimal requir ements regarding the characteristics of air voids to ensure a good beh avior of HPCs under freeze-thaw cycles. The results of the investigati on reported herein show that a spacing factor lower than approximately 500 mu m can be sufficient to ensure a good resistance of HPCs to sca ling. It is also shown that surface trawling, slump, and set-retarding agents have only secondary effects on the scaling resistance of HPCs. Silica fume and membrane curing have allowed to improve significantly the scaling resistance of the HPCs under investigation.