COMPARATIVE RESISTANCE TO SOFT WATER ATTACK OF MORTARS AND FIBRE-CEMENT PRODUCTS MADE WITH OPC AND BLENDS OF OPC AND MILLED QUARTZ, PFA AND GGBS

In addition, researchers at the National Building Research Institute found that the leaching process in fibre-cement pipes also frees sulphate ions that will penetrate the pipe wall, react there

with Ca(OH)2 and alumina to form ettringite between layers; the ettringite will then place the outer circumference under hoop stress. The stress may lead to longitudinal cracking in small diameter FC pipes (South African Fibre-Cement Association 1986) (Figure 2).