Experimental study of blast-Furnace slag blended cement concrete investigating and improving shrinkage cracking resistance

Applying blast-furnace slag fine powder blended cement is an important option to achieve low carbon emission due to concrete materials in construction. However, concrete with this blended cement (BFS concrete, hereafter) has been believed vulnerable to shrinkage cracking and traditionally avoided to use in building construction except underground structural elements in Japan. To extend BFS concrete usage in building construction necessitates to quantitatively evaluate this concrete's shrinkage cracking resistance. Scope of this study is to experimentally reveal shrinkage resistance of BFS concrete, in which effects of ambient temperature are emphasized. In experiments, restraint shrinkage cracking tests were conducted with BFS concrete subjected to three levels of ambient temperatures, 10-30 °C in comparison with normal concrete. To improve crack resistance of the former concrete, modified BFS concrete were added in the experiments by using additives like water retaining SRA. As a result, next two major conclusions were obtained: 1) crack resistances of BFS concrete deteriorated due to increasing free shrinkage strain at high temperature, while this is not the case for normal concrete, 2) water retaining type SRA dramatically improved crack resistance of BFS concrete at high temperature.