Properties of Anti-Washout Concrete with High Blast Furnace Slag Content

This paper will discuss how anti-washout concrete has been proposed for recent construction projects such as foundation work for long-span bridges. For such applications, thermal cracking of concrete is one of the major concerns. For conventional underwater concreting, rich mixes are required to insure the quality of the concrete. With the intent of developing a low-heat type underwater concrete, high blast furnace slag content was used as replacement of cement to reduce the heat of hydration of cement. The characteristics of fresh concrete, adiabatic temperature rise, and compressive strength of the anti-washout concrete with slag were examined. The major variables in the experiments were slag content, fineness of slag, type of cement, etc. Adiabatic temperature rise of anti-washout concrete with a slag content of 50 to 80 percent was higher than that without slag. However, when the slag content was more than 80 percent, significant decrease in adiabatic temperature rise was observed. Compressive strength with up to 90 percent of slag content was higher than that without slag. From these results, it was proposed that a mix proportion of concrete with a slag content of 90 percent and fineness of slag 4000 cm/g would be suitable for such underwater massive concrete.