To recycle concrete waste and to produce concrete having a low exothermic value, high strength and high flowability by mixing a cement admixture consisting of a fine concrete recycle powder that is obtained from concrete waste and has a specified particle size, and anhydrous gypsum and/or a fine siliceous powder, preferably together with a water reducing agent, with cement, to form a cement composition and to produce concrete from the cement composition.
This cement admixture consists of a fine concrete recycle powder which is obtained by crushing concrete waste with a crusher into a crushed material to obtain a crushed powder as a part of the crushed material and classifying the crushed powder into two kinds of powder, i.e. a powder that has ≥0.15 mm particle size and is utilized as recycle aggregate, and another powder that has <0.15 mm particle size and is used as this fine concrete recycle powder; and anhydrous gypsum having particle size appropriate to provide preferably an about 3,000-10,000 Blaine specific surface area and/or fine siliceous powder preferably such as fumed silica having an about 10-30 m2/g BET specific surface area. The cement admixture, preferably together with a water reducing agent, is mixed with cement to form a cement composition. This cement composition is capable of providing concrete produced from the cement composition with a ≤50°C adiabatic temperature rise value.
MORIOKA MINORU
WATANABE YOSHIHARU
SAKAI ETSURO
DAIMON SEIKI
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