Compositions for low heat cements developed especially for massive concrete works and which exhibit a compressive strength/heat of hydration ratio of at least 7.0 at the age of 13 weeks. One of two inventions provides a powder prepared by mixing CaO, SiO.sub.2, and Al.sub.2 O.sub.3 materials, melting the mixture, quenching the melt, and grinding the quenched matter, the powder being composed mainly of amorphous substances and chemically having a CaO/SiO.sub.2 (molar ratio) of 0.8-1.5 and an Al.sub.2 O.sub.3 content of no more than 10 wt. %. The other invention provides a mixed powder comprising no less than 70 wt. % of a powder and no more than 30 wt. % of an addition (portland cement or the like), the powder being the same as that of the first invention in both predominance of amorphous substances and CaO/SiO.sub.2 (molar ratio) excepting the Al.sub.2 O.sub.3 content which is less than 12 wt. % in the second invention.