| abstract |
Prodn. of a hydraulically hardening mixt., esp. a concrete mixt. is improved by first preparing a premix contg. normal Portland cement and water, opt. with addn. of gravel, sand and other known additives and then admixing, before the beginning of the setting, another premix contg. a fused alumina cement and/or a cement predominantly consisting of 11 CaO. 7 Al2o3-CaX2 (in which X is Cl, Br, I or pref. F). The premixes alone set slowly (90 min.) but when they are mixed together the mixt. sets rapidly (within 3 min), and the concrete shows a considerable early strength. One or both premises can be heated so that the work can be carried out at temps. 0 degree C; additional heating is provided by heat liberation during the setting. |