Press moulding mixts. of gypsum, cement and sand - with defined relation between strength, pressure and sand content

摘要

Prodn. of moulded articles (e.g. building blocks or bricks) is carried out by pressing a mixt. of gypsum (CaSO4.2H2O), cement and sand. The cement content is 8-15 wt.% (based on dry gypsum and sand) and the moisture content is >5 wt.%. The improvement lies in the fast that, starting from a given compressive strength D (in kg/cm2), the applied pressure P (in kg/cm2) and the sand content S (in wt.% based on dry gypsum) are determined by the relation D=2.6x103 (100-S)-1.2P0.43. The D value obtd. can vary by +10% of the indicated value depending on the cement used and the moisture content. Compared with the process of the Parent Patent (using a relation based on a fixed P value of 150kg/cm2), this process allows greater flexibility in the choice of P, S and D values.