Cement-sand mixes for moulds and cores - using dextrose-calcium chloride mixt. as catalyst for rapid setting

摘要

A mixt. contg. (based on the wt. of sand) 3-12% cement, 2-4% total water, and 1-6% of a catalyst; the catalyst contains 0.1-1 pts. wt. of an alkali- or alkaline earth chloride and 1-5 pts. wt. of a reducing cpd. Pref. substances for the catalyst are calcium chloride and dextrose or glucose-syrup or molasses. The great advantage of the catalyst is that moulds can be used for casting within 3-4 hrs. of mfr. The pref. cement is portland CP A500 with a max. SO3 content of 2.5% and the pref. grain-size of the sand is between 15-80 AFA. By using (all pts. wt.) 100 sand, 7 cement, 4 dextrose-molasses, 0.4 CaCl2.2h2O, 2.5 total water, the resulting mould has a compression strength of 14 kg/cm2 after 45 mins. as compared with a max. of 0.5 kg/cm2 for sand mixes contg. either no catalyst or only one of the two constituents forming the catalyst. The compression strength of the mix showing 14 kg/cm2 after 45 mins. increased after total setting times of 4 and 6 hrs. to 24 and 30 kg/cm2 respectively.