CEMENTITIOUS COMPOSITIONS AND A METHOD OF THEIR USE

摘要

A settable composition suitable for coating surfaces eg walls of a mine comprises (i) a cementitious composition comprising the following components:(a) at least 25% preferably at least 40% of a reactive cement having a C to A or(A + X) ratio of greater than 1:1 preferably greater than 1.2:1,where X is S* or S or F (b) from 0 to 10% of lime and(c) from 5 to 70% preferably 10 to 40% of calcium sulphate,and where the sum of (b) and (c) is at least 15%the % being by weight based on the combined weight of (a), (b) and (c) and where the proportions of the components are such that the composition on hydration is capable of absorbing at least its own weight of water and(ii) an aqueous emulsion of an organic polymer, the amount of (ii) in relation to (i) being such as to provide a weight ratio of polymer solids to combined weight of (a), (b)) and (c) of from 0.5:1 to 10:1, preferably 0.7:1 to 2:1 or(iii) an organic polymer in the form of a powder dispersible in water and where the amount of organic polymer is such as to give a weight ratio of polymer solids to combined weight of (a), (b) and (c) of from 0.5:1 to 10:1, preferably 0.7:1 to 2:1 andwhere the proportions of the components are selected from within the above defined ranges to provide a composition which on hydration will have a tensile strength at 4 hours of at least 135psi and an elongation at 7 days of at least 20 %.When the composition contains components (i) and (ii) the amount of water can be equal to at least 50% by weight of the weight of the cementitious composition (i), preferably from 70% to 250%.