E A Laycock* & T Yates** * Sheffield Hallam University ** Building Research Establishment


Work was carried out on the validation of the test to measure expansion due to sulfate. The work involved the manufacture of a series of three clay brick samples. Some of these bricks would have their sulfate contents artificially increased by dosing them with amounts of magnesium, sodium, potassium and calcium sulfate salts. In the validation work, 3-hole perforated wire cut bricks, with 21% water absorption were used, and dosing was carried out by plugging the perforation holes and filling the resulting reservoirs with known quantities of the sulfate containing solution. Results showed that expansion due to the reaction of the sulfate salts with the C3A content of the cement could occur very early in the life of the samples, before curing time had elapsed, and that these expansions could be of sufficient magnitude to cause a loss of strength when measured in direct tension.