Some results of exposure tests on durability of calcium silicate bricks

Abstract

Batches of calcium silicate bricks from over 25 different brickworks and ranging in compressive strength from 7 to 35 N/mm 2, have been exposed in shallow trays and on concrete slabs for periods up to 30 years. The results of annual inspection have been correlated with the original compressive strength according to the classes used in the current British Standard Specification No. 187 : 1967. Transverse strength, accelerated freezing and water absorption tests are reported on a proportion of the sample batches. Also, eleven larger sample batches of bricks from nine different brickworks were used in burial tests, in which individual bricks were exposed in both completely buried and half-buried conditions in a heavy, wet clay soil. Determinations of compressive strength and chemical analysis were made on some bricks of each batch excavated at various ages up to 20 years. Some decrease in strength was found under these severe conditions, coupled with substantial carbonation of calcium silicate material. Small free-standing panels and retaining walls were built from four of the batches of bricks used in the burial tests. These also were inspected at intervals of up to 20 years. The results of these long term exposure tests are compatible with present British Standard classification of calcium silicate bricks and the recommendations for their use in British Standard Codes of Practice.