I. EL-SAIE, G.A. KHOURY, J.B. NEWMAN Imperial College, London

This work was prompted by concern over the effectiveness of infitt concrete as protection to steel in reinforced masonry. C30F infill concrete as recommended in BS5628 was severely cracked in 18 of the 19 wall units tested. Varying wall cavity width, mix workability, water/cement ratio and type of brick made only marginal differences to the results. The problem was solved for bricks with water absorptions of 3-6% by the use of gas forming expanding agents giving 1-3% expansion. For bricks with a water absorption of 17% the cracking was also reduced but not eliminated. The quality of the uncracked concrete with gas forming agent compared favourably with standard C30P concrete not influenced by masonry. Revision of BS5628 is, therefore, recommended.