Strength and durability of lightweight concrete

Two lightweight aggregate concretes, SLWC35 and SLWC50, of 35 and 50 MPa 28 day cube compressive strength were cast. The concrete specimens made with lightweight coarse aggregates and a dune sand were continuously cured in water for one or 7 days and then exposed to predominantly hot and humid seaside ambient conditions containing air-borne salts. After 7 days of initial curing and on subsequent exposure to hot and humid air both SLWCs attained an almost similar strength to those continuously water cured cubes at an age of 12 months. In contrast, the water penetrability of SLWC35 and SLWC50 after 7 days of initial curing and subsequent exposure to the sea side was about 2 and 1.8 times the water penetration of those slabs which were water cured for the entire duration of 12 months. However, the depth of carbonation of the two sand lightweight concretes LIP to an age of 12 months were negligibly small. The results suggest that compressive strength is comparatively less sensitive to the curing regimes investigated. Both the chloride and sulphate penetration after 12 months exposure were found to be within tolerable limits. Also replacement of lightweight fine aggregate with normal weight sand produces a concrete that is somewhat more durable as indicated by their water penetrability and depth of carbonation when concretes are of equal strength. (C) 2003 Elsevier Ltd. All rights reserved.