SELF-CURED HIGH PERFORMANCE CONCRETE

Bad curing is often a source of later disease of a structure because of lower strength and higher permeability than anticipated. To overcome this problem, it has been suggested that concrete be cured directly where it is needed. To this aim a water reservoir was generated in lightweight aggregates (LWA) that were uniformly distributed in the concrete. Eleven mixtures were designed such that they should reach a minimum cube strength of 85 MPa irrespective of curing. The mixes contained 10-25% by volume lightweight expanded clay aggregates with respect to the total volume of aggregates. The aggregate size of LWA was varied between 4 mm and 8 mm. Results revealed that a partial replacement of normal weight aggregates by prewetted LWA leads to an internal water supply for continuous hydration of cement. Despite water loss by evaporation, there was a continuous strength gain: up to 25% more strength after one year compared with standard compressive testing after 28 days. Normal weight aggregate concrete reached considerably less strength at the same storage conditions. Application of such concrete in practice means that no curing from bad workmanship would not impair the concrete; in other words, it would be robust during construction.