Deleterious alkali–silica reactivity in the laboratory and under field conditions

Expansion test results are reported for concretes made with a range of original alkali contents and prepared a number of UK aggregates containing chert and flint. The concretes were subject to three exposure regimes: moist storage at 38°C, moist storage at 20°C, and external exposure. The current age of exposure for some of the concrete prisms stored at 20°C and some of the concrete blocks stored externally is 4·5 years. It is shown that original alkali contents above about 5·0 kg/m³ are necessary for deleterious expansion to result from alkali–silica reaction, and that concretes stored externally which have exhibited abnormal expansion within 4 years gave expansions in excess of 0·2% when stored moist at 38°C for one year. A model is presented which may enable the expansion behaviour of a number of the concretes tested under field conditions to be broadly predicted from the expansion measurements made in controlled tests on same concretes.