Restrained alkali-aggregate expansion due to steel fibre additions in concrete

The work reported here shows that steel fibres can reduce the expansion caused by alkali-aggregate reaction in concrete, hereby decreasing the resulting strength loss. The addition of 1-1.5% of steel fibres by volume allowed us to increase the alkali content by about 2 kg/m^3. Under such conditions, the ultrasonic pulse velocity was found to be stable, and the expansion rate low, indicating only minor effects on the strength of the concrete, even though the concrete contained reactive aggregate and a high alkali content. More specifically, the efficiency of fibres for restricting expansion is governed by the size and geometric parameters of the fibres. The expansion rate was linearly related to the so-called fibre factor or fibre index, for otherwise similar alkali-aggregate reaction conditions.