Long-Term Creep and Shrinkage of Alkali-Activated Concrete Incorporating Fly Ash and Rice Husk Ash

The creep and drying shrinkage of two alkali-activated concretes produced with low-calcium fly ash and rice husk ash (RHA) were investigated over a period of 1 year. The compressive strength of 100% low-calcium fly ash (100NFA) concrete and the concrete having 10% RHA replacement (10RHA) decreased from 49.8 to 37.7 MPa (7.22 to 5.47 ksi) and 30.2 to 18.3 MPa (4.38 to 2.65 ksi), respectively, between 28 and 365 days. The imbalance in the dissolution rate of the raw materials in the blended system (10RHA) could negatively influence the strength properties, which leads to poor matrix integrity and a highly porous structure when compared with 100NFA. The presence of the micro-aggregates due to the block polymerization provides the effect of increasing the aggregate content in the 100NFA concrete compared with the 10RHA concrete, which is hypothesized as one of the reasons creep and shrinkage properties deteriorated in 10RHA.