Portland cement concrete is a widely used construction material due to its durability, long service life and great economy. The mechanism and properties related to chemical kinetics under variable environmental conditions should be clearly understood to effectively control the use of concrete in construction and make judicious choices of materials. Cement acts as a binding agent when mixed with water and aggregates will react chemically with each other to form concrete. However, in concrete many chemical components of reactive aggregate & cement lead to undesirable chemical reaction which has detrimental effects to concrete. One of the major sources of this deterioration is the alkali-aggregate reaction. Since 1940s, several research have been conducted to identify chemical reaction between cement and aggregate that contribute to concrete degradation. Though aggregates are chemically inert to a certain extent, reactive aggregate particles make chemical contact with the alkali hydroxides in concrete, degrading coherence between concrete materials and developing crack in concrete structure over a period of many years. The two major types of alkali-aggregate reaction are alkali-carbonate reaction (ACR) and alkali-silica reaction (ASR). Incidences of ACR are hardly seen and generally formed with dolomitic or ACR-susceptible aggregates which are restricted to a few isolated regions. In ASR, aggregates containing silica will react with alkali hydroxide in concrete which form alkali silica gel in a solid form (1). This gel further swells when it absorbs water from surrounding cement paste or the environment and induce increasing internal pressure in the cementitious matrix of concrete structure (2). This pressure may initiate expansion and develop crack in concrete materials. Unlike ACR, ASR is considerably more widespread and is of more significance in the United States.
