Method for the assessment of alkali-silica reactivity of aggregates and concrete mixtures

A chemical test method for assessing the likelihood of the formation of alkali-silica reaction gels in a defined concrete job mix comprising the steps of:

• preparing a mixed aggregate for testing;
• preparing at least three replicates for simulating long-term pore conditions of said defined concrete job mix using said mixed aggregate;
• heating said at least three replicates in an oven for a period of time;
• filtering contents of each of said at least three replicates after the expiry of said period of time;
• measuring concentrations of silicon, aluminum, and calcium in each of said contents from said at least three replicates;
• and
• calculating a reactivity index value using said measured concentrations of silicon, aluminum, and calcium from each of said contents of each said at least three replicates by dividing said measured concentration of silicon by a combined concentration of both said measured concentrations of aluminum and calcium, wherein said reactivity index value is indicative of an alkali-silica reactivity of said mixed aggregate in said defined concrete job mix and the likelihood of the formation of alkali-silica reaction gels in said defined concrete job mix using said mixed aggregate.

A method for assessing the likelihood of the formation of alkali-silica reaction gels in concrete comprising the steps of:

• preparing a plurality of replicates for simulating long-term pore conditions of a proposed concrete mix using a specified aggregate by adding a predetermined amount of calcium oxide, a predetermined amount of said specified aggregate and a soluble alkali to a container to form each of said plurality of replicates;
• conducting an accelerated exposure of said plurality of replicates to simulated long-term pore conditions by heating said plurality of replicates in an oven for a predefined period of time at a predefined temperature;
• analyzing contents of each of said plurality of replicates for concentrations of silicon, aluminum, and calcium after said predefined period of time;
• and
• calculating a reactivity index value for each of said plurality of replicates by dividing a measured concentration of silicon by a measured combined concentration of both said aluminum and calcium in each of said plurality of replicates and averaging their values to obtain an average calculated reactivity index value;
• wherein an average calculated reactivity index value greater than 0.45 is indicative of the likely formation of alkali-silica reaction gels in said proposed concrete mix using said specified aggregate.