Thermogravimetric Analysis of Carbonate Aggregates

The durability of coarse aggregate has a major impact on the durability of Portland cement concrete. Thermogravimetric (TG) analysis is a relatively rapid technique that has shown good potential in previous work for its usefulness in the analysis of carbonate aggregates. In this work, the TG technique is used to analyze 31 limestone aggregates and two dolomitic aggregates through heating the specimens to a temperature above 1,000°C and recording the weight loss and the change of weight loss as a function of temperature. Results show that limestone aggregates yield typical TG curves and a major weight loss takes place around 900°C. Dolomitic aggregates yield typical TG curves with a two-stage weight loss. The first stage is due to dolomitic loss, which occurs around 700°C while the second is a calcite loss similar to limestone aggregates. Results also indicate that a correlation exists between the slope prior to calcite transition in TG curves and some durability aspects of limestone. The TG data can be used to calculate the percent acid insoluble and the pavement vulnerability factor. These values are equivalent to conjugate values determined using the conventional methods. Therefore, TG can be considered a relatively rapid method for acid insoluble and pavement vulnerability factor determination.