Studying thaumasite sulfate attack using compressive strength and ultrasonic pulse velocity

The performance of blends of Portland-limestone cements and supplementary cementing materials (SCMs) were studied in thaumasite sulfate attack (TSA) using ultrasonic pulse velocity (UPV), compressive strength and expansion tests. The tests were performed on mortar samples periodically to assess the reliability of UPV and compressive strength in studying TSA. The expansion study was performed on 25 x 25 x 285 mm mortar prisms while the compressive strength and UPV were performed on 50 x 50 x 50 mm mortar cubes. The inclusion of SCMs delayed expansion; however, after expansions exceeded 0.05 %, they proceeded rapidly. It was observed that in general the compressive strength and UPV of mortars increases until certain stages. Then, due to development of TSA, considerable reductions may occur. The results of both latter tests were affected by TSA and were in accordance with expansions. A good correlation was found between the average compressive strength and the average UPV of mortar cubes during 3 years of TSA. It was found that reductions in both compressive strength and UPV occurred near the time of the onset of rapid expansion and well before the expansion limit of 0.10 % was reached. It may indicate that UPV can be used in investigating deterioration due to TSA.