This paper presents the results of a study on the effect of high temperatures on the mechanical properties of high-strength concretes. Mixtures were prepared with water to cementitious material ratios of 0.40, 0.35, and 0.30 containing silica fume at 0, 6, and 10% cement replacement. After heating to 100, 200, 300, and 600°C , the compressive strength, the splitting tensile strength, and the corresponding ultrasonic pulse velocity were measured. A substantial loss of strength was observed for all compositions at 600°C , particularly the silica fume concretes in spite of the superior mechanical properties provided by silica fume at room temperature. The average residual compressive and splitting tensile strengths of the concretes at 600°C were 30 and 25% of the room-temperature strengths, respectively. It was found that the rate of the splitting tensile strength loss is higher than the rate of the compressive strength loss at elevated temperatures and that the ultrasonic pulse velocity measurements slightl...

Durability is one of the most important considerations regarding the design of new concrete structures in aggressive environments. Thaumasite sulfate attack (TSA) is one durability consideration. This paper reviews the features of TSA, factors affecting TSA, thaumasite formation mechanisms, and prevention measures. Finally, some needs for future studies are also suggested. TSA can completely destroy the cementitious binding ability of concrete by transforming it into a mush. Many factors affect thaumasite formation and TSA. The four primary factors affecting TSA on portland cement-based materials are low temperatures (below 15°C) and the presence of sulfates, carbonates, and moisture. Apparently, the dissolution–precipitation mechanism can be used to explain most phenomena during TSA. A procedure for field studies is also proposed. Both material compositions and surrounding environments should be considered for the prevention of TSA in concrete structures.