Thermal stress of high volume fly-ash (HVFA) concrete made with limestone aggregate

This paper presents numerical simulation of the thermal stress as well as experimental results establishing thermal and mechanical properties of high volume fly ash (HVFA) concrete of 50% replacement of cement by fly ash. The HVFA concretes are made with fine and coarse aggregates of limestone, so it has a significant low coefficient of thermal expansion (CTE). The low CTE may contribute to reduction of thermal stress in addition to low temperature rise. On the contrary, gradual strength development of HVFA concrete at early age should be considered for possibility of thermal cracking. To examine the crack resistance of the HVFA concrete at early age, a uniaxial tension test using prismatic concrete specimens was performed and tensile properties such as tensile strength and tensile Young’s modulus were quantified for 75 samples. Adiabatic temperature rise and CTE tests were also conducted to provide more evidence of the thermal properties. The thermal properties measurements confirmed that CTEs of the HVFA concrete are approximately 5 × 10⁻⁶/°C. The thermal and mechanical properties of HVFA concrete were adopted in a Finite Element (FE) simulation using a model of T-shaped bridge pier. The numerical simulation confirmed the favorable thermal properties contributing to decrease of thermal stress.