Mechanical performance of ECC with high-volume fly ash after sub-elevated temperatures

Engineered cementitious composites (ECC) are known for their strain-hardening behavior under tension, and have been increasingly applied in engineering practice. However, the lack of understanding about the performance of ECC exposed to elevated temperatures limits their application in some special fields. Therefore, the residual mechanical performance of ECC containing very high volume fly ash (FA/C = 4.4) and polyvinyl alcohol fibers (HVFA-ECC) was investigated after temperature exposures of 20 °C, 50 °C, 100 °C and 200 °C, considering the melting temperature of polyvinyl alcohol fiber is about 230 °C. The test results indicated that HVFA-ECC maintains its unique multiple cracking and pseudo strain hardening characteristics after temperature exposure within this range. The tensile properties, including the ultimate tensile strength and tensile strain capacity, increased after the 50 °C and 100 °C treatments, but diminished after the 200 °C exposure. To better understand the impacts of thermal exposure, tests were carried out on the fiber tensile strength, fiber/matrix interfacial bond and matrix fracture toughness. It was found that the fiber's tensile strength retained its room temperature value up to 100 °C exposure, but dropped significantly after undergoing the 200 °C heating. The interface parameters (chemical bonding Gd and frictional bonding τ0) and the strain-hardening index (Jb′/Jtip) have a similar trend as the composite tensile properties, which explained the variation of composite response with thermal treatment. The test results indicates that HVFA-ECC can resist a sub-elevated temperature (⩽200 °C) exposure, and a moderate temperature treatment (⩽100 °C) may actually enhance ECC's tensile properties. This study provides a scientific basis for further development of ECC for elevated temperature applications and also a possible technique to improve ECC's mechanical properties.