Assessing Tensile Properties of Fire-Damaged Engineered Cementitious Composites with Hybrid Fibres

Engineered Cementitious Composite (ECC) is one special type of fibre-reinforced cementitious composite which is well known for its strain hardening behaviour under direct tension. For practical applications of ECC in buildings and infrastructures, performance of ECC under different environments should be evaluated. The fire resistance of ECC is questionable, especially when non-fire-resistant polymer fibres are used. PVA fibres are most widely used polymer fibres in ECC, however, they will melt at temperature around 220 degrees C leading to disappearance of strain-hardening behaviour. In the study, 0.5% volume of PVA fibres was replaced by steel fibres in ECC so as to alleviate the negative impact of melting of PVA fibres. Tensile stress-strain relationships of this type of ECC with hybrid fibres after 100 degrees C to 600 degrees C at an increment of 100 degrees C were investigated. Digital Image Correlation (DIC) technique was used to capture cracking patterns of fire-damaged ECC. It was found that steel fibres improve tensile behaviour of ECC at 300 degrees C. After 600 degrees C, 79% of tensile strength of ECC remained. The results provided useful information of tensile behaviour of ECC with hybrid fibres and yielded promising direction for future improvement of tensile properties of ECC at elevated temperatures.