Testing and modelling the creep of cracked macro-synthetic fibre reinforced concrete (MSFRC) under flexural loading

An investigation of the delayed crack opening of cracked concrete containing short discrete macro-synthetic fibres under sustained flexural loading at service conditions (30-50 % of the average residual strength of cracked specimens) over a period of 8 months is reported. The time-dependent crack opening in flexure is simulated by implementing both the material model parameters obtained from a tension softening model and a rheological model for viscoelastic behaviour in the Total Strain Crack Model using the finite element method. Prisms measuring 100 mm x 100 mm x 500 mm and 150 mm x 150 mm x 700 mm were cracked under uniaxial tensile and three point flexural tests respectively and then subjected to sustained loadings in their respectively creep frames. In all cases, specimens were produced from the same concrete mix and fibre content. All specimens were tested in a climate controlled room at a temperature of 23 +/- A 1 A degrees C and relative humidity of 65 +/- A 5 %. Experimental results have indicated that significant lesser creep occurred in specimens subjected to flexural creep compared to the uniaxial tensile creep specimens. The result of the finite element analyses at both stress levels shows good agreement with the experimental time-dependent crack opening results in flexure.