Determination of Maturity Relations for Steel-Fiber Reinforced Concrete

The evaluation of steel-fiber reinforced concrete using the maturity method was investigated in this study. There were five different volume fractions of fibers (0, 0.5, 1, 1.5 and 2% by volume of concrete) and three different curing temperatures (8°C, 22°C and 32°C) considered. Maturity method has been widely used to predict compressive strength of concrete, although less research have been used to investigate other properties of concrete by maturity method. In this study, compressive strength, flexural strength, flexural toughness and splitting tensile of steel fiber reinforced concrete were also evaluated by maturity method. The compressive strength, flexural strength and splitting tensile strength were tested at 1, 3, 7, 10, 14, 28 and 56 days for all of the volume fractions of fibers and at different curing temperatures. However, flexural toughness were tested at ages of 3, 7, 14, 28 and 56 days for all volume fractions of fibers at different curing temperatures. The apparent activation energy was determined for all volume fractions of fibers by three methods (linear hyperbolic, parabolic hyperbolic and exponential). The results show that activation energy decrease by increasing volume fractions of fibers in all methods. In order, to determine apparent activation energy, the compressive strength of mortar were tested at ages of 1, 2, 4, 8, 16, 32 and 64 days and at curing temperatures of 8°C, 22°C and 32°C for all the five-volume fractions of fibers. In this study, two maturity methods were used to calculate equivalent age and maturity index, these were the Arrhenius and Nurse-Saul methods. However, according to different apparent activation energies, three equivalent ages were calculated as namely LHeq, PHeq and EXPeq. The predicted models obtain by LHeq have a very good correlation with experimental results. Four different strength-maturity equations (linear hyperbolic, parabolic hyperbolic, logarithmic and exponential) were used to predict the compressive strength, flexural strength, flexural toughness and splitting tensile strength for three equivalent ages and maturity index. All of these four equations have good correlations with the experimental results. However, the accuracy linear hyperbolic and exponential is slightly higher parabolic and logarithmic equations. In this study totally 320 new maturity models were established and for each test, the predicted models were compared with each other. In addition, the validation of each model was evaluated. Moreover, some necessary factors for using maturity method such as temperature histories and datum temperature were evaluated for all mixes. The temperature histories at first 24 hours are slightly increased by increasing volume fractions of fibers.