Physical-mechanical and fresh state properties of self-compacting concrete based on different types of gravel reinforced with steel fibers: Experimental study and modeling

Due to the enormous and rapid growth in the field of construction and public works all over the world, it has become necessary to seek alternatives to the non-renewable natural resources used to protect them from waste and exhaustion on the one hand and to satisfy the environmental aspect on the other hand. Some of the ways to achieve this include recycling various concrete waste resulting from the demolition of old concrete structures or the results of natural disasters to replace natural gravel in the manufacture of different types of concrete mixes. The type of natural gravel used has a significant impact on the compatibility of recycled gravel with steel fiber reinforced self-consolidating concrete (SCCf) in the fresh state and on the improvement of its phys-ical-mechanical performance. In this research, we studied the fresh state properties and the physical-mechanical properties of SCCf composed of natural gravel of two different types with the substitution of the natural gravel by the recycled gravel at percentages of 25%, 50% and 75% by weight. The evaluations of different fresh SCC were conducted using various tests in accordance with the recommendations of EFNARC. On cubic specimens with a side of 10 cm, we successively carried out three tests as follows: at 28, 56, 90, and 120 days, for the tests (ul-trasound pulse velocity (UPV), water absorption, open porosity and compressive strength). A three-point bending strength test was also carried out on rectangular specimens (7 x 7 x 28) cm3 at different ages.The results obtained indicate that all the mixtures tested met all the SCC requirements recommended by EFNARC, the substitution of 25% recycled gravel for the two types of concrete SCCfQ and SCCfL gives better results than that of the concrete SCCfL at 28 days on the tensile strength in bending. The density of the different types of concrete decreases as the percentage of recycled gravel increases. Curing in water has a beneficial effect on reducing the open porosity of the various SCCf fiber-reinforced self-compacting concretes and on increasing the compressive strength, flexural tensile strength, ultrasonic velocity UPV (V). Finally, acceptable and encouraging correlations between the different physical and mechanical parameters of the SCC and the different types of gravel were found.