Case study of fiber reinforced, lightweight concrete, intended for production of precast elements

The presented work was focused on developing a lightweight, quasi self-compacting, fiber reinforced concrete mix for pre-cast use. The research activities covered a complex iteration design process and experimental tests leading to the selection of the final mix. The threshold requirements for the final mix were: strength class of at least LC 25/28, quasi self-compacting properties of the fresh concrete mix and good quality of the surfaces of hardened elements. During the design process a wide array of lightweight aggregates was considered characterized by bulk density ranging from 340 kg/m 3 to 750 kg/m 3 . Ten different concrete mixes were created. Two mixes characterized by most promising properties were further developed by the addition of steel fiber. Eventually, one of the mixes was chosen for the final tests. Compressive strength after different time intervals, tensile strength, shear strength and LOP characteristics of the chosen mix were of key interest. Durability associated properties were also tested. Ultimately, lightweight concrete with the density of 1640 kg/m 3 and the strength class of LC 30/33 was obtained.