Use of high ductile mortar mixing method for the enhancement of flexural fracture behaviour of steel filler mortar

The use of steel fillers enhances the flexural behaviour of mortar and concrete. However, it makes it more difficult to disperse them uniformly and coat them firmly in the mortar/concrete with the conventional mixing method while using them at higher content. In this method, steel fillers are generally mixed after the mixing of mortar with a full part of water. In the high ductile mortar mixing method, the viscous mortar was first prepared with the first part of the water and then the steel fillers were mixed. Its workability was increased in the final stage of mixing with the second part of the water. The mixture proportion of the base mortar was similar to that used for the production of the permanent formwork (W/C = 30% and W = 206 kg/m3). The content of steel filler (0, 1.5%, and 2.5%) was by volume of the mortar and it was used as part of the sand. The distribution and coating condition of steel filler was better in the second mixing method. It was made possible due to the strong kneading and lapping action within the viscous mortar. The flexural strength was increased by 28.7% with less variation. It was a 241% increase from that of plain mortar and only a 165% increase was with the conventional mixing method. The high ductile mortar mixing method enhanced the flexural strength, deflection, rigidity, flexural performance, and fracture energy of steel filler mortar more than that of the conventional mixing method. This result contributes to reducing the thickness of permanent steel filler mortar formwork as well as of other structures enabling easier transportation and erection work. Moreover, it also helps to reduce the overall cost of the steel filler mortar structures.