Experimental Study of Ultra-High-Early Strength Repair Grout Systems

Abstract

Ultra High Early Strength self-compacting repair grout (having compressive strength of about 3000 psi in half hour) is being used more and more frequently in repair of concrete structures and making pre-placed aggregate due to the many advantages it offers when compared with conventional vibrated concrete. In Civil Engineering works, setting of cement or cementitious system is very time consuming as well as costly, due to curing, however, by using special types of cement and admixtures we can reduce the time of setting of concrete as well as reduce the cost by saving the amount of form work and cure. The research was carried out on ultra high early strength repair grout system to make self-compacting, self-leveling pre-placed aggregate concrete. Primarily calcium aluminate cement, Istra 40, was used to achieve ultra-high early strength SCP along with a suitable accelerator. Furthermore as secondary objective, a blend of ordinary Portland cement and Calcium aluminate cement was also used for the reason of economy. Fly ash, class F imported from Germany, was used to reduce water demand and to achieve the required flow and additionally avoiding strength degradation through the hydration of silicate present in fly ash with time. In addition to mineral admixtures, some chemical admixtures were also used such as a PCE based super plasticizer and suitable accelerator to help in the flow, setting and penetration aspects. Fine sand with fineness modulus of 2.3 was used and coarse aggregate used was passing from 1” and retaining in ¾” sieve. Particle size characterization, water demand, super-plasticizer demand, accelerator demand, setting times and compressive strength tests on self-compacting paste systems (SCP) were conducted. Calcium aluminate cement along with suitable accelerator was used to achieve a compressive strength of 4000 psi for SCP system and 3000 psi for SCM system in half an hour. Furthermore, OPC in blend with 15% calcium aluminate cement, 1500 psi compressive strength was achieved in half an hour for SCP system. It is recommended that calcium formate accelerator for OPC should be used for further continuation of this project and to improve compressive strength results.