An investigation on early age and long term dimensional stability of high performance cementitious composites

The mechanical properties of Ultra High Performance Concrete (UHPC) have been investigated by many researchers in the literature. However, there is no detailed study about dimensional stability of UHPC. High amount of cement and low water/cement ratio increase the autogenous shrinkage which also increases the crack formation risk. The effect of ingredients on shrinkage behavior of UHPC was investigated in the scope of the experimental study. In the first step, rheological, mechanical and dimensional stability of matrix phase were determined under silica fume, ground granulated blast furnace slag and fly ash replacement. Autogenous and drying shrinkage of matrix phase were monitored at early and later ages. Shrinkage measurement methods that were used in this experimental program are laser sensors, hydrostatic weight measurements, keeping in curing cabinet and measuring with comparator. After fixing the binder phase, the amount and gradation of quartz aggregate were determined. Furthermore, the effect of maximum size of the quartz aggregate was also investigated. The effect of steel fibers on fresh state, mechanical and dimensional stability of UHPC was determined. The effect of sample dimensions, temperature and humidity on shrinkage of UHPC was observed. Cracking resistance of the mixtures was also investigated. Test results indicated that shrinkage of UHPC is a complex phenomenon depended on many parameters. Aggregate content and grading, mineral admixtures, fiber content and curing conditions have great effect on shrinkage of UHPC. One of the most important problems about cast-in-situ UHPC is insufficient dimensional stability. So, an improvement on dimensional stability will provide higher cracking resistance and longer service life.