A Study on Delayed Deformations of an Ultra High Strength Cementitious Material

Abstract

This paper presents the results of an experimental investigation of shrinkage and creep under uniaxial compressive loading of Reactive Powder Concrete (RPC). RPCs are ultra-high strength concretes characterized by high silica fume content and steel fiber reinforcement. The present study focuses on RPC with a very low water/binder ratio (0.17) and a compressive strength at 28 days of 160 MPa and 200 MPa after a 90 deg C heat treatment. The thermogravimetric analysis shows that in RPC a high proportion of cement remains unhydrated, and the pozzolanic reaction becomes predominant two weeks after mixing. The autogenous shrinkage and creep of RPC were measured on sealed specimens. The stress level on the creep specimens represented 20% of the concrete compressive strength at the time of loading. The basic creep kinetics of RPC is very rapid and does not differ from high strength concrete, whereas its magnitude can be twice as much. The basic creep amplitude and kinetics of RPC are strongly affected by the age of loading. After a heat treatment of RPC at 90 deg C, the shrinkage becomes insignificant, and the basic creep is highly reduced.