Experimental Reserch On Self-compacting Ultra High Toughness Cementitious Composite

A kind of new high performance fiber reinforced concrete, Ultra High Toughness Cementitious Composites (abbreviated as UHTCC), which shows prominent toughness and superior durability has been successfully recognized and applied in many practical projects overseas. During construction of commen UHTCC, problems,such as bad dispersion of fiber due to complex reinforcement arranged,lower workability of UHTCC and shortage of construction technique,often arise which will affect its durability.To resolve the problems above,a kind of advanced UHTCC with high workability called self-compacting UHTCC, which can flow through and fill the gaps of reinforcement and corners of molds without any need for vibration and compaction during the placing process,is badly needed. In this paper, a series of tests for PVA fiber reinforced UHTCC have been done by using overseas results of self-compacting UHTCC as a source of reference.The details are as follows:1. Through the tests of deformability and flow rate,it has been found that the affect of workability of fresh motar with the water-reducer added and the loss with time,and then the best water-reducer content was determined, a series of tests for workability of UHTCC with the water-reducer content above,such as deformability test,fiow rate test,filling ability and the ability of passing through the gaps of reinforcement. It turned out that the workability of this UHTCC has met the self-compacting requirement.A test was done on this fresh self-compacting UHTCC containing air entraining agent of appropriate content,it showed that the effect of proper air entraining agent on material's workability was minimal.2. Through cubic specimens compressive strength test,it was studied that the difference of compressive strength between commen UHTCC specimens and self-compacting ones and the effect of vibration and air entraining agent added on the compressive strength of self-compacting UHTCC.3. Through four-point bending test for sheets and beams,it was studied that the difference of flexural behavior between commen UHTCC specimens and self-compacting ones and the effect of vibration and air entraining agent added on the flexural behavior of self-compacting UHTCC. In addition,a model of load-deformation curve for bending test of UHTCC sheets was established according to the test results,and the whole curve was approximately devided into four stages.4. Through three-point bending test of beams for fracture property,P-δand P-CMOD curves for UHTCC were described and then the whole fracture process was analyzed. Through electric resistance strain gauge technique,initial craking load and maximum were finally measured. In addition,the paper have investigated the difference of fracture property between UHTCC with and without air entraining agent and that between UHTCC with different initial crack-depth ratios.