Experimental Research On Self-consolidating PVA Fiber Reinforced Cementitious Composites

Engineered cementitious composite (ECC) is a kind of fiber reinforced cementitious composite developed in recent 20 years. ECC shows a multiple cracking pattern and a strain-hardening behavior during the loading process. Therefore, compared to conventional fiber reinforced cementitious composite, ECC has better mechanical properties and durability, and has been applied in many practical projects. When common ECC is utilized as the structural materials of continuous bridge deck, the bad dispertion of fiber and aggregate, as a result of the complex reinforcement arranged and lack of vibration and compacting, often lead to durability problems. To sovle the above problems, a kind of advanced ECC with high workability, which is named self-consolidating ECC, is badly needed. It can flow through and fill the every corner of formworks without any vibration and compacting during the placing process. In this paper, a series of tests for PVA fiber reinforced ECC have been done by using international achievements of self-consolidating ECC as references. The details are as follows:(1) Experimental research on fresh-state workability of PVA-ECC and its mortar. The deformability and flow rate tests were adopted to measure the effect of superplasticizer content on workability of fresh mortar and the loss with time, and then the optimal superplasticizer content was determined. Besides, a slump flow test was performed to assess the workability of PVA-ECC mixtures with different fiber, fly ash addition and w/b ratio.(2) Experimental research on hardened-state mechanical properties of self-consolidating PVA-ECC. The bending test, compressive test and tensile test were carried out to evaluate the effects of different fiber, fly ash addition and w/b ratio on the fundermental mechanical properties of self-consolidating PVA-ECC. As a result, the bending and compressive strength, the stress-strain curve, the ultimate tensile stress and the ultimate tensile strain were obtained.(3) The effect of fiber addition on early-age (24h) cracking behavior of self-consolidating PVA-ECC was investigated. A restrained shrinkage knife-edge test including 12 slab samples was carried out to characterize the early-age cracking behavior of self-consolidating PVA-ECC. Combined with fractal theory, the irregular nature of early-age cracks were described. In addition, the mechanism of fiber on resistance of cracking was analysed.(4) Experimental research on resistance of chloride ion penetration of self-consolidating PVA-ECC. The effects of different fly ash, fiber addition and w/b ratio on chloride ion resistance of self-consolidating PVA-ECC at various curing age were systematically discussed through the Rapid Chloride Migration (RCM) test. The optimal fly ash and fiber content were obtained.