Performance Research Of Shrinkage Compensating Engineering Cementitious Composite

Engineered Cementitious Composite(ECC)is a kind of advanced cement based composites,which has a high ductility and toughness.On the one hand,there is no coarse aggregate in ECC,the water binder ratio of ECC is low and the proportion of cementitious material is large,these lead to shrinkage and cracking in the early time.On the other hand,fibers could effectively reduce the shrinkage and cracking of ECC.However,there is only a small amount of research about how the two factors influence the shrinkage law of ECC together.Besides,how the expansion components would influence the shrinkage law and other properties of ECC is an uncertain problem.Therefore,researching the properties of shrinkage compensating ECC is significant for preventing early shrinkage and cracking,the popularization and the application of ECC.The contents and results of this paper are as follows:First of all,the aluminate cement and gypsum as the expansion component added into the concrete matrix,after that,the shrinkage compensating concrrete matrix could be obtained.The shrinkage law,flexural strength and compressive strength of shrinkage compensating concrrete matrix and original concrete matrix have been compared respectively.The rusults show that: due to the increasing of ettringite in the system,the shrinkage compensating concrete matrix expands during the early time and shrinkage during the later period.It is different that,the original concrete matrix shrinks during all the period.In terms of comprssive strength and flexual strength,the shrinkage compensating concrrete matrix is a little higher than original concrrete matrix.And when the proportion of the aluminate cement is constant,the compressive strength of shrinkage compensating concrete matrix decreasing as increasing the amount of gypsum,but the flexual strength firstly increase and then decrease.In the second place,the shrinkage compensating PVA-ECC could be obtained by putting the Polyvinyl Alcohol(PVA)fiber into the shrinkage compensating concrete matrix.The non-contact laser displacement sensor has been used to test the shrinkage law during 28 d of shrinkage compensating PVA-ECC.The rusults show that: the shrinkage compensating PVA-ECC expands during the early time and shrinkage during the later period also.The shrinkage of shrinkage compensating PVA-ECC is increasing as the increase of the PVA fiber content,it is diametrically opposite to ordinary PVA-ECC.In addition,the early expansion and expansion duration of shrinkage compensating PVA-ECC in the water were higher than it in the air.Thirdly,the compressive strength,flexual strength and bending strength of shrinkage compensating PVA-ECC and ordinary PVA-ECC have been compared.The rusults show that: the compressive strength of shrinkage compensating PVA-ECC is higher than ordinary PVA-ECC at 3d,but a bit lower than ordinary PVA-ECC at 28 d.In the apect of flexual strength,the shrinkage compensating PVA-ECC is lower than ordinary PVA-ECC both at 3d an 28 d.Bending strength of shrinkage compensating PVA-ECC is higher than ordinary PVA-ECC at 3d.Different rule in 28 d,the bending strength of shrinkage compensating PVA-ECC is decreasing when PVA fiber content is 0 and 0.5%,but increasing when PVA fiber content is 1.0%,1.5% and 2.0%.Besides,comparing with standard curing,3d water curing would reduce all the three kinds of strength of shrinkage compensating PVA-ECC.What’s more,four points bending test has been used to test the toughness of shrinkage compensating PVA-ECC.The rusults show that: the bending toughness of shrinkage compensating PVA-ECC is higher than ordinary PVA-ECC in the early period,but lower in the later period.Moreover,comparing with the shrinkage compensating PVA-ECC after standard curing,water curing 3d would reduce bending toughness.Finally,after comparing with different properties of shrinkage compensating PVA-ECC and ordinary PVA-ECC,then it could make a summary: expansion component could produce the expansive effect of PVA-ECC in early period,it would effectively prevent shrinkage and cracking.And expansion component does not bring negative effects to other properties of PVA-ECC.Futhermore,water curing is unfavourable for compressive strength,flexual strength,bending strength and toughness of shrinkage compensating PVA-ECC.In addition,it gives some advices about the research of shrinkage compensating PVA-ECC in the future.