Development Of High Ductile Cementitious Composite With Characteristic Of Low Shrinkage

PVA-ECC is a kind of high performance cementitious composite with strain-hardening capacity and fantastic cracking property. The basic design principal was founded by Victor C. Li from Michigan University using micro mechanics and fracture mechanics approach initially. But, however, the large dry shrinkage of the traditional PVA-ECC seriously confining the applications. Therefore, study on the developing the materials with characteristic of low shrinkage and remaining the strain hardening and multiple cracking performances are greatly needed.Research emphasis of the present thesis is placed on the development of high ductile cementitious composite with properties of low drying shrinkage and improved cracking performance. The thesis consists of 3 parts. The first part of the thesis focuses on the mix proportion design based on the low shrinkage matrix developed previously. The influences of sand to cement ratio (S/C), water to cement ratio (W/C) and glass powder on the mechanical and cracking properties are investigated by shrinkage test, uniaxial tensile test and compressive tests. The experimental results show that the shrinkage of the developed PVA-ECC is only 10%~20% of that of traditional PVA-ECC. Better tensile and cracking performances can be obtained with the decrease of S/C and increase of W/C. But the influence of S/C on compressive strength is very small. The strain-hardening performance is improved with addition of glass powder.The second part of the thesis focuses on the development of low shrinkage PVA-ECCs with different strength grade. A total of four mixtures with compressive strength from 20MPa to 60MPa were proposed. The experimental results show the designed PVA-ECCs of obvious strain-hardening and multiple cracking performances. The average crack width at tensile strength is smaller than traditional PVA-ECC. The tensile strengths and strain of the four mixtures are between 4.30MPa~6.70MPa and 1.5%~2.6% respectively.The third part of the thesis present a plot of the application of low shrinkage PVA-ECC in improving structural durability by composing PVA-ECC and traditional concrete. The bending tests on different ECC-concrete composite beams were carried out. The experimental results show that PVA-ECC can significantly increase the ductility of the beams and the durability of structures can be improved. The rational manners of ECC-concrete composite structures can not only get fantastic structural properties, but also can reduce the total cost of the structures.