Influence Of PVA Fiber And Steel Fiber On Mechanical Properties Of New Cement Composites

Ultra Lightweight Cement Composites（ULCC）as a new type of material was originally intended to meet the requirements and development of offshore structures,most of the existing research is focused on adding PVA fiber,the mixed with PVA and of the comparison of the steel fiber is not much,but there is not much comparative study on the influence of PVA fiber and steel fiber.The development of offshore structures also requires that structural materials have a better ability to withstand impact and even blast loads.Based on this,two types of fiber（PVA fiber and steel fiber）and three fiber volume fractions（0%,0.5%and 1.0%）were designed under the condition of keeping the water-binder ratio.The compressive strength of the cylinder specimens,the breaking strength of the prism specimens,the compression strength of small cube after breaking and the flexural properties were studied under the conditions of 3 days,7 days and 28 days ages.And the dynamic compression strength were measured under 28 days.The main research contents and conclusions are as follows:1.The effect of steel fiber on the compressive strength of ultra lightweight cement composite cylinder specimens is higher than that of PVA fiber.Compared with the ratio without fiber added,the reinforcing effect of steel fiber on the strength is remarkable,the highest compressive strength after adding steel fiber is 1.17 times than that of the strength when PVA fiber is added.The extreme compressive strain of the matrix after adding steel fiber is higher than that PVA fiber is added.The extreme compressive strain with 0.5%and 1.0%volume of steel fiber was 1.08 times and 1.25 times than that of adding PVA fiber.2.The effect of steel fiber on the compression strength of small cube after breaking of ultra lightweight cement composite is higher than that of PVA fiber,and the enhancement effect was obvious when the volume content was 0.5%,the highest compressive strength of small cube after breaking when adding steel fiber was 1.23times than that of the strength when PVA fiber is added.3.The effect of steel fiber on the breaking strength of ultra lightweight cement composite is higher than that of PVA fiber,and the enhancement effect was obvious when the volume content was 0.5%,the hightest breaking strength when adding steel fiber was 1.82 times than that of adding PVA fiber.4.The effect of steel fiber on the toughening effect of ultra lightweight cement composite is higher than that of PVA fiber,and the enhancement effect was obvious when the volume content was 0.5%,the higthest toughening effect when adding steel fiber was 1.47 times than that of adding PVA fiber.5.The flexural properties and flexural toughness of the matrix after adding steel fiber is higher than that PVA fiber is added,and the effect was even more pronounced when the fiber volume was 0.5%.Under the same age condition,the ultimate flexural strength is 39.24%higher than that of adding the PVA fiber,and the residual strength coefficient was 3.19 times than that of adding PVA fiber.6.The specimens with PVA fiber has better dynamic compression performance,and the effect is more significant when the volume content is 1.0%,and under the average strain rate of 25s^-1 to 35s^-1,the strain rate enhancement effect of the peak stress of specimen with PVA fiber is 1.52 times than that of adding steel fiber.