Study On Concrete Reinforced With Jute Fibres

Concrete is the most extensively used as architectural materials and it is very popular in engineering filed all the time. But the flaws of the concrete, such as its brittleness, limit its application and good effect. Mixing fibers into concrete can improve the properties of the materials in micro-structure mechanism. It can improve tensile strength, toughness and crack resistance and so on. It has been done many researches in high property fiber reinforced concrete and some synthetic fiber reinforced concrete. But the study of the natural fiber reinforced concrete and its mature productions are rare both in theory and in engineering application. As environmental fibers are payed more and more attention to in international area, the application of nature fiber reinforced concrete will have a very wild development.The jute fiber (noil) was firstly used as the concrete reinforced material, and the microscopic mechanism of the concrete reinforce (crack resistance) and the relationship between the microscopic mechanism and macroscopic characteristic is investigated in the paper. The microscopic models which is used to analyze the fiber bridged stress and to forecast fiber reinforced concrete single tensile cure is established, and the stress-displacement whole curve of the jute fiber reinforced concrete is forecasted by using this model.Firstly, the essential properties of jute fiber and the crack resistance property are studied. The paper analyses the mechanism of jute fiber improved crack property of concrete and the influence of fiber reinforced concrete microscopic mechanism on the crack property. The results show that jute fiber property and shape can improve crack resistance of fiber reinforced concrete. Compared with mortar, the average crack index of mortar mixted jute has decreased by 82.1 percents. Crack resistance property has improved obviously, and its effect depends on fiber's properties and the mesoscopic mechanism of fiber reinforced mortar, and follow some rules. The average crack index of high module fiber reinforced mortar is higher than that of the low module fiber reinforced mortar; the higher of the fiber volume ratio, the better of the effect of crack resistance; when the other conditions are in the same, the relative crack index of jute reinforced mortar, the fineness of the fiber is much finer, the effect of crack resistance is better, the length of the fiber is longer, the effect is worse. Model of fiber reinforced mortar is established. It is used to analyse the properties of fiber and the rule of the micro-mechanism of fiber reinforced mortar influence on the crack resistance by ANSYS software. The results accord with the experimental results. It is said that it is one kind of effective methods to use ANSYS software establish FEM model to analyze the crack mechanism. In the interface mechanics aspect, the influence of the bond property between fiber and matrix and the surface property of fibers on the crack resistance of the concrete is studied. By analyzing pull-out curve of jute fiber and polypropylene fiber, the local bond stress-local slide curves of jute fiber and polypropylene fiber are obtained, and four linearity and three linearity simple bond model are established, and the process of pull-out fibers from concrete is simulated well.Secondly, the splitting tensile of the jute reinforced concrete is studied. Contrast with mortar, the splitting tensile of jute reinforced mortar increase 10 to 15 percents. The splitting tensile of the jute reinforced concrete in all directions are almost the same, that is the mechanics property of jute reinforced mortar is isotropy. It shows that jute fibers distribute three dimensions randomly in the mortar. The influence rules of the property of fibers and the micro-mechanism of fiber reinforced mortar on the splitting tensile are the same with its crack resistance properties. Then, based on the individual pull-out test, hypothesis and simplify the pull-out curves in axial and slanting direction of jute fibers, the micro pull-out model of three dimensions random distribution of jute fiber in the mortar is established. According to this model, the stress-displacement theory curve of the jute reinforced concrete is identical with the test curve. The model is viable. This method can apply for the similar type fibers to forecast the single tensile curve of the fiber reinforced concrete.Finally, the investigation results of the paper are summarized. Some suggestions are put forward for future research of correlative properties of jute fiber reinforced concrete.