废橡胶纤维增强混凝土的制备及力学性能研究

以废橡胶纤维和硅灰的含量为变量,制备了废橡胶纤维增强混凝土。探究了单一水灰(w/c)比为0.45,不同比例废橡胶纤维(0~25%(质量分数))替换细骨料,硅灰(0,5%(质量分数))替换水泥的情况下,废橡胶纤维增强混凝土的可加工性、抗压强度、密度和弹性模量等力学性能,通过SEM和EDS分析,研究了废橡胶纤维混凝土的显微形貌及元素分布情况。结果表明,混凝土的可加工性不受废橡胶纤维添加量的明显影响;随着废橡胶纤维替换细骨料比例的提高,两种废橡胶纤维混凝土(无硅灰和硅灰5%(质量分数))的抗压强度、密度和弹性模量均逐步降低;而相比无硅灰加入的混凝土试样,加入5%(质量分数)硅灰试样的抗压强度、密度和弹性模量都有不同程度的提高,说明5%(质量分数)硅灰的掺入,加强了废橡胶与水泥基体之间的粘结,提高了混凝土的刚度,使材料更加不易发生变形,耐久性能更好。SEM和EDS分析表明,废橡胶纤维和混凝土结合并不牢固,两种材料相互之间润湿性较差,界面结合力学性能较低;废橡胶纤维含有微量的硫和锌,从而加剧了废橡胶纤维与混凝土粘结剂之间润湿性较差的问题。

Study on preparation and mechanical properties of waste rubber fiber reinforced concrete

Using the content of waste rubber fiber and silica fume as variables, waste rubber fiber reinforced concrete was prepared. The machinability, compressive strength, density and modulus of elasticity of waste rubber fiber reinforced concrete were studied when the ratio of water cement to cement(w/c) was 0.45, the ratio of waste rubber fiber to fine aggregate was 0-25wt%, and the ratio of silica fume to cement was 0, 5wt%. The micro-morphology and element distribution of waste rubber fiber reinforced concrete were studied by means of SEM and EDS analysis. The results showed that the workability of concrete was not affected by the amount of waste rubber fiber added. With the increase of the proportion of waste rubber fiber replacing fine aggregate, the compressive strength, density and modulus of elasticity of the two kinds of waste rubber fiber reinforced concrete(without silica fume and silica fume of 5wt%) were gradually reduced. Compared with the concrete without silica fume, the compressive strength, density and modulus of the concrete with silica fume of 5wt% were gradually increased. Elastic modulus was improved to varying degrees. It showed that the addition of 5wt% silica fume strengthened the bond between waste rubber and cement matrix, improved the stiffness of concrete, made the material more difficult to deform and had better durability. SEM and EDS analysis showed that the bonding between waste rubber fiber and concrete was not firm, the wettability between the two materials was poor, and the mechanical properties of interface bonding were low. The waste rubber fiber contained trace sulfur and zinc, which aggravated the problem of poor wettability between waste rubber fiber and concrete binder.