机制砂MB值对混凝土碳化性能的影响研究

Effect of MB value of manufactured sand on carbonation of concrete

为促进机制砂的应用,合理控制机制砂MB值,试验研究了MB值对混凝土碳化性能的影响,并采用孔结构分析了影响机理,结果表明:随着机制砂MB值得增大,混凝土减水剂掺量呈现增加趋势,MB值在0.35~1.05之间,混凝土减水剂掺量增加趋势相对较为缓慢,而MB值超过1.40之后,混凝土减水剂掺量增大趋势更为明显;混凝土抗压强度随着机制砂MB值得增大,呈现先缓慢增长后迅速下降得趋势;混凝土弹性模量随着机制砂MB值得增大,呈现明显下降趋势;随着机制砂MB值的增大,混凝土碳化深度变深,MB值低于1.05时,碳化深度变深的趋势相对较弱,而MB值超过1.40时,碳化深度随着机制砂MB值增大而变深的趋势较为明显。砂浆孔隙率和平均孔径随机制砂MB值的增加而增大,机制砂泥粉使得浆体孔隙增多,劣化了浆体孔结构。

In order to promote the application of manufactured sand and reasonably control the MB value of manufactured sand,the effect of MB value on the carbonation performance of concrete was studied by experiments,and the influence mechanism was analyzed by using pore structure.The results showed that with the increase of MB value of manufactured sand,the content of water reducing agent in concrete showed an increasing trend.When the MB value was between 0.35 and 1.05,the increasing trend of water reducing agent in concrete was relatively slow,while the MB value was more than 1.40,the increasing trend of concrete water reducing agent content is more obvious.The compressive strength of concrete increases slowly with the value of manufactured sand MB,and then decreases rapidly.The elastic modulus of concrete increases with the value of manufactured sand MB,and then decreases significantly.With the value of manufactured sand MB,the carbonation depth of concrete becomes deeper,and when the value of MB is lower than 1.05,the carbonation depth becomes deeper.The trend is relatively weak,but when the MB value exceeds 1.40,the carbonation depth tends to be deeper with the increase of MB value of manufactured sand.The porosity and average pore diameter of mortar increase with the increase of MB value of random sand making,and the pore structure of mortar is deteriorated by the increase of mechanical sand powder.