石粉含量对机制砂自密实混凝土耐久性的影响

Influence of stone powder content on the durability of machine-made sand self compacting concrete

对比分析了河砂和不同石粉含量的机制砂自密实混凝土的抗氯离子渗透能力、膨胀率、抗碳化性能、抗冻性和长期抗压强度的影响。结果表明,在石粉含量≤9%时机制砂自密实混凝土的抗氯离子渗透能力要弱于河砂自密实混凝土,但河砂和不同石粉含量的机制砂自密实混凝土的抗氯离子渗透性都满足TB 10005—2018使用要求;在机制砂自密实混凝土中加入石粉有助于降低混凝土的膨胀率,且石粉加入量越大则膨胀率越低;不同石粉含量的机制砂自密实混凝土的碳化深度会随着石粉含量先减小后增大,河砂和不同石粉含量的机制砂自密实混凝土的抗碳化能力差别不大;不同石粉含量机制砂自密实混凝土的抗冻性能都要优于河砂自密实混凝土,且石粉含量为3%的机制砂自密实混凝土的抗冻性能最好;过高的石粉添加量(≥12%)会对机制砂自密实混凝土的长期抗压强度带来不利影响,适宜的石粉添加量应≤9%。

The effects of river sand and machine-made sand self compacting concrete with different stone powder content on chloride ion permeability,expansion rate,carbonation resistance,frost resistance and long-term compressive strength are compared and analyzed.The results show that when the stone powder content is≤9%,the chloride ion permeability of sand self compacting concrete is weaker than that of river sand self compacting concrete,but the chloride ion permeability of river sand and machine-made sand self compacting concrete with different stone powder content can meet the application requirements of TB 10005—2018.Adding stone powder to machine-made sand self compacting concrete helps to reduce the expansion rate of concrete,and the greater the amount of stone powder,the lower the expansion rate.The carbonation depth of machine-made sand self compacting concrete with different stone powder content will first decrease and then increase with the stone powder content.There is little difference in carbonation resistance between river sand and machine-made sand self compacting concrete with different stone powder content.The frost resistance of machine-made sand self compacting concrete with different stone powder content is better than that of river sand self compacting concrete,and the frost resistance of machine-made sand self compacting concrete with stone powder content of 3%is the best.Excessive addition of stone powder(≥12%)will adversely affect the long-term compressive strength of machine-made sand self compacting concrete,and the appropriate addition of stone powder shall be≤9%.