粉煤灰掺量对海水海砂高性能混凝土性能的影响

通过宏观力学性能、化学收缩、pH值、氯离子浓度等测试和SEM、XRD等微观表征研究粉煤灰掺量对海水海砂高性能混凝土性能的影响。结果表明:为维系钢筋钝化膜稳定,高温蒸养时粉煤灰掺量不宜大于30%(质量分数,下同),标养时粉煤灰掺量不宜大于50%;海水海砂高性能混凝土中游离Cl^-浓度随养护时间波动,前期先升高后骤降,后期缓慢增加,标养条件下Cl^-浓度明显低于高温蒸养条件下;海水海砂高性能混凝土具有早强性,其强度随粉煤灰掺量增加大致呈下降趋势,高温蒸养可明显提高混凝土抗折、抗压强度;粉煤灰掺量越多,残留的未水化颗粒越多,高温蒸养可有效改善混凝土微观结构,提高致密性;粉煤灰掺量过多或过少均会增加硅酸盐水泥体系的化学收缩,粉煤灰掺量为30%和40%时混凝土化学收缩值较小。

Effect of Fly Ash Content on Performance of High Performance Concrete with Seawater and Sea Sand

The effect of fly ash content on the performance of seawater and sea sand high performance concrete was studied by carrying out experiments on mechanical properties, chemical shrinkage, pH value, chloride ion concentration, and microstructure. The results show that in order to maintain the stability of reinforcement passive film, the content of fly ash should not be greater than 30% (mass fraction, the same below) under high temperature steam curing and 50% under standard curing. The concentration of free Cl^- in seawater and sea sand high performance concrete fluctuates with curing time, increases first and then decreases sharply in the early stage, and increases slowly in the later stage. The Cl^- concentration under standard curing is significantly lower than that under high temperature steam curing. Seawater and sea sand high performance concrete has early strength, and its strength decreases with the increase of fly ash content. High temperature steam curing significantly improves the flexural and compressive strength of concrete. The more fly ash is added, the more unhydrated particles remain. High temperature steam curing effectively improves the microstructure and compactness of concrete. When fly ash content is too large or too small, it increases the chemical shrinkage of Portland cement. The chemical shrinkage value of concrete is small when the fly ash content is 30% and 40%.