再生混凝土微粉活化及其性能研究

Study on activation and performance of recycled concrete micropowder

废弃混凝土微粉组成复杂,活性低。为实现其再生利用,采用机械力活化、热活化、微波活化、化学激发的方式,制备再生混凝土微粉,测试水泥-再生混凝土微粉体系净浆3 d、7 d、28 d抗压强度,并通过SEM观测其硬化体微观形貌。研究结果表明:单纯机械力活化无法有效提升再生混凝土微粉活性。随热活化温度提高,水泥-再生混凝土微粉体系3 d、7 d抗压强度逐渐降低,而28 d强度先增加后降低。随微波活化时间的增加,水泥-再生混凝土微粉体系3 d、7 d抗压强度变化不规律,但28 d抗压强度逐渐提高。热活化后的再生混凝土微粉反应生成较多的AFt相,而微波活化后再生混凝土微粉反应生成较多凝胶体。掺入Ca(OH)_(2),对采用机械力-微波活化微粉的水泥-再生混凝土微粉体系28 d抗压强度有提高作用。结果表明:比表面积为395.2 m^(2)/kg的再生混凝土微粉,微波活化20 min,掺加胶凝材料总量2%的Ca(OH)_(2),活性优于Ⅱ级粉煤灰。

The waste concrete powder had low activity which composition was complex.To realize its regenerative use,it used mechanical activation,thermal activation,microwave activation,and chemical activation to prepare recycled concrete micropowder,analyzed its mineral composition,and the 3 d,7 d,28 d compression resistance of the cement-recycled concrete powder system were tested.The micro-morphology of the hardened body was observed by SEM.The results showed that mechanical activation alone couldnot be effectively to improve the activity of recycled concrete powder.The thermal activation temperature increased,the 3 d and 7 d compressive strengths of the cement-recycled concrete micro powder system decreased and the 28 d strength first increased and then decreased.The 3 d and 7 d compressive strengths of the cement-recycled concrete micro powder system changed irregularly with increasing microwave activation time,but the 28 d compressive strength was gradually increased.More AFt phases were generated by thermally activated recycled concrete powder participating in the hydration reaction,while more gels were generated by recycled microconcrete powder after microwave activation participates in the hydration reaction.Mixed with Ca(OH)_(2),the 28 d compressive strength of the cement-recycled concrete micro powder system had been increasedwhich used mechanical force-microwave activation of micro powder.Recycled micro powder with a specific surface area of 395.2 m^(2)/kg,microwave activated for 20 minutes,mixed with 2%Ca(OH)_(2),the activity was better than grade Ⅱ fly ash that under the same water-to-binder ratio and the same mixing amount.