废混凝土骨料对GRC性能影响研究

Influences of waste concrete aggregate on properties of GRC

针对废混凝土排放量巨大、再利用程度低以及GRC长期性能下降的问题,采用50℃热水加速老化的试验方法,研究了废混凝土取代天然砂、粉煤灰和硅灰对GRC性能的影响。结果表明,废混凝土骨料取代率为30%时,可提高GRC的抗折强度,同时还可以减缓GRC抗折强度下降的速度;粉煤灰取代率30%时,对GRC早期抗折强度不利,但可提高其后期强度,同时可较大程度地减缓GRC抗折强度下降的速度;粉煤灰取代率30%,同时废混凝土骨料取代率30%时,对GRC抗折强度及抗折强度下降速度的影响较粉煤灰单独使用时效果要好;粉煤灰与硅灰同时分别以20%及10%取代水泥时,对GRC抗折强度有较大的提高作用,同时也可减缓GRC抗折强度下降的速度;粉煤灰取代率20%、硅灰取代率10%、废混凝土骨料取代率30%时,对GRC抗折强度的提高作用最大,对GRC抗折强度下降的延缓作用较废混凝土骨料单独使用或粉煤灰与硅灰同时使用时要大。

Aimed at the problems of the large emission of waste concrete, low level of reuse and property degradation of GRC in the long term, the paper studied the influences of waste concrete, fly ash and silica fume on the performance of GRC, with the method of accelerating GRC aging. The results showed that the flexural strength of GRC can be enhanced when the replacement ratio of waste concrete is 30%, at the same time it can slow down the declining of GRC flexural strength; When the replacement rate of fly ash is 30%, though it has an disadvantageous effect on the early flexural strength of GRC, it can improve the late strength, simultaneously it can slow down greatly the speed of the decline of GRC flexural strength; When the replacement rate of fly ash and waste concrete aggregate is 30%, it has better effect on flexural strength and fall speed of flexural strength than when fly ash is used alone; When PoO cement are replaced simultaneously by 20% fly ash and 10% silica fume, the flexural strength of GRC is greatly improved, meanwhile, it can also slow down the speed of the decline of the flexural strength of GRC; The improving effect on flexural strength of GRC is greatest when natural sand and PoO cement are replaced simultaneously by 30% waste concrete, 20% fly ash and 10% silica fume, and it has better effect on delaying the speed of the decline of GRC flexural strength than when waste concrete aggregate is used alone or fly ash and silica fume are used simultaneously.