RPC强化骨料掺量对再生混凝土强度的影响

Effect of Mixing Amount of Aggregate Intensified by RPC on the Strength of Recycled Concrete

利用活性粉末混凝土(RPC,reactive powder concrete)浆液对再生粗骨料进行浸泡包裹处理得到强化骨料,分析了强化骨料+再生骨料、强化骨料+天然骨料、再生骨料+天然骨料这3种粗骨料组合情况下,强化骨料或再生骨料掺量对再生混凝土不同龄期抗压强度、劈拉强度和抗折强度的影响.结果表明:经RPC浆液强化处理后的再生骨料吸水率降低,压碎值显著减小.强化骨料+再生骨料组合情况下,再生混凝土不同龄期的抗压强度均随强化骨料掺量的增大而降低;而另外两种组合情况下,再生混凝土不同龄期的抗压强度均随强化骨料或再生骨料掺量的增大而增大.强化骨料+再生骨料和强化骨料+天然骨料组合情况下,再生混凝土劈拉强度均随强化骨料掺量的增大而增大;而再生骨料+天然骨料组合情况下,再生混凝土劈拉强度与再生骨料掺量的规律性不明显,表现出较大的离散性.强化骨料+再生骨料组合情况下,再生混凝土抗折强度总体上随强化骨料掺量的增大而减小;强化骨料+天然骨料组合情况下,再生混凝土抗折强度与强化骨料掺量的规律性较复杂;再生骨料+天然骨料组合情况下,再生混凝土抗折强度随再生骨料掺量的增大而增大.折后抗压强度和普通抗压强度一样能较好地反映强化骨料或再生骨料掺量对再生混凝土强度的影响规律,在掺量相同的情况下,折后抗压强度普遍比普通抗压强度低,3种骨料组合中两者比值均稳定在0.93;折后劈拉强度比普通劈拉强度能更好地反映强化骨料或再生骨料掺量对混凝土强度的影响规律,在其掺量相同的情况下,折后劈拉强度基本上比普通劈拉强度高,3种骨料组合的两者比值差异较大.提出了有效水灰比和名义水灰比的概念,有效水灰比是决定再生混凝土强度的最主要因素,若比较强化骨料掺量对再生混凝土强度的影响,必须保持有效水灰比一致,而非名义水灰比一致.

The intensified aggregate was obtained by using RPC（reactive powder concrete）grout for strengthening recycled coarse aggregate.The effect of intensified aggregate mixed with recycle aggregate and natural aggregate,mixture of recycle aggregate and natural aggregate and their mixing ratio on compressive strength,splitting tensile strength and flexural strength of recycled concrete was investigated.The test results show that the water absorption of recycled aggregate mixed with aggregate intensified by RPC grout is lower than that of recycled aggregate,the crush index decreases significantly.For the mixture of intensified aggregate and recycled aggregate,the compressive strength of recycled concrete in different ages decreases with the increase of intensified aggregate content,but for the other two mixtures,the compressive strength of different ages increase with the increase of intensified aggregate or recycled aggregates content.And for these two mixtures of intensified aggregate and recycled aggregate,intensified aggregate and natural aggregate,the splitting tensile strength increases with the increase of intensified aggregate content,but for the mixture of recycled aggregate and natural aggregate,the changes of splitting tensile strength and recycled aggregate content is quite complicated,showing a large discreteness.For the mixture of intensified aggregate and recycled aggregate,the flexural strength,on the whole,decreases with increase of intensified aggregate content,for the mixture of intensified aggregate and natural aggregate,the changes of flexural strength with intensified aggregate content is relatively complex,for the mixture of recycled aggregate and natural aggregate,the flexural strength increases with the increase of recycled aggregate content.Compressive strength can well reflect the influence law of the intensified aggregate or recycled aggregate content on the concrete strength.Under the same circumstances,compressive strength is generally lower than the ordinary one,the mixing ratio of all three mixed aggregate is stable at0.93.Splitting tensile strength can be better than ordinary splitting tensile strength reflecting the influence law of the intensified aggregate or recycled aggregate content on the concrete strength.Under the same circumstances,the splitting tensile strength is higher than that of the ordinary one basically,the mixing ratio of three mixed aggregate is quite different.The concept is proposed of effective water-cement ratio and nominal water-cement ratio,the effective water-cement ratio is the most important factor to determine strength of recycled concrete.To compare intensified aggregate content how to influence recycled concrete strength,effective water-cement ratio of them must stay the same,rather than nominal water-cement ratio.