Use of Recycled Coarse Aggregate for Prepacked and Postpacked Concrete

1)采用两种混凝土，强度等级分别为250和570kgf/cm~2。采用颌式破碎机进行一次破碎，将再生粗骨料的级配调整为15~40 mm和10~40 mm。从普通混凝土和高强混凝土生产的再生粗骨料A和B的物理性能分别为2级和3级，相当于劣质骨料。2)置换骨料混凝土灌浆砂浆使用化学外加剂，当水胶比为50%，矿物掺合料与胶凝材料之比为20%，流动时间为16~20s时，砂浆的砂胶比为0.8。即使将单位含砂量的5%替换为粉碎原始混凝土时产生的0.15 mm下的粉尘，砂浆的流动时间、渗漏率、膨胀率和抗压强度也与不含粉尘的砂浆相同。3)用新购买的钻芯机从大型混凝土砌块中取样芯样。使用再生粗骨料的预填和后填混凝土的抗压强度与使用碎石的情况几乎相同。掺入粉尘的砂浆和改变再生粗骨料的级配不会降低强度。混凝土强度等级越高，两种再生粗骨料混凝土的抗压强度和动弹性模量越高。4)阐明了低质量的再生粗骨料和低能量产生的粉尘用于预填和后填混凝土的可能性。

The summary of research results on above mentioned title is as follows.1) Two types of original concrete were used and the strength levels were 250 and 570 kgf/cm^2. The first crush was done by a jaw crusher and the grading of the recycled coarse aggregate was adjusted to 15 to 40mm and 10 to 40mm. The physical properties of the recycled coarse aggregate A and B which were produced from the normal and high strength original concrete were classified into grade 2 and 3 respectively and were equivalent to low quality aggregate.2) The chemical admixtures for the grout mortar of replaced aggregate concrete was used, and the sand-cementitious material ratio of the mortar was 0.8 when the water-cementitious material ratio and mineral admixture-cementitious material ratio were 50 and 20% respectively and the flow time range was 16 to 20 seconds. Even if 5% of unit sand content was replaced by the 0.15mm under dust produced during crushing the original concrete, the flow time, bleeding ratio, expansion and compressive strength of the mortar were the same as the case of the non-dust mortar.3) The core test specimens were sampled from large scaled concrete block by a new purchased core boring machine. The compressive strength of the prepacked and postpacked concrete using recycled coarse aggregate was almost the same as the case of using gravel. The strength was not reduced by using the mortar with the dust and by changing the grading of the recycled coarse aggregate. The higher the strength level of an original concrete, the higher the compressive strength and dynamic Young's modulus of both concretes using recycled coarse aggregate.4) It was clarified that there was an every possibility of using the low quality recycled coarse aggregate and the dust produced by the low cursing energy for the prepacked and postpacked concrete.