摘要：采取降低水灰比，掺入适量粉煤灰，高效减水剂和对再生集料表面进行处理等措施，通过SEM研究了再生混凝土界面过渡区（ITZ）的结构与性质。试验结果显示：降低水胶比，掺入20%的粉煤灰和2.5%高效减水剂(对水泥),可使再生混凝土ITZ结合更加紧密,抗压强度得以提高。在同样条件下，采用1%PVA溶液处理过的再生集料,有利于提高新拌再生混凝土的流动性,同时,硬化混凝土的强度也有所提高。
关键词: 再生混凝土; 界面过渡区; 结构和性能 (毕业设计 )
中图分类号: TQ172 文献标识码: A 文章编号:1671-4431(2004)11-0029-04
1.introduction
随着可持续社会的发展,人们更加注意到对再生混凝土的研究和应用,再生混凝土由作为循环利用的再生集料废渣料混凝土和老混凝土配制而成,再生集料包含一定数量的水泥,灰泥,其中还有一些独立的快体,另外有一些吸附在天然集料的表面,因为再生混凝土有比天然集料更大的孔隙率和更强的吸水性,这对混凝土的性能产生了极大的影响,因此对再生集料表面进行处理可以很明显的降低它的孔隙率和改善再生混凝土的耐久性,事实上,进行表面处理后的再生集料改变了再生集料和水泥浆体之间的结构和性质,特别是在水泥浆体—集料的过渡区.
2 实 验
2.1 材料
用作再生集料的老混凝土样品取自某工厂的行车梁,预制构件,龄期约为40年;老混凝土中粗集料的主要物相为白云石和方解石,粒径较大,最大粒径约50mm,以20~30mm粒径居多;老混凝土结构致密,少有碳化。老混凝土经破碎、过筛后用作再生混凝土的粗集料,其有关的物理性质见表1。细集料采用河砂,物理性质见表1。
Study on the Structure and Properties of Interfacial Transition
Zone(ITZ)of the Regenerated Concrete
Abstract :With reducing W/C ,incorporating a suitable fly ash and superplasticizer,disposing the surface of recycled aggregate(RA)etc,this paper researched the structure and properties of interfacial transition zone(ITZ) of the regenerated concrete(RC) through SEM .The experimental results showed that when reducing W/C,incorporating 20% of fly ash (FA) and 2.5% of superplasticizer
(to cement)in the RC ,ITZ of the RC was combined much more compact and the compressive strength was enhanced..Under the same condition ,using disposed RA with 1% PVA solution ,the fluidity of fresh RC can then be enhanced and the compressive strength of hydrated RC with 1%
PVA solution ,the fluidity of fresh RC can then be enhanced and the compressive strength of hydrated RC can also be enhanced slightly.
Key words:regenerated concrete ;interfacial transition zone(ITZ);surface disposed
1 Introduction
Increasing attention is paid to the investigation and application of regenerated concrete (RC) for the sustainable development of society[1-3]. The RC is prepared with demolition waste concrete or old concrete as the recycled aggregate (RA). RA contains a certain amount of hardened cement mortar, some of which have a form of independent lumps, and others adhere onto the surface of natural aggregate. Since RA has a greater porosity and a higher water absorption capacity than natural aggregate, which has a greater influence on the performance of RC; consequently, the treatment of the surface of RA can obviously reduce its porosity and improve the workability of RC[4,5]. Virtually, the surface pretreatment of RA changes the structure and property between RA and fresh cement paste, especial between hardened cement mortar in the RC and fresh cement paste (i e, interfacial transition zone).
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