Performance of Recycled Aggregate Concrete

Abstract

Owing to the shortage of space for land reclamation in Gaza Strip, it is difficult to dispose tons of construction and demolition waste generated daily from construction activities and destroying of building during Israeli campaigns in addition to the huge amount of ex-settlements destroyed buildings. Adoption of recycled aggregate from concrete waste thus becomes a burning issue. For this reason, it is suggested that clearing the debris from destroyed buildings in such a way as to obtain recycled concrete aggregates to be reused in concrete production that could well be a partial solution to environmental pollution. For this study, the physical and mechanical properties of recycled aggregate concrete produced were investigated and tested. Most of studies held in Gaza strip on recycled aggregate produced from construction and demolition wastes, focused on using recycled aggregate as granular material for base coarse roads and for concrete mixes for concrete hollow blocks . This thesis, aims to find the possibility of the structural usage of recycled aggregate concrete in lieu or mixed with natural aggregates, based on better understanding of behavior of recycled aggregate in concrete structures. experimenting fresh and hardened concrete, mixtures containing recycled aggregates. The percent of fine recycled aggregate in the all recycled aggregate was about 5.0% so it was excluded from the study. 0 %,30 % and 60 % of coarse recycled aggregate was used in the experimental tests . Two kinds of natural fine aggregates were used , Gaza sand and crushed stone . The experimental tests focused on, physical properties density and workability, and mechanical properties compressive strength , flexural strength and bond strength between concrete and steel. More than 120 concrete specimens were tested for the study. The tests showed that the workability of recycled aggregate is lower than the workability of natural aggregate concrete ,the slump test was about 1.0cm slump for 60 % coarse recycled aggregate concrete and increases as the percent of recycled aggregate decreases . The compressive strength of recycled aggregate concrete with 60 % recycled aggregate, is about 76 % of natural aggregate concrete. The compressive strength increases as the percent of recycle aggregate in concrete mixes decreases. As the percent of Gazasand increases the compressive strength of recycled aggregate concrete decreases for the same percent of recycled aggregate . The concrete of recycled aggregate exactly behaves as natural aggregate concrete in flexural tests and the flexural strength have same percent of corresponding compressive strength (3.2√fc kg/cm2) . The bond strength between deformed steel bars of recycled aggregate concrete is about 1.4 times natural aggregate concrete. Future studies on recycled aggregate are recommended, like the effect of mitigation of alkali and silica on recycled aggregate concrete, the durability of recycled aggregate concrete and the effect of fire on recycled aggregate. Developing specifications and standards are necessary in order to encourage use of recycled aggregate in lieu of natural aggregate.