Abstract

Wherever there are construction activities, there is waste generation. In Ethiopia, the popular material for wall construction is a hollow concrete block that can be broken on the production site or the construction site during loading and unloading and is also found abundantly in demolished buildings. This research aimed at searching for alternative construction materials through recycling and examined the properties of recycled fine aggregate from demolished (old) and construction (new) hollow concrete block (HCB) wastes. The study examined the effect of the recycled HCB on fresh and hardened C-25 concrete properties and the possible replacement percentage of river sand by those recycled fine aggregates. The research also examined the comparative properties of the two recycled fine aggregates. The replacement percentage was in steps of 25%, starting from 25% up to 100%, and 0% represented the reference mix. In general, the recycled fine aggregate exhibited relatively lower physical properties than natural river sand but satisfied the American Society for Testing and Materials (ASTM) standard requirements. The demolished recycled fine aggregate (DRFA) had slightly lower physical properties than the construction recycled fine aggregate (CRFA). The properties of fresh and hardened concrete were decreased as percentage replacement of DRFA and CRFA increased. The optimum percentage replacement of river sand by recycled fine aggregate was between 50% to 75% but was much closer to 75% for that of recycled from construction (new) and closer to 50% for that of recycled from demolished (old) HCB. Recycling wastes can reduce environmental impact due to sand mining and waste disposal as well as partially conserve the natural resource depletion.

Highlights

  • The construction industry’s quick growth has developed a high demand for resource materials

  • A researcher in Ethiopia tried to identify the effects of sand mining on marine biology and concluded that sand mining activities interfere with fish migration and affect the spawning populations early in their life stage by polluting the water, destroying the spawning grounds, removing vegetation, and damaging the fishes [3]

  • This research consisted of preparation of recycled fine aggregate from hollow concrete block (HCB) wastes, characterization of the recycled fine aggregate, and investigation of the effect of recycled fine aggregate on properties of concrete at fresh and hardened states

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Summary

Introduction

The construction industry’s quick growth has developed a high demand for resource materials. A researcher in Ethiopia tried to identify the effects of sand mining on marine biology and concluded that sand mining activities interfere with fish migration and affect the spawning populations early in their life stage by polluting the water, destroying the spawning grounds (especially the gravel beds), removing vegetation, and damaging the fishes [3]. It can affect marine life as well as lead to the depletion of natural resources due to the lack of sustainability/rejuvenation of materials. This research consisted of preparation of recycled fine aggregate from HCB wastes (resizing, crushing, gradation, and purification), characterization of the recycled fine aggregate (silt content, sieve analysis, moisture content, specific gravity, water absorption), and investigation of the effect of recycled fine aggregate on properties of concrete at fresh and hardened states

Literature Review
Experimental Program
Cement
Results and Discussions
Fresh Concrete Properties
Comparison of CRFA and DRFA

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