Group members SALMAN LATIF (CU-1022-2010)JHENGIR KHAN (CU-1012-2010)

MUHAMMAD RAHIM (CU-1018-2010) MUJAHID NAZEEF (CU-1019-2010) SAJIDEEN KHAN (CU-1054-2010)

Recycling Of Cement Concrete

INTRODUCTION:

CONCRETE: Concrete is a composite material

composed of coarse aggregate , fine aggregate, water and binding material in suitable proportion.

Re-use of demolished concrete in construction It involves breaking, crushing and removing irrelevant and contaminated materials from existing concrete and then using it new construction work.

When a structure demolishes due to any disaster like earthquake, flood etc or a structure completes its life span and we demolish it ourselves, then the demolished concrete is re-cycled for its re-use.

Introduction

The re-cycling and re-use of demolished concrete seems feasible solution in rehabilitation and new constructions after the natural disaster or demolition of old structures.

We are going to re-cycle demolished concrete, to reduce cost of new construction and environmental pollution.

To reduce consumption of natural aggregate and depletion of natural coarse aggregate by utilizing demolished concrete in new construction.

Problem statement

To find different physical and mechanical properties of re-cycled coarse aggregate (RCA) concrete like, workability, compressive strength, tensile strength, flexure strength, modulus of elasticity etc and to compare it with the natural coarse aggregate (NCA) concrete.

To obtain the desired properties of Re-cycled coarse aggregate concrete by adding admixtures, Air Entrainment, Super plasticizers, Retarders, Accelerators, Fly Ash etc.

Objectives

Project Scope

The scope of this project

Review and research of recycled aggregate.

Construct the concrete specimens by using different percentage of recycled Aggregate

. Investigation and laboratory testing on high strength concrete with recycled

Aggregate.

Analyze the results and recommendation for further research area

High-Strength Structural Concrete with Recycled Aggregates

Authors: Nelson, Shing Chai NGOTowards the degree of Bachelor of Engineering (Civil)

Research ConclusionResearch on the usage of waste construction materials is very important due to the materials waste is gradually increasing with the increased of population and increasing of urban development. The reasons that many investigations and analysis had been made on recycled aggregate are because recycled aggregate is easy to obtain and the cost is cheaper than virgin aggregate. Virgin aggregate need to mine but recycled aggregate can ignore this process.

Research Conclusion

This on-going research project is to determine the strength characteristics of recycledaggregate for potential application in the high concrete structural concrete. The studyshows that when the water/cement ratio was decreased, the compressive strength canreach 48MPa. This is classified as high strength concrete and they can be applied in theInfrastructures, which need compressive strength up to 40MPa. Furthermore, with thecheaper price of recycled aggregate compared to natural aggregate, the builders can carryout the construction task with lesser material costs.

Research Conclusion

Another result found in this research is that when reducing the water amount used inrecycled aggregate mixes, tensile strength and modulus of elasticity are also improved.This will give an improvement in general strength characteristics of structural building.Although recycled aggregate can be applied in the high strength structure, but one issuemust not be neglected as recycled aggregate with reduce water content would have lowworkability. Whenever recycled aggregate is applied, water content in the concrete mixhas to be monitored carefully due to the water absorption capacity of recycled aggregate will vary. This type of concrete can only be used under the condition that does notinvolve a lot of handling works.

Research Conclusion

Making samples of Natural coarse aggregate (NCA) concrete and re-cycled coarse aggregate (RCA) concrete in different proportions.

Methodology

Re-cycled coarse aggregate (%)

Natural coarse aggregate (%)

0 10025 7550 5075 25100 0

Compressive strength test: Finding compressive strength of natural coarse aggregate (NCA) and re-cycled

coarse aggregate (RCA) samples at failure and prior to failure.

Tensile strength test: Finding tensile strength of NCA and RCA samples ,by placing it horizontally in

testing machine and applying compressive load. Load is applied along the vertical diameter. Samples will be tasted for two loads i.e. at failure and at its ultimate strength.

MethodologyTests to be performed:

Methodology

Loss Angeles Abrasion Test:

The Los Angeles abrasion test is a common test method used to indicate aggregate toughness and abrasion characteristics. Aggregate abrasion characteristics are important because the constituent aggregate  must resist crushing, degradation and disintegration in order to produce a high quality HMA.

Methodology Tests to be performed:

Loss Angeles Abrasion machine

Flexure strength test:Flexure strength: Material’s ability to resist deformation under loadings. A rod specimen having either a circular or rectangular cross-section is bent until

fracture using a three point flexural or center point test technique. Provides values of modulas of elasticity, flexural stress, flexural strain and the

flexural stress-strain response of the material.

3-point

Methodology

Workability (slump test) : To check consistency of concrete immediately after mixing and after 30 minutes.

Bulk density of fresh concrete : To find out the Bulk Density of aggregate (i.e. unit weight and voids in aggregate). Bulk Density indicates the %age of voids present in the aggregate material.

Air content: This test involves the determination of the air content of freshly mixed concrete from observation of the change in volume of concrete with a change in pressure.

Methodology

Bulk density of hardened concrete : This test involves the determination of unit weight and voids of concrete in hardened form.

Fatigue test : a beam of concrete is tested under repeated loads until failure and at its ultimate strength. Load is applied slowly and in small increments.Load may be repeated tensile ,compressive or flexural.Affects ultimate strength ,strain or deflection.

Methodology

Re-cycling of demolished concrete reduces the use of natural aggregate and thus depletion of natural resources is prevented.

Reduces the environmental pollution as concrete is re-cycled and production of new aggregate for construction is avoided.

Research significance / benefits

As disposal of demolished concrete requires a big area to get disposed, re-cycling allows to utilize that area for other meaningful purposes.

Construction cost can be reduced by a big amount by utilizing re-cycled demolished concrete instead of using natural coarse aggregate for whole new construction.

Can be used as a construction material in new concrete for pavements, shoulders, median barriers, sidewalks, curbs and gutters, and bridge foundations.

Research significance / benefits

Recycled Aggregates in New Concrete by Cement & Concrete Association of New Zealand (CCANZ) Use of Recycled Aggregates in Construction by Cement Concrete & Aggregates Australia.

Recycled Concrete as Aggregate for Structural Concrete Production

( Mirjana Malešev , Vlastimir Radonjanin and Snežana Marinković )

www.astm.org

References