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.

Re use of Demolished concrete in construction

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

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 (%)

0 100

25 75

50 50

75 25

100 0

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

aggregate (RCA) samples at 2, 7 and 28 days strength.

Tensile strength test: (at the age of 28 days)

Finding tensile strength of NCA and RCA samples, by placing it horizontally in compression testing machine and applying compressive load diametrically along its length.

Failure of the sample takes placer along the vertical diameter.

MethodologyTests to be performed:

Methodology

Flexure strength test: (at age of 28 days)

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 center-point or third-point loading test technique. Provides values of modulus 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. Load is applied slowly and in small increments. Load may be repeated tensile, compressive or flexural.

Methodology

Re-cycling of demolished concrete reduces the use of natural aggregate and thus depletion of natural resources in 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