Recycled Aggregate Concrete

A STUDY ON “RECYCLED AGGREGATE CONCRETE”

BY- NEELANJAN SARKARMURSHIDABAD COLLEGE OF ENGG. & TECH.BRANCH -- Civil engineeringYear -- 3rd year (6th sem)

I would like to express my gratitude to all those who gave me the possibility to complete this project.I am deeply indebted to my my HOD (CIVIL) and the faculty members of my department whose help, stimulating suggestions and encouragement helped me in all the time of research and for completing this project.

I would also like to thank my friends for supporting me a lot .

Neelanjan Sarkar

ACKNOWLEDEGMENT

CONTENTS INTRODUCTION WHAT IS RECYCLE AGGREGATE CONCRETE? CHARACTERISTICS OF RECYCLE AGGREGATE

CONCRETE CLASSIFICATION OF RECYCLE AGGREGATE

CONCRETE PROCESS OF RECYCLE AGGREGATE

CONCRETE HOW TO PRODUCED RECYCLE AGGREGATE

CONCRETE USE OF RECYCLE AGGREGATE CONCRETE APPLICATION OF RECYCLE AGGREGATE

CONCRETE BENEFIT OF RECYCLE AGGREGATE

CONCRETE CONCLUSION

INTRODUCTION

To achieve sustainable issue in construction area, researchers and companies focus on using waste concrete as a new construction material. It is called recycled aggregate which can be produced by concrete crusher.

The aggregates are categorized by size as coarse and fine aggregate.

The characteristic of recycled aggregates could be different by its parent concrete because the parent concrete was designed for its purposes such as permeable, durable and high strength concrete

Its a lower density , elastic modulus, strength and a higher water absorption capacity.

recycled aggregate has a proportional mortar which attached to aggregate, it gives a higher porosity and a lower strength to RAC than the normal concrete.

In addition, since recycled aggregates require a more amount of water than natural aggregate, shrinkage issue could be a problematic to use RAC in practically.

What Is Recycle aggregate concrete

Characteristics of recycle aggregate concrete

Recycle aggregate concrete has a Crushed sound and clean waste concrete of at least 95% by weight of concrete with typical total contamination lower than 1% of the bulk mass

Class 1A RCA is a well graded RCA with no more than 0.5% brick content

Classification & properties of recycle aggregate concrete

Material composition is the basis for classification of recycled concrete aggregate in two main types-

1) Crushed concrete 2) Mixed materialEach of these types is

divided in a class for bound and a class for unbound use

Crushing age

Bulk specific gravity

Bulk density

Absorption(%)

Crushing value(%)

1 days CoarseMediumFine

2.59

2.352.23

1433

12201342

3.2

9.711.2

25.4

n/a

n/a


2.60

2.382.25

1433

12341342

3.4

8.111.4

25.3

n/a

n/a


2.55

2.32

2.23

1433

12781321

2.3

8.0

12.7

24.3

n/a

n/a

1. crushed concrete- This materials generally resulted in increased water demand and decreased workability.

2. Mixed concrete- mixed concrete remain plastic for a short time. This properties are important because they affect the quality and in place cost of the hardened concrete

Process of recycle aggregate concrete

Process of recycle aggregate concrete-

crushing pre-sizing sorting screening contaminant elimination

How to produce recycle aggregate concrete

Crushing and screening systems start with primary jaws, cones and/or large impactor taking rubble from 30 inches to 4 feet.

A secondary cone or impactor may or may not need to be run, and then primary and secondary screens may or may not be used, depending upon the project, the equipment used and the final product desired.

A scalping screen will remove dirt and foreign particles. A fine harp deck screen will remove fine material from coarse aggregate.

Further cleaning is necessary to ensure the recycled concrete product is free of dirt, clay, wood, plastic and organic materials.

This is done by water floatation, hand picking, air separators, and electromagnetic separators.

Uses of recycle aggregate concrete

In a world that is increasingly emphasizing on sustainable construction practices; recycled aggregates have a major role to play.

Recycled concrete is in fact recognized by the LEED Green Building Rating System in its point system. Credit 4 (Materials and Resources) points out that “specify a minimum of 25% of building materials that contain in aggregate a minimum weighted average of 20% post-consumer recycled content material, OR, a minimum weighted average of 40% post-industrial recycled content material.”

Making Concrete more Green

∗ Apart from the obvious benefits, there is one more aspect that of carbonation that occurs during the process of concrete crushing for producing concrete aggregates. Certain areas that were earlier not carbonated absorb carbon dioxide from the immediate environs adding to the already high sustainability quotient of concrete.

For recycled concrete to be used in greater quantities in a country like India, there are certain aspects that need to be taken care of initially.

∗ The setting up of a proper institutional mechanism for taking care of all the steps, such as collection of the construction and demolition waste, transportation, and disposal is of key importance.

∗ Outsourcing of such functions to private enterprise is an idea that the concerned authorities could give a though to in this day and age of open economies.

Challenges in the Indian Context

∗ Set up of the necessary processing infrastructure. ∗ Necessary infrastructure should also be available for

testing the quality of recycled aggregates. ∗ Project developers need to be educated on on-site

waste management plans. ∗ Concerned authorities need to plan an awareness

campaign, using the electronic and online media to promote the virtues of recycled aggregates.

∗ Removing misconceptions about recycled aggregates as being of inferior quality among the public.

STEPS TO BE TAKEN

Scope of application

CLASS-- H No limitation are put on the type segment for concrete & structures with a nominal strength of45 mpa or less.

CLASS –M Member not subjected to drying or freezing – and – thawing action, such as piles ,under ground beam and concrete fill in steel tubes.

CLASS-- l Backfill concrete, building concrete, and leveling concrete

Application of recycle aggregate

There are a variety of benefits in recycling concrete rather than dumping it or burying it in a landfill.Keeping concrete debris out of landfills saves landfill space.Using recycled material as gravel reduces the need for gravel miningUsing recycled concrete as the base material for roadways reduces the pollution involved in trucking material.

Benefit of recycle aggregate concrete

Initial moisture states of RCA is one of the most important variables that impact strength and shrinkage.

When oven-dried RCA is used, strength is used to be greatly reduced but free shrinkage as measured in this study was low.

The creep to free shrinkage ratio for RAC was similar to that of normal concrete at 7 days under restrained conditions.

When greater volume of recycled fine aggregates and fly ash was used, free shrinkage of the specimens was reduced.

Conclusion

The use of recycled aggregate has been found to be better than that of virgin aggregates for certain applications. For example, the physical properties of recycled aggregates make them ideally suited for road base and sub-base. This is because of their physical properties which means less cement is required making them suited for sub-base use. This is in addition to the cost benefits accrued by developers in the process.

Recycled concRete AggRegAte An ideA

Whose time hAs come

Thanking you

Engineering

Recycled Aggregate Concrete