Manjunath M, Research scholar, Walchand College of Engineering, Sangli, and Prakash K B, Principal, Government Engineering College, Haveri

This paper presents an experimental investigation on the effect of alternate wetting and drying on recycled aggregate concrete with different supplementary cementitious materials (SCM). The supplementary cementitious materials considered in the present study include fly ash, silica fume and ground granulated blast furnace slag used as a partial replacement of cement. The compressive strength of concrete subjected to 45 cycles of alternate wetting and drying is determined for the various%age replacements of natural coarse aggregates by recycled aggregates.Test results indicate that the durability aspects of recycled aggregate concrete as evaluated by alternate wetting and drying test can be improved through the use of SCM admixtures.

Introduction

The utilization of the recycled aggregates created from processing construction and demolition waste in new construction has become more important over the last two decades. There are many factors contributing to this, from the non-availability of new material and the damage caused by the quarrying of natural aggregate and the increased disposal costs of waste materials. Construction and demolition waste are generated mainly from demolished concrete and masonry structures. Due to advances in manufacturing of crushing machinery and recycling processes, it became possible to scale or crush down large masses of construction and demolition waste into smaller particles to produce recycled aggregate at acceptable cost.

Recycling of concrete waste is necessary from the viewpoint of environmental preservation and effective utilisation of resources. The utilization of recycled concrete aggregates is particularly very promising as 60-80% of concrete is made of aggregates [3].

A review of several early studies indicated that, compared with concrete mixtures containing natural aggregate, the mixture containing recycled-concrete aggregate generally gave at least two-thirds of the compressive strength and modulus of elasticity, and show satisfactory workability and durability [5]. In general, the effects of using recycled-concrete aggregate instead of natural aggregate are (a) reduced compressive strength (b) reduced modulus of elasticity (c) increased drying shrinkage and creep and (d) increased damping capacity. The reduction in strength ranges between 12 to 25%, while, the reduction in modulus of elasticity varies from 10 to 33%. Creep of recycled aggregate concrete is found to be 30 to 60% greater and drying shrinkage 20 to 50% greater than concrete made with natural aggregates [7 & 1].

Recycled aggregates are composed of the original aggregates and the adhered mortar. It is well known that physical properties of recycled aggregates are very much dependent on the type and quality of the adhered mortar. The adhered mortar is a porous material; its porosity depends upon the water-cement ratio of the recycled concrete employed [4].

As the adhered mortar is often prone to attract more water than the original aggregate, the absorption capacity of recycled aggregates is known to be greater than that of natural aggregate; this is believed to be one of the most significant factors affecting the recycled aggregate concrete. Although there is no clear-cut relation between the strength of concrete and the water absorption of aggregate used, the pores at the surface of the particle affect the bond between the aggregate and the cement paste, and may thus exert some influence on the strength of concrete [6].

When the aggregate to be used is limiting the strength of concrete, the overall performance is usually affected; in this case, the obvious solution is to improve the performance of the aggregate and other concrete components. The factors that contribute to increased strength and performance include use of supplementary cementitious materials and chemical admixtures [2].

Durability of concrete is defined as its ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration. Water, which is the primary agent of both creation and destruction of many natural materials, happens to be central to most durability problems in concrete. In porous solids, water is known to be the cause of many types of physical processes of degradation. The movement of the various fluids through concrete takes place not only by flow through the porous system but also by diffusion and sorption [5].

An exposure condition which cannot be avoided, is the exposure of mature concrete to alternating wetting and drying – a temperature cycle frequently met with in nature. Alternating wetting and drying represents much more severe conditions because a build-up of salts within the concrete can occur in consequence of the ingress of water, followed by evaporation of pure water, with the salts left behind [6].

For concrete produced with recycled aggregates, the volume of pore space in concrete, as distinct from the ease with which a fluid can penetrate it, is measured by absorption, thus testing of concrete subjected to alternating wetting and drying cycles serves as a measure of durability index.

Main objective of this experimentation is to study the effect of alternate wetting and drying on concrete produced by replacing natural coarse aggregates by recycled aggregates and on recycled aggregate concrete with different supplementary cementitious materials. The grade of concrete adopted is M20, as it is the widely used structural concrete. Three supplementary cementitious materials (SCM) considered for the study are fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF). Each of the mineral admixture is used independently in the recycled aggregate concrete. The different%age replacement of natural coarse aggregates by recycled aggregates considered are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%. The compressive strength of concrete subjected to 45 cycles of alternate wetting and drying is determined.

This section of the article is only available for our subscribers. Please click here to subscribe to a subscription plan to view this part of the article.

Click Here
To Know More or to Contact the Manufacturer
Please let us know your name.
Invalid Input
Please let us know your Designation.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.
Our other Value-Added Services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Invalid Input
Invalid Input
Invalid Input
The demand for structural strengthening of ageing structures is growing rapidly in buildings, industrial structures, infrastructure projects like bridges, dams, etc. Structural Strengthening also

Read more ...

Durability and strength are two most important criteria and requirements for the long-term performance of concrete structures against weathering action, chemical attack and abrasion. Any deficiency

Read more ...

Cement is a key binder component of concrete production in the building industry. It is a complex hydraulic binder, made up of four main clinker components; alite (Ca3SiO5), belite (Ca2SiO4)

Read more ...

FAIRMATE manufactures a complete range of construction chemicals and provides cost-effective solutions and world-class services to the Speciality Construction Chemicals Industry in alliance with leading

Read more ...

Corrosion of concrete is a major issue and many concrete structures on adverse environment have experienced unacceptable losses in terms of serviceability, ultimately requiring replacement

Read more ...

Cement is the most used industrial commodity required for development, but it is also responsible for high GHG emissions; so there is a need to create a balance between the nation’s growth and environment sustainability

Read more ...

Cement concrete is the most consumed materials on the earth next only to water. The ingredients used in preparing concrete are not sustainable. The ingredients are responsible for causing global warming. The most

Read more ...

India’s ready-mix concrete (RMC) market is projected to witness a 7-9% CAGR in the next five years. This growth is predominantly driven by the increased investments in the development of infrastructure throughout

Read more ...

Concrete, being a physical mixture of cement, aggregate (sand and crushed rocks), and water, is the key construction material across the world. There is now a huge demand for infrastructure which has increased concrete

Read more ...

There is a need for technologically advanced concrete admixtures for the ready-mix industry that meet industry codes and meet or exceed the demands of challenging construction applications and adverse placement conditions

Read more ...

High Performance Concrete (HPC) is seeing major applications in the field of civil engineering constructions such as long-span bridges, tunnels, high-rise buildings, huge complexes, highway pavements, and more, since

Read more ...

Concrete being the second largest consumed material after water needs attention towards sustainable construction with an increase in infrastructure. The world is moving towards innovative techniques and methodologies

Read more ...

Co-processing of waste in the cement industry is an advanced and innovative recovery process whereby energy is recovered, and the non-combustible part of the waste is reused as raw material.

Read more ...

Traditional masonry units are not sustainable and eco friendly due to consumption of fuel or cement. It is essential to find sustainable alternatives. This paper reports about preparation of geopolymer bricks, masonry

Read more ...

Geo-polymer mortar (GPM) is proven for its strength, durability and sustainability [2 & 3]; strength of GPM is a function of alkaline to binder ratio, and has an adverse effect on consistence properties of mortar

Read more ...

Comparison of Reinforced and Pre-Stressed Concrete Building Frames This article discusses pre-stressing of concrete to get lighter and slender beam sections for six different four storied concrete building frames of different spans/lengths by the application of post-tensioning

Read more ...

Ready mix concrete (RMC) is the first choice for projects requiring concrete. The term ‘ready mix’ is used to describe a process where concrete is pre-made at a plant and delivered in batches to job sites. It is a convenient

Read more ...

When we talk of Primers that are applied before the paint work, what comes to mind are the Acrylic Primers. However, since the last few years, White Cement-based Primers are gaining popularity amongst the construction

Read more ...

Chemistry is truly relevant for concrete because chemistry controls the life/durability of concrete. It explains why cement hardens and the interaction between cement and its environment. Dr. S.B.Hegde at Udaipur Cement Works

Read more ...

Concrete is considered the world’s most versatile, durable and reliable construction material, next only to water. It is the most consumed material requiring large quantity of cement, fine aggregates, course aggregates

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.