EFFECT OF CRUSHED CONCRETE AS COARSE AGGREGATES IN PRODUCTION OF CONCRETE

ABSTRACT

In the face of a possible scarcity of natural aggregates in the future in line with sustainable construction, this research investigates the feasibility of the use of recycled coarse  aggregates as an alternative to natural coarse aggregates in structural concrete. The recycled coarse aggregate used in the research was processed from waste concrete.The percentage of recycled coarse aggregates by weight of all in aggregates in the test mixes were 0%, 5% 10% 20% and 30 % respectively. The properties of both natural and recycled coarse aggregates and the fresh and hardened properties of both control and trial concrete mixes were investigated. The results showed that therecycled coarse  aggregates had poor mechanical and physical properties.  Aggregate Impact Value, Aggregate Crushing Value, Compressive strength were lowered with an increase in recycle aggregate content. The recycled coarse aggregates (RCA) had little influence on the hardened density of concrete and an increase in recycled aggregate content led to a decrease in capacity.

CHAPTER ONE

INTROUDUCTION

1.0    Background to the study

Construction and Demolition Waste (C&D) is produced during new construction, refurbishment or renovation of buildings. Demolition waste includes materials from complete building removal as well as partial removals when aspects of the buildings are retained. Construction and Demolition waste includes bricks, concrete, masonry, soil, rocks, lumber, paving materials glass, plastics, aluminum, steel, drywall (gypsum), plywood (formwork), plumbing fixtures, electrical, and roofing materials. Construction and Demolition waste will have increased from time to time proportionate with the development of the town and country. Thus, the necessity of finding appropriate solution to construction and Demolition waste destination must be clear. Reducing, reusing and recycling appear to be profitable alternatives that will increase the lifetime of landfills and reduce exploration of natural resources (Ryu, 2002).

Aggregate is a mixture of materials in the concrete mix. It is a mixture of basic material in which the content consists of three fourths of the concrete mix. In addition to the concrete mix materials are composed of water, cement and additives, if necessary. Because the total quantity of aggregate in a concrete mixture is large, the strength and durability of a concrete depends on the characteristics aggregate itself. Among the key features of an aggregate is the strength of compressive and bond strength, size, shape and surface, the permeability and reactions to chemicals. Besides the physical properties of an aggregate such as relative density, density loam, porosity and absorption of moisture, soundness and resistance to acid and alkali attack also affect the strength. Although however, it is known that concrete strength decreases with increasing water ratio and the ratio of the design in terms of a ratio of cement to aggregate. (Athanas, 2011).

Aggregates can be classified into two classes of coarse aggregate and fine aggregate (sand). Classification is based on the aggregate size where the size of the aggregate Gross is more than 5.0 mm while the size of the fine aggregate shall not exceed 5.0 mm. in concrete mixture, the quantity of both is different classes of aggregate based on the desired design strength of concrete.  Normally, the strength of a concrete can be determined through water content and the quality of cement. Besides other conditions that affect the catalyst, temperature, type of mould and more. For the aggregate size, it affects concrete strength indirectly. Up to now be used in aggregate for produce concrete is appropriate use of concrete. Here, the possibility of new aggregates exist and need to be tested to ensure use appropriate or at least have a function similar to the existing aggregate.  In Malaysia, the construction waste has course a significant impact on the environment and also increasing the concern a significant impact on the environment and also increasing the concern of the society (Chetna, 2006).

1.1 Problem Statement

The main problem of this is to determine whether these crushed concrete can be re-used for construction or for production of new concrete.

Construction and Demolition materials can be recovered through reuse and recycling. The choice of what and how construction and demolition materials can be recovered depends on many factors including type of project, working area and space on the site, cost effectiveness of recovery, project timeline and experience of contractor (Limbachiya, 2000). Many building materials from demolition projects and can be reused as part of the materials to construct a new building for a new project, which will then, involve both the construction and demolition activities. In order to ensure that certain building materials from demolition activities may be reusable, the planners or designer should design the new building with the same size and types of materials as in the old construction.

One of the major challenges of our present society is the protection of environment. Some of the important elements in this respect are the reduction of the consumption of energy and natural raw materials and consumption of waste materials. These topics are getting considerable attention under sustainable development nowadays. The use of recycled aggregates from construction and demolition wastes is showing prospective application in construction as alternative to primary (natural) aggregates. It conserves natural resources and reduces the space required for the landfill disposal.