THE EFFECT OF CRUSHED CONCRETE AS COARSE AGGREGATES IN THE PRODUCTION OF CONCRETE
In the face of 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 the recycled coarse aggregates had poor mechanical and physical properties. Aggregate Impact Value, Aggregate Crushing Value, Compressive strength were lowered with an increase in recycleb 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.
TABLE OF CONTENTS
TABLE OF CONTENT vi
LIST OF TABLE ix
LIST OF FIGUREx
CHAPTER ONE: INTRODUCTION
1.0 Background of the study 1
1.1Problem Statement 2
1.2 Aim and Objectives 3
1.3 Justification of the study 4
1.4 Scope of the study 5
CHAPTER TWO: LITERATURE REVIEW
2.0 Literature Review 6
2.1Crushed Aggregate Concrete7
2.2Size Distribution 7
2.3 Classification of Aggregate 8
2.4 Sources of crushed Aggregates 8
2.5 Material Properties 9
2.5.3 Fine Aggregate 10
3.0 Research Methodology 11
3.1 Slump test 11
3.2 Density test 12
3.3 Compressive strength Test 13
3.4 Aggregate Impact Value Test 13
3.5 Sieve Analysis 14
3.6 Water Absorption 14
3.6 Materials Used 14
CHAPTER FOUR: RESULTS AND DISCUSSION
4.0 Results and Disucussion 15
4.1Aggregate Impact Value and Aggregate Crushing Value 15
4.2Sieve Analysis of Fine Aggregate 17
4.2.1 Sieve Analysis 19
4.3Sieve Analysis of coarse Aggregate 21
4.4 Compressive strength of Natural Aggregate (Granite)23
4.5 Water Absorption Rate29
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.0 Conclusion 30
5.1 Recommendation 30
LIST OF TABLES
Table 3.1: Proposed Mixes Proportions by weight 14
Table 4.1a: Aggregate Impact and Crushing Value Test 15
Table 4.1b: Aggregate Impact and Crushing Value Test 16
Table 4.2b: Below shows the particle size distribution of fine aggregate used. 17
Table 4.2c: Below shows the particle size distribution of coarse aggregate used 21
Table 4:3 Compressive Strength for Natural Aggregate 23
Table 4.4: Compressive Strength for Recycled Aggregate at 5% replacement 24
Table 4.5: Compressive Strength for Recycled Aggregate at 10% replacement 25
Table 4.6: Compressive Strength for Recycled Aggregate at 20% replacement 26
Table 4.7: Compressive Strength for Recycled Aggregate at 30% replacement 27
LIST OF FIGURES
Figure 4.1: Particle size distribution of fine aggregate 16
Figure 4.2: Particle size distribution of crushed concrete 18
Figure 4.3: Particle size distribution of Coarse Aggregate 22
Figure 4.4: Compressive Strength for Natural Aggregate 23
Figure 4.5: Compressive Strength for Recycled Aggregate at 5% Replacement 24
Figure 4.6: Compressive Strength for Recycled Aggregate at 10% Replacement 25
Figure 4.7: Compressive Strength for Recycled Aggregate at 20% Replacement 26
Figure 4.8: Compressive Strength for Recycled Aggregate at 30% Replacement 27
Figure 4.9: Compressive Strength of Varied Percentage of Crushed Concrete 28
Plate 1: Pictorial Illustration of workability of concrete 11
Plate 2: Determination of density of concrete 12
Plate 3: Testing of compressive strength of concrete
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).
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.
The aim of this research work is to investigate the impact of crushed concrete in production of new concrete.
i. To determine the physical and mechanical properties of aggregate.
ii. To investigate the influence of varying percentage of crushed concrete on the mechanical properties of concrete.
1.3JUSTIFICATION OF THE STUDY
In recent years, concrete has diversified its production. Condition this affects the aggregate consumption indirectly. In addition, demand against increasing the concrete economic conditions are good with increase of aggregate demand. In these situations, it is not appropriate to rely on one source of aggregate with continuing increase in demand and it will cause the shortage by natural aggregate in future. Thus, several alternatives should be established for the preparation of the possible effects on the aggregate demand in the future.
There are few studies have undertaken to produce a new aggregate. Most of the newly generated aggregate consists of waste materials such as glass, tires, broken bricks, concrete and other waste again and some of the results of this study have been practiced in the construction industry.
Therefore, this study examined the effectiveness of the use of crushed concrete produced from concrete waste in order to test the suitability and strength. It is hoped that this study will be the beginning of efforts to use recycled aggregate in construction material in the future.
1.4SCOPE OF THE STUDY
The scope of this research work is to determine the effect of crushed concrete as coarse aggregate in the production of new concrete.
2.0 LITERATURE REVIEW
The function of aggregate has the influence of the construction quality, therefore, the type and quality of aggregate are very important to be concerned. The fine and coarse aggregates generally use 10% to 25% of the concrete volume (20% to 35% by mass) and will influence the concrete’s freshly mixed and hardened properties, mixture proportions, and economy. Moreover, fine aggregate usually consists of natural sand with particles around 4.75mm (0.2 in); then in terms of coarse aggregate it is usually combination of gravels or crushed stone with particles larger than 4.75 mm (0.2 in.) and generally between 9.5 mm and 37.5 mm (3/8 in. and 11/2 in.) (Gomez, 2003). Then, the natural aggregate consists of gravel and sand can be used after those materials through processing. The process of materials for natural aggregate is only minimal process through the dug or dredged from a pit, river, lake, or seabed (Gomez, S.M 2003).
Moreover, in terms of Crushed Coarse Aggregate use will influence high water absorption of crushed aggregate, of concrete (Fumoto and Yamada, 2006). This is due to the migration of water absorbed by the aggregate to the paste around particles of aggregates, then, the water absorption will influence volume of water and pores in the paste. Recycled fine aggregate has high water absorption because it contains a large quantity of hydrated cement paste from the demolished concrete. Increasing the level of cleanliness of crushed concrete, in terms of the amount of mortar adhering to aggregate particles, has been found to improve the workability, mass per unit volume and compressive strength of the concrete and to reduce the air content (Montgomery and Sturgiss, 1996).
2.1 CRUSHED AGGREGATE CONCRETE
The crushing characteristics of hardened concrete are similar to those of natural rock and are not significantly affected by the grade or quality of the original concrete. Recycled aggregates produced from all but the poorest quality original concrete can be expected to pass the same test required of conventional aggregates. Recycled aggregate can be batched, mixed, transported, placed and compacted in the same manners as convention concrete. Special care is necessary when using fine recycled aggregate. Only up to 10% - 20% recycled fine aggregate is beneficial. The aggregate should be tested at several substitution rates to determine the optimal rate.
2.2 SIZE DISTRIBUTION
Generally, a series of successive crushers are used, with oversize particles being returned to the respective crusher to achieve desirable grading. The best particle distribution shape is usually achieved by primary crushing and then secondary crushing, but from an economic point of view, a single crushing process is usually most effective. Primary crushing usually reduces the Construction and Demolition concrete rubble to about 50 mm pieces and on the way to the second crusher, electromagnets is used to remove any metal impurities in the material (Tsung, N.A 2006)..