The Study of Using Recycled Materials in Concrete Production (Crush Glass, Recycled Aggregate, Fly Ash)
CHAPTER ONE
Objectives
General objective
The main objective of this research is to investigate the performance of selected recycled materials as aggregates in structural concrete.
Specific objectives
- To identify which of the selected recycled materials can be used as alternative aggregates for concrete production.
- To investigate the influence of glass, ceramic tiles, and fly ash on both the mix design and the concrete properties.
- To apply a Finite Element Model (FEM) in characterising the structural behaviour of non-conventional aggregates
CHAPTER TWO
LITERATURE REVIEW
Theoretical background
Traditionally, aggregates consist of fine and coarse components. Fine and coarse aggregates can be obtained naturally or crushed (F. Chen & Richard, 2003). In other words, aggregates are a granular material gained from treating natural materials (BS EN 12620, 2002). Because aggregates represent form 60 to 80% of concrete volume, it characterizes the hardness of the concrete. (Nawy, 2005). Aggregates that are retained in sieve No. 5mm is known as coarse aggregates, and aggregates that passed sieve No. 5mm or have sizes less than 5mm is fine aggregates (Kong & Evans, 1978). The shape of surface and the physical properties affects the strength of concrete.
The surface of aggregates provides the bond between the cement paste and aggregates. It could also hold the water of the subsequent hydration reactions (Neville, 1981). Aggregates should be clean, hard, and it did not react chemically with cement (Wilson & Kosmatka, 2011).
The characteristics of aggregate appear in many properties such as; particles size distribution, particle shape, surface texture, unit weight, specific gravity, density, absorption, and surface moisture (Wilson & Kosmatka, 2011). Additionally, the resistance to freezing, dry wetting properties, shrinkage, strength, resistance to acid, thermal properties, and fire resistance represent a major part for determining the quality of aggregates (ASTM C33 /C33M-16, 2000).
The uncrushed smooth and rounded coarse aggregates lead to lower strengths than the crushed aggregates, although the workability will be more (MacGinley & Choo, 1990).
In case of the nominal maximum size of the coarse aggregates for reinforced concrete are normally 20 mm. the maximum size of aggregate depends on the dimensions and the spacing between the reinforcement steel bars. The good practice ensures that the maximum size of the aggregates is not more than 25% of the minimum thickness of the member and the cover. By contrast, the workability concerning the size of the aggregates should be reasonable (Kong & Evans, 1978).
According to (Kong & Evans, 1978), the strength of aggregates has no effects on the strength of the bond between the cement paste and aggregates. The strength of concrete does not depend only on the strength of aggregates, but also on the surface characteristics (BS 812: Part 2, 2002). As a result, the primary purpose of aggregates is to provide the strength and the specific surface. The recommended strength of aggregates is above 100 N/mm2.
Aggregates properties have an influence on the workability in two ways. First and foremost, the particles size distribution, and it is normally determined by sieve analysis test. Second, is the nature of aggregates particles, and it considers the shape, porosity, and surface texture of aggregates (Wilson & Kosmatka, 2011).
CHAPTER THREE
MATERIALS AND METHODS
Materials preparation and properties
General
The experimental program under this research was carried out at the structural laboratory of Jomo Nigeriatta University of Agriculture and Technology in 2016. This chapter presents the type of materials that were used. It also contains the scientific methodology that was followed for; testing the used materials, conducting the proposed experiments, and modelling the chosen structural element. The work plan of the experiment and the research method were demonstrated.
Materials
In this research, the material that were used consist of cement paste (cement and water), and the filler materials (aggregates). Aggregates consist of coarse and fine aggregates which are usually gravel and sand. For the cement paste, Ordinary Portland Cement (OPC) class 32.5R and clean potable water were used. In addition, recycled materials such as; glass, ceramic tiles, and fly ash were used as aggregates, replacing gravel and sand.
Conventional aggregates
Conventional aggregates are gravel and sand. Gravel that was used is crushed stone with maximum size of 20mm. River sand was used as fine aggregates. Sand has maximum particles size of 5.0mm. Gravel and sand passed sieve No. 20mm and sieve No. 5 were used. After sieving the gravel, it was washed once. Therefore, all clay and other deleterious materials were removed.
CHAPTER FOUR
RESULTS AND DISCUSSION
Introduction
This chapter presents the results, analysis, and discussion of the laboratory results. Results were obtained from different tests and for different materials were carried out are presented. Fine and coarse aggregates of both conventional and recycled materials aggregates were tested such as; Particle size distribution, dry- rodded and loss-rodded density, specific gravity, water absorption, impact value, crushing value, and moisture content were also presented in this chapter. Concrete mix design proportions were done according to DOE and ACI method. Tests of the characteristics of concrete were also illustrated. Finally, results which were obtained from the modelling of the beams using ANSYS.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
- General
This chapter presents conclusions and recommendations of the research results. Outcomes lied on the analysis and discussion of the results that have mentioned in the previous chapter. Also, it clarifies weaknesses and areas of further research. Recommendations were mentioned to imply this research in a better way in real life.
5.2 Conclusion
Many tests were conducted for the properties of inorganic recycled materials as aggregates, for a purpose of use in concrete. Particles size distribution, dry-rodded, loss-rodded density, aggregate crushing value, aggregate impact value, water absorption, and specific gravity were tested. These tests were conducted for fine and coarse aggregates, fine and coarse ceramic tiles aggregates, and fine and coarse fly ash aggregates. Sand and gravel were tested as well. The following conclusions were draw;
- In this study, it is proposed “to identify which of the selected recycled materials can be used as alternative aggregates for concrete production”. From the results, ceramic tile aggregates can be applied as either fine or coarse Fine glass aggregates also have suitable results. ACV of the coarse glass was 42.3%, and AIV was 31.0% which are both more than 30%. Fly ash aggregates gave ACV and AIV of 0.02% and 0.004% respectively which are very low results in comparison with other aggregates. Therefore, fine glass, ceramic tiles, and coarse ceramic tiles could be acted as normal aggregates under mentioned conditions.
- Furthermore, the second objective was of this research was “to investigate the influence of glass, ceramic tiles, and fly ash on both the mix design and the concrete properties”. Therefore, Compressive strength was 55MPa and 20.7MPa for glass concrete and ceramic concrete at 25% replacement, and as it was discussed early in chapter four. It was concluded that sand should not be replaced by fine glass and fine ceramic tiles aggregates more than 50%. Also, the gravel should not replace more than 25% by coarse ceramic tiles aggregates. For these replacement, the strength of the concrete was not much affected.
- The fine glass, fine ceramic, and coarse ceramic aggregates were blended upto 50% replacement for fine aggregates, and up to 25% replacement for coarse Based on the results, it concluded that the fine glass, fine ceramic, and coarse ceramic can be blended and used as specifically mentioned replacement.
- In addition, rubber aggregates can be used as normal aggregates either sand or gravel, where high strength is not needed. Rubberized concrete showed high elastic energy, which gave it an advantage than the normal concrete. Wear resistance increased highly by increasing the amount of the rubber aggregates in concrete. This study concludes that rubberized concrete can be used in the construction industry such as; landscaping, sports field ground, architectural finishing, and other engineering applications where normal strength is not
- Beams were made from chosen recycled materials were cast to check the structural behaviour. ANSYS was used to simulate these beams. The results (refer to Figures 18, 4.19, 4.20, and 4.21) were not giving a good agreement with the test results, and the simulation gave the load -deflection curve somehow close to the experimental load – deflection curve.
- The use of recycled materials instead of normal aggregates has financial benefits, and it saves approximately 20% to 30% of the amount of suggested budget in the construction materials.
Recommendation
This research was conducted based on materials’ results that have been mentioned in the previous sections. Any type of glass and ceramic tiles waste can be used without
significant change in the results and fly ash as well. From this research, the following recommendations were set for further studies.
- This study did not consider the effect of the durability. The used recycled materials were not natural, and re-producing them may affect their characteristics with time. Recycled materials should not contain any organic materials and clay. The fine glass and ceramic tiles aggregates can provide more rough surface, and therefore, the strength may
- The method of papering the recycled materials was recommended to be developed to reduce the consumed time and effort.
- The research recommended that sand should not be replaced by fine glass and fine ceramic tiles aggregates more than 50%. Also, the gravel should not replace more than 25% by coarse ceramic tiles aggregates.
- Rubberized concrete was recommended to be used in the construction industry such as; landscaping, sports field ground, architectural finishing, and other engineering applications where normal strength is not needed.
- In fact, many factors affected the simulation results of concrete beam which was made from inorganic recycled materials. The model of the concrete was assumed to be theoretically described, and controlled by the modulus of The values of modulus of elasticity that were obtained experimentally for each material were not that accurate. Furthermore, the modulus of elasticity was assumed to be equal in the whole beam element, and that assumption was not exactly true but it is uncontrollable. Thus, the best estimate for the modulus of elasticity was used. The steel reinforcement was assumed to reach yield strength in the whole reinforced section, which was not also accurate. Therefore, for a better solution, the above assumptions should be considered.
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