Mechanical Properties Ofplastic Waste As Complementary Aggregate On Solid Concrete Production

The aim of this work was to use plastic waste recycled materials into production of concrete without compromising the compressive strength of the concrete produced.

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The aim of this work was to use plastic waste recycled materials into production of concrete without compromising the compressive strength of the concrete produced. In order to shed light on the compressive strength of concrete made from recycled materials, the thesis reviewed studies in which waste materials are utilised as recycled aggregates in the composition of concrete and presented the results of this synthesis and analysis. It was found that some types of recycled aggregate can be used as a component in the production of concrete without undermining the compressive strength of the concrete produced.

The research implicated that the possibility of utilizing plastic waste material in the production of concrete offers a compelling alternative to waste disposal and the preservation of natural resources.


  1. aggregate: inert granular material such as sand, gravel, crushed rock and clinker used as a main solid constituent in concrete, plaster, tarmacadam and asphalt.
  2. bottom ash: bottom ash is part of the non-combustible residue of combustion in a fur- nace or In an industrial context, it usually refers to coal combustion and com- prises traces of combustibles embedded in forming clinkers and sticking to hot side walls of a coal-burning furnace during its operation. The portion of the ash that escapes up the chimney or stack is, however, referred to as fly ash.
  • coarse aggregate: aggregate which consists largely of particles over 5 mm in diameter.
  1. end-of-waste: end-of-waste criteria specify when certain waste ceases to be waste and obtains a status of a product (or a secondary raw material).
  2. fine aggregate: aggregate consisting largely of particles with a size range of 75 mm–5 mm.
  3. RA (recycled aggregate or recycled aggregates): aggregate composed of recycled materials
  • RAC (recycled aggregate concrete): it is the concrete that had recycled aggregates as a component in the mixing process.
  • Recycled concrete aggregates or secondary aggregate: it is the fine and coarse aggregate that is produced from processing of the crushed original concrete.
  1. Ultimate compressive strength: the stress at which a material or structural component fails in compression or is crushed.
  2. Waste concrete: it is the concrete rubble of demolished structures, and/or the concrete that was rejected during construction of new structures.
  3. Polymer concrete (PC): ) is a composite material which is composed of polymeric resins that act as binder materials of aggregates and microfillers


































1.0                                                        INTRODUCTION

Polymer concrete (PC) is a composite material which is composed of polymeric resins that act as binder materials of aggregates and microfillers. After the addition of different additives (catalysts and accelerators), the binders undergo polymerization resulting in a hardened composite.

The primary difference, compared with cement-based concrete, apart from not containing hydrated cement, is that PC is stronger, more durable, and with lower maintenance requirements [1, 2]. However, portland cement can be used as microfiller or aggregate [3] in PC. Besides these advantages, this composite, which can reach mechanical strengths 4-5 times higher than cement-based concrete [4] keeping the modulus of elasticity in similar values [5], has good chemical resistance and water impermeability [6, 7]. For these reasons, PC is widely used in different applications of civil engineering [1, 8]. It has been used as a major component for the construction of box culverts, underground pipes, trench lines, industrial floors, also as bridge deck overlays, and in reparation tasks of damaged cement-based concrete structures.

In spite of these advantages, PC presents disadvantages that have limited its worldwide utilization. These PC disadvantages may be: expensive cost of resins used as binder agents, suitable precautions that should be applied to achieve a proper curing of PC, and need to use the high quality aggregates to produce PC, when it is compared with cement-based concrete. In order to reduce the high costs of competitive PC, together with recent environmental concern about wastes that end up in landfills, several researches [9, 10] have been conducted to analyze the properties of PC made with industrial byproducts and cement-based concrete residues acting as aggregates.

Commercial epoxy resins and commercial unsaturated polyester resins, whose good results are widely known [11], can be found among the classic resins used as binder agents. Recently, plastic wastes and bottles from polyethylene terephthalate (PET) have been used for unsaturated polyester resins production, which were used as the binder agent to produce recycled PC. The results of these investigations were very promising. They opened an important way to reduce costs and environmental pollution caused by wastes disposal.

For their part, in order to achieve high mechanical performances by using expensive resins, high quality aggregates are commonly used. This optimum combination results in PC that fulfills such requirements. In this respect, a wide variety of materials are used, including quartz, silicates, gravel, limestone, calcareous, granite, clay, natural basalt, and calcium carbonate. Somewhat similar to the resin replacement, aggregates and microfillers have also been replaced by solid wastes from various industrial fields. Demolition materials from concrete and masonry wastes, residual glass from blasting operations, industry development and electrical production wastes such as fly ash or silica fume,  crushed polymer concrete and mortar, rapid-cooled slag from the steel production process, or residual sands from foundry industries, have been studied as mineral aggregates and microfillers in the production of recycled polymer concrete (RPC). These investigations concluded that it is feasible to produce high quality RPC based on recycled solid wastes and performances of resultant materials could be improved by optimizing different variables of the mixtures. Such variables were, in any case, aimed towards varying the ratios of resins : microfillers : aggregates used, the particle-size distributions of aggregates used, as well as their nature, and type of resins added to the mixtures.

Focusing the interest in the case of recycled aggregates from concrete and PC, the obtained results were very encouraging. Generally, as the amount of binder increases, the void ratio in PC mixtures decreases, while compressive strength and flexural strength increase. Although this is affected not only by such variables but also by grading and mixture of microfillers and aggregates used. Besides these facts, as a gradual increase in the content of the recycled aggregate takes place, a reduction in the modulus of elasticity of the PC can also be seen.

On the other hand, the use of aggregates from recycled PC has shown the feasibility of using them as a competitive alternative, compared with natural aggregates, producing only changes in mechanical strengths within 1% of significance statistic level [18]. In the case of portland cement-based concrete there is a wide range of previous investigations related with the partial or complete substitution of coarse and fine natural aggregates by recycled aggregates from concrete [21–23]. Results of those studies generally concluded that the cement-based developed concretes with recycled aggregates offered less mechanical strengths and lower elastic modulus.

Recently, the growing environmental awareness on the reuse of solid wastes from disused infrastructures, alongside the difficulties to obtain high-quality natural aggregates, leads to the study and incorporation of these waste materials as PC components. In this research, the fundamental sources of aggregates are the replaced concrete sleepers or those whose manufacture has been faulty.

Railway sleepers are essential elements in railroads; their main role is to distribute loads from the railway vehicles to the underlying ballast bed. Particularly, in the case of high-speed railroads, loads are very demanding. Therefore, materials that compose these elements should provide the maximum performance [24]. In the case of concrete sleepers, the most used composition for their manufacture in Spain is siliceous aggregates, limestone, and basalt. Their mechanical properties are very suitable; consequently, they may provide an excellent source of high-quality recycled aggregates.

From these considerations, this paper presents the results of experimental research on PC made with unsaturated polyester resin, microfillers, and recycled aggregates from crushing, cleaning, screening, and sieving replaced concrete sleepers or faulty ones. Furthermore, it also attempts to assess the mechanical properties of new PC, by varying the resin content, the nature of the recycled aggregate, and the particle-size distribution of microfillers blended.

1.1                                           BACKGROUND OF THE STUDY

Globally speaking, there is an evident need to recycle more and thus, reduce the amount of waste being disposed into landfills that are rapidly filling [2]. The construction industry in particular is notorious for the creation of vast amounts of waste [3]. It is only sensible that this industry should do more to develop new ways of bringing waste that can potentially be recycled back into the production line.

Because concrete is the most widely used construction material in the world today [4], this thesis focuses on a specific component that accounts for 80% of the volume of concrete [5], that is, aggregates. Aggregates are becoming increasingly scarce in urban areas. That means that aggregates have to be transported from longer distances into the urban areas, which is where most buildings are constructed. Stringent environmental laws and growing public awareness towards a more sustainable society have driven organisations and governments to search for a replacement to aggregates. [6.]

This thesis aims to provide an overview of recent studies that have been carried out to investigate the incorporation of recycled aggregates, hereafter referred to as RA, into the production of concrete. In particular, this thesis examines the results of those studies in regard to the compressive strength of concrete blocks made with RA, hereafter referred to as recycled aggregate concrete, or simply, RAC. The goal is to identify if RAC has achieved similar mechanical performances as normally expected from conventional concrete.

Considerable amount of research has been carried out with different types of materials. This thesis presents the most widely researched waste material used as RA, that is, concrete waste. In addition, other less commonly used waste materials are introduced. These are: general plastic, polyethylene terephthalate (PET) bottles, tyre rubber and coal bottom ash. It is important to note that each of these waste materials would require a book in their own right to explain their mechanical characteristics as RA.

Furthermore, the current Finnish situation of incorporating RA into concrete is discussed. Given that of all aggregates utilized in Nigeria in 2013, only 1% derived from a recycled source [7], this thesis aims to examine the reasons behind this almost non-existent application of RA in Nigeria.

Overall, the purpose of this thesis is to increase the awareness of the scarcity of aggregates in the metropolitan areas and to present alternatives that replace the use of aggregates. By diminishing the amount of aggregates extracted from nature, the use of RA creates an opportunity to preserve natural resources and offers and assists the pursuit of a greener planet for the present and future generations.

1.2                                                     AIM OF THE STUDY

Plastics have become an essential part of our modern lifestyle, and the global plastic production has increased immensely during the past 50 years. This has contributed greatly to the production of plastic-related waste. The aim of this work is to study the reuse of waste and recycled plastic materials in concrete mix as an environmental friendly construction material.

1.3                                                   SCOPE OF THE STUDY

Plastic aggregate (PA) is produced by mechanically separating and processing plastic waste. A life cycle analysis of mixed household plastics shows that mechanical recycling provides a higher net positive environmental impact than the recovery of energy or land-filling2-4. Different types of plastic waste have been used as aggregate, filler or fibre in cement mortar and concrete after mechanical treatment. They include: polyethylene terephthalate (PET) bottles, polyvinyl chloride, PVC pipes, high density polyethylene, HDPE, thermosetting plastics, mixed plastic waste, expanded polystyrene foam, polyurethane foam, polycarbonate, and glass reinforced plastic5-21. The details about the generation of PA as well as the properties of concrete containing PA are presented in this work.

1.4                                                PROBLEM OF THE STUDY

Plastic aggregate (PA) in concrete has several negative effects such as poor workability and deterioration of mechanical behaviour. The strength properties and modulus of elasticity of concrete containing various types of PA are always lower than those of the corresponding reference concrete containing NA only. The decrease in bond strength between PA and cement paste as well as the inhibition of cement hydration due to the hydrophobic nature of plastic are the reasons for the poor mechanical properties of concrete containing plastic.


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