Waste plastic as partial replacement for aggregates- a review

By replacing coarse aggregate as well as fine aggregate with waste plastic known as green innovation. As the years go by, waste plastic increases day by day, since most of the plastic used by human is non-bio-degradable. The idea behind this review is to identify research done by the researchers who uses recyclable material such as plastic obtained mostly from waste plastic that the people had generated around the world by utilisation of waste plastic in becoming of construction materials in order to overcome the environment problem that the society are facing. This paper aim to review the using of waste plastic to replace fine and coarse aggregate and stated the mechanical properties of the concrete. With different percentage replacement of aggregates will affect the different properties such as slump, compressive strength and ultimate strength of the concrete and compare with the control sample in order to find the suitable percentage of the waste plastic to replacement of aggregates for the concrete used. It was found that plastic as replacement for fine and coarse aggregate both have has lower compressive quality of the concrete, almost the same or lower slump test value for ordinary concrete and waste plastic concrete and lower density for the waste plastic concrete compare to the ordinary concrete.


Introduction:
Plastic waste become a major problem effect environment as it is not easy biodegradable. Each year of waste plastic increase as population grow. Recycling using the plastic waste into useful product is one of the solution to decrease the quantity of plastic waste. Used plastic will be landfill and litter on land if without recycle. National Environment shown that 7.70million tones of plastic waste was generated in 2017. Malaysia is the worst 8 country of plastic waste in the world. In order that motivate the researchers and engineers to use plastic waste as a material for the concrete. Concrete has been widely used in the construction work, so determine the properties of the concrete by replacing plastic waste.
Sreenath & Harishankar, (2017) stated that 500 million plastic bags per year was used in different industries. Low-Density Poly Propylene (LDPP) are the major plastic waste and used LDPP replacement fine aggregates are used in concrete mixture with grade M25. Moreover, Jaffe et al., (2015) used high-density polyethylene(HDPE) types of plastic to full or partial replace the fine aggregates in the concrete. Due to others research had shown that increase in plastic ratio in the concrete mixtures decrease the compressive strength. Ghernouti et al. (2009)found that plastic bag had been rejected into nature, so the research is focus studying using rushing the waste plastic bag replacing fine aggregates in the concrete mixtures. Moreover, Amalu et al, (2016)investigates used recycle plastic material to replacing the fine aggregates in the concrete mixture with concrete grade M20 as it is most commonly used in the constructional work. Suganthy etal., (2013) stated that increased waste material as shortage of construction materials. So, waste plastic replacement for fine stated that using plastic waste can decreasing the construction cost and reduce the river sand used protect the environment. Ramadevi & Manju,(2012)exploredthat around12.3% waste plastic which from discarded water bottles. By using replacing sand in concrete mixture to overcome the problem. Arivalagan.S, (2016) conducted experiment to identify of advantages using PET waste plastic as replacement of sand. Guendouz et al., (2016) studied that using Low Density Polyethylene(LDPE) powder with diameter 1.5mm as new material to replace sand in concrete mix design, due to more economic. Kibria et al., (2017) stated that disposing plastic require huge area land space to fill it and utilization of waste plastic for aggregates replacement in concrete to help can overcome the problem. Purnomo

Properties of concrete waste plastic replacement by fine aggregates
Properties of concrete such as slump test, density, tensile strength, compressive strength and split tensile strength replacement of fine aggregates by waste plastic stated as below: Ghernouti et al., (2009) had determine replacing 10,20,30 and 40% of sand by using plastic bag waste(PBW) by increasing percentage of plastic bag waste the fluidity of concrete increase as plastic particles have more smoother surface than sand.Suganthy et al., (2013) reported with same 90mm height of slump, the require of water cement ratio will be higher with increase replacement of fine aggregates by plastic. With replacement of 100% of fine aggregates by plastic, shown that require 0.6 water cement ratio. Amalu et al.( 2016) shown that increasing percentage containing plastic in the concrete, given the highest slump. The slump test shown that increasing when containing more PBW. Containing 40% of PBW showed that highest slump as plastic can't absorb water so increase the fluidity of concrete. Arivalagan.S, (2016)stated that workability increase when increase percentage of PET waste plastic as replacing sand. Guendouz et al., (2016) determined that with increase replacement 40% LDPE powder as sand and increasing workability due to more free water in the concrete mixture.

2.2Compressive strength:
Amalu et al., (2016)stated that decrease in compressive strength increasing plastic contain at 28days. But remain close to the concrete of 10% and 15% contain have fall around 10% and 13% different. Ghernouti et al., (2009) and Jaffe et al., (2015) shown that the compressive strength at 28 days for containing 10 and 20% remain close to the control sample but when replacing until 30% the concrete has turn to unusually weak. The compressive strength has shown much different to the control sample. Sreenath  26% compare to control sample but replace more than 15% the compressive strength less than control sample. Guendouz et al., (2016) determined that at replacement 20% of sand by using LDPE powder increase 30% of compressive strength as concrete have more ductile tolerant. Ghernouti et al., (2009) has determined the bulk density of the concrete cube at 28days. It shown that if containing higher plastic waste the density will be lower so, with containing 40% of the plastic waste is lighter than the others as the plastic waste lighter 70% than the sand. Suganthy etal., (2013) carried out that replacing percentage of sand by plastic, the cube weight decrease and seen like the linear with replacement of sand by plastic. Guendouz et al., (2016) reported that replace 40% of the sand by using LDPE powder decrease 10% of bulk density of the concrete at 28days.

2.4Split Tensile Strength:
Sreenath & Harishankar, (2017) stated that replacing 10% sand by LDPP has increasing to the control sample. (Ramadevi & Manju, 2012) reported that with replacing 2% of sand by PET fibres increasing the split tensile strength but when replacing more than 2% started decrease. Jaffe et al., (2015) determined that replacement 20% of fine aggregates by plastic increased splitting tensile strength compare to control sample but after replace more than 30% start decrease. Aravind & John, (2015) shown that replace 5% of fine aggregates by plastic fines more higher than control sample but more than 10% much lower than control sample.

2.5Flexural strength:
Amalu et al., (2016) shown that with increasing ratio of waste plastic, the flexural strength will decrease. By replacing 25% of sand by plastic has lowest value flexural strength at 28days. Sreenath & Harishankar, (2017) reported that replacing 10% sand by LDPP, the flexural strength has increasing but replacing from 10% to 20% has decreasing. Ramadevi & Manju, (2012) reported that with increase percentage replacement fine aggregates by PET bottle fibres increasing flexural strength but remain same at the 4% and 6% replacement. Aravind & John, (2015)stated that replacement 5% of fine aggregates by plastic fines increase the flexural strength but replace more than 10% start decrease. Guendouz et al., (2016) determined that at replacement 20% of sand by using LDPE powder get the highest flexural strength compared to control sample and replace 10%, 30% and 40%.If replace more than 30% start reducing the flexural strength of concrete.

Types of plastic as coarse aggregate
Plastic can be classify into many different kind where many of the researcher uses different kind of plastic in their experiment.

Compressive strength
The compressive strength of the 28 th S. Vanitha, V. Natrajanand M. Praba (2015) waste plastic increases with maximum of 26.9 n/mm2 and research from Md. Golam Kibria, OsikurRahaman, Md. Ferdous Wahid a found that the compressive strength for the polystyrene polymer waste as coarse agg 955 psi value around 6.59 n/mm2 which also indicated that as increases the compressive strength will show poor bond between cement and polymer materials. Similarly stated that a huge reduction from 34% to 51% to 61% of compressive increases by 20% each. In the other hand, res obtain twice the compressive strength compared to Md. G Wahid and Abdus Salam (2017) due to the fact that the the m weight of cement and sand. In addition to that, another research by Hashmi(2007), although it is not mention the exact compressive strength strength obtain is fairly poor.  fibre.From the result obtain it can be conclude that the percentage of plastic added will greatly affect the quality of the concrete such as the compressive strength, slump test, density.

Slump test
Consistency of mix property concrete whichhad different ability properties of finish ability, mobility, compatibility, stability and place abilitydetermined by YoucefGhernouti, Bahia Rabehi, Brahim Safi and Rabah Chaid (2010), whereas the percentage of plastic increases the fluidity of the concrete increases as well from minimum of 5 cm to maximum of 11 cm. However, research done by Baboo Rai, S. TabinRushad, Bhavesh Kr, and S. K. Duggal (2012), concluded that the higher the plastic percentage the lower the workability of the concrete it gets from the difference of 80mm to 35mm. Also as stated by Lei Gu, TogayOzbakkaloglu (2015) who reviewed Ismail and Al-Hashmi (2008) reported that the slump reduces up to 95% difference compared to the controlled sample concrete when substitute with 20% of plastic content. While another research by Kou

5.Conclusion
The main conclusion that can be drawn from this review is that the compressive strength of all concrete involving plastic as partial substitution most likely to be significantly lower than the ordinary or controlled concrete. It is much clearer when the percentage of plastic content as partial substitution increases the lower the strength of the concrete gets. Same conclusion can be made for the slump test result where higher percentage of plastic lower the slump test which was caused by the irregular shape, angularity as well as the surface smoothness of the plastic used as the substitution. As for the bulk density for the ordinary and plastic concrete it was shown that the plastic concrete will definitely weight lesser compared to the ordinary concrete since it is made out of plastic. This shows that plastic will be a good platform in producing light weight concrete if proper research were to conducted which in other hand will produce good compressive strength in the meantime.
Although some researcher that manage to obtain satisfying compressive strength, it may due to the low percentage of plastic content used as well as types of plastic used which may be an important factor as some plastic material are tougher and stronger than others such as polypropylene. Other than the low plastic percentage used, it may also due to the additional binding agent called plasticizer. As show by Baboo Rai et al. (2012) the addition of plasticizer will increases or improve the result obtain with plastic as substitution for concrete. In addition to that, from the review above it can be concluded that plastic as fine aggregate substitution in concrete manage to produce a much more better result compared to the substitution for coarse aggregate since most of the research conducted with fine aggregate give positive feedback rather than mostly negative result from coarse aggregate as substitution. Therefore, it is much more recommendable to use plastic as partial replacement for fine aggregate instead of coarse aggregate and using of plasticizer will manage to enhance the outcome of the plastic concrete.