Dear Mohammad Nadeem Akhtar

Have a look at the following articles:

Article The effect of using polyethylene terephthalate as an additiv...

Data Waste Polyethylene Terephthalate as an Aggregate in Concrete

Thank you Dr. Mehran Shahpari for sharing the artciles

actually it depends on the author some of them reported enhancement in the compressive strength

check the following articles:

Article Modelling the mechanical properties of concrete containing P...

Article Flexural Behavior and Analysis of Reinforced Concrete Beams ...

https://www.scientific.net/AMR.795.352

Article Precast use of polymer concrete using unsaturated polyester ...

This article reported decrease in the comprs. strength due to usage of PET fiber

Article Experimental Behavior and Analysis of High Strength Concrete...

Thus, in conclusion using PET in concrete needs optimization of the following criteria

1- the percentage of PET in the concrete

2- PET size or form (particle size fiber size..)

3- other additives

Yes Dr. Mohammad K. Younes this is the point of discussion as some studies show a significant reduction in compressive with the addition of PET waste. However, most of the studies found increment in tensile strength; reduction in compressive strength is a serious issue as we know that compressive strength is the most critical concrete parameter.

Heliyon

Volume 6, Issue 8, August 2020, e04700

Review article

The effect of using polyethylene terephthalate as an additive on the flexural and compressive strength of concrete

Author links open overlay panelRichie.I.UmasaborSamuel.C.Daniel

https://doi.org/10.1016/j.heliyon.2020.e04700

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Under a Creative Commons licenseopen access

Abstract

The annual consumption of plastics in Nigeria has increased drastically and plastic wastes recycling has become one of the major challenges in recent times. Polyethylene Terephthalate (PET) has been selected in this study to ascertain its possible use as an additive in concrete construction. The study used the experimental research design in carrying out its work. The PET was pulverized so that it can mix with the concrete. The pulverized PET was used in concrete with percentages of 5 %, 10 %, and 15 % by weight of conventional fine aggregate. Four types of concrete specimens including the control were prepared. The flexural and compressive strength of the concrete specimens were tested, after a curing period of 3 days, 7 days, 14 days, and 28 days respectively. The result showed that the concrete specimen containing PET at 5 % by weight showed higher compressive strength than other specimens. The flexural strength of concrete specimens containing PET aggregate was below that of the control concrete.

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Keywords

Civil engineeringMaterials scienceStructural engineeringMaterials classMaterials applicationEnvironmental pollutionAdditiveCompressive strengthFlexural strengthPolyethylene terephthalate (PET)

1. Introduction

Concrete is made up of cement, fine aggregate, coarse aggregate, and water. They are used globally for the production of concrete (Kolhapure et al., 2018). Concrete estimated usages are up to 11 billion metric tons yearly because it is the most frequently used construction material globally (Praveen et al., 2013). Due to the usage of concrete, these aggregate resources are getting scares thus requiring an alternative with the passing of each day. The searches of local materials, which can be the best substitute for the concrete material, are matters of serious concern for civil engineers (Praveen et al., 2013). The continuity of the construction industry is very critical, hence seeking aggregates for concrete and other replacements of the conventional aggregates are paramount. The aggregate alternative used in this study is called polyethylene terephthalate (PET).

Polyethylene terephthalate (PET) also known as polypropene is a thermoplastic material used in various applications such as food wrapping, clothing, building materials, rope and constitutes a major fraction of household wastes. In recent years, shredded synthetic fibers such as polyethylene (Wang et al., 2016), polyvinyl alcohol (PVA) (Sahmaran and Yaman, 2007), polyethylene terephthalate (PET) (Foti, 2013) and polyethylene (PP) have been added to the concrete as reinforcements to enhance the mechanical and engineering properties of the concrete.

In a study carried out by Albano et al. (2009), they replaced sand in concrete with polyethylene terephthalate (PET) with two different w/c ratio (0.50 and 0.60). The PET specimen sizes are 0.26 (small) and 1.14 cm (big), respectively. The replacement of sand was done with 10 % and 20 % by volume of PET with particle sizes of 0.26 and 1.14 cm and a 50/50 mix of both sizes. Workability was determined with the help of a slump test. It was observed that there was a higher slump for the blends with 10 % of recycled PET, for determining particle size. A higher slump value was observed for the PET blend with a 50/50 particle size when compared to the blends with PET particles of 0.26 and 1.14 cm. PET affected the slump but it had more effect on slump when there was an increase in the w/c ratio (Albano et al. (2009).

Furthermore, Ramadevi and Manju (2012) used waste PET bottles in fiber form as the partial replacement of fine aggregate in 25Mpa grade of concrete specimens with 0.45 w/c ratio in various percentages 0.5 %, 1 %, 2 %, 4 %, and 6 %. Mix design of 25Mpa grade concrete was done following the guidelines of IS 456 (2000) and IS 10262 (2009). It was reported that a 2% replacement of the fine aggregate with PET bottle fibers gave an appreciable increase in the compressive strength. Beyond 2%, the compressive strength was found gradually reducing.

However, Frigione (2010) used waste unwashed PET bottle (WPET) as a replacement of fine aggregate. 5% by weight of WPET was replaced by the fine aggregate in concrete. Compressive strength was determined at 28 days and 365 days. It was observed that at 28 days, the compressive strength slightly decreased (not lower than 2%) when WPET was added in substitution of natural sand in comparison to the reference concrete. The differences in compressive strength observed at 28 days were alike to those measured at 365 days. The compressive strength at 28 days and 365 days of WPET concrete was between 0.4 %–1.9 % lower than the control concretes.

More so, Choi et al. (2005) reported on the effects of waste PET bottles on properties of concrete. They observed that the weight of conventional concrete can be decreased by 2%–6 % of waste plastics, but there was a 33% reduction in the compressive strength to that of normal concrete.

Similarly, Islam et al. (2011) in his research used PET to replace coarse aggregates in concrete where he shredded, melted, and crushed the collected waste PET bottles. He found out that at 20 % PET replacement of PAC (PET aggregate concrete) at 0.42 w/c ratio; the compressive strength was 30.3 MPa, which was only 9% less than the NAC (Normal aggregate concrete). However, 1.8 cm slump value was observed for 20 % PET replaced PAC at 0.42 w/c ratio which has significantly high workability. It was concluded that PET replaced concrete with a low w/c ratio and high workability can be used for structural concrete applications.

Baboo et al. (2012) reported in their study that with varying percentages by volume of sand was partially replaced by waste plastic flakes in concrete. Waste plastic mix concrete with and without super-plasticizer. Compressive strength tests were carried out for forty-eight cube samples at 3 days, 7 days, and 28 days. The flexural strength characteristic of waste plastic mix concrete was studied using eight beams that were concreted. It was found out that due to partial replacement of sand by waste plastic, there was a minimal reduction in workability and compressive strength, and this can be enhanced by the addition of super-plasticizer.

Industrialization and the considerable improvement in the standards of living have increased quantities of waste plastic rapidly during recent decades. Bottles made from polyethylene terephthalate (PET) deposited in domestic wastes and landfills, which are not bio-degradable cause environmental issues in most regions. Serious problems such as environmental pollution may arise when these wastes are not recycled but rather abandoned (Ahmad, 2014). One of the efficient measure in the management of the waste materials are the recycling and reusing of these waste material, which also prevents pollution and conserves natural resources.

The usage of PET as a partial replacement in concrete is widely known according to literature but using the PET as an additive in concrete is not widely known. This work aims to study the effects of pulverized polyethylene terephthalate as an additive on the compressive and flexural strengths of concrete using specimens tested after 3 days, 7 days, 14 days and 28 days of curing.

2. Materials and method

Portland cement, 19 mm coarse aggregate, fine aggregate, polyethylene terephthalate (PET), and water were used as materials for the concrete. The polyethylene terephthalate was pulverized before it was added to grade 25 concrete at 5%, 10%, and 15% by weight as additive. Seventy-five (75) moulds of dimensions 100 mm × 100 mm x 100 mm and fifty (50) beam of dimensions 500 mm × 100 mm x 100 mm PET concrete specimen was produced according to BS 1881: Part 108 (1983) methodology. These concrete specimens were prepared at the Civil/Structural Engineering laboratory at the University of Benin, Benin City, Nigeria. Flexural and compressive tests were carried out on the specimens for 3 days, 7 days, 14 days, and 28 days curing interval. The third point flexural test method was used to obtain their various flexural strengths according to BS EN 12390–5:2009 methodology. The BS EN 12390–3:2019 methodology was used for the compressive strength test. Other tests such as particle size distribution test for the fine aggregates and the pulverized polyethylene terephthalate (PET), slump tests were also carried out before concreting.

Regression equations depicting the compressive and flexural strength of the grade 25 concrete with both the PET content, fine aggregate, coarse aggregate, cement content, water content, and ages of curing were developed using a statistical package, Design-Expert Software 7.0.0. This software was adopted because it helps in designing the experiments before laboratory works were carried out. The responses (compressive and flexural strength of the PET concrete) on the independent variables (PET content, fine aggregate, coarse aggregate, cement content, water content, and ages of curing of the concrete) were studied. The experimental design was carried out for the PET concrete using Design-Expert software and this produced twenty-five (25) factorial designs as shown in Table 2. The value of 5 %–15 % by weight of the PET and 3 days–28 days of the curing duration were used to produce the PET concrete using the Design-Expert. The responses (compressive and flexural strengths of the PET concrete) were obtained as stated in Table 3. The significance of the model was evaluated using F-test while the coefficient of determination (R2) was used to check the adequacy of the model.

3. Results and discussion

3.1. Particle size distribution test

Particle size distribution tests were carried out on the fine aggregate and the pulverized polyethylene terephthalate (PET) according to ASTM C136 (2014). The results are shown in Figure 1 and Figure 2.

Figure 1

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Figure 1. Particle size distribution test of fine aggregate.

Figure 2

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Figure 2. Particle size distribution test of the PET sample.

3.2. Specific gravity test

Specific gravity was carried out on the samples according to ASTM C127 (2015) methodology. The average specific gravity of the fine aggregate was 2.54 while that of pulverized PET was 1.29 which shows that the pulverized PET is lighter than the fine aggregate.

3.3. Slump test

The test for the slump test for the optimum strength for 0 %, 5 %, 10 %, and 15 % are presented in Table 1 below.

Table 1. Slump test for the pulverized PET and control concrete.

% Of pulverized PET Slump (mm)

0 36

5 7

10 5

15

PET is a remarkably energy-efficient packaging material. ... Although the feedstocks for PET are petroleum based, the environmental impact of PET is very favorable in comparison to glass, aluminum and other container materials.

Thank Dr. Abraham Teym for a nice explanation

Yes, it is synthetic, therfore not durable and consistency

Thank you Dr. Vaibhav Amarsinh Rajemahadik for discussion

Hi Dr Mohammad Nadeem Akhtar

. The compressive strength development of concrete containing all types of PET-aggregate behaves like in conventional concrete, though the incorporation of any type of PET-aggregate significantly lowers the compressive strength of the resulting concrete. See the article :https://www.scielo.br/j/mr/a/Pd9mw5B73Ht4QqZZ7dZmPyG/?lang=en

Also, see the link: Article Compressive and Flexural Strength of Concrete Containing Rec...

Check also the link: https://www.hindawi.com/journals/ace/2019/6942052/

According to (Choi et al, 2005) reported on the effects of waste PET bottles on properties of concrete. They observed that the weight of conventional concrete can be decreased by 2%–6 % of waste plastics, but there was a 33% reduction in the compressive strength to that of normal concrete. Therefore PET bottles reduce the compressive strength of concrete.