Potential use of PET and PP as partial replacement of sand in structural concrete

Priscila Marques Correa,Ruth Marlene Campomanes Santana,Ângela Gaio Graeff,Diego Guimarães

doi:10.1590/s1517-707620210003.13009

Priscila Marques Correa, Ruth Marlene Campomanes Santana + Show 2 more

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https://doi.org/10.1590/s1517-707620210003.13009

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Abstract

ABSTRACT The use of polymeric residues in the civil construction has been the target of many studies aiming to reduce the volume of post-consumer plastics in the environment. This work focuses on the viability to use polyethylene terephthalate (PET) and polypropylene (PP) as partial replacement to sand in concrete. PET and PP flakes from post-consumer packings were used as light aggregate to partially replace, individually, 10% in volume of sand. The effect of adding these polymers was investigated in terms of physical, mechanical, durability and morphological properties of the concrete. Physical properties were measured in terms of water absorption, voids content and specific mass. Mechanical properties were measured in terms of compressive strength and elasticity modulus. Durability properties were measured in terms of capillarity water absorption and electrical indication of the concrete to resist to chloride ion penetration. MEV and EDS were used to carry out morphological analysis. DSC curves were carried out to evaluate thermal properties of the polymeric flakes. Contact anlge test was also performed. The partial addition of PET and PP polymers reduced the compressive strength by 20%, whilst the reduction of the elasticity modulus was 16% for PET samples, and almost insignificant for PP samples. The durability results show that the polymers contributed to increase the resistance of the samples to chloride penetration by 15% and 57%, for PET and PP samples, respectively; however, there was an increase in the voids content and water absorption. In the morphological test it is possible to observe a lower interfacial adhesion between PP and the cementions paste in comparison to PET.

Highlights

One ton of concrete is produced annually for each inhabitant of the world, which highlights the environmental impact caused by the production of concrete [1]
3.1 Thermal properties of polymers This test aims to measure the possible hydrolytic degradation of polyethylene terephthalate (PET) and PP in an alkaline environment, which can lead to durability and mechanical problems of concrete in case the degradation will be confirmed
The interface formed with a cementitious matrix and this alkaline medium can favor the hydrolytic degradation of PET [27, 28] and the second at 250oC, due to fusion temperature of PET

Summary

Introduction

One ton of concrete is produced annually for each inhabitant of the world, which highlights the environmental impact caused by the production of concrete [1]. The high cost and shortage of sand in some areas of Brazil has turned the recycling of polymeric residues into an interesting option to replace the natural resource. This is especially because polymeric commodities are largely produced and used [1, 2] so the amount of recyclable post-consumer plastics is abundant all over the world. The use of polymeric residues by the civil construction may be an effective alternative to reduce the environmental impact caused by polymer discarding and to the development of greener materials. Many authors studied the use of polymeric residues, such as polyethylene terephthalate (PET) [1,2,3,4,5] and polypropylene (PP) [1, 6, 7] processed as fibres and flakes for concrete production

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