key: cord-0973255-jhbeqtke
authors: Kilmartin-Lynch, Shannon; Roychand, Rajeev; Saberian, Mohammad; Li, Jie; Zhang, Guomin
title: Application of COVID-19 single-use shredded nitrile gloves in structural concrete: Case study from Australia
date: 2021-11-04
journal: Sci Total Environ
DOI: 10.1016/j.scitotenv.2021.151423
sha: 20cf7db8e7cd508d3a09617659cea61b5bd8dffb
doc_id: 973255
cord_uid: jhbeqtke

The use of single-use nitrile gloves has been on a sharp incline since the Coronavirus pandemic first started in late 2019. This led to a significant increase in the generation of this clinical waste that requires various recycling solutions to reduce its environmental impact from disposal or incineration. This paper explores its application in structural concrete by adding shredded nitrile gloves at 0.1%, 0.2%, and 0.3% of the volume of concrete. The compressive strength, modulus of elasticity, ultrasonic pulse velocity, and SEM-EDS analysis were undertaken to ascertain the effect of different concentrations of shredded nitrile gloves on the mechanical properties, quality of concrete, and its bond performance with the cement matrix. The results demonstrate that the inclusion of up to 0.2% of shredded nitrile gloves can provide ~22% improvement in the compressive strength of blended concrete composites at 28-days of curing. In comparison, the inclusion of 0.3% of shredded nitrile gloves shows improvements of ~20% in compressive strength at 28-days. The SEM-EDS analysis shows a very good bond formation between the nitrile rubber and the cement matrix with no gap identified in the interfacial transition zone (ITZ).

days of the pandemic, the World Health Organisation (WHO) introduced guiding principles around the use of personal protective equipment known as PPE. WHO has requested a 40% increase in the production of disposable PPE (Adyel, 2020) . It has been reported that about 54,000 tonnes of waste PPE were produced per day worldwide as of 22 November 2020 (Purnomo et al., 2021) . The demand is expected to increase at a compounded annual rate of 10. 6%-11.2% until 2027 6%-11.2% until at least (Patrawoot et al., 2021 . This sharp increase in the utilisation rate of PPE is making its safe disposal very challenging. The single-use face masks and gloves forming the majority of PPE are now ending up in landfills or littering the streets (Jaromír Klemeš et al., 2020b; Saberian et al., 2021; Sangkham, 2020) . PPE is being discarded along with other organic and inorganic waste and has also been found littering public places globally (Silva et al., 2020) . Furthermore, COVID-19 related plastic has been observed in marine environments creating a potential new source of microplastics currently generated in our oceans (Anastopoulos and Pashalidis, 2021) .

The majority component of this PPE waste is that of single-use surgical gloves that are made of PVC, rubber, nitrile, or neoprene, with healthcare settings preferring sterile nitrile gloves (Australia, 2020) . Among various types of gloves, the use of nitrile gloves is proliferating (Patrawoot et al., 2021) . With millions of contaminated gloves and other medical waste being generated daily that require safe disposal in landfills or incineration, they pose another environmental challenge for the community (Sangkham, 2020) . Therefore, it becomes imperative for the research community to develop various recycling solutions that can increase the uptake of this clinical waste material. that do touch base on the applications of such plastic-based PPE. Saberian et al. (2021) evaluated the effects of single-use face masks for road constructions concluding that the addition of 1-2% shredded face masks to recycled concrete aggregates resulted in an increase in strength stiffness due to the face masks acting as a reinforcement role when binding with Recycled concrete aggregate (RCA). Also, based on the studies of Kilmartin-Lynch et al. (2021) , the inclusion of shredded face masks to concrete provided a rise in compressive and indirect tensile strength when 0.2% of shredded single-use masks were applied to the concrete mix, noting the increase was due to the fibres being more densely spaced.

Furthermore, Rehman & Khalid (2021) conducted studies on COVID-19 face masks for the amelioration of mechanical properties of fat clay, concluding that the face masks show a reasonable improvement in the unconfined compressive strength. Additionally, Abdullah & Aal (2021) conducted an assessment on the re-use of healthy COVID-19 personal protective materials on enhancing geotechnical properties for road construction and concluded that there was a decrease in maximum dry density; however, an increase was shown in the optimum moisture content that was directly proportional to the number of healthy face masks incorporated. To the best of the authors' knowledge, there is a lack of existing studies on the use of waste PPE and the inclusion of nitrile rubber gloves for concrete applications.

Therefore, to address this research gap, an experimental study was undertaken to investigate the effect of the inclusion of 0.1, 0.2, and 0.3% of shredded nitrile gloves by volume of concrete. Compressive strength, Young's modulus, ultrasonic pulse velocity tests were undertaken in addition to the SEM-EDS analysis to ascertain its mechanical properties, quality of concrete, and its bond performance with the cement matrix. Endeavour equipped with a lynx eye linear strip detector and Cu-Kα radiation. The instrument ran at a 40-kV voltage and 40-mA current. The cement was tested with a counting time of 1 second per step between a range of 5° and 70° 2-theta (2θ) with a step size of 0.01°.

Nitrile gloves that were both latex and powder-free conforming to ISO374-1 (2016) and ISO374-5 (2016) were used in this experiment. These gloves were stored in a sealed container for a 96-hour quarantine period, followed by undertaking the disinfection procedure. The disinfection procedure allowed the gloves to be washed and dried with hot soapy water before being cut to size. The isolation procedures were in accordance with studies conducted in the New England Journal of Medicine outlining how scientists found that SARS-CoV-2, the virus responsible for COVID-19, can be detected on plastics and stainless steel for up to 72 hours after the application to the material (Van Doremalen et al., 2020). Following the isolation procedures is an extremely crucial part of the study; the quarantine and sanitization protocols help ascertain safe barriers when working with potential viruses and microbes to prevent accidental community transmission. It is worth mentioning that except for the isolation process, as one of the disinfection methods, other disinfection J o u r n a l P r e -p r o o f Journal Pre-proof techniques on PPE have been analysed and reviewed for PPE by other scholars (Rowan and Laffey, 2021; Rowan and Moral, 2021) . After the disinfection process, the gloves were cut into long strands using scissors before being cut into smaller pieces of approximately 5 x 15mm. The size fractions were kept similar to the studies by Sharma and Bansal (2016) 

Four concrete mixes were utilised in total for investigating the samples combined with sterile Table 2 shows the mix designs containing different concentrations of shredded nitrile gloves. CM0 signifies the control mix (0% surgical gloves) compared to CM02 implying the mix contained 0.2% surgical gloves by volume. 

For concrete mixing, the dry materials were weighed and placed into the concrete mixer, and mixed together for a duration of 3 minutes. After the initial 3 minutes of dry mixing, the water/superplasticiser mix was gradually introduced into the cement/aggregate mix and thoroughly mixed for an additional 3 minutes. The wet concrete mix was then transferred into After initially curing for 24 hours, the concrete specimens were taken out of their respective casting moulds and put into a curing tank with clean and fresh water to allow them to be cured for the rest of the 28 days at approximately 22 °C. Similar methods can be seen conducted by Zhao et al. (2012) and (Roychand et al., 2018) . After curing for 28 days in water, the samples were removed from the curing tank and allowed to air dry before being prepared for testing. The tops of the compressive strength samples and Young's modulus samples were smoothened off using a concrete grinder. This process is undertaken to ensure a clean contact surface during testing. 

Journal Pre-proof

SEM-EDS analysis was undertaken on the concrete sample containing shredded nitrile gloves using FEI Quanta 200 SEM to ascertain its bond performance with the cement matrix. A small sample was cut out from the fractured exposed part of the flexural strength test sample.

This sample was loaded onto the steel stub with carbon tape, followed by a gold coating to make it conductive for high-quality SEM images. The SEM images were taken at 25x and 1000x magnification levels. Since the images obtained with scanning electron microscopy are in greyscale, the EDS analysis was undertaken to correctly identify the shredded nitrile gloves from the cement paste based on the identified chemical composition. Since the samples were coated with gold, it was deconvoluted during the analysis to remove it from the percentage composition table of the individual spectrum. Figure 1 shows the SEM-EDS analysis of the bond performance of shredded nitrile gloves with cement matrix at 25x and 1000x magnification levels, respectively. A strongly bonded shredded piece of the nitrile glove was identified from Spectrum 1 from its high percentage of carbon content that is typical of organic compounds (nitrile rubber). A large number of the cement concrete particle bonded to the top surface of the shredded nitrile glove can be seen from a 25x magnification SEM image. Spectrum 2 shows high calcium, silicon, and oxygen concentrations that are typical of calcium silicate hydrate gel. Since Hydrogen, a low atomic weight element, cannot be identified by the EDS analysis, it is not shown in the analysis. 

UPV test is frequently used to determine the quality of concrete (Demirboğa et al., 2004) , and as outlined by Jamle et al. (2020) , a UPV result greater than 4500 (m/s) is deemed to be concrete of excellent quality. Figure 2 demonstrates the outcomes of the UPV test after 28day curing. As outlined in Figure 2 , it can be seen that all mix designs from CM01 to CM03 had better results compared to that of the control mix. All samples from CM0 to CM03 fall into the category determined by Jamle et al. (2020) as that of excellent quality. It can be seen in Figure 2 that as the quantity of nitrile gloves increases between CM0 and CM03, so does the overall quality of the concrete present. Consequently, it can be determined that the inclusion of shredded nitrile gloves improves the overall quality of concrete. The increase in the quality of concrete is most likely due to the nitrile rubber aiding in limiting the formation of microcracks throughout the concrete matrix. 

This study outlined a series of experiments studying the effects of incorporating single-use shredded nitrile gloves and the underlying impacts they had on the mechanical properties, quality of concrete, and its bond performance with the cement matrix. This study proposes a potential solution to the PPE waste generated by the COVID-19 pandemic. From these sets of experiments, it can be concluded that:

2. The introduction of single-use nitrile gloves increased the overall results of UPV when related to the control mix, thus increasing the overall quality of the concrete. This is likely due to the nitrile gloves aiding in bond formation, limiting microcracks throughout the concrete compared to the control mix. 

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The authors gratefully acknowledge the RMIT X-Ray Facility for providing training and access to the X-ray facilities. The authors would also like to acknowledge the generous support of the Lowitja Institute, Australia's national institute for Aboriginal and Torres Strait Islander health research. 

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