Gainful utilization of waste glass for production of sulphuric acid resistance concrete
Introduction
Production of excess amount of waste has forced countries all around the globe to use fertile grounds as disposal units [1]. Disposal of glass waste also adds to this uncontrolled dumping issue which is troubling ecological balance around the globe. Glass being non-biodegradable in nature causes severe damage to the environment. To overcome this issue of improper glass waste handling, different methods have been considered for disposal of different varieties of waste glass (WG) [2]. Out of the many types of glass products, Avancini et al. (2018) [3] showed that borosilicate based WG can be used for the preparation of glass – ceramics which are magnetic in nature. These can be used in fields of biomedical engineering and magnetic resonance imaging to name a few. Monich et al. (2018) [4] used WG of both boro – alumino – silicate and soda lime origin for the production of glass foam with the aim of reducing the cost involved in producing the same. Disposal of solar panels also produces WG, which Jimenez - Millan et al. (2018) [5] evaluated as a degreaser for the manufacture of ceramic bricks. According to the authors, addition of WG had helped in reducing the high plasticity of the clay mineral sepiolite without which this mineral would be difficult to work with. WG can also be used in the manufacturing of clay blocks where the surplus residue was successfully employed by Mao et al. (2018) [6] to immobilize heavy metals in electroplating sludge.
The variety in types of materials that can be produced using WG does not end here. WG cullet recovered from urban waste was tried as a replacement of water glass in the manufacturing of fly ash grounded geopolymer concrete. The results as presented by Toniolo et al. (2018) [7] suggested that such a replacement will further reduce the CO2 emission associated with production of an already eco-friendly construction material. WG can also be utilized in production of abrasives. Being rich in silica, WG can be consumed as fine aggregate for concrete production [3]. The above waste utilization techniques might lessen a significant amount of WG which would in turn reduce the associated health problems.
This research aims in improving the extent of utilization of WG in concrete and hence some studies with waste glass as substitute of river sand are discussed below. Batayneh et al. [2], Du H and Tan KH [3] and Borhan [4] noticed increase in performance of concrete mixes due to pozzolanic activity of WG. On contrary to this Taha and Nounu [5] Ismail and Al Hashmi [6] and de Castro and de Brito [7] also noticed drop in hardened properties of concrete mixtures at different replacement levels river sand which is basically related with nature of WG used in these studies.
For concrete structures to last for their entire service life, durability parameters play a key role. Resistance to deterioration of concrete when exposed to acidic atmosphere (sulphuric acid) is also an alarming concern. When exposed to such a medium, concretes longevity reduces which starts with surficial damage. This damage indicates the growth of reaction products which strip out the concrete surfaces, leading to change in mass, size and shape of the concrete [14].
Considerable progress has been done in the past to study the change in chemistry this composite would exhibit when subjected to an acidic medium [15]. The studies conclude that H2SO4 reacts with Ca(OH)2 which is present in concrete to form gypsum [16], [17]. Gypsum further bonds with calcium aluminate hydrate present in concrete and develops ettringite [18], [19], [20], [21]. Ettringite has greater volume than the products from which it is generated and leads to the concrete’s deterioration [22].
There are studies that can be traced where effect of incorporation of glass in concrete on acid attack mechanism has been evaluated. On such study presented by Chen et al. (2006) [23], Ling et al. (2011) [24] and Ling and Poon (2011) [25] proved that when concrete prepared with waste electronic glass, recycled glass and waste glass bottles as an alternate for river sand showed reduced vulnerability to damage. The researchers demonstrated that usage of glass waste in concrete enhances its physical and mechanical properties thus displays positive consequence towards mass loss and strength variation in comparison with reference concrete (see Table 1).
Numerous researchers have evaluated the work on hardened characteristics of concrete samples with waste glass (WG). The prime motive of this study is to examine the variation produced in performance of concrete samples when WG and Portland pozzolana cement were blended together and subjected to acid curing. Secondly an attempt has also been made to study the microstructural variations happening in the cement matrix due to presence of WG when subjected to attack from an acidic medium. The techniques employed to judge this are listed in the subsequent sections.
Section snippets
Research origination
Many researchers have noticed rise in hardened physical and mechanical properties by using waste glass in concrete mixtures as a replacement of river sand in range of 18% – 24% [2], [8], [9], [10], [11], [12], [13], [25]. However, Bisht and Ramana [2] verified 21% substitution level as an optimum percentage. In the present study similar substitution levels were considered to achieve optimum substitution level when composites made with and without WG are exposed to acid attack (sulphuric acid).
Materials
In the current work fly-ash based Portland pozzolana cement with specific gravity of 3.11 was employed. This cement type satisfied the stipulations set by IS: 1489 (1991) [26] and ASTM C340-67 [27]. Elemental composition of cement captured using Energy-dispersive X-ray Spectroscopy (EDAX) is reported in Table 2 and Fig. 1. River sand having specific gravity 2.66 is used which belonged to the grading curve classified as Zone 2 according to IS: 383–2016 [28]. The particle size grading of sand is
Fresh property
Fresh property of concrete mixture was inspected by conducting compaction factor test in accordance with IS 1199 (1959) [38]. The test equipment contains 2 hopper vessels with hinges attached at the bottom of these vessels with a cylinder placed at the base. Freshly prepared concrete was allowed to pass through these pre-oiled vessels by opening the hinge. Then the placed concrete was allowed to fall in cylindrical container. Upper layer of the cylindrical container was levelled and then weight
Workability
In this research, quantity of chemical admixture to be included while mixing was precisely examined to retain their compaction factor value as 0.9 as illustrated in Fig. 5. From this figure we can see that the requirement of super – plasticizer increases with rise in WG percentage. When related to reference concrete, the mix with 24% of WG (WG24) has 33% more super – plasticizer content. This might be because, WG particles are finer than sand, have sharp edges and are more angular in shape when
Conclusions
Slight variation has been noticed in weight and compressive strength when WG incorporated concrete cubes were exposed to acid curing. This is associated with early reaction of waste glass with H2SO4 thus results into formation of sodium sulphate which does not allow decomposition of cementitious materials. However, notable changes have been detected for WG0 mix concrete sample due to production of ettringite and gypsum. The formed sodium sulphate, ettringite and gypsum were spotted by
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
Authors are thankful to Materials Research Centre, MNIT Jaipur for their support in conducting FESEM, FTIR, TGA / DTA and XRD analyses.
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