Production of Groundwater Resistance Mortar Using Glass Sand and Polypropylene Fibres

Over the years, the accumulation of waste has become a serious problem due to the difficulty of disposing of it and the increase in resulting pollution due to the industries expanding in the world. This led to the increased production of adverse waste [1]. These solid wastes involve wood, iron, glass, rubber, ceramics, and plastic. According to the requirements of the World Bank for solid waste management, most countries in the Middle East and low-income countries produce some 1.3 billion tons of solid waste every year which is estimated to rise to 2.2 billion tons around 2025 [2]. Wastes like polyethylene and PP have increased in Malaysia due to incorrect consumption of waste materials. Current rates of waste use are as follows: polyethylene (4.6 ton/day), PP (12.8 ton/day) [3, 4]. India consumes 8 million tons of plastic items year (2008), rising to 12 million tonnes by 2012. Plasticized PVC is wasted greatly because it is utilized to make pipes, window framing, floor coverings, roofing sheets, and wires [5]. Various campaign methods, including landfill, ocean disposal, and burning, have been implemented to mitigate the environmental impact of waste garbage.

However, the outcomes are disappointing. Landfilling hinders plant growth, ocean disposal generates floating garbage, and burning emits poisonous gasses (smoke). Burning plastics or carbon-containing materials releases CO and CO₂ gasses. CO over 35 ppm is harmful [6, 7].

Therefore, engineers and researchers are trying to look for solutions that reduce such solid waste to make the environment cleaner by focusing on providing scientific information on the recycling of this solid waste in a way that maintains the ecological balance. Recently, research indicated the possibility of using glass effectively in concrete by directing the use of glass waste in the concrete production as a partial replacement of cement or sand, where it can be used as a binder that takes an important role in the reaction during hydration in addition to being a filler [8-12].

Concrete specimens that contain glass as a partial replacement of fine aggregates yielded higher compressive strength values than the mixtures in which glass was used as a partial replacement of cement [9]. Other studies indicated that the use of GS as a partial replacement of cement by (10-20%) led to a barely noticeable increase in compressive strength [13-15]. While Esmaeili and Al-Mwanes [16] studied the high-performance glass concrete manufactured from GS that was used as a partial replacement of cement with differing addition rates. The results obtained indicated that the concrete resulted has high mechanical property included compressive, splitting, and bending strength. In addition, the ability of chloride to penetrate the resulting type of concrete decreased, which led to the resistance of this type of concrete to the chloride ion. The main ingredient in glass is silica. Milled (ground) GS as a partial cement substitute in concrete could improve sustainable, energy-efficient, and cost-effective construction of infrastructure. While grinding waste glass into microparticles, pozzolanic interactions with cement hydrates are expected to yield secondary calcium silicate hydroxide (C-S-H), the remaining portion, which has not undergone complete reaction, will function as a filler that seals the pores or diminishes their size, so resulting in denser and more resistant concrete [17]. GS particles can enhance the mechanical characteristics of concrete through their pozzolanic activity [18]. It is important to highlight that GS, which has a particle size of 100 micrometers or smaller, demonstrates a reactive characteristic that is comparable to the pozzolanic reaction observed in concrete [19]. The particles that are finer than 1.18mm show signs of less expansion than normal fine aggregates after conducting an expansion test. When glass is crushed to finer particles of 5 microns, it was found that concrete specimens achieved an increase in compressive strength, which can be accounted for in terms of the pozzolanic nature of fine GS [20]. Wang et al. [21] conducted investigations on the effect of using glass as fine aggregate with three different mixtures, and obtained compressive strengths of 21, 28 and 35 MPa, with replacement ratios of (0-80) %. The obtained results indicated that the compressive strength decreased in a significant way when the replacement ratio was raised to more than 20%. Because of the high brittleness of ordinary concrete, which has low flexural, fracture, and strength properties, it is easy to break after it affects its durability. Therefore, concrete reinforcement is resorted to using fibers that contribute to a clear reduction in the brittleness of concrete and the development of durability [22, 23].

Europe produces around 29 million tons of plastic trash annually, mostly thermoplastic PP and polyethylene (PE). PP representing 19% of European plastics, is harder and more thermally and chemically resistant than PE despite being less dense. PP is used in food wraps, automotive parts, toys, and pipe manufacturing. Nearly 25% of European plastic garbage is thrown away [24]. Landfilled plastic is both a missed opportunity for renewable energy production or recycling and a direct harmful impact on the environment, such as garbage from the oceans entangling ocean organisms or microplastics produced by the degradation of larger waste plastic and transported through the atmosphere even to remote locations with known health risks [25]. Bagherzadeh et al. [26] investigated the effect of using PP fibers in different proportions and different lengths to improve the performance of lightweight concrete. The lengths of the used PP fibers were (6, 12) mm with proportions (0.15, 0.35%) of the cement weight. In comparison with the non-reinforced lightweight concrete, the lightweight concrete enhanced with PP fibers 12 mm long and at a rate of 0.35%, gave an increase of 30.1% in the flexural strength and a 27% increase in splitting tensile strength. Increasing the presence of fibers in the LWC mixture, in addition to the ability of PP fibers help to prevent the occurrence of capillary cracks. All the above-mentioned reasons combined led to improving the quality of the mechanical properties of concrete. Furthermore, Patel et al. [27] explained that research for evaluating the performance of reinforced concrete with PP fibers concluded that the presence of fibers in ordinary concrete allows failure due to spalling, while the nature of failure in fiber-reinforced concrete is swelling in the transverse direction. As far as the compressive strength is concerned, it is improved by (8-16%), as well as the splitting tensile strength. Cho et al. [28] compared the post-cracking behavior of steel fiber-reinforced concrete with PP-reinforced concrete. It has been shown that the use of PP fibers delays stress reduction after cracks occurred in concrete which improves the flexural properties. Also, after the stabilization of cracks, concrete containing PP fibers can withstand any increase in residual load despite the presence of large wide cracks [29, 30]. This research combines the use of glass waste as a percentage of sand at rates of (25, 50, and 75%) and observes the effect of this on the properties of concrete. In addition to the use of PP fibers to improve the splitting tensile strength of the mixtures used. Ahmed et al. [31] investigated the effect of using PP fibers as a partial replacement of sand to produce concrete, where six concrete mixtures were made via using PP fibers as a partial replacement of sand with percentages (0, 8, 16, 24, 32 and 40) %. The laboratory results showed a decrease in unit weight and compressive strength with the increase in the percentage of PP fibers. The percentage of replacing 40% achieved the lowest compressive strength.

The purpose of this study is to exploit waste such as GS to reduce its negative cumulative impact on the environment and produce sustainable concrete with better characteristics compared to traditional concrete, where glass sand contains high silica in its composition, which improves the mechanical properties of the produced concrete. Since concrete suffers from weak tensile strength, exploiting PP fiber waste to improve the mechanical properties of concrete is necessary. Several mechanical tests, such as compressive, flexural, and splitting tensile strengths, were conducted. In addition, physical tests such as water absorption and weight density were conducted to further cover the effects of the waste materials used. In summary, we attempt to decrease the harmful effects of groundwater-containing salts on concrete hydraulic structures by combining the two waste materials and eliminating pollution. The solution suggested through this study is to use a sustainable solution represented by adding waste glass as a percentage of fine aggregate with PP fibers to concrete exposed to groundwater containing harmful salts such as chlorides and sulfates.

The mixing proportion was selected depended on the ACI 211 [34]. While the compressive strength test conducted based on BS EN 1015-11 [35]. The standard ASTM C496/C496M-11 [36] used to test the splitting tensile strength. The flexural strength tests were conducted following ASTM C348-14 [37]. The density of specimens test conducted according to ASTM C138/C138M-14 [38]. ASTM C1403-15 [39] used to determine the water absorption of specimens. The molds were carefully cleansed, with the inner surfaces lubricated to prevent mortar adherence upon hardening. The molds were filled with mortar and compacted using a vibrating table to eliminate any trapped air. The upper surfaces of the specimens were smoothed using a trowel and left in the laboratory for 24 hours. Ultimately, specimens were removed from the molds and placed in a water tank for 7, 14, 28, 56, and 90 days to undergo the curing process before being tested.

In the present study, GS with 25%, 50%, and 75% was utilized as a partial sand replacement via using PP fibers in 1% of a mixed volume exposed to tap water and groundwater curing. The following conclusions can be drawn:

(1) The compressive strength increases for specimens cured by tap water were 2.84 and 4.26%, while the improvement for specimens cured by groundwater was 2.67 and 4.21% for replacement percentages of 25 and 50% GS, respectively. The presence of PP fiber in mortar in small ratios plays a positive role in improving the mechanical properties of mortar. However, the specimens treated with groundwater were slightly lesser. When the percentage of glass ratio increased to 75%, the compressive strength decreased at all ages for example at 28 days decreased by 3.94% for curing with tap water and 4.24% for curing with groundwater.

(2) All specimens with GS and PP fibers (excluding those with 75% GS) improved splitting tensile strength with tap water, better than groundwater. This improvement improved with cure age (excluding those with 75% GS). Tap water-cured specimens with 25 and 50% GS increased 4.19 and 5.93% after 28 days. Groundwater-cured specimens increased by 4.45 and 5.78% compared to those without GS. Curing with tap water and groundwater decreased the splitting tensile strength of specimens containing 75% GS by 2.6% and 2.7%, respectively.

(3) The increment of flexural strength specimens cured by tap water reached 17.5, 30, and 38.75%, while the increment of specimens cured by groundwater reached 29.76 to 38.38% for specimens containing 0, 25, and 50% GS, respectively, compared with traditional mortar specimen. It is noted that in all mechanical tests, the results at 90 days were the highest compared to other ages.

(4) The highest density is reordered for mortar specimens (free of GS and PP), where the density reached 2360 and 2265.6 kg/m³ for specimens cured by tap water and groundwater, respectively. The results indicated that the density reduction increased with the GS ratio increase, with the lowest density recorded at 75% GS (2160 and 2073.6 kg/m³) for tap and groundwater curing, respectively.

(5) The values gathered from this study indicated that when the glass contents increased, the mixtures were more absorbent. The percentage increase in absorption for specimens containing 50 and 75% GS and cured by tap water was 6 and 12.5%, respectively, compared with 2% for specimens containing 25% GS. The same specimens cured by groundwater exhibited 15.7 and 9.5% increments in absorption.

(6) Possibility of produce mortar has a density of 2192 kg/m³ and has a good mechanical property will open the gates to produce parts of the construction materials like the interlock bricks and light curbstone used in roads shoulders.

It is clear from these results that GS could strengthen the mechanical properties of the mortar produced (Rich of silica) if it is used at a suitable level of replacement. The results indicated that the ratio of 50% GS was the best ratio in all mixes and curing types depnds on the improvement in mechanical properties gained such as the compressive and flexural strengths, which is recommended to be the optimal ratio, and may help to utilize the glass waste to produce new concrete or mortar eco-frindly to the environment.