Geo-polymer Concrete with recycled wastes: Concrete for Green Future

Concrete is the inevitable material in construction and without concrete, none can think of a modern world and recent breakthroughs of neoteric civilization. Close upon, next to the water, concrete is the most used material in the world. Consequently, to meet the high demand for concrete, tons of Ordinary Portland Cement (OPC) producing in a day.

But this OPC is directly a threat to the green environment and demolition of energy greatly since production of 1 ton of OPC needs 4700 MJ and 1 ton of CO₂ emission on average [1]. Though OPC is the main ingredient that binds aggregates, OPC manufacturing is energy-intensive and responsible for almost 5% of total global CO₂ emission causing global warming [2], [3].

Therefore, construction industries are rethinking OPC usage. In recent years, Geopolymer Concrete is being popular and replacing OPC due to its eco-friendly manufacturing process and low energy consumption and resources.

Since Geo-Polymer is not relying on calcium carbonate, CaCo₃ like OPC, it reduces 40% to 80% CO₂ emission and 1200 to 1900 MJ/ton. Due to the rapid growth of urbanization,  the demand for housing,  and industries is increasing, increasing the demand for cement which eventually releases a high amount of CO₂ in the environment [4]. Capros et al. [5] reported that the high demand for OPC will soon increase anthropogenic CO₂ emissions by a total of 10%.

These emissions of CO₂ produce a greenhouse effect and are responsible for 65% of global warming [6]. However, the CO₂ emission can be reduced by half by improving the current cement manufacturing technology [7]. New low CO₂ binders are needed to meet the goal of reduction in emission of CO₂, and maybe Geo-Polymers are a high potential solution [8].

Geo-Polymer concrete and cement are more suitable than OPC, and it is a mixture of Aluminosilicate ( Al₂SiO₅)-based materials such as fly ash, blast furnace slag, including either Sodium silicate or Sodium hydroxide (NaOH)  [9], [10].

Geo-Polymer concrete has shown properties on par and superior to OPC, including good resistance against sulfate attack and acid, high compressive strength, and resistance to fire and external heat [11]–[13]. Some recent studies revealed that good compressive strength had been achieved in ambient conditions with low required energy during manufacturing and a huge decrease in CO₂ emission.

As a result, using waste materials such as fly ash and geo-polymer concrete is considered a more sustainable alternative to OPC [14], [15]. However, there are some contradictions about the CO₂ emission. Some researchers claimed that there was slightly less carbon emission in the case of geo-polymer.

In contrast, some others argued that carbon emission was higher than geopolymer concrete [8], [16]. Still, many researchers investigated durability, strength, setting time, hardening, cost, and fuel energy. They found better strength and durability than OPC.

Hanjitsuwan et al. [17] and Onutai et al. [18] reported improved slump, conductivity, tensile strength, and setting time when the proportion of Sodium hydroxide (NaOH)  increased.

In contrast, some researchers suggest embedding a small amount of OPC to sodium hydroxide to get a good initial setting time and Compressive strength [15].

Again, a high population growth rate, rapid urbanization, and industrialization, and a humongous amount of raw materials and natural resources harm environmental and socio-economic status. Rapid Climate change is the most crucial phenomenon closely related to continuous use of natural resources, mismanagement of waste disposal, contamination, and land use, which are the main threat to human existence in this world as they’re jeopardizing the ecology  [19].

Tons of solid wastes are producing from households, industry, construction demolition, etc. For instance, It reported that about 1000 million tires end their useful life every year, and as per estimation, the number of discarded tires will be 5000 million by the year 2030 [20]–[25].

Tires contain various toxic substances, cause mosquito breeding, serious fire hazards and pollute the environment. Das et al. [26] reported that rice husk is an agro-waste that produces more than 20 million per annum globally, jeopardizing the environment, public health, and disposal problems.

It was reported by Siddique et al. [27] that the world’s annual consumption of plastics has increased from 5 million tons in the 1950s to approximately 100 million tons in 2001. Larsen et al. [28] and Brunner et al. [29] reported that glass wastes are non-biodegradable, and 82% of industrially manufactured glasses contain various toxic chemical compositions.

Abdullah et al. [30] and Chindaprasirt et al. [31] reported that its amount is near about 3 million globally. They produced o.1 million palm oil fuel ash (POFA) in Malaysia and Thailand in 2007.

This huge amount of waste will threaten the environment if not properly disposed of, recycled, and re-use for another purpose. The major amount of solid wastes produced in India is shown below in Figure-1 [32].

One of the best solutions to environmentally friendly waste is to use them in construction incorporating with concrete by recycling.

These types of users are more sustainable Recycled material used in construction has a benefit in two ways. One is to provide a barrier in the ongoing use of natural resources, and will reduce another is waste generation rate, and 3Rs – Reduce, Reuse & Recycle are adopted worldwide [33], [34].

The past studies observed that researchers researched recycled waste materials in concrete to manage waste eco-friendliness. For example, Azmi et al. [35], investigated fly-ash-based geopolymer concrete’s compressive strength, replacing fine aggregate with crumb rubber concrete, and they suggested using rubberized geopolymer concrete in non-structural applications.

Nuaklong et al. [36] investigated fly ash-based geopolymer’s mechanical property and fire resistance using rice husk ash (RHA). What is more, Islam et al. [37] investigated the engineering properties and carbon footprint of palm oil fuel ash-based geo-polymer concrete and obtained promising results.

Writer’s Opinions and Solicitations:

In fine, from my above writing and research, I have tried to make the people and researchers understand that this present era demands the replacement of ordinary cement and proper utilization and management of wastes.

Geo-polymer incorporating various waste usage in construction can be a better solution, but this method cannot fully diminish the problem. My humble recommendation to researchers and government is to consider it a global issue and find new methods to properly utilize our resources to save our future generation and our green environment.

Reference:

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