Reusability of Ashes for the Building Sector to Strengthen the Sustainability of Waste Management

Reusability of Ashes for the Building Sector to Strengthen the Sustainability of Waste Management

Neslihan Doğan-Sağlamtimur (Niğde Ömer Halisdemir University, Turkey), Ahmet Bilgil (Niğde Ömer Halisdemir University, Turkey) and Baki Öztürk (Hacettepe University, Turkey)
DOI: 10.4018/978-1-5225-5757-9.ch014

Abstract

Coal, as a fossil fuel, is used to generate power for industrial operation. Two types of industrial ash, including fly and bottom ash, which are solid residues arising from coal burning, are dumped to the landfill with no care for reuse. These wastes consist of environmental issues needing to be resolved. The ashes are used in the production of cement, concrete, aggregates, adobe, brick, and insulation material, in the construction of dam and road, and in geotechnical applications. Construction material is a form of cementitious materials based on ash as source material and it is an environmentally friendly choice against Portland cement releasing a large amount of greenhouse gas to the atmosphere during energy intensive manufacturing process. It is a good alternative to the solution of environmental problems based on the waste ashes in the international scale. In addition to its economic benefits, it is suitable for industrial symbiosis. This chapter explores the reusability of ashes for the building sector to strengthen the sustainability of waste management.
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Introduction

In industrial applications, the process of raw material and production is based on a single support; and waste generations in most industrial organizations are an inevitable result. Coal, as a fossil fuel, is used to generate power for industrial operation. Two types of industrial ash, including fly and bottom ash, which are solid residues arising from coal burning, are dumped to the landfill with no care for reuse. These wastes consist of environmental and technical issues needing to be resolved. Depositing or disposal of these wastes leads to significant environmental pollution. Some environmental problems of the ashes are dust, damaging agricultural products, rain and wind erosion, radiation and infiltration of toxic substances in soil. Therefore, environmentally undesirable results occur concerning agricultural products, water and air quality, wildlife and the region's economic status (Doğan-Sağlamtimur et al., 2016).

Using ashes in various areas and gaining them to the country's economy seem to be possible, if solutions to these problems are found. Due to their fine formation, pozzolan property and the one-dimensional spherical structure, the ashes are resistant to freezing and thawing and is preferred as building material. Therefore, construction industry mainly comes first among the sectors using the ashes. The ashes are used in the production of cement, concrete, aggregates, adobe, brick, gas concrete and insulation material; in the construction of dam and road, and in geotechnical applications. The production of cement is one of the areas most commonly used in the construction industry due to cost reduction, energy conservation, and environmentally friendly behaviour. The ashes are used as additive and substitute material in both normal and lightweight concrete as well as in ready-mixed concrete whose use is increasingly getting widespread in the production of pre-production and pre-stressed concrete elements, as a water trapping additive in concrete.

Concrete usage around the world is second only to water and Ordinary Portland Cement (OPC) is conventionally used as the primary binder to produce concrete. The environmental issues associated with the production of OPC are too many. The cement industry is held responsible for some of the CO2 emissions. The amount of the CO2 released during the manufacturing of OPC due to the calcination of limestone and combustion of fossil fuel is in the order of 1 ton for every ton of OPC produced (Motorwala et al., 2013).

OPC is by far the most commonly used binder in construction practices. For a long time, OPC concrete was considered to be very durable material requiring a little or no maintenance. Unfortunately, its resistance to chemical attacks such as acids and sulphates is of concern. In the case of acid attack on OPC concrete, calcium salts of the attacking acid rapidly form; and the concrete loses its strength and deteriorates quickly. Acid attack has not traditionally attracted much attention, even when cement composites are severely damaged by acids wherein calcium hydroxide is dissolved and the hydrated silicate and aluminium phases are decomposed (Thokchom et al., 2009).

The demand for OPC is increasing day by day; and hence, efforts are being made in the construction industry to address this by utilising supplementary materials and developing alternative binders in concrete. The application of geopolymer technology is one such alternative. The abundant availability of fly ash worldwide creates opportunity to utilise this by-product of burning coal, as a substitute for OPC to manufacture concrete. When used as a partial replacement of OPC, in the presence of water and in ambient temperature, fly ash reacts with the calcium hydroxide during the hydration process of OPC to form the calcium silicate hydrate (C- S-H) gel (Motorwala et al., 2013).

Green engineering construction material is a form of cementitious materials based on ash as source material; and it is an environmentally friendly choice against OPC releasing a large amount of greenhouse gas to the atmosphere during energy intensive manufacturing process. It exhibits many excellent properties such as high compressive strength, low creep, good acid resistance and low shrinkage.

Key Terms in this Chapter

Industrial Symbiosis: Is an association between two or more industrial facilities or companies in which the wastes or byproducts of one become the raw materials for another. Industrial symbiosis involves a collective approach to competitive advantage through the physical exchange of materials, energy, water, and/or byproducts, or the shared use of assets, logistics, and expertise.

Geopolymer: Is new materials for fire- and heat-resistant coatings and adhesives, medicinal applications, high-temperature ceramics. It is a type of inorganic polymer that can be formed at room temperature by using industrial waste or by-products as source materials to form a solid binder that looks like and performs a similar function to OPC. Geopolymer binder can be used in applications to fully or partially replace OPC with environmental and technical benefits, including an 80-90% reduction in CO 2 emissions and improved resistance to fire and aggressive chemicals.

Cement: Is a binder, a substance used in construction that sets, hardens, and adheres to other materials, binding them together. Cement, usually in powder form, acts as a binding agent when mixed with water and aggregates.

4 R: Reduce, reuse, recycle, and recover.

Reuse: Is the action or practice of using something again, whether for its original purpose (conventional reuse) or to fulfil a different function. Reduce, reuse, and recycle (R3) are the three essential components of environmentally responsible consumer behavior.

Bottom Ash: Is the coarse, granular, incombustible by-product of coal combustion. It is made from agglomerated ash particles that are too large to be carried in the flue gases and fall through open grates to an ash hopper at the bottom of the furnace or incinerator.

Ordinary Portland Cement (OPC): Is one of the most widely used type of Portland cement. The name Portland cement was given by Joseph Aspdin in 1824 due to its similarity in color and its quality when it hardens like Portland stone. Portland stone is white grey limestone in island of Portland, Dorset.

Fly Ash: Is a byproduct from burning pulverized coal in electric power generating plants. During combustion, mineral impurities in the coal (clay, feldspar, quartz, and shale) fuse in suspension and float out of the combustion chamber with the exhaust gases. As the fused material rises, it cools and solidifies into spherical glassy particles called fly ash.

Waste: Is any substance that is discarded after primary use, or it is worthless, defective, and of no use. It is unwanted material (discharged to, deposited in, or emitted to an environment in such amount or manner that causes a harmful change) left over from a production process, or output which has no marketable value.

Waste Management: Is all the activities and actions (the collection, transportation, and disposal of garbage, sewage, and other waste products) that are required to manage waste from its inception to its final disposal. It encompasses management of all processes and resources for proper handling of waste materials, from maintenance of waste transport trucks and dumping facilities to compliance with health codes and environmental regulations.

Environment: The sum of total of all surroundings of all living organisms, including natural forces and other living things, which provide conditions for development and growth as well as of danger and damage.

Concrete: Is a composite material composed of coarse aggregate bonded together with a fluid cement that hardens over time. Concrete is made up of three basic components: water, aggregate (rock, sand, or gravel), and Portland cement.

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