Introduction
Waste glass is of great concern in some developed countries, particularly in the urban areas. This is because of the amount of waste material generated from both municipal and construction sources, and the lack of waste disposal areas to receive the material. Countries like Japan, the United States of America, and Australia have taken the initiative to invest in the recycling of glass in order to mitigate the ever increasing amount of waste glass generated over the years.
1.1 History of glass
According to (Lee, Jr. 2007), glass can occur naturally as volcanic deposits and fulgurite. It is also be manufactured from silica sand (SiO2) and a mixture of other compounds. Glass containers manufacturing dates back over 3500 years and evolved around 50 AD by the Romans using the mouth-blowing technique to form complex shapes. During this time, the mouthblowing technique transformed multi-coloured transparent glass into many shapes and sizes, but resulted in small quantities which were mostly used as stained window panes in churches (Guardian Glass Time n.d.).
Europe was the first continent to benefit from the Italians advanced glass industry in the middle ages.
At present, over 1000 chemicals formulas are used in the glass manufacturing industry (Lee, Jr. 2007).
During the twentieth century, the modern era of glass brought forth magnificent skyscrapers redefining the skyline. In addition, glass cladding of buildings fulfils functional requirements of lighting, heat retention and energy saving. “The nature of glass – its visual appeal, interplay with light, a sense of openness and harmonious integration with the environment, facilitates interesting and creative uses both in the interiors and exteriors of any building” (Property Bytes 2013).
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1. Asahi Glass Company has diversified through internal growth, acquisition, and joint ventures from its origin in flat glass to broad glass-materials, chemical, and electronics manufacturer. It has also vertically integrated and expanded internally to become the leading global glass manufacturer. In 1993, Asahi Glass is reviewing its future direction, particularly whether it should divest its ...
1.2 Uses of glass in the construction industry
The use of glass in the construction industry has increased over a number of years and recently has been incorporated into the structural elements of load bearing components to increase lighting and to enhance appearance of the structures. Not all glass components used in the construction industry are structurally loaded, and they can be found in non-structural lightweight concrete, paints, partitions and waste water filtration devices just to name a few. Glass can be found in both translucent and transparent forms, and is perceived as being superior and more economical and sustainable than that of cement, concrete and steel.
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1.2.1
Glass beams
Complex glass structures exist in the modern world. One such structure is the glass beam which had limited span length but can be joined to lengthen its span to at least 2-3 times the original. For example, the Yuraku-cho station in Tokyo has a 10.6m cantilever glass canopy at the entrance of the station, which consists of four individual beams pinned together to form an arch shown in Figures 1 and 2. (Leitch 2005).
Figure 1 Yuraku-cho underground station in Tokyo, Japan (source: www.rvapc.com)
1.2.2
Glass columns
Glass columns is yet another interesting structural component that architect and engineers managed to use in places where clients do not like to see columns because of their visual obstructions. These columns made from glass create an interesting visual feature that is appealing to the eyes and give the appearance of an uninterrupted open space. Design strength of these columns is carefully done but designers also over-design the structures that are being supported by the glass column in order to prevent collapse in the event the column fails. Although glass is strong in compression, there is still a fear of brittle failure, hence the overdesign of the structures being supported. In addition, load distribution of the applied load must be carefully uniformly distributed to prevent the development of concentrated stress that can trigger a brittle failure.
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Figure 2 Columns of glass in Russia (Source: http://www.mos-steklo.ru)
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1.2.3
Glass walls
The use of glass walls has become more popular in modern times. They enhance the appearance of a building and allow a connection to the adjacent environment whether from a top floor of a skyscraper enjoying the scenery or from a few millimetres away from sea-life in an aquarium or zoo. Therefore, these transparent glass walls serve as a connection to the outside environment and they also protect us from elements and dangers outside of the building envelope.
Design considerations must be given to the thickness of these walls and load transfer, and must also be comprised of multiple layers to minimise the risk of concentrated stresses which can cause a collapse from a fracture. Safety standards must be adhered to at all cost to ensure the walls protect the occupants for a period of time even after a failure.
Figure 3 Glass walls structural members and partitions (Source: www.accentbuildingproducts.com)
1.2.4
Glass roofs
Glass roofs were always a fascination to watch. They are built in all shapes and sizes to support the need of the occupiers, whether it is for architectural or conventional horticultural purposes. Regardless of its intended use, several benefits and drawbacks will have to be considered such as, light penetration and thermal properties, in addition to the structural specifications that must be followed. If ignored, the occupants of these structures can experience undesirable discomfort due to intense thermal gain. On the other hand, this can be regulated with the use of modern polyvinyl butyral (PVB) technology and glass tint, to reduce the thermal gain and create favourable conditions.
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Source: www. www.law.umich.edu
Source: www.inhabitat.com Figure 4 Glass roofs in India
1.2.5
Glass floors
Consideration for installation of glass floors are dependant on their intended use and locations. These are mostly in use as pedestrian foot bridges, as designers try to prevent surface scratches which can increase the potential for failure due to increase tensile forces. Nonetheless, they are a great architectural façade, and designers take great care calculating the degree of robustness to withstand the expected traffic and abuse, and meeting all required specifications.
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Figure 5 The Grand Canyon Skywalk (Source: http://www.highestbridges.com)
Figure 6 Glass Bridge in Calgary Eaton Centre, Canada (Source: http://www.halcrow.com)
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2
Objectives
The objective of this study is to identify and analyze potential applications of using recycled waste glass as construction materials (Mwasha 2013).
This study will look at the following: The Life Cycle Analysis (LCA) of waste glass The properties of glass and suitable applications The benefits and effects of glass recycling Investigate the use of recycled waste glass as construction materials Investigate their advantages and disadvantages
3
Methodology
This study is conducted by reviewing existing literature extracted from books, scientific articles, internet databases, journals and reports of studies that were done on the properties, benefits, economic and environmental factors, life cycle analysis and potential applications of solid waste recycled glass. The literature will then be used to identify suitable applications and make recommendations for the use of recycled glass in the construction industry.
3.1 Limitations
This research is limited to data collected and published on countries outside of the Caribbean. The lack of information and practical application within the region is limited and therefore do not produce a good representation of the Caribbean.
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Literature review
4.1 Properties of glass
Most of today’s glass production is float glass, with thicknesses usually
ranging from 2 – 25 mm and a standard size of 3.21 x 6 m that is used for further processing. The glass has the following physical properties (Lee, Jr. 2007).
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Engineering Properties of 100-percent Cullet from Two Recycling Sources Property Value 2.48 to 2.49 Specific gravity Gs 72 to 79 lb/ft3 (minimum) Relative density 109-118 lb/ft3 (maximum) Durability LA abrasion averaged 24.5 percent Sodium sulfate soundness averaged 6.7 percent Modified Proctor maximum dry density averaged Compaction 114 lb/ft3 Standard Proctor maximum dry density averaged-106 lb/ft3 Permeability 0.00014 0.00066 cm/sec Shear strength Effective friction angle average from triaxial testing was Leaching TCLP and 47.5 deg SPLP tests showed the samples were nonhazardous Table 1 Source: (Lee, Jr. 2007) 4.1.1 Specific gravity
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The specific gravity of crushed rock and natural sand aggregates usually range between 2.60 and 2.83 (Nebraska State Recycling Association 1997).
On the hand, the specific gravity of glass cullet is significantly lower than that of crushed rock and will affect the relative density and compaction unit weight of cullet (Table 1).
The comparison between performance and compaction density will be seen as a negative attribute. (Lee, Jr. 2007) 4.1.2 Durability
Depending on the type of rock aggregate in question when compared to glass cullet, it was revealed that during the LA abrasion tests, cullet suffered more losses (at least twice as much) than the natural aggregate from crushed rock (Lee, Jr. 2007).
In contrast, (Mayer, Egosi and Andela 2001) asserted that when glass is used in concrete, it provides an abrasion resistance that only a few natural stone aggregates and expensive special floor toppings can achieve. 4.1.3 Workability
The ease with which a material is handled and compacted defines the workability of that material. According to (Nebraska State Recycling Association 1997), cullet and cullet-aggregate mixtures provides favourable workability characteristics. 4.1.4 Density
The density of glass is 2500kg/m3, and will have an effect on durability and compaction factors in concrete mixes (Nebraska State Recycling Association 1997).
4.1.5 Aesthetics
Glass can produce value-added products and can be very attractive when Artists, Architects and Designers work their artistic abilities to achieve such a product. Evidence of this can be found in 6|Page
many glass products constructed around the world. One such location is the Itabashi City in Tokyo, Japan, which took the global recycling movement by storm, and engaged in the glass recycling programme with great success (Japan Local Government Centre 2009).
The city utilized the tiny pieces of crushed waste glass (less than 1mm) to practical use as raw material for architecture, paints and coatings, where the distinctive colours are still visible in the final product. Some of these effects can be seen in the pavements, wall coatings and bollards, to name a few (Japan Local Government Centre 2009).
The Essay on Recycling 7
recycling, the process of recovering and reusing waste productsfrom household use, manufacturing, agriculture, and businessand thereby reducing their burden on the environment. During World War I and World War II, shortages of essential materials led to collection drives for silk, rubber, and other commodities. In recent years the environmental benefits of recycling have become a major component ...
Other architectural and decorative applications such as precast wall panels, park benches, planters, floor tiles and trash receptacles are potential products of recycled waste glass (Mayer, Egosi and Andela 2001).
4.1.6 Compaction
Compaction is an important design consideration in construction and engineering, given that most in-situ materials need some form of compaction to gain the required specifications for the application. The application of glass cullet as a substitute for conventional aggregates can be handled spread and compacted with traditional construction equipment in backfills, roadway base course, sub-base or embankments and utility trench beddings (Lee, Jr. 2007).
Various laboratory compaction tests can be used but this is guided by the compaction method to be used in the field. One of these tests is the modified Proctor compaction method.
This test was used in (Lee, Jr. 2007), and indicated that density marginally increases with decreasing cullet content in cullet-added mixes. An advantage of utilising cullet is its insensitivity to moisture content which allows it to be placed and compacted in adverse weather conditions (wet weather), reducing or preventing delays on construction projects (Nebraska State Recycling Association 1997).
4.1.7 Permeability
In civil engineering works such as foundation drainage, permeability is an important design consideration. Sand or washed gravel are the more traditional granular materials used in drainage applications with ranges from 0.01 to 0.001 cm/sec, but glass cullet can also be utilised with a permeability range from 0.04 to 0.06 cm/sec for fine cullet and 0.18 to 0.26 cm/sec for coarse cullet. The ranges above are in contrast with Table 1 compaction data, which illustrates a range from 0.00014 – 0.00066 cm/sec for 100% glass cullet. Other uses of cullet are filtration medium in swimming pools, septic fields and water purification applications. However, (Nebraska State Recycling Association 1997) indicated that a further study of the filtration capacity is needed. 7|Page
4.1.8
Filtration
When designing drainage systems, filtration is one of the most important factors to be considered to prevent blockages, plugging and clogging. Traditional methods used are by means of geotextiles but glass cullet also has its place in this application. Cullet can also be used as a composite material with thick non-woven geo-textiles to offer a drainage solution preventing the movement of soil particles from water flow. 4.1.9 Emissivity
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Emissivity measures the ability of a surface to reflect absorbed heat as radiation. It is defined as the fraction of energy being emitted relative to that emitted by a thermally black surface (a black body).
According to (Guardian Glass Time n.d.), the normal emissivity factor for glass is 0.89, which indicates that of all the heat absorbed, 89% is reradiated. The reflectivity of glass varies with wavelength because glass is transparent at short wavelengths, and is opaque at long wavelengths (4.8 microns).
Thin glass has a low emissivity value at short wavelengths but has a high emissivity value at long wavelengths. This property was particularly useful in the construction of the glass pavements in Tokyo, Japan, where the reflective properties of glass, along with its water retentive properties, has proven to have a greater effect in temperature reduction than other previously used materials such as asphalt (Japan Local Government Centre 2009).
4.1.10 Shear strength
Shear strength is a major design consideration for construction with glass cullet in embankments, roadway base courses, and engineering fill under foundations (Nebraska State Recycling Association 1997).
This factor is measured by a number of tests for granular materials such as, the direct shear test, the triaxial shear test, the California Bearing Ratio (CBR) test, the Resistance R-value test, and/or the resilient modulus test, depending on the engineering application.
For roadway and airfield design and construction, the CBR, R-value, and resilient modulus tests are the most appropriate methods of testing. According to (Guardian Glass Time n.d.), these tests are carried out to measure specific parameters depending on the intended application and the quantity of cullet present. Although it was determined that cullet strength and natural aggregate strengths are similar, it is recommended that only 30% of cullet is used in load bearing fluctuating fills (Nebraska State Recycling Association 1997).
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4.1.11 Thermal properties
As indicated by the (Guardian Glass Time n.d.), an extremely important factor for glass is its thermal properties. For example, thermal variations such as increase in temperature can have a significant impact for joining to other materials. In addition, it must also be noted that resistance to temperature differences along glass panes has a tolerance of 40 K (Kelvin).
Higher temperatures than 40 K can cause dangerous stresses and can result in breakage. Therefore it is recommended that direct heat should be kept approximately 30 cm away from the glass or one of pane safety glass should be installed in addition (Guardian Glass Time n.d.).
(Nebraska State Recycling Association 1997) asserted that because cullet conducts heat more slowly, it allows cullet materials for use as utility trench backfill. 4.1.12 Compressive strength
According to (Guardian Glass Time n.d.), glass is extremely resilient to pressure which is indicated by its 700-900 MPa. In addition, flat glass can withstand 10 times higher compressive power with the maximum compressive load.
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Life cycle analysis
Life-Cycle Assessment (LCA), also called Life-Cycle Analysis is a tool for examining the total environmental impact of a product through every step of its life. This process begins with the extraction of raw materials, transportation, manufacturing in the factory, selling, the use of the product, and disposal or recycling of the product (Bishop 2004).
The LCA of glass has evolved since the recycling of solid waste materials began. Instead of the extraction of virgin material from their natural source such as quarries, many countries are now recycling from existing solid waste materials. Glass has been piling up in the local landfills over time and placed them under tremendous pressure for space, Figure 7 Recycling process of waste glass Source: (Glass for Europe n.d.)
due to their very slow rate of degradation. Since the waste
glass recycling campaign started, instead of disposing of the post- consumer glass, this material is reprocessed to produce new household and construction products.
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During each step of LCA, CO2 emissions are calculated, and the environmental impacts evaluated, as substitute materials replace virgin raw materials. At each stage of the life cycle, all sources of CO2 are considered from cradle to cradle including quarrying, raw material preparation transport, product manufacture, recycled glass collection and recycled glass processing and reuse (Enviros Consulting Ltd for British Glass 2003).
The LCA of glass can be a closed looped process where glass can be reprocessed for an infinite number of times and retain its 100% quality, or open loop where glass can only be processed a single time.
The LCA of glass begins with the quarrying or extraction of raw material. This task has a negative impact on the environment, as natural resources are being depleted and expenses accumulating while excavation equipment is discharging carbon dioxide (CO2) into the atmosphere. CO2 continues to be discharged during transportation of extracted material to the processing plant. At this stage, the raw materials (soda lime glass, silica sand, soda and magnesium) are properly weighted and mixed and then introduced into a furnace where they are melted at 1600° C. This is where energy consumption is at a high level and so is pollution.
In figure 9, the molten glass then flows from the glass furnace onto a bath of molten tin in a continuous ribbon. The glass, which is highly viscous, and the tin, which is very fluid, does not mix so that the contact surface between these two materials is perfectly flat. When leaving the bath of molten tin, the glass has cooled down sufficiently to pass Figure 8 showing the LCA of floating glass Source: www.glassforeurope.com
through an annealing chamber called a lehr. Under After the product has been produced, transportation cost and CO2 emissions continue to accumulate as the product
controlled temperatures, it is cooled until it reaches room temperature.
Figure 9 Showing production of glass Source: http://www.glassonweb.com
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is transported to the wholesalers and retailers for distribution to the customers for use. Subsequently, the waste product is discarded to be disposed of, recycled or reused. Discarded waste products to be recycled are collected or transported (CO2 pollution generated via transportation) to the recycling plant for sorting as the first stage of the recycling process. Most plants have an automated sorting system but additional labour is required to remove residual contaminants (plastic, wood, metal, paper, etc.) from the waste glass before crushing begins. The sorted glass is then crushed into cullet in preparation for melting. Not all glass may be melted as some cullet may be sold to used Figure 11: Glass cullet in various colours
construction as a
Figure 10 Life Cycle of Glass Source: (Gabbert Cullet n.d.)
companies to be
Source: www.1800recycle.wa.gov
substitute or mixed with conventional construction aggregates. The remaining cullet is placed into the furnace and heated to 900 degrees Celsius where it is melted and shaped to produce the new product. This heating process consumes a lot of heat energy, but less than that of melting virgin material, that produces more CO2 emissions. The product is then transported to the wholesalers and retailers for distribution to the consumers for use, and CO2 savings kg/t glass 314 290 275 66 19 -2 -43 0
subsequently disposed for recycling or landfill depending on if it was a closed looped or open looped recycling process. See tables 2 & 3 below for figures showing the CO2 savings kg/t of glass in the U.K. via various recycling methods and producing new products (Enviros Consulting Ltd for British Glass 2003).
Recycle closed loop Recycle open loop
UK Export Glass fibre Bricks Shot blast Aggregates Filtration
Landfill disposal
Table 2 A comparison of CO2 savings options for recycling of waste glass Source: (Enviros Consulting Ltd for British Glass 2003)
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Table 3 CO2 Savings Resulting from Glass Recycling Source: (Enviros Consulting Ltd for British Glass 2003)
6
Discussion
6.1 Economic factors
In addition to some U.S. states offering cash for most glass bottles, a number of glass recycling plants in the U.S. and the U.K. that use automated sorting systems also rely heavily on workers to eliminate any contaminants left behind. This is the livelihood for some people, while in some areas, glass recycling is a means to earn extra income (West n.d.).
In addition, collection, sorting and reprocessing of recyclables, creates more jobs than incineration and landfill deposits. Another example of key economic factor is the recycling of glass and other solid waste materials reduces the amount of waste being deposited at the landfills. According to (West n.d.), glass can take up to a million years to break down but it takes as little as 30 days for a recycled glass bottle to leave your kitchen recycling bin and appear on a store shelf as a new glass container.
This can have serious land-area implications at landfills and can lead to high economic cost to locate and prepare an alternate site to receive waste material. Instead of incurring environmental levies and high landfill costs, the recycling of glass material can generate revenue from sales, and also reduce landfill expenses. Despite a cost attached for the collection of material to be recycled, the materials generate revenue upon completion of the recycling process and sales. This revenue can be reinvested into the waste collection budget.
In addition to the U.S and the U.K, other countries such as Australia and Japan have already began to utilise waste glass in in many applications such as pavements, road construction, coatings and filtration media, to name a few. The availability and properties of glass plays a major role in their use as a recycled material. For example, it is less expensive to recycle glass from local sources in order to reduce the transportation cost and maximise the loads being 12 | P a g e delivered to the processing plants. It is more energy and cost efficient to process glass at the maximum capacity of the plant because it takes the same amount or energy to process full or half loads of material.
6.2 Health and Environmental factors
Glass bottle recycling should be the concern of all inhabitants of the world as pollution affects us all in some form. Recycling mitigates the need for virgin materials and hence the impact on the environment and global habitat loss. There is a heavy impact on the environment due to the carbon footprint from the extraction of raw materials to the production of glass products.
The two classifications of carbon footprints are categorized as primary and secondary, where the primary footprint is the amount of greenhouse gases released into the environment from various sources (automobiles, airplanes, etc.), and the secondary footprint which is the amount of greenhouse gas emitted from the life cycle of products.
The reduction of energy consumption through recycling techniques continues to use energy, but reduces the overall emissions generally produced when manufacturing from virgin materials. This is evident according to table 3 (Enviros Consulting Ltd for British Glass 2003).
Glass dust is not considered hazardous but can be a skin and eyes irritant. As a precaution it is recommended to supply moist material and hose down stockpiles, and encourage workers to always wear protective gear when in its environs.
6.3 Sustainability
In terms of availability and capacity, glass is one of the most economical materials to recycle in some countries such as the U.S, Japan, Australia and the U.K. It is not limited to a particular class of people, as every householder can participate in this recycling initiative to help us toward our quest of sustainable living by reducing their impact on the environment. Countries have made provisions such as collection points and centres for recycled glass, to encourage the population to be on-board with this mammoth task.
Participation encourages a green consciousness in our minds and promotes the development of sustainability among the population. Glass can be infinitely recycled with no loss of purity or quality, with a reduction of energy consumed (West n.d.).
The LCA of glass provides the data to support this notion, and has proven that alternative uses of waste can be adopted in the form of aggregates, fill materials, coatings and filtration media. Based on the properties of glass, testing methods and standards,
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glass can be used as a substitute material in order to reduce the environmental impact caused by depleting our natural resources and CO2 emissions.
6.4 Energy consumption
Producing new glass from virgin materials consumes a significant amount of energy and generates pollution in the form of CO2. This is due to the extraction of raw materials, transportation to the processing plant, heating to approximately 1600 degrees Celsius in a furnace to produce the product, and transportation to the distributors.
Although the recycling of waste glass also includes a transportation element, energy may be saved and pollution reduced depending on the proximity of the collection site to the processing plant and distribution centres. Another energy saving component is the melting of the cullet. Cullet consumes approximately 40% less energy than making new glass from virgin materials, because cullet melts at a much lower temperature of 900 degrees Celsius (West n.d.).
6.5 Applications in construction
“Glass cullet may be pulverised into a sand-like product, for which there are limited applications as non-structural concrete aggregate, fill material and for drainage” (Department of Sustainability, Environment, Water, Population and Communities 2012).
According to the (Department of Sustainability, Environment, Water, Population and Communities 2012), approximately 75,000 tonnes and 60,000 tonnes of glass fines are currently in New South Wales and Sydney respectively, that are destined for the landfill. It is envisioned that if that glass is utilized in concrete as a natural sand replacement, it could save them up to $2.5 million. Waverley Council has already begun to utilize the glass cullet in two 100m sections of pavement by substituting 15 tonnes of cullet into asphalt and concrete (Department of Sustainability, Environment, Water, Population and Communities 2012).
Backfill material The use of cullet as a drainage backfill material is becoming a widely used application in place of the more conventional washed stone/gravel as fill material.
Cullet conducts heat at a slow rate which makes it a viable option for use as backfill in trenches with utility pipes such as gas lines that heat could be detrimental to the stability of the pipe, and adversely affect its operation. This material must meet the requirements for its specified use as part of the design considerations such as compaction, permeability, thermal conductivity and filtration. 100% glass cullet fill can 14 | P a g e
be used to at least 2 feet below finish grade of the trench, and the remainder may vary from 15% to 100% cullet (Nebraska State Recycling Association 1997).
In addition, cullet can also be used as general construction backfill in foundations, beneath fluctuating loads, reciprocating pumps, and as fill beneath pedestrian sidewalks. Design considerations for these applications include gradation, shear strength and leachability. Source: www.ceramicindustry.com
Aggregate in Concrete For cullet to be used as aggregate in concrete, a number of properties must be taken into the design considerations. Compressive strength, thermal properties, shear strength, density, durability, workability, specific gravity and compaction are the main consideration to be addressed for the cullet to be favourably considered for use in concrete applications. Concrete with cullet aggregate can be used in sidewalk construction projects. Source: www.heringinternational.com
Roadway Construction Conventional granular materials are subjected to shear strength, R-value, abrasion, resilience modulus and filtration standards to be considered for use as sub-base and base course material in road construction. There is a potential to use glass as a base course, sub-base, sub-grade or embankment applications when mixed with natural aggregate, and will likely be able to withstand abrasion and traffic loads. However, in addition to the above criteria, gradation standards will also have to be met. Source: www.blog.selector.com
Landscaping Glass used for landscaping is used as aesthetics but some physical characteristics also matter in the application. Crushed glass used in this manner must meet another requirement to enable it to
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be used safely. After crushing, the glass must be sized and tumbled (to soften the sharp edges) to minimize the potential threat to human health. Sandblast Media Natural sand is normally used in this application to free surfaces from corrosion, fungus and paint to name a few, using high pressure pumps.
This application requires an abrasive material such as sand, to function effectively and efficiently. Glass can be crushed, sized and dried to meet the expected requirements but a specific uniform size may also be required for use in this particular application along with additional specifications. In this application, it is absolutely necessary for workers to use protective gear in order to minimise potential health risks. Source: www.flickr.com
Glass Sand Cullet can be ground into fine particles that can be used to replace the conventional natural sand in some applications. New Zealand has often use glass sand on golf courses in sand traps, and for beach sand (Solid and Hazardous Waste Education Center 2012).
In this case there is no need to consider some glass properties such as workability, compaction, and shear strength, to name a few, because there are no strength considerations in this application. However, for use as beach sand, tumbling of the glass is a necessary requirement as this softens the sharp edges on the pieces of glass to reduce any health hazards.
Water and Wastewater Filter Media Conventional materials such as granular aggregates are normally used in Water and wastewater treatment systems as part of the of filter systems. Glass can be used as a substitute or as a composite material with sand to provide an effective filter system for waste water treatment. Applications should be considered only when glass properties such as permeability and filtration standards are met to reduce the possibility of clogging and plugging. Source: www.ukpoolstore.co.uk
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6.6 Advantages and limitations
The use of recycled class in the construction industry reduces the burden on some natural resources that are being depleted by excessive quarrying. With the properties of glass considered, there are many possibilities and advantages of using glass in the construction industry. It offers a wide range of energy-efficiency possibilities such as optimising light transmission, regulating heat entry into the building with its thermal conductivity properties, hence providing cost savings in temperature regulating devices within the building envelope. Glass serves as an excellent thermal insulator whether by itself or as a composite material. The emissivity of glass also has its advantages. For example, the streets of the Yotsumata shopping district in Tokyo, Japan are made from wine block slabs and other glass products. This initiative managed to reduce the temperature in the city because of the adoption of the highly reflective pavement installed (Japan Local Government Centre 2009).
A number of other advantages are listed below.
Architect’s use of glass in designing adds beautification of the facade of a building. Kitchens and bathrooms can be furnished with glazed counters or shower cubicles that are easy to clean and give a very modern and hygienic look to the space. Its use fulfils the architectural view for interiors and exteriors of buildings. By using glass in interior, it maximises the space inside the building. Glass cladding in building fulfils functional requirement of lighting, heat retention and energy saving through unique thermal properties. Its use conveys a sense of openness and harmonious. As toughened glass is available, one can have good interior design with the use of glass in transparent staircases, coloured shelves, ceiling and other fascinating designs.
Glass is an excellent material for thermal insulation, water proofing and energy conservation. For making glass partition on upper floors, no extra design is required for slab as glass is light in weight. The glass has sufficient properties to perform the function of the aggregate it replaces. Glass is a diverse material that can be used in various applications, not limited to the construction industry alone. 17 | P a g e
Listed below are some disadvantages of using glass in construction. Glass can get very costly and increase the budgeted cost of construction work. It can force the designer to over-design the structure supported by glass columns and beams to be able to stand on their own. This can also lead to an increase in construction cost. Glass erected as walls can increase the cost of security as it may not be as secured as a concrete wall and may attract prowlers. In this case, an adequate security system may have to be considered.
Maintenance cost can be very high as glass is expensive and installers would account for that in their installation fees. Maintenance in terms of cleaning will be more frequent if it is to remain attractive. Glass is also unsafe for earthquake prone areas. Glass may not be used where it will be exposed and may pose a safety threat. The use of glass in application oriented. For example, glass has properties that may not be suitable for specific applications, therefore, the designer must ensure that they are aware of such information.
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Conclusion and Recommendations
Glass always had its place in the construction industry. It stems back from over 5000 years ago and has since been evolving. In this modern era, glass has been used in various applications from structural to non-structural. Several countries have already engaged designing and building sophisticated glass structures such as the Yuraku-cho underground station in Tokyo, Japan (Figure 1), and the Grand Canyon skywalk in the U.S.A (Figure 6).
The properties of glass were identified, and this gave rise to the advantages and limitations of using waste glass in various applications in the construction industry. Some key properties were emissivity, durability, compaction and aesthetics. These properties proved to have some suitability in specific applications based on specific tests and standards, however they were limitations to how much, what size and what methods should be used for the application to be successful.
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The LCA of glass also supports a sustainable product from the view that glass can be recycled an infinite number of times, and remain pure. Recycled glass is more energy efficient and less pollution intensive than extracting from virgin material. It promotes jobs in this economic climate, encourages all citizens to participate in the “greening” initiative, and reduces the amount of waste material going to the landfill for disposal. Today the glass used in modern architecture is suitably processed to make it safe and secure. This is done by making the glass either tempered or laminated. By processing the glass in this fashion, its ability to survive impacts is enhanced. Glass today gives several benefits as mentioned above. We have to recognize these benefits and give them their due importance. Glass does a wonderful job of protecting us from the environment – provided it is used properly. Glass is irreplaceable as an element of architecture, which imparts to a building.
It has many desirable characteristics like safety, aesthetics, and solar control, ease of maintenance, sustainability and so forth. Technologies in glass designs hold a great future for more delightful yet enthralling architectural designs. As futuristic designs might emerge it opens doors for us to live in a world made of glass. (Property Pulse 2011) It is recommended that more countries invest in glass recycling as it can provide some economic gains, reduce pollution and build toward a greener environment. In addition, more studies should be done to further explore the limitations of glass and to improve upon the existing advantages. More standards and continued improvements of glass in applications should be pursued to widen the scope of glass recycling worldwide. Lessons learned from existing studies and past experiences should be shared with countries getting on-board in the recycling initiative, so as to fast-track the process of sustainability. Government should implement policies regulating solid waste recycling for future improvements in our dying environment.
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References
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Civil and Environmental Engineering, Massachusetts Institute of Technology, 2005. Mayer, C, N Egosi, and C Andela. Concrete with Waste Glass as Aggregate. Columbia University, RRT Design and Construction, Andela Products Ltd, 2001. Nebraska State Recycling Association. Glass Cullet Utilization Study. Civil Engineering Applications, HDR Engineering Ltd., 1997. Property Bytes. Glass in Construction. 2013. http://propertybytes.indiaproperty.com/ (accessed July 18, 2013).
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U.S. Department of Transportation. The Use of Recycled Materials in Highway Construction. 1994. http://www.fhwa.dot.gov (accessed July 18, 2013).
United States Environmental Protection Agency. Markets for Recovered Glass. United States Environmental Protection Agency, 1992. West, Larry. Benefits of Glass Recycling: Why Recycle Glass? n.d. http://environment.about.com (accessed July 18, 2013).
www.int49project.wikispaces.com. n.d. www.int49project.wikispaces.com.
