Introduction
A permanent concern of man has been his habitat. He has always looked for ways to protect himself from the elements, the aggressions of the outside environment, and the intrusion but without remaining in isolation or darkness. Man has tried to combine his safety and protection with the utility of light and observation of the outside. As result, it arises the most important application of glass in construction. With its contradictory functions, glass separates and unites at the same time; it is inert and its effects are changing; it gives light, harmony, and resistance; it is transparent and facilitates the great expansion of architecture as art and construction technique. The discovery of glass dates back to 3000 to 2000 BC. It is believed it was found by accident in Egypt and Mesopotamia and used mainly in decorations, jewelry and liquid containers. Considering its manufacturing process have evolved from craftsmanship to today’s industrial making, the number of glass types and applications in construction have multiplied. Its chemical, physical and optical contributions to construction make it convenient for building industries. Glass might be used in a design for structural, enclosure, mechanical and aesthetic purposes. It is a fully recyclable material which brings different benefits for the environment and also in people’s lives. The purpose of this paper is to go more in depth about glass history, manufacture process, construction uses, sustainability and reinforce the information with a case study.
History
It cannot be assured who discovered the glass. Studies, videos, and articles attribute the discovery of glass to the Phoenicians and others to the Egyptians. Some publications, tell a common story about glass’s beginnings. Historians said that the birth of this transparent material occurred when Phoenician merchants of natron prepared their food. Not finding stones to place their pots on the fire, they took part of the natron that they carried. After eating, they fell asleep and left the fire burning. When they awoke, instead of the natron blocks, they found transparent and luminous solids like precious stones. Although nobody is completely sure of its origin, Alan Macfarlane and Gerry Martin provide a more complete study of the history of glass in their article "Glass: A Word History”. The authors state that “some estimate the origins of glass at between 3000 and 2000 BC, while other suggest hints of glazing on pottery as early as 8000 BC. As to how, all is complete guesswork and we can only say that it was originally made by accident.” (Macfarlane and Martin pg 10). For this statement, the story mentioned about the Phoenicians might not be a poor theory. After all, the oldest pieces of glass date from about 5,000 years BC. They have been found in areas of Asia, Mesopotamia and Ancient Egypt.
As Ancient Egypt became part of the Roman Empire, they were propagating the glass industry, Macfarlane and Martin say glass was used for three purposes: to glaze pottery, for jewellery and to make small containers, mainly for liquids (12). With the fall of the Roman Empire in the fifth century, this industry moved to the East. The method of making glass using the mouth-blowing technique, developed in Syria between the first and second centuries BC. The blowing technique was a great revolution in the technique and craftsmanship of glass and also in the history of construction. This event allowed the manufacture of larger sheets of glass, which facilitated the glazing of larger windows and more economically in buildings. Another advantage that involved the blowing of glass was a substantial improvement in its quality, since to be worked by this technique, it requires considerably higher temperatures than those required by the work of glass casting.
In Venice, the manufacture of glass was born in the tenth century and reached its maximum splendor in the fourteenth century. The use of stained glass as the closing of the windows of the churches had a special appeal for Christianity during the Middle Ages, given the multiple decorative, symbolic, didactic and propaganda possibilities offered, hence, its rapid dissemination. The symbolism of light and the search for effects of light and color inside Christian temples were a constant during the Middle Ages, since light was associated with God.
In another article called “Glass as matter: A brief history of manufacturing and application”, the author Anne Beim, explains that glass was a very expensive material to produce due to the vast amount of fuel (wood) required for firing the ovens. As such, the precious material was only affordable to a wealthy clientele, primarily the churches and nobility (Beim, 30).
The northern states did not remain indifferent to this new industry so rich. Glass making became cheaper as fuel was exchange for coal to fire ovens and there was a higher level of technological advancement. According to “A brief history of manufacturing and application”, it was not until the middle of the 19th Century, when the heavy tax laws on glass and windows were repealed in countries like England and Belgium, that window glass became more widely used in common buildings (Beim 30). The potential for manufacturing moved quickly through the industrialization era.
In the 19th Century, there was a higher demand of its product and new techniques permitted the creation of different styles and properties of glass. Innovations were introduced for newer commercial, scientific, and building applications. The importance of this material is confirmed by its numerous demand, under different forms and compositions. Glass has gone from being an interesting product, to being indispensable to satisfy the multiple needs of modern life.
Manufacturing of Glass
According to the International Association for Bridge and Structural Engineering (IABSE), the float process is the most popular primary manufacturing process and accounts for about 90% of today’s flat glass production worldwide. (IABSE pg 2). The raw materials for the modern production of a large variety of glasses employs a mixture of naturally occurring and locally sourced materials mainly limestone and sand. The major components of glass based on their percentages are as follow:
Silica (SiO2), vitrifying material 69 to 74 %
Sodium oxide/soda (Na2O), flux 12 to 16%
Calcium oxide/ lime (CaO), stabilizer 5 to 12%
Magnesium oxide/magnesia (MgO) 0 to 6%
Aluminum oxide/alumina (Al2O3) 0 to 3%
These ingredients are melted at a temperature between 1400 and 1500 °C in a furnace to obtain liquid crystal. The high temperature keeps it warm and fluid. Glass, then, floats on molten tin at approximately 1000 ° C. In this tank, it is cooled and solidified; a process called float bath. The flow of molten glass varies depending on the desired thickness of the final sheet. Furthermore, in an annealing lehr, the glass is cool slowly so it does not crack. Glass obtained can be further processed to obtain properties such as higher resistance and mechanic strength. Finally, a cutter cuts the crystal in the desired shapes and sizes. It is then packed, and transported to its destination. The fabrication of glass is a continuous process that does not stop. Manufacturers keep up with an schedule of 24/7 during the whole year.
Construction Uses
The glass-construction symbiosis is already consolidated, but it is in recent years, when this material is fully integrated into the construction industry. From being an aesthetic element, or a transparent separation material, to a multifunctional material, glass perfectly combines its transparency to light with selective actions against other radiations, with the isolation of noise, heat, fire, resistance to impact or burglary, with its behavior as a structural element, with the contribution of new optical, electrical, chemical properties. Glass as a building material and a series of properties that make it particularly interesting in the manufacture of decorative elements, the possibility of reading and writing in the same name, transparency in the passage of light and the resistance, The manufacture of windows, tables, cabinets, glasses, bottles, vases and infinity of ornamental pieces. In particular, colored glass is the most suitable for purely decorative applications, since the different shades combined with the light, create beautiful effects and also provide sensations of incomparable beauty.
Glass is a common material, used to make all kinds of enclosures. Some of them include balconies, laundry, windows, doors, closet, etc. In the case of using glass enclosures, the placement of the same can be carried out regardless of the masonry work. This is because the enclosures are usually placed on openings and are kept hidden under the new structure. The finishing process this type of enclosures has been going on for a long time of its placement. Any damage, or stain that results from the placement, can be removed only with the help of an anti-grease cleaner, leaving the surface as new. The type of glass that is used for these enclosures also guarantees their durability. People do not have to worry about replacing them quickly. The structure that contains the glass enclosures and weather strips, prevents the infiltration of water, wind and external dust. This helps keep the environment isolated and preserved from dirt and pollution.
Structural glass is a material with perfectly known properties that can be used, not only as a secondary element, but it can be made all kinds of structural elements such as beams, walls, slabs, etc. Probably the nonexistence of a reference regulation has slowed down a more widespread use of it. There are, however, publications of extraordinary quality such as the Structural Use of Glass document, published by the International Association for Bridge and Structural Engineering (IABSE), in which the properties and methods of calculating glass as a structural material are described. Recently the drafting of a new structural glass Eurocode has been approved, which was approved in 2012.
The laminated glass is formed by two sheets of simple annealed glass that are joined to one another by interposing a plastic adhesive sheet. Laminated glass is not designed to achieve greater mechanical strengths, since the thickness of the laminate is usually considered inferior to that of the glass formed by a single sheet. The laminated glass does not admit perforations for its fixation, because the concentration of efforts would break it with total security. It is convenient to protect the edges of the laminated glass to prevent the aging and its adhesives by direct exposure to the outside.
Tempered glass presents a remarkable increase of the mechanical resistance, a greater resistance to the thermal shock and offers a greater security to the use. Tempered glass is gradually heated to a softening temperature of between 575 and 635 °C and then cooled very quickly with air. In this way it is achieved that the glass is exposed on its surface to compressive stresses and inside to tensile stresses, giving it greater structural strength and impact than untreated glass, having the additional advantage that in case of breakage it is It fragments into harmless little pieces (which is why it is considered one of the types of safety glass). All manufactures, whether size cuts, edgings or drills should be made before tempering, if done later, would cause the glass to break.
Sustainability
One of the main uses of the industry for recycled glass is that of construction material. Glass suggests a wide range of possibilities since it can replace and improve the performance of other products. According to Glass Alliance Europe, glass is a fully recyclable material that can be recycled in close loop over and over again. The essential facilities for the use of glass offer a way to reduce the pollution caused by human activities. It is important to keep in mind that there are glasses that can not be recycled because they contain other components that make them contaminants for recycling glass which are:
Ceramic and porcelain
Mirrors.
Headlights of cars.
Lenses.
Lead crystal
Once the glass recycled arrives at the recycling plant, the material goes through a selective procedure in which some strange elements such as lids and labels are eliminated. Then, they are divided by chemical composition and by color, where the most common are transparent glasses, green and brown. However, the process is more complicated than it seems, since different types of glass must be differentiated, whether they are made of special composition, without lead, or other derived textures such as windows or windshields of cars. Once this is done, the glass is crushed and processed to remove adhering metallic impurities until it forms a liquid material that, before being sent to multiple production companies, is mixed with soda, limestone and sand at temperatures of 1,600 degrees.
Glass recycling helps in saving energy because less energy is required for the melting process. The amount of solid waste produced by the glass industries during manufacturing is extremely low in the glass industries as almost all glass waste (cullets) are immediately recycled and put back to furnaces to serve as raw material. When recycling glass, the emission of polluting gases into the atmosphere is reduced as well as the use of natural resources, since glass is made with sand, lime and soda. In construction, glass provides a safe way to enhance natural light into buildings which studies have shown contributes to people’s well-being and health conditions.
Case Study
To reinforce the information mentioned, a case study has been selected to demonstrate the importance of glass in the area of construction. “Increase BREEAM credits through the specification of advanced architectural glass. A Case Study” is an article published for Guardian Industries. This company headquartered in Auburn Hills, Michigan, emphasizes in different types of glass for commercial, residential and automotive markets. One of their commercial projects has been the Building 4 St Paul’s Square in London. This project was awarded by the BREEAM assessment as “Excellent" with a rating of 4 stars. BREEAM, as their website states, is the world’s leading sustainability assessment method for masterplanning projects, infrastructure and buildings. This article highlights how the use of 3,000m2 of SunGuard High Selective Super Neutral 70/41 glass and Guardian 10.8 Laminated glass, in combination with toughened High selective 70/41, helps achieve these credits. The building was awarded in 4 different categories. One of them was energy, the use of insulation in the glass allows the building to be fully equipped to maintain temperature control by reducing the use of air conditioning systems. In addition, it also provides natural light that increases the saving of light in the building. The second one, health and well being, demonstrates the design connects users with the outside environment which is healthy, and helps to gain focus when it comes to work. The third category, management, ensures safety and adequate acoustic performance throughout the building. Last one, waste, restates that there is “little-to-no waste packaging”. Even if there is wasted material, the glass can be reuse in the manufactured process. This 8-story building demonstrates that the use of glass in construction can provide advantages in different aspects and highlights its preference unlike other materials.
Conclusion
Without having to be sure of its discovery, glass is definitely one of the most demanded materials in the use of construction. Its manufacture requires a continuous process and the use of different natural resources. Once used, glass can provide different functions in the structure of a building and its characteristics change according to the consumer's need. Being a recyclable material, it helps in the sustainability of the environment by reducing the emission of gases and reuse of the same material. Building 4 St Paul’s Square in London deploys some of the reasons what makes glass so attractive for building construction.
References
Macfarlane, Alan and Martin, Gerry. “Glass: A World History.” Academic Search Complete. Accessed 1 Dec 2018.
Beim, Anne. “Glass as matter: A brief history of manufacturing and application.” Academic Search Complete. Issue 3, pp. 28-32. Accessed 1 Dec 2018.
Haldimann, Matthias. etc. “Structural use of Glass” International Association for Bridge and Structural Engineering (IABSE). https://issuu.com/iabse.secretariat/docs/sed10. Accessed 2 Dec 2018.
BREEAM. ‘What is BREEAM?” https://www.breeam.com. Accessed Dec 5 2018.
“Increase BREEAM credits through the specification of advanced architectural glass
A Case Study.” Guardian Glass. https://www.ribaproductselector.com/Docs/0/24610/external/COL656186.pdf. Accessed Dec 3 2018.
“The World Of Glass” Glass Alliance Europe. https://www.glassallianceeurope.eu/en/environment. Accessed Dec 2 2018.