Introduction to Autoclaving in Bricks - Report Example

Autoclave Bricks Name Date Affiliation Autoclave Bricks Introduction to autoclaving According to (Du et al,2014,p.295) autoclaving is the process of sterilizing equipments and supplies using high pressure that is under saturation in 250F and above an equivalent of 121 degrees centigrade and above for approximately fifteen to twenty minutes. The process has wide usage and more especially in the field of medicine, microbiology, dentistry tattooing and veterinary science. Zhao et al, (2012,p.452) adds that auto claves are machines that can use pressurized steam for the purpose of eliminating micro-organisms and it is on of the best mechanisms of eliminating organisms through decontamination. Under normal circumstances, autoclaves make use of damp heat (180 degrees to 220 degrees) and therefore, some materials like plastics and paper cannot go through the process of autoclaving. Autoclaving is highly applicable in sterilizing medical waste before disposal making it an ideal method of killing organisms and microorganisms found in such wastes. When compared to incineration, it is a better method of treating disposals because it does not pose any health complication towards the users. Moreover, autoclaving is highly applicable in the process of rubber vulcanization as well as curing the composites because the temperature from the autoclaves makes it possible to attain products that have the best physical properties (Du et al, 2014, p.295). Autoclaving in bricks On the other hand, autoclaving is a method of making bricks because of the ability to remove microorganisms that can alter structures after construction. The presence of high temperatures and pressure makes it possible for the autoclaves to eliminate any form of micro-organism that can destroy the micro-organisms found in the raw materials used in the preparation of bricks. Autoclaved products are the best construction materials because they free from microorganisms and bacteria that might trigger biological processes such as decomposition and withering hence destroying the structures made from such materials. Therefore, autoclaved materials and especially brick s are the best types of construction materials that any construction company can use (Du et al, 2014, p.297). Autoclaving machines have standardized temperature and pressure making it possible for the brick or the autoclaved material to have the desired physical properties. For instance, during vulcanization of runner, the autoclave machine makes different physical properties depending on the usage of that particular product. For instance, the tires and fan belts for heavy machines must exhibit strength and toughness so that they can withstand weight and pressure. On the contrary, rubber products that need not to be tough and strong are also part of the process of autoclaving. Therefore, autoclaving is a crucial process of making durable products from different products (Roux et al, 2009, p.680). According to (Zhao et al, 2012, p.455) sustainable construction and considerations of energy are some of the factors that have the brick autoclaving common in the world today and more especially in the industries. The choice of material to use in the cementious systems normally requires efficient usage of the natural materials that are no renewable. In masonry, most of the materials used are the concrete and clay bricks making them useful products in the industry of construction. Energy considerations from the manufacturing of cement and baking of clay create a gap of efficient usage of energy giving a platform for usage of autoclaved bricks. For instance, in Algeria the common construction materials are cement blocks and burnt clay bricks that are in high demand totaling to 15 million tons annually. However, the country does not satisfactorily provide these building blocks making it essential to get another source that is cheaper, environmental friendly and sustainable as per the millennium developmental goals. Moreover, research indicates that the intensive demand for clay bricks in Algeria threatens ecological balance because the deposits of the alluvial deposits diminish day by day making it difficult for the process to continue. Therefore, the only option that the country has is to use the limestone bricks (calcium silicate) bricks made through the process of autoclaving replacing the burnt clay bricks. Usage of the silicate bricks will reduce the cost of production in terms of energy and at the same time encourage sustainability according to the millennium, development goals (Zhao et al, 2012, p.455). Autoclaving in current bricks manufacturing industry Calcium silicate is an artificial stone normally obtained mixture of sand and lime when put in high temperatures a well as the saturated pressure and the process is the renowned autoclaving. The process of autoclaving (high pressure and temperature) creates hard and durable products than are usable after ten or so hours. The high temperatures cause disintegration of molecules and they become free. On the other hand, the high pressure makes it possible for pressure to compact the molecules to an extent that they combine under high temperature to form new product that is compact and durable. The product is calcium silicate bricks that are essential in the construction industry. The importance of the silicate bricks underlies the permanence and in ability to react with water due to the insolubility. This ultimately turns to be the most productive construction material because of cost efficiency and durability (Jinrui, Wen & Qingmei, 2007, p.85). According to (Huimin, 2013, p.21) calcium silicate achieves the hardness through the process of carbonation of lime after several exposures. Under the effect if saturated vapor and temperature that varies from 170-200 degrees centigrade, the fine-grained quartz in occasionally insoluble in ambient temperatures turns to be chemically active and eventually reacts with the hydrated lime (Calcium hydroxide). The ultimate product is hydrated calcium silicate which is solid and resistant and at the same time insoluble in water. () asserts that hydrothermal treatment of lime and mixture of sand in the autoclave form of calcium hydrated silicates in the forms of hydrated calcium silicate. Subsequent studies indicate that probable existence of C-S-H depends on the initial calcium and silicate mixtures as well as mixture ratio and temperature. According to () C-S-H systems under hydrothermal conditions is usually metastable with temperature and Calcium and Silicate variations. Moreover, () assets that from 120-220 degrees centigrade, thermal treatment of the quartz-lime powder mixture produces an amorphous substance that does not have definite compounds according to the analysis of X ray followed by crystalline compounds that are in the form of tobermorite and C-S-H (Huimin, 2013, p.21). (Zhao, Zhang & Chen, 2012, p.162) goes ahead to assert that C-S-H (hydrated calcium silicate) has the actual chemical composition of tobermorite making an ideal compound for the autoclave process. Moreover, Taylor and Dyczek observed that similar results are evident in similar temperatures qualifying tobermorite as a compound for the process. At temperatures above 220 degrees centigrade, these minerals crystallize to form final products known as gryolite or lime that is rich in C-S-H. Several authors have profoundly demonstrated that there are differences in substance composition from materials derived from autoclave. These eventually turn out to be tobermorite appellation commonly known as the 14A, 9A, 11A tobermorite. Under normal circumstances, some of these are normal while others are anomalous with variables of crystalline. Tobermorite are stable and obtained at 0.8 to 1 calcium silicate ratio and they form good and efficient bricks by the end of the day (Zhou & Qu, 2011, p.830). According to (CSIR-CBRI, 2011) lime is a basic component of blast furnace slag especially in the formation of C-S-H. Simply by the virtue of the chemical constituents, that are similar to cement, blast furnace slag are applicable in cases that need lime. Algeria produces blast slag at an estimate of 500,000 tons and it is not widely applicable in the civil engineering work. Rapid cooling of slag results in formation of meta-stable structure with appearance of glass that favors reactions with lime in specific conditions. The granulated slag has ultimate properties of hydraulic depending on the chemical composition of the materials in the blast furnace. In addition, slag can also react either through activation mechanically or thermal activation in steam rooms that facilitates autoclaving. Blast furnace under normal circumstances must have hydraulic activity and it indicates some cement properties especially when it is contact with water over quite a long time. In the presence of lime (calcium hydroxide) or cement, the kinetic energy accelerates due to presence of temperature prompting further reactions. At this point, the point the granulated slag has amorphous structure and it transforms into various new phases that corresponds the hibschite as well as the tobermorite when temperature ranges from 170-200 degrees centigrade (Jain, Garg & Rai, 2013,p.78). Industrial manufacturing autoclaved bricks go hand in hand with the desire to produce products directed towards development of new technology that will utilize and recycle the clay-brick waste materials to form renewable construction materials that is the autoclave products. The desire to keep environment clean as well as economic factors has prompted industries to start manufacturing autoclave bricks. Each year, many houses where construction and demolition takes place and the waste products deposited in the landfills. For instance, according to the Environmental Protection Authority (EPA) of the northern section of Australia have approximately 25% of construction and demolition products that eventually end up landfills. The 25% of the construction and demolition products forms approximately one million tons, which can be useful through application of new technology. For instance, the Alumina –Silica industrial wastes in form of fired clay is under heavy production especially during production, construction and procedures of transportation because large amounts end up breaking (Zhou, & Qu, 2011, p.830). (Saijun & Chang 2011, p.6568) posits that clay-brick in finely grounded state normally exhibits the high pozzolanic activities normally under the ambient conditions. Hydrothermal curing commonly known as autoclaving is a process that affords rapid strength developments by using saturated steam under high pressure enhancing chemical equations that reactivates the pozzolanic materials. (Al-Otaibi et al,2010,p.127) demonstrates that formation of the 1.1mm tobermorite which is the principal building agent of the renown calcium silicate product is possible through addition of the finely grounded clay-bricks to the mixtures of the ordinary cement from Portland(OPC) and the quartz sand. Various studies report that compressive strength in manufacturing of calcium silicate products that contain the tobermorite as the main binding factor. The other factors that need consideration are paramount in relation to the compressive strength and include the amount of Crystalline to the amorphous materials that bind them at a given porosity. The size of the particle and the distribution amount of that does not react through starting the material by the habit of the tobermorite. The resultant products exhibit high quality and the embodiment energy for constructing a house made of autoclave brick is far much lower in comparison to the operational energy. The graph below indicates the number versus cumulative energy in relation to the embodiment energy. The above graph indicates the number of years in relation to cumulative energy and it is citation from (http://www.yourhome.gov.au/materials/embodied-energy.) As posited above, construction industry has intensively demonstrated ultimate interest of utilizing solid waste rich in Aluminum Oxide and Silicon Oxide. The fired clay bricks that are fine exhibit high levels of pozzolanic activities even in ambient conditions. In the other words clay brick residue hardens in water with introduction of calcium hydroxide where by the calcium ions gets to the mixture just like in the case of Portland cement. The chemical activity of pozzolanic materials normally increases through introduction of high temperature and especially through autoclaving. According to (Al-Otaibi et al,2010,p.127) autoclaving refers to the process of curing the saturated steam under a given pressure and most typically through passing it at 180 degrees for several hours by using the mixture of Portland cement or calcium hydroxide at 30to 80% of mass . Under normal circumstances, the process affords the manufacture of the cement-based construction materials with a principal advantage of a permanent and early strength equivalent to that of 28 days in the ambient cured products. Moreover, the industrial autoclaved cement products of building have a specific quantity of cement and quartz in a given ratio following the 40:60 modes. (Huimin, 2013, p.21) asserts that formation of 1.1nm tobermorite is possible through addition of fine grounded clay-brick waste that blends well with OPC and quartz sand. The tobermorite is the most important hydrous calcium silicate phase and it serves as the principal binder providing matrix strength that has close associate with autoclaved cement-made bricks. Extensive thermal analysis took place facilitating the evaluation of hydration products. Cycles of Autoclaved bricks production Many countries that value the environment have prohibited use of clay bricks more-especially, because clay is great contributor to destruction of environment. On the other hand, autoclaved bricks like asserted by many people have turned out to be the favorite of many people in the developed and developing countries making it an ideal source of construction material. There are several production lines for autoclaved bricks such as the autoclaved lime -sand brick production line, and the renowned autoclaved fly-ash brick production line. Automatic hydraulic brick machines are the main driver in the process of making autoclaved bricks. Various types of machines that are applicable in the process of making bricks and such include; DY1250 block machine, the DYS430 block making machine and the DY1100 block making machines. These machines work in the same very just that the mode of construction a bit different though the final product ends being the same (Huimin, 2013, p.21). Various specifications must take place whenever an individual goes through the process of making the autoclave bricks. For instance, the PLC automatic closing must take place whenever an individual embarks on the process. It is the first process that must take place. The second is high automatic production line, third involves the automatic hydraulic brick manufacturing machine, fourth is the electric control system and fifth is the good quality and the after sale service. These steps form the production process of the autoclaved bricks. When making the fly-trash brick production, some of the main raw materials includes the fly ashes and lime. However, the lime-sand autoclaved bricks use sand in order to replace the fly ash. The process of autoclave brick production involves preparation of raw materials so that they can meet the required threshold and ultimately come up with a desirable and quality product (Huimin, 2013, p.21). In the process of autoclave production, the common materials include the fly ash, sand from the river, Aeolian sand, depositions of sand, as well as the concentrator of minerals. A jaw crusher is crucial in attempt to reduce the covers and the area of each one to facilitate crushing and mixing at the same time. Under normal circum stances, the size of the jaw crusher should be less than 30mm. the materials normally reaches the ball mill through conveyor belts to facilitate fine grinding and ultimately sending them to the bin(Cicek & Tanrıverdi,2007,p.1297). The common ingredients have fly ash, sand; quick lime that involves the industrial waste and this reduces the cost of production. The figure above indicates production autoclaved bricks (derived from https://www.google.com/search?q=images+showing+the+production+process+of+autoclave+bricks&biw=1024&bih=649&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=g1lrVeL8MdGu7Aa7goCgCg&ved=0CB4QsAQ.) The figure illustrates a detailed production line of autoclave bricks derived from (https://www.google.com/search?q=images+showing+the+production+process+of+autoclave+bricks&biw=1024&bih=649&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=g1lrVeL8MdGu7Aa7goCgCg&ved=0CB4QsAQ.) The autoclave diagram cited from (https://www.google.com/search?q=images+showing+the+production+process+of+autoclave+bricks&biw=1024&bih=649&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=g1lrVeL8MdGu7Aa7goCgCg&ved=0CB4QsAQ.) The above diagram is an illustration of autoclave aerated brick machine that is among the best brick-making machine in the industry. The brick-making machine employs heavy technology coming up with the best products in the market. The introduction of PLC technology makes it an ideal in the modern industries. Energy efficiency and affordable maintenance costs make it ideal machine for business-oriented industries. The autoclaved machine diagram cited from (https://www.google.com/search?q=images+showing+the+production+process+of+autoclave+bricks&biw=1024&bih=649&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=g1lrVeL8MdGu7Aa7goCgCg&ved=0CB4QsAQ.) The above autoclave brick-making machine is among the best in the market and it employs the processing technology of finished bricks that extends from ends of autoclaved brick production to the finishing and parking line. Under normal circumstances, the machine can pack an entire wagon of the finished bricks immediately after getting out of the autoclave. The machine helps in reducing the amount of bricks that ends up breaking in the process of loading them to the trucks for further transportation. The ability to pack the bricks in stacks reduces the chances of such bricks breaking hence making it ideal for the purpose. In the same breath, it cost effective in terms of maintenance and initial cost making it ideal for large autoclave industries (Cicek & Tanrıverdi, 2007, p.1297). Methods of autoclaving bricks As posited above, autoclaving involves a process of treating clay-brick waste and OPC (Portland cement) products at high temperature of around 180 degrees and pressure to produce quality products that are strong and tough. For instance, the autoclaved aerated brick is usually a lightweight material of construction. Comparing this with concrete blocks, it is evident that exhibit lower density and that makes suitable for constructing simple structures. The low density emanates from voids in attempt to produce cellular structures. The voids are typically 1mm-5mm across and they normally give the material a unique characteristic in appearance. Under normal circumstances, the blocks will have strength ability ranging from 3-9 Nmm according to the BSEN 771-1:2000(Cicek & Tanrıverdi, 2007, p.1297). The densities of the products range from 460 to 750kg/m-3. The autoclave bricks normally go through an autoclave process that exhibits high pressure and temperature vessel. The steam in the vessel hits 800kpa while temperature reaches 180 degrees and that is appropriate for the process. The high pressure and temperature creates a room where chemical equations can take place resulting to formation of entirely new products. As indicated above, autoclaved bricks can emanate from range of activities and they include combining the Portland cement, pulverized fuel ash and lime. The combination produces quality bricks that are durable and efficient in large-scale construction. Moreover, the manufacture of bricks can emanate from combination of silica, Portland cement and lime. Combing the three components under 1800kpa and 1180 degrees of temperature produces quality bricks that end up in the construction sites (Cicek & Tanrıverdi, 2007, p.1297). The composition of autoclaved aerated bricks is entirely different from the dense concrete in the means of production and the ultimate composition of the product. The dense bricks normally go through the same production method but it is a mixture of water and cement and occasionally with the PFA or the slag. The product normally gains strength because of the hydration of cement reaching to approximately 50% of the final length. Under normal circumstances, the autoclaved bricks take approximately8-10 hours to get ready especially for the high-density types. The long period of 8-10 hours allows them to get maximum pressure and temperature ultimately producing quality products that are durable and strong. The high pressure and temperature gives room for production of quality bricks measuring 600mm by 200mm. the size is approximately eight times bigger than the burnt bricks indicating the efficiency of the autoclave process (Jain et al, 2013, p.56). Average price of autoclaved bricks in Australian dollar According to the current trends in the market, the accepted market price for autoclave bricks is a range of 1-2Australian dollar $ depending on type and the component. Buyers will purchase the bricks in bulk but and they receive discounts bringing the average price per brick lower. As posited above, the materials used in the construction of this bricks are sand and fly ash. They are essential materials in the construction work because they reduce dead weight of structures as well as accelerating the speed of construction especially when used for flooring and building the walls. However, basic cost of the products appears to be high when compared to other materials of construction. This is because they are light in weight and structure prompting them to the best materials for construction. When making the autoclaved bricks, it is possible to make aerations within the bricks by using a foaming agent developed in Germany and later patented in Neapor (Jain et al, 2013, p.56). Moreover, there are various methods used in making the CLC bricks depending on the productivity required and the required investment. However, the economic method used in Australia includes usage of the hydraulic press and tunnel driers for autoclaves. Most of these equipments are readily available in Australia and this makes it possible for the industries to make the products conveniently. As indicated above, quality of the product determines the choice of materials for making the autoclave bricks. For an industry to produce quality autoclave bricks, the autoclave ovens must have the required quality and efficiency. For instance, an ideal autoclave oven must have the following features; Programmed pressure, heating and cooling, and Controlled water cooling systems. The oven material must be strong enough to withstand pressure and temperature (Saijun & Chang, 2011, p.6890). In addition, the openings must have a strong seal to prevent loss of heat or entry of air. The internal sections must have fans that will regulate movement of air within the oven. These specifications determine the quality of the autoclave oven. The most important specifications of the autoclave oven include the pressure vessel, materials, and doors, cooling, interior and heating. For example, the outer cover encapsulating the pressure vessel must have the required thickness to withstand the high pressure from the inside. The materials used for fabricating the autoclave material must be stable enough to an extent that they will not react. For instance, for the steam autoclaves, carbon steel is the best because it will prevent corrosion from taking place. The doors are crucial components of autoclave machine and they are the most expensive parts of the autoclave. They must be full diameter to allow enough working space and bear enough seal against loss of temperature and pressure. The heating and cooling systems must also exhibit high quality to facilitate effect effective autoclave process (Huimin,2013,p.21). Autoclave brick making method in comparison to other methods Autoclaving as a method of making bricks has received warm welcome in Australia and other countries like India and Algeria. The essence of using the autoclaved bricks in many countries today agrees with need to conserve the environment. Autoclave uses the remains clay brick made through furnace burning. There is a lot of waste that emanates from the process and autoclave process makes use of such products. This makes the process economical and at the same time conserving the environment. Conservation of environment is part of the millennium development goals hence making the process sustainable. The alluvial soil deposits used for making the clay bricks will not exhaust easily because the process makes use of every byproduct. Massive embrace of the process indicates that people find it good and ideal method (CSIR-CBRI, 2011). Moreover, the process of autoclaving involves a series of reactions and chemical reaction is part of the reaction that takes place. The high temperatures and pressure are conditions that facilitate the chemical products within the Calcium carbonate (OPC) and the silicate component to react forming products that are stable and insoluble in water. The reaction produces products that are stable and will not react with the environment at any given time. For instance, autoclave products (bricks) are stable that will not spoil even when exposed to extreme conditions of weather. This is an indication that autoclave brick making process is economical and the resultant products have exquisite quality (CSIR-CBRI, 2011). Comparing the autoclave bricks with clay bricks, they have high quality in terms of durability and physical outlook making them ideal for construction. In Australia, various companies produce the autoclaved bricks because they are marketable commodities whose demand increases day after day. Some of these companies include the PGH brick and pavers. The company has operated over one hundred years making clay bricks but they started making the autoclave bricks. They make strong and durable products and their reputation has reached all over Australia. The company is a division of CSR house of brands along with Wunderlich and Monier roofing tiles. The conglomeration helps the companies to provide full construction for the Australians. Sto New Zealand and Australia is another company that provides the autoclave bricks to the Australian civilians. The brands produced by this company exhibit high quality and that attract many clients. According to () Sto is the best international company providing the interior and exterior construction solutions (CSIR-CBRI, 2011). Conclusion Autoclave process involves use of high temperatures of 180-220 degrees and 1800kpa to facilitate formation of bricks. Autoclaved bricked are the best bricks in the market today. The autoclave machines (pressure ovens) are different depending on the carrying capacity and the manufacturing company. The specifications of the autoclave oven determine the type of the bricks produced. However, the best machines produce the best bricks in the market. The raw materials for producing the autoclave brick are the byproducts of clay bricks (limestone - calcium silicate) produced in masses from the production factories. When calcium silicate and other elements and compounds within the clay products react under the high temperature and pressure, they produce quality products. The quality and environmental concerns related to autoclaved bricks has prompted many Australians to continue buying and using the bricks for construction. The trend indicates that in the next five years, people will entirely build their homes using the autoclave bricks. References Al-Otaibi, S., El-Hawary, M., & Abdul-Jaleel, A. (2010). Recycling crushed concrete fines to produce lime–silica bricks. Proceedings of the ICE-Waste and Resource Management, 163(3), 123-127. Cicek, T., & Tanrıverdi, M. (2007). Lime based steam autoclaved fly ash bricks. Construction and Building Materials, 21(6), 1295-1300. CSIR-CBRI, R. (2011). SAND-LIME BRICKS. 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Experiment on Making Autoclaved Sludge Bricks with the Dewatered Sludge from Water-Supply Plant. Advanced Materials Research, 261, 829- 833. Read More