Concrete Suitability and Concrete Production Methods - Literature review Example

Concrete Suitability Student’s Name Subject Professor University/Institution Location Date Introduction Concrete is a combined construction material which is composed of aggregate, water and cement. Its primary substitutes are the aggregate which is coarse gravel and crushed rocks of granite and lime stones and fine aggregates of sand. Concrete widely makes architectural structures including roads, walls pavements and bridges among others. This is due to its compressive strength. Its suitability and sustainability is based on concrete recycling, versatility, durability, low maintenance, affordability, locally production and use among others. Concrete production methods As Lee & Kang (2004, p.73), argues, the cement is used as a binder for aggregates with the common ones being the Portland cement, and cementations materials like slag cement and fly ash. Its varied properties are determined by formulation modes. Along with, there are various chemical admixtures added to it in order to achieve some varied properties. Water then solidifies the dry composite, shaping it and hardening it into a rock-hard through hydration. The end product is a robust stone-like material. This gives rise to different types of concrete which are created by varying proportion of ingredients. The finished product depends on varying strength desired, the density, and thermal and chemical resistance properties. The mix design primarily depends on the type of structure that is being built, concrete mixing and delivery and placement to form the structure. Concrete is generally created by combining some chemically inert minerals such as sand and gravel with a binder. Water and chemical additives are used to complete the mixture. The proportion of concrete materials mostly include one part of cement, two fine aggregate and four part of coarse mineral aggregates. The formula is not standard and can be altered so as to adapt the strength needed for a particular structure. The aggregate form 75% of concrete volume, and is a function that improves its formation and increase strength. According to Mahboubi & Ajorloo (2005, p.412), the properties of concrete depends on its two major groups; fresh and hardened concrete. Fresh concrete is mounded to a plastic state, which is called ‘Green Concrete’. This determines the ease with which the concrete will flow. Hardened concrete is achieved through setting, which is hardening it. Setting is affected by water cement ratio, cement type, content, fineness, suitable temperature and relative humidity. Wide variety of equipments is available for concrete processing. Technical details affect the nature and quality of the product. The gel reacts aiding mixing and placement and the curling process completes the hydration process. Some of the most concrete qualities desired include the mechanical strength, volumetric and chemical stability and low moisture permeability. However, since concrete has lower tensile strength, it is always reinforced with materials like steel which are strong in tension (Oner, Akyuz & Yildiz 2005, p. 1165). Construction methods Through innovation, concrete industry has embraced modern methods to offer concrete solutions. This is used to reduce the construction time, offer cost saving and to promote sustainable development. 3D Volumetric construction involves a three dimensional unit’s production through a controlled factory conditions that occur prior to transportation to the site. Modules are then brought to the site in various forms, from basic structure to those with internal or external finishes installed. There is also a precast flat panel construction. In this case, the floor and walls are produced off-site and erected on-site forming robust structures. Factory fitted insulation with decorative cladding improves the structures. This gives the speed of erection, quality and accuracy. Flat slabs are quickly built and give rapid overall construction and simplify the installation process. Flat slabs construction has little restrictions on partitions and positioning horizontal services. This promote and gives the occupier considerable flexibility to easily alter the internal layout to accommodate changes and usage of the structure. Post tensioning of slabs allows thinner and longer slabs. This, together with little reinforcement offers labor advantages and significant program me. Tunnel form, hybrid concrete construction, thin joint masonry and insulating concrete formwork are other forms of concrete construction methods. The various methods can be used together and interchangeably, depending on applicability, effectiveness and efficiency desired (Mehta 2004 May, p.9). In large structure, such as the gravity dams and bridges, concrete is placed in formed horizontal blocks. It however, generates excessive heat with associated expansion. As a way of mitigating this, post-cooling commonly provided improves the design. A network of pipes between concrete placements circulates cooling water in the curling process. This avoids damaging effects of overheating. The volume of pour, concrete mix used ambient air temperature may require a cooling process that last for months, after placing the concrete. Concrete is generally applied in pre-stressed structures, reinforced to construct a compressive structure. Concrete is a durable building material with superior fire resistance and its applicability is determined on how it gains strength overtime. Most of concrete structures have long life. Concrete textures can be improved during construction from its usual dull and gray concrete. Concrete is cast and molded to different textures in order to enhance its decorative applications. Sound wall, office building and bridges are decorated through optimal canvases of concrete art. Durability and “end of life” considerations As Mehta, (2004, May, p.3) observes, concrete is amongst the most durable of the building materials. It has superior fire resistance as compared to the wooden construction. It also gets strength overtime giving it longer service life. Due to these reasons, it is mostly used man-made material in the world as compared to other construction materials. Concrete cannot burn and therefore concrete buildings are resistant to fire. The risk of structural collapse greatly reduces since it effectively shields fire. This provides the most non-combustible options, including the floors, roofs and ceilings mainly from hollow-core and cast-in-place concrete. Hollow blocks with fire proof insulation foam create durable structures. Concrete also provides resistance to high winds, tornadoes and hurricanes due to lateral stiffness that reduce horizontal movement. If properly reinforced, concrete weak tension is less affected in case of an earthquake. Large shear loads generated on the structures by earthquake are generally reduced through the use of steel reinforcements. Seismic retrofitting of buildings at-risk greatly reduces severe earthquake shaking. Important still, is the ability of concrete which is not weakened by moisture, pests or mould. Concrete structures withstand natural disasters with Roman buildings of over 1,500 years’ structures as examples of strength and durability of concrete. It is versatile as it applies to buildings, tunnels, bridges and others with low maintenance cost. This is because, concrete is inert, non-porous and compact and thus, it does not lose its properties or attract mould. According to Khatib, (2005, p. 768), concrete recycling has become a common method when disposing concrete structure. The concrete debris which once was used for landfills is gaining more recycling options as environmental awareness ensues. Government laws and its particular economic benefits promote recycling. This concrete free of trash, paper, trash and other materials is collected, crushed with a machine along with asphalt, rocks and bricks. Reinforced concrete with metallic reinforcements is removing with magnet for recycling. Smaller pieces of concrete are used as gravel for construction projects. The aggregate base gravel can be laid down as lowest layer when constructing roads. Nevertheless, concrete is damaged by many processes including the expansion of corrosive products such as steel reinforcement bars. The freezing of trapped water, radiant heat, bacterial corrosion, aggregate expansion, leaching, erosion and sea water effects are most necessitating factor to its damage but can be substantially controlled. Justification of material choice The justification of concrete basically is derived from its proved characteristics. One of the significant one is strength and durability which makes it the most used in majority of buildings, tunnels and bridges. Significant still is its ability to gain strength over time. This makes it possible for significant structures to withstand most of common occurring natural disasters. The second cause of justification is based on affordability which, when compared to other building materials, it is less costly in production. It is also locally produced and thus reduces the transportation cost in most cases. The amount of cement and concrete transported and traded internationally is limited. This also reduces emissions of C02 which occur through transport. Low maintenance, fire resistance ad slow thermal passage makes them more suitable and desirable. Finally, with recycling innovation, a large percentage of concrete from demolition is re-used and thus adds an economic advantage and sustainability (Mehta 2004 May, p.7). References Khatib, J. M. (2005, ‘Properties of concrete incorporating fine recycled aggregate’, Cement and Concrete Research, 35(4), 763-769. Lee, K., & Kang, K 2004, ‘Feature dependency analysis for product line component design’ Software Reuse: Methods, Techniques, and Tools, 69-85. Mahboubi, A., & Ajorloo, A 2005, ‘Experimental study of the mechanical behavior of plastic concrete in triaxial compression’ Cement and Concrete Research, 35(2), 412-419. Mehta, P. K 2004, May, ‘High-performance, high-volume fly ash concrete for sustainable development’, In International workshop on sustainable development and concrete technology (pp. 3-14). Beijing: Kejin Wang. Oner, A., Akyuz, S., & Yildiz, R 2005, ‘An experimental study on strength development of concrete containing fly ash and optimum usage of fly ash in concrete’. Cement and Concrete Research, 35(6), 1165-1171. Read More