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Durability and hardness: - timber has remarkably good resistance to deterioration by atmospheric exposure- it is virtually unaffected by agencies such as rain, frost and acids, which responsible for damage to other materials. The action of sunlight is only slight, prolonged exposure degrading the lignin adhesive so that the timber surface is bleached, becoming slightly fibrous. The mechanisms of attack involve its being used as food- by plants in the form of fungi and by insects.(…)
Heat conductivity: this is quite low; the coefficient of heat conductivity along the fibred is 1.8 times greater than that, across the fibred and average 0.15 to 0.27 kcal/mh°c. As the bulk density of wood increases and its moisture content decreases, the amount of air entrapped inside cavities decreases.
Cement may be classified as hydraulic and non-hydraulic. The non-hydraulic doe not set and harden in water while the hydraulic set and hard in water such as porthland cement. They can be either manufacture from natural cement stone or artificial by using calcareous and argillaceous materials.
Initial and final setting time: the setting implies the solidification of the plastic cement paste. Initial and final setting times may be regarded as the two stiffening state of the cement. The beginning of the solidification is called initial set which mark the point in time when the paste has become unworkable. The time taken for the cement to solidify completely is called the final set, which should not be too long in order to resume construction activity. The initial and final setting time is the rheology property of cement. The initial setting time for the cement that was used is <45minutes and the final setting time is <10 hours. It has the same setting time as that of Ordinary Portland Cement.
Aggregate are the materials basically used as filler with binding material in the production of mortar and concrete. They are originated from either igneous rock, sedimentary rock and metamorphic rock or manufactured from blast furnace slag etc. aggregate form the major part of concrete they reduced shrinkage and effect economy. They occupied 70-80% of the volume and have considerable influence on the properties of concrete. They should be clean, hard, strong, durable, and graded in size to achieve utmost economy from the paste.
Quarrying process: the process of manufacturing aggregate is a multi stage process; it starts with the extraction of rock from the ground and crushing them to produce aggregate. Then extracted rock are screen into size as required for immediate or further use and processing .the process start with three stages of survey of the quarry face this help the engineer to design the blast and where the shot hole will be drilled so that the blast can be carried out safely and efficiently after the drilling of the shot hole using an air operated drilling rig, the dynamite are used in blasting the rock. A single blast can fragments up to 60,000 tons of rock. After the blast, the shot pile where cleared up by the use of face shovel or loader and then load the truck dumper that will convey the rock to the crusher. The granite particles are fed into the crusher. The crusher is design to reduce the particle between 1-4 feet in diameter into pieces approximately 5-6 inches in diameter. After the initial crushing, if the minimum size is not attained the aggregate are fed into the secondary crusher. The process only involves modification to attain the best aggregate size required. To get a specific grading size ; the sieving tray are placed one on top of another, with the sieve having bigger opening being placed immediately above the one with smaller opening. By so doing the smaller particle go to the bottom of the tray and the bigger ones are separated on different level.
Before assessing the suitability of any material for a given situation, the performance requirement for that situation must be identified. The individual component system of a building are very much interested; changing any one part without consideration of then others can create a domino effect with catastrophic outcomes. With knowledgeable consideration of the building as a system philosophy change in one part can augment the performance system and the building as a whole. Below are some points that should be considered while going for the material selections:
Renewability: Are the products made from material that is rapidly renewable such as cork or bamboo? Wood products are also a renewable resource. Choose wood products that are FSC (Forest Stewardship Council) certified. Many engineered wood products are made from fast growing trees such as aspen and require less wood to make them than conventional lumber.
Construction materials that are used in the manufacture of Concrete, cement is the most important material used. Without cement, concrete would not even be called concrete. A mixture without cement would be easy to breakdown and wash away; collapse of the building would be inevitable. Cement is responsible for the hardening process that takes place in concrete mixes. This property ensures that the concrete is stays in place as designed by the architects, and it also helps the building to perform as it was designed to. During the early stages of the manufacturing of concrete, when it is in its plastic condition, a mould of any design can be made since the cement in that condition can flow into any shape with the help of compaction. Simply by the property of cement having the ability to harden this process is possible. Because cement can exist in both molten and solid state (although only for a short while in the molten state) designs are less limited to flat surfaces only. Civil Engineers use this property to realize the designs of an Architect. Designs consisting of sophisticated curves are made possible. Cement is largely responsible for binding the aggregates and sand together with water. It therefore reduces the chances of voids forming in the concrete. Voids impact negatively on concrete as it reduces the strength of the concrete. Cement contributes very effectively to the strength of the hardened concrete. According to the water-cement ratio, the strength of the concrete varies. This shows how dependant the strength is on cement. It gives the structure the strength required to support it and its load. It makes concrete durable and last long, very minimal damage can be done to concrete, it also reduces the chances of an insect-attack. Impact of chemical attack is reduced significantly as well, cement is not very reactive to many substances, except alkaline ones, and however, chemically resistant cements can be used in such cases. Cement is, however, also responsible for certain problems that may be sited in concrete; cracks are mainly caused by cement, when cement hydrates very fast crack form; shrinkage can be observed when as a result of fast hardening as well.
Concrete recycling: concrete from demolished building is put through a crushing machine. The crushing machine accepts only uncontaminated concrete, which must be free from trash, wood and other material. The aggregate chunks are stored by size; larger chunks may go through the crusher second time to reduce the size. Crushed concrete has lower strength and higher water absorption characteristics than primary aggregates. This makes mix design more difficult. One of the problem associate with the use of the crushed concrete as an aggregate is the large variation in quality and this rule out its use for structural concrete. This crushed recycled concrete can be used as the dry aggregate for brand new concrete if it is free of contaminant.
Bricks recycling: recycling of bricks is a process of reusing the demolished or old clay bricks from an old building. However, older masonry is easier to recycle because they are mostly built using lime mortar. The recycled clay can be used as loose fill or backfill material in civil engineering works. The clay bricks is collected from the demolition site and then transported to the plant were is been feed into the crushing machine.
Sustainable material: sustainable material are that material can be produced and used in an environmentally compatible ways as without any technical loss in quality of the end product. They are building material that are comfortable, healthy, internal condition are achieved, whilst minimizing environmental impact associated with construction and operation, the goals are set to conserve natural resources and minimize waste quantity, as well as the reduction of further environmental effect like the consumption of non-renewable energy and emission into soil, water and atmosphere. There are four key principles for sustainability, they are:
A building defect is that which makes a building dangerous, unsafe or causes real damage to the user. Building defects affect society at large due to possible danger posed; they also result indirect and indirect cost in repairs, abnormally high maintenance, disputes and possible loss of building use. Defects in building construction is not only contributes to the final cost of the building but also to the cost of maintenance, which can be substantial. Defect in building may lead to the complete failure of the building. This defect is generally caused by inadequacies in design, poor workmanship, building usage not in accordance with design and lack of or incorrect maintenance and poor selection of material used.
Preservatives should be toxic to fungi and/ or insects as required, be of sufficient chemically stability for their operational environment, be able to penetrate timber and be non-aggressive to surrounding materials. The first step in ensuring the durability of a timber is a careful assessment of the environment in which the timber is to be used so as to identify the risk. This identification of risk will help in giving recommendations for preservative treatment of timbers to be used for structural purposes so as to protect them from degradation by wood-destroying organisms. It does not deal with the protection of timber against fire, or with preserving the appearance of timber against weathering or staining.
These are generally odorless and non-staining with no restrictions on decorative treatment, making timber so treated suitable for both internal and external use. Because of the waterborne nature of this type of preservative, it may be necessary to re-dry the timber to acceptable moisture content. Waterborne preservative treatment consists of salt based on metal such as sodium, magnesium, zinc, copper, arsenic and boron. Copper-chrome-arsenate is a common example. They are fairly cheap and also have some disadvantage, they can cause swelling of timber and will cause corrosion of metals in contact until drying out is complete, which may take up to 7 days, depending on the type of timber and section thickness of the timber.