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摘要：The building industry and the civil engineering industry together are often referred to as the construction industry, and many firms operate in both sectors, even though their staff and organizations may be largely separate.

uantity of material left in place. That is, if the actual quantity of concrete required is 100m² and the waste factor is 5%, the amount of concrete to be procured should be 105m². (Calin,M 2003)
6.1 Concrete
Like other direct costs, the total direct cost of concrete work is the summation of all costs including labor, equipment, material, and subcontractors required to complete the work. Concrete is currently one of the most common and extensively used materials in construction. Cost of labor, equipment, and materials in concrete construction are relatively high. (Calin, M 2003)
Typically, concrete work consists of two major components, structural and non-structural. Structural elements are the major components in concrete building construction. They include footing. Concrete pilings, foundation walls, slabs in grade, columns, beams, above –grade floor structures, wall structures, abutments, roof structures, and other special elements such as stairways. The structural elements can be made from lightweight, normal weight, and heavyweight concrete. (Calin, M 2003)
Concrete work requires a significant number of crafts and the cost of crafts is normally high. An estimator must therefore include the costs of desired concrete construction crafts in the cost estimation.
Take off methods for Concrete Cost Estimating
One of the most common take off needs for concrete work is concrete volume. As shown in Eq. (6.11), concrete volume is simply determined by the multiplication of the length, width, and height (or depth) of a structural unit.
Volume (m³) = Length (m) ×Width (m) ×Height (m) (6.11)
As shown in Eq. (6.12), concrete area is the product of the length and width of a structural unit.
Section Area (m²) = Length (m) ×Width (m) (6.12)
Even though the multiplication seems to be a simple task, an estimator can make mistakes due to unfamiliarity take off methods. There are three methods used to perform the quantity take off for the concrete work. They are differentiated by how the area of a structural component is determined, namely, the unit, perimeter, and centerline methods.
Concrete is one of the major and most common materials used in current construction. It is widely used because of its strength, durability, water tightness, and resistance to scratching and freezing, thawing, and some chemicals. Additionally, concrete is the principal material for many other construction components such as masonry units, mortar, grout, and precast concrete units. Typically, concrete gains more strength as it gets older. Its strength also depends on its major ingredients. (Calin, M 2003)
Concrete is basically a mixture of cement, water, and aggregates. Cement usually contains, by volume, from 10 to 15% of the total concrete mix. One cubic meter of cement is approximately 1510 kg. The most widely used cement for construction is Portland cement. It is usually made from limestone, clay, silica, iron ore, and other raw materials in a very high- temperature manufacturing process (1500︒C). According to the Portland Cement Association (2000), there are six types of cement commonly used in construction. ((Calin, M 2003)

6.2 Masonry
It is certain that being a good estimator requires knowledge and skills acquired through practice and experience. Particularly in masonry estimation, a good estimator needs to be well organized and proficient informa本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。