Concrete - 14070_103

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and as a check to determine if sufficient materials are available to constructor complete a project. In general, the term  bulk material  refers  to  concrete,  bituminous paving materials, and mineral products, such as sand, gravel, or rock. A few examples of estimating these materials  are  described  below. Concrete Estimating the amount of concrete required for a project consists of determining the volume (in cubic yards or, in many locations outside the United States, in cubic meters) of the spaces that will be occupied by the concrete. As an example, let’s look at figure 5-2. This figure   shows   the   foundation   plan   and   a   typical foundation detail for a small 20 foot by 32 foot building. As shown in the detail, the foundation is continuous and the floor is a 4-inch-thick concrete slab. Our task is to determine the amount of concrete that will be required for the foundation and slab. Since in any concrete job a certain amount of concrete will be unavoidably lost during  placement,  we  will  include  a  10-percent  waste factor. You can find this waste factor listed in the P-405. Although  we  could  proceed  in  various  ways  to estimate the amount of concrete that is required, an easy method is tabulated as follows: Foundation  wall: (32.00 ft x .67 ft x 2 fi) x 2 = 85.76 cu ft (18.67 ft x .67 ft x 2 ft) x 2 = 50.04 cu ft Footing: (33.33 ft x 2 ft x 1 ft) x 2 = 133.032 cu ft (17.33 ft x 2 ft x 1 ft) x 2 = 69.32 cu ft Slab: 18.67 ft x 30.67 ft x .33 ft = 188.96 cu ft 527.40 cu ft x 1.10 (10% waste) 580.14 cu ft = 21 cu yd From the above tabulation, you can see that separate estimates  were  prepared  for  the  foundation  wall, footing,  and  slab.  You  can  also  see  that  both  the foundation wall and the footing were further subdivided based  on  the  length  and  width  of  the  building;  for example,  the  foundation  wall  consists  of  two  walls measuring 32 feet long and two measuring 18 feet 8 inches  long  (allowing  for  overlap  at  the  foundation corners).  Then,  the  separate  estimates  were  added together, the waste factor was applied, and the final cubic feet of concrete was converted to cubic yards. Now  let’s  see  how  much  compacted  fill  will  be required for this job. For this example, we will assume that the project specifications call for sand to be used as the fill material. Figure 5-2 shows that the fill material is to be 8 inches thick after compaction. Therefore, the volume of the  compacted  fill  is  383.65  cubic  feet.  However,  from your  knowledge  of  soils,  you  know  that  compacted  sand occupies less volume than loose sand. Since the sand for this project will be delivered to the jobsite in a loose condition,   a   compaction   factor   must   be   applied. NAVFAC P-405 lists compaction factors for various materials. For sand, the compaction factor listed is 1.17. So, the total amount of sand required for this project is 383.65 x 1.17=448.87 cubic feet, or 16.6 cubic yards. Again, however, we know that a certain amount of sand will be wasted. So, let’s increase the total by 10 percent. Now we need approximately 18 cubic yards of sand for the job. Bituminous  Paving Although  not  always,  most  bituminous  paving projects  that  are  accomplished  by  the  Seabees  use hot-mixed bituminous concrete that is purchased from a central plant. In this case, the job of estimating consists of determining the compacted volume, in cubic feet, of the pavement. This volume is then multiplied by the unit weight of the mix, in pounds per cubic foot (pcf), and the final result is converted to tons of mix required. An equation for determining the required tons of mix can be  expressed  as  follows: Tons of mix = L  x  W  x  T  x  U  W 12  x  2000 Where: L  = W  = T  = UW = Length of paved area in feet Width of paved area in feet Compacted thickness of the pavement in inches Unit weight of the mix in pounds per cubic foot To illustrate the use of this formula, let’s assume that   we   are   estimating   a   2-inch-thick   hot-mix 5-7

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