Estimating Sheet

# How to analyze concrete block work perfectly

Construction Software In this construction video tutorial, some useful guidelines are provided to make analysis of concrete block work by applying the following steps :-

1) Determine the total Gross block work. ( in cu.m or in cu.ft )
2) Identify mortar. (here, mortar is taken as 12% of block work)
3) Identify total net block work.
Net block work = gross block work - mortar
4) Define number of blocks.
No’s of blocks = (net block work)/( volume of one block)

Note: For volume of a single block, no standard size of concrete block exist. It can be selected from specification. In this video, the dimension of block is taken as 16 x 6 x 8 inches.

5) Determine cement and sand for mortar mix.

In this video solution is given on the following problem :-

Prob: Analyze a block wall where mortar is 12% of block wall with proportion 1:3 and size of blocks is 16” x 6” x 8”.
The length of the block wall is taken as 15 ft and the height is taken as 30 ft. The density of the wall is 6”

Total block work is determined by multiplying length, thickness and height i.e. length x thickness x height
Total block work = 30 x 0.5 x 15 = 225 ft3
Total mortar = 12% of total block work i.e. 12%/100 x 225 = 27 ft3

Net block work = gross block work – mortar = 225 – 27 = 198 ft3
Numbers of blocks = Net block work/volume of one block

= 198/0.4489 ft3 (16” = 1.34 ft, 6” = 0.5 ft, 8” = 0.67 ft) = 441.0781911 = 441 numbers

Volume of cement and sand will be determined as follow :-
Total weight mortar = 27 ft3, it should be converted to dry mortar by multiplying it with 1.27
i.e. 27 ft3 x 1.27 = 34.29 ft3
We know, the proportion of cement and sand in mortar = 1:3 (cement : sand)
By summing up, we get = 1+3 = 4
The volume of cement = 1/4x34.29 = 8.5725 cft, to convert it to bags divide it with 1.25 (volume of one cement bag) i.e. 8.5725/1.25 = 6.858 bags or 7 bags approx.
The volume of sand = 8.5725 x 3 = 25.71 cft (as sand is 3 time of cement volume)

Video Source: SL Khan 