QUANTITY METHOD

How to Calculate Cement Sand Aggregate in Concrete?

Question

Hi Friends please tell me about cement concrete calculation.
Volume of concrete = 4000 ft3
Ratio of concrete = 1:2:4
Reinforcement Steel Quantity = 3 ton

1. 1 ft3 = 0.02832 m3

   So, 4000 ft3 = 4000 x 0.02832 = 113.28 m3.

   Now you can get the QUANTITIES OF MATERIALS PER CUBIC METER OF CONCRETE as follow:

   For Concrete Mix Proportion 1: 2: 4, materials per m3 are as follows:

   Cement Quantity = 310 kg (6.2 bags)

   Sand = 0.434 m3

   Coarse Aggregate = 0.868 m3

   Therefore, for 4000 ft3 (113.28 m3) will be as follows:

   Cement = 113.28 x 310 = 35116.8 kg = 702.34 bags

   Sand = 113.28 x 0.434 = 49.16352 m3  = 1736 ft3

   Coarse Aggregates = 98.32704 m3 = 3472 ft3
2. Today we will see how to prepare rate analysis for Reinforced Concrete (RCC) work. First step to rate analysis is the estimation of labour, materials, equipments and miscellaneous items for particular quantity of reinforced concrete.
   The second step is to determine the component of structure for which the RCC rate analysis is required, as the quantity of reinforcement steel varies with slabs, beams, columns, foundation, RCC Roads etc., though the quantity of other materials like sand, coarse aggregate and cement remain the same with the same mix design (mix proportion) of concrete. Labour rates for reinforcement work changes with type of structural component as the quantity of reinforcement steel changes. The Quantity of materials like sand, cement and coarse aggregates vary with mix design such as M15 (1:2:4), M20 (1:1.5:3), M25, M30 etc..
   
   Here we will see the rate analysis for 1m3 of reinforced concrete.

   Data required for RCC Rate Analysis:

   1. Estimation of materials:
   Material estimation include sand, cement, coarse aggregate and steel for a particular mix design. Let us consider a mix design of 1:1.5:3 for our estimation practice. The dry volume of total materials required is considered as 1.54 times the wet volume of concrete, due to voids present in sand and aggregates in dry stage. Therefore, for our calculation, we will consider the total volume of materials required as 1.54 m3 for 1 m3of wet concrete.
   a) Bags of cement required:
   Volume of cement required for 1m3 of Concrete =
   =0.28 m3
   Then number of bags of cement (volume of one bag of cement = 0.0347 m3)
   == 8.07 bags of cement.
   b) Volume of Sand required:
   Volume of sand required =  = 0.42 m3 of sand.
   c) Volume of Coarse Aggregate Required
   Volume of Coarse Aggregate == 0.84 m3 of coarse aggregates.
   d) Estimation of Reinforced Steel:
   Quantity of steel required depends on components of structure, i.e. slabs, beams, columns, foundations, roads etc. To estimate the steel required, there are two methods.
   First method is, when we have the drawing available, we can calculate the total weight of steel required divided by total volume of concrete for different components. This will give us the weight of reinforcement steel per cubic meter of concrete.
   Second method is assuming the percentage of reinforcement for different components. Following are the percentage of reinforcement steel generally required per different components. Its values can vary from structure to structure, and can be assumed from past experiences of similar structure.
   • For slabs = 1.0 % of concrete volume.
   • For Beam = 2 % concrete volume.
   • For column = 2.5 % of concrete volume.
   • For RCC Roads, 0.6% concrete volume.
   Lets take example of RCC Column, where reinforcement required is 2.5% of concrete volume, weight of steel required will be:
   =196.25 kg.
   2. Labour Requirement for 1m3 of RCC:
   Labours required are presented in terms of days required by particular labour to complete its work for the given quantity of concrete. Following are the various labours required:
   a) Mason: As per Standard Schedule of Rates and Analysis of Rates, One mason is required for 0.37 days.
   b) Labours: One Unskilled labours required for 3.5 days.
   c) Water carrier: One water carrier required for 1.39 days.
   d) Bar Bender: Bar bender requirement depends on weight of reinforcement. Lets consider one bar bender required for 100 kg of steel as for 1 day.
   e) Mixer Operator: One mixer operator required for 0.0714 days.
   f) Vibrator Operator: One vibrator operator required for 0.0714 days.
   3. Equipments and sundries:
   Equipment and other charges, such as water charges, miscellaneous items, tools and tackles etc can be assumed as some percentage of total cost of materials and labours. Lets say it as 7.5%.
   4. Contractor’s Profit:
   Contractor’s profit depends on place to place, organization to organization and work to work. It varies from 10 – 20%. For our case lets assume it as 15% of total cost of materials, labours and equipments.
   We have calculated the quantity of every item in above 1 – 3 steps. For rate analysis of RCC, we need to multiply each quantity with their rates to get the amount for every item of work. Rates vary from place to place and time to time. It is advisable to assume local rates or standard rates of the place.
   The sum total of all the four items above will give the rate or cost for 1m3 of concrete.
3. Quantity of materials such as cement, sand, coarse aggregates and water required per cubic meter of concrete  and mortar varies with the mix design of the concrete and mortar respectively. Following table gives the estimated quantity of materials required per cubic meter of mortar and concrete for various nominal mixes.

   NOMINAL MIX			WATER CEMENT RATIO	WATER PER 50KG BAG OF CEMENT	CEMENT		SAND (CUM)	CRUSHED STONES (CUM)
   CEMENT	F.A.	C.A.			BY WEIGHT (KG)	BY NUMBER OF BAGS
   1	1	–	0.25	12.5	1015	20.3	0.710	–
   1	1.5		0.28	14	815	16.3	0.855	–
   1	2	–	0.3	15	687	13.74	0.963	–
   1	2.5	–	0.35	17.5	585	11.7	1.023
   1	3	–	0.4	20	505	10.1	1.06	–
   1	4	–	0.53	26.5	395	7.9	1.106	–
   1	6	–	0.7	35	285	5.7	1.197	–
   1	8	–	0.9	45	220	4.4	1.232	–
   1	1	2	0.3	15	560	11.2	0.392	0.784
   1	2	2	0.42	21	430	8.6	0.602	0.602
   1	1.5	3	0.42	21	395	7.9	0.414	0.828
   1	1.66	3.33	0.48	24	363	7.26	0.419	0.838
   1	2	3	0.5	25	385	7.7	0.539	0.808
   1	2	3.5	0.53	26.5	330	6.6	0.462	0.808
   1	2	4	0.55	27.5	310	6.2	0.434	0.868
   1	2.5	3.5	0.57	28.5	305	6.1	0.534	0.748
   1	2.5	4	0.6	30	285	5.7	0.499	0.798
   1	3	4	0.65	32.5	265	5.3	0.556	0.742
   1	2.5	5	0.65	32.5	255	5.1	0.446	0.892
   1	3	5	0.69	34.5	240	4.8	0.504	0.84
   1	3	6	0.75	37.5	215	4.3	0.452	0.904
   1	4	8	0.95	47.5	165	3.3	0.462	0.924

   Notes:
   1. F.A.= Fine Aggregates, C.A.= Coarse Aggregates
   2. The table is based on assumption that the voids in sand and crushed stone are 40 and 45 percent respectively.
   3. Air content of 1 percent has been assumed.
   4. For gravel aggregates decrease cement by 5 percent, increase sand by 2 percent and coarse aggregate in proportion to fine aggregate in mix.
   4. No allowance has been made in the table for bulking of sand and wastage./>
4. QUANTITY OF CEMENT & SAND CALCULATION IN MORTAR
   Quantity of cement mortar is required for rate analysis of brickwork and plaster or estimation of masonry work for a building or structure. Cement mortar is used in various proportions, i.e. 1:1, 1:2, 1:3, 1:4, 1:6, 1:8 etc.
   Calculation of quantity of cement mortar in brickwork and plaster:
   For the calculation of cement mortar, let us assume that we use 1m3 of cement mortar. Procedure for calculation is:
   1. Calculate the dry volume of materials required for 1m3 cement mortar. Considering voids in sands, we assume that materials consists of 60% voids. That is, for 1m3 of wet cement mortar, 1.6m3 of materials are required.
   2. Now we calculate the volume of materials used in cement mortar based on its proportions.
   Let’s say, the proportion of cement and sand in mortar is 1:X, where X is the volume of sand required.
   Then, the volume of sand required for 1:X proportion of 1m3 cement mortar will be
   
   3. Volume of cement will be calculated as:
   
   Since the volume of 1 bag of cement is 0.0347 m3, so the number of bag of cement will be calculated as:
   
   
   Example:
   For cement mortar of 1:6, the quantity calculated will be as below:
   Sand quantity:
   
   Quantity of cement (in bags):
   Volume of cement = 
   There number of bags required =  = 6.58 bags.

5. How to Calculate Labor & Reinforcement for 1m3 RCC column Work in detail ?

6. 1. Column Design: Exm: Size of the column 0.450*0.450 mm

      Dead Load :Slab load+Live load+beam load+Stairs load+wall load

      Self load per meter :0.450*0.450*1=0.2025

      Column should be taken what story of building General use Per meter Ground &1st floor 1Mason,2Mazdoor ;2&3 floor 2Mason 3Mazdoor.

   METHODS OF REINFORCEMENT QUANTITY ESTIMATION IN RCC STRUCTURE

7. Estimation of Reinforcement Quantity in RCC Structure

   Estimation of steel reinforcement quantity is required for calculating cost of RCC structure along with other building materials as per construction drawing. Accurate quantities of the concrete and brickwork can be calculated from the layout drawings.

   If working drawings and schedules for the reinforcement are not available it is necessary to provide an estimate of the anticipated quantities. The quantities are normally described in accordance with the requirements of the Standard method of measurement of building works.

   In the case of reinforcement quantities the basic requirements are:

   1. Bar reinforcement should be described separately by steel type (e.g. mild or high-yield steel), diameter and weight and divided up according to:

   (a) Element of structure, e.g. foundations, slabs, walls, columns, etc., and

   (b) Bar ‘shape’, e.g. straight, bent or hooked; curved; links, stirrups and spacers.

   2. Fabric (mesh) reinforcement should be described separately by steel type, fabric type and area, divided up according to 1(a) and 1(b) above.

   

   Methods of Reinforcement Quantity Estimation

   There are different methods for estimating the quantities of reinforcement;, three methods of varying accuracy are:

   Method-1 for Reinforcement Estimation

   The simplest method is based on the type of structure and the volume of the reinforced concrete elements. Typical values are, for example:

   • Warehouses and similarly loaded and proportioned structures: 1 tonne of reinforcement per 105m3
   • Offices, shops, hotels: 1 tonne per 13.5m3
   • Residential, schools: 1 tonne per 15.05m3

   However, while this method is a useful check on the total estimated quantity it is the least accurate, and it requires considerable experience to break the tonnage down to Standard Method of Measurement requirements.

   Method-2 for Reinforcement Estimation

   Another method is to use factors that convert the steel areas obtained from the initial design calculations to weights, e.g. kg/M2 or kg/m as appropriate to the element.

   If the weights are divided into practical bar diameters and shapes, this method give a reasonably accurate assessment. The factors, however, do assume a degree of standardization both of structural form and detailing.

   This method is likely to be the most flexible and relatively precise in practice, as it is based on reinforcement requirements indicated by the initial design calculations.

   Method-3 for Reinforcement Estimation:

   For this method sketches are made for the ‘typical’ cases of elements and then weighted.

   This method has the advantages that:

   (a) The sketches are representative of the actual structure

   (b) The sketches include the intended form of detailing and distribution of main and secondary reinforcement

   (c) An allowance of additional steel for variations and holes may be made by inspection.

   This method can also be used to calibrate or check the factors described in method 2 as it takes account of individual detailing methods.

   When preparing the reinforcement estimate, the following items should be considered:

   (a) Laps and starter bars

   A reasonable allowance for normal laps in both main and distribution bars and for starter bars has shall be considered. It should however be checked if special lapping arrangements are used.

   (b) Architectural features

   The drawings should be looked at and sufficient allowance made for the reinforcement required for such ‘non-structural’ features.

   (c) Contingency

   A contingency of between 10% and 15% should be added to cater for some changes and for possible omissions.

Preparation of Bar Bending Schedule

Bar bending schedule (or schedule of bars) is a list of reinforcement bars, vis-à-vis, a given RCC work item, and is presented in a tabular form for easy visual reference. This table summarizes all the needed particulars of bars – diameter, shape of bending, length of each bent and straight portions, angles of bending, total length of each bar, and number of each type of bar. This information is a great help in preparing an estimate of quantities.

Figure 1 depicts the shape and proportions of hooks and bends in the reinforcement bars – these are standard proportions that are adhered to:

(a) Length of one hook = (4d ) + [(4d+ d )] – where, (4d+ d ) refers to the curved portion = 9d.

(b) The additional length (la) that is introduced in the simple, straight end-to-end length of a reinforcement bar due to being bent up at  say 30o to 60o, but it is generally 45o) = l1 – l2 = la

Where,

Fig: Hooks and bends in Reinforcement

Giving different values to  respectively), we get different values of la, as tabulated below:

Figure 2 presents the procedure to arrive at the length of hooks and the total length of a given steel reinforcement.

Fig: Typical Bar Bending Schedule

ESTIMATION METHODS OF BUILDING WORKS

ESTIMATION METHODS OF BUILDING WORKS

The estimation of building quantities like earth work, foundation concrete, brickwork in plinth and super structure etc., can be workout by any of following two methods:

a) Long wall – short wall method

b) Centre line method.

c) Partly centre line and short wall method.

a) Long wall-short wall method:

In this method, the wall along the length of room is considered to be long wall while the wall perpendicular to long wall is said to be short wall. To get the length of long wall or short wall, calculate first the centre line lengths of individual walls. Then the length of long wall, (out to out) may be calculated after adding half breadth at each end to its centre line length. Thus the length of short wall measured into in and may be found by deducting half breadth from its centre line length at each end. The length of long wall usually decreases from earth work to brick work in super structure while the short wall increases. These lengths are multiplied by breadth and depth to get quantities.

b) Centre line method:

This method is suitable for walls of similar cross sections. Here the total centre line length is multiplied by breadth and depth of respective item to get the total quantity at a time. When cross walls or partitions or verandah walls join with main wall, the centre line length gets reduced by half of breadth for each junction. Such junction or joints are studied carefully while calculating total centre line length. The estimates prepared by this method are most accurate and quick.

c) Partly centre line and partly cross wall method:

This method is adopted when external (i.e., around the building) wall is of one thickness and the internal walls having different thicknesses. In such cases, centre line method is applied to external walls and long wall-short wall method is used to internal walls. This method suits for different thicknesses walls and different level of foundations. Because of this reason, all Engineering departments are practicing this method.