The absolute volume method is a technique used to calculate the quantities of materials required for concrete production, including cement, sand, and aggregates, based on specific mix proportions such as 1:2:4 for M15, 1:1.5:3 for M20, and 1:1:2 for M25. The principle behind this method is that the volume of fully compacted concrete is equal to the absolute volume of all the materials used in the concrete mixture, including cement, sand, coarse aggregates, and water. By using this method, the exact volumes of each material needed can be determined for producing the desired quantity of concrete with the specified mix proportions.
To calculate the volume of concrete required for a concrete structure, the volumes of each structural member or part of members must be summed up. The formula for calculating the volume of a rectangular cross-sectional member is length multiplied by width multiplied by height (or depth or thickness). Different formulas may be used for different cross-sectional shapes of members.
The calculation of material quantities for concrete involves various factors such as the absolute volume of fully compacted fresh concrete (Vc), mass of water (W), mass of cement (C), mass of fine aggregates (Fa), and mass of coarse aggregates (Ca). Additionally, specific gravities of cement (Sc), fine aggregates (Sfa), and coarse aggregates (Sca) are considered in this method of calculation. The air content is ignored for simplicity. This approach takes into account the mix proportions from design mix or nominal mixes to ensure the desired structural strength and durability of the concrete. Let’s understand this calculation through an example.
Calculating Quantities of Materials for per cubic meter or cubic feet or cubic yards concrete
The given concrete mix proportion is 1:1.5:3, where 1 part is cement, 1.5 parts are fine aggregates (sand), and 3 parts are coarse aggregates (with a maximum size of 20mm). The water-cement ratio for mixing the concrete is taken as 0.45.
The bulk densities of the materials per cubic meter, cubic feet, and cubic yards are as follows:
- Cement: 1500 kg/m3 = 93.642 lb/ft3 = 2528.332 lb/cubic yards
- Sand: 1700 kg/m3 = 105 lb/ft3 = 2865.443 lb/cubic yards
- Coarse aggregates: 1650 kg/m3 = 103 lb/ft3 = 2781.166 lb/cubic yards
The specific gravities of the concrete materials are as follows:
- Cement: 3.15
- Sand: 2.6
- Coarse aggregates: 2.6
The percentage of entrained air assumed in the concrete mix is 2%.
The mix proportion of 1:1.5:3 by dry volume of materials can be expressed in terms of masses as:
- Cement: 1 x 1500 = 1500
- Sand: 1.5 x 1700 = 2550
- Coarse aggregate: 3 x 1650 = 4950
Therefore, the ratio of masses of these materials with respect to cement will be as follows.
In the given context, the mass proportions of concrete materials are provided as a ratio of 1 : 1.7 : 3.3, representing the ratios of cement, water, and aggregate (such as sand and gravel) respectively. The water cement ratio is specified as 0.45, which indicates the amount of water relative to the amount of cement in the concrete mix.
To calculate the volume of concrete that can be produced with one bag of cement weighing 50 kg, we can use the concept of absolute volume. The absolute volume of concrete is the total volume of all the individual ingredients in the mix, expressed as a fraction of the volume of solid cement. For a given water cement ratio, the absolute volume of concrete can be calculated using the given mass proportions of concrete materials.
Using the given mass proportions of 1 : 1.7 : 3.3 for cement, water, and aggregate respectively, and the water cement ratio of 0.45, we can calculate the absolute volume of concrete that can be produced with one bag of cement (50 kg). The absolute volume of concrete is obtained by multiplying the mass of each ingredient with its respective volume per unit mass (or specific volume), and summing them up.
Finally, the volume of concrete that can be produced with one bag of cement (50 kg) can be determined using the calculated absolute volume of concrete. This information helps in estimating the amount of concrete that can be produced with a given quantity of cement for the specified mass proportions of concrete materials.
Based on the given information, the proportion of mix considered allows for the production of 0.1345 m3 of concrete with one bag of cement weighing 50 kg. An entrained air percentage of 2% is taken into account, resulting in an actual volume of concrete for 1 cubic meter of compacted concrete construction of 0.98 m3. As a result, the quantity of cement required for 1 cubic meter of concrete can be calculated as 0.98/0.1345, which equals 7.29 bags of cement. This translates to a weight of cement required of 7.29 x 50 = 364.5 kg.
Similarly, the weight of fine aggregate (sand) needed can be calculated as 1.5 times the weight of cement, which results in 1.5 x 364.5 = 546.75 kg. The weight of coarse aggregate required is determined by multiplying the weight of cement by a factor of 3, resulting in 3 x 364.5 = 1093.5 kg.
Concrete Calculator: Calculate Quantities of Materials for Concrete
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Calculation Results: Quantities of Materials
In construction, the volume of concrete can be measured in various units such as cubic meters, yards, cubic feet, and pounds. Similarly, the quantity of cement can be measured in kilograms, bags of 50 kilograms, or pounds. The quantity of sand can be measured in kilograms, cubic meters, yards, cubic feet, and pounds, while the quantity of coarse aggregates can also be measured in kilograms, cubic meters, yards, cubic feet, and pounds. Additionally, the quantity of water can be measured in liters or gallons.