Concrete - cement:sand:gravel

The application calculates the exact proportions, volume and weight of cement, water, sand and gravel for making concrete with desired characteristics *:
- compressive firmness - classes B7,5..B30 or mark M100..M400
- Mobility (density) of the concrete mix - P1..P5
- Frost-resistance - F50..F1000
- Watertightness - W2..W20
* classes and marks are given in accordance with russian standards

Proportions can be calculated for the concrete on the basis of:
- Gravel and sand
- Only sand
- Ready mix of sand and gravel (S/G mix)

The calculation considers the possibility of using waterreduction additives.

While using the app you will be asked to specify the characteristics of cement, sand and gravel. The basic values (cement mark, empty space between grains of gravel and sand) are necessary to specify - otherwise the calculation accuracy will not be high. But you can leave the default values for other features. The help is offered to specify each feature, which says how to find out or calculate the required value.

Finally, you will get proportions (eg, 1:0,5:1,5:3), liters and kilograms required to make desirable concrete. You can recalculate the liters and kilograms, for example, to bring them to the recommended 40 liters of concrete mix in a common mixer.

The application will also check whether desired frost-resistance and watertightness are achievable with given values of the components. It will suggest what kind of additional additives (airinvolving, waterproofing, sealing) should be introduced in the concrete mix if required.

You can get the cost of 1 m3 (1000 liters) of concrete also by specifing the cost of cement, gravel and sand in your region


THE LACK OF GUARANTIES AND THE FINAL SELECTION OF THE CONCRETE PROPORTIONS
The application uses the algorithms of calculation proportions of concrete components suggested in the books of the Soviet and Russian concrete scientists - Dvorkin, Sizov, Izotov, Gorchakov, Davidson.

This algorithms are the theoretical basis for the initial selection of the proportions of components only. It is necessary to assess the mobility (thickness) of the concrete mix after making trial mixture. If the mixture has turned too liquid - reduce the amount of cement and water by 5%. If the mixture is too thick - increase cement and water by 5%.

The application offers proportions of components for desired firmness with reliability of 95% and coefficient of variation of firmness of 13,5%. This means a large stock of safety. However, in order to be assured in terms of firmness, frost-resistance and watertightness, it is necessary to make concrete samples and test them in the laboratory. Thereafter, if necessary, adjust the proportions of the components. Application author does not give a 100% guarantee and is not responsible for difference between the actual characteristics of concrete designs and those, which were specified in the app. The application should be used for searching of initial proportions only.


ALGORITHMS USED TO CALCULATE PROPROTIONS
Concrete proportions calculation is devided into two actions. Firstly, the water-cement ratio required to obtain the desired concrete firmness is calculated. Secondly, the water demand of concrete mix and the ratio of filling the empty space between the gravel grains by sand and cement paste is determined considering desired mobility level of the mixture. The higher the required mobility, the greater the volumes of sand, water and cement.

In case of concrete prepared on the basis of sand (without gravel) the ratio of filling the empty space between the sand grains by cement paste is determined.

Calculation of concrete prepared on the basis of ready sand and gravel mix combines both of these algorithms. However, since the application is requesting a few characteristics of S/G mix, the calculation of such type of concrete is the least accurate. So it is not recommended to use S/G mix in the most cases.