Preparation of concrete technology and proportions

construction almost always involves the use of concrete, namely the concrete mix, which is an artificial stone.With the construction of the house, garden greenhouses, fences necessarily poured foundation.concrete is also used to make the blind area, Water supply without even footpaths in suburban areas.Wide range of applications speaks of concrete universality, as a building material.

Concrete is made in the production or personally mixed the main constituent components.Mixing is carried out in wooden or metal boxes, tubs, mobile concrete mixers.The latter provide the highest quality and productivity of stirring a mixture of components (gravel, sand, cement, water).In the manufacture of concrete with their hands is very important to avoid getting into a mixture of impurities, as well as to comply with the technology and take into account the proportions (dosage).

Concrete, classification

Classification	Weight, kg / m3	Scope of use
particularly heavy	Over 2,500	power plant NPP
Heavy	From1800 to 2500	Manufacturing of foundations, structures of reinforced concrete, and other construction work
easy	from 500 to 1800	Production of floors, panels, wall
blocks particularly easy	Less than 500	insulation of facades of buildings

also developed specialized concrete, characterized by the presence of specific impurities, improve certain characteristics (thermal conductivity, strength, density, etc.).For example:

• refractory (resistant to heat up to 1000 degrees);
• road (especially strong in bending and morozostoustoychiv);
• hydraulic engineering (highly resistant to corrosion, waterproof, high-density);
• airfield concrete and other special purposes.

main components of the concrete mix

If you are thinking about a handwritten concrete preparation, it is worth considering not only the number of used "ingredients" for a mixture, but also their quality, which affect the characteristics of the finished basement.

Sand

To prepare a concrete mix, using sand with a grain size from 1.2 to 3.5 mm.Too fine sand is not suitable for the manufacture of concrete.When choosing sand pay attention to its purity - the presence of inclusions of clay, silt, less than 5%.Otherwise concrete loses its strength due to the high fat content, which gives clay, respectively crumble quickly.

How to check the quality of the sand?Suffice it to pour into a container with little running water and stir.The high quality of say clean or slightly muddy water.If the liquid instantly turns the color of clay, or there is a deposit - sand is not suitable for the manufacture of concrete.

Crushed gravel

next component of concrete - crushed stone (gravel, granite gravel, scrap brick, concrete block, etc.).It is chosen with a particle size of from 1 to 8 centimeters (self concrete production - from 1 to 2 centimeters), checking for purity and absence of debris clay impurities.The use of larger fractions of crushed stone will lead to the loss of the foundation of proper strength and at the same time to the disadvantage of the operations.

Cement

addition of gravel and sand in the concrete is required to add cement.At the same time the consumption of cement depends on its brand.The amount of cement is calculated strictly on the proportions, the rule "the more the better" does not affect the quality of the future concrete.

Cement is:

• Portland cement - is used for all types of construction, as well as for filling the basement, ideal for the independent preparation of concrete;
• slag - differs from the previous low frost resistance and increased moisture resistance;
• pozzolan Portland cement - used in the construction of underground and underwater structures due to the high moisture resistance;
• other types of cement with special additives, allowing the mixture to harden more quickly, which reduces the period of maturation of concrete up to 14 days.

Water Water is necessary to use a warm and clean, free of impurities oils, petroleum products, paints, enamels.

Of course, it is difficult to guarantee absolute purity, especially in the preparation of their own concrete.It is also quite difficult to reconcile in practice absolutely exact proportions of crushed stone, sand and cement to the liter or kilogram.In addition, should take into account that the cement over time loses some of its properties.Even after months of storage, he will lose a tenth of its properties, respectively cement maar decreases.For 6 months of storage cement loses up to one third of all its properties.

marking of concrete and cement

cement brand characterizes its compressive strength (kilograms per square centimeter concrete cube with a side of 20 cm in 28 days after manufacture).If there are additional cement admixture, the labeling indicates additional letters (for example, M (PC) 400 - D20).

most commonly used in the preparation of cement concrete - M350 and M500 .

concrete Brand (M50 - M1000) also reflects its average characteristics.In this concrete marking it depends on the amount of cement used in a mix.The marking of the concrete also show his class - B1 - B60, which is a measure of strength.

How to calculate the volume of concrete and learn

immediately the amount of the concrete is measured in cubic meters. Calculate the amount of concrete for the foundation not difficult.

To calculate the volume of concrete and formwork, multiply its depth to width and length.This result is the number of the desired concrete pouring.

To calculate the proportion of the components (cement, sand, water) to prepare concrete , should refer to the following "recipe".

If you want to prepare 10 cubic meters of concrete, and is used for its manufacture cement brand M500, you should take 1 part cement, 2 parts water, 4 pieces of rubble.From these seven parts of 10 cubic meters of ready-mixed concrete is made, then 10 ÷ 7 = 1.42 m3.This volume is necessary for each of the pieces of concrete components.Accordingly:

1. sand 1.42 m3 × 2 pieces = 2,84 m3;
2. one part cement, 1.42 m3;
3. rubble of the 1.42 m3 4 × 4 = 5.68 m3.

Approximate weight materials (kg / 1 m3) of cement - 1500, the sand - 1800, the rubble - 1400.

The optimum amount of water - half of the amount used for the preparation of cement concrete (in this case, ½ part).Larger amounts of water lead to a deterioration in the consistency of the mixture.

Mixing ratio concrete

When used for the preparation of cement concrete solution M400 and M500, the proportion of crushed stone, sand and cement will be as follows.

Concrete, brand	proportions of cement M400 (C), sand (D), gravel (W), kg - C: P: u	proportions of cement M500 (C), sand (D), gravel (w), kg - C: P: u	The amount of concrete from 10 liter M400 brand of cement, l	The amount of concrete from 10 liter M500 brand of cement, l
M100	1: 4,6: 7,0	1: 5,8: 8,1	78	90
M150	1: 3,5: 5,7	1: 4,5: 6,6	78	73
M200	1: 2,8: 4,8	1: 3,5: 5,6	54	62
M250	1: 2,1: 3,9	1: 2,6: 4,5	43	50
M300	1: 1,9: 3,7	1: 2,4: 4,3	41	47
M400	1: 1,9: 3,7	1: 1,6: 3,2	31	36
M450	1: 1,1: 2,5	1: 1,4: 2,9	29	32

After a number of gravel, sand, cement and water became knownand prepared, should prepare a mixture.For this purpose, the mixer adds a small amount of water, and then fall asleep cement mix, adding sand, stir again, achieving uniformity of the mass without lumps.Only now you can add gravel and the remaining amount of water.The mixture immediately use for construction purposes.

concrete Maturation and set them to the proper strength

Traditionally, all work with concrete is carried out in the warm period of the year when air temperatures above zero.In this case, the water reacts with the cement composition and solidified qualitatively.When pouring concrete in cold weather, the water can turn into ice, which will cause loss of strength of the bud and its destruction from within.

«grasp" the concrete for 12 hours to harden during the first week, two weeks after concrete is gaining almost 80% of its strength, and fully becomes ready for operation only after a month (assuming an ambient temperature of about 20 ° C).If you are used to fill special forms bystrozatverdevayuschih concrete, the term "mature" may be shorter.

Video - Concrete Preparation