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When purchasing building materials, it is important to accurately calculate their quantity. Both lack and excess do not bring joy. It is generally believed that “interception” is better than “undercoverage”, but not in the case of cement. This material cannot be stored for a long time and therefore it is worthwhile to accurately calculate the required amount. How much cement is needed per 1 m³ of concrete can be determined in kilograms and bags. In principle, it is better to know both, because the packaging can be different.
How much cement is needed per cube of concrete
Cement is the type of building material that should not be stored for a long time. Even if it is kept warm and dry, after three months it loses 20% of its strength, after six months – 30%, and after a year – 50%. So for critical areas it is better not to use stale. To be sure of “freshness”, it is better to purchase in the original packaging, on which the date of production is affixed. If you immediately put it into action, it can be two months ago. If you also have it for some time, fresher is better.
In order not to store, you need to know how much cement is in a cube of concrete. For this, there are tables that show the consumption of cement in kilograms per cubic meter of mortar. The most popular are Portland cement grades M400 (new designation CEM I 32,5N) and M500 (new designation CEM I 42,5N). They are used to prepare concrete up to M500 grades. For the less durable, you can use the cheaper M300.
Based on these data, it is easy to calculate how much cement is required for the amount of concrete you require. For example, 5,7 cubes are required for pouring the foundation. The concrete will be M300, we will make it from PC400. One cubic meter is 290 kg. This means that 5,7 m³ will go for everything * 290 kg / m³ = 1653 kg.
The amount of cement per 1 m³ of concrete, depending on the hardness
Above is the average table. In general, the specific amount of binder depends on its quality, aggregates (sand and gravel), and also on the required stiffness of the concrete solution. At factories, a specific ratio is selected for each delivery of cement, sand or gravel. They brought another batch of sand – tests are being carried out. Received a new binder – all over again. Anyway, that’s how it should be. For meticulous house builders, we present a table that indicates the consumption of cement per cubic meter of mortar, depending on the required stiffness (fluidity) of the composition.
Also keep in mind that the use of additives that increase the workability of the mortar (fluidity) allows you to put less binder. But it is better not to reduce it “by eye”. If you decide to add the same “Fairy”, put the cement at the rate. Additive, by the way, too. Because with an excess, the concrete simply will not set and even after a month it will be soft.
How many bags of cement in a cube of concrete
Cement is sold in bags and therefore it is better to know how many bags of cement per 1 cubic meter of concrete are required. There are also reference tables for this, but you can calculate it yourself. Counting is more accurate than using tables. Firstly, there are bags of 40 kg and 50 kg. This is a standard container. But there are also 25 kg and such packaging is also a lot. The table shows how many bags of cement are in the concrete of the most popular brands.
In addition, it is not enough when a whole number of bags is required per cubic meter. For example, concrete M150 requires 215 kg of PC400. Let’s calculate the amount of binder in kilograms that will be needed to make 4,6 cubic meters of concrete. 4,6 m³ * 215 kg = 989 kg. Now we count the number of bags of cement that will need to be purchased:
- 25 kg each – 898 kg / 25 kg = 35,92 pcs. That is, you will need 36 pieces of 25 kg each;
- in a package of 40 kg: 898 kg / 40 kg = 22,45 pieces, round up, it turns out that you will need to buy 23 forty kilogram bags;
- 50 kg each – 898 kg / 50 kg = 17,96 pcs; bags of 50 kg, 18 pieces are needed.
Now, how many bags of cement are needed for 1 m³ of concrete, we will calculate according to the second table. Let’s take the same example – 4,6 cubic meters of concrete M150 from cement M400. According to the table, one cubic meter requires 4,3 bags of 50 kg and 5,4 bags of 40 kg. In total, the entire volume will go:
- 40 kg bags: 4,6 cubes * 5,4 pcs = 24,84 pcs or 25 bags.
- in packing of 50 kg: 4,6 cubes * 4,3 pieces = 19,78 pieces or 20 pieces.
The table does not indicate the number of 25 kg bags. You can calculate it yourself – you need to divide the number of 50 kg bags by 2.