Mix cement - instructions for quick mixing

• Use as a binder
• Stirring in the pan by hand
  • Step by step instructions
• Mix by hand on a tarpaulin
• Mixing with stirrers
• Mixing with concrete mixer
• Production of plaster in the plastering machine
• Mortar and concrete recipes
  • "Basic recipes" when self-mixing
  • A basic recipe for concrete

Cement is an important binder used for concretes and mortars. The correct mixing of all cement-based products is important, because it depends on the strength of the later product. How to properly and professionally mix cement products by hand, with the mixer or with the stir bar is explained in our easy-to-understand instructions.

For all cement-based products (cement mortar, concrete), it is not only important to precisely observe all mixing ratios. It also depends on the correct order and the correct procedure for mixing. Mixing can be done with different devices and also by hand. For every type of mixing you have to observe special procedures and procedures. When using cement-based finished products, one usually has some significant advantages over self-mixing. You can see how the self-mixing works exactly in the following instructions.

Use as a binder

Cement is used exclusively as a binder. It is not a building material in itself, but is mixed with other materials to obtain a workable building material. Mortars are primarily made of cement and sand and, if necessary, an addition of lime (lime-cement mortar). For concrete gravel in each case standardized grain and so-called Portland cement is used. Plasters, such as cement plaster also belong to the mortar (technical term: plaster mortar) and are therefore produced with the same basic recipe.

Special types of cement

Portland cement is burned with particularly high temperatures, and also contains limestone. Trass cement contains trass (a special stone) and is more waterproof than other types of cement, showing less efflorescence. Alumina cements have a higher aluminum , only approved for non-structural structures. Fast Cement is mostly a mixture of Portland and Alumina Cement. He binds very fast. The properties of each type of cement must be taken into account in the case of mixing ratios and during subsequent processing. The DIN takes into account a total of 28 different types of cement.

aggregates

All mortars and concretes may contain numerous substances, including pozzolans, blastfurnace slag, fly ash, gypsum and limestone. Synthetic resins, fibers or color pigments can also be added. In contrast, additives include all property-modifying substances (longer processability, faster curing, better flow properties, air entrainment agents). They are often mixed in finished cements.

Bonding - the process

The curing does not take place by drying, but by a complex chemical reaction. In connection with water arise insoluble, fine calcium silicate needles, which are interlocked with each other, and provide the strength. Cement products can therefore even cure under water (so-called underwater concrete).

For the chemical reaction, the amount of water within the concrete or mortar is particularly important as it influences the course of the reaction. It is therefore always necessary to pay close attention to the so-called water-cement value (TM value).

WZ-value

The so-called TM value (sometimes also w / c value) indicates the ratio between the amount of water and dry matter. For the calculation of the tool value, the mass of the water used and the mass of the cement are used. The mass of aggregates (and also of the concrete admixtures) must be included, but not the mass of merely modifying admixtures.

The tool value is of crucial importance for the later strength of the cement-bound building material. Therefore, even when using ready mixes, the quantities of water must be kept very precisely, otherwise the strength class stated on the package will not be reached.

In the usual mortars and concretes used today, the TM values ​​of the mixtures are usually around 0.40, for reinforced concrete, depending on the type of concrete 0.45 - 0.75. The closer you get to the 0.40, the better the strength in general. Individual concretes also have TM values ​​of only 0.20. The optimum tool value must be specially calculated for each mixture.

Too much water

If too much water is added, after the reaction has ended (setting), so-called excess water remains in the mixture. The excess water takes up space within the building material and, after its evaporation, leaves behind cavities which impair the strength. In addition, the sensitivity to frost and shrinking increase.

Not enough water

With too little water can not cure the entire cement . This also affects the strength. If the mixture only hardens at some points due to water penetration, high internal tensions can occur in the finished product, resulting in an increase in volume in some areas and thus in deep cracks and damage to the concrete or mortar.

In order that the reaction with the exactly measured amount of water can actually take place in the desired manner, in addition to the correct amount and a precisely prescribed mixing is required. You can find out how to do this in the following instructions.

Overall, there are five ways to mix all cementitious products (including concrete).

• Stirring in the pan by hand
• Mix by hand on a tarpaulin
• Mixing with stirrers
• Mixing with concrete mixer
• Production of plaster in the plastering machine

The rules apply equally to the mixing of concrete and mortar. The manual mixing of concrete (depending on the type of concrete) but even with small quantities require a lot of effort.

Stirring in the pan by hand

For mixing is best a special mortar trough. Rectangular, as large as possible tubs are usually easier to handle and often lead to a better mixing result, especially if you are still untrained.

For mixing you need a spade. He should not be too tall so you can hold him well in his hand.

Step by step instructions

Step 1 - When making the mix yourself, first put the sand evenly in the pan. Then you distribute the cement (or the lime-cement mixture) evenly in small heaps. If you use dry mortar, you do not need sand as a substrate. You can then put the same small piles of dry mortar in the tub. Make a small dip in each of the piles.

Step 2 - Accurately measure and supply the required amount of water. The water may not be added at once, but only in small portions. Usually, if you use a sack of ready-to-use mix, you add the water by gallons. If you make smaller quantities, reduce the amount of water for the individual addition accordingly.

Step 3 - Add one liter of water (or less, with less amount of grout or concrete) to the pits. Then start mixing: use the spade to push a small part of the moistened pile forward. Then push the pushed forward heap back part by part back to its original place, thoroughly mix the heaps with the tip of the spade. Repeat with each heap until it is evenly moistened.

Step 4 - Make a small well again on each heap, pour in the next liter of water, and start again from step 3. Repeat all until the water provided is exhausted.

Step 5 - Finally, from the edge to the middle, thoroughly re-mix the entire pan with the tip of the spade. You should have received a uniformly shiny, earth-moist mixture. Make sure that the moisture level is uniform throughout the mixture.

Even with practice and experience, stirring in this way is quite exhausting and a real endurance exercise. However, if you do not use ready mixes, but mix the individual ingredients yourself, this is still the best way to get a uniformly mixed concrete or cement mortar.

Tip: If you want to stir very small quantities, and use a small tub, you can also do the mixing well with a trowel (triangular). Proceed in the same way as described above.

Mix by hand on a tarpaulin

Mixing on a tarpaulin works the same way as mixing in the tub described earlier. You can use the same guide. On a tarpaulin, you can also mix a little larger quantities if necessary.

Always make sure that you use a clean tarpaulin that is free from contamination. Under no circumstances should earth enter the mixture from the surrounding soil. When mixing slightly larger quantities on the tarpaulin, you usually have to work quickly. Then place the finished concrete or mortar in suitable buckets.

Mixing with stirrers

Especially when working with dry mortar or finished concrete mixes, agitators have proven to work for smaller quantities. However, they should not be used for the drilling machine for the stirring of paint or the mixing of rolling plaster.

For the mixing of mortar and especially concrete, a professional mortar stirrer is essential. Most mortars are easy to mix with concrete, which is often more difficult with concrete. Depending on the type of concrete, you need very powerful equipment for smaller quantities.

Always work in a mortar trough and always from the edge to the middle. Always fill the tub so well that you can still mix well with the mixer. A completely uniform mixing is absolutely necessary!

In this case too, gradually add the water, otherwise the mixing will not be uniform. At the end, always check the consistency and uniform moisture penetration before continuing to process the concrete or mortar.

Depending on their performance, stirrers can be purchased in various price ranges, but can often be lent to hardware stores.

Mixing with concrete mixer

For medium to large quantities, the concrete mixer is the most suitable for mixing. Always pay attention to the order of addition and always measure as accurately as possible.

Basic rule: Always add two thirds of water as first!

Then, add the gravel and then the cement mixture, then the rest of the water you need (referred to here as aggregate water or mixing water).

If you use ready-to-use dry products, simply add the dry mix after the first addition of water (two-thirds of the mixing water!), Then slowly add the rest of the water gradually.

The concrete mixer should run for about three to four minutes. Too long mixing endangers but also the subsequent stability of the concrete, such as an insufficient mix. It takes a bit of feeling and experience to see when the concrete is "done through".

Production of plaster in the plastering machine

Plaster mortars can also be processed automatically today (spray plaster method). The mortars used for this purpose have special admixtures which improve their flow properties and render the plaster mortar ready for spraying (machine-friendly means in technical language).

As each type of cleaning machine requires slightly different operation and feeding, you should always work according to the instructions in the operating book. Of course, you may only use suitable mortar for processing in the plastering machine.

Mortar and concrete recipes

Normally you are always on the safe side with finished goods. Unlike self-blending, the quality and strength of the final product is normalized when the instructions are carefully followed. When self-mixing you can always make a conditionally reliable statement about the subsequent strength even with very careful measurement. In addition, finished products often contain added additives that often make processing much easier and easier after mixing and ensure balanced properties. The cost savings through self-mixing is negligible compared to finished products.

"Basic recipes" when self-mixing

• Mortar:
  • 4 parts sand
  • 1 part cement
  • Addition of water: approx. ½ kilo of water per kg of cement
• Lime cement mortar regular:
  • 8 parts sand
  • 1 part cement
  • 2 parts of hydrated lime
  • Addition of water: approx. ½ kilo of water per kg of dry matter (lime + cement)
• Lime-cement mortar higher strength:
  • 6 parts sand
  • 1 part cement
  • 1 part hydrated lime

The latter mixture is recommended for most applications. Instead of sand, rocks with a maximum grain size of up to 4 mm can be used, but the grain size always changes the characteristics slightly. Pure lime mortar is actually only suitable for a few purposes, it should therefore be better to use as a home improvement.

A basic recipe for concrete

• 40 kg gravel, grain size 0/16
• 10 kg Portland cement PC 35
• 5 liters of water

This concrete can be used for most smaller foundations or similar applications and has sufficient strength. Please note, however, that special concrete properties and standardized strengths are required for certain applications (concrete strength classes according to DIN). These can only be reliably achieved with certified dry goods or with ready-mixed concrete!

Tips for quick readers

• Cement products (mortars and concretes) are best used as standardized dry finished products
• Self-mixing offers few advantages, but many disadvantages compared to dry finished goods
• Always observe the specified amount of water!
• Never change consistency (!) By changing the amount of water
• Mixtures must always be completely moistened
• Add water gradually in small quantities
• always observe the sequence in the concrete mixer
• observe the required and prescribed concrete or mortar quality for all construction projects