Sticking to the specific proportions when mixing the concrete mortar is a key factor, as it translates into the physical properties of the screed. The more water we use in the concrete mortar, the more fluid it will be, but at the same time, it will lose its strength after drying. The general rule is to add as little water as possible to the concrete mix, but use as much water as possible during its care. So what is a dry cement mortar, i.e. dry concrete? Why is it worth remembering the water-cement ratio? We will answer these and other questions in today's article!
DRY CONCRETE - DEFINITION
Dry cement mortar is made of the same ingredients as traditional concrete mix, but with lower water content. Such consistency makes the prepared mixture more loose and lumpy than classic concrete mortars with a more liquid consistency. As a consequence, dry concrete is not suitable e.g. pump delivery of concrete. B7.5, B10 and B15 class concrete is most often used to make a dry mortar. By the way, check out other concrete grades and find out what concrete mixer truck is. It is worth mentioning that dry concrete is more brittle than ordinary concrete, which, however, does not lose its key properties for the construction industry, because it is not of great importance for elements that only level and stabilize the terrain.
DRY MORTAR - APPLICATION
Dry concrete is mainly used in places where it will be in contact with the ground because it will collect water from it, needed to bind the mortar (hydration process). Dry cement mortar is therefore used in all substructures, sleepers or for soil stabilization. Where else is dry concrete used for? It turns out that it can be used for pouring the foundation, under the edges and curbs, in the construction of the driveway and for paving stones. In addition, special dry concrete is used to build roads in the so-called RCC (reinforced cement concrete) technology. Thanks to this technology, the construction of roads is very fast, and various types of rollers are used primarily for the mechanical compaction of their surface.
The pouring of dry cement mortar looks a bit different than in the case of classic screeds. Here, the use of a surface or submersible vibrator (such as concrete poker vibrators) is essential, and it is also recommended to spray the surface of the dry concrete with a water mist (avoid pressurized water so as not to accidentally wash out the aggregate). Both taking water from the ground and delivering it in the form of a dispersed mist reduce the strength of the screed, but at the same time dry concrete can be poured directly on the ground, making it ideal for stabilizing the ground.
DRY CONCRETE - PREPARATION
To obtain 1 m3 of B10 dry concrete, we need:
- 190 kg of cement
- 840 kg of sand
- 1230 kg of gravel
- 150 liters of water
We must quite precisely follow the instructions on the label, because adding too much water will reduce the final hardness and strength of the concrete. Various types of concrete mixers are most often used to prepare dry concrete, but an ordinary wheelbarrow or bucket will work just as well in the form of a temporary container. Nevertheless, regardless of the method of mixing, we must constantly observe the changing consistency of the mortar. How much does dry concrete cost? Depending on the material used and the class of concrete selected, we will pay approximately PLN 180 - 220 for 1 m3 of dry cement mortar.
WHAT IS THE WATER-CEMENT RATIO?
The water-cement ratio (w / c) is the ratio of the water content to the cement content in the concrete mix. The w / c ratio for dry concrete should be 0.5. Only then will this mixture be distinguished by high frost resistance, durability and low shrinkage. A larger ratio will mean a deterioration in physical properties.
CONCRETE EQUIPMENT AND MACHINES
In our store you can buy professional equipment necessary for the processing of floors and concrete elements. We recommend, for example, vibrating bars for concrete, concrete milling machines, industrial concrete power trowels, manual cutters, concrete mobile saws, electric hammers and chipping hammers. We only have equipment from renowned brands such as Husqvarna, Wacker Neuson, Bosch, Milwaukee, Enar or Altrad Belle.