Concrete is a construction mixture that provides durability, reliability, resistance of the finished structure to the influences of any nature. Growing requirements to construction materials caused the necessity to improve their properties. Special additives for concrete improve the characteristics of mortar and commercial concrete, accelerate the rate of construction, reduce the cost of materials and energy resources. The question of what categories of additives exist is disclosed in detail below.
What are they used for?
The use of chemical additives is a simple, affordable and effective way to improve the quality of concrete mortars. Their use today is as important as the main components. Additives for concrete are designed to:
- achieving high performance qualities of cement stone;
- accelerate or retard hardening;
- improve water resistance;
- increasing resistance to temperature fluctuations and frost;
- eliminating the need for metered delivery of mortar;
- obtaining concrete with the specified characteristics.
Their amounts for a particular mixture are chosen under experimental conditions by the Skytrade technology.
Types of concrete admixtures
There are two types of additives for concrete: liquid, powder. Primarily they affect the specific properties of the fresh mortar – workability, the beginning of hardening. Concrete additives need to be added either to the mixing water or to the ready mix.
There is a separate type of specific additives – air-entraining and foaming additives. For example, an additive in concrete Kalmatron d. This type of modifiers is distinguished by its complex action. It is added to improve several parameters simultaneously. Concrete additive significantly reduces costs, avoids the incompatibility of several separate additives.
Gas pedals and retarders of hardening are also important. Additives for concrete in this category are popular, such as calcium chloride, sodium sulfate, calcium and sodium nitrates. Multicomponent formulations include calcium nitrite-nitrate, calcium nitrite-nitrate-calcium chloride. Below is a species classification of additives.
Modifiers
Modifying compounds are a category of substances that improve strength, durability, resistance to low temperatures. They reduce the permeability of concrete. Working with a modified product is more convenient, since its mobility improves. The mortar is laid evenly, filling all cracks and cavities.
Modifiers are classified according to the purpose of the resulting concrete. For example, there are additives in concrete, designed for the construction of wells, swimming pools. Another type of additives is used in the construction of facades or the formation of floor screed. Such a regulator, which improves the performance of the building mass, reduces its moisture permeability.
Plasticizers
This group is the most popular. There are four categories of plasticizers:
- Strong.
- Weak.
- Medium.
- The newest super plasticizers.
Additives in the latter category include substances for a comprehensive solution to the tasks set, increasing several characteristics of the cement mass. Depending on the scheme of action on concretes and the chemistry of the process, plasticizers are:
- Increasing mobility with the same amount of water.
- Reducing cement consumption by up to 10% without changing mobility.
- Increasing the strength at a constant mobility.
Additives are characterized by such advantages as:
- saving consumable material;
- improvement of mobility of sand-cement;
- increase in reliability by 20-25%;
- production of easy-to-consolidate mass;
- possibility of pouring thin-walled or densely reinforced structures;
- compaction of cement composition;
- improvement of frost and crack resistance;
- saving of energy resources by reducing the time of cement mass production.
The disadvantage of plasticizers – accelerating the rate of hardening. Therefore, it is recommended additional chemistry for concrete, accelerating this process. The resulting concretes are widely used in structures where ideally smooth floors and walls are needed.
Antifreeze
Additives for concrete and mortars are needed to reduce the freezing point of the water that is included in their composition. Anti-freeze chemistry in these products makes it easier to lay mortar and speeds up the process of concrete gaining strength in the cold season. These indicators allow saving consumables and prolonging service life of the finished product. Cements get frost-resistant properties. Sodium nitrite is the most popular additive. Other air-entraining components are also available.
Agility regulators
These specific additives, added in order to maintain the plasticity of the mortar in adverse conditions, are actively used in the hot summer. Concrete flow regulators are also useful when transporting mortar for long periods of time. Regulators improve the convenience of mortars when laying floor screeds.
Concrete strength gain additives
One of the types of additives of complex action are gas pedals of hardening or concrete hardeners. They are endowed with the qualities of both superplasticizers and hardening gas pedals. Organic and inorganic compounds without alkali are included in their composition. Gas pedals have a wide range of uses in construction, industry, road and transport in obtaining a commercial product or the area where you need shotcrete.
Chemical additives
There are several target categories of chemical additives added to concrete mortar. The classification is made according to the effect they have.
- Concrete modifiers of mobility and plasticity of the mixture.
- Substances to reduce moisture evaporation from the mortar.
- Waterproofing additives.
- Concrete stabilizers of the process of delamination of the sand-cement mass.
- Hardeners.
- Retarders setting time.
- Antifreeze additives.
- Foam and gas formers.
- Protective compounds.
- Air-binding compounds.
- Concrete additives that improve resistance to corrosion, exposure to living organics (mold, fungi).
- Hydrophobizers.
Chemicals can affect several properties, but only one will manifest itself. The principle of action of additives is similar to that of surfactants and can form a material with a spatial structure. Nitrite-based additives belong to this category. Such chemicals are very dangerous, so work with them with caution, following the instructions of skytrade.
Anticorrosive
Modifying products make concrete resistant to the effects of fresh water-filter, an aggressive liquid that causes corrosion of the material. These additives for concrete solve several problems:
- prevent the dissolution of the constituents of the finished stone;
- prevent leaching of reaction products of concrete and water;
- protect the surface from crystalline formations difficult to dissolve, leading to the destruction of the stone.
During the action of anti-corrosive chemicals carried a complete or partial binding of free calcium hydroxide in the concrete. The additive is mixed to increase the density and impermeability of the stone, reducing the pore volume in its structure. Cements are thus made hydrophobic.
Additives for self-compacting mixtures
A specific type of additives is used when pouring thin-walled structures. This category includes some new superplasticizers that improve mobility of the building mass and reliability, density with watertightness of the finished product. Concrete regulators allow you to reduce the consumption of cement without loss of quality of the resulting structure. Chemical modifiers of this type raise the grade of the mixture and the rate of hardening at the initial stage of hardening.
Complex additives for thin-walled and densely reinforced products greatly simplify the process of selecting the necessary components and determining their compatibility. Stabilizing superplasticizers are designed to solve several problems by adding only one substance. Their purpose is to obtain the maximum effect of interaction with the mixture components.
A wide range of modifying chemistry allows you to choose the product that will best meet the requirements of each specific case, increase the efficiency of the sand-cement composition, and prolong the operation of the finished product. However, when working with cement additives, it is important to accurately follow the recommendations and instructions on the proportions used, as specified by Skytrade specialists. The desired effect will not be achieved if there is any disproportion or violation of the preparation sequence.