Concrete Additives?
Additives (Concrete Admixture) are materials that are used to improve the properties of concrete. Admixtures, in addition to cement, water and aggregate, are added to concrete immediately before or during the mixing process. Additives can be used to reduce construction costs and ensure some required characteristics of fresh concrete. If the project officials face problems during the construction process, additives can be used as an emergency measure to solve implementation issues. did The percentage of concrete additives used in concrete varies depending on the type of additive and cement content. Typically, admixtures make up a relatively small percentage of the concrete mix. The amount used is usually five percent or less.
The Importance of Use of Concrete Additives
Apart from cement, aggregates (sand) or water, any other material added to concrete is known as admixture. Although these materials may not be needed, but sometimes in special conditions, concrete additives play the role of auxiliary force.
Additives are used in concrete to change its properties in different ways. Some common applications include improving workability, increasing or decreasing curing time, and increasing concrete strength. Additives can also be used for aesthetic reasons such as changing the color of cement.
By having engineering science and paying attention to the ingredients of concrete and checking the type of aggregates and the ratio of water to cement, it is possible to provide things like the efficiency and resistance of concrete in natural conditions. If it is not possible or there are special conditions, such as frost, high air temperature, increased wear or long-term exposure to degreasing salts or other chemicals, additives are added to concrete.
The Benefits of Concrete Additives
The benefits of using concrete additives include:
- مواد افزودنی مقدار سیمان مورد نیاز را کاهش میدهند و بتن را از نظر اقتصادی مقرون به صرفه میکنند.
- افزودنی ها کارپذیری بتن را افزایش میدهند.
- برخی از مواد افزودنی مقاومت اولیه بتن را افزایش میدهند.
- برخی مواد افزودنی مقاومت اولیه بتن را کاهش میدهند اما مقاومت نهایی بتن را در مقایسه با بتن معمولی افزایش میدهند.
- افزودنیها گرمای اولیه ناشی از هیدراتاسیون را کاهش میدهند و بر مشکل ترک خوردگی حرارتی در بتن غلبه میکنند.
- این مواد مقاومت بتن در برابر اثر یخ زدگی را بالا میبرند.
- مخلوط های بتنی با استفاده از مواد زائد حداکثر پایداری را حفظ میکنند.
- این مواد میتوانند زمان گیرش بتن را کاهش دهند.
- برخی از آنزیم های موجود در مواد افزودنی به عنوان یک عامل ضد باکتری عمل میکنند.
Application of Concrete Additive Materials
In addition, some of the main functions of using concrete admixtures are:
can reduce the water content required to achieve the required slump by 5-10%.
Reduces the setting speed of concrete and keeps it workable.
To neutralize the effect of air acceleration Hot to use It increases the speed of early resistance.
It reduces the time required for processing.
It can reduce the amount of water by 12 to 30% and produce a very smooth and workable concrete form.
To slow down the corrosion process of reinforcing steel. It is used in concrete.
It helps to improve the performance of concrete.
It helps to reduce shrinkage (concrete shrinkage).
Mix cement particles with water.
Reduces alkali-silica reaction.
Used to increase pumpability.
Increases bond between concrete and rebar.
Bond between existing concrete and increases new concrete.
Improves impact resistance and wear resistance.
Produces colored concrete or mortar.
Types of Concrete Additives
Admixtures are mixed with a mixture of cement and water to help set the control and harden the concrete. These additives can be prepared in liquid or powder form. Additives can be divided into two categories: chemical and mineral additives. Which additive to use depends on the nature of the project.
chemical additives
Chemicals are used for the following purposes:
Reduces project cost.
Overcomes emergency conditions in concrete operations. Execution, guarantees.
Corrects hardened concrete.
Mineral Additive Materials
Mineral materials are used for the following purposes:
Increases the strength of concrete. It regulates the nature of hardened concrete using hydraulic activity.
The division of concrete additives depends on their role:
Water reduction: These materials reduce the amount of water that must be added to concrete for a specific project. These types of additives are used in large-scale projects.
Accelerator: These materials accelerate the rate of cement hydration, which is especially useful for concreting in the cold months. Calcium chloride is used as an accelerator additive on unreinforced concrete.
Aeration: These admixtures are used to introduce microscopic air bubbles to stabilize the concrete. These materials prevent concrete from cracking in colder weather.
Shrinkage reduction: Concrete additives in slabs, bridge decks and buildings that have a chance of cracking and shrinkage problems. , is used.
Corrosion inhibition: These additives are used in cases where chloride salt is used. Chloride ions may corrode steel reinforcements and result in rusting. Areas that need this additive most include bridges, parking garages, and marine structures.
