Accelerator admixtures: which are mixed with the concrete to increase the percentage of strength development and shorten the setting time. Compounds that can be used are calcium chloride, Triethanolamine (TEA) in calcium format, soluble organic salts, sodium nitrite, sodium sulfate, sodium aluminates, sodium silicate, carbonate, and sodium hydroxide. potassium.
Retarding admixtures They are used to slow down the initial rate of cement hydration or to prolong the setting of the cement paste in the concrete. The compounds that can be used are derivatives of soluble carbohydrates: starch, Hydroxylated carboxylic acids, inorganic retarders, and sugar.
Air-entraining admixtures Help to incorporate a controlled amount of air, in the form of millions of small non-coalescing bubbles distributed throughout the concrete, during mixing, without significantly altering the rate of setting or curing of the concrete.
With the right amount of entrained air, the workability and durability of the concrete increases. The compounds that can be used are natural wood resins, fats, lignosulphonate, and alkyl sulfates.
Water-reducing additives Help increase the rate of strength gain and increase handling.
The compounds that can be used are mixtures of calcium, calcium chloride and lignosulfonate, a mixture of sugars or Hydroxylated carboxylic acids, and lignosulphonate.
Plasticizers and Superplasticizer They are used for better handling. The compounds that can be used are Hydroxylated carboxylic acid derivatives, calcium and sodium lignosulphonate, sulfated melamine-formaldehyde resin, mixtures of saccharine and acid amides.
Some other special additives used in concrete are:
1) Joint additives
2) Anti-air additives
3) Gas additives
4) Anti-corrosion additives
5) Adjutants that reduce shrinkage
6) Additives that are impervious to water or humidity and that reduce permeability.
7) Union aids
8) Concrete surface hardening additives
9) colorings admixtures or pigments
10). Fungicidal, germicidal and insecticidal admixtures
11). Set Retarding Admixture – Liquid Glucose or Sodium Gluconate is used.
12) Curing and Setting Accelerator-Triethanolamine
13) One of them is calcium chloride, an additive that accelerates hardening.
In addition to the above and their combinations, formalin is also used as a preservative. Certain buffer salts can be used to control the pHs And many other chemicals to fine-tune specific properties.
You can use infrared spectroscopy if you want to know the general bases of the additives used.
In the nutshell, ultimately it is divided into mineral admixtures that are powdered and it is added to concrete before or during mixing to improve or change the specific plasticity or hardening properties of Portland cement concrete. These additives are usually natural ingredients or derived materials. Usually, up to 40% is added to concrete. Cement weight.
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