During winter concrete construction, we habitually require commercial concrete stations to add antifreeze and early-strength agents. But how to choose and distinguish between the two? Sometimes we only distinguish between the two by their names. In fact, the two are completely different things. If used improperly, it will not only cause material waste, but also cause major quality accidents.
The difference between the two
1. Concrete early strength agent can accelerate the early strength development of concrete. Admixtures are called early strengthening agents. In actual use, most of them are compound early-strength agents. Inorganic salts are detrimental to the later strength of concrete; chloride early-strength agents can cause corrosion of steel bars; sulfate early-strength agents may cause volume expansion, reducing the durability of concrete; sodium salts Early strength agent will increase the alkali content in concrete and produce alkali-aggregate reaction with active silica aggregate. If the early strength agent is added excessively, although the early effect of the concrete is good, the later strength loss will be large, and the salt precipitation will be intensified, affecting the concrete finish; it will increase the conductivity of the concrete and increase the risk of shrinkage and cracking of the concrete. The main components of concrete early strength agent are: sodium chloride, calcium chloride, sodium sulfate, calcium sulfate, aluminum sulfate, potassium dichromate, triethanolamine, triisopropanolamine, methanol, ethanol, calcium formate, lithium oxalate , sodium acetate, etc. 2. Concrete antifreeze. Admixtures that can harden concrete at negative temperatures and achieve expected performance under specified curing conditions are called antifreeze. The vast majority of antifreeze agents are composite admixtures. The amount of early strength components and antifreeze component inorganic salts should be controlled. Otherwise, improper use will cause the later strength shrinkage of concrete, corrosion of steel bars, and alkali-aggregate reactions. The main components of concrete antifreeze are: antifreeze components (such as sodium nitrite, sodium chloride, methanol, urea, calcium chloride, potassium carbonate, etc.), air-entraining components (such as rosin soap, rosin thermopolymer, alkanes Sodium sulfonate, etc.), early strength components (such as sodium sulfate, calcium chloride, calcium nitrate, triethanolamine, etc.), water-reducing components (such as naphthalene series, melamine, sulfamic acid, etc.).
How to choose
In "Technical Specifications for Application of Concrete Admixtures" (GB50119) Chapter 7.3 Article 1 clearly stipulates: 1. When the daily minimum temperature is 0~-5℃, when the concrete is covered and maintained with plastic film and insulation materials, early strength agent or early strength water reducing agent can be used; 2. The daily minimum temperature is -5～-
10℃, -10～-15℃, -15～-20℃, when adopting the above insulation measures, the specified temperatures should be adopted respectively It is antifreeze for -5℃, -10℃ and -15℃.
It can be seen that the early strength agent is suitable for any low-temperature weather. Antifreeze is only used in conjunction with early strengthening agents when the minimum temperature is below -5°C.
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