Durability testing of concrete admixtures

In addition to having appropriate strength, concrete should also include application-level precautions, including resistance to cold, water penetration, chloride ion penetration, shrinkage, carbonization, Rigid steel rust, sulfate resistance, tensile strength fatigue deformation, alkali aggregate reaction, etc. are generally called service properties.

Waterproof concrete: refers to the property of concrete to resist the penetration of liquids and vapors. Because there are interconnected permeability and capillary tubes inside the concrete, as well as honeycombs and holes caused by the lack of concrete segregation due to vibration, allowing liquids and gases to penetrate into the concrete, the intrusion of water and gas will cause Rigid steel will rust, and the intrusion of harmful liquids and gases will cause the concrete to become mildewed, which will ultimately affect the quality of the concrete and its long-term safe operation. The waterproof concrete property of concrete is expressed by waterproof concrete model P. For example, P4 expresses that under the relative water level effect of 0.4N/㎜2, as a cone or cone test block with 6 required specifications in the waterproof concrete experiment, 4 test block water-proof layers are still maintained. The waterproof concrete models of concrete are usually divided into P4, P4, P6, P8, P10, and P12.

Cold resistance: refers to the potential of concrete to resist freezing. Concrete often freezes in cold areas, especially in environments where it is both exposed to water and refrigerated. This is because the water that penetrates into the concrete expands by 9% when it is cold and freezes, causing the permeability and capillary tubes inside the concrete to be subjected to considerable water pressure. If the temperature rises and the freeze thaws, it will continue to freeze. Melt, and the concrete will eventually be destroyed. The cold resistance of concrete is expressed by cold resistance model F. If the strength of the test block subjected to freezing and thawing is reduced by no more than 25% compared to the strength of the test block not subjected to freezing and thawing, the cold resistance is considered to be qualified. The cold-resistant model is expressed in terms of the maximum number of continuous freeze-thaw cycles that the test block can withstand. According to the frequency of freeze-thaw cycles, concrete cold-resistant models are generally divided into: F15, F25, F50, F100, F150 and F200.

Anti-adhesion: refers to the property of concrete to resist corrosion in various adhesive liquids and vapors. Substances that corrode concrete are mainly sulfate solutions, acidic and alkaline water, dynamic and or water-containing softened water, sea water, concentrated alkaline solutions, etc.

Temperature resistance: refers to the fact that the structure of concrete will not be damaged and its strength will not be significantly lost under the action of high temperature, and it has the characteristics of certain biological reliability.

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