Polycarboxylic acid is a new type of admixture, which has high water reduction rate and high adaptability, can improve the workability of concrete, and improve the workability and quality of concrete construction. Precautions for the use of polycarboxylic acid admixtures for concrete are embodied in the following aspects:
1. The sensitivity of polycarboxylic acid to water. Because the water reduction rate is relatively higher than that of Nai and aliphatic, and it has high dispersibility, the water reduction rate above 30% will become more obvious as the dosage increases, so pay attention to the comprehensive adjustment of the dosage and dosage.
2. The sensitivity of polycarboxylic acid to temperature. Temperature difference between day and night, temperature change point in the morning and evening. The water temperature, floor temperature, and glue temperature specification requirements are not more than 60 ° C, especially in the hot summer. In winter, it is considered that the delayed increase in slump and the decrease in the temperature of the mixture when the temperature is low are not conducive to the initial reaction, to avoid the sinking of the explosion mold and the concrete stones, and affect the structural homogeneity.
3. Polycarboxylic acid water reducing agent is highly sensitive to the mud content of aggregate, which is mainly manifested in the increase of the content with the increase of mud content, so the use of aggregate with excessive mud content should be avoided.
4. Adaptability to cement, adaptability of admixtures, and treatment of air bubbles, whether or not defoamers have been added.
5. After the concrete arrives at the construction site, care should be taken to avoid excessive unloading time. After 2 hours, concrete with polycarboxylic acid additives loses its plasticity faster than Nai-based systems, so care should be taken to avoid sticking and building.
6. Before each opening, the concrete truck should be cleaned and drained in time. It is forbidden to mix with concrete of other series of admixtures such as Nai series, which may cause abnormal accidents such as rapid solid state. The prepared Nai admixtures should be brought to the Materials Section, and the buckets should be cleaned and refilled with new polycarboxylic acid admixtures.
7. Polycarboxylic acid water reducing agent should not be stored in iron container, suitable for plastic, stainless steel, enamel and other materials. When using the original iron storage tank, the interior should be cleaned and the inner wall should be anti-corrosive.
8. Do not mix with other types of admixtures, which may cause rapid setting and abnormal phenomena.
9. The strength improvement effect is obvious. The addition of polycarboxylic acid water reducer can significantly improve the early strength of concrete, which is helpful to shorten the construction period.
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