In production, in order to improve the quality of construction and reduce the intake of raw materials, early-strength type water-reducing agents are becoming more and more popular. With the continuous development of technology, water-reducing agents are not only used in high-speed rail construction, but also in The road to development in the construction of other industries will surely become wider and wider. In the market, the mud-containing materials are complex and uneven, the sand and gravel moisture content fluctuates, the temperature changes, the dosage measurement fluctuations and other factors restrict the early-strength superplasticizer when it is directly applied to concrete, and it often appears that it does not adapt to the cement. Sensitivity issues such as poor performance, poor concrete performance, and possible large collapse damage make it impossible to meet the requirements of the construction site. As an admixture for high-performance concrete, early-strength high-performance water-reducing admixture undoubtedly has outstanding advantages and strong vitality, and will definitely be more widely used in concrete production. What are the advantages of early strength water reducing agent?
There is currently a lack of systematic research on the application of admixtures in dry-mixed mortar. Different types of admixtures are not very specific to different dry-mixed mortar products. Some admixtures (such as cellulose ethers) do not propose their own performance indicators for their application characteristics in dry-mixed mortar, but are standards for the light industry and chemical industry. . There are few studies on the action mechanism of admixtures in the hardened body of dry-mixed mortar. This will undoubtedly affect the reasonable and efficient use of admixtures in dry-mixed mortar. The early-strength series water-reducing agent is the third generation of water-reducing agent after the lignin and naphthalene series. Under the conditions of lower water-cement ratio and lower dosage, it has the characteristics of large fluidity and slump loss of the clean slurry. Small, environmentally friendly and other outstanding advantages. It has become an indispensable part of the construction industry. As its application fields continue to expand, the construction industry has more and more demands for it.
Lignin water-reducing agent
Lignin water-reducing agent is usually produced from the by-product of paper pulp produced by the sulfurous acid process. It generally includes three types: calcium lignin, sodium lignin and magnesium lignin. Calcium lignin and sodium lignin are commonly used, namely calcium lignosulfonate and sodium lignosulfonate, usually in powder form.
The general water-reducing rate of lignin water-reducing agent is 10~15%, and the dosage is 0.2~0.3%. It has a retarding effect on cement. If the dosage is too high, it will cause the cement to not solidify, and it has an air-entraining effect on the cement mortar.
Lignin water-reducing agent has a small dosage and low price, and is suitable for mortars with low water-reducing rate requirements. Better results will be achieved when used in conjunction with high-efficiency water-reducing admixtures.
Cai series water reducing agent
Naphthalene series water reducing agent is prepared by using industrial naphthalene, formaldehyde, concentrated sulfuric acid and liquid alkali as the main raw materials under certain reaction conditions. The main ingredients It is naphthalene sulfonic acid formaldehyde condensate. Usually in liquid or powder form as the final product, it is one of the most widely used water reducing agents at present. The dosage of powdery products is generally 0.5~1.0% of cement weight, and the water reduction rate can reach about 20%.
Adding this alkaline water agent to mortar can significantly increase the strength, slightly extend the setting time, improve the dispersion of cement and other additives in the mortar, and significantly improve the constructability and impermeability of the mortar. properties, frost resistance, chemical resistance, and reduced shrinkage. In cement mortar, it is widely used due to its high water reduction rate and moderate price. However, when this water-reducing agent is used in gypsum-based mortar, the water-reducing effect is not obvious.
Early-strength water-reducing admixture is the third generation of high-performance water-reducing admixtures developed after ordinary water-reducing agents represented by wood calcium and wood magnesium and high-efficiency water-reducing agents represented by naphthalene series and melamine series. The advantages of the early-strength water-reducing agent compared to the naphthalene-based water-reducing agent are briefly summarized as follows:
1. The water-reducing rate of the early-strength water-reducing agent is significantly higher than that of the naphthalene-based water-reducing agent. , the dosage of water-reducing agent is much lower than that of naphthalene-based water-reducing agent, and its water-reducing rate can be as high as 45%.
2. Naphthalene-based water-reducing agents generally have relatively large slump losses. Generally speaking, increasing the dosage will help reduce slump loss, but adding a little more naphthalene-based water-reducing agents Concrete is easy to segregate, so it is difficult to adjust if the material is not good. However, concrete prepared with polycarboxylic water-reducing agent can still meet the pumping requirements after 1 hour.
3. As the dosage increases, the ultimate water-reducing rate of the early-strength type is much higher than that of the naphthalene-based water-reducing agent, and the naphthalene-based water-reducing agent has basically reached the limit when the dosage is about 2.0%. , which shows that early-strength water-reducing admixture is more suitable for formulating high-strength concrete with low water-cement ratio.
4. When the dosage is appropriate, the concrete prepared with early-strength concrete has excellent workability, no segregation or bleeding, and the concrete has a uniform appearance and color. When used to prepare high-grade concrete, the concrete has good cohesion and is easy to mix.
5. The product has good stability, no stratification or precipitation occurs during long-term storage, and no crystallization occurs at low temperatures.
6. The production process of naphthalene-based water-reducing admixtures has certain pollution to the environment. However, early-strength water-reducing admixtures adopt environmentally friendly and green synthetic production processes, which can save cement, improve concrete performance, and promote green concrete, Sustainable development of low-carbon concrete technology
The advantages of early-strength water-reducing admixtures are obviously the future industry trend. More and more water-reducing admixtures used in industries are gradually replaced by early-strength superplasticizers
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