There are many varieties of concrete water-reducing admixtures, but they are indispensable in the actual production process. Although the amount of admixtures in concrete is small, they play an important role in improving the performance of concrete and reducing costs. Different problems such as workability and bleeding and segregation of concrete require different solutions. Common ones include ordinary water-reducing agents, air-entraining water-reducing agents, retarding water-reducing agents, etc., which are widely used in the construction industry. Of course, different types of concrete water-reducing admixtures have different application ranges. What should we pay attention to when choosing types of concrete water-reducing admixtures?
1. Of course, the purpose of use must be clear. For example, it is to improve workability, increase air content, improve strength and durability when adjusting condensation, save cement, save energy, speed up formwork and site turnover, etc., and choose reasonably according to the purpose.
2. Generally speaking, ordinary water reducing agents are suitable for concrete construction where the minimum temperature is above 5℃, and should not be used alone for steam curing concrete. High-efficiency water-reducing admixtures are generally applicable, but are more suitable for preparing fluid concrete, high-strength concrete, and steam concrete.
3. Air-entraining water-reducing agent is suitable for: anti-freeze concrete, anti-seepage concrete, pumped concrete, flowing concrete and ordinary concrete.
4. Retarding water-reducing admixture is suitable for: concrete constructed under hot temperature conditions, large-volume concrete, concrete for slip form construction, pumped concrete, concrete parked for a long time or transported over long distances, etc.
After figuring out what kind of concrete water-reducing agent is needed, use the concrete raw materials being used to conduct concrete performance tests on the water-reducing agent samples to determine the water-reducing agent and optimal dosage that meet the concrete performance requirements. It should be noted that the optimal dosage of water-reducing agent should not be selected near its saturated dosage. The dosage of water-reducing agent near the saturated dosage is very sensitive. Small fluctuations in concrete production may cause poor performance of concrete. huge changes. The optimal dosage of water-reducing agents for different types of water-reducing agents or from different manufacturers of the same type may be different. Within the saturated dosage range, the water-reducing rate of the water-reducing agent has a close linear relationship with the change in dosage. That is to say, it can be adjusted according to the dosage. Quantitative changes predict changes in concrete properties. When the optimal dosage of water-reducing agent is exceeded, the performance changes of concrete are very sensitive to the dosage of water-reducing agent, and various problems may occur at any time, such as segregation, bleeding, or the setting time becomes longer, or the air content increases, etc. . Generally speaking, water-reducing admixture has the best cost performance within the optimal dosage range. Therefore, when determining the optimal dosage of water-reducing agent, the working range of the dosage of water-reducing agent and the allowable fluctuation range of the concrete mix ratio should be tested.
In the actual production process, the sensitivity of polycarboxylate superplasticizer is also a quality indicator that needs attention. In actual production, concrete raw materials and ingredients will always fluctuate to a certain extent. For example, if the moisture content of sand during production fluctuates by 1%, the water consumption of concrete will fluctuate by 5kg/m3 to 8kg/m3. After determining the amount of water-reducing agent and concrete mix ratio, the water consumption of 5 kg/m3 to 8kg/m3 should be added or subtracted to see whether segregation, bleeding, and increased bubbles occur in the concrete in addition to changes in slump or fluidity. and other phenomena. In addition, technical plans for some emergencies should also be determined, such as traffic jams, long waiting times at the construction site that reduce the workability of concrete, etc. Water-reducing agents can be added on site to restore pumping and pouring performance. It is necessary to conduct tests in advance to determine the amount of water-reducing agent added, the setting time and the impact on early strength, and inform the construction unit of these plans.
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