High-efficiency water reducing agent is more convenient, safe and efficient when used, but it also has certain limitations. Its advantages are only relative. Therefore, you may encounter the following problems during construction and production.
1. It is difficult to unload from the mixer truck
Cause: It may be caused by severe incompatibility between cement and cement.
Treatment method: A compound test should be done for each batch of cement using the construction mix ratio before opening.
2. The slump of the concrete mixture suddenly increased and water bleeds
Reason: This batch of cement has good adaptability to the water-reducing agent.
Solution: The amount of admixture should be appropriately adjusted.
3. There are bubbles on the surface after hardening
Reason: In order to facilitate construction during use, the amount of water-reducing agent is increased.
Solution: Strictly carry out construction according to the mix ratio, improve construction technology, and strengthen construction management.
4. Concrete sets and hardens slowly
Reason: The amount of water-reducing agent is increased or the curing temperature is not enough.
Treatment method: Construction should be carried out strictly according to the mix ratio and the maintenance time should be extended.
5. The slump of concrete is significantly different from the design value
Cause: Incompatibility occurs when two admixtures are mixed.
Solution: Do a compatibility test before use and adjust the blending ratio.
Precautions for the use of water-reducing agents
a. Do not mix with other admixtures, especially naphthalene-based water-reducing agents, otherwise it will seriously affect the high performance of salt reduction. The effectiveness of aqueous agents. Any container that has been used to store concrete containing naphthalene-based water-reducing admixtures must be strictly cleaned before it can be used to store concrete containing high-efficiency water-reducing admixtures.
b. Concrete using naphthalene-based water-reducing agent and concrete using salt-based high-performance water-reducing agent can be applied to a concrete structure at the same time without any problem and will not affect the concrete structure. When pumping, the phenomenon that the front and rear trucks of concrete are produced with two different types of water-reducing agents should be avoided as much as possible. If this phenomenon occurs under special circumstances, it will generally not affect the performance of the concrete, but the pump bucket must be moved during pumping. The first truck of concrete should be poured as much as possible before adding the next truck of concrete.
c. High-efficiency water-reducing agent is slightly corrosive to iron. Long-term contact with iron will cause the salt-based high-performance water-reducing agent to discolor, produce odor, and reduce performance. Therefore, iron containers should be avoided. High-efficiency superplasticizer, preferably in plastic or stainless steel containers.
d. Salt high-performance admixture is sensitive to the fineness of cement, the mud content of sand and gravel, and the fineness modulus of sand. Generally, the finer the cement, the higher the mud content of sand and gravel, and the finer the sand. , the worse the effect of high-efficiency water reducing agent, so the above raw material indicators should be strictly controlled.
e. The water-reducing rate of high-efficiency water-reducing admixture is high, so the dosage is relatively low. If the slump of the concrete arriving at the construction site is too small, when it is necessary to add water-reducing admixture on the construction site, it is generally based on the whole vehicle. Each addition should not exceed 5kg, and the amount added per square should not exceed 2kg as standard.
f. High-efficiency water-reducing agent is non-toxic, non-corrosive, and does not pollute the environment. However, it is not edible. When it comes into contact with the human body and eyes, it should be rinsed with clean water as soon as possible. It may cause allergies to some people. If symptoms occur, seek medical treatment promptly.
It is generally believed that the water-reducing effect of water-reducing agents is mainly due to the adsorption and dispersion of water-reducing agents. By studying the cement hardening process in concrete, it can be found that during the mixing process of cement with water, since the cement minerals contain components with different charges, the mutual attraction of positive and negative charges will cause the concrete to produce a flocculation structure. The flocculation structure may also be formed due to the thermal movement of cement particles in the solution causing them to collide and attract each other at certain edges and corners. Since a lot of mixing water is wrapped in the flocculation structure, more water cannot be provided to lubricate the cement particles, thus reducing the workability of fresh concrete. </p
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