Concrete pumping agent can significantly improve the workability of concrete, especially for lean concrete with low cement dosage. It can greatly improve the fluidity of the mixture without increasing the cement dosage, so that it can meet the pumping requirements; pumping The pumping agent has a certain retarding effect, especially the initial setting time. In large-volume concrete projects, the addition of pumping agent can also delay the early hydration heat of concrete and reduce the internal and external stress when the strength of the concrete is very low. Cracks caused by temperature differences; pumping agents can mainly reduce the water-cement ratio of concrete, and can improve the pore structure in concrete, making the pore structure in concrete tend to be a completely closed structure, and external carbon dioxide gas and water cannot enter the interior of the concrete. , thereby reducing carbonization, and the pumping agent can also improve the finish of the concrete surface and make the surface smooth.
According to the rheological characteristics of pumped concrete, the basic requirements for pumped concrete are: high fluidity without bleeding, in order to reduce pump pressure and maintain the homogeneity of the mixture; and have the ability to construct The required retardation time to reduce the slump loss of the concrete mix. For this reason, concrete pumping agents need to be added to the concrete for pumping construction. Generally speaking, pumping agent consists of the following parts:
1. High-efficiency water-reducing agent or ordinary water-reducing agent.
The pumping agent must have a certain water reducing rate, so water reducing agent needs to be added to reduce the water consumption of the concrete mixture. Commonly used water-reducing agents include nylon-based high-efficiency water-reducing agent, melamine-based high-efficiency water-reducing agent, sulfamic acid-based high-efficiency water-reducing agent, polycarboxylic acid-based high-efficiency deicing agent, calcium lignosulfonate ordinary water-reducing agent, and molasses-based ordinary water-reducing agents. Liquids, etc.
2. Retarder.
In engineering practice, it is often required to delay the setting time of pumped concrete to facilitate construction and pouring. It is also required that the slump of the concrete mixture is lost over time. Therefore, a certain amount of retarder is often added to concrete pumping agents to meet the above requirements. Commonly used retarders include: molasses, calcium sugar, calcium lignin, citric acid, phosphate, metaphosphate, etc.
3. Air-entraining agent.
In order to improve the workability of pumped concrete mixtures, reduce segregation and bleeding of the mixture, and improve the pumpability and durability of concrete, a certain amount of air-entraining agent is often added to the pumping agent. , such as rosin thermopolymer, rosin soap, dodecyl benzene sulfonate, etc., so that a certain amount of closed micro-bubbles can be introduced into the pumped concrete to meet the above requirements.
4. Pump aid.
In order to reduce the frictional resistance between the concrete mixture and the inner wall of the pump pipe, a certain amount of pump aid is often added to the pumping agent.
Commonly used concrete pumping agents include the following types:
(1) Natural and synthetic water-soluble organic polymers.
These admixtures can increase the viscosity of the mixing water. They include: cellulose ester, ethylene oxide, alginate, carrageenan, polypropylene amine, hydroxyethyl polymer and polypropylene amine. Vinyl alcohol, etc. The dosage of such substances is generally 0.02% to 0.05% of the weight of cement.
Water-soluble organic flocculants that can be adsorbed on cement particles, such as carboxystyrene copolymers, synthetic polyol electrolytes and natural hydrosols, can promote mutual adsorption between particles and improve mixing. The viscosity of the compound. The dosage of such substances is 0.01% to 0.10% of the cement weight.
(2) Various emulsions.
It can improve the mutual adsorption force between cement particles and provide a certain amount of ultra-fine particle organic emulsion in the cement slurry, such as paraffin emulsion, polypropylene emulsion, etc. The dosage of such substances is 0.10% to 1.5% of the cement weight.
(3) Various inorganic materials.
Various inorganic materials with large specific surface areas, such as diatomaceous earth, silica fume, asbestos powder, fly ash, calcium hydroxide, kaolin, untreated or burned volcanic ash, stone powder and other fiber materials, etc. , this type of material can improve the water retention capacity of the mixture, thereby improving the pumpability of the concrete. The dosage of such materials is 1% to 25% of the weight of cement.
Simply put, concrete pumping agent has the effects of high fluidization, cohesion, lubrication, and retardation. It can improve the pumping performance of concrete mixtures and is suitable for making high-strength or fluid-type concrete.
</p
微信扫一扫打赏
