1. Retarder: Pumped concrete mostly uses commercial concrete, which requires small slump loss. Especially for large-volume concrete or concrete constructed at high temperatures in summer, retarder must be added. components. When ordinary water reducing agents cannot meet the retarder requirements, chemical retarder should be added, such as hydroxycarboxylic hydrochloric acid, sugars, polyols, etc. It can reduce the slump loss, control the hydration heat release of concrete, and avoid temperature cracks.
2. Ordinary water-reducing agent: Ordinary water-reducing agent has a water-reducing effect and can reduce water ash while maintaining the fluidity required for pumping concrete. ratio to improve later intensity. Calcium lignosulfonate and sodium lignosulfonate are the most commonly used water reducing agents. In addition to the water-reducing effect, it also has retarding and air-entraining properties. Some pumps with lower grades and not too high slump requirements can even meet the requirements by adding only lignosulfonate water-reducing agents.
3. High-efficiency water-reducing agent: used in pumping concrete with high concrete design strength and high slump value requirements, such as high-performance concrete pumping High-efficiency water-reducing agents must be used in the agent, such as Nylon-based water-reducing agent, melamine-based water-reducing agent, and fatty acid-based water-reducing agent. These water-reducing agents have high water-reducing rates and are suitable for preparing high-grade, large-slump, self-leveling pumped concrete.
These water-reducing agents cause large slump losses and require compound retarder. Sulfamate water-reducing agents and polycarboxylate water-reducing agents are low slump loss water-reducing agents and are more suitable for formulating high-performance concrete with low water-cement ratio. When the water-cement ratio is 0.3, the water reduction rate of sulfamate can be as high as 30%. When used when the water-cement content is relatively large, they are prone to bleeding.
As buildings become larger and more high-rise, concrete needs to be transported to the pouring site along horizontal or vertical pipes under a certain pumping pressure. In order to meet this special construction requirement, in addition to having certain strength and durability requirements like ordinary concrete, pumped concrete also needs to have good fluidity, which requires the addition of pumping agents, which are mainly made of It is composed of water-reducing agent and retarder, as well as air-entraining, water-retaining components and mineral ultra-fine admixtures. Water-reducing admixture must be added to pumped concrete to meet workability and strength requirements. As for the retarder, it is used to adjust the concrete setting time according to seasonal changes. To meet transportation and construction requirements. Retarder delays the setting time of concrete to avoid excessive concrete slump loss during transportation or construction or the setting is not conducive to pumping and affects construction.
Water-reducing agent reduces the mixing water in the concrete mixing process. Under the condition of fixed label (water-cement ratio), the amount of cement is reduced, thereby improving the efficiency of concrete mixing. Reduced concrete cost.
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