Polycarboxylic acid water reducer is a new type of admixture, which has a higher water reduction rate than naphthalene series, better slump retention performance, and has a certain air entrainment, and less concrete shrinkage, use Of course, it is necessary to do experiments first to avoid bleeding due to excessive parameters. When should the polycarboxylic acid water reducer be added?
Water-reducing agent in concrete is mainly based on physical properties,
such as adsorption, space effect to prevent the flocculation of cement particles. As the cement hydration progresses, the water-reducing agent molecules will be wrapped up by the cement product and lose the water-reducing effect. As long as the concrete has plasticity, water reducing agent can be added. The newly added water-reducing agent can be adsorbed on the surface of cement to provide water-reducing effect
It can be added twice. When the slump loss is too fast to guarantee the normal pouring construction, you can add an appropriate amount (preferably tested) before the pouring and mix it evenly after construction. You can also add less water as long as you guarantee the water Do not change the glue ratio too much (requires data accumulation), it will not have a great impact on quality.Powder water reducer is added together with cement and other powder materials, and the liquid is added together with water, stirring for 2-3 minutes.
In the process of concrete mixing, the method of admixture has a great influence on the effect of the admixture. It can be roughly divided into pre-mixing method (mixing before mixing water), co-mixing method (mixing with mixing water at the same time), and stagnation method (in the mixing process, the admixture lags behind the water for 2min-3min mixing) 3. Post-mixing method (after a certain period of time after mixing, it is added to the concrete mixture one or more times, and then mixed two or more times). The blending method is better in the future, and the mixing method of wood calcium water-reducing agent has little effect, and the same blending method is better.
After the test ratio is determined, add it when mixing. Once the cooperation is completed, you are not allowed to add it yourself. Slump is planned in advance. If the slump is found not to meet the construction requirements, it is necessary to find the cause and solve it.
Polycarboxylic acid water-reducing agent is a high-performance water-reducing agent, the water-reducing rate can be around 25%, and other types of water-reducing agents can reach 20%, you can search for its description. Be careful not to add too much when producing concrete! If it is too much, the concrete will bleed, segregate, catch bottom, and have more air bubbles. The requirements for sand and gravel are strict, especially for sand, the mud content cannot be high, otherwise the admixture is too large and has no effect.