1, in-situ polymerization grafting method
Using polyether as the polymerization medium of unsaturated monomer, the main chain polymerization and the introduction of side chain can be carried out at the same time. The process is simple, and the molecular weight of the synthesized water reducer can be controlled to a certain extent. However, the esterification reaction involved in this method is reversible, which leads to low grafting rate in aqueous solution and has been gradually eliminated.
2. Polymerization before functionalization
In this method, the main chain of water reducer is synthesized first, and then the side chain is introduced to functionalize by other methods. This method is difficult to operate, and the molecular structure of water reducer is not flexible, and the compatibility between monomers is not good, which makes the use of this method greatly limited.
3. Direct polymerization of monomers
The method comprises the following steps: firstly, preparing an active macromonomer; and then, initiating by an initiator, polymerizing the small monomer and the macromonomer in an aqueous solution. With the maturity of the synthesis process of macromonomer, there are more and more kinds, and this synthesis method has become the most commonly used method for the synthesis of PLA water reducer at this stage.
operating characteristic
1, low dosage, high water reducing rate, and the water reducing rate can be as high as 45%.
2. The slump loss changes little with time. The slump loss rate of ready-mixed concrete is less than 5% at 1h and less than 10% at 2 h.
3. The reinforcement effect is remarkable. The compressive strength of concrete is increased by 50 ~ 1 10% at 3d, 40 ~ 80% at 28th and 30 ~ 60% at 90d.
4, concrete workability is excellent, no segregation, bleeding phenomenon, concrete appearance color is uniform. When used to prepare high-grade concrete, the concrete has good cohesiveness and is easy to mix.
5, moderate air content, no adverse effect on the elastic modulus of concrete, good frost resistance and durability.
6. It can reduce the early hydration heat of cement, which is beneficial to mass concrete and summer construction.
7. Excellent adaptability, good compatibility between cement and admixture, good temperature adaptability and good compatibility with different kinds of cement and admixture, which solves the problem of poor compatibility between other water reducing agents and cementitious materials.
8. Low shrinkage can obviously reduce the shrinkage of concrete, and its freeze-thaw resistance and carbonation resistance are obviously better than ordinary concrete; Obviously improve that volume stability and long-term durability of concrete.
9. The alkali content is extremely low, and the alkali content is ≤0.2%, which can effectively prevent the occurrence of alkali-aggregate reaction.
10, the product has good stability, no delamination, no precipitation and no crystallization at low temperature after long-term storage.
1 1, the product is environment-friendly and does not contain formaldehyde, so it is an environment-friendly product.
12, good economic benefit, lower comprehensive engineering cost than other products, and cement 15-25% can be saved under the same strength condition.
Refer to the above contents: Baidu Encyclopedia-polycarboxylic acid water reducer, Baidu Encyclopedia-water reducer.