What is concrete superplasticizer? Superplasticizer is a kind of concrete admixture that can reduce the water consumption of mixing under the condition of keeping the slump of concrete unchanged; it can improve its workability, reduce unit water consumption, increase concrete strength and improve durability, or reduce the amount of per unit cement and save cement.
Matters needing attention in concrete maintenance 1.Dispersion effect After cement mixes with water, due to the action of molecular gravity of cement particles, the cement slurry forms a flocculating structure, and the mixed water is wrapped in the cement particles. When the superplasticizer is added, the molecules of the superplasticizer can be adsorbed on the surface of the cement particles. The surface of the cement particles has the same electric charge (usually negative charge), forming electrostatic repulsion, causing the cement particles to disperse each other and destroy the flocculation structure. Release the wrapped part of the water and participate in the flow to effectively increase the fluidity of the concrete mixture. 2 Lubrication effect The polarity of the hydrophilic group in superplasticizer is very strong, so the adsorption film of superplasticizer on the surface of cement particles can form a stable solvated water film with water molecules, which has a good lubrication effect and can effectively reduce the sliding resistance between cement particles. to further improve the fluidity of concrete. 3. Steric hindrance effect The hydrophilic polyether side chain in the superplasticizer structure extends in the aqueous solution, thus forming a hydrophilic three-dimensional adsorption layer with a certain thickness on the surface of the adsorbed cement particles. When the cement particles approach, the adsorption layer begins to overlap; that is, the steric hindrance between the cement particles occurs. The more the overlap, the greater the steric repulsion, and the greater the hindrance to the condensation between the cement particles is so that the concrete slump is kept good. 4 Sustained release effect of graft copolymerization branched chain During the preparation of a new type of superplasticizer, such as polycarboxylic acid superplasticizer, some branched chains are grafted on the molecules of the superplasticizer, which can not only provide steric hindrance effect but also be cut off slowly in the high alkalinity environment of cement hydration, thus releasing dispersed polycarboxylic acids, which can improve the dispersion effect of cement particles and control slump loss.
Performance characteristics of polycarboxylic acid superplasticizer Workability Concrete and workability are excellent, non-segregation, non-bleeding, concrete appearance color is uniform. It is easy to achieve self-leveling and self-compacting concrete. Slump The slump loss is small over time, and the slump loss rate of ready-mixed concrete is less than 5% in 1h and less than 10% in 2h. Compressive strength The strengthening effect is remarkable; the 3D concrete compressive strength is increased by 50% to 110%, the 28d compressive strength is increased by 40% and 80%, and the 90d compressive strength is increased by 30% to 60%. When used to prepare high-grade concrete, the concrete has good cohesion and is easy to mix. Contraction Moderate air content and low shrinkage can significantly reduce concrete shrinkage; freeze-thaw resistance and carbonation resistance are significantly better than ordinary concrete and significantly improve concrete's volume stability and long-term durability. Heat of hydration Many mineral admixtures are used to reduce the early hydration heat of cement, which is beneficial to mass concrete and summer construction. High performance The environmental protection and energy saving of concrete and greatly reducing the alkali content of concrete can effectively prevent the alkali-aggregate reaction of concrete and achieve green, high-performance concrete.
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