Concrete retarder ratio

Clay mud with obvious swelling properties and water absorption capacity will have a major impact on the working properties and final physical properties of concrete. The common clayey muds in stones mainly include kaolin, illite and montmorillonite. The same type of water-reducing agent has different sensitivities to mud powder composed of different minerals, and this difference is very important for the selection of water-reducing agents and the development of mud-resistant water-reducing agents and anti-mud agents. Wang Ziming and Cheng Xun found that under the same water-cement ratio and water-reducing agent dosage, the adsorption capacity of kaolin for polycarboxylic acid is several times that of concrete, while bentonite (the main ingredient is montmorillonite) is dozens of times that of concrete; bentonite The impact on the expansion of mortar is also obvious in higher clay.

When the metakaolin content is 5.0%, it has little harm to the fluidity of the concrete; when the metakaolin content is 10% to 15%, the fluidity of the concrete decreases. Wu Hao et al. found that sand and gravel in different regions affect the properties of polycarboxylate superplasticizer to varying degrees. XRD was used to determine that the main components of mud in sand and gravel are SiO2, feldspar, mica and clay minerals. According to the TOC test of PCE-1, it was found that feldspar and sericite have extremely strong adsorption effects, and montmorillonite has the strongest adsorption potential. Ma Baoguo et al. studied the adsorption characteristics of polycarboxylate water-reducing agent, naphthalene-based water-reducing agent and sodium lignosulfonate on the surface of concrete, kaolin and montmorillonite particles and found that naphthalene-based water-reducing agent has a large mud content. The application effect in concrete is better than polycarboxylic acid superplasticizer and lignin sulfonate.

Sakai et al. used limestone powder to simulate the hydration mechanism of concrete, studied the impact of mud on the mobility of polycarboxylate superplasticizer slurry, and found that montmorillonite has higher sensitivity potential than kaolin. Norvell et al. found that the water demand of mortar mixed with montmorillonite may exceed that of mortar mixed with kaolin and illite under the condition of uniform movement of mortar. Munoz et al. found that the effects of sodium montmorillonite and calcium montmorillonite on concrete rebound are inversely proportional to illite and kaolin, and as the water-cement ratio increases, the effects of the two montmorillonites on concrete rebound are moderately reduced. Fernandes stated that montmorillonite is more harmful to concrete rebound than kaolin because not only is montmorillonite more hygroscopic than illite and kaolin, but when the water-cement ratio moves at a constant speed, a large number of large bubbles are introduced, making it difficult for concrete to separate; To obtain appropriate mobility, the water-cement ratio must be increased, which will lead to reduced concrete rebound.

At the same time, montmorillonite will absorb and cover the surface of the stone or form a loose non-empty subset of particles that blocks the bond between concrete and stone, thus forming a weak page connection in the cement stone. Areas and cavity areas to reduce the concrete segregation and strength of concrete.

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