Effect of Limestone Powder Mixing Methods on the Performance of Mass Concrete.

Using limestone powder (LP), the by-product of manufactured sand, to replace part of fly ash (FA) or manufactured sand could not only turn waste into treasure and decrease the price of concrete, but could also enhance the performance of concrete and reduce environmental pollution. However, the impact of various LP incorporation methods on the performance of mass concrete was inconsistent. In this paper, the effects of LP on the workability, compressive strength, constrained expansion rate, hydration temperature and impermeability of mass concrete were studied by replacing FA or manufactured sand alone and replacing FA and manufactured sand simultaneously. The results showed that the impact of LP on the performance of mass concrete was equal when it replaced FA alone and FA and manufactured sand at the same time. When the replacement amount was 20%, the workability, expansibility and early strength of concrete were improved, but the later strength and impermeability were slightly reduced. The workability, compressive strength, expansibility and impermeability of mass concrete were improved when manufactured sand was replaced alone, and the optimal dosage was 10%. The LP, moreover, reduced the hydration temperature peak of concrete in three kinds of mixing methods, but the temperature peak appeared earlier. At lower dosages, LP optimized pore structure and promoted the early hydration of cement through filler effects and nucleation effects. When LP replaced manufactured sand, the microstructure of concrete was more dense, so the replacement of manufactured sand had a better effect on the improvement of concrete properties. A reference value for the use of LP in mass concrete is provided in this study.

Mechanism of Acrylate Emulsion-Modified Cement-Based Materials.

Polymer-modified cement-based materials have been widely used in building materials. Polymers play a crucial role in improving the performance of cement-based materials. At the same time, different polymers are added according to specific special requirements to meet the needs of the industry. Therefore, this paper reviewed the research on the performance and mechanism of acrylic lotion in modifying cement-based materials. Firstly, the role of acrylate lotion in the improvement of the volume stability, mechanical properties, and durability of cement-based materials was discussed to explore the advantages and disadvantages further, optimize the application of polymer in cement-based materials according to the performance improvement, and amplify the advantages of polymer modification. Secondly, the physicochemical mechanism of acrylate-lotion-modified cement-based materials was discussed, and the products and reactants of acrylate lotion in the reaction process of cement-based materials, as well as the interaction mechanism of acrylic lotion and cement hydrates, were clarified. Cement hydration is a crucial step in exploring the mechanism of polymer-modified cement-based materials. Due to the acrylate lotion filled on the cement surface and the physical and chemical interaction between them, the cement hydration is delayed, resulting in the cement retarding phenomenon. This paper describes its mechanism. Finally, the improvement effect of acrylate lotion on the performance of cement-based materials was reviewed, the research methods of mechanism research on acrylate-lotion-modified cement-based materials were evaluated, and suggestions for future research methods were provided.