Research on the improvement of underwater workability of cement paste by composite polymers

The underwater workability of cement paste is essential for the application of non-dispersive underwater materials. However, the coordination of fluidity and flocculation remains challenging. While superplasticizers can enhance the fluidity of underwater cement paste, the absence of effective bonding between the flocculants and superplasticizers makes it struggle in controlling the underwater workability. This study aims to enhance the underwater workability of non-dispersive cement paste and clarify the relationship between specific sequences in the microstructure of polymer composite emulsions and cement paste performance. Using non-ionic waterborne epoxy resin (NEP) and polyacrylate latex (PAE) as raw materials, a response surface methodology was employed to design polymer-cement paste mixtures, examining the effects of the NEP-PAE on the workability of polymer-modified cement paste. The microstructural characteristics of the polymer-cement paste were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy, elucidating the reaction mechanisms of the NEP-PAE within the cement paste. The adsorption behavior of the NEP-PAE in the cement paste was analyzed using 1 H nuclear magnetic resonance, hydration heat, and Zeta potential techniques, revealing the microscopic mechanisms influencing the underwater workability of the cement paste. The results indicate the presence of multiple reactions simultaneously in the NEP-PAE modified cement system. The crosslinking reaction between –NH 2 in the NEP and –COOH produced from the hydrolysis of the PAE forms a polymer network structure, while the complexation of the PAE with Ca 2+ increases interlayer pore water content, enhancing paste fluidity. Additionally, the accelerated release of Ca 2+ and its coordination with the NEP within the network structure forms an integrated compound, enhancing underwater flocculation. Silica fume acts as a catalyst in the system. This work offers a polymer composite additive improving the underwater workability of cement paste and demonstrates the flocculation retention and fluidity promotion mechanism of the NEP-PAE via crosslinking, coordination, and hydration in cement paste. • Improvement in the underwater workability of composites can be achieved. • The NEP-PAE forms a well-structured network with cement particles. • NEP can crosslink with hydrolyzed PAE in the formation of –CONH– groups. • Ca 2+ ions from the gel part form ionic bonds with the polymer film.