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Nano-silica has great potential in cement-based composites, but the agglomeration of nano particles in cement-based materials limits its development. A series of modified nano-silica were synthesized by grafting isobutylene alcohol poly-oxyethylene ether (TPEG) on to the surface of nano silica modified by silane coupling agent. The results show that the nano-silica modified by TPEG has better dispersibility and stability in an alkaline environment. In addition, compared with nano-silica, modified silica can make the cement hydration process controllable and improve the physical and mechanical properties of the mortar. [ABSTRACT FROM AUTHOR]

In this work, a novel total non-ionic polystyrene-polyurethane (PS-PU) composite latex was synthesized with polymerizable polyethylene glycol ether. Contrary to traditional styrene-butyl acrylate latex (St-BA), PS-PU has a smaller size and superior dispersion stability, and it is stable in saturated Ca(OH)2 even after 72 h. In fresh-mixed mortars, PS-PU showed a little adverse effect on workability and insignificant air entrainment, with little defoamer consumption. The retardation effect of PS-PU is also much milder than traditional St-BA. As for strength, PS-PU showed a less adverse effect on early and late age compressive strength, but its effect on flexural strength is not as pronounced as St-BA at high dosages (4% and 6%). The different behavior in cementitious materials between PS-PU and St-BA can be reasoned from their different adsorption behavior and surface charge properties, as the results from characterizations suggest. The non-ionic nature of PS-PU made it less prone to destabilization and adsorption, which turned out as the aforementioned behavior in cementitious systems. The difference can further be ascribed to the difference in their polymeric structure and properties. [ABSTRACT FROM AUTHOR]

• Calcium silicate-based nanofibers are synthesized through seed-mediated hydrothermal method. • The structure of unstable nanofiber is Na 2 Ca 3 Si 2 O 8. • Nanofibers with defects have strong interactions with Ca2+ ions. • The flexural strength of mortar can be enhanced by adding the nanofibers. Despite many studies of nanomaterials have been reported on the enhancement of cement-based materials, such as the pozzolanic effect of nano silica and flexural enhancement of fibers, there rarely are reports of the nanomaterials with both pozzolanic effect and shape-based enhancement. In this paper, anisotropic nanofibers were synthesized based on calcium silicates through hydrothermal method. Seed-mediated growth was conducted while SiO 2 nanoparticles served as the seeds and pseudo-wollastonite was used as the precursor. Importantly, the addition of the nanofibers can greatly improve the 28d flexural strength from 7.12 MPa to 8.99 MPa of the cement-based materials, which provides a new approach to realize the high performance of cement-based materials. [ABSTRACT FROM AUTHOR]