A preliminary study of thermal expansion compensation in cement by ZrW2O8 additions: Fid-Bau Portal

A preliminary study of thermal expansion compensation in cement by ZrW2O8 additions

Kofteros, M. / Rodriguez, S. / Tandon, V. / Murr, L.E.

The control, adjustment, or compensation for thermal expansion or the coefficient of thermal expansion (CTE or alpha) as well as low anisotropy in thermal expansion can pose a formidable materials science challenge. In addition, the development of materials with tolerable bulk thermal expansion as well as low anisotropy has found numerous practical applications in cookware, electronic devices, automotive components, etc. The addition of low, zero, or negative CTE materials to a variety of systems creating a self-compensating material composite or so-called 'smart' material also poses interesting practical prospects for a range of materials systems; especially cement composites. Zirconium tungstate, ZrW2O8, is one of the more interesting low CTE materials because it contracts on heating, and recent measurements have shown that the cubic compound exhibits an isotropic, negative CTE over its entire range of stability (from 0.3 to 1050 K). These properties were first reported by Martinek and Hummel more than 30 years ago. As an additive or reinforcement, in a composite, Zr(WO4)2 can reduce the bulk thermal expansion more effectively than a ceramic with a low, positive CTE. The isotropic CTE for Zr(WO4)2 of -9x10^-6 K^-1 can be compared with the average alpha for Invar (Fe-36Ni) of 1x10^-6 K^-1, ordinary glass (SiO2) where alpha nearly equal 0.5x10^-6 K^-1, or Al2O3 (9x10^-6 K^-1. The present work shows that the additions of ZrW2O8 (a negative thermal expansion coefficient material) to a cement-sand (mortar) mix have shown reductions in its thermal expansion. Extrapolations of the experimental data illustrate zero thermal expansion of cement with approximately 60 wt-% addition of ZrW2O8.