Title: Effect of Welan Gum SuperplasticizerCombinations on Properties of Cement Grouts
Author(s): K. H. Khayat and M. Saric-Coric
Publication: Symposium Paper
Appears on pages(s): 249-268
Keywords: calorimeter; cement; hydration; rheology; superplasticizer; viscosity
Welan gum is a viscosity-enhancing admixture used to retain some of the free water in cement-based materials and modify flow properties. The incorporation of welan gum and super-plasticizer can enable the production of highly flowable, yet stable systems with relatively low yield value and moderate viscosity. Such flow characteristics are useful for proportioning underwater concrete, post-tensioning grout, and self-consolidating concrete. Despite recent advances in such technological areas, limited data are available on the effect of welan gum-superplasticizer combinations on physico-chemical characteristics and kinetics of cement hydration. The study reported here was undertaken to evaluate the influence of welan gum and a naphthalene-based superplasticizer on fresh and hardened properties of cement paste with 0.40 W/C. The performance of reference grouts made without any admixture and those made with super-plasticizer were compared to the performance of mixtures made with 0.025, 0.055 and 0.075% welan gum by mass of cement. The effect of the admixtures on consistency, rheological properties, and stability of cement paste as well as setting time and changes in heat flux are discussed in this paper. Test results on hardened cement paste involving mercury porosimetry, scanning electron microscopy, and compressive strength development are also given.