The effect of d-gluconic acid as a retarder of ground granulated blast-furnace slag pastes. (1st October 2016)

• Record Type: Journal Article
• Authors: Schneider, Nick; Stephan, Dietmar
• Is Part Of: Construction & building materials. Volume 123(2016)
• Page Start: 99
• Page End: 105
• Publication Date: 2016-10-01
• Subjects: Retardation -- Ground granulated blast-furnace slag -- d-gluconic acid -- Hydration study -- Setting control -- Hardening control; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2016.06.127
• Languages: English
• ISSNs: 0950-0618

Abstract

Graphical abstract: Highlights: 1 wt.%d -gluconic acid retards the GGBFS suspension for at least 28 days. The retarder extends the dormant period of the hydration process. The retarder prevents not only the formation of ettringite but also that of strength-giving phases. No transformation of sulfite to sulfate is indicator for a retarded GGBFS suspension. Abstract: Ground granulated blast-furnace slag (GGBFS) is a latent hydraulic binder, which has also the ability to hydrate autonomously after contact with water. The rate of hydration strongly depends on the composition of the slag and the pH-value of the mixing water or activator. The retarded GGBFS suspension and an alkali activator can be used in a special two-component binder system for variable applications.d -gluconic acid (C6 H12 O7 ) was found to be a suitable retarder for GGBFS, which retarded the hydration at least 28 days. The retarder extends the dormant period of the hydration process and prevents mainly the formation of strength-giving phases. The interaction of GGBFS and retarder was investigated by heat flow calorimetry, measurement of non-purgeable organic carbon (NPOC), inductively coupled plasma optical emission spectrometry (ICP-OES), thermogravimetry (TG) and scanning electron microscopy (SEM). The basis for this study was a constant binder content, various concentrations of the retarder and different durations for the retarding effect. The concentrations were 0.05, 0.25 and 1.00% by weight of the mixing water. The samples were investigated between 0 and 28 days. At the end, one mixture was optimized for a shelf time of at least 28 days without separation.