MICROSTRUCTURE OF BINDER FROM THE POZZOLANIC REACTION BETWEEN LIME AND SILICEOUS FLY ASH, AND THE EFFECT OF LIMESTONE ADDITION
Currently, blended cements (CEM II) are the most commonly used cements in Europe.Most blended cements are binary, composed of clinker and one supplementary cementitiousmaterial (SCM). The clinker replacement level in blended cements may be increased bycombining different SCMs. In this paper a preliminary study on the combination of fly ash(FA) and limestone and their interaction was conducted. Cement-free pastes composed of lime/FA and lime/FA/limestone, respectively, werecompared. Clinker was excluded to simplify the system. In stead an excess of calciumhydroxide (Ca(OH)2) and alkaline mixing water (i.e. pH 13.2 and K/Na = 2:1) was used tosimulate the conditions in a hydrating cement paste. The mixes were cured at 5, 20, 38 and 80℃, and the reactions were stopped after 1, 3, 7,28 and 88 days of curing. The microstructure of the hardened binder was investigated bythermogravimetry (TG), X-ray-diffraction (XRD) and scanning electron microscopy (SEM). The addition of limestone resulted in a slight increase in the amount of chemically boundwater relative to the amount of FA. FA also appeared to bind more water than what wasprovided by calcium hydroxide. The XRD patterns confirmed an interaction between thelimestone and the FA, which resulted in the formation of calcium carboaluminate hydrates. Athigher temperatures (80℃) the calcium carboaluminate phase appeared to be unstable andother hydration phases (e.g. hydrogamet type phases) were observed.
K.De Weerdt H.Justnes
SINTEF Building and Infrastructure,Trondheim,Norway
国际会议
南京
英文
107-116
2008-10-13（万方平台首次上网日期，不代表论文的发表时间）