- Author
-
Stutzman, P. E.
|
Clifton, J. R.
- Title
- Microstructural Features of Some Low Water/Solids, Silica Fume Mortars Cured at Different Temperatures.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Report
-
NISTIR 4790,
April 1992,
17 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
cements
|
silica
|
hydration
|
microscopy
|
x ray diffraction
|
curring temperature
|
microstructure
|
mortar
|
silica fume
- Abstract
- The microstructure of mortars with water/solids ratios (w/s) of 0.36 and 0.29, cured under water at 7, 23, and 40 deg C, were studied by scanning electron microscopy and x-ray powder diffractometry. The mortars contained silica fume and a superplasticizer. The degree of hydration and extent of pozzolanic reaction was estimated after quantifying the residual unhydrated cement by image analysis and the mas percent calcium hydroxide by x-ray powder diffraction. Their microstructures were fairly homogeneous in both the bulk paste and at the paste-aggregate transition zone. In all mortars, the outer 250 mum was hydrated to about 85 percent and highly microcracked. The degree of hydration decreased rapidly beyond the outer zone to about 69 percent and less microcracking was observed. A temperature effect on the reactivity of silica fume was found.