Density and water content of nanoscale solid C-S-H formed in alkali-activated slag (AAS) paste and implications for chemical shrinkage

Journal Article · Wed Feb 15 00:00:00 EST 2012 · Cement and Concrete Research

DOI:https://doi.org/10.1016/j.cemconres.2011.11.003· OSTI ID:21596957

Allen, Andrew J ^[1]; Jennings, Hamlin M ^[2]

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1. National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)
2. CSHub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 Degree-Sign C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C-S-H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO){sub 0.99}-SiO{sub 2}-(Al{sub 2}O{sub 3}){sub 0.06}-(H{sub 2}O){sub 0.97}, d = (2.73 {+-} 0.02) g/cm{sup 3}) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the chemical shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 {+-} 1.5) cm{sup 3} of volumetric shrinkage per 100 g of unhydrated cement, is about twice the amount of chemical shrinkage exhibited by normal cement pastes.

• OSTI ID: 21596957
• Journal Information: Cement and Concrete Research, Vol. 42, Issue 2; Other Information: DOI: 10.1016/j.cemconres.2011.11.003; PII: S0008-8846(11)00288-2; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CALCIUM
CALCIUM OXIDES
CALCIUM SILICATES
CURING
DENSITY
HYDRATES
HYDRATION
MICROSTRUCTURE
NANOSTRUCTURES
NEUTRON DIFFRACTION
PORTLAND CEMENT
SHRINKAGE
SILICON OXIDES
SLAGS
SMALL ANGLE SCATTERING
SPECIFIC SURFACE AREA
SURFACE AREA
TEMPERATURE RANGE 0273-0400 K
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
ALUMINIUM COMPOUNDS
BUILDING MATERIALS
CALCIUM COMPOUNDS
CEMENTS
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
ELEMENTS
MATERIALS
METALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
SILICATES
SILICON COMPOUNDS
SOLVATION
SURFACE PROPERTIES
TEMPERATURE RANGE