Effect of Hydration Temperature on Cement Paste Structure
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EFFECT OF HYDRATION TEMPERATURE ON CEMENT PASTE STRUCTURE
I. ODLER*, S. ABDUL-MAULA* AND LU ZHONGYA** *Technical University Clausthal, F.R.G. **Cement Research Institute, Anhui, Hefei, China
ABSTRACT The effect of temperature on the progress of hydration and cement paste structure and properties was studied using four laboratory-synthesized portland cements, hydrated at temperatures between 5 and 95°C for up to 90 days. In addition to an accelerated progress of hydration, elevated temperatures altered the phase composition and pore structure of the resulting hydrated material. Below 75°C the effect of temperature on the intrinsic bond properties of the hydrates formed remained negligible.
INTRODUCTION Data on the effect of temperature on the progress of hydration and the structure and strength properties of the resultant cement pastes are reported in the present paper. The aim of this work was to study whether and to what an extent the latter parameters are altered by variations of hydration temperature and whether an increase of temperature affects adversely cement strength even at isothermal curing conditions.
EXPERIMENTAL Four cements prepared using laboratory-synthesized clinkers were employed in the experiments. The potential phase composition of these clinkers is given in Table I. The cements were obtained by grinding the clinkers with gypsum (3% SO3 ) to a specific surface area (Blaine) of 3000 2 cm /g. The strength development of the cements was studied using 10 x 10 x 60 mm paste specimens prepared at a water-cement ratio of 0.30. The pastes were mixed and test specimens prepared after preheating the employed cement, water and molds to the selected curing temperature. After mixing and casting, the test specimens were allowed to hydrate at various temperatures, 50, 25°, 50°, 75° and 95°C, in a water-saturated atmosphere until testing. They were demolded after a sufficiently high strength was attained.
Table I Potential phase composition of synthesized clinkers
Clinker
C3 S
C2 S
C3A
C4 AF
1 II III IV
70 70 70 40
10 10 10 40
20 10 0 10
0 10 20 10
Mat. Res. Soc. Symp. Proc. Vol. 85. c1967 Materials Research Society
140
Fragments of the specimens were used for additional testing. The bound water content was determined as the ignition loss of samples in which the free water fraction was removed by grinding the material with acetone, filtering it, washing it on the filter with additional acetone and ethyl This very gentle procedure was employed to preether and drying in air. serve also the AFt and AFm phases, which are decomposed if more drastic water removal methods are employed. In the residue obtained after acetoneether extraction, the free lime was determined by the Franke extraction method and the nonreacted fraction of C3 S by X-ray diffraction. For DTA 1 studies , 10 mg sample was heated at 10°C/min in a N2 atmosphere. The porosity of the original samples was determined as the volume of water removed from the fully saturated material by acetone-ether extraction. Unlike all other determin
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