E.G. Swenson

Microstructure of calcium silicate hydrates

WHILE CONSIDERABLE ATTENTION AND STUDY HAVE BEEN DEVOTED TO THE STRUCTURE AND MORPHOLOGY OF CALCUM SILICATE HYDRATE, NEITHER THE INTERRELATION BETWEEN THE VARIOUS OBSERVED PARTICLE SHAPES NOR THEIR ROLE IN FORMATION OF THE FINAL MICROSTRUCTURE OF THE HARDENED PASTE HAS BEEN ESTABLISHED. THE DIVISION OF BUILDING RESEARCH OF THE CANADIAN NATIONAL RESEARCH COUNCIL HAS RECENTLY BEEN STUDYING MORPHOLOGICAL CHANGES IN THE HYDRATION PRODUCTS OF THE VARIOUS PURE CONSTITUENTS, SINGLY AND IN COMBINATIONS, AS WELL AS OF CEMENT PASTE. IN THE WORK REPORTED HERE, MORPHOLOGICAL AND MICROSTRUCTURAL CHANGES WITH TIME OF A HYDRATING TRICALCIUM SILICATE WERE STUDIED BY ELECTRON MICROSCOPY AND X-RAY DIFFRACTION. PRODUCTS CONSISTED OF AMORPHOUS MATERIAL, CRUMPLED FOILS, FIBROUS PARTICLES, AND PLATES. THE PLATES APPEAR TO HAVE AN UNDERLYING MESH STRUCTURE OF INTERLOCKING FIBERS, THE SPACE BETWEEN THESE HAVING BEEN FILLED WITH A LIME-RICH CALCIUM SILICATE HYDRATE OR WITH CALCIUM HYDROXIDE. THE PLATY MORPHOLOGY OCCURS FOR THE SILICATE HYDRATES AS WELL AS FOR CALCIUM HYDROXIDE. THIS STUDY INCLUDED ALSO PORTLAND CEMENT PASTE TO ALLOW A COMPARISON WITH THE TRICALCIUM SILICATE SYSTEM. CONCLUSIONS ARE GIVEN REGARDING MECHANICAL PROPERTIES OF THESE CEMENTING SYSTEMS.

Alkali-aggregate reaction in Nova Scotia I. Summary of a five-year study

Abstract Laboratory experiments confirmed that alkali-aggregate reaction caused excessive expansion of some Nova Scotia concrete. Major rock types were tested as aggregates in mortar bars and concrete prisms and as rock cylinders immersed in alkali solution. Greywackes, argillites, phyllites, and some quartzites, schists and rhyolites were identified as highly reactive through petrographic studies and length change tests.

Alkali-aggregate reaction in nova Scotia IV. Character of the reaction

Abstract Studies of an alkali-aggregate reaction in Nova Scotia have shown that it differs in important characteristics from the well-known alkali-silica reaction. It is discussed in relation to previously published concepts of mechanism and an explanation is proposed for the alkali-expansivity of some Appalachian rocks.

Volume change on first drying of hydrated portland cement with and without admixtures

Abstract The effect of admixtures of several types on the volume change characteristics of portland cement pastes is reported. Samples were cut in the form of wafers and dried step by step through several humidities down to 40 per cent; other samples were dried to the d-dried state. Large first drying shrinkages were obtained with extra dosages of calcium lignosulphonate, hydroxy carboxylic acids, and triethanolamine. Below 40 per cent RH all samples showed similar behavior with further drying or rewetting. It is suggested that the effect of admixture is mainly one of degree of dispersion in terms of alignment of sheets and displacement of ends of sheets.

MORPHOLOGY AND MICROSTRUCTURE OF HYDRATING PORTLAND CEMENT AND ITS CONSTITUENTS. II. CHANGES IN HYDRATION OF CALCIUM SILICATES ALONE AND IN THE PRESENCE OF TRIETHANOLAMINE AND CALCIUM LIGNOSULPHONATE, BOTH WITH AND WITHOUT GYPSUM

Abstract Systematic sequential observations with the electron microscope were made of the morphological changes which occurred during hydration of C 3 S ∗ and C 2 S pastes, with and without the presence of gypsum. The specific effects of each of two admixtures were studied: triethanolamine and calcium lignosulphonate. Water to C 3 S or C 2 S ratio was 0.5 and admixture dosage was 0.5%. The admixtures had some effect on changes in microstructure, but they had a pronounced influence on the rate of the hydration processes.

Alkali-aggregate reaction in nova scotia III. Laboratory studies of volume change

Abstract Studies of alkali-expansivity of Nova Scotia rock types included extensive lenght change tests of mortar bars and concrete prisms, and also cylinders immersed in alkali solution. The effects of such variables as alkali content, type of alkali, temperature, wet and dry cycling, anisotropy, optimum proportion of rock type, and the influence of pozzolan and fly ash were studied. Results obtained were correlated with petrographic studies so that potentially expansive rock types in the provinve may be recognized. Preventive measures applicable to field use were determined form analyses of expansion data.

Morphology and microstructure of hydrating portland cement and its constituents I. Changes in hydration of tricalcium aluminate alone and in the presence of triethanolamine or calcium lignosulphonate

Abstract Morphological changes which occur during the hydration of C3A∗ paste were observed by electron microscopy from the age of 5 minutes to 3 months. X-ray analyses were used to identify phases. The effects of the admixtures, triethanolamine and calcium lignosulphonate, were investigated with and without gypsum. The dosage of admixture was 0.5%; the water to C3A ratio was 1.0. The results showed clearly the morphological changes that took place as hydration proceeded, and showed the specific influences of each of the two admixtures.

Alkali-aggregate reaction in Nova Scotia II. Field and petrographic studies

CERTAIN SILICEOUS AND SEDIMENTARY ROCKS IN NOVA SCOTIA, WHEN USED AS AGGREGATE WITH HIGH ALKALI CEMENT, HAVE PRODUCED EXCESSIVE EXPANSION OF CONCRETE. LABORATORY STUDIES SHOWED A TYPE OF ALKALI-AGGREGATE REACTION TO BE RESPONSIBLE. ROCK TYPES IN STRUCTURES AND IN AGGREGATE SOURCES WERE IDENTIFIED BY PETROGRAPHIC EXAMINATION, THE MAIN TYPES BEING SELECTED FOR STUDY OF ALKALI-REACTIVITY. /AUTHOR/

Morphology and microstructure of hydrating portland cement and its constituents V. Changes in hydration of portland cement with and without the presence of triethanolamine and calcium lignosulphonate

Abstract Systematic sequential observations with the electron microscope were made of the morphological changes that occured during the hydration of normal portland cement paste. The specific effect of each of two admixtures, triethanolamine and calcium lignosulphonate, was studied. The hydration products observed were clearly the same as those noted in the pastes of pure minerals or mixtures of these. The morphological changes that occurred appeared to be the same, and the rate of change effected by the presence of an organic admixture was found to be very similar.

Morphology and microstructure of hydrating portland cement and its constituents III. Changes in the hydration of a mixture of C3S, C3A and gypsum with and without triethanolamine and calcium lignosulphonate present

Systematic sequential observations with the electron microscope were made of the morphological changes which occurred during the hydration of a paste mixture of C3S, C3A and gypsum. It was found that this system produced hydration products similar in nature to those produced by the monomineral systems with gypsum present. The two organic admixtures studied had some effect on changes in morphology and microstructure of the hydrating mixture, but they showed a pronounced influence on the rate of the hydration processes.