Search

This paper reports the treatment of bottle-hydrated portland cement with organosilanes, oleic acid and octadecylamine intended to reduce the sorption of water and the corresponding dimensional changes. Compacts were made from the treated hydrated cement powder to simulate cement paste and allow measurements of sorption-dimensional change characteristics and microhardness. It was found that organochlorosilanes are not suitable for the treatment because the HCl released during the reaction produced undesirable side effects and in some cases increased the adsorption and expansion of the cement. Hexamethyldisilazane was more effective, reducing adsorption by 10 to 20%. Oleic acid was effective at concentrations as high as 25% by weight, but serious loss in mechanical property of microhardness was experienced.

The standard tapping machine is the most commonly used source for impact insulation testing of floors and floor coverings. In this paper the stages of the transmission of impact noise through a floor are considered. The force spectrum of the hammer impulse is calculated digitally. By assuming that the cushioning effect of the floor covering can be separated from the concrete floor on which it is laid, it is possible to predict the sound field produced by the tapping machine. It is necessary to know the sound field produced by the tapping machine on the bare floor and the force spectra of the hammer on the bare and the covered floor. The predicted results agree well with measured cases. This validates the definition of the behaviour of a floor covering in terms of impact insulation improvement when used on concrete slab floors. It also shows that impact insulation improvement can be calculated from a knowledge only of the hammer impact spectrum. An ageing or hardening process which occurs after successive hammer blows on soft floor coverings is also described.

The Quebec autoroute on the North Shore of the St. Lawrence River between Montreal and Quebec City traverses deep deposits of compressible marine clay. One of the overpass structures at Berthierville is supported on twelve 39-in. (1 m) diameter reinforced concrete piles, which pass through 270 ft (82 m) of soil and finally rest on shale bedrock. The paper presents measurements of settlement and pore water pressures in the soil at various depths under the fill, and of axial deformations in two of the piles. It provides a set of relatively rare field observations on which to base an approximate evaluation of the rate and magnitude of negative skin friction development under the described field conditions.

Although of a general nature, this paper summarizes the causes of cracking in concrete and makes specific reference to more detailed studies.

This paper includes the study of the following problems: The local stress concentration in the large particles of the coarse aggregate in non-reinforced concrete during setting and as a result of conversion of water. Stress and deformation patterns in specimens of non-reinforced concrete under constant load and constant elongation, respectively, i. e., stress and deformation patterns due to contraction and relaxation, respectively.

In the course of a Canadian investigation, a dolomitic limestone coarse aggregate has been found that produces excessive expansion and cracking in concrete. Despite the observed influence of cement alkalis, the results of the ASTM Test Method C289 on the limestone were negative. The results of the ASTM mortar bar test were also negative but indicated some alkali-reactivity in the limestone. This brief paper is intended to provide for the benefit of those concerned with the use of the standard tests for alkali- aggregate reaction a record of this Canadian experience with an apparently unusual case of cement-aggregate reaction for which the standard tests were not effective.

The practice of regarding the thermal properties of concrete as constants may lead to serious errors in heat flow calculations. Because of the physicochemical instability of concrete it is very difficult to procure valid experimental information. In this paper theoretical considerations are presented which, together with some experimental data, will make the assessment of the thermal properties of concrete possible. The calculation procedure is illustrated by examples., Reprinted from: ASTM Journal of Materials, v. 5, no. 1, March 1970, p. 47-74. ISSN: 0022-2453

This paper, a translation of an extensive German article, reviews the behaviour of concrete and reinforced concrete in fire and discusses by means of examples the fire related properties of concrete and concrete products, particularly concrete masonry and precast concrete. It deals separately with structural parts of buildings, such as floors, beams, walls and columns. It is shown that it is now possible to build concrete, reinforced concrete and prestressed concrete structures of almost any desired fire resistance. Even in relatively slender precast concrete construction considerable fire resistance periods can be achieved.

This paper summarizes the results of a probabilistic study of ultimate moment and ductility ratio of reinforced concrete. The results are of use in assessing existing design formulas and safety provisions.

Certain rock types, used as aggregate, react with alkalis in Portland cement to produce expansion and cracking of concrete. In Canada, several investigations of field problems have indicated a much wider occurrence of the phenomenon than was formerly thought to be the case. There are at least two different types of reaction involved. Methods of determining potential alkali-expansivity of concrete aggregate have been well developed and preventive measures have been established that are being used successfully in the field. The extra cost involved is relatively small and, in terms of added life to concrete, may be considered negligible. This paper is a brief review of the present situation in Canada.

The ready-mix concrete producer at times experiences problems with uniformity of his raw materials, and also with secondary properties. Portland cement is no exception. The sources of variations in the properties of Portland cement are discussed in this paper as well as the problems that such variations can create; some solutions to these problems are offered. Particular attention is given to the distinction that should be made between the minimum requirements of a general quality specification and the more rigid requirements of a purchase specification. Also noted is the accessibility of test data on secondary properties from the cement manufacturer.

This paper presents a review of literature on the use of electrical resistance strain gauges on concrete. Type of gauge, surface preparation, cement type and waterproofing techniques are tabulated. Investigations into the effect of aggregate size are reported and conclusions drawn in a preliminary way. A separate bibliography on Strain Gauges and Their Application 1940 to 1964 and a second bibliography on Electric Resistance Strain Gauges Applied to Concrete Surfaces have been combined in this publication., Cette communication présente une revue de la littérature sur l'usuage des appareils à mesurer les déformations unitaires sur le béton par résistance électrique. Le genre d' instruments, la préparation de la surface, le genere de ciment et les techniques d'étanchéité sont catalogués. Des résultats d'études sur l'effet de la grosseur de l'agrégat sone rapportés et certaines conclusions sont établies d'une facon préliminaire. Une bibliographie séparée sur les instruments à mesurer les déformations unitaires et leur application de 1940 à 1964 et une deuxième bibliographie sur ces instruments à résistance électrique appliquée aux surfaces de béton ont été combinées dans cette publication.

The mechanical properties of hydrated Portland cement, are largely dependent on its pore structure. This paper describes these relationships and shows the difficulties in firmly establishing them because of (a) the instability of the material under any form of stress and drying and (b) the existence of interlayer spaces which play an important part in volume stability and elastic moduli of the material. A new technique, the helium flow method, is described, where relative changes to the dimensions of very small pores, due to removal of sorbed water may be traced. This technique involves measuring the flow of helium as a function of time into the vacated spaces of the material as water is removed and returned. Simultaneously, volume change, porosity and density of the material are measured as a function of weight change. Results obtained by this technique are presented showing the unique behaviour of this "porosity" and how density of the sorbed water can be computed. Results that show the effect of this "porosity" on Young's modulus are also presented., RILEM/IUPAC 1973 International Symposium on Pore Structure and Properties of Materials, September 18, 1973, Prague, Czechoslovakia

Recent findings in DBR and other laboratories has made it necessary here to revise the accepted model for hydrated portland cement paste. The model recognizes surface areas and porosities obtained by N2 adsorption as the most reliable values, and attributes many of the phenomena observed, to the behaviour of interlayer hydrate water. The bonds between and within individual “crystallites» are clearly defined; it is shown that the “inter-crystallite” bonds do not separate when exposed to physically adsorbed water. The paper describes some of the thermodynamic equations pertinent to the phenomena of adsorption, length change and creep, and some basic principles governing physical adsorption and types of hystereses. The results were obtained from two areas of work: A. Surface chemical experiments. B. Measurement of mechanical properties of compacted and cast systems of hydrated cement and gypsum. The experiments in (A) included sorption and length change scanning isotherms of water and methanol and led to the following conclusions: The experiments in (B) included measurements of modulus and strength versus relative humidity, and porosity, and led to the following conclusions

The practice of regarding the thermal properties of concrete as constants may lead to serious errors in heat flow calculations. Because of the physicochemical instability of concrete it is very difficult to procure valid experimental information. In this paper theoretical considerations are presented which, together with some experimental data, will make the assessment of the thermal properties of concrete possible. The calculation procedure is illustrated by examples., 5th International Symposium on the Chemistry of Cement: 1968, Tokyo, Japan

The Division of Building Research has investigated, in the field, the leading "system housing" advances in urban building in Northern Europe. The results of these studies are already being used by some Canadian builders of large multi-family housing complexes and there is a rapidly developing interest in the subject. "System building" developments raise the critical question of precision in the manufacture of large-panel components, especially when these are highly prefinished and are assembled to form almost the complete building. This paper concerns the extensive statistical sampling of dimensional control and on problems in system building, by the consulting engineering firm Rastor OY, in Helsinki, Finland.

This paper presents a quantitative interpretation of results of differential thermal analysis of hydration reactions at 2, 12, 23 and 52 degrees C of 3CaO.Al[2]O[3] mixed with 0, 0. 25, 2.5, 10 or 20% gypsum, and compares these with length changes obtained from the hydration of compacts of these mixtures. Estimates of the relative reaction rates from d.t. a. peak areas and measurement of length change during these reactions showed marked agreement, although interpretation had to be made with caution. It was concluded that the formation of ettringite (high sulpho-aluminate) had no direct effect upon reaction rate, but that the reactivity of 3CaO.Al[2]O[3] was reduced by the sorption of (SO[4])[2-] ions on active sites of its surface. Gypsum reduces the rate of conversion of the hexagonal hydro-aluminates to the cubic hexahydrate, probably also by sorption of (SO[4])[2-] ions, and thus is a second mechanism by which they can retard the normal hydration of 3CaO.Al[2]O[3]. The degree to which a given addition of gypsum retards the hydration of 3CaO.Al[2]O[3] at a particular temperature is affected by a balance between (1) the concentration of (SO[4])[2-] ions on and around the surface of the 3CaO.Al[2]O[3]; (2) the rate of reaction of (SO[4])[2-] ions with the hexagonal hydroaluminates; (3) the thickness of the hexagonal hydroaluminate layer around the 3CaO.Al[2]O[3] grain. Reactions at the various temperatures are discussed in terms of the above parameters.