Showing papers in "Cement and Concrete Research in 1975"

TL;DR: A brief overview of the physicochemical basis for alkali-silica reactions is given in this article, where the rates at which these reach the pore solution phase are discussed, and data indicating that concentrations as high as 0.7 molar may be attained in a month or so and maintained indefinitely are discussed.

TL;DR: In this paper, measurements of compressive strength, modulus of elasticity, and microhardness were made on magnesium oxychloride cement systems having a wide range of porosity.

TL;DR: In this paper, a combination of scanning electron microscope, energy dispersive X-ray spectrometer and computer, quantitative analyses of microvolumes of alkali-silica gel at the reaction site and in cracks in concrete were carried out.

TL;DR: In this article, it was shown that water of more than 30 H2O molecules are present not only in the crystal internal channels, as can be concluded from A.E. Moore's and H.F.W. Taylor's data, but also in crystal defects and is adsorbed on the surfaces of the crystals.

TL;DR: In this article, a mixture of CaO and colloidal silica with and without γ-Al2O3, CaO, and alkali-bearing Al 2O3-SiO2 gels were treated hydrothermally at 90°C or 120°C for 4 hours to 4 weeks.

TL;DR: In this paper, it was shown that from the trigonal prisms (n = 30−18) the structure of the ettringite crystals is maintained; from the main apices (n=18−6) - crystals become roentgenoamorphous, but their sign of elongation alters and ends are destructed; from 6−0 - longitudinal and transverse ruptures appear and the crystals disintegrate.

TL;DR: The pozzolanic activity of pulverized fuel ash (p.f.a.) has been determined by measuring the rate of dissolution of silica from p.a. in 0.1 M hydrofluoric acid as mentioned in this paper.

TL;DR: In this paper, a spectrum of linear log mechanical properties (i.e., compressive strength, modulus of elasticity, and microhardness) were measured on a variety of autoclaved cement-silica preparations covering a wide range of porosity.

TL;DR: In this paper, it has been demonstrated that porosity is by far the dominant controlling factor limiting strength of hydrated cement paste, and a new relationship to describe the interrelation of strength and porosity was given, and the effect of maturity of specimens, composition and microstructure are illustrated.

TL;DR: In this paper, the rapid deterioration in a sulphate solution at 5°C of autoclaved mortar made with portland cement and dolomitic aggregate is explained and the presence of thaumasite in such mortars and its preparation are discussed.

TL;DR: In this paper, the Debye-Huckel theory was applied to the solubility of calcium hydroxide by Greenberg and Copeland to permit calculation of the ion concentration in solutions of high ionic strength and high alkalinity, such as are present in the pores of hardened cement paste and concrete.

TL;DR: In this paper, the absorption of microwaves by hardened cement paste has been studied in the frequency range of 8.5 GHz to 12.3 GHz (x-band) using the free wave method.

TL;DR: In this paper, the fracture of ordinary and polymer-impregnated concrete has been studied by high-speed photography, where 20-40 mm thick concrete prisms were subjected to a dynamic loading by detonation of a high explosive in contact with the top surface of the specimen.

TL;DR: In this article, the influence of steel fiber reinforcement on the onset of cracking, ductility and energy absorption capacity in flexure is reported, and the automatic load-deflection curve predicts a consistently higher load for the start of cracking than those obtained from strain, pulse velocity and deflection measurements.

TL;DR: In this paper, the effect of compressive stress on the porosity and density changes of a series of mortar specimens and a set of cement paste specimens subjected to various compressive stresses histories during desorption and sorption cycles was investigated.

TL;DR: In tunnels sulphate damage was detected in the concrete lining by X-ray analysis from the needles showed diffraction values from a t h a u m a s a s i t e as mentioned in this paper, which is remarkable that the formula contains a relatively high level of SiO2 and little SO3 and CO2.

TL;DR: In this paper, the effect of admixtures of several types on the volume change characteristics of portland cement pastes is reported, and it is suggested that the effect is mainly one of degree of dispersion in terms of alignment of sheets and displacement of ends of sheets.

TL;DR: Mercury porosimetry tests have been made on four different particle sizes of the same mature hardened cement paste, w/c = 0.40 as mentioned in this paper, and the pore volume penetrated by mercury appears to be independent of particle size.

TL;DR: In this paper, it was established that the higher ultimate strength of fly-ash cements as compared to plain Portland ones can be attributed to the tobermorite-like secondary microcrystalline phase formed in the period from 1 to 3 months, depending on the quality and activity of the flyash used.

TL;DR: In this paper, the effects of CaCl2, calcium gluconate, mixture of caCl2 and calcinellum, glucose, and mixture of glucose and calcanellum on the hydration of three different portland cements have been studied using isothermal microcalorimetry, x-ray diffraction, chemical analysis of the liquid phase and differential thermal analyses.

TL;DR: In this article, simultaneous heating and pressing techniques were applied to ordinary calcium aluminate cements (40% Al2O3) and high aluminate (72%) cement, and the compressive strength of the former, when hot pressed at 50, 000 psi, 250°C, 1 2 hr.

TL;DR: In this article, the CEB International Recommendations for unit creep curves for various ages t′ at loading are approximated in the form f(t-t')+g(t)-g(T)-g (t)-t)-G(t') where t = time.

TL;DR: In this article, the effects of waste solids on compressive and tensile strength, setting time, shrinkage and sulfate expansion and workability of ready-mix concrete are investigated.

TL;DR: In this article, the authors examined some badly deteriorated soil cement pavement base materials which had been in contact with ground water containing about 2000 ppm SO3 and found that the deterioration was caused by expansion due to formation of the fibrous phase, apparently the result of prolonged contact of this particular soil-cement with high sulfate content ground water and possibly affected also by the high dolomite content of the soil.

TL;DR: The hydrated cement paste of an 84 year old reinforced concrete bridge construction has been examined for its composition and microstructure by means of chemical analysis, SEM, X-ray diffraction analysis and thermal analysis.

TL;DR: In this article, the correlation between the permeability and the strength of concrete was studied by means of new methods of measuring the air and water in concrete. But the scatter of the results is rather large, probably due to the heterogeneous character of concrete containing aggregate particles which are large in comparison with the test cavity.

TL;DR: In this article, a sufficient quantity of Icelandic natural pozzolans can prevent damaging expansion in concretes with reactive aggregates, due to the low average temperatures in Iceland, the risk of alkali expansion is diminished.

TL;DR: In this paper, the influence of the shrinkage of portland cement on concrete was investigated and it was shown that the formation of ettringite is an important link in the mechanism of shrinkage in the plastic stage of cement paste and mortar.

TL;DR: In this article, the corrosion behavior of reinforcing steel embedded in various slag cement pastes was studied using the galvanostatic polarization technique, and the results obtained were supported by corrosion rates obtained using the linear polarization technique.