Showing 3 results for Setting Time
A. Allahverdi, E. Najafi Kani, S. Esmaeilpoor,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: The use of alkali-activated cementitious materials especially over the past decades has
significantly been increased. The goal of this research is to investigate the effects of silica modulus
and alkali concentration on alkali-activation of blast-furnace slag. In this research, the most
important physical characteristics of cementitious systems, i.e. the 28-day compressive strength
and final setting time, were studied by changing influencing parameters such as silica modulus,
i.e. SiO2/Na2O, (0.44, 0.52, 0.60, and 0.68) and Na2O concentration (4, 6, 8 and 10% by weight of
dry binder) at a constant water-to-dry binder ratio of 0.25. Final setting time of the studied
systems varies in the range between 55-386 minutes. The obtained results show that systems cured
at an atmosphere of more than 95% relative humidity at room temperature exhibit relatively high
28-day compressive strengths up to 107 MPa.
S. H. Razavi, Sh. Mirdamadi, M. M. Hormozi,
Volume 8, Issue 1 (3-2011)
Abstract
Abstract: The aim of the present investigation is to study the physical and mechanical characteristics of dental-filling spherical high-copper and silver amalgams and to compare them with a common high-copper domestic unicompositional amalgam. In this study, cylindrical specimens were mechanically condensed according to the ISO 1559:1986 Standard in order to measure the compressive strength, Vickers hardness, static creep and dimensional change on setting. Adding more silver to the amalgam increased its compressive strength, creep resistance and reduced mercury vapor. After 1, 24 and 168h of amalgamation and Modulus of elasticity of specimen S1, the mean hardness and compressive fracture strength were significantly lower than those of . No significant differences were identified for the two alloys in the creep and dimensional changes on setting. It can be concluded that as far as the mechanical properties or corrosion resistance is concerned, the amalgam should be comprised of at least one spherical alloy.
E. Najafi Kani, M. Nejan, A. Allahverdi,
Volume 13, Issue 4 (12-2016)
Abstract
This article addresses the interplay between heat of hydration and physico-mechanical properties of calcium sulfate hemi-hydrate in the presence of retarding additives such as citric and malic acids and sodium citrate. The heat of hydration was measured using a semi-isothermal calorimeter. Results proved that citric and malic acids had superior impact on hydration and mechanical properties. While the concentration of additives was increasing, the maximum heat of hydration was decreasing from 56.15 cal/g.min for blank sample to 33 cal/g.min for high concentrations of citric and malic acids. Consequently, the measured time to this maximum heat of hydration and thus the induction period were increased significantly from 5 to 105 min. Mechanical results indicated that the increase in the amounts of additive led to the reduction of the compressive strength from 16.25 MPa in the blank sample up to 74% for the highest concentration of malic acid
