Non-isothermal thermokinetic of cement hardening

Thermokinetic analysis of cements hydration under nonisothermal conditions was performed. The influence of the application moment, intensity and duration of heat effect on the velocity and completeness of the character of hydration was estimated.     

Thermokinetic features of the early stages of hydration of slag alkaline binders

This paper presents results of thermokinetic studies on the early stages of hydration of some slag minerals, slag alkaline binders of traditional and new-generation compounds. A possibility of adjustment and control of hardening processes through thermokinetic indices of hydration (intensity and completeness of heat evolution) for various compounds, types and quantities of the alkaline components and temperatures is proved.     

Calorimetry in the science of building materials

A new conceptual approach is proposed for evaluation of the most important properties of cement-containing composites on the basis of the rate and degree off completeness of hardening processes and study of the porous structure during material formation, within the limits of the system “composition-structure-process-property”.     

Calorimetric Study of Frost Attack During Cement Hardening

This report deals with practical and experimental studies of the effects of frost attack on hardening cement stone and concrete. The basic component of concrete, cement stone, is a typical capillary-porous material formed from solid, liquid and gaseous phases. The level of knowledge on the effects of frost attack on cement stone and concrete hardening is insufficient, due to the complexity of the mechanisms of the accompanying effects. The values of internal pressures are determined among others by ice formation parameters, by the characteristics of the porous structure and the solid phase of the cement stone, and also by technological factors. The quantitative estimation of certain parameters is important for an approach to the understanding of the mechanism of frost attack and the choice of methods of its regulation for technological purposes. These are the temperature of pore liquid crystallization T _f, the degree of freezing F _d and the mass of ice I _m formed during freezing. Examples of changes in ice formation parameters on variation of some of the technological factors are given. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies of Capillary Porosity of Clinker Phases During Hydration

The capillary porosity of clinker phases, i.e. 3CaOSiO₂, β2CaOSiO₂, 3CaOAl₂O₃ and 4CaOAl₂O₃Fe₂O₃, at the early stages of hydration has been studied by the methods of Differential Scanning Calorimetry and nitrogen adsorption (BET). It was established that pores of 3–70 nm were formed during the hydration of 3CaOSiO₂ and the maximum of their distribution was found at about 10 nm. The hydration of 2CaOSiO₂ is much slower and the porosity is one order of magnitude lower. During the hydration of 3CaOAl₂O₃ the content of crystalline hexagonal hydrates prevailed and the porosity was in the range 5–90 nm with the average pore diameter of about 16 nm. This average pore diameter was much smaller for thermoporosimetry and lay at about 7 nm. The hydrated 4CaOAl₂O₃Fe₂O₃ sample had the porosity in the range 3–90 nm with the maximum of the pores distribution at about 4 nm. There are some differences between the porosities measured by BET and thermoporosimetry. Principally thermoporosimetry gives no information about larger capillary pores in the range 30–50 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between the Structure of Cement Stone and the Parameters of Ice Formation during Stone Freezing

The specific features of ice formation during freezing of hardening binders are considered as dependent on the structural characteristics. The theoretical grounds for the relationship between the crystallization point of the pore-confined liquid and the pore size are discussed. The possible mechanisms of frost-caused cement stone destruction and the conditions of their development are considered. A model is proposed for estimating the danger of ice formation. The results of experimental studies are given for ice formation during freezing of tricalcium silicate and tricalcium aluminate. The parameters of ice formation are shown to be interrelated with the properties of the porous structure formed during hardening of these binders. The laws characterizing the degree of danger due to ice formation during freezing of cement stone are established.     

Calorimetric Studies of Hydration of Cementitious Materials Varying in Basicity

This paper presents results of thermochemical and thermokinetic studies of the hydration of portland cement, alkaline cements with mineral additives and slag alkaline binder. The influence of the modulus of basicity of the binders on the thermochemical and thermokinetic characteristics of hydration was estimated. This revised version was published online in August 2006 with corrections to the Cover Date.