Ceramic pigments in the RO-(Co,Ni)O-TiO2 system
Six compositions, placed in the RO-(Co,Ni)O-TiO2 system where R2+ represents Ca2+, Sr2+, Ba2+ are synthesised in this work. The compositions were chosen so that at firing temperature to form the perovskite lattice. Cobalt and nickel oxides were used as cromophors in such quantities as to form theoretically 20% CoTiO3 and 30% NiTiO3. The samples are fired at 12500C and their mineralogical composition was examined by X-ray diffraction. The mechanism of solid-state reactions and the solid solution formation were studied. The chromatic characterization of samples was realised by electronic spectra and CIE Lab method.
Isomorphy relationships - theoretical base for rational elaboration of oxide composition
There have been approached the isomorphy relationships, very frequent among the oxide compounds, underlining the importance of knowing and using them for a rational elaboration of the make recipes. In the paper there are given some examples of isomorphy relationships, which represent the starting point in obtaining some thermoresistant pigments based on different structures: spinel (ZnAl2-xCrxO4), baddelayite (Zr1-2xVx5+Rx3+O2 where R3+=Y3+, In3+, Ga3+, Bi3+), zircon(Zr1-xVx4+SiO4 respectivelyZr1-xPrx4+SiO4), malayaite ( ) and some perovskite compounds. The isomorphous substitutions represent the basis of the obtainment of oxide compounds with tailored properties.
Behaviour of Portland cement with slag under acid corrosion with formation of soluble products
The stability of the building materials to the action of different physical and chemical agents in the natural and technological conditions in which the constructions are exploited represents one of the major concerns in order to insure their durability. The acid corrosion occurs below the pH of 6.5, and may originate from: (i) acid rains, increasingly frequent over the last decades and caused by SO2 and NOx emissions leading to formation of H2SO4 and HNO3; and (ii) the life and service of industrial structures in acid-generating mediums.
The paper aimed at studying the behavior of a CEM II/A-S type cement with 17.4 % blast furnace slag. The cement samples prepared pastes and mortars were kept in water for 28 days, then submitted for 180 days to the corrosive action of four soluble interaction products forming acids.
Two inorganic acids HCl and HNO3 and two organic acids HCOOH and CH3COOH were used. During the acid solution cure, chemical, physico-mechanical and XRD analyses were carried out. The compressive strength underwent decreases at all terms, more significant for the samples cured in the HCl and CH3COOH solutions. The chemical analysis proved the advanced decalcification of the corroded layers and that this type of corrosion doesnt take place in the core of the samples but the at the corrosion products layer - uncorroded core interface.
Expansive binders type M - first time realized by Mihailov- are obtained by mixing Portland cement with an expansive addition consisting of aluminate cement and gypsum. The ettringit formation, associated with expansion, assume the participation of aluminous compounds, CA and C12A7 of aluminate cement, and calcium hydroxide resulted by the hydration of Portland cement, with gypsum.
In this context, the blended binders, containing Portland cement as principal binder and an expansive addition consisting of high alumina cement, gypsum and calcium hydroxide (necessary because of low basicity of high alumina cement), can be consider expansive binders type M.
The present paper brings information regarding the hardening and expansion of such binding mixtures, in which the proportion of expansive addition ranged between 5% and 20%. The humidity of the environment (humidity saturated atmosphere and laboratory atmosphere), in correlation with the proportion of expansive addition exerted a significant influence on the expansion and, of course, on the amount of ettringite formed. In the first days of hardening, the expansion had low values, which determine the consideration of such binders like shrinkage-compensating cements; the mechanical strength determinations approved it.
The distribution of phosphorus from bone meal between silicate phases of Portland cement clinker
Meat and bone meal (MBM) can be used in clinker manufacture as a secondary fuel together with the conventional one. The substititution level of conventional fuel with the secondary one reached up to know was maximum 20 %. The high MBM content of phosphate raises problems regarding the incorporation of ash in the main clinker mineralogical phases. The aim of this paper was to determine the incorporation amount of phosphorus in Portland clinker minerals when MBM ash is added to the clinker raw material. The influence of this addition on the clinkering reactions was evaluated as well as the incorporation of phosphorus in alite and belite. Samples were prepared by additions from 0.07 to 0.88 wt.% of MBM ash to an industrial clinker raw material. The following techniques were applied to characterize the raw materials and the obtained clinkers: chemical analysis, selective dissolution of interstitial phase, X-ray diffraction and scanning electron microscopy. Selective dissolution of interstitial phase was performed in order to find out the amount of phosphorus incorporated in the silicate phases. The results led to the conclusion that addition of up to 0.88 wt. % MBM ash leads to decomposition of alite and consequently to an increase amount of free lime. The results of X-ray microanalysis show that the amount of P2O5 incorporated in belite is approximately two times higher than that in the alite.
One of the major requirements for ensuring cement concrete with good performance in time is the selection of the type of cement with allowance for the ensuing effect the respective cement intergrinding admixture has on the concrete characteristics. In the case of cement type II/A-V and II/B-V, including fly ash, the cement performance parameters relate directly to the quality of the fly ash and the cement processing conditions. The paper presents process engineering solutions to be applied in power plants in order to improve the quality of the fly ash, as well as process engineering solutions to be applied in cement production in order to obtain cement type II/A-V and II/B-V.
Glass is an essential material in the context of the present civilization. Like for all other artificial materials the huge industrial production of glass in the last century determined the increase of the preoccupation concerning their influence on human health and generally on biosphere. A scheme representing the main glass categories show that glass mass products are chemically inoffensive and only few glass compositions are really dangerous. Some unpleasant side effects related, for example, to the spreading of cullets in nature, can be removed in a great measure. There are also some glass categories useful for human health or contributing to the immobilization of harmful wastes. So, glass may be considered a friendly material. The positive and negative effects of glasses on living world, sometime very important and interesting, continue to deserve attention. The study of glass categories with benefic, sometime miraculous, effects on living organisms deserves to be strongly encouraged. Some solutions for the unpleasant side effects, elaborated worldwide and in our laboratory, are evidenced.
This paper represents the results of several stages of complex, interdisciplinary researches on working and exploitation activities of mineral resources for the building materials, more especially for the building ceramics. It also represents a part of the results of the researches on the life cycle of some products resulting from the exploitation of some clayey mineral resources for the building ceramics, the influence on the environment factors and measures for protection of the latter and the implementation of a performing system of environment management within a company in the field of building ceramics.
The results obtained may constitute a model for such a research and working system and show that by the exploitation and manufacture of products at a competitive level, the activity of a company with a major impact in this field can comply with the complex quality and environment management and provide the area with a log time and durable development.