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Abstract
MDF cements using the blends of sulfoaluminate ferrite belite (SAFB) clinkers and ordinary Portland cement (OPC) in mass ratio 85:15 with Al2O3, and starch, polyphosphate (poly-P) or butylacrylate/acrylonitrile were subjected to moist atmospheres (ambient, 52 and 100% relative humidity (RH)) to investigate their moisture resistance. Their chemical, thermal, electron microscopic and magnetic properties were also studied before and after moisture attack. Butylacrylate/acrylonitrile (BA/AN) copolymer was found to be the most suitable for MDF cement synthesis since the sample containing BA/AN showed the best moisture resistant. There are significant differences in scanning electron microscopy (SEM) of MDF cements before and after moisture attack and with different polymers. New data on the paramagnetic nonhysteresis magnetization curves for all the samples are observed. The MDF cements synthesized from SAFB clinker with dissolved poly-P give the best signal/noise (S/N) ratio. Three main temperature regions on TG curves of both series of MDF cements are observed. In the inter-phase section of MDF cements, the content of classical cement hydrates decomposing by 250C is increased. Combustion of organic material took place by 550C. In the temperature range 550-800C, the decomposition of CaCO3 occurs.
Abstract
Methods of thermal analysis are employed in a study of the high-temperature properties of three different types of glass fiber reinforced cement composites together with the measurements of their thermal and hygric parameters. First, basic TG and DTG measurements are carried out to get the first insight into the high-temperature behavior of the analyzed materials. Then, mercury porosimetry and scanning electron microscopy of specimens subjected to the temperatures of 600 and 800C are performed and compared to the reference specimens not exposed to any thermal load. Finally, measurements of thermal and hygric parameters of the studied materials are done and matched with the results of the material characterization experiments. Three main effects are found to influence the thermal and hygric properties of the analyzed materials. The first is the decomposition of the cement matrix, which is clearly a negative factor. The second is the positive effect of the presence of fibers that could partially keep the cement matrix together even after significant decomposition of cement hydration products. The third important factor affecting the thermal and hygric properties is the composition of the particular materials. The application of vermiculite aggregates instead of sand is found to be clearly positive because of its porous character leading to the bulk density decrease without worsening the other properties. Also, wollastonite aggregates are a better choice than sand because of its fibrous character that could partially magnify the effect of fiber reinforcement.
Abstract
This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or siliceous and aluminous materials according to the ASTM C 618-94a. The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine fineness range, the reactive alumina (Al2O3 r−) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO2 r−) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is due primarily to the chemical interaction between the gypsum and the C3A in the Portland cement and the reactive alumina (Al2O3 r−) in the fly ash.
Abstract
Prof. Wojciech Zielenkiewicz was born in Warsaw on 6 June 1933. He studied chemistry at the Warsaw University and graduated in 1955. His master thesis in the field of nuclear chemistry dealt with the enrichment of bromobenzene by the Szilard-Chalmers method. Since 1955 his professional career has mostly been related to the Institute of Physical Chemistry of the Polish Academy of Sciences (PAS) founded in the same year. Initially, Wojciech Zielenkiewicz worked under the supervision of Prof. Wojciech Świętosławski. This cooperation had a powerful influence on Zielenkiewicz both as a researcher and as a person. His strong interest in thermochemistry at that time resulted partly from his research interest and partly from his attraction to one of the students doing her diploma who later became his wife. Zielenkiewicz’s PhD thesis carried out under Świętosławski’s supervision concerned the thermochemistry of cement hydration. For the purposes of this work, Zielenkiewicz constructed his first calorimeter – a labyrinth flow calorimeter which was a modified version of the first such calorimeter constructed by Świętosławski and Malawski in 1935. The calorimeter was applied for the determination of the heat of cement hardening. After his PhD, Zielenkiewicz worked on several other calorimeters for the study of heat of cement hydration with the quasi-adiabatic method as well as on ‘conduction’ calorimeters for the examination of the first phase of cement hydration. This activity resulted in a monograph Calorimetry and Thermochemistry of Cement written in collaboration with T. Krupa and published in 1975. In the following years, his scientific interests were focused mostly on various aspects of the transfer of heat energy in time, i.e. thermokinetics. He constructed a number of calorimeters for this type of measurements and, together with his co-workers, elaborated new numerical methods of determination of thermokinetics. Those methods were assessed at international symposia on thermokinetics organised by Zielenkiewicz in cooperation with the French Association of Calorimetry and Thermal Analysis (AFCAT). In this period, he established regular cooperation with scientists from France, Spain, and the USA. Research on thermokinetics includes not only theoretical studies but also experimental works. Most of the experiments conducted at the Department of Calorimetry headed by Prof. Zielenkiewicz were connected with inclusion compounds, particularly Werner complexes as well as porfyrine derivatives. In the last twenty years, Zielenkiewicz conducted research in the scope of biomolecules. The study resulted in the determination of thermodynamic properties of over 60 derivatives of nucleic acid bases and the establishment of new correlations between enthalpic, volume, and structural properties of the compounds examined. His most recent interests concerned the study of enthalpic processes of protein salting. Zielenkiewicz’s long and intensive work in the field of calorimetry and thermokinetics has appeared in numerous books and publications presenting his research results. He is the author of 7 monographs, a number of chapters in a monograph and about 200 scientific publications. They include, among others, Analysis of Course of Heat Effect in n-n Calorimeters, Signal Processing of Calorimetric System, Dynamic Theory (later translated into Russian and published in Russia), Advances in Calorimetry and Thermochemistry, Theory of Calorimetry written together with E. Margas and published in 2002 by Kluwer and the most recent book, Calorimetry, published in 2005. Prof. Zielenkiewicz has also been active as a supervisor. He assisted and supported the realisation of 14 completed PhD theses of the employees at the Institute of Physical Chemistry and is supervising 3 more students of the Institute. Moreover, he has been involved in the realization of several more PhD theses both in Poland and abroad. For many years Prof. Zielenkiewicz combined his activity on research with research coordination. He managed the organizational units of the Polish Academy of Sciences as the Director General of the PAS and as a Deputy Scientific Secretary. For 6 years he was a Scientific Secretary of the Division of Mathematical, Physical and Chemical Sciences of PAS. In the years 1968–2003 he headed the Laboratory and Department of Calorimetry and he was a director of the Institute of Physical Chemistry for 19 years. His directorship in the Institute happened in a very difficult period for Poland, i.e. when the Marshall Law was introduced in 1981. As numerous employees of the Institute were involved in the illegal Solidarity movement at that time, the position of a director of such an institution was extremely uncomfortable and required great abilities in dealing with the communist authorities in such a way as to protect those employees. It must be said that Prof. Zielenkiewicz faced this challenge with success. Prof. Zielenkiewicz was also an initiator of the Polish conferences on calorimetry and thermal analysis. The first one was held over 30 years ago. These conferences created an opportunity for Polish researchers to exchange their opinions and learn about the world research trends. Numerous outstanding scientists were guests at these conferences. Many of them are members of the Polish Society of Calorimetry and Thermal Analysis. Prof. Zielenkiewicz has been awarded many state and foreign medals and distinctions, among others, Wojciech Świętosł;awski’s Medal and the Calvet Award given by the French Association of Calorimetry and Thermal Analysis (AFCAT) as well as the most prominent Polish state orders including the Order of Polonia Restituta (the Knight’s Cross) and the Order of Labour Banner. He is a corresponding member of the Polish Academy of Sciences and the Royal Academy of Sciences in Barcelona. Dr. Paweł Gierycz
Early stages hydration of high initial strength Portland cement
Part I. thermogravimetric analysis on calcined mass basis
in order to eliminate the residual non combined free water [ 16 ]. As during these drying steps the water/cement ratio is decreased significantly, which decreases the cement hydration rate, any possible little acceleration during drying was considered
33 245 253 Pacewska B., Wiliska I., Bukowska M., Nocu-Wczelik W. Effect of waste aluminosilicate material on cement hydration and properties of
catalyst reacts with calcium hydroxide (a product of cement hydration) as a pozzolanic material [ 5 – 7 ]; in the compositions with calcium aluminate cements the FCC catalyst is an active additive [ 8 ]. The authors, investigating Portland cement
. Weyer , HJ , Muller , I , Schmitt , B , Bosbach , D , Putnis , A . 2005 . Time-resolved monitoring of cement hydration: influence of cellulose ethers on hydration kinetics . Nucl Instrum Methods B . 238 4 102 – 106 10.1016/j.nimb.2005
have been found very few references. Dweck et al. [ 14 ] present a method to study cement hydration at ambient temperatures by using a micro processes non-conventional DTA system. Criado et al. [ 15 ] develop an alternative method applied to
replacement of 10 wt% cement with zeolite (mortars B and D) changes the cement hydration. Thus, hillebrandite and xonotlite have not been indicated in samples cured for 120 days in water, which may be explained by partial consumption of hydroxyl ions by
