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1、Frost damage, which is the deterioration due to freeze and thaw of pore soln. is causes scaling, pop-out and cracks on surface of concrete members, is an important issue in the durability of concrete structures in cold regions. Deicing agents are sprayed in order to prevent frost damage. By contrast, it has been reported that chlorides of deicing agents accelerate the deterioration due to frost damage under freeze-thaw environment. It is generally known that phase changes of hydration products, such as formation of friedel's salt and ettringite, occur due to penetration of chloride ion. Ettringite formation leads vol. expansion and cracks. Since the acceleration of frost damage due to chlorides penetration, the use of deicing agents which is not contg. chloride ions, such as potassium acetate and calciummagnesium acetate, has been proposing. However, it has not been shown that chem. alteration due to penetration of deicing agents influence on increase of strain and decrease of structural characteristic value with frost damage under freeze-thaw environment. Therefore, this study aimed to investigate the influence of deicing agents under freeze-thaw environment on 1) progress of frost damage, 2) phase changes of hydration products and 3) decrease of structural characteristic value. As the results, 1) penetration of deicing agents contg. chloride ions influenced on the strain hysteresis and resulted in the increase of residual strain and water absorbing ratio, 2) ettringite formation with displacement and dissoln. of monosulfate hydrates was a contributory factor for frost damage acceleration and 3) chem. alteration and increase of residual strain due to penetration of chlorides led decrease of tensile strength, elastic modulus and fractural energy. 2、The effect of metals in fly ash on the dechlorination reaction which occurs in bag filters installed in municipal waste incinerators and melting furnaces has not been previously assessed. Tricalcium aluminate (3CaO·Al2O3, C3A), considered a precursor of complex oxychlorides, and its reaction with HCl was examd. in a gas flow reactor under simulated bag filter conditions (473° K, 1000 ppm HCl, 30 vol. percent water, 5 vol. percent O2). The C3A molar chlorination ratio leveled off at ~1 after 24 h. The C3A chlorination reaction rate was similar to that of Ca(OH)2. C3A chlorination products had a mainly amorphous structure. Elemental mapping images of the chlorinated C3A surface indicated the likely generation of complex Ca and Al oxychlorides. It is possible that complex oxychlorides are produced in bag filters from complex oxides generated by high temp. incinerators. 3、This paper reports the results of a study to det. the effects of supplementary cementitious materials (SCMs) on the chloride binding of portland cement pastes. The results show that SCMs with significant quantities of alumina increase the binding capacity of cement paste. Pastes with metakaolin (45% Al2O3) showed the greatest chloride binding capacity and pastes with silica fume (<0.5% Al2O3) showed the least binding. The chem. binding in solns. of high chloride concn. is mainly attributed to the formation of Friedel's salt, C3A·CaCl2·10H2O. When pastes originally exposed to high chloride concns. are subsequently exposed to chloride-free soln., a portion of the bound chloride is released, but a significant portion remains irreversibly bound. There is some evidence that Friedel's salt may partially convert to Kuzel's salt, C3A·(0.5CaCl2)(0.5CaSO4)·12H2O, under these conditions. The binding relationships were best described by the Freundlich isotherm and binding coeffs. are given for all the binders tested. 4、We investigated the performance of Friedel's salt (FS: 3CaO·Al2O3·CaCl2·10H2O), a layered double hydroxide, as an adsorbent for As removal from aq. soln. Friedel's salt was prepd. at lower temp. (50°) compared to traditional autoclave methods by reaction of calcium chloride with sodium aluminate. Kinetic study revealed that adsorption of arsenate by Friedel's salt was fast in the first 12 h and equil. was achieved within 48 h. The adsorption kinetics are well described by second-order Lageren equation. The adsorption capacity of the prepd. sorbent for arsenate at pH 4 and 7 calcd. from Langmuir adsorption isotherms was 11.85 and 7.80 mg/g, resp. Phosphate and silicate markedly decreased the removal of arsenate, esp. at higher pH, but sulfate was found to suppress arsenate adsorption at lower pH and the adverse effect was disappeared at pH 3 6. Common metal cations (Ca2+, Mg2+) enhanced arsenate adsorption. Thus, Friedel's salt is a potential cost-effective adsorbent for arsenate removal in water treatment. 5、When CaO·2Al2O3 was mixed to ordinary portland cement, 3CaO·Al2O3Ca(OH)2·12H2O has formed a large amt. of in hardened cement by the reaction of CaO·2Al2O3 and Portlandite. Amt. of portlandite was formed in hardened cement has decreased with increased of amt. of CaO·2Al2O3, because 3CaO·Al2O3·Ca(OH)2·12H2O formed a large amt. of in hardened cement by the reaction of CaO·2Al2O3 and Portlandite. Amt. of leaching of Portlandite in hardened cement added with CaO·2Al2O3 into NaCl soln. has decreased with increased of amt. of CaO·2Al2O3. When CaO·2Al2O3 was mixed to ordinary portland cement, Penetration of chloride ion into hardened cement was decelerated compared with hardened ordinary portland cement because formation of Friedel's salt for the reaction of 3CaO·Al2O3·Ca(OH)2·12H2O and chloride ion. When CaO·2Al2O3 was mixed to ordinary portland cement, amt. of fixed chloride ion has increased and ratio of sol. chloride ion in total chloride ion has decreased in hardened cement. This reasons was chem. effect of fixation of chloride ion by formation of Friedel's salt for the reaction of 3CaO·Al2O3·Ca(OH)2·12H2O and chloride ion. 6、A chem. model for the soly. of Friedel's salt (FS, 3CaO·Al2O3·CaCl2·10H2O) was developed. The model was built with the help of the OLI platform via regression of exptl. soly. data for FS in the Na-OH-Cl-NO3-H2O systems. The soly. of FS in water was measured using a batch nickel autoclave over the temp. range of 20-200 °C, and the soly. product of FS (log10Ksp) was obtained. The soly. of FS in water shows a max. value as a function of temp. The soly. of FS in 0-5 mol/L NaOH and 0-2.5 mol/L NaCl solns. was found to decrease with increasing NaOH and NaCl concns., because of the common ion effect; however, in 0-2.5 mol/L NaNO3 solns., it was found to increase because of complexation. During the regression anal., it was found that CaOH+ plays an important role in soly. modeling, and its dissocn. const. was detd. by an empirical equation. New Bromley-Zemaitis activity coeff. model parameters for the Ca2+-OH-, CaOH+-OH-, and CaCl+-OH- ion pairs were also regressed, using the exptl. soly. data generated in the present study. The new model was shown to successfully predict the soly. of FS in mixed NaOH + NaNO3 solns. not used in model parametrization. With the aid of the newly developed model, the concn. and temp. effects on calcium species distribution were analyzed. 7、A Spanish hazardous waste from tertiary aluminum industry was used as a raw material for the prepn. of calcium aluminate. An amorphous precursor was obtained by a hydrothermal method at different values of pH. The transformation of the precursor in a cryst. aluminate was followed by TG/DTA up to 1300°. At temps. between 719 and 744 °C, the precursors evolve towards the formation of C12A7 which becomes CA at circa 1016°. Mass spectrometry coupled to thermal analyzer allowed the identification of the decompn. products. 8、Controlling the silica level in Bayer provess liquor is crit. to prevent scaling or alumina quality issues. The conventional method of removing silicates from aluminate solns. requires the introduction of calcium oxide or calcium hydroxide. In this work, Friedel's salt (3CaO·Al2O3·CaCl2·10H2O) removed ￡95% of the silica from sodium aluminate soln. FS is a mineral anion exchanger belonging to the layered double hydroxides which was prepd. by adding calcium chloride to sodium aluminate at 50-90°. The salt was characterized by XRD, SEM, particle size anal. and TG-DSC. FS prepd. at 50° has a relatively high silica removal capacity compared to calcium oxide. Exptl. parameters affecting the silicaremoval process, such as temp., sodium aluminate liquor compn., initial silica concn. (4-10 g/L) and FS dosage were investigated in detail, and a comparison of desilication between FS and CaO was carried out. The desilication products were mainly calcium aluminum silicates, identified by XRD to be Chabazite and Wadalite and the final chloride concn. in the sodium aluminate soln. after anion exchange with FS was ~0.015 g/L. The rate of silica removal by FS was first order with a rate const. 2.582 × 106 min. The apparent activation energy was estd. to be 57.7 kJ/mol at 80-110°. 9、The hydration product Friedel's salt (Ca4Al2O6Cl2.10H2O) is frequently encountered in wasteforms solidified and stabilized using Portland cement. The ability of Friedel's salt to form solid solns. plays a role in chloride binding in such matrixes. This paper addresses one practical example of this influence by examg. the immobilization of chloride ions from municipal solid waste incinerator fly ash in cementitious matrixes also comprising Portland cement and fly ash from coal-fired power generation. Measurements of quantities and structural parameters of Friedel's salt in pastes contg. incinerator fly ashes show that chloride ion release is lowest when large quantities of chloride-deficient Friedel's salt is generated. However, chloride is more tightly bound elsewhere in the material, probably in calcium silicate hydrate (CSH) gel. The dissoln. of Friedel's salt is modelled using a geochem. modeling program capable of dealing with solid solns. These observations reinforce the need to incorporate variable phase compn. in models for predicting leaching from cementitious matrixes contg. waste materials. 10、The studies of the tricalcium aluminate-sulfate system with aim to understand the sequence of the reactions and the limiting stages of C3A hydration in the presence of chlorides were carried out. At first C3A starts to dissolve in contact with the soln. and it leads to the pptn. of a certain quantity of calcium hydroaluminate. At later stage the rate of hydration is controlled by the rate of ettringite formation. In the presence of sodium chloride, the tricalcium aluminate reacts with chloride ions to produce the AFm-type phase C3A·CaCl2· 10H2O (Friedel's salt) from the beginning of reaction. The formation of solid soln. between Friedel's salt and calcium monosulfoaluminate occurs simultaneously. 11、The stable quaternary diagram for the system CaO-Al2O3-CaCl2-H2O at 23±4° has been constructed. Among the phases in this system are the calcium oxychlorides Ca(OH)2.CaCl2.H2O and 3Ca(OH)2.CaCl2.12H2O. The formation of Friedel's salt (FS) and calcium oxychlorides provides a mechanism for chloride binding in Portland cement concrete. The compatibility relationships involving these compds., FS and Ca(OH)2, were established empirically, and 3Ca(OH)2.CaCl2.12H2O was found not to coexist in equil. with FS. The soly. behaviors of these compds. may play a role in affecting temp.-dependent corrosion rates. Addnl., the formation of oxychlorides from solns. contg. elevated concns. of NaCl may provide a mechanism by which ASR is facilitated. 12、A series of slurries contg. Friedel's salt (3CaO.Al2O3.CaCl2.10H2O) in equil. with other solids that include Al(OH)3, Ca(OH)2, and 3CaO.Al2O3.6H2O were produced at room temp. (23±1°). The liq. phases were analyzed for calcium, aluminum, and chlorine, and the speciation program PhreeqC was used to model the equil. that were established between the solid and liq. phases. By matching closely, the exptl. detd. soln. parameters with those calcd. using PhreeqC, important information concerning equil. in the CaO-Al2O3-CaCl2-H2O system was obtained. For example, it was shown that the stable phase pair, Friedel's salt/3CaO·Al2O3·6H2O, acts to buffer against rising chloride concns. by acting as a chloride sink. PhreeqC calcns. have estd. the soly. product of Friedel's salt to fall within the range -28.8<log Ksp<-27.6. 13、The hydration products of Portland cement pastes cured using water contg. tin(II) chloride have been compared with those using distd. water. In the latter case, the expected products, i.e. portlandite, ettringite and calcite, were obsd. The X-ray diffraction patterns of the cement pastes cured in the presence of tin(II) chloride showed several addnl. peaks that have been attributed to the formation of calcium hydroxo-stannate, CaSn(OH)6, and Friedel's salt (tetracalcium aluminate dichloride-10-hydrate), Ca3Al2O6·CaCl2·10H2O. The amt. of portlandite formed was reduced in the presence of tin(II) chloride. Calcium hydroxo-stannate contains tin in the +IV oxidn. state and equations are presented to account for the oxidn. of Sn(II) to Sn(IV) preceding the formation of CaSn(OH)6 and Friedel's salt. 14、Eco-cement is made from municipal waste incinerator ash, which contains much Al2O3 and Cl-. Consequently Ecocement contains much more interstitial phase and Cl- than OPC. Although 20-40 mass% of Cl- in Eco-cement dissolved into free water within 3 h, Cl- concn. decreased rapidly after that. In the case that the Cl- content in cement was adjusted to 0.1 mass% using NaCl, almost all of the Cl- in free water was bound as Friedel's salt in mortar with Eco-cement, OPC and blast-furnace slag cement. The value of [Cl-/OH-] molar ratio of free water in each mortar was under 0.6 at 28 days, so steel corrosion is likely not to occur. In the case that Cl- content was increased to 1.0 mass%, Eco-cement bound more amts. of Cl- than other cements by producing much amt. of Friedel's salt. The remaining Cl- in free water, which was not bound as Friedel's salt, was sorbed in hydrates such as C-S-H. 15、Hardening properties of two kinds of trial cements based on a sulfate resisting portland cement, one contg. the C11A7·CaCl2 clinker and the other the C11A7·CaF2 one, were investigated by comparison of their hydration properties and the formation behavior of hydrates. The C11A7·CaCl2-contg. cement had less heat of hydration than that contained the C11A7·CaF2 at an early stage of hydration and was easy to mix without rapid setting. Strength development of both hardened cements was strongly related with the rapid formation of ettringite at an early time. Addn. of citric acid to these cements depressed the rate of hydration and the formation of ettringite. The compressive strength of the C11A7·CaCl2-contg. cement mortar was slightly lower than that contg. the C11A7·CaF2 at an early short time, but raised to the same level after 24 h. In the hydration of the C11A7·CaCl2 contg. cement, Friedel's salt formed as a hydrate contg. Cl- ion; however, no hydrates contg. F- ion appeared in the C11A7·CaF2-contg. cement. 16、The structural phase transition occurring in Friedel's salt, the chlorinated compd. 3CaO稟l2O3稢aCl2?0H2O (AFm phase), was studied by synchrotron and std. X-ray powder diffraction. The compd. transforms at 35癈 from a rhombohedral (rh) high-temp. (HT) phase [R-3c; a=5.744(2) ? c=46.890(3) 臸 to a monoclinic (m) low-temp. (LT) phase [C2/c; a=9.960(4) ? b=5.7320(2) 臕, c=16.268(7) ? b=104.471(2)癩. The LT and HT phases were refined with the Rietveld method from synchrotron data recorded at 20 and 40癈. Variations of the lattice parameters as a function of temp. are reported at 8-48癈. The rh甿 transition is characterized by a unit cell vol. expansion of 1% and a movement of the interlayer species: a shift of 0.45 ?of the Cl- anions along [010]h and a shift of 0.25 ?of the water mols. along [210]h of the hexagonal cell. The m phase distortion is due to an ordering of the hydrogen bonds between chloride anions and H-atoms of the water mols. 17、Cement manufd. from incinerator ash has been developed in Japan. This cement contains 15-20% of C3A and 0.02-0.1% of chlorine. Since the chlorine content of this cement is higher than that of normal portland cement in Japan, there is a concern whether steel bars embedded in concrete using this cement would become rapidly corroded. In this study, the behavior of chlorine in cement hydrates is investigated in terms of the contents of chlorine accommodated by Friedel's salt. The compns. of pore soln. in cement hydrates at early ages and the water-sol. and acid-sol. compns. of cement hydrates are analyzed. As a result, it is found that the concn. of chloride ion in pore soln. of cement hydrates using cement manufd. from municipal wastes is not too high. It means that many chloride ions could be accommodated by Friedel's salt because of high C3A content. 18、Friedel's salt, a mineral anion exchanger belonging to the family of the layered double hydroxides (LDHs), was synthesized and used as a novel electrode modifier for the accumulation of iodide species and their subsequent voltammetric detn. at carbon paste. Beside the preconcn. features of Friedel's salt towards iodide species, its presence at the electrode surface allowed to evidence the oxidn. of mol. iodine into iodate (with transient IO-), contrary to most carbon-based electrodes, as demonstrated by cyclic voltammetry. Preconcn. was achieved at open circuit and iodide was then detected by differential pulse voltammetry in unbuffered chloride medium. The sensing process was further improved by optimization of the carbon paste compn., the detection medium, and the accumulation time. The detection limit was 0.06 mM (3s), with linear calibration ranges extending from 0.1 to 1 mM, 1 to 10 mM, and 10 to 50 mM, giving a dynamic range of over several orders of magnitude. The effect of anionic interferences was evaluated and the sensor was applied to iodide anal. in synthetic ground- and seawaters. 19、The effects of addn. of bypass dust (BD) to ordinary Portland cement (OPC) and blended cement systems on the hydration and mech. properties of the hardened pastes were investigated. BD content increment in OPC and blended cement systems shortened induction period. In each curing time, both OPC and slag cement systems showed their max. value of compressive strength and bound water content at 5 wt% of BD addn. As curing time passes, while the content of Ca(OH)2 in OPC increased, that of blended cement decreased. From XRD results the peak of Friedel's salt (C3A·CaCl2.10H2O) grew gradually, as BD content increased. With increasing BD, Ca(OH)2 content decreased in blended cement compared to the control case. As BD content increased, it was obsd. by SEM that C-S-H(II) was the dominant hydrate and the microstructure of hardened cement pastes were more dense than that of neat paste. 20、Soly. relationships between Friedel's salt and hydroxy AFm suggest an essentially complete solid soln. with only minor discontinuities. Solid-aq. partitions were detd. by equilibration of 11 compns. at 10 mol% intervals at ~20 °C in expts. of 6-17 mo duration. Aq. chloride concns. 2 mM are required to incorporate significant Cl in hydroxy AFm; the process is complete, giving essentially pure Friedel's salt, at a chloride content of ~14 mM. The self-generated pH of the solid solns. are high: pH >12 for all compns. The implications for diffusion of chloride ions through cement paste are discussed. 21、Hydration of alinite cement is studied by calorimeter, TGA, XRD, and SEM/EDAX. Ion content in the hydration soln. is detd. by ICP and wet chem. anal. The action of Cl- in alinite cement hydration and its effect on the formation of hydration products are revealed. The hydration reactivity of alinite cement is quite high because of rather rapid hydration of minerals contg. Cl-. Forming C3A·CaCl2·10H2O will reduce sol. Cl- and compose an intergrowth structure with CSH gel. Therefore, strength of alinite cement is enhanced. 22、It is of significant scientific and engineering benefit from the corrosion view point, to know the state of Friedel's salt in concrete structures subjected to the simultaneous attack of chlorides and atm. carbonation. An attempt is made in the present exptl. investigation to elucidate the role of atm. carbonation on the stability of the Friedel's salt in chloride contaminated structures. For this purpose, four different types of concrete slabs, were subjected to chloride penetration over a total period of about three years and then exposed to atm. carbonation for almost the same period. The stability of Friedel's salt, based on XRD and DTA results is shown to be pH dependent. The soly. of Friedel's salt increases with the degree of carbonation of the concrete. It is also concluded that the stability of ettringite is also pH dependent. 23、In this study hydration reactions of municipal solid waste (MSW) fly ash with an exptl. C12A7/C3A-cement are investigated. The fly ash has high contents of sol. calcium sulfates, alkali chlorides and heavy metals. During the first hours the calcium aluminates react with the calcium sulfate to form ettringite. On condition that the amt. of added cement is sufficient, after complete consumption of calcium sulfates further hydration leads to addnl. crystn. of Friedel's salt. The same course of hydration is found for synthetic model mixts. of calcium aluminate + gypsum + alkali chlorides. TEM/EDA-anal. indicates that ettringite is able to incorporate the heavy metals Pb and Zn by substitution, but no contents of Cl- are detected. Treatment by reactive calcium aluminates could be a suitable method for the immobilization process of a wide range of toxic wastes. 24、Friedel's Salt is a poorly understood phase in the CaO-Al2O3-CaCl2-H2O system, which is crit. in the function and stability of salt-satd. portland cement-based grouts. Such grouts are required to seal exploratory excavations in a radioactive waste repository sited in bedded salt. The phase equil. of this system were investigated, and four quaternary invariant points were detd. to allow construction of a phase diagram. The diagram is constructed using a plotting technique applicable to double-decompn. systems or systems with a reciprocal salt pair. Statistical anal. of soln. data was performed to assess the precision and accuracy of the invariant points. 25、A concd. CaCl2 aq. soln. (30%) causes a severe deterioration of cement paste. Such a process occurs in cement pastes produced with high C3A cement as well as with low C3A cement. On the other hand, since the x-ray diffraction anal. shows the formation of both monochloroaluminate hydrate and calcium oxychloride hydrate, it is still possible that both these products are responsible for the deterioration process caused by CaCl2. 26、For a study of the formation and hydration of 11CaO.7Al2O3.CaCl2 (I), I was prepd. by burning a stoichiometric mixt. of CaCO3, Al(OH)3, and CaCl2.2H2O. The burned products were examd. by x-ray powder diffraction with a Geiger counter diffractometer, some of the samples were analyzed chem. for chloride ions, and the setting time and compressive strength of samples of ordinary portland cement (OPC) with added I were detd. I formed at 900-1500°. At >1500°, I liberated chloride ions and was converted to 12CaO.7Al2O3 (II). Chloride ions were occluded in crystals of II, and the lattice const. (a0) of the solid soln., i.e., the system II-I, depended on the amt. of chloride ions. When I was hydrated, chloride ions formed a ppt. of 3CaO.Al2O3.CaCl2.10H2O (Friedel's salt). The setting of OPC was accelerated by adding I with and without anhydrite. The addn. of I and anhydrite increased the early strength of the OPC. 27、The durability of high-Al2O3 cement (HAC) in strong chloride solns., occurring in salt mines, was studied. These solns. contained large amts. of NaCl, MgCl2, and CaCl2. The HAC paste underwent rapid shrinkage in the 1st mo, and then stabilization of the vol. change occurred. However, total shrinkage was small and did not exceed 11 mm/m. Simultaneously, the formation of a very dense layer on the surface of the samples was obsd. Also, very distinct differences in the paste compn. of the different layers appeared. In the dense layer, the recrystn. of Al(OH)3 gel occurred, and a large amt. of Friedel salt was formed. Some basic Mg chloride was also formed. A much higher CAH10 content appeared in the external layer, while in the internal layer the concn. of cubic C3AH6 was substantially greater. This reaction layer was of very limited thickness and, because of its very low porosity, evidently hindered the migration of the ions from the liq. phase to the interior of the paste. This external layer also showed much higher strength. In up to 3 yr, the HAC paste did not show any significant change of properties. 28、The system C3A.CaCl2.nH2O-C3A.Ca(OH)2.nH2O-H2O was studied at 25° and 35 and 100% relative humidity. Between the components Friedel's salt and Ca aluminate hydrate, a limited solid soln. exists. The compn. of the solid solns. is represented by [Ca4Al2(OH)12]2+[Cl(2-2x)OH(2x).H2O(4+2x)]2- with x = 0-0.66. On grinding of the ppts. a polymorphic transformation occurs. Formation conditions, compn., and crystallog. properties of the cryst. phases are discussed. 29、The penetration of chloride ions into hardened cement pastes (hcp) was measured by chem. anal., x-ray diffraction, and thermal anal. The penetration of chloride depends on the permeability; thus, the greater the water/cement ratio the greater the penetration. The concn. of chloride in the hcp is dependent on the concn. of the surrounding soln. The chloride ions react with the anhyd. C3A in the unhydrated cement left in the hcp but not with the complex hydrated Ca aluminate salts including ettringite. C3A.CaCl2.10H2O (I) is formed, but not all the chloride which penetrates reacts to form this mineral. The quantity of I formed is independent of the chloride concn. in the hcp. From a study of the poresize distribution of the hcp by Hg intrusion porosimetry it is deduced that the penetrating chloride reduces the sizes of the small pores thus reducing the permeability. 30、The compn. of hydrated new formations from the hydration of CaO.Al2O3 in 0.5-6 N CaCl2 solns. at 5-50° was studied by chem., x-ray, and thermal analyses. The compn. of hydrated products depended on CaCl2 concn. and temp. of the suspensions. The main hydration products of CaO.Al2O3 in 0.5-3 N CaCl2 at 5° were hydrated CaO.Al2O3 and 2CaO.Al2O3 which are metastable at 20 and 50°. At 20-50°, 3CaO.Al2O3.CaCl2.10H2O or 3CaO.Al2O3.3CaCl2.31-H2O was formed, depending on the temp. and soln. concn., and the main product at 50° was only3CaO.Al2O3.CaCl2.10H2O. 31、The mechanism of hardening of portland cement in the presence of NaCl as an antifreezing additive was studied. The rate of strength increase is lowered in aq. suspensions of 3CaO.Al2O3 in the presence of NaCl and the resulting final strength is reduced. This is due to the decrease of hydration rate and to the change in the phase compn. of the crystg. new structures. Endothermic peaks at 190?and 350?in thermograms indicate the formation of 3CaO.Al2O3.CaCl2.10H2O. This observation was checked by x-ray diffraction and by chem. detn. of bound Cl-. The phase compn. is detd. by the concn. of NaCl soln. and by the ratio NaCl:3CaO.Al2O3. Simultaneously, the isomorphous 2CaO.Al2O3.aq. is formed as evidenced by another endothermic peak at 285-300? The max. mol. ratio CaCl2:-3CaO.Al2O3 is 0.5. The reaction Ca(OH)2 + NaCl ?CaCl2 + 2NaOH probably takes p lace. The hardening is accompanied by the formation of internal stresses. 32、The chem. interaction was studied in suspensions of 3CaO.Al2O3 (I) dissolved in CaCl2 solns. satd. with Ca(OH)2. The only product of interaction is the monochloride form of hydrated Ca chloroaluminate. This is confirmed by thermographic data. X-ray and thermographic anal. showed that in 6N CaCl2 the high-chloride form is observed. On the thermograms there is an endothermal peak at 160° corresponding to the high-chloride form. Satn. of the liq. phase in I suspensions dissolved in CaCl2 and satd. with Ca(OH)2 does not impede the formation of hydrated Ca chloroaluminates. The formation is slower in the presence of Ca(OH)2 than in pure CaCl2 solns. The chloroaluminates 3CaO.Al2O3.CaCl2.10H2O and 3CaO.Al2O3.3CaCl2.nH2O when crystg. out from the soln. give a crystn. hardening structure. With low and medium addns. of CaCl2 (0.5-1.0N) the structure formation shows an induction period. At high concns. the structure is destroyed under the action of internal tensions. |
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4楼2013-11-27 14:44:58
真强必胜
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5楼2013-12-03 20:07:17
真强必胜: 警告！！！！！！！！！！！！ 2013-12-11 21:11:23
真强必胜: 屏蔽内容, 广告止步！ 2013-12-22 20:06:15
真强必胜: 屏蔽内容, 广告止步！ 2013-12-22 20:06:15
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6楼2013-12-11 11:52:44
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