Advanced Materials Research Vols. 306-307

Abstract: The effects of MoO₃ additives on the clinkers mineral formation of portland cement were investigated by X-ray diffraction,scanning electron microscopy. One reference mixture and others modified mixtures, prepared by mixing the blank sample with chemical grade MoO₃ were studied. Based on experimental result, MoO₃ shows the less positive effect, MoO₃ added less than 1wt% was benefit for f-CaO absorbtion, but when more than 1wt% MoO₃ was added, with the temperature increasing, increasing the free CaO (f-CaO) content compared with the pure sample,which cound not promote the formation of 3CaO·SiO₄. MoO₃ can stabilizes crystalline structure of β-2CaO·SiO₄. The analysis results for the microstructure indicate that grain size of C₃S in the samples with MoO₃ is larger than that of only -portland clinker.

Abstract: Dicalcium silicate, whose chemical formula is Ca₂SiO₄ = 2CaO·SiO₂, is a typical cementitious mineral phase, especially in Portland cement clinker. In the past, to study this mineral, it was common to use some conventional heating methods, e.g. flame heating, radiation heating etc. Whereas, in our study, the microwave (or MW in brief) heating method is used to synthesize this mineral, because MW heating method has several advantages in fabricating materials. In order to seek the characteristics of MW heating method in synthesizing this mineral, a conventional synthesizing method (i. e. electric radiation heating) is also used in our parallel experiments, so as to compare the results between experimental samples with both methods. All related samples are measured with XRD (X-ray diffraction) and SEM (scanning electron microscopy), then their results are discussed.

Abstract: The mineral structure and performance of belite-barium calcium sulphoaluminate cement clinkers were investigated by petrographic analysis, X-ray diffraction and scanning electron microscopy. The experimental results showed that the minerals of calcium barium sulphoaluminate (C_2.75B_1.25A₃) and C₂S could coexist in the belite-barium calcium sulphoaluminate cement clinker, and the optimal sintering temperature was 1380°C, at which, more C_2.75B_1.25A₃was formed, well developed and also evenly distributed in the optimal sintering condition. If the sintering temperature exceeded 1380°C, the decomposition of C_2.75B_1.25A₃ would speed up and the C₃S became inactivate for its excessive development. In the optimal sintering condition, the compressive strength of the prepared cement at 3, 7, 28 d were 32.6, 47.9, 88.5 MPa respectively, which exhibited excellent mechanical properties.

Abstract: Consequent upon increased generation of electricity through thermal route involving combustion of pulverized coal/ignite, concurrent generation of fly ash/pond ash in bulk quantities is a matter of serious concern not only because of issues associated with its disposal and utilization, but also because of its threat to public health and ecology. Though a lot of research has been carried out for the effective utilization of flyash like its use in construction industry etc, little literature is available on pond ash utilization particularly its use as a constituent material for concrete in construction industry. Hence pond ash - a waste material, if supplements shortage of fine aggregate (river sand) in mortar and concrete, reduces the demand for disposal of thermal power plant waste, reduces its environmental impact with proper utilization of huge quantity of waste in construction industry. Researches are being carried out worldwide which shows the suitability of Pond Ash as FA. This paper summerises various characteristics of Pond Ash as fine aggregate in concrete with its engineering properties such as its shape, gradation, texture, physical, chemical and also morphological aspects when used in concrete

Abstract: This paper discussed the main clinker minerals and their optimal proportion of Ba-bearing aluminoferrite cement. The results show that the optimal sintering temperature is 1365°C. In XRD patterns, the diffraction peak of C_2.75B_1.25A₃ and C₄AF nearly disappear when the harden cement slurry hydrated for 3d at absent of gypsum. At the same time, a large numbers of hydration products like BaSO₄ and C_xAH_y which including CAH₁₀, C₂AH₈, C₄AH₁₉ and so on, appear in XRD patterns. So the hydration rate of Ba-bearing aluminoferrite cement is fast and the degree of hydration is high. These hydration products come into being a stable structural frame so that 3d compressive strength of the clinker can reach to 73.3MPa.

Abstract: In this paper, a series of enzymatic hydrolysis lignin modified petroleum asphalts were prepared. The physical properties such as softening point, ductility at low temperature and penetration of the modified asphalt were investigated. The penetration index of asphalt modified with EHL was higher than that of unmodified asphalt, equivalent softening point increased and equivalent brittle point decreased with the increase of EHL amount, which showed that the addition of EHL was favorable to reduce the temperature susceptivity of asphalt. When the EHL was 4%, the ductility was 39.0 cm. Meanwhile, low temperature performance of asphalt could be further improved by adding EHL and a small amount of SBS.

Abstract: In order to study cubic compressive strength of recycled coarse aggregates-filled concrete systematically, recycled coarse aggregates with the particle size from 50 to150mm are made from waste solid contents, which are artificially broken from abandoned rubble and concrete blocks. Based on the mix proportion design method of ordinary concrete and test code for hydraulic concrete, 3 groups of recycled coarse aggregates-filled concrete cubic specimens were prepared and the compressive strength of the specimens were tested. The results showed that basic failure pattern of recycled coarse aggregates-filled concrete are longitudinal splitting failure, and that cubic compressive strength is higher than that of self-compacting concrete.

Abstract: On condition of formulating malic acid (Malic) with super plasticizers (SPs), the hydration heat of α-calcium sulfate hemihydrate (α-HH) was studied. The results show that: Malic and SPs mainly adsorb on gypsum surface to exert inhibition; influence of compositing SPs on hydration process mainly depends on the adsorption of SPs and the effect of SPs on Malic adsorption; formulation of sulfonate melamine formaldehyde plasticizer (SMF) limits the adsorption of Malic.

Abstract: Effect of the different contents of limestone power (LSP) in manufactured-sand (MS) is investigated in respect of the workability, setting time and compressive strength. The results show that the contents in a certain range can significantly increase the consistency, Specific density of the fresh mortar, and improve comprehensive strength of the hardened mortar due to LSP deduced the porosity and improved the pore structure.

Abstract: In order to enhance the ability of sulfate resistance of the coastal engineering, the effects of hydroxyapatite, shell and calcium carbonate on the mechanical performance and sulfate attack resistance were studied. The composition and structure of hardened cement paste were analyzed by means of X-ray diffraction and scanning electron microscopy. The experimental results showed that with the increase of mixed material contents, the compressive strength decreased, while the content of hydroxyapatite was 5%, the strength reached highest. The ability of sulfate resistance was improved as appropriate amounts of hydroxyapatite, shell and calcium carbonate were added into the cement. When the content of hydroxyapatite was 5%, the corrosion resistance coefficient was1.24, reaching the best resistance to sulfate attack.