Jun Chang

Effects of Carbonation on Steel Slag Products

The effects of carbonation on structure and properties of steel slag specimens are evaluated by some different testing technologys in this paper. The experimental results of strength and soundness show that the compressive strength of samples is improved 6-8 times due to carbonation, and carbonated specimens have qualified autoclave soundness. Also the carbonation reactions of steel slag and the reason that why strength and soundness improved are analyzed by chemical titration, XRD, TG, SEM and MIP etc. Experimental results indicate that in steel slag specimens, f-CaO, f-MgO, partial C2S and C3S minerals could be carbonated, and 105～110 gram CO2 gas could be sequestrated after carbonating per kilogram of steel slag specimens.

Effect of Sr/Ba Ratio on Dielectric Properties of BSTN Ceramics

The phase composition of (1-x)BaO·xSrO·0.7TiO2·0.3Nb2O5 (BSTN) composite ceramics was analyzed by XRD, and the effect of Sr/Ba ratio on the dielectric properties of BSTN was investigated by impedance analyzer. The results showed that any sample with different x value contained two phases-the perovskite phase and the tungsten bronze phase. The dielectric constants of BSTN basically decreased while the tanδ increased with the increase in x value. Both dielectric constant and tanδ decreased with the applied frequency increased for the same x value. There were two Curie points for BSTN composite ceramics. The first one belonging to the perovskite phase decreased with the increase in x value, but the second one belonging to the tungsten bronze phase kept almost constant at about 300°C.

Study on Effect of Carbonation Curing for Cement Minerals and Clinker

As an advanced technology, carbonation reaction could dispose of industrial solid residues and sequestrate CO2 gas, save resources and protect environment. In this study, Major minerals of cement were high-temperature burned using pure chemical reagents ( the burning temperature of C3S, C2S, C3A, C4AF were 1550°C,1400°C,1330°C, 1350°C). Forming and unforming main cement minerals and clinker were carbonated under the condition of CO2 partial pressure P=0.2MPa, T =25°C, CO2 gas concentration c>99.9% and water/soild w/s=0.12kg/kg. The change of minerals and the effect of carbonation were tested. The experimental results showed that carbonation reaction could been occured in four cement minerals (C3S, C2S, C3A and C4AF), and CaCO3 crystals appeared in these minerals. The sequence of carbonation degree of minerals were C3S﹥C2S﹥C4AF﹥C3A. 0.168g and 0.125g CO2 gas could been sequestrated by 1 gramme of C3S and C2S in carbonated curing respectively, and 0.1301g and 0.1464 g CO2 gas could been sequestrated by 1 gramme of formed and powdery clinker. After carbonated curing, clinker samples had high early strength and good soundness, 2h strength was 24.65 MPa and 3d strength was 41.65 MPa.

Research on the Performance of Ba-Bearing Aluminoferrite Cement

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 C2.75B1.25A3 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 CxAHy 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.

Spectrophotometric Determination of the Ca Ion Content in Steel Slag by Using Chlorophosphonazo as the Spectral Chromogenic Reagent

Steel slag was carbonated and the Ca2+ in steel slag was also dissolving under different carbonation time and dissolution condition. As the spectral chromogenic reagent, chlorophosphonazo was used to analyze the leaching law of Ca2+ in steel slag. The results showed that, Ca2+ concentration in uncarbonated steel slag could rise from 240.79 μg/ml to 802.83 μg/ml in 120 min and Ca2+ concentration varied slowly after 120 min; The f-CaO in uncarbonated steel slag was 2.67%, but reduced from 2.67% to 0.88% after carbonating 3 min and reduced from 0.88% to 0.58% after carbonating 180 min; Ca2+ leaching concentration reduced from 102.31 μg/ml to 44.97 μg/ml after carbonating 180 time; Under the same leaching time(t=90min), the smaller the particle size, the more the leaching concentration of Ca2+ in steel slag.

Pore Structural Changes and Carbonated Depth of Carbonated Steel Slag

Steel slag and carbon dioxide were used as raw materials to prepare building material by carbonation. Effects of forming pressure on carbonation of steel slag and carbonated depth were studied by pore structural changes before and after carbonation and carbonated region. The results showed that these were visible pore structural changes between non-carbonated and carbonated steel slag, and after carbonation, the porosity of steel slag samples were decreased, the number of fine pore was increased and large pore was opposite. Carbon dioxide gas which was sequestrated by Ca(OH)2 and C3S were combined in CaCO3 crystal, and this process was form surface to interior. Clustered granular crystals were generated in the surface and 12 mm depth of samples, while none in the 20 mm depth of samples, no obvious granular crystal growth. The granular crystals which produced by carbonation filled the pores of the sample, in particular the arrangement of dense granular surface of crystal layer, which may impede the spread of CO2 gas to the depths, and carbonation reaction focused on the surface to 12 mm depth region.

Fabrication and Properties of 1-3-2 Piezoelectric Composites

In this paper, the 1-3-2 piezoelectric composites were fabricated by the cut-filling technique using P(MN)ZT piezoelectric ceramic as functional materials and polymer as matrix. The effects of ceramic volume fraction on the electrical properties of the composites were studied. The results indicate that as the ceramic volume fraction increases, the piezoelectric stain factor d33 increases evidently, while the piezoelectric voltage factor g33 decreases. Besides, the planar electromechanical coupling factor Kp and mechanical quality factor Qm of the composite are also less than those of the pure ceramic, while the thickness electromechanical coupling factor Kt is larger than that of the ceramic.

Repairing Bridges in Coastal Area with Ba Bearing Sulphoaluminate Cement

In coastal areas, corrosion has been found in bridge piers made of Portland cement concrete. In an trail to protect the piers from further damages, Ba bearing sulphoaluminate cement concrete was tested as the repairing layers. It is showed that the Ba bearing sulphoaluminate cement concrete has a lower porosity and a more compact structure than Portland cement concrete under the same conditions, and consequently, better performances, such as high strength and corrosive resistance both in lab and real corrosive environments. Stimulating experiments indicate that Ba bearing sulphoaluminate cement is more suitable for repairing bridges in coastal area.