Advanced Materials Research Vols. 306-307

Abstract: The influences of slag on the expansion of alite-calcium barium sulphoaluminate cement were studied. The experimental results indicated that the formation of ettringite and Ba-bearing ettringite are the main expansion sources of alite-calcium barium sulphoaluminate cement clinker with only gypsum. In addition to the ettringite and Ba-bearing ettringite, the Mg(OH)₂ crystal formation was another probably the expansion source. The expansion rate of alite-calcium barium sulphoaluminate cement increased with slag content rising. Even if the content of slag in cement arrived at 20%, the soundness of alite-calcium sulphoaluminate cement its expansion was still in the safety range.

Abstract: Some properties of asphalt mastic containing recycled cement mortar powder (CMP) were investigated in this paper. CMP was used as filler in asphalt mastic. The investigated mastic consisted of asphalt and filler at a mass ratio of 1:1. Penetration, softening point and high-temperature viscosity were tested. Dynamic Shear Rheometer (DSR) was used to conduct frequency sweep test of asphalt mastic. The introduction of CMP resulted in reduced penetration, increased softening point, apparent activation energy, complex shear modulus in the low frequency area and high-temperature viscosity. Results indicate that CMP may have some positive effect on high-temperature properties but some negative effect on low-temperature properties of asphalt mastic. It is also believed that the average mixing and compacting temperature of asphalt mixture containing CMP is higher than that containing limestone mineral filler (LMF).

Abstract: Activation of coal gangue from Yixing was done by the method of addition of calcium during calcination. Structural characteristic and cementitious properties of activated samples were analyzed. And then hydration degree of activated coal gangue cement was studied. The results show that: thermally and chemically added-calcium composite activation method can improve the activity of coal gangue. At 1050°C, more effective silicate minerals may be in activated samples, with which cement system may have a higher degree of hydration. infra-red(IR) spectra shows that large number of new mineral peaks can occur in activated sample, and with extending of hydration age mineral peaks gradually decreases until it disappears.

Abstract: The influence of slag and fly ash on the self-healing ability of concrete was researched by strength measurement and SEM analysis. The self-healing ratio was measured by the increase of compressive strength before and after self-healing. The optimal mixing amount of slag and fly ash were determined, and the reasonable sand ratio was obtained. Analyzing results show that the self-healing ability of concrete was the strongest when the mixing content of slag and fly ash were 30% and 40% respectively. The appropriate sand ratio was also obtained, when the sand ratio is 33%, the self-healing ability of concrete is the strongest.

Abstract: Synthesis conditions and performance of alite-strontium calcium sulphoaluminate cement have been studied by introducing strontium calcium sulphoaluminate into Portland cement clinker. The effects of gypsum on compressive strength, hydration degree and structure of hardened alite-strontium calcium sulphoaluminate cement paste were studied in this paper. Composition and structure of the hardened cement paste were analyzed by XRD and SEM. Results show that appropriate content of gypsum could contribute to the hydration of alite-strontium calcium sulphoaluminate cement. When gypsum content is 9%, the compressive strengths for 1d, 3d and 28d curing age are 30.7MPa, 59.5MPa and 105.5MPa, and the corresponding hydration degree are 40.4%, 57.5% and 85.8%, respectively. The hydration products of alite-strontium calcium sulphoaluminate cement are mainly ettringite (AFt), Ca(OH)₂, C-S-H gel. Large amount of AFt formed at early curing age provides a sound basis for early compressive strength, and a lot of C-S-H gel generated at later curing age increases the density of the hardened paste.

Abstract: This article carried out the strength experiments on four hundred and five specimens with twelve mix proportions and three curing ages, systematically investigated the relationships of related strengths, the dimensional effect of compressive strength and splitting tensile strength of plastic concrete. The results showed that there well exist the statistical relationships among the related strengths of plastic concrete, the dimensional effect coefficients of compressive strength and splitting tensile strength with 100mm cubic specimen are 0.9375 and 0.8616 respectively compared with 150mm cubic specimen. Based on the analysis of test results, the conversion formulae of strength-related indicators and linear function relationship between axial compressive strength and curing ages are put forward respectively.

Abstract: The standard diffusion calculating model is one of the models widely used to predict the concrete construction life in chloride environment. According to test results, the surface concentration and the initial concentration of chloride ion on sulphoaluminate cement sample was analyzed by mathematical method. Life prediction model in chloride environment was built. According to the model, the sulphoaluminate cement construction life will be 51.5 years when the thickness of cement protective layer is 40mm.

Abstract: Calcium sulphoaluminate (3CaO·3Al₂O₃·CaSO₄, ) was synthesized with pure chemical reagents. The adsorbed amount of aminosulfonic acid-based superplasticizer (AS) on the surface of mineral and the mineral mixture (mixture of the , Ca(OH)₂ and CaSO₄·2H₂O) were detected by ultraviolet-visible absorption spectrometry. The adsorptive behaviors of AS on the surface of mineral particles in the hydration system were studied. The results showed that: the adsorbed amount of AS on mineral and the mineral mixture increased with higher initial concentration; the adsorption amount and the maximum adsorption amount increased with prolonged hydration time; the adsorption amount and the maximum adsorption amount of AS on the mineral mixture was more than those on the mineral in the hydration system within the same hydration time.

Abstract: After the assessment targets on concrete performance of anti-sulfate erosion were optimum designed rationally to be assessment parameters, the course on performance deterioration of concrete was characterized using designed assessment parameters. The results show that, every performance deterioration degree of concrete can be compared on the same coordination axis by assessment parameters. The assessment parameters were applicable the same determination criterion, and the determination principle is simple and convenient. The comparing the deterioration course and sensitivity degree of concrete performance is much easy. If concrete performance of anti-sulfate erosion was experimented at laboratory, the result assessment ought to use the two non-destructive test assessment parameters.

Abstract: A new method to improve the water-resistance of magnesium oxychloride composites (MOCs), with the addition of nano rice-husk ash (RHA), was studied. The related properties of samples were characterized by scanning electron microscope (SEM) and Brunauer Emmett and Teller (BET). The phase composition of MOCs was determined by X-ray diffraction (XRD). The water-resistance of MOCs was estimated by calculating softening coefficients. The experiments show that the particles size of nano RHA prepared is about 50nm, and the SiO₂ content is 92.30 %; a suitable amount of nano RHA to MOCs obviously increases the water-resistance without reducing the bending strength of MOCs, and increases the softening coefficient from 0.29 to 0.78.