Advanced Materials Research Vols. 306-307

Abstract: Sulfoaluminate cement, non-ionic polyacrylamide and sulfamate high-effective water reducing agent were used as main raw materials to fabricate concrete. The adhesive performance of high performance sulfoaluminate cement underwater non-dispersed concrete and its influence on water quality in surrounding water areas were studied. The compressive strength ratio of concrete cast in water and in air was also determined. The results show that mortar and concrete using non-ionic polyacrylamide as adhesion agent has many advantages such as superior underwater anti-washout properties, little pollution to water quality in the surrounding water areas and obvious early strength. Furthermore, the compressive strength ratio of concrete cast in water and in air is also up to the required standard.

Abstract: The influence of P₂O₅ on the properties of alite-calcium strontium sulphoaluminate cement was researched by means of X-ray diffraction, scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) and petrographic analysis. The results show that the optimal content of P₂O₅ is 0.3% and the compressive strength of the cement at 1, 3, 28d are 27.0, 59.1, 110.9MPa when the calcining temperature is 1350°C. P₂O₅ mainly exists in the belite and a suitable amount of P₂O₅ can promote the formation of C_1.5Sr_2.5A₃ and alite. When the content of P₂O₅ is higher than 0.3%, the formation of C_1.5Sr_2.5A₃ and alite can be hindered. P₂O₅ can enhance the hydration heat evolution rate in the acceleration period and the hydrate heat of cement containing P₂O₅ increases slightly.

Abstract: Through testing the amount of the free lime and the Loss ignition, the clinker formation rate, the reaction-rate constant (K) and the activation energy (Ea) were calculated according to the Gentling equation and Arrhenius equation. The effects of CaF₂ on the formation kinetics of Portland cement clinker were investigated by analyzing the K and Ea. X-ray diffraction (XRD) and scanning electron Microscope (SEM) were used to characterize the phase composition and the morphology of the resulting samples. The results show that the silicate minerals formation is promoted when a proper amount of CaF₂ is doped into the raw meal. The K increased from 0.7450 ×10^-5s^-1 to 7.1588 ×10^-5s^-1 and the Ea decreased from 386 kJ/mol to 122 kJ/mol when the amount of CaF₂ increased from 0.0% to 2.0% in mass. However, the results were reversed at the amount of CaF₂ exceeding 2%.

Abstract: The effects of the sintering temperature, sintering time and contents of calcium strontium suphoaluminate (C_1.5Sr_2.5A₃) on the sintering technology of the alite-rich cement clinker modified by C_1.5Sr_2.5A₃ were researched by the orthogonal test method. X-ray diffraction, scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) and lithofacies analysis were used to investigate the compositions and structure of cement. The experimental results show that the optimal sintering temperature and sintering time of alite-rich cement clinker modified by C_1.5Sr_2.5A₃ are 1350 °C and 60 min, and the appropriate content of C_1.5Sr_2.5A₃ in the clinker is 2%. The introduction of C_1.5Sr_2.5A₃ in clinker can promote the formation of alite mineral at low temperature and decrease the sintering temperature of clinker by 100°C approximately. This new-type cement shows excellent mechanics properties. The compressive strength at 3d is up to 64.3MPa, which is increased by 26.7% comparing to that of alite-rich cement and the compressive strength at 28d is almost the same as that of alite-rich cement. For alite-rich cement clinker modified by C_1.5Sr_2.5A₃ calcinated at low temperature, alite still can be mass-formed, but the size decreases.

Abstract: The paper studied the adaptability between alite-sulphoaluminate cement clinkers with different amount of C₃S and the fly ash admixture. The results showed that: with a fixed content of C₃S, the setting time of the cement delayed, and the compressive strength of the cement decreased with increasing amount of fly ash admixture. With a fixed content of the fly ash admixture, the setting time of the cement delayed, the compressive strength of the cement increased with the increase amount of C₃S, and the lowed percentage of the strength decrease at each ages; With addition of fly ash admixture, the early compressive strength of the cement decreased more, while the later compressive strength decreased less. Clinker with higher C₃S content showed better adaptability with high addition amount of fly ash admixture.

Abstract: The influences of sand-cement ratio on bulk density, fluidity, compressive strength, flexural strength of mortar of river sand, limestone manufactured sand (MA), quartzite MA, granite MA were studied compresively in the paper. The results show that bulk density of mortar reaches to maximum if sand-cement ratio of mortar of river sand is 2.73 and the ratios of mortar of manufactured fine sands are all 3.0. The fluidity of mortars of river sand and limestone MA are better than those of quartzite MA and granite MA. Sand-cement ratios of mortars with maximum strength are equal to that with maximum bulk density. The sequence of compressive strength is limestone MA, quartzite MA, river sand, granite MA from high to low, and that of flexural strength is limestone MA, quartzite MA, granite MA, river sand.

Abstract: The compressive strength of the cementitious materials doubly with alkaline slag and fly ash are investigated in this paper. The optimum mixing way and ratio of weight were found. The hydration properties of cement binders with alkaline slag and fly ash are studied using XRD and SEM. The result shows that alkaline slag can stimulate the activity of fly ash, increase the hydration velocity of clinker mineral and improve the second hydration of fly ash.

Abstract: 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.

Abstract: A cement-based foamed lightweight thermal insulation material was prepared with cement, industrial waste (fly ash, steel slag) as the main raw materials, by using self-developed composite activator and foaming agent. The influence of foam content on dry density, compressive strength and thermal conductivity coefficient of material was studied, the activation mechanism of composite activator to fly ash and steel slag was discussed. Results showed that, the dry density and compressive strength of material decreased, and thermal conductivity coefficient decreased first and then increased with the increasing foam content.

Abstract: Effect of doped BaO on the formation dynamics of alite of alite-rich cement clinker was investigated. The experimental results indicated that its formation kinetic satisfied with three- dimensional spherical model and accorded with Glinstling diffusion equation. Doped BaO could decrease dramatically the apparent activation energy of alite-rich cement clinker. This was contributed to the combination of C₂S and CaO in liquid phase, and acceleration of formation of alite-rich cement clinker.