Chen Chen Gong

Preparation and Properties of Sulphoaluminate Cementitious Materials with Low Alkalinity

The influence of anhydrite on mechanical property and alkalinity of sulphoaluminate cement clinker was investigated. The alkalinity was examined by mixing powdered samples with a solvent and measuring the pH of the suspension. The hydration mechanism was analysed by XRD analysis. The results indicated that with the increase of anhydrite addition, both the alkalinity and compressive strength decreased. Yeelimite completely converted into ettringite with the dosage of anhydrite reaching to 50% by weight of the paste. With the dosage of 30%, the 7 d pH could be reduced to 10.43 while the 7 d compressive strength was 48 MPa.

Preparation and Performance Testing of Foamed Concrete

The key influences of foamed concrete and the optimum preparation technology were studied. The performance of foamed concrete was analyzed by the compressive strength testing, SEM. Results show that the flowability of cement paste is good when water-cement ratio is 0.4. The amount of foam added in sulphoaluminate cement is not able to exceed 3.5L/kg. However, the dilution multiple of foaming agent is near concentration and the mixing time depends on the foam quantity. When the water-cement ratio is 0.4, the foam quantity is 3 L/kg and the foaming agent is diluted 30 times. When the mixing time is 60s, the dry density is around 380kg/m3 and the 7d compressive strength reaches to 0.9MPa.

Influence on Activation Property of Coal Gangue by Calcining Temperature

Influence on activation property of coal gangue by calcining temperature was discussed. The experimental results show that C12A7 and C2S with hydraulic-activity are created in coal gangue calcined at 900 - 950°C which has reasonable pore distribution after hydrating.

Influence of CaF2 on the Formation Kinetics of Belite-Calcium Barium Sulphoaluminate Cement Clinker

This paper studies the formation dynamics of belite-calcium barium sulphoaluminate cement clinker with and without CaF2. The results suggest that, under the condition of the experimental preparation process, the formation process of belite-calcium barium sulphoaluminate cement clinker is controlled by diffusion mechanism in the temperature range of 1250-1380¡æ and the formation dynamics fits nicely with D4̍́˽̂ځ˿̃˽˸́˽ځ˹2/3=kt. Apparent activation energy was calculated to be 250 kJ·mol-1and 195 kJ·mol-1 for sample clinker without and with 0.6% CaF2 content. It is concluded that CaF2 contributes a lot to the reduction in energy consumption during the process of sintering belite-calcium barium sulphoaluminate cement clinker.

Mineral Composition and Performance of Phosphoaluminate Clinker with Addition of SO3

The effect of SO3 on the mineral composition and performance of phosphoaluminate clinker was investigated by means of XRD, IR and SEM. Also, the compressive strength of clinker was performed. The experimental results showed that a certain amount of SO3 would promote the formation of calcium phosphoaluminate mineral, which was good for the strength development of phosphoaluminate clinker. Moreover, the addition of SO3 was benefit to the formation of C4A3 in phosphoaluminate clinker. So, the 5% dosage clinker owns a good strength development.

Study on the Formation of C3S Doped with SO3, BaO and MgO

Specimens were prepared by burning mixtures containing CaCO3 and SiO2 in 3:1 stoichiometric ratio along with dopants at different temperatures. Formation of C3S doped with SO3, BaO and MgO was studied. The results show that the temperature of beginning formation for C3S is 1380°C in the system, and there exist both C3S and C2S. SO3, BaO and MgO can effectively stabilize the M1 and M3 type alites through substitution and interstitial imperfection, and make f-CaO content 8.68 wt% at 1450°C. C3S doped with minor elements appears in the shape of six-party plate with the mean size of 17~30μm.

Composition Characteristics of Reconstructed Steel Slag with Electric Furnace Slag

Mineral compositions and granule morphology of reconstructed steel slag with electric furnace slag as an adjusting component were discussed. The vitreous content with hydrofluoric acid erosion and petrographic analysis were carried out. The results showed that the vitreous content of steel slag was lower than that of raw and first decreases and then increases as the calcination temperature increases; C3S becomes hexagonal sheets or square columnar with the size of 40 to 60 microns and C2S becomes spherical with size of 20 to 50 microns. Particle shape is more regular and the size is smaller than that of raw.

Effect of Material Constitution on the Properties of Thermal Insulation Materials

Cement-based foam insulation board is a lightweight thermal insulation and have a characteristic of energy saving. The effects of material constitution on the properties of mechanical properties, dry densityand thermal conductivity for thermal insulation materials. The subject of fast hardening sulphoaluminate cement as cementitious materials, polystyrene particles as a lightweight thermal insulation material, adding a certain amount of water reducer, cellulose ethers, air entraining agent to make thermal insulation materials. The experimental results shows that the appropriate material constitution is following: the cement-bead ratio is 12, the ratio is 0.65, the water-cement ratio is 0.4, the content of water reducer is 0.5%, the content of cellulose ether is 0.4%, the content of the air entraining agent is 0.4% .This mix ratio test of mechanical properties are: flexural strength is 0.72MPa, compressive strength is 1.24MPa, dry density is 375kg/m3, water content is 2.3%, water absorption is 10.8%, softening coefficient is 0.95 and coefficient of thermal conductivity is 0.053 W/ (m K).

Effect of Different Mineral Admixtures on Properties of Sulphoaluminate Cement

Effects of superfine slag powder, fly ash and ultra-fine CaCO3 on compressive strength of sulphoaluminate cement were investigated. Cement hydration products were analyzed by using scanning electron microscopy (SEM). The results show that different fineness and additions of mineral admixture differ in compressive strength. When the amount of superfine slag powder, fly ash and ultra-fine CaCO3 are added by 10%, 10% and 3% (by weight), the compressive strength of the hardened paste of sulphoaluminate cement is highest, respectively. Meanwhile, it is concluded that the additions of superfine slag powder and ultra-fine CaCO3 facilitates hydration at early ages, while fly ash could accelerate hydration at later ages.

Intensifying Test of Recycled Aggregate Made with Crushed Concrete

Compared with natural aggregates (NA), recycled aggregates (RA) have higher porosity and water absorption rates due to the presence of the porous cement mortar. This paper attempts to report several treatment approaches to improve the properties of RA by their impregnation with kinds of chemical solutions. Effects on compressive and tensile splitting strengths of RAC were investigated. The results show that not only the behavior of RA has improved with reduction in water absorption but also a marked improvement in the mechanical properties of RAC.