Effect of Barium Oxide on the Formation and Coexistence of Tricalcium Silicate and Calcium Sulphoaluminate

Formation and coexistence of tricalciurn silicate （C3S） and calcium sulphoaluminate （ C4 A3S^- ） minerals in Portland cement clinker containing calcium sulphoaluminate were investigated. Thef-CaO content, mineral composite and formation of mineral in the clinker were analyzed respectively by chemical analysis, differential scanning calorimetry（DSC） and X-ray diffraction. The results show that, adding a suitable amount of BaO can improve the burnability of raw meal and promote the f-CaO absorption. Tricalcium silicate and calcium sulphoaluminate minerals can form and coexist in clinkers at 1 234-1 317 ℃ by the addition of BaO to the raw meal. A suitable amount of BaO expanded the coexistence temperature of two minerals by 58 ℃.

Effect of Phosphorus and Fluorine on Hydration Process of Tricalcium Silicate and Tricalcium Aluminate

By means of hydration heat, XRD and SEM, effect of phosphorus and fluorine （P205 and F-） in phosphorous slag on hydration process of tricalcium silicate （C3S） and tricalcium aluminate （C3A） was explored. The results indicated that the early hydration exothermic rate of C3S and C3A was obviously lowered by P205 and F- in phosphorous slag, the second peak occurring time of C3A was delayed by 0.9 h, the exothermal output of C3S was reduced by 25.04% and the time of accelerating stage was postponed by 0.86 h. The early hydration degree of C3S and C3A was also decreased. Due to the influence of P205 and F, more pores and thinner crystals can be observed in the microstructure of hardened paste and the chance of cracks was reduced.

Optimization of the Content of Tricalcium Silicate of High Cementing Clinker

Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction（XRD）.＂K Value＂method of QXRD was selected as a quantitative analysis way to measure the content of C 3 S,and the strength of cement paste was determined.The results show that at a water cement ratio of 0.29,the strength of cement paste with 73%C 3 S can be up to 97.5 MPa at 28 days age.The strength at 28 d of cement with 73%C 3 S is 16%higher than that with 78%C 3 S at water requirement for normal consistency.The relationship between the strength of high cementing Portland cement and the content of C 3 S in the clinker is nonlinear.According to the strength of cement paste,the optimal content of C 3 S in cement clinker is around 73%in this paper.

Effect of Minor Elements on Silicate Cement Clinker

The effect of rare-earth and HX addition agent on the burn-ability of silicate cement dinker was investigated by orthogonal experiment. The result shows, compared with blank sample, f CaO of the .samples added with rare-earth and HX agent drops by 84.95% , its 3 d and 28d compressive strength enhances by 24.40% and 16.90% , respectively. It was discovered by means of X-ray diffrnction and high temperature microscope analysis that sintering temperature of the sample added with rare-earth and HX addition agent is about 1320℃. At the same time, the tmrning temperature of triealeium silicate desends and its crystal growth forming- rate increases. Tricalcium silicate content in burning clinker is higher and its crystal is larger.

Effects of Molecular Structure of Polycarboxylate-type Superplasticizer on the Hydration Properties of C_3S

Effects of polycarboxylate-type superplasticizer（PC） molecular structure on the hydration heat of tricalcium silicate（C3S） paste and polymerization degree of hydration products（C-S-H gel） were researched by using TAM AIR isothermal microcalorimetry（TA） and 29Si nuclear magnetic resonance（NMR）.Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.

Composition Design for High C_3S Cement Clinker and Its Mineral Formation

A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO （in mass）. Fired at 1 200℃,1 350℃,1 400℃ and 1 450℃ for 30 min, the resultant mineral phases component and mineral morphology were analyzed. The performances of the cement which was made of clinker burned at 1 450℃ and fly ash were determined. By means of QXRD, XRD and optical microscopy, it is shown that the clinker burnt at 1 450℃ has the larger size crystals and distinct crystal interface, in which the C3S content is 73.37% and the mineral phases is dominantly C3S, following by minor C2S, C3A and tetracalcium aluminoferrite. The results reveal that a new type of high C3S content clinker can completely be made by traditional temperature-time schedule. The performances of the cement produced from this clinker with addtion of 50% fly ash and 5% gupsum were in agreement with the 32.5 strength grade of Portland fly-ash cement. The results also show that the clinker has a significant effect of saving energy and utilizing waste slag.

Synthesis of C_3S by Sol-Gel Technique and Its Features

Sol-gel method is a technique to synthesize inorganic materials based on wet-chemical reaction theory. The results have shown that reactants tetraethyl orthosilicate （TEOS） and Ca（NO3）2·4H2O can form sol and gel in solution at 50-60 ℃, and the cosolvents are propyl alcohol （NPA） and H2O, the catalyst is HNO3. This sol-gel is burned for 12 hat 1 350-1 450 ℃ so that the organic matter, free water （moisture） in sol-gel system are removed and a solid reaction has taken place to form the resulting product. The product has been confirmed to be C3S by XRD, SEM and 29Si MAS NMR, as well as free lime content of the product which is less than 0.2% was determined by propanetriol-ethanol-method. The analysis determined by EDXA has indicated that the n（Ca）/n（Si） ratio in corresponding to micro-region is close to theoretical value of 3∶1. This resulting product is C3S with Si sites of Q0 polymerization, and has higher purity and hydraulic activities at earlier age of hydration.

Effect of CuO on the Burnability and Mineral Formation of High C_3S Cement Clinker

The effect of CuO on the clinkering process and mineral structure, components and morphology of high C3S cement clinker was studied. One reference mixture was prepared according to the potential mineral phase components C3S=75%, C3A=7%, C4AF=18% and then was mixed, respectively, with 0.5%, 1%, 1.5%, 2%, 2.5% and 4% CuO. All samples were heated at a rate of 10°C/min to the design temperatures and then maintained for 40 min. Analyses by the glycerol-ethanol method, XRD and SEM-EDS show that the minimum of free lime （f-CaO） content was related to temperature and CuO amount. The higher the temperature, the lower the amount of CuO corresponding to the f-CaO minimum content. CuO promotes the formation and growth of C3S and C4AF and a new compound is found. In addition, these phenomena are discussed theoretically. In conclusion, CuO alters the burnability and the formation and structure of C3S in a high C3S cement system.

C-S-H Cluster Microstructure and Bonding Force Investigation base on AFM Technology

AFM （atomic force microscopy） technology was applied on C-S-H （calcium silicate hydrate phase） microstructure investigation. The topographies of hydrated C3S （Tricalcium silicate） samples were firstly acquired with AFM. Accordingly, C-S-H can be identified according its pattern. Then the hydrated pssortland cement samples at different curing time were scanned with AFM. The topographies and force displacement curve were acquired and its characters at different days were summarized and analyzed. These results are very meaningful for C-S-H microstructure further investigation and cement-base material macro scale properties improvement.

Strength Activity Index of Air Quenched Basic Oxygen Furnace Steel Slag

Air quenched basic oxygen furnace steel slag （BOF-SS） is processed at very high cooling rate, which is expected to have different cementitious properties from conventional slowly cooled BOF-SS. For this purpose, the strength activity indexes of air quenched and slowly cooled BOF-SS are investigated. The results reveal that, under the specific surface area （S） of 490 m^2/kg, the compressive strength activity index reaches 1.24 after 28 days with replacement of 15% air quenched BOF-SS and reaches 1.05 after 28 days with replacement of 20% air quenched BOF-SS and 30%granulated blast furnace slag （GBFS）. The cementitious activity of air quenched BOF-SS is obviously higher than that of slowly cooled BOF-SS, mainly because it contains more C3 S and glassy phases.