共查询到20条相似文献，搜索用时 15 毫秒
1.
WANG Li-peng 《保鲜与加工》2012,(2):143-148
Without natural lime stone, clay, shale and sandstone, with the mass fracrion of demolition concrete in raw meal up to 95%~99%, along with ordinary calcining process, the cement clinkers (hereinafter called recycled clinkers for short) were produced. Experiments and analysis were employed to compare these recycled clinkers with the cement clinker which was manufactured by natural lime stone and sandstone. It is shown that the two types of clinkers have completely the same positions of characteristic peaks of XRD; the clinker minerals of recycled clinkers are formed normally; the two clinkers have similar chemical composition, and the rate value design of recycled clinkers are more likely to higher calcium and lower silicon; the content of f-CaO of recycled clinkers meets the requirements of soundness; the 3d strength of cements produced by recycled clinkers reaches the requirements of 42.5 grade Portland cement, and the 28d strength reaches the requirements of 52.5 grade. 相似文献
2.
Two kinds of magnesium slag from different places were added in clinker respectively to manufacture portland cement, and the essential properties of cement, such as water requirement of normal consistency, setting time and strength, were studied. The influence of magnesium slag on the drying shrinkage of portland cement was investigated. Meanwhile, effects of magnesium slag in portland cement were analyzed on the basis of XRD, DSC/TG and SEM microscopic experiments. The results show: magnesium slag plays roles in water-reducing and set-retarding as a composite material of cement; when the contents of magnesium slag range from 10%～30% (weight ratio) and 35%～40% (weight ratio), cement samples reach Composite Portland Cement 42.5R and 32.5R standard, separately; the drying shrinkage of mortar can be restrained as the contents of magnesium slag range from 30%～40%; and the structure of cement pastes is more compacted as magnesium slag reacts with the hydrations of clinker. 相似文献
3.
Municipal solid waste incineration fly ash (MSWI) was successfully used as raw material in sintering and preparing a calcium sulphoaluminate (CSA) cement clinker in laboratory. The effects of different types and different addition percentages of cement additives on compressive strength and hydration properties were investigated. The results showed that lime (LI) powder / slag (SL) powder was compatible in CSA cement system while the activities of fly ash(FA)/ MSWI was low. Adding these four types of cement additives in CSA cement system respectively, there were negative effects on compressive strengths of hardened cement at early age while LI/SL improved the compressive strength at later age. The performance of combined additives was better, especially, the specimens with 10%LI+10%SL, 10%LI+10%MSWI, and 5%LI+15%SL. 相似文献
4.
Qin Lichuan Yang Tao 《保鲜与加工》1991,(1)
The colourcd clinker cement which fired directly from kiln has the advantages of low cost,bright colour and good colour durability.This paper studies the possibility of using calcium flouridc and gypsum combined mineralizer to calcine the col-outed clindcr cement at low temperature.Different methods such as X-ray diffraction ana ysis,scanning electron microscopy,infrared spectra analysis,combined water content chemical asysis,compressive strength test and so on arc used to study the clinder minerals,the colour,the physical and mechanics properties and behaviour of the coloured clinker cement which made both with high quality raw materials and with electric furnace reduced slag additive. 相似文献
5.
PENG Zhi-hui~ 《保鲜与加工》2004,(1):93-96
The chemical composition and form of impurities in titanium gypsum and their effects on properties of cement were introduced when used as set retarder for Portland cement. Experimental results show that the impurities are mainly Fe (OH)_3, FeSO_4 and Al(OH)_3, and they may do little effect to Portland cement. The properties of cement with titanium gypsum are similar to those of Portland cement with natural gypsum, 相似文献
6.
By means of SEM, XRD and calorimeter C 80Ⅱ, the hydration characteristics and hydration kinetics of cement based materials with and without P2O5 incorporated were investigated. It is found that the amount and size of hydration products incorporated with P2O5 were decreased dramatically. When 3.5% P2O5 was added in cement, total amount of hydration heat was decreased by 32.6% and initial and final setting were delayed by 1.10 h and 12.54 h respectively. In terms of mechanism analysis, P2O5 had little impact on cement hydration mechanism, and accelerating stage was controlled by chemical reaction, decreasing stage controlled by both chemical and diffusion reaction while stabilizing stage controlled by diffusion alone. The hydration resistance in both accelerating and decreasing stage was elevated while decreased in stabilizing stage. The activation energy in both accelerating and decreasing stage were reduced and increased in stabilizing stage. P2O5 was favorable to hydration of C3A yet retarded hydration of C3S and C2S. 相似文献
7.
The changes of electrical resistivity with time of cement pastes with water to cement ratio of 0.23, 0.35 and 0.53 were in situ continuously monitored by using electrodeless resistivity apparatus. Isothermal conduction calorimeter was also used to measure the hydration degree. The quantitative relationship between electrical resistivity evolution of paste and development of pore structure was proposed during hydration process. The results show that four stages (dissolution, induction, acceleration and deceleration) are identified according to the characteristics of electrical resistivity and its differential resistivity curves. In addition, a lower water to cement ratio shows a smaller capillary porosity and constriction factor as well as a higher tortuosity factor, resulting in a higher electrical resistivity of bulk paste, and the reverse phenomenon is observed with the electrical resistivity of pore solution. 相似文献
8.
The
method of AC impedance spectroscopy has been applied to study the properties of interface
between cement paste and crushed stone. The effect of interface between cement paste and
crushed stone can be determined by comparison of three parameters in AC impedance
spectroscopy. 相似文献
9.
The amount of limestone powder, which is a by product of manufactured fine aggregate, is larger and larger with the increase of manufactured fine aggregate. Environment will be severely polluted if the powder is improperly used. The effects of limestone powder on workability, compressive strength, and impermeability of concrete were studied when cement is substituted for the mass proportion of 0, 10, 15, 20 percent with it. The results show that the performances of concrete are better improved when the percentage of limestone powder is about 10 percent. The wet packing density of mixture of limestone powder and cement was measured, and it shows that the degree of density was biggest when limestone powder is 10 percent. This shows that the best mixing proportion of limestone powder and cement may be determined through measuring the change of compactness of mixture of limestone powder and cement. 相似文献
10.
The advantages and shortcomings of traditional method and Finite Difference Method (FDM) for the calculation of cantilever slab model with void beneath cement concrete slab corner and analysis on the results were carried out. The traditional method assumes that the cement concrete slab with void below was a cantilever slab with constant sections. The influence of loading eccentricity was not considered while more than two wheel loads were exerted on the concrete pavement, which can be overcome by using Finite Difference Method. With FDM, the stress and displacement distributions of any parts of the cement concrete slab can be easily achieved. The results indicate that when the concrete slab with void beneath the slab corner was assumed to be a cantilever slab, regardless of calculation by traditional method or by FDM, the cement concrete pavement will be destroyed even under the condition of minimum traffic grade. The fatigue stress and road deflection obtained by FDM are bigger than that obtained by the traditional formula, so bigger safety factor should be employed in the road design. 相似文献
11.
To optimize properties of the crushed rock is a simple and effective method to control the reflective cracking.There are some measures to reduce the shrinkage of the crushed rock,such as: decreasing water content and cement percentage,reducing surface tension of water.The test study shows that shrinkage resistance of the crushed rock base can be improved by mixing with fly ash,water reducing agent and shrinkage reducing agent each other,it will be better for the crushed rock to mix with fly ash,water reducing agent and shrinkage reducing agent proportionally. 相似文献
12.
The influences of the monocyclic aromatic high range water reducers on cement hydration were evaluated from four factors, such as hydration heat, hydration products, pore structure, microstructures of cement pastes. With measurement of hydration heat by the TAM Ai, it was found that monocyclic aromatic high range water reducer may delay early hydration and significantly decreased early hydration heat. And the monocyclic aromatic high range water reducers tended to increase porosity and pore volume of cement pastes with MRI analysis, while pore size distribution did not change remarkably. With analysis of XRD、TG DTA and SEM, it was shown that the monocyclic aromatic high range water reducers could restrain the production of Ca(OH)2 and Hydrated Calcium Silicates in the hydration process without affecting the end products, and refine the hydration products, such as Ca(OH)2, C S H gel and ettringite crystals. 相似文献
13.
The effects of initial high humid air curing, standard water curing and sealed curing on thaumasite form of sulfate attack (TSA) of cement based materials were studied.The Erosion products after 180 days attack in sulfate solution were analyzed by the way of X ray diffraction(XRD) and fourier transform infrared spectroscopy(FTIR).And it was found that the TSA of the cement stone was delayed in high humid air resulting from that CaCO3 generated from carbonation was filled in the pores of the specimens, forming a compacted surface and restricting SO42- intrusion.In comparison, the extent of TSA of the specimens cured in sealed condition was most severe resulting from that large amount of inter defects in specimens for the lower hydration degree, and SO42- ions could intrude into specimens more easily. 相似文献
14.
Aiming at the lack of the current determination method for voids in practical engineering applications, in order to accurately quantify the voids beneath cement slab, the determination method was proposed with slab edge slab center deflection difference and slab corner slab center deflection difference in the same cement slab for voids.Three dimensional models were set up using the ANSYS finite element method for voids beneath slab corner and slab edge.And the load was simulated with FWD test results.Thereafter, the deflection values were calculated in slab center, slab corner, slab edge under different void depth, void area and load transfer capacity.And the range of deflection diffidence was obtained.With Yantai Weihai expressway, detection data for deflection using Falling Weight Deflectometer were statistically analyzed.And the criteria and correction factors of load transfer capacity were given with simulation and samples analysis.The feasibility of criteria was verified by actual test data.It is found that the simulation values and the test values are in good agreement.The accuracy of void determination by lab edge slab center deflection difference and slab corner slab center deflection difference are 88.5% and 84.6%, respectively, which meet the engineering requirements.The voids were determined under the same conditions with the elimination of deflection variability. 相似文献
15.
Cementation Effect with Cement during Cold In Place Recycling System of Asphalt Pavement 总被引：1，自引：0，他引：1
Different kinds of structures of RAP and different contents of cement were prepared. By means of standard compaction test, unconfined compressive strength, water stability, modulus and SEM test, the cementation effect with cement was studied. It was shown that the maximum dry density of RAP mixture rose from 1.91g/cm3 to 2.00g/cm3 with the increase of cement content when A/S was 0.4. The maximum dry density of RAP mixture would rise when adding more asphalt. The unconfined compressive strength rose from 1.48MPa to 2.63 MPa and then down to 2.28MPa when cement content was 6%. The best property could be got when A/S was 0.4 and the cement content was 6% with 9.5% water. The compressive strength of RAP mixture declined after it was cured in water for 24 h, but it had the same tendency with those of which had not been maintained in water. And it is also found that RAP does not obtain better stabilities in high temperature with modular test. From SEM test, it is shown that ettringite and C S H interlace and form the netted structure, and the aggregate would be enwrapped to increase the strength. 相似文献
16.
The effect of water to cement ratio, fiber types and content, cement types on the bending performance of the extruded fiber reinforced cementitious board were studied. And it was found that polyvinyl alcohol (PVA) fibers can significantly improve the ductility of the board compared with polypropylene (PP) fibers. As PVA fiber content achieved 1.7%, the strain hardening and multiple cracking were occurred on the extruded board, while strain softening were shown on PP fiber reinforced cement board. The difference between the two kinds of board was from the differences of the mechanical properties of the two fibers. In addition, taking the fiber reinforced extruded board as base, the ultimate bending strength, as well as and the corresponded deflection and the resistant to chloride iron penetrating, was improved for a composite beam with fiber board and concrete compared with those of traditional concrete beam. 相似文献
17.
Taking cement as primary raw material, a porous hardened cement paste synthetic filter material was prepared by steam curing in a reaction kettle. The optimum process combination condition of the filter material was determined. By orthogonal experiment, the optimal combinations of technical conditions were determined: water-solid ratio is 0.25, and pore-forming agent/cement equals to 0.3 with steaming temperature at 180°C in the reaction kettle for 4 h. Effects of pH value, dosing quantity and the initial concentration of phosphorus on phosphorus removal by using the filter materials which prepared under the optimal conditions were tested. The results show that the phosphorus removal rate reaches all above 95.3% and the highest one is 99.8% when the initial concentration of phosphorus is 5~10 mg·L -1. When the amount of filter material is added 2.5 g/100 mL, under the experimental condition of pH neutral, the top phosphorus removal rate reaches 89.6% when the concentration is 50 mg·L -1. The analysis of adsorption kinetic process shows that the pseudo-second-order kinetic is fitted to the adsorption characteristics of filter material and the adsorption rate is controlled by the intra-particle diffusion. 相似文献
18.
The influence on the strength of cement mortars by adding emulsified epoxy is studied, and epoxy resin polymer cement mortars with excellent performances are made up through modifying ordinary Portland cement with emulsified epoxy and micro-fine slag. The microstructure of the epoxy resin polymer cement materials are studied and their action and mechanism are discussed by means of modern detection measures such as SEM, XRD. The experimental results indicate cement mortars modifying emulsified epoxy and micro-fine slag have higher compressive strength and flexible strength. The series effects of water-reducing, density, pozzolanicity, filling and solidification cross linking through the action together of epoxy organism and micro-fine slag can endow cement-based materials with perfect mechanic performance. The main hydration products in the system are C-S-H gel and micro-crystal hydrated calcium aluminate. When epoxy resin is solidified, the organism is network. No Ca(OH) 2 has been found. 相似文献
19.
The cement paste added with chemical admixtures is kept out (5±2)℃, 5% in mass MgSO4 corrosion solution in 300 d of immersion. Its visual appearance, compressive strength and erosion products are studied. Its erosion products are analyzed by the way of X ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). It shows that the calcium formate can delay the TSA of harden cement paste to occur, but can not stop the development of TSA. The resistance of mortar to TSA increases with the raise of calcium formate in the range of 03% to 07%. The reason why barium nitrate can inhibit the formation of thaumasite is that it can combine with SO2-4 which is essential for the forming of thaumasite. Thus, the TSA of mortar is reduced in degree. The harden cement paste shows good resistance to TSA when barium nitrate is approximately 1% of cement. 相似文献
20.
In order to prepare aerated concrete with alkali-phosphorus slag and better use of industrial waste, the powder composition of the slurry was investigated. The impacts of certain factors on aerated concrete, including the foaming agent, sodium silicate modulus, alkali content and the temperature of alkali solution also were investigated using single-factor test methods. The results indicate that: the cement and fly ash in powder have impacts on the pouring stability of slurry, and the bulk density of aerated concrete is impacted by the amount of foaming agent, sodium silicate modulus and alkali content. In the experiment, aerated concrete with bulk density in range of 535~887 kg/m3 and compressive strength of 6~9.5 MPa was produced; its mechanical performance conforms to the requirements of the standard GB 11968 2006. 相似文献