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1 Research on Shearing Strength and Compressive Resilient Modulus Experiment of Asphalt Concrete

WANG Gang , LIU Li ping , SUN Li jun

2012(2):279-282. DOI: 10.3969/j.issn.1007 9626.2012.02.026

[Abstract](5980) [HTML](0) [PDF 0.00 Byte](120)

Abstract:
Uniaxial penetration and compressive resilient modulus tests of the high modulus asphalt concrete(CHMAC), SBS modified asphalt and 70# plain asphalt concrete under the condition of 15,20,40,60 ℃ have been performed, and the cohesion c of asphalt concrete has been calculated with the result of uniaxial compressive test. It can be found from the test that the HMAC has relatively high shearing strength，cohesion and compressive resilient modulus under various temperature conditions and especially at high temperatures. The regression equation was obtained through the correlation analysis of each index, which can be used to convert shearing strength to compressive strength, c values and compressive resilient modulus.

2 Experimental Study of Structural Steel Constitutive Relationship under Cyclic Loading

SHI Yong jiu , WANG Meng , WANG Yuan qing

2012(3):293-300. DOI: 10.3969/j.issn.1007 9629.2012.03.001

[Abstract](5234) [HTML](0) [PDF 0.00 Byte](147)

Abstract:
In order to study the seismic performance of steel structure in China and look for the constitutive relationship of steel under cyclic loading, a variety of loading was imposed on total 50 specimens of Q235B and Q345B steel and their monotonic behavior, hysteretic behavior, macro and micro failure modes, ductility characteristics and cumulative damage degradation were investigated; Ramberg Osgood model was used to fit the curve of cyclic loading and then the one dimensional stress strain skeleton curves of Q235B and Q345B under cyclic loading were obtained; based on the Chaboche plastic constitutive model for steel, two material parameters of constitutive models were obtained from experimental data calibrated with ABAQUS which provided an important basis to accurately calculate the response of future structures under earthquake. The results show that the response of steel under cyclic loading and the monotonic loading are quite different, therefore, the skeleton curve under cyclic loading plays an important role for accurate numerical simulation; cyclic loops and amplitudes seriously affect the fracture ductility of specimens and the failure strain under cyclic loading cannot be determined in accordance with the monotonic loading.

3 Water Sorptivity of Steam Curing Concrete

HE Zhi min , LONG Guang cheng , XIE You jun , LIU Jun zhe

2012(2):190-195. DOI: 10.3969/j.issn.1007 9629.2012.02.008

[Abstract](4912) [HTML](0) [PDF 0.00 Byte](82)

Abstract:
Initial surface absorption test(ISAT) method was employed to investigate the water sorptivity of steam curing concrete as well as the effects of binder types, curing condition and steam curing technology on capillary absorption coefficient of concretes. The corresponding mechanisms and technical measurements reducing capillary absorption role of steam curing concrete were studied. Results indicate that, compared with standard curing concretes, a much higher water absorption gradient from exposure surface to interior of steam curing concretes is observed, which results from the bad effects of elevated temperature on the top surface directly exposed to steam during steam curing period. The capillary absorption coefficient of steam curing concrete and the corresponding gradient of capillary absorption from exposure surface to interior both can be decreased by incorporating a compound of fly ash and slag or silica fume, using such technical measurements as subsequent water curing and/or water retaining coverage.

4 Preparation of Powder Polycarboxylate Superplasticizer

麻秀星 , 钱觉时 , 李苑 , 邓成 , 方云辉

2011(6):829-833. DOI: 10.3969/j.issn.10079629.2011.06.021

[Abstract](4716) [HTML](0) [PDF 1.07 M](6944)

Abstract:
The preparation of powder polycarboxylate superplasticizer by centrifugal spray drying process was discussed. The powder solid content(by mass) of the product can reach 99%. Through infrared spectroscopy the carbonyl group has been shown to be partly decomposed during the drying process which has only limited influence on the performance of the powder with the result that its performance is at the same level compared to the liquid superplasticizer. Based on single factor experiments, the major parameters affecting the drying process were discussed and the appropriate process conditions were obtained, e.g. the import air temperature of drying chamber must be controlled at 180220℃；the spraydrying feed temperature controlled at 2040℃, and solid content of polycarboxylate superplasticizer fed is in the range of 20% to 60%.

5 Preparation of Sulphoaluminate Cement from Municipal Solid Waste Incineration Fly Ash and Its Hydration Properties

施惠生 , 吴凯 , 郭晓潞 , 邓恺 , R.TRETTIN , 张震

2011(6):730-736. DOI: 10.3969/j.issn.10079629.2011.06.002

[Abstract](4683) [HTML](0) [PDF 1.19 M](5312)

Abstract:
Municipal solid waste incinerator(MSWI) fly ash was successfully used as a raw material in sintering sulphoaluminate cement clinker in the laboratory. The clinkerization process, morphology and compositions of the clinker were investigated. The hydration properties of sulphoaluminate cement and the toxicity leaching characteristics of heavy metals were also studied. The results show that the good quality clinkers in which C4A3S and C2S are presented as major phases can be sintered by using the MSWI fly ash as raw material, and the optimal amount of MSWI fly ash in the raw mix is about 30%. Microstructure of produced clinker was loose and lacunary and it appeared to be irregulartiny crystal. The sulphoaluminate cement with reasonable strength can be prepared by grinding the clinker with appropriate amount of gypsum. Porosity and mean pore diameter of harden cement paste decrease with the curing age. The results also indicate that the concentrations of all the investigated elements in the leachates are far below the regulatory limit up to 28 d, and the produced cements would not present a leaching hazard to environment.

6 Influence of Carbonation on Microstructure of AlkaliActivated Slag Cement Pastes

何娟 , 杨长辉

2012(1):126-130. DOI: 10.3969/j.issn.10079629.2012.01.024

[Abstract](4561) [HTML](0) [PDF 0.00 Byte](59)

Abstract:
In view of the phenomena that no Ca（OH）2 exsits in the hydration products of alkalislag cement and its carbonation is more serious, water glass was selected as the alkali activater, and XRD and SEM were adopted to study carbonation products and microstructure of alkalislag cement pastes, while the pore structure was researched by nitrogen adsorption. The results show that the carbonation takes place directly on the CSH gel and calcium carbonate, the carbonated product of alkalislag pastes exists mainly in the form of calcite. After carbonation, the Ca/Si of CSH gel decreases, while surface area of the pastes increases and the average pore diameter reduces. The change in cumulative volume of pores varies with modulus of water glass.

7 Development of Shrinkage and Internal Moisture in Cement Paste, Mortar and Concrete at Early Age

Zhang Jun , Chen Hao-Yu , Hou Dong-Wei

2011(3):287-292.

[Abstract](4514) [HTML](0) [PDF 1.47 M](5903)

Abstract:
The development of free deformation and internal moisture in cement paste, mortar and concrete were experimentally investigated. The results show that the deformations of cement paste, mortar and concrete at early age all exhibit plastic swelling at initial several hours after casting and then shrinking with a gradually reduced rate. The end point of swelling may be corresponding to the transformation point of plastic state to solid state and this point can be defined as setting time of the cement based materials. The development of shrinkage starting from setting point of the three kinds of cementitious materials exhibits at first a fast developing stage(stage Ⅰ) and is followed by a relatively slow developing stage(stage Ⅱ). The restraint effect of aggregates on shrinkage is significant only in the stage Ⅱ. In stage Ⅰ a similar shrinkage values are observed on the three kinds of materials. The development of moisture inside cement paste, mortar and concrete can be described as a vapor saturated stage with saturated moisture followed by a stage in that internal moisture is gradually reduced. The shrinkage developed within stage Ⅱ can well correlate to the reduction of internal moisture.

8 Rheological Characteristics of Sodium Silicate Solution and Its Effects on the Performance of Geopolymer Slurry

文梓芸 , 晏锦 , 殷素红

2011(6):723-729. DOI: 10.3969/j.issn.10079629.2011.06.001

[Abstract](4307) [HTML](0) [PDF 1.83 M](5892)

Abstract:
The effect of modulus, mass fraction and temperature of sodium silicate solution(SS) on the rheological characteristics of SS and geopolymer slurry(GS) were analyzed by means of viscometer and rheometer. Meanwhile, the effect of SS modified by ultrasonic on the workability of GS was studied. The results show that the viscosity of SS for 2.2 modulus get the minimum value in ambient temperature(1825℃), but the effect of modulus on viscosity of SS is gradually weaker with the raise of temperature. When SS is in the true solution(highionized) zone(modulus<1.8), the difference of GS viscosity of different SS modulus is little, while in the water glass(SiO2polymerized) zone(modulus>2.2), the viscosity of GS increases sharply with the increase of modulus of SS. With increasing of the mass fraction of SS, both viscosity of GS and SS are all increased.The viscosity of GS gets the minimum value at 30℃ in different SS modulus. The SS modified by ultrasonic could improve the fluidity of GS and increase the compressive strength of geopolymer.

9 Comparative Study on Anti-aging Performance of Asphalt Based on Dynamic Aging Process

ji xiao ping , hou yue qin , xu hui , zheng nan xiang , tan xue zhang

2013(2).

[Abstract](4117) [HTML](0) [PDF 0.00 Byte](6056)

Abstract:
The purpose of this paper is to use dynamic characterization model to evaluate the dynamic process of asphalt aging and compare the pros and cons of different asphalt. First, the RTFOT aging tests at different aging time for four kinds of asphalt are carried out and the aging test data are fitted with dynamic characterization model. As a result, the aging parameters and aging equation of penetration, ductility, softening point and viscosity of different asphalt are determined. Then, grey relational evaluation method is used to evaluate the anti-aging performance of different asphalt, which setting the aging parameters L and r of penetration, ductility, softening point and viscosity as the evaluation indexes. The results show that: the aging rate of penetration, softening point, ductility of asphalt reaches the peak at the beginning and becomes smaller as the variation of aging time and balances at last; The aging process of asphalt can be described accurately by dynamic characterization mode and parameters L and r can be a good characterization of aging degree and aging rate; The sort of anti-aging properties of the four asphalt is determined as following: the indoor modified asphalt is better than matrix 90 asphalt and better than SBS modified asphalt and better than matrix 70 asphalt.

10 Evaluation of Durability for Asphalt Mixture with Large Air Voids

耿韩 , 李立寒 , 孟庆楠

2011(6):767-770. DOI: 10.3969/j.issn.10079629.2011.06.009

[Abstract](3856) [HTML](0) [PDF 721.24 K](3318)

Abstract:
Experiments including Cantabro loss test for specimens of different temperature, Marshall test of immersion, and freeze thaw split test were designed to obtain proper test methods for the evaluation of antiscattering property and moisture sensibility of asphalt mixture with large air voids. Test results show that, Cantabro loss test is the proper experiment for this purpose. Furthermore, scattering loss at 20℃, frozen scattering loss at -18℃ and soaking scatterrng loss at 60℃ are suggested as evaluation index of antiscatterng property in normal temperature state, antiscattering property in frozen state and moisture sensibility respectively. The precision criterion for durability evaluation is that, the coefficient of variation of scattering loss at 20℃ or soaking scattering loss at 60℃ is no more than 10%, and that of frozen scattering loss at -18℃ is no more than 20% .

11 Isothermal Sorption of Recycled Aggregate Concrete andIts Influence on Drying Shrinkage

GUO Yuan chen , WANG Xue , HE Yun xiang

2012(3):386-391. DOI: 10.3969/j.issn.1007 9629.2012.03.018

[Abstract](3820) [HTML](0) [PDF 0.00 Byte](117)

Abstract:
Based on pore structure theory, a device for measuring the wetting properties of materials was designed. The effect of recycled aggregate replacement rate, and water reducer, expansive agent, fly ash dosage on isothermal absorption of recycled aggregate concrete was investigated. Through curve fitting, the function relationship of isothermal absorption curve of recycled aggregate concrete with different mix proportion was established. It is proposed that the water contact angle can be calculated from the initial absorption curve, and its impact on drying shrinkage of recycled aggregate concrete is analyzed. Research results show that the addition of recycled aggregate and superplasticizer lowers the contact angle of recycled aggregate concrete, and increases the drying shrinkage. The addition of fly ash improves the pore structure of concrete, and can reduce the wettability, which can help inhibit the shrinkage of recycled aggregate concrete; It is difficult to explain the shrinkage mechanism of expanded recycled concrete only from material wettability and pore structure theory.

12 Investigation on the Thermal Stability and Spectroscopic Properties of Er3+ Doped Fluorophosphate Glasses with Various P2O5 Content

YU Xiang-min , ZHU Ji-qian

2008(4).

[Abstract](3796) [HTML](0) [PDF 0.00 Byte](2)

Abstract:
制备了不同P2O5含量的GaF3-InF3-ZnF2-SnF2-CdF2-PbF2-ErF3-P2O5氟磷玻璃,对玻璃样品进行了差热、红外透过光谱及紫外吸收光谱分析.结果表明,随P2O5含量的增多,玻璃的形成能力得到提高,当P2O5含量为7%(摩尔分数)时,特征温度△T可达167℃;随P2O5含量的增多,玻璃的红外截止波长移向短波方向,紫外截止波长移向长波方向;在515 am光激发下,观察到了与其他基质玻璃不同的上转换发光现象,其蓝色上转换发光较强.

13 Study of Pore Size Distribution Measurement of Cementitious Materials by Nuclear Magnetic Resonance Cryoporometry（NMRC）

王中平 , 黄晨明 , 王弢

2012(1):6-10. DOI: 10.3969/j.issn.10079629.2012.01.002

[Abstract](3793) [HTML](0) [PDF 0.00 Byte](75)

Abstract:
The application of nuclear magnetic resonance cryoporometry（NMRC）for cementitious materials was analyzed. The constant in GibbsThomson equation that described the relationship between decrease value of ice melt point and pore size was obtained via measuring some mesoporous molecular sieve with certain pore size. The constant was then used to analyze the white cement samples with different mW/mC at different ages, and the possible error was discussed. The preliminary result shows that NMRC can give more details of pore size distribution of white cement samples than other methods, such as the volume of close micropore.

14 Impact of Paving Waiting Time on Performance of Epoxy Asphalt Mixture

黄明 , 黄卫东

2012(1):122-125. DOI: 10.3969/j.issn.10079629.2012.01.023

[Abstract](3654) [HTML](0) [PDF 0.00 Byte](113)

Abstract:
A large number of laboratory tests were carried out, which took high temperature, fatigue and moisture resistance as main test items. The research not only evaluated the impact of waiting time for paving on the performance of epoxy asphalt from three aspects, but also integrated these items and put forward suggestions on the value of waiting time for paving by the grey relationship analysis methods. The results indicate that if the waiting time for paving is less than 30 min, the performance of epoxy asphalt will remain unchanged; however, when the grey connection performance declines to 80%, it will take the longest waiting time for paving, which can be as long as 80 min. This method can be applied to the researches and developments of epoxy asphalt as well as the evaluation of engineering practice.

15 Study on Synthesis Technique and Properties of Amide Type Polycarboxylate Based Superplasticizer

孙振平 , 罗琼

2012(1):22-27. DOI: 10.3969/j.issn.10079629.2012.01.005

[Abstract](3630) [HTML](0) [PDF 0.00 Byte](93)

Abstract:
Synthetic process of amide type polycarboxylate based superplasticizer was studied. Polyether amine（PN220） and polyacrylic acid（PAA） were used as the monomers and directly polymerized into superplasticizer. The effects of the relative molecular mass of PAA, monomer ratio, polymerization temperature and time on waterreducing rate and fluidity retention of the product were investigated through experiments. The orthogonal experiment is designed to find out the optimal synthesis technique. The performance of the product is compared with the superplasticizer which is prevailing in the market and synthesized by polyethylene glycol monomethyl ether（MPEG） and methacrylic acid. The results show that the former has excellent slump retention and it is suitable for preparation of concrete demanding outstanding slump retention.

16 Function of Water in Different Types of Cementitious Materials

杨南如

2012(1):1-5. DOI: 10.3969/j.issn.10079629.2012.01.001

[Abstract](3565) [HTML](0) [PDF 0.00 Byte](112)

Abstract:
From the view point of chemistry, the function of water in different types of cementitious materials is analyzed. In some books about cement technology and cement chemistry, authors say:“It should be noticed, that the term, hydration, can not be used to describe the reaction between water and cementitious materials, even Portland cement.” In the fact that the reaction of water with cementitious materials may results in hydration and hydrolysis, water sometimes may only play the role of solvent to dissolve the reactants. Moreover the water is not the reactant, but is even the reaction product.

17 Effect of Decalcification on CSH Gel Microstructure in Cement Paste

He Zhen , Wang Lei , Shao Yi-Xin , Cai Xin-Hua

2011(3):293-298.

[Abstract](3514) [HTML](0) [PDF 952.15 K](4057)

Abstract:
Effect of decalcification on microstructure of CSH gel in ASTMⅠcement paste were studied by Xray fluorescence spectrometer(XRF), Xray diffraction(XRD), infrared spectroscopy with Fourier transform(FTIR) and 29Si MAS NMR with deconvolution technique. It is shown from test results that the decalcification process can be divided into two stages. When the molar ratio of CaO to SiO2 in the pastes at 3, 28d is lowered from~2.78 to~2.00, almost all of CH is removed and CSH gel is partially decalcified, the average chain length(ACL) of CSH is increased from 2.4 to 4.4 for 3d paste and from 2.9 to 5.8 for 28d paste respectively, and I(Q2)/I(Q1) is also increased. While the molar ratio of CaO to SiO2 in the pastes comes to~1.83, decalcification of CSH gel occurs. CSH polymerizes and I(Q2)/I(Q1) increases largely in this stage, which results in further increase of ACL to 6.2 for 3d paste and 9.9 for 28d paste. The mechanism of increase of CSH polymerization could be transformation of dimeric CSH toward highly polymerized CSH. However, Al doping could affect the stability of CSH microstructure. In molecular level, the existence of the pure bridging siliconoxy tetrahedrons in CSH is beneficial to the optimization of the microstructure.

18 Comparative Study on Cl- Penetration in Cracked High Ductility and Low Shrinkage Material and Steel Fiber Concrete

ZHANG Jun , ZHONG Hai tao , JU Xian chun , WANG Guan ming

2012(2):151-157. DOI: 10.3969/j.issn.1007 9629.2012.02.001

[Abstract](3492) [HTML](0) [PDF 0.00 Byte](110)

Abstract:
The effect of cracks in steel fiber concrete(SFRC) and high ductility and low shrinkage material(LSECC) on Cl- penetration was investigated by pre induced flexural cracks in concrete beams. The cracked beams with different crack width or tensile strains were then continuously soaked with 3%(by mass) NaCl solution or undergone drying and wetting cycles. The content(by mass) of Cl- in concrete at the locations of cracks was determined by drilling powder sample with electric hammer. The experimental results show that the influence of cracks on the Cl- penetration is very significant. The content of Cl- at the location of cracks in SFRC is 34 times compared to the place without cracks. The Cl- content in SFRC is increased with increase of the crack width for the specimens soaked for 30 d. At 60 d after soaked, the content of Cl- becomes almost constant irrespective of the penetration depth. Under drying and wetting conditions, the content of Cl- in SFRC greatly increases compared to those of continuously soaked. By contrast, LSECC can apparently reduce the content of Cl-, especially under drying and wetting conditions. The resistance to Cl- penetration for LSECC is obviously significant.

19 Study on Effectiveness of Electrochemical Realkalization for Carbonated Concrete

蒋正武 , 杨凯飞 , 潘微旺

2012(1):17-21. DOI: 10.3969/j.issn.10079629.2012.01.004

[Abstract](3442) [HTML](0) [PDF 0.00 Byte](89)

Abstract:
An experimental method of electrochemical realkalization for carbonated concrete was designed and two reasonable evaluation indexes for its effectiveness, pH value and migration content of sodium ion, were proposed. Further, effects of types and concentration of electrolyte solution, realkalization time on the effectiveness of electrochemical realkalization for carbonated concrete were investigated. The results show that the pH value increases but increase rate of pH value slows down with the increase of realkalization time. For the same electrolyte solution, the higher the electrolyte solution concentration, the higher the migration content of sodium ion in carbonated concrete after realkalization is. For the same concentration of different types of electrolyte solution, the migration contents of sodium ion in carbonated concrete after realkalization are different.

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