Research on the Low-carbon Cementitious Materials:Effect of Triisopropanolamine on the Hydration of Phosphorous Slag and Steel Slag

Cement,phosphorous slag(PS),and steel slag(SS)were used to prepare low-carbon cementitious materials,and triisopropanolamine(TIPA)was used to improve the mechanical properties by controlling the hydration process.The experimental results show that,by using 0.06%TIPA,the compressive strength of cement containing 60%PS or 60%SS could be enhanced by 12%or 18%at 28 d.The presence of TIPA significantly affected the hydration process of PS and SS in cement.In the early stage,TIPA accelerated the dissolution of Al in PS,and the formation of carboaluminate hydrate was facilitated,which could induce the hydration;TIPA promoted the dissolution of Fe in SS,and the formation of Fe-monocarbonate,which was precipitated on the surface of SS,resulting in the postponement of hydration,especially for the high SS content.In the later stage,under the continuous solubilization effect of TIPA,the hydration of PS and SS could refine the pore structure.It was noted that compared with portland cement,the carbon emissions of cement-PS-TIPA and cement-SS-TIPA was reduced by 52%and 49%,respectively.

Ferro-vanadium Slag in Improving Inner Chloride Solidification Rate of Cement Materials

We investigated the effects of ferro-vanadium slag(FVS)as a supplemental cementing material which can dissolve a large amount of active aluminum phases without excessive pretreatment or excitation to enhance the inner chloride solidified rate(CSR)of cement-based materials.Cement-FVS pastes with 0-30%content of FVS was designed,and the CSR was examined.Hydrates at different curing ages were studied by X-ray diffraction(XRD)and thermo-gravimetric analysis(TGA);hydration heat and^(29)Si nuclear magnetic resonance(^(29)Si-NMR)were tested to analyze the hydration degree of the system;mechanical properties in cement-FVS system were evaluated by compressive strength test,pore structure and the fractal regression.Results revealed that the incorporation of FVS could greatly promote the CSR of cement-FVS system.Compared with the control groups,30%dosage of FVS could increase the CSR by 69%at 3 d,47%at 7d,36%at 28 d and 34%at 60 d.It was demonstrated that the incorporation of FVS could enhance the chemical solidifying ability of chloride,and the main reason was the promoted generation of Kuzel’s salt and the Friedel’s salt in hydrate products,and the enhanced chloride migration resistance capacity by increasing the volume of gel pores in the cement-FVS system.Considering the influence of FVS on strength performance,this paper suggested that the suitable dosage of FVS as a supplemental cementing material was around 10%.The study in this paper might provide one efficient path to promote the chloride solidifying capacity of cement-based material and meanwhile the comprehensive utilization of FVS.

青少年短跑的速度训练探究

短跑作为田径运动的基础项目,对青少年的速度、力量、柔韧性等综合素质要求较高。该文针对青少年短跑速度训练,分析青少年短跑速度训练的要点,提出青少年短跑速度训练的策略,包括创设多样化训练场景、运用游戏化训练方法、实施周期性训练计划和引入科技辅助与数据监控,以提升青少年短跑速度表现与整体竞技水平。

头针为主治疗中风后失语临床及机制研究进展

通过检索近10年头针为主治疗中风后失语(PSA)临床研究文献,对头针应用概况、头针操作方法、头针临床疗效、头针机制研究四个方面进行归纳分析,总结头针为主治疗中风后失语的临床及机制研究现状。结果表明,头针应用以焦氏头针最为广泛;头针治疗PSA疗效显著;头针结合语言康复治疗是目前的研究热点;《汉语失语症检查法》量表是目前最常用的结局指标;头针机制主要针对脑电活动、脑部代谢产物、相关血液流变学指标的影响进行研究。但存在头针操作不规范、真实世界研究较少、疗效评价不统一且缺乏中医特色评价及相关核心结局指标集、作用机制研究偏少等问题。应当进一步规范化、标准化头针操作,开展更多真实世界研究,构建中医治疗PSA核心结局指标集并采用循证医学方法评价头针为主治疗PSA的疗效、开展更多机制研究。

Ranking method for the reciprocal judgment matrix based on the unascertained three-valued judgments

The ranking problem is studied when the pairwise comparisons values are unoertain in the analytic hierarchy process （AHP）. The method of constructing the judgment matrix is presented when the pairwise comparisons values are denoted by the unascertained three-valued reciprocal scales. By turning the reciprocal judgment matrix into attribute judgment matrix, the method to check the consistency of the pairwise comparisons judgment matrix and the calculation method of weighting coefficients are given. Finally, numerical examples are given to illustrate the effectiveness of the proposed method.

Use of Different Barium Salts to Inhibit the Thaumasite Form of Sulfate Attack in Cement-based Materials

We investigated the effects of different barium compounds on the thaumasite form of sulphate attack（TSA）resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhibition mechanisms within different types of barium salts,namely BaCO_3 and Ba（OH）_2,on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%,1.0%,and 1.5% were immersed in 5%（by weight）MgSO_4 solution at 5 ℃ to mimic TSA.Appearance,mass,and compressive strength of the mortar samples were monitored and measured to assess the generaldegradation extent of these samples.The products of sulphate attack were further analyzed by XRD,FTIR,and SEM,respectively.Experimentalresults show that different degradation extent is evident in allmortars cured in MgSO_4 solution.However,barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form,which may be due to their solubility difference in alkaline cement pore solution,and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controlsamples.

Effect of Silica Fume on the Thaumasite Form of Sulfate Attack on Cement-based Materials

Thaumasite form of sulfate attack（TSA） can be observed in cement containing limestone under sulfate condition at low temperature. Mixing with suitable mineral admixture could be a good choice to improve the TSA resistance performance of cement-based materials. We investigated the durability performance of limestone-cement mortars reinforced with silica fume（SF） in 5% MgSO_4 solution at 5 ℃. The mortars, which were immersed in aggressive condition, were prepared with 2%, 4%, 6%, 8%, and 10% cement replacement by SF at a fixed water-to-binder ratio. Appearance, compressive strength, change of length and mass and corrosion products were investigated to evaluate the TSA resistance performance of SF based specimens. The results showed that specimens in the absence of SF almost disintegrated. Increasing SF dosage can reduce the degree of deterioration of SF mortars in TSA environment. Mortar mixtures with more than 6% SF merely show slight degeneration in relation to macroscopic and microscopic tests and characterizations.

Microstructure and Characterization of Capric-stearic Acid/Modified Expanded Vermiculite Thermal Storage Composites

In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface modifier, and organic EV（OEV） with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic（CA-SA）/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC）, thermal gravimetry（TG）, and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density（112.52 J/g）, suitable melting temperature（20.49 ℃）, good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.

Polymorph Transformation of Tricalcium Silicate Doped with Heavy Metal

The aim of the present study was to investigate the influence of heavy metals on the polymorph transformation of tricalcium silicate.Heavy metal（0.1wt% to 3.0wt%） of Cr,Zn,Cu,Ni and Pb（in oxides form） was added into the raw mixtures and then sintered together three times at 1450 ℃ for 2 h.The f-CaO content of doped C3S was determined by the glycerol-ethanol method,and their polymorph transformation was investigated by means of XRD and FTIR.Thermal analysis（DTA/DTG） was conducted to determine the reaction temperatures and mass losses during the sintering process of raw mixtures.The concentration of heavy metal in C3S after sintering was determined by ICP-AES.The experimental results indicate that heavy metal doping contributes to a higher symmetry of C3S except for Pb.Addition of up to 3.0wt%,Cr will lead to a decomposition of C3S into C2S and CaO;Zn will cause a transformation from T1 to M2 polymorph,and then to R polymorph;Cu and Ni cause a gradual transformation from T1 to T2 and then to M1 and/or M2 polymorph.During the sintering process,all the Pb releases into atmosphere because of evaporation.

黄姜废渣发泡陶瓷的制备及其性能研究

发泡陶瓷作为一种新型建筑墙体材料,具有轻质保温的优良特性,有利于实现建筑节能。以黄姜废渣为主要坯料,掺加适量麻城石粉优化坯料组分,并以SiC为发泡剂,通过混料、压片、烧结等工艺实现了一种新型闭孔发泡陶瓷的制备。主要研究了烧成制度、成型压力、发泡剂掺量、石粉掺量对黄姜废渣发泡陶瓷宏观性能及其微观特征的影响。试验结果表明,在烧成温度1130℃、升温速率5℃/min、成型压力1 MPa、SiC掺量0.5%、麻城石粉掺量40%(均为质量分数)的工艺条件下,黄姜废渣发泡陶瓷制备效果最佳,综合性能最优。

纳米CaCO_3对硫铝酸盐水泥水化硬化特性的影响

研究了纳米CaCO_3(NC)对硫铝酸盐水泥(SAC)凝结时间、抗压强度、水化热、水化产物和微观形貌的影响。结果表明,NC可促进SAC的凝结,缩短初凝和终凝时间间隔;显著提高SAC各龄期的抗压强度;缩短SAC的水化诱导期,使水化第一、第二放热峰值分别提高了15.4%和18.9%,并增加了水化放热量;NC在SAC结构中起微集料成核效应和填充效应,提高了水化产物钙矾石(AFt)的结晶度,从而促进SAC的凝结和水化,并使硬化浆体呈整体化的均匀致密结构,提高了SAC净浆的强度。

聚乙烯醇纤维改性EPS混凝土性能试验研究

以再生EPS颗粒作为轻骨料,制备出EPS轻质混凝土,选用聚乙烯醇纤维(PVA)作为改性材料,通过试验研究了不同PVA体积掺量对EPS混凝土的流动度、吸水率、力学性能、导热系数、干缩以及抗冻性的影响,探讨其改性机理。结果表明,PVA的掺入使EPS混凝土流动度持续降低,但对容重影响不大。与空白样相比,当PVA掺量为0.8%时,吸水率降低了27.7%;28 d抗压强度、劈裂抗拉强度和抗折强度分别提升了18.5%、57.1%和50%;在掺量不超过1.2%范围内,拉压比持续增大,PVA对EPS混凝土的抗裂增韧作用显著。其导热系数逐渐降低,混凝土保温隔热性提高。综合PVA对EPS混凝土性能的影响规律及机理分析,确定最佳掺量为0.8%。

EPS-磷石膏复合体系的性能优化研究

利用发泡聚苯乙烯(EPS)和磷石膏制备轻质板材具有节能、保温、吸声、调湿等诸多优点。但在成型中,由于EPS密度小且憎水,不易被石膏浆体润湿包裹,出现分层离析,导致和易性不良。为了改善EPS-磷石膏体系中EPS颗粒与磷石膏界面的粘结性能和力学性能,采用三乙醇胺、聚乙烯醇及乙烯-醋酸乙烯酯对EPS进行表面改性并采用三类工艺实现硫铝酸盐水泥对EPS的造壳。通过测试接触角和粘结强度发现,当三乙醇胺∶乙烯-醋酸乙烯酯为1∶1时,改性效果最好,改性陈化分散工艺对硬化体强度的增强效果最优。试验结果为进一步拓宽磷石膏-EPS复合体系的应用提供了技术参考。

缓凝剂对磷建筑石膏-普通硅酸盐水泥复合体系性能的影响及其机理研究

磷建筑石膏(β-HPG)力学性能差,凝结硬化快,已有研究表明用普通硅酸盐水泥(OPC)替代部分β-HPG可改善其力学性能,但对此复合体系工作性能的调控作用及机理研究尚不明确。本文探讨了三种缓凝剂对β-HPG-OPC复合体系性能的影响,通过测试凝结时间和抗压强度来表征性能变化,通过分析水化热曲线、电导率曲线、XRD谱和SEM照片来讨论作用机理。研究结果表明,三聚磷酸钠(STPP)对复合体系基本无缓凝作用,蛋白质类SC缓凝剂(SC)和柠檬酸(CA)的缓凝作用均较好,其中SC对初凝时间的延缓作用较好,CA对终凝时间的延缓作用更佳。CA使二水石膏晶体的形貌发生改变,导致体系抗压强度显著降低;SC对二水石膏晶体的粗化作用使体系形成相对致密的微观结构体,对抗压强度影响较小。研究结果将为β-HPG-OPC复合体系工程应用提供重要参考,有助于推进β-HPG在工程中的高附加值利用。

磺酸基改性聚丙烯酸类增稠剂的性能研究

混凝土增稠剂作为一种混凝土外加剂,可以提高混凝土的工作稳定性,改善混凝土的离析、泌水等问题。利用磺酸基对聚丙烯酸(PAA)类增稠剂进行改性,制备出一种增稠效果优良的增稠剂。利用红外光谱分析仪(FTIR)表征了聚合物结构与成分,研究了改性PAA对水泥浆体流变性能的影响,并通过TOC(总有机碳吸附)、Zeta电位、电导率、DLS(动态光散射)等手段分析了聚合物在水泥颗粒表面的吸附行为以及聚合物在水泥孔溶液中的构象,并据此提出改性PAA的作用机理。结果表明:磺酸基改性PAA会增加掺入聚羧酸减水剂(PCE)浆体的塑性粘度,降低浆体流动度,且磺酸基改性PAA会增大液相中的聚合物构象粒径,有利于增大浆体粘度,另外,长链状的磺酸基改性PAA会提供桥接作用增大水泥颗粒之间的相互作用,增大水泥浆体的塑性粘度。

改性硅藻土调湿性能研究及其在EPS-磷石膏体系中的应用

由工业固废制备轻质节能建筑材料的同时,实现其功能性,是拓宽其应用途径的重要方面。本文中使用CaCl 2溶液对硅藻土的调湿性能进行改性,并将改性硅藻土应用到EPS-磷石膏体系中。实验结果表明:当使用质量浓度为30%的CaCl 2改性时,改性硅藻土48 h吸湿率可达到192.2%,48 h放湿率为32.81%;当改性硅藻土掺量为20%时,EPS-磷石膏硬化体的吸放湿性能相对最优,但会对硬化体的强度产生一定影响;CaCl 2的使用,使硅藻土的平均孔径增大,且CaCl 2的化学吸附被认为有效提高了硅藻土的调湿能力。

基于响应面法优化硫铝酸盐水泥体系性能研究

基于响应面法对硫铝酸盐水泥-普硅水泥-粉煤灰-硅灰四元体系进行试验设计,分别以凝结时间、3 d抗压强度及28 d抗压强度为响应值,探究硅酸盐水泥、粉煤灰和硅灰部分替代硫铝酸盐水泥时体系凝结时间、3、28 d抗压强度的变化规律。建立四元体系凝结时间和抗压强度预测模型,并对模型进行了回归分析和方差分析。结果表明,在保证3 d抗压强度优良的同时,28 d抗压强度最佳的各因素最佳水平为:普通硅酸盐水泥5%,粉煤灰5%,硅灰6%。响应曲面分析法可以对硫铝酸盐水泥基胶凝材料配合比进行优化。

亚硝酸钙对硫铝酸盐水泥水化硬化过程的影响

利用维卡仪、水化热、XRD和DTG等测试手段,研究亚硝酸钙(Ca(NO2)2)对硫铝酸盐水泥(SAC)初凝时间和终凝时间、力学性能、水化放热速率及水化产物的影响.结果表明:当亚硝酸钙的质量掺量为1.2%时,可显著缩短初凝时间和终凝时间,加快硫铝酸盐水泥的凝结;明显提高硫铝酸盐水泥早期的抗压强度,对后期抗压强度的提高幅度较小,标准养护条件下1 d和28 d抗压强度分别提高25.0%和6.1%;使水化第一、第二放热峰值分别提高35.9%和34.3%,并增加水化放热量;亚硝酸钙的溶解改善硫铝酸盐水泥浆体系统的水化环境,有利于水化产物钙矾石(AFt)的结晶,从而促进水化并提高抗压强度.

TiO_2纳米颗粒对水泥-粉煤灰体系水化硬化及氯离子侵蚀的影响

利用微量热分析、X射线衍射(XRD)、差热分析(DSC)、扫描电子显微镜(SEM)、压汞测孔仪(MIP)等手段研究了TiO_2纳米颗粒对水泥粉煤灰体系水化硬化以及抗氯离子侵蚀的影响。研究发现:TiO_2纳米颗粒的异相晶核效应和微集料填充效应协同作用,促进了水泥熟料的水化,加快了粉煤灰的二次水化进程并降低了硬化水泥石的孔体积,使水泥粉煤灰材料的微观结构更加均匀密实,提高了水泥粉煤灰材料的力学性能和抗氯离子侵蚀性能。

纳米SiO_(2)对钢渣水泥基胶凝材料的影响

钢渣和水泥具有相似的矿物组成,可以作为一种潜在的胶凝材料,然而钢渣掺量较高时并不利于混凝土早期性能的发展。以钢渣质量分数为30%的钢渣水泥基胶凝材料为研究对象,探讨纳米SiO_(2)对其早期性能的影响。主要通过测量流动度、凝结时间和抗压强度评估物理力学性能,并利用微量热分析、X射线衍射(XRD)、差热分析(DSC-TG)等方法对掺有纳米SiO_(2)的钢渣水泥基胶凝材料的水化过程和水化产物进行分析。结果表明,当纳米SiO_(2)掺入的质量分数为3%时,纳米SiO_(2)可充分发挥火山灰活性,消耗大量Ca(OH)_(2),同时由于纳米SiO_(2)颗粒的结晶成核作用和微集料填充作用,促进了钢渣和水泥的水化,水化初期的放热速率有所提高,从而提高钢渣水泥基胶凝材料的力学性能,28 d的抗压强度提高了14.0%。