Multi-scale Modeling of the Effective Chloride Ion Diffusion Coefficient in Cement-based Composite Materials

N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone （ITZ） between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself. For the convenience of applications, the mortar and concrete were considered as a four-phase spherical model, consisting of cement continuous phase, dispersed aggregates phase, interface transition zone and their homogenized effective medium phase. A general effective medium equation was established to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure. During calculation, the tortuosity （n） and constrictivity factors （Ds/Do） of pore in the hardened pastes are n^3.2, Ds/Do=l.Ox 10-4 respectively from the test data. The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results; The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.

Properties and interfacial microstructure of cement-based materials with composite micro-grains

Silica fume, fly ash and nano-fiber mineral materials (NR powder) are employed to incorporate into cement-based materials. According to the grain grading mathematical model of cement-based materials, two packing systems, namely, spherical grading system and nano-fiber reinforced system were designed. Properties and interfacial microstructure of the two systems were studied according to secondary interface theory. It was shown that nano-fiber mineral materials can improve the grain grading of the admixture, increase the density of the system, improve the microstructure of the interface and the hardened paste, and enhance the uniformity of cement-based materials mixed with composite micro-grains and greatly increase their wearable rigidity and flexure strength. In this paper, two kinds of interface models, including spherical grain model and nano-fiber reinforced interface model of the cement-based materials mixed with composite micro-grains, were brought forward.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Smart Behavior of Carbon Fiber Reinforced Cement-based Composite

The electrical characteristics of cement-based material can be remarkably improved by the addition of short carbon fibers. Carbon fiber reinforced cement composite (CFRC) is an intrinsically smart material that can sense not only the stress and strain, but also the temperature. In this paper, variations of electrical resistivity with external applied load, and relation of thermoelectric force and temperature were investigated. Test results indicated that the electrical signal is related to the increase in the material volume resistivity during crack generation or propagation and the decrease in the resistivity during crack closure. Moreover, it was found that the fiber addition increased the linearity and reversibility of the Seebeck effect in the cement-based materials. The change of electrical characteristics reflects large amount of information of inner damage and temperature differential of composite, which can be used for stress-strain or thermal self-monitoring by embedding it in the concrete structures.

Synthesis of steel slag ceramics: chemical composition and crystalline phases of raw materials

Two types of porcelain tiles with steel slag as the main raw material （steel slag ceramics） were synthesized based on the CaO-A1203-SiO2 and CaO--MgO-SiO2 systems, and their bending strengths up to 53.47 MPa and 99.84 MPa, respectively, were obtained. The presence of anorthite, a-quartz, magnetite, and pyroxene crystals （augite and diopside） in the steel slag ceramics were very different from the composition of traditional ceramics. X-ray diffraction （XRD） and electron probe X-ray microanalysis （EPMA） results illustrated that the addition of steel slag reduced the temperature of extensive liquid generation and further decreased the firing temperature. The considerable contents of glass-modifying oxide liquids with rather low viscosities at high temperature in the steel slag ceramic adobes promoted element diffusion and crystallization. The results of this study demonstrated a new approach for extensive and effective recycling of steel slag.

Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.

Thermodynamic analysis and formula optimization of steel slag-based ceramic materials by FACTsage software

Using steel slag as a main raw material of ceramics is considered as a high value-added way. However, the relationship among the initial composition, ceramic microstructure, and macroscopic properties requires further study. In this paper, a series of ceramics with different slag ratios （0-70wt%） were designed, and the software FACTsage was introduced to simulate the formation of crystalline phases. The simulation results indicate that mullite is generated but drastically reduced at the slag ratios of 0-25wt%, and anorthite is the dominant crystalline phase in the slag content of 25wt%-45wt%. When the slag ratio is above 45wt%, pyroxene is generated more than anorthite. This is because increasing magnesium can promote the formation of pyroxene. Then, the formula with a slag content of 40wt% was selected and optimized. X-ray diffraction results were good consistent with the simulation results. Finally, the water absorption and bending strength of optimized samples were measured.

Corrosion resistance evaluation of highly dispersed MgO–MgAl2O4–ZrO2 composite and analysis of its corrosion mechanism: A chromium-free refractory for RH refining kilns

The corrosion resistance behavior of a highly dispersed MgO-MgAl2O4-ZrO2 composite refractory material is examined by testing with high-basicity and low-basicity RH(Ruhrstahl-Hereaeus)slags.The composite material exhibits greater resistance to the RH slags than the traditional MgO-Cr2O3 composite,MgO-ZrO2 composite,and MgO-MgAl2O4-ZrO2 composite.On the basis of the microstructural analysis and mechanisms calculations,the corrosion resistance behavior of the MgO-MgAl2O4-ZrO2 composite is attributable to its highly dispersed structure,which helps protect the high activity of ZrO2.When in contact with the slag,ZrO2 reacts with CaO to form the stable phase CaZrO3,which protects MgAl2O4 against corrosion,thereby enhancing the corrosion resistance of the composite.

Flexural behavior of composite beams after the ultimate limit state externally strengthened with CFRP sheets bonded with high-temperature resistant matrix

In this paper the alkali-activated slag cementitious materials(AASCM)which strength at 600 ℃ is larger than that of AASCM at room temperature,were prepared to paste CFRP sheets to strengthen four simply supported unbonded prestressed composite beams encased circular steel tube truss after ultimate limit state.Test on flexural behavior of these four beams was performed.Moreover,normal section load-bearing capacity of these beams and the curve load-deflection at mid-span were obtained.Experimental results show that it is feasible to strengthen concrete members with CFRP sheets bonded with AASCM.Based on the experimental results and theoretical study,computational method of stiffness is proposed for calculating bending rigidity and normal section load-bearing capacity of concrete simply supported beams strengthened with CFRP sheets bonded with AASCM.Formula of bending rigidity calculation was founded which results are in good agreement with testing data.

碱激发粉煤灰矿渣胶凝材料的流变性能

这是一篇陶瓷及复合材料领域的论文。为了研究碱激发粉煤灰矿渣胶凝体系在早期的流变特性,制备了不同粉煤灰和矿粉质量比以及碱激发剂含量的复合浆体,并且分别采用了微型坍落度筒和Brookfield DV3T流变仪测试其流动性和流变性,最后用等温量热仪测试了各组配比下浆体的水化放热速率。结果表明:当FA/GGBS比为3∶7时,碱激发剂NaOH含量为4%的浆体在所有配合比中流动度为较低。随着粉煤灰质量比和NaOH摩尔质量的升高,碱激发粉煤灰矿渣胶凝体系的流动度均有所上升,且屈服应力和塑性黏度有所下降。粉煤灰掺量的升高使得早期水化速率有所下降,而碱激发剂含量的增加则提高了水化放热峰值速率。

基于镁渣-水泥-脱硫石膏复合胶凝材料的砌筑砂浆制备及其性能

镁渣高效利用对于金属镁冶炼行业的可持续发展和环境保护具有重要意义。本文以镁渣、水泥和脱硫石膏为主要原料,设计和配制复合胶凝材料,并以此制备高性能砌筑砂浆。三元体系胶凝材料试验结果表明,以高掺量镁渣制备的胶砂试件28 d抗压强度可达35.6 MPa,脱硫石膏对镁渣-水泥胶凝体系起到了活性激发作用,尤其对28 d强度具有明显的促进作用。以镁渣-水泥-脱硫石膏复合胶凝材料制备的砌筑砂浆28 d抗压强度最高达25.32 MPa,满足JGJ/T 98-2010《砌筑砂浆配合比设计规程》中M25等级的要求。研究成果可为镁渣大规模资源化利用提供参考。

磷矿渣改性水泥基充填料的渗透性能及其微观结构

这是一篇陶瓷及复合材料领域的论文。采用碱激发混合法制备了4种不同磷矿渣掺量的水泥基充填料,对养护过程中的改性充填料开展渗透率、核磁共振(NMR)与电子显微镜扫描(SEM)实验。结果表明:随磷矿渣掺量增加,水泥基充填料试件的抗压强度呈现先增后减的变化趋势,渗透率呈现先减后增的非线性变化趋势,且两者均在4%时达到极值;经过养护1~28 d的充填料试件弛豫时间(T2)分布曲线均为双峰分布,代表小孔隙的峰占比超过80%,代表大孔隙的峰占比随养护时间增加而逐渐降低;根据SEM图像可以看出一定掺量的磷矿渣能够促进水化反应的发生,使得材料的孔隙显著减少;磷矿渣为4%时,水泥基充填料的密实度较好,抗渗性能和强度达到较佳,据此可以确定磷矿渣改性水泥基充填料的较佳掺量是4%。

基于固废磷化渣的复合型防腐阻锈剂对混凝土性能的影响

为了提高严酷环境下建筑的耐久性,研究了防腐阻锈剂和防腐阻锈混凝土。以三乙醇胺、硝酸铝和Ca(OH)2为原料,经化学反应,制备新型固体醇胺,再按一定质量分数将固体醇胺、固废磷化渣、石膏和苯甲酸钠混合、球磨,制得复合型防腐阻锈剂,将其掺入基准混凝土中,制得防腐阻锈混凝土,并研究其力学性能和防腐阻锈性能。结果表明:掺复合型防腐阻锈剂的防腐阻锈混凝土,抗压强度和抗折强度显著提高,抗渗等级达P12,碳化深度大幅降低,抗冷热干湿循环和抗冻融性能优异,用含防腐阻锈剂的海水混合液浸泡钢筋2年,钢筋无腐蚀行为。用复合型防腐阻锈剂制备的防腐阻锈混凝土能有效延缓建筑混凝土的腐蚀进程。利用固废磷化渣制备防腐阻锈剂,变废为宝,可为新型防腐阻锈剂的开发提供借鉴。

碱激发铜渣-粉煤灰复合胶凝材料的力学性能及水化机理研究

旨在探讨利用碱激发剂制备铜渣-粉煤灰复合胶凝材料的可行性及其性能表现。选择铜渣和粉煤灰作为主要原料,通过实验确定其最佳配比和激发剂种类及浓度,发现以7.5%的水玻璃为激发剂时,材料的力学性能最佳。过量的碱激发剂会导致返碱现象、增加与模具的粘合度及拆模困难,甚至降低成品强度,因此在生产过程中需严格控制激发剂的掺量。通过实验分析不同变量对材料性能的影响,包括原材料细度、激发剂浓度、养护条件等,确定了优化的制备工艺。实验结果表明,优化后的复合材料在28 d内的强度可达71 MPa,显著优于普通硅酸盐水泥。在早期强度发展迅速的同时,后期强度虽然增长缓慢,但整体性能依然优越。这种表现为其在实际工程应用中提供了理论依据和实践支持。结合微观结构分析和实际应用研究,揭示了硅铝酸盐凝胶的形成机制,进一步优化了配方和工艺。研究结果证明,该材料具有显著的环保效益和经济潜力。其广泛的应用前景不仅可以部分替代传统水泥,还能实现工业废弃物的高效资源化利用,推动建筑行业的可持续发展。通过不断优化技术和降低成本,碱激发铜渣-粉煤灰复合胶凝材料将在绿色建筑和环保材料领域发挥更大的作用。

多元固废基胶凝材料的组成优化及强度形成机理

采用钢渣粉、S95矿粉、粉煤灰和脱硫石膏为原材料,通过单纯形重心方法优化设计制备多元固废胶凝材料,以胶砂抗压、抗折强度试验分析了组成成分对固废胶砂力学性能的影响,采用X射线衍射(X-ray diffraction,XRD)、傅里叶红外光谱(Fourier transform infrared spectroscopy,FT-IR)和热重(thermogravimetric,TG)方法探究了多元固废基胶凝材料强度形成机理。结果表明:多元固废基胶凝材料(SFMD)的最佳掺配比为钢渣粉∶S95矿粉∶粉煤灰∶脱硫石膏=31∶38∶27∶4。多元固废基胶砂试件的力学性能随钢渣粉掺量的增加呈先升高后降低的趋势,S95矿粉对胶砂试件早期强度贡献较大,过量的粉煤灰掺入则不利于胶砂强度的形成。SFMD的红外吸收峰在969 cm^(-1)处出现了C-S-H中Si—O的伸缩振动峰,且SFMD中C-S-H的失重最多,该体系的各组分之间的协同效应较好。此外,脱硫石膏可以促使钢渣粉-S95矿粉-粉煤灰体系的协同水化反应更加彻底,生成提供强度的钙矾石。

基于体积特性的钢渣沥青混合料最佳油石比等体积设计方法研究

为了建立一种将玄武岩沥青混合料最佳油石比转化为钢渣沥青混合料最佳油石比的设计方法,首先,采用等体积替换法得到钢渣的实际用量;随后,采用CT扫描技术研究了钢渣集料多孔特性对沥青的多余吸附量,从而确定了钢渣的吸附机理,并建立了一种钢渣集料的材料组成设计方法。研究结果表明:粒径为10~15 mm的钢渣集料表面孔内沥青体积占钢渣集料表面实际沥青体积的20.21%;粒径为5~10 mm的钢渣集料表面孔内沥青体积占钢渣集料表面实际沥青体积的6.70%。基于体积特性的材料组成设计方法计算的钢渣沥青混合料最佳油石比为5.79%,与马歇尔击实试验结果基本一致。现场检测结果表明,5.70%油石比摊铺的钢渣沥青路面具有优异的抗滑性能和路用价值,对保障路面行车安全具有突出意义。与玄武岩沥青路面相比,钢渣沥青路面的摆值和横向力系数多分布于数值较高的区域,其具有更加优异的抗滑性能。

钢渣-矿渣-脱硫石膏复合胶凝材料的制备及水化机理

加速钢渣水化过程、胶凝活性激发对钢渣综合利用率的提高有重要意义。以矿渣和脱硫石膏为复合激发剂,基于交叉试验的设计方法,对复合胶凝材料的组成进行了优化,分析了复合胶凝材料的综合性能,采用X射线衍射(X-ray diffraction,XRD)、扫描电子显微镜(scanning electronic microscopy,SEM)、傅里叶变换红外光谱(Flourier transform-infrared spectroscopy,FT-IR)等测试方法表征了复合胶凝材料的组成及结构,并以此揭示复合胶凝材料协同优化的机理。复合胶凝材料配合比的交叉试验结果表明:钢渣30%、矿渣60%、脱硫石膏10%,水灰比为0.5,28 d抗压强度为40.4 MPa,其他各项性能指标满足GB/T1346—2011要求。通过多项测试手段可以判断出,矿渣在脱硫石膏的激发作用下不断水解,缩短了水化诱导前期和延长了诱导期,提升早期水化反应程度,释放大量热量,生成了generates ettringite(AFt)和C—S—H凝胶。而浆体的pH值上升,促进钢渣水化反应,加速了浆体由液相反应转为固相反应,证明了各原料之间存在协同反应。

典型锂渣性质及在建筑材料利用的研究现状

这是一篇陶瓷及复合材料领域的论文。锂渣是锂辉石和锂云母提锂及其化合物过程中产生的废渣,其SiO_(2)和Al_(2)O_(3)含量达70%。因残留的化学物质,锂渣堆放和填埋威胁着周边环境,也造成铝硅酸盐矿物资源的浪费。锂渣经过高温焙烧、机械磨碎和化学浸出,具有高比表面能和一定火山灰活性,可以用作建筑材料。本文综述了近年来国内外针对锂渣应用于建筑材料的最新研究成果,重点包括以下几个方面:(1)代替部分水泥做混凝土掺料,对混凝土的力学性能、抗碳化性能、耐磨性、抗氯离子渗透和抗裂性能的影响;(2)锂渣代替粘土生产水泥,对水泥熟料龄期抗折和抗压强度的影响;(3)制备建筑陶粒及力学性能和结构的影响;(4)锂渣配方对陶瓷工艺性能和质量的影响。最后对锂渣在建筑材料的应用研究进行了归纳总结并对研究前景进行了展望,以期能够为开发锂渣在建筑材料掺入量高、经济效益好的应用途径提供借鉴与参考。

硅钙渣-水泥复合胶凝材料水化程度时变规律预测与分析

硅钙渣是高铝粉煤灰提取Al2O3时产生的固体废弃物,将其掺入水泥中,研究复合胶凝材料水化程度时变规律对其资源化利用具有重要意义。基于ARIMA模型建立了硅钙渣掺量为0、10%、20%、30%、40%的硅钙渣-水泥复合胶凝材料水化程度时变规律预测模型,各掺量下模型预测误差均小于5%,说明ARIMA模型在预测水化程度方面具有较好的精度和通用性。预测结果显示:复合胶凝材料的水化程度随龄期的增加而提高,硅钙渣对复合胶凝材料的最终水化程度影响不大;相同龄期下复合胶凝材料的水化程度随着硅钙渣掺量的增加而降低;水化反应主要发生在前期,硅钙渣可以减缓复合胶凝材料的前期水化反应速率,提高后期水化反应速率;水化终止时间随硅钙渣掺量的增加而延长。

高碱原材料制备硅酸盐水泥熟料的研究

采用工业原材料石灰石、高碱页岩、铁矿石按照常规三率值KH=0.92±0.02、SM=2.5±0.1、IM=1.4±0.1进行配料,并引入适量的磷渣制备硅酸盐水泥熟料,通过化学分析、XRD、岩相等检测手段对高碱硅酸盐水泥熟料的化学组成、矿物组成、矿物形貌及物理性能等进行了分析。分析表明,引入适量的磷渣,可改善高碱熟料的液相黏度,促进A矿的发育,改变B矿的晶型,使熟料的标准稠度用水量、凝结时间等物理性能发挥良好,3 d抗压强度可达到39.5 MPa,28 d抗压强度达到59.5 MPa。