Analysis of the Damping Behavior and Microstructure of Cement Matrix with Silane-treated Silica Fume

The surface treatment of silca fume with silane coupling agent prior w incorporation in a cement mortar resulted in composites exhibiting increuses in loss tangent by 5%-200% and storage modulus by 10%-20% , relative to the value obtained by using as-received silica fume. The scanning electron microscopy （SEM） images iindicate that there is a morphological difference in the cement paste with treated and as-received silica fume, The, X-ray diffraction （XRD）, infrared （IR） spectrum analyses and mercury intrusion porosimetry （ MIP ） have provided evidence to understand the reaction mechanism between treated silica .fume and the hydrate product of cement. This has led to the establishment of an initial microscopic model describing the damping behavior of cement matrix.

Test on Sensor Effect of Cement Matrix Piezoelectric Composite

A novel cement matrix smart piezoelectric composite and its application as sensing element are presented.A cement matrix smart piezoelectric composite piece encapsulated in a cement mortar formed a practical sensor, and it was tested on material test system with cyclic loading.According to the theoretical analysis, the function of the cement matrix piezoelectric sensor output voltage was expressed in terms of the magnitude of the input cyclic loading amplitude and frequency.The curve fitting of gain function that is defined as sensor′s gain factor under different frequencies of input loading was carried out. From the results of curve fitting, it is found that the cement matrix smart piezoelectric composite has a simple relationship between input loading and output voltage.Therefore the cement matrix piezoelectric composite sensor is suitable to be applied in structural health monitoring.

Performance of the Cement Matrix Composite Material With Rubber Powder

The effect of the deferent rubber content substituted for fine aggregate on the mortar performance was studied.The effects of the rubber coated with the coating materials on the mortar compressive strength,bending strength and impact work were discussed.The optimum rubber powder content and the suitable coating material were found.Through the electrical probe test-BEI,SEI and calcium ion distribution,and the slight crack and the interface between the rubber and cement matrix are analyzed.The results show that the rubber powder coated with the surface treatment materials A,B and C has the capability of absorbing a large amount of energy under the compressive and flexural load and the slight cracks of R-C were controlled and restrained.

Capacity of bone induction of compound material of decalcified bone matrix combined with rhBMP-2 and impregnated with bone cement

AIM:To analyze bone inductive capacity of the compound material of decalcified bone matrix combined with rhBMP 2 and impregnated with bone cement.METHODS:To assess the experimental study, histological and Masson’s methods were used.RESULTS:The effects of compound material on the induction of bone formation were investigated in NIH mouse models.It was observed that in the with rhBMP 2 group, mesenchymal cells gathered in the implanted material at the 7th day postoperation,chondrogenesis were found at 14 to 21 days after implantation,new bone formation were observed at about 21 to 28 days after surgery and the DBM particles were absorbed by the new generated tissues gradually.CONCLUSIONS:The compound material of DBM combined with rhBMP 2 and impregnated with bone cement could induce the proliferation and migration of mesenchymal tissues that could be differentiated into cartilage and formed new bone finally.The new bone could absorb DBM particles gradually.The compound material had fair capacity of bone induction.

Piezoresistive Prediction of CNTs-Embedded Cement Composites via Machine Learning Approaches

Conductive cementitious composites are innovated materials that have improved electrical conductivity compared to general types of cement,and are expected to be used in a variety of future infrastructures with unique functionalities such as self-heating,electromagnetic shielding,and piezoelectricity.In the present study,machine learning methods that have been recently applied in various fields were proposed for the prediction of piezoelectric characteristics of carbon nanotubes(CNTs)-incorporated cement composites.Data on the resistivity change of CNTs/cement composites according to various water/binder ratios,loading types,and CNT content were considered as training values.These data were applied to numerous machine learning techniques including linear regression,decision tree,support vector machine,deep belief network,Gaussian process regression,genetic algorithm,bagging ensemble,random forest ensemble,boosting ensemble,long short-term memory,and gated recurrent units to estimate the time-independent and-dependent electrical properties of conductive cementitious composites.By comparing and analyzing the computed results of the proposed methods,an optimal algorithm suitable for application to CNTs-embedded cementitious composites was derived.

Early Stage Hydration Mechanism of Cellulose Ether Modified Thin Layer Cement Pastes

The early stage hydration mechanism of cellulose ether modified thin layer cement pastes was studied, using brick as the matrix. Samples of 6 h, 24 h, and 3 d and 7 d hydration time were analyzed to study the hydration law on the surface of high water-absorbing matrix. Hydration products were qualitatively and semi-quantitatively analyzed using XRD, TG-DSC-DTG, FTIR and SEM. The experimental results show that there is no enough water for 2 mm thick cement pastes to hydrate, because of rapid water absorption of matrix. Trace amounts of Ca （OH）2 was detected after three days hydration. With the prolongation of hydration time, the category and concentration of hydration products do not change. Compared with 2 mm thick cement pastes, 6 mm thick cement pastes and 10 mm thick cement pastes have lower dehydration rate and water loss. The humidity field of the cement paste show different changes within the same time. 6 mm thick cement paste and 10 mm thick cement pastes have longer time and more water to hydrate. Ca（OH）2 and ettringite were detected after 6 hours hydration and the concentrations of hydration products increased from 24 hours to 7 days.

Mechanical Properties of Hybrid Cementitous Composites

Pulverised stem fibres of the natural sponge plant, SP, (Acanthus montanus) and stranded coconut fibre, CF, (Cocos nucifera) from the coir tree were used as reinforcements for thin cement sheets in this research work. The mixture of cement and pulverised waste paper, which formed the matrix, was maintained constant while the fibre mass concentration of both fibres were varied. The slurry formed by adding water to the mixture of the matrix materials and the reinforcement fibres, was poured into rectangular mould and consequently pressed to eject excess water. De-moulded samples were allowed to cure in the laboratory for twenty-eight days before flexural and compressive tests were carried out. The analysis of the experimental results established that sample coded as S4, with 30% CF and 70% SP, showed the most promising result. This implied that particulate reinforcement in cement matrix composite contributed to higher and improved flexural load bearing capacity and ductility when utilised in a higher proportion than long fibres.

水下抗分散水泥土正交试验及配比优化方法研究

水流经过桩基时会形成漩涡侵蚀床面,影响桩基及上部结构的稳定性,冲刷治理是工程界关注的热点问题。为促进固化土技术在桩基冲刷修复中的应用,设计开展了抗分散水泥固化土系列正交试验。针对高岭土和淤泥土,选用PAM、EVA、黄原胶、HPMC四种抗分散剂,采用平均效果分析和极差分析,研究了抗分散剂种类、抗分散剂掺量、含水量和水泥掺量对流动度、浊度、7 d和28 d无侧限抗压强度的影响。结果表明:对于高岭土,抗分散剂掺量从0.25‰增大到1‰,水泥土流动度减小20%,浊度减小25%,抗分散剂掺量对流动性和抗分散性的影响显著。对于淤泥土,对抗分散性影响显著的仍是抗分散剂掺量,而对流动性的影响显著的则是含水量,含水量从1.4倍液限增大到2.0倍液限,水泥土流动度增大45%。基于综合平衡法、矩阵分析法和多元线性回归模型,提出了一种抗分散水泥土配比设计方法,研究得到了高岭土和淤泥土抗分散水泥固化土的推荐配比,其在泥沙起动实验中的抗冲刷特性明显优于原始土样。

高温处理对聚乙烯纤维-钢纤维高韧性水泥基复合材料抗折性能的影响

为了探究高韧性水泥基复合材料经高温处理后的力学性能,采用聚乙烯纤维与钢纤维混杂方式制备一种混杂纤维高韧性水泥基复合材料,通过三点抗折试验探讨所制得聚乙烯纤维-钢纤维高韧性水泥基复合材料经温度20、60、100、150、200、250℃处理后的抗折性能。结果表明:随着处理温度的升高,该复合材料的开裂应力、峰值应力和弯曲韧性均表现为先增大后减小的变化规律,处理温度为60、150℃时最大开裂应力为12.09 MPa,最大峰值应力为18.52 MPa;峰值应力受处理温度的影响较显著,当处理温度为200、250℃时,聚乙烯纤维熔化,复合材料的峰值应力相较于处理温度为150℃时的分别减小42.7%、57.9%;该复合材料的弯曲韧性在指定挠度为L/150、L/100(其中L为支座间跨度)阶段受处理温度影响较小,在指定挠度为L/50、L/25阶段,随着处理温度的升高而先增大后减小,聚乙烯纤维熔化导致复合材料在大挠度阶段的弯曲韧性明显减小。

用于基层的氯氧镁水泥稳定碎石胶凝材料组成分析

为确定氯氧镁水泥稳定碎石应用在路面基层结构中合理的胶凝材料组成,解决击实试验中变量不恒定的问题,采用相理论推导和正交设计试验,利用矩阵分析法,对影响氯氧镁水泥稳定碎石力学性能的因素进行了分析和验证。结果表明,相理论配比结合正交试验所得的配比最优组合与击实试验所得的配比结果一致,确定了氯氧镁水泥稳定碎石胶凝材料的最佳配比范围为轻烧粉掺量3.5%~4%,MgO/MgCl_(2)摩尔比6~7,MgCl_(2)浓度20%~22%。氯氧镁水泥稳定碎石混合料可以通过相理论配比来进行材料组成正交设计,解决了通过击实试验无法解决的MgCl_(2)浓度的问题,为氯氧镁水泥稳定粒料基层的后续研究奠定了理论基础。

水泥基纤维复合材料与混凝土的黏结性能试验研究

为了实现对老旧混凝土结构快速修补的目的,以磷酸镁水泥代替普通硅酸盐水泥,制备了一种高性能水泥基纤维复合修补材料,并以黏结抗拉强度、抗折强度和抗剪强度为评价指标,考察了其与混凝土结构之间的黏结性能。试验结果表明:混凝土的界面粗糙度越大,水泥基纤维复合材料与混凝土之间的黏结抗拉强度、抗折强度和抗剪强度值均先增大后减小,当界面粗糙度为3.5 mm左右时,黏结性能可达到最佳;混凝土基体强度越大,水泥基纤维复合材料与混凝土之间的黏结抗拉强度、抗折强度和抗剪强度值就越大,黏结性能越好。试验制备的水泥基纤维复合材料与混凝土之间的黏结性能较好,能够满足老旧混凝土结构修补施工的需求。

TiO_(2)光催化高延性水泥基材料拉伸性能和光催化性能研究

随着大气污染给建筑物及居住环境带来的恶劣影响日益严重,TiO_(2)光催化水泥基材料广受关注。利用光催化剂纳米TiO_(2)颗粒制备光催化高延性水泥基材料(PC-ECC),研究其单轴拉伸应力作用下力学性能和光催化性能;结合微观力学模型及孔结构分析纳米TiO_(2)颗粒对PC-ECC延性的作用机理。结果表明:掺0~15%纳米TiO_(2)颗粒的PC-ECC在龄期28 d时均具有显著的应变硬化特征和优异的多缝开裂能力,拉伸应变在掺1%纳米TiO_(2)颗粒时出现最低值3.48%,之后升至4.55%;宏观拉伸应变随纳米TiO_(2)颗粒掺量变化趋势与应变硬化指标J_(b)’/J_(tip)一致,且后者与孔结构等微观结构紧密相关;掺5%纳米TiO_(2)颗粒的PC-ECC经72 h紫外光照后光降解亚甲基蓝效率达95%,符合一级反应动力学模型。

纤维复合材料剪滞理论的改进与参数分析

对于纤维复合材料,传统剪滞理论没有考虑基体轴向应变的影响,导致无法反映基体在应力传递中的作用。通过对剪滞理论的改进,解决了上述问题,推导了纤维轴向应力、纤维轴向变形、基体轴向应力、基体轴向变形、纤维/基体界面剪应力、纤维/基体相对滑移量的分布公式,分析了界面弹性模量对应力传递机制的影响,结果符合现有研究成果。经与有限元分析结果对比,验证了改进理论的合理性。

聚丙烯纤维水泥基复合材料物理力学性能研究(Ⅱ)——力学性能

研究了采用不同工艺制作的 3种几何形态的聚丙烯纤维在不同掺量情况下对水泥基材料力学性能的影响 ,结果表明 :(1 )当掺量 φf≤ 1 .0 %时 ,拉丝PP纤维和膜裂ⅠPP纤维虽然不能提高混凝土的强度 ,但却能大幅度提高混凝土的抗弯韧性 ;(2 )低掺量 (φf=0 .0 5 % )时 ,膜裂ⅡPP纤维对混凝土的力学性能无不良影响 ,并可使砂浆抗冲强度、混凝土抗弯韧性指数明显提高 .另外 。

碳纤维增强水泥基复合材料的发展与研究

传统的水泥混凝土材料由于功能单一、脆性大、自重大、抗拉强度和抗弯强度差,在一些特殊领域中的应用受到了很大限制。碳纤维由于具有高比强度、高比模量、密度小、耐腐蚀、导电性好、对人畜无害等优异性能而颇受材料科学工作者的青昧,被视为许多复合材料的优良增强体。将碳纤维加入到水泥基体中,制成碳纤维增强水泥基复合材料,不仅可改善水泥自身力学性能的缺陷,使其具有高强度、高模量、高韧性,更重要的是能把普通的水泥建筑材料变成对温度和应力敏感、具有自感知内部应力和损伤及一系列电磁屏蔽性能的智能材料。

钢渣用作水泥基材料的问题研讨

碱度在1.6以上的钢渣是一种具有一定水化活性,又在不同程度上存在风化膨胀不稳定性的矿物集合体,将其用作水泥基材料的关键是活性的开发与膨胀的抑制。在现有研究的基础上,对钢渣用作水泥基材料时体积膨胀的诱因与抑制措施、钢渣活性的激发等问题进行了较为详细的探讨。认为对钢渣采用机械活化与化学激活并举的措施不失为一条有效的途径。

氧化石墨烯在水泥基体中的分散性及对其结构和性能的影响

为了解决氧化石墨烯(GO)纳米片层在水泥基体中的分散问题,制备了丙烯酸(AA)、丙烯酰氧乙基三甲基氯化铵(AAC)和丙烯磺酸钠(SAS)的共聚物(PAAS),PAAS与GO纳米片层形成PAAS/GO复合物并显示出分散作用。结果表明,w(PAAS)=2%分别与w(GO)=0.01%、0.02%和0.03%形成的复合物可使水泥基体分别形成由花状晶体、多面体状晶体和针状晶体构成的规整有序的微观结构,28 d时的抗折强度分别比对照样提高了63.0%、90.4%和87.9%,抗压强度分别提高了32.6%、74.2%和71.3%,同时这些水化晶体容易生长在裂缝、孔洞等缺陷处,具有修复结构缺陷的效果。PAAS通过与GO纳米片层形成复合物实现了GO在水泥基材料中的均匀分散以及对水泥基材料微观结构和性能的调控。

短碳纤维的分散性对CFRC力学性能的影响

碳纤维增强水泥基复合材料(CFRC)是一种新型建筑智能材料,碳纤维在水泥基体中的分散性直接影响着它的力学性能。借助超声波和甲基纤维素(MC)分散剂,实现了短碳纤维在水泥基体中的均匀分散,对所制备的CFRC复合材料的断口形貌作了SEM观察;测试了试件的抗压强度、抗拉强度和抗折强度。结果发现,碳纤维均匀分散时,复合材料的抗压强度提高19%,抗拉强度比不加碳纤维时提高2.2倍,弹性模量提高1.4倍。此外,复合材料的抗弯强度、抗折强度均高于未均匀分散时的强度。

固井水泥环微裂纹自修复微胶囊的制备与性能研究

采用原位聚合法合成了一种新型油井水泥石微裂纹自修复微胶囊(以环氧树脂为囊芯、脲醛树脂为囊壁)。并使用激光粒度仪、扫描电子显微镜(SEM)、红外光谱仪(FT-IR)和差热-热重分析仪(TG/DTA)等方法分别对微胶囊的粒径分布、表面形貌、化学构成和热稳定性等进行了研究。将微胶囊加入水泥浆体后,通过测试油井水泥石损伤前后的抗压强度值和强度回复率评价了微胶囊的自修复效果。研究结果表明:实验所制备微胶囊的平均粒径约为36.08μm,表面较为粗糙,具有良好的热稳定性。此外,微胶囊的加入在提高水泥石(回复后)抗压强度值的同时,能将水泥石的抗压强度回复率η提高2~3倍,且微胶囊的加量为1.5wt%时,水泥石试样具有最优异的力学性能。

碳纤维增强水泥基复合材料屏蔽性能的研究

现代电子技术的迅速发展不可避免地带来了电磁辐射所造成的环境污染。选择合适的屏蔽材料,利用其反射、吸收、多层反射等功能是消除电磁污染的有效手段。碳纤维除具有高弹性、高模量、低密度、耐腐蚀等优良性能被当作许多复合材料的增强体外,还具有良好的导电性,将其加入到水泥基体中制成碳纤维增强水泥基复合材料(CFRC),不仅使水泥自身力学性能得到改善,而且可作为防止电磁辐射或核辐射的优良屏蔽体。