Effect of Fly Ash and Early Strength Agent on Durability of Concrete Exposed to the Cyclic Sulfate Environment

The effect of fly ash and early strength agent on resistance of concrete to the cyclic sulfate environment was studied.Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%,or 1% early strength agent and fly ash with the replacement of 20%,were made and subjected to 250 cycles of exposure to the cyclic sulfate environment.Concrete properties including loss of mass,chloride ion diffusion coefficient,compressive strength and flexural strength were measured.Microstructure and chemical component of samples were determined by means of X-ray diffraction,scanning electron microscopy and energy dispersive spectroscopy.The experimental results indicated that effect of fly ash on the cyclic sulfate resistance of concretes was mostly dependent on the amount of fly ash.Early strength agent improved performances of concrete with 20% fly ash exposed to cyclic sulfate environment.

A Combined Discrete Event—Agent Based Approach to Modeling Tensile Strength of One-Dimensional Fibrous Materials. Face Validation and Effect of the Basic Model Parameters

A combined method of discrete event and agent based modelling has been applied to the computer modelling and simulation of the tensile strength of one-dimensional fibrous materials (ODFM). This combined method is based on the concept of discrete event simulation as being applied to the modeling of the structure of the fiber flow and on the concept of agent based modelling for modelling and simulation of the fiber interaction within the structure of the fibrous material. Frictional and traction forces arise as the result of this fiber interaction. A model of the ODFM tensile strength, which is based on the slippage effect, is created and studied in this research. Only frictional and traction forces determine the tensile strength in this kind of the model. The article examines the validation problem of the slippage effect based tensile strength model and questions regarding the strength potential estimation through variation in the parameters of the model.

Multi-Variable Flocking Control for Multi-Agent Systems via a Received Signal Strength Indicator

A novel flocking control approach is proposed for multi-agent systems by integrating the variables of velocities, motion directions, and positions of agents. A received signal strength indicator （RSSI） is applied as a variable to estimate the inter-distance between agents. A key parameter that contains the local information of agents is defined, and a multi-variable controller is proposed based on the parameter. For the position control of agents, the RSSI is introduced to substitute the distance as a control variable in the systems. The advantages of RSSI include that the relative distance between every two agents can be adjusted through the communication quality under different environments, and it can shun the shortage of the limit of sensors. Simulation studies demonstrate the effectiveness of the proposed control approach.

SYNTHESIS AND APPLICATION OF THE NOVEL PAM EMULSION AS PAPER DRY-STRENGTHING AGENT

The synthesis of a novel type of polyacrylamide emulsion as dry-strengthing agent was studied in this paper. Several strength agents were obtained by changing reaction conditions such as reaction time, species and doses of initiator, reaction concentration and so on. Meanwhile, the application of these strength agents in papermaking of wheat straw slurry was also discussed. In addition, the obvious increases in dry strength of paper comparable to using currently available cationic dry strength agents at the same dose were given by using these strength agents.

Alkali Tolerance of Concrete Internal Curing Agent Based on Sodium Carboxymethyl Starch

Internal curing agents (ICA) based on super absorbent polymer have poor alkali tolerance and reduce the early strength of concrete.An alkali tolerate internal curing agent (CAA-ICA) was designed and prepared by using sodium carboxymethyl starch (CMS) with high hydrophilicity,acrylic acid (AA) containing anionic carboxylic group and acrylamide (AM) containing non-ionic amide group as the main raw materials.The results show that the ratio of CAA-ICA alkali absorption solution is higher than that existing ICA,which solves the low water absorption ratio of the ICA in alkali environment.The water absorption ratio of CAA-ICA in saturated Ca(OH)_(2) solution is 95.8 g·g^(-1),and the alkali tolerance coefficient is 3.4.The application of CAA-ICA in cement-based materials can increase the internal relative humidity and miniaturize the pore structure.The compressive strength of mortar increases up to 12.95%at 28 d,which provids a solution to overcome the reduction of the early strength.

固化水库底泥制备人工骨料及其性能研究

水库底泥中含有大量无机质,经过处理后,可以用底泥生产建筑材料。采用固化剂固化水库底泥制备人工骨料,通过正交实验研究固化剂的最优掺量(固化剂的掺量以水库底泥的掺量为基准),其结果为:硅酸钠8%、石膏6%、聚羧酸高效减水剂3%、三乙醇胺0.05%(下文简称为SRPT)。然后,掺入最优SRPT作为附加固化剂制备出人工骨料并探究其性能。结果表明:掺入最优SRPT组骨料的筒压强度最大为7.31 MPa,相比于不掺固化剂组提升了44.2%,1 h吸水率为9.34%,堆积密度为937 kg/m^(3)。用SRPT固化剂固化水库底泥制备人工骨料可以高价值利用水库底泥,并且制备的骨料满足规范要求,研究成果为水库底泥在水利工程中的利用提供了新思路。

不同固化剂加固滨海软土的强度特性室内试验研究

为提高固化剂加固滨海软土的强度特性与时效性,通过室内试验研究固化剂类型、固化剂掺量、水灰比、搅拌均匀性、养护条件等因素作用下固化滨海软土强度的演化规律。试验结果表明:不同固化剂加固软土的抗压强度随着养护期龄的延长持续增加,将水泥替换为HR软土固化剂可有效提高软土加固体的抗压强度。拌合时间越长,软土加固体的抗压强度越高;相同的拌合时间,水泥软土加固体的抗压强度远低于HR固化剂加固软土的抗压强度;利用HR软土固化剂加固软土能够在保障施工质量的基础上,有效缩短施工工期。随着水灰比的增加,软土加固体的抗压强度明显降低;相同的水灰比,HR固化剂加固软土的抗压强度均大于水泥软土加固体的抗压强度。软土加固体在养护过程中,温度与湿度在固化剂水化过程中发挥重要作用,影响软土加固体的抗压强度;相同的固化剂掺量,标准养护条件下软土加固体的抗压强度比低温养护提高2倍以上;软土加固体早期抗压强度随着养护期龄的延长增加显著,当期龄达到14 d后,随着期龄的增加软土加固体的抗压强度增长趋势明显变缓。

交联型聚乙烯醇纸张表面施胶剂的制备及其应用

为了改善聚乙烯醇、淀粉作为纸张表面施胶剂的应用性能,选用γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)和硼砂(STB)为交联剂,交联改性淀粉(PS)和聚乙烯醇(PVA1799),制备出不同交联程度的纸张表面施胶剂(CPSn-PVA).通过傅里叶红外光谱(FT-IR),扫描电镜(SEM)及稳定性测试对纸张表面施胶剂的性能进行了表征,探讨了KH560和STB的添加比例对纸张施胶剂的性能以及施胶后纸张物理性能的影响.实验结果表明,当STB添加量为0.1 g、KH560添加量为3 g时,纸张施胶剂膜拉伸强度可达25.6 MPa、断裂伸长率为326%.同时,与原纸相比,多重交联型纸张表面施胶剂表现出良好的应用性能,施胶后的纸张耐折次数、撕裂指数、接触角分别提升了6700%、65.04%、89.7%.

纳米C-A-S-H早强剂的制备及其性能研究

本文采用共沉淀法合成了一种新型纳米水化硅铝酸钙(C-A-S-H)早强剂,通过粒径、SEM和抗压强度测试,研究和分析了不同的铝硅比(Al/Si)对纳米C-A-S-H早强剂颗粒尺寸、微观形貌的影响,以及纳米C-A-S-H早强剂对净浆凝结时间和混凝土抗压强度的影响。结果表明:当Al/Si=0.05时,纳米C-A-S-H早强剂具有更强的晶核效应和分散保持能力;纳米C-A-S-H早强剂可以明显缩短水泥的凝结时间,促进水化进程,提高混凝土的早期抗压强度,且混凝土的后期抗压强度无倒缩。

高耐久补偿收缩混凝土试验研究及工程应用

为满足长沙黄花机场T3航站楼指廊区域对混凝土高耐久补偿收缩的要求,制备了C35高耐久补偿收缩混凝土,并研究了单掺粉煤灰、复掺矿粉和粉煤灰、膨胀剂掺量对该类混凝土力学性能、限制膨胀率和耐久性能的影响。结果表明:高耐久补偿收缩混凝土的最佳配合比为C35-3组;工程实际应用表明,混凝土的28 d抗压强度为47.2 MPa,14 d水中限制膨胀率为2.6×10^(-4),28 d干燥收缩为189με,28 d电通量为284 C,28 d碳化深度为12 mm,抗硫酸盐侵蚀等级达KS90,均满足工程使用要求。

Effect of Combination of Steel Fiber and MgO-type Expansive Agent on Properties of Concrete

The effect of combination of steel fiber and MgO-type expansive agent （MEA） on strength, air-permeability and porosity of concrete was investigated. The porosity and air-permeability of concrete were determined by method of evaporated water and Torrent permeability tester, respectively. Pore structures of mortars in concrete were analyzed using mercury intrusion porosimetry （MIP）. Interfacial structures between steel fibers and matrix were examined by use of optical microscope. The experimental results show that improvement of pore structures of mortar and fiber-matrix interfacial structure in concrete by combination of steel fiber and MEA may remarkably increase properties of concrete. In comparison with plain concrete, compressive strength and splitting tensile strength of steel fiber reinforced expansive concrete increased by 15.3% and 38.1%, permeability coefficient Kt, penetration depth L and porosity of concrete decreased by 41.1%, 21.3% and 13.1% at 28 days, respectively.

Influence ofβ-nucleating Compound Agents on the Mechanical Properties and Crystallization Behavior of Polypropylene Random Copolymer

A novel polypropylene random(PPR)composite materials with optimized properties was developed by addingβ-nucleating compound agents(rare earth complex WBG-2 and aryl amide derivative TMB-5)and ternary compound modifier(TPE/WBG-2/CaCO_(3)).The effects of differentβ-nucleating agents and ternary compound modifier on the mechanical properties and crystallization behavior of PPR were analyzed.The results show that,compared with pure PPR materials,both WBG-2 and TMB-5 could significantly improve the impact strength of PPR.The crystallization temperature of PPR increased with the addition ofβ-nucleating agent.The modified PPR prepared with ternary compound modifier showed the most excellent comprehensive properties.

基于多Agent的微博社交网络信息传播模型

针对传统微博社交网络信息传播模型没有考虑用户个体差异性和用户强弱关系的问题,本文建立了基于多Agent的微博社交网络信息传播模型。将微博用户抽象为Agent,并定义Agent的属性,分析微博社交网络信息的传播机制,定义Agent之间的交互规则,考虑不同强弱关系下影响用户转发信息行为的因素,通过仿真实验探究个体态度、影响力、个体间认同度等因素对微博网络信息传播的影响。仿真结果表明,微博信息的传播呈裂变式扩散模式,微博用户的态度、影响力等因素对信息的传播起促进作用,所提出的相关影响变量对有效利用与管控微博信息传播具有一定的启示意义。

Assessment of strength development in cement-admixed artificial organic soil with GX07

To explore the stabilization effect of stabilizing agent GX07 on treating organic soil and the influence of organic matter on the strength development of stabilized soil,artificial organic soil with various organic matter content was obtained by adding different amounts of fulvic acid into non-organic clay,and then liquid-plastic limit tests were carried out on the artificial organic soil.Meanwhile,unconfined compressive strength(UCS) tests were performed on cement-only soil and composite stabilized soil,respectively.The test results indicate that the plastic limit of soil samples increases linearly,and the liquid limit increases exponentially as the organic matter content increases.The strength of stabilized soil is well correlated with the organic matter content,cement content,stabilizing agent content and curing time.When the organic matter content is 6%,as the cement content varies in the range of 10%-20%,the strength of cement-only soil increases from 88.5 to 280.8 kPa.Once 12.6% GX07 is added into the mix,the strength of stabilized soil is 4.93 times compared with that of cement-only soil.GX07 can obviously improve the strength of cemented-soil and has a good economic applicability.A strength model is proposed to predict strength development.

STUDY ON WET STRENGTH PERFORMANCE OF KENAF MULCH

Optimum applied technical conditions of wet strength agent for kenaf mulch were studied in this article. Breaking length, wet-dry strength ratio, tear index and burst index of kenaf mulch were measured and optimum wet strength agent was selected. The aim is to make mulch have properties of heat preservation, humidity preservation, growth prompting, biodegradation and maximum wet strength and to improve impact resistance of mulch to rainwater so as to assure growth of plant and replace plastic film.

Experiment Study on Self-stress of High-strength, Low-heat and Micro-expansion Concrete-filled Steel Tube

The self-stress trial of the fifteen high-strength, low-heat andmicro-expansion concrete-filled steel tube(CFST)is introduced, andthe generating and distributing features of pre-stress and itsrelation to add- ing quantity of expansive agent, which providespersuasive dependences for optimal design of high-strength, low- heatand micro-expansion CFST were investigated, especially for the designof added quantity of expansive agent.

Analysis of Factors Affecting Solidification Strength of Sludge in a Landfill Area of Shenzhen

Parallel and orthogonal tests are used to explore the influence law of the dosage and age of curing agent on the strength of solidified sludge. The test results show that: 1) The strength of solidified sludge is mainly related to the cement content and dry soil content, and presents a good linear relationship. The influence of gypsum content is not significant. As the age increases, the strength is greatly affected by the cement content. 2) At different ages, the unconfined compression strength of solidified sludge presents a linear relationship, and the change law of later strength can be predicted by early strength. 3) Degree of influence of curing agent dosage: cement dosage > gypsum dosage > dry soil dosage. The optimal mixture ratio is 8% of cement content, 30% of gypsum content (proportion of cement content), and 4 times of dry soil content (multiple of cement content).

轻质高强蒸压加气混凝土的制备及性能研究

本文利用新疆地区粉煤灰和微硅粉等典型固废资源为原料,开展轻质高强蒸压加气混凝土制备技术研究,分析了原料配比、水料比和发气剂掺量对制品绝干密度和抗压强度的影响。结果表明,当m(粉煤灰)∶m(微硅粉)∶m(石英砂)∶m(生石灰)∶m(水泥)∶m(石膏)=30∶25∶10∶25∶8∶2、铝粉量为总物料质量的0.10%、水料比为0.58、蒸压温度为195℃、蒸压压力为1.2 MPa、蒸压时间为8 h时,轻质高强蒸压加气混凝土的绝干密度为568.70 kg/m^(3),抗压强度为5.4 MPa,导热系数为0.140 W/(m·K),达到了A5.0、B06等级。

密实剂对水泥抗氯离子渗透性能的影响

目的研究密实剂对水泥抗氯离子渗透性能的影响。方法选择三种密实剂(S、Y、T),研究不同掺量下密实剂对水泥力学性能和抗氯离子渗透性能的影响,利用压汞测孔法分析内部孔隙结构,并利用扫描电子显微镜观察水泥的微观结构特征。结果当密实剂在单掺条件下,S掺量为0.02%,Y掺量为0.03%,T掺量为0.02%时,水泥3 d和28 d的抗压强度均得到改善,氯离子渗透性能与空白试样相比,28 d电通量分别降低了7.75%、9.44%、10.2%。密实剂的掺入能够使水泥水化更充分,并有效降低孔隙及裂缝的数量,改善水泥石结构的密实性。结论密实剂在低掺量下对水泥强度的发展有促进作用,可以降低水泥石的孔隙率,改善孔结构,并提高水泥抗氯离子渗透性能。