加载速率对CA砂浆抗压强度的影响

CA砂浆中沥青的大量存在使得其力学性能具有较强的时间依赖性.首先研究了CA砂浆抗压强度在不同加载速率下的变化规律及沥青乳液与水泥的相对质量比、砂的细度模数与外掺料硅灰(SF)和橡胶粉(CR)对CA砂浆抗压强度时间依赖性的影响.结果表明:CA砂浆的抗压强度随加载速率的升高呈增加趋势,沥青的相对含量越低,增加趋势越明显;砂的细度模数越小,CA砂浆的抗压强度对加载速率的稳定性越好,但同时会导致CA砂浆的流动性损失过大.SF和CR对CA砂浆表现出的时间依赖性有不同程度的改善作用.同时提出了沥青在CA砂浆中的理想分布模型,对其力学性能的时间依赖性进行了解释.     

CA砂浆强度影响因素及强度机理研究

为制得满足高速铁路建设的CA砂浆,制备了不同配比的CA砂浆,通过考查CA砂浆的强度并利用扫描电子显微镜观测微观结构,研究砂的级配、砂灰比、乳化沥青与水泥比等因素对CA砂浆固化体不同龄期强度的影响．研究表明：选择粒径为0．15—0．3mm与0．3—0．6mm的组合砂能有效地降低高强型CA砂浆材料的分离度,而对CA砂浆28...     

Effect of Waterborne Epoxy on Performances of Cement Asphalt Mortar

The waterborne epoxy modified cement asphalt mortars were prepared with varying content waterborne epoxy and a constant fluidity. The effects of waterborne epoxy emulsion on water/cement ratio,compressive and flexural strength,tensile bond strength,freezing and thawing damage,corrosion resistance of cement asphalt mortar cured for 7 and 28 d have been investigated. The results show that waterborne epoxy is very beneficial to the improvement of mechianical properties and durability of cement asphalt mortar. Waterborne epoxy can improve the flowing ability of cement asphalt mortar. With the increasing of waterborne epoxy content,compressive strength,flexural strength and bond strength all have increased obviously. The modified mortar shows higher resistance to corrosion and the freezing and thawing compared with control mortar.     

减水剂对CRTSⅡ型CA砂浆强度影响规律研究

高速铁路板式无碴轨道中CA砂浆主要由水泥、沥青乳液和多种外加剂组成,其中减水剂是最重要组分之一.为了探讨不同种类和掺量的减水剂对CRTSⅡ型CA砂浆强度和微观结构的影响,采用聚羧酸系、木质系磺酸钠和萘系3种减水剂,研究了其品种和掺量的变化对CA砂浆抗压强度的影响,并通过SEM观察了其微观型貌特征.结果表明,聚羧酸减水剂对CA砂浆抗压强度降低作用的影响最小;相同品种的减水剂掺量越大,CA砂浆抗压强度降低越明显,流动性越高.SEM微观分析表明,强度性能变化的原因是由于减水剂造成了CA砂浆的孔洞数量、孔径、孔洞连通情况不同.     

乳化沥青冷再生混合料中的复合胶浆性质

对乳化沥青冷再生混合料中的三种胶浆系统进行了研究,包括沥青+矿粉、乳化沥青残留物+矿粉和乳化沥青残留物+水泥。结果表明,因为水泥水化作用的存在,水泥⁃乳化沥青残留物胶浆表现出更高的模量增率效果;模量和相位角变化呈现与普通矿粉⁃沥青胶浆和矿粉⁃乳化沥青胶浆不同的特点,且不随粉胶比呈现线性单调的变化;胶浆界面黏结力与矿粉⁃沥青胶浆相当,并在低粉胶比范围内远高于单独利用矿粉的乳化沥青残留物胶浆。     

Damage evolution and dynamic response of cement asphalt mortar layer of slab track under vehicle dynamic load

The damage evolution and dynamic performance of a cement asphalt (CA) mortar layer of slab track subjected to vehicle dynamic load is investigated in this paper. Initially, a statistical damage constitutive model for the CA mortar layer is developed using continuous damage mechanics and probability theory. In this model, the strength of the CA mortar elements is treated as a random variable, which follows the Weibull distribution. The inclusion of strain rate dependence affords considering its influence on the damage development and the transition between viscosity and elasticity. Comparisons with experimental data support the reliability of the model. A three-dimensional finite element (FE) model of a slab track is then created with the commercial software ABAQUS, where the devised model for the CA mortar is implemented as a user-defined material subroutine. Finally, a vertical vehicle model is coupled with the FE model of the slab track, through the wheel-rail contact forces, based on the nonlinear Hertzian contact theory. The evolution of the damage and of the dynamic performance of the CA mortar layer with various initial damage is investigated under the train and track interaction. The analysis indicates that the proposed model is capable of predicting the damage evolution of the CA mortar layer exposed to vehicle dynamic load. The dynamic compressive strain, the strain rate, and the induced damage increase significantly with an increase in the initial damage, whereas the dynamic compressive stress exhibits a sharp decrease with the increasing initial damage. Also, it is found that the strain rate dependence significantly influences the damage evolution and the dynamic behavior of the CA mortar layer.     

CA砂浆的流变特性

CA砂浆是应用在板式轨道结构中的一种新型有机无机复合灌浆材料,其流变性能直接决定CA砂浆的灌注效果.通过流变仪研究了新拌CA浆体的瞬态与稳态流变特性及其影响因素.结果表明,CA浆体属于非牛顿流体,表现在低剪切速率时,CA浆体的粘度随时间先减小后增大;中高剪切速率时,其粘度先随时间减小后趋于稳定.在绝对水灰比固定条件下,随着沥青乳液与水泥质量比、硅灰和流变助剂掺量的增大,CA浆体的粘度增加;随着粉煤灰掺量的增加,CA浆体粘度略有降低.     

塑料砂浆的性能研究

采用废旧PET塑料瓶作胶结料来制备塑料砂浆。研究了不同的PET与砂的比例、养生时间以及少量沥青的添加对塑料砂浆的物理和力学性质的影响。试验结果表明,塑料砂浆具备吸水率低,强度增长迅速的特性。随着塑料砂浆中含砂量的增加,其抗压强度与抗折强度增大。在室温条件下,塑料砂浆养生3h即可达到最终强度的90％以上;养生24h可达到最终强度。在塑料砂浆中加入少量的沥青,能够有效提高塑料砂浆的抗弯拉性能。     

Ultra high early strength self-compacting mortar based on sulfoaluminate cement and silica fume

The influences of silica fume and aluminum sulfate on hydration process of sulfoaluminate cement were carried out by ring flow, setting time, hydration heat, XRD and DTG analyses. In addition, mortar mixtures with different functional additives have been studied through compressive strength, flexural strength, volume stability at early age and porosity characterization tests. The results show that the addition of silica fume and aluminum sulfate reduces the fluidity and shortens the setting time of sulfoaluminate cement paste, promoting hydration process and increasing hydration products at early age. In the case of appropriate proportion of mortar, the inclusion of hydroxy propyl methyl cellulose, dispersible polypropylene fiber and organic silicon kind of defoamer can control segregation and bleeding, improve mechanical strength and volume stability at early age, and modify the pore distribution of sulfoaluminate cement mortar, respectively. The sulfoaluminate cement mortar can carry out gravitational grouting in the absence of outside force, the compressive strength of 2 hours and 24 hours have reached 26 and 58 MPa respectively, and have good microexpansion and tiny pore distribution characterization.     

超细粉煤灰与原灰在水泥砂浆中的水化特征对比研究

主要对比研究了粉煤灰原灰颗粒和超细粉磨后的粉煤灰颗粒在水泥砂浆中的水化过程,利用SEM对水化行为进行了微观观察,并结合砂浆试块3 d7、d、28d抗折、抗压强度.结果表明:粉煤灰的细度对试块的强度影响最大,尤其是后期对抗压强度,在相同掺量下,强度相差达2倍左右;粒径在5μm左右的粉煤灰颗粒在养护初期就已经开始水化,且水化速率较快,在28 d时水化程度已经很充分,粉煤灰原灰颗粒即使养护到28 d龄期时,水化程度仍然很低;掺入细灰的试体各个龄期的结构均比原灰的要致密,且钙矾石的生长更快.     

水泥沥青浆体中减水剂与乳化沥青的竞争吸附行为

为揭示水泥沥青砂浆(CA砂浆)中水泥对乳化沥青和减水剂的吸附规律,采用微量热仪分析了减水剂、乳化沥青(单掺及同掺)对水泥水化诱导期的延迟作用.采用"固含法"研究了减水剂种类对水泥-乳化沥青经时吸附规律的影响,以及减水剂在不同添加顺序时对水泥-乳化沥青经时吸附规律的影响.采用偏光显微镜对减水剂作用下水泥-乳化沥青的吸附行为进行了原位观测.结果表明:CA砂浆中的乳化沥青和减水剂均能显著延迟水泥的水化诱导期,两者同掺使延迟作用产生了明显的协同效应;聚羧酸减水剂与乳化沥青对水泥的吸附作用存在明显的竞争关系,两者同掺时水泥优先吸附减水剂分子,减水剂耗尽后,水泥再吸附乳化沥青.减水剂后掺时可使部分吸附的乳化沥青发生解吸附.     

Synthesis and Application of Sodium-carboxymethylcellulose Type Superplasticizer in Cement Mortars

The polymeric admixture, the sodium-carboxymethylcellulose(CMC)/poly sodium p-styrene sulfonate(PSS)/poly vinyl acetate(PVAc) was synthesized and applied in cement mortars. The polymer was tested by FTIR and SEM, and the results indicate that the ideal molecular structure is synthesized. The effect of addition amount of polymeric admixture and water-to-cement ratio on mechanical properties of cement mortars was studied. The polymer-modified mortars under the optimum water cement ratio and optimum polymer cement ratio, the flexural strength of polymer-modified mortars are 1.45, 1.21, and 1.17 times higher than the plain cement mortar at age of 3, 7, and 28 d, respectively. The compressive strength of polymer-modified mortars at age of 3, 7, and 28 d are 1.55, 1.40, and 1.2941 times higher than that of the plain cement mortar,respectively. Scanning electron microscope(SEM), FTIR and TG were used to analyze the effect of polymer emulsion on cement hydration reaction. The results show that the polymer emulsion can promote the hydration reaction of cement.     

水泥混凝土地坪"起砂露石"的薄层修复砂浆研究

通过对多种配方修补砂浆的抗压强度、抗折强度、抗拉强度、粘结强度、折压比、拉压比、干缩变形性能、弹性模量、耐磨性能的对比研究，发现了施工性能、力学性能、变形性能、耐久性能完全能满足“起砂露石”的混凝土地坪修补要求的砂浆，避免了采用板块拆除重浇、环氧砂浆罩面等修补方式所造成的费工耗时、色差严重、变形不同步或老化而导致粘结失效等问题。     

Comparison of hydration properties between cement-GGBS-fly ash blended binder and cement-GGBS-steel slag blended binder

The hydration properties of cement-GGBS-fly ash blended binder and cement-GGBS-steel slag blended binder were compared. The experimental results show that the hydration rate of cement-GGBS- steel slag blended binder is higher than that of cement-GGBS-fly ash blended binder within 28 days, but lower than the latter after 28 days. The hydration of cement-GGBS-steel slag blended binder tends to produce more Ca（OH）2 than the hydration of cement-GGBS-fly ash blended binder, especially at late ages. Cement-GGBS- steel slag mortar exhibits higher strength than cement-GGBS-fly ash mortar within 28 days, but at late ages, it exhibits similar compressive strength with eement-GGBS-fly ash mortar and even slightly lower bending strength than cement-GGBS-fly ash mortar. Cement-GGBS-steel slag paste has finer early pore structure but coarser late pore structure than cement-GGBS-fly ash paste. Cement-GGBS-steel slag paste can get satisfied late pore structure and cement-GGBS-steel slag mortar can get satisfied late strength as compared with pure cement paste and pure cement mortar, respectively.     

乳化沥青对PVA纤维增强水泥基复合材料韧性的影响

为了研究乳化沥青对纤维增强水泥基复合材料韧性的影响,采用乳化沥青制备PVA纤维增强水泥基复合材料,对其强度和韧性性能进行测试,并采用SEM对试件断面微观形貌进行了分析。结果表明,加入乳化沥青以后,复合材料的抗压强度和抗折强度迅速下降,而韧性性能迅速上升;纤维的破坏模式由拉断破坏变成拔出破坏,随之在试件底部出现了多缝开裂;当乳化沥青用量为10%时,试件出现了明显应变硬化现象;当乳化沥青用量过大时,韧性反而下降。此外,结合微观力学原理,对乳化沥青的增韧机理进行了阐述。     

Strength and Microstructure of Mortar Containing Glass Powder and/or Glass Aggregate

The compressive strength of mortar containing glass powder(GP) and/or glass aggregate(GA) was tested, and its microstructure was also studied by thermogravimetric and differential thermal analysis(TG-DTA), scanning electron microscopy(SEM), energy dispersive spectroscopic analysis(EDX), and X-ray diffraction(XRD) techniques. The incorporation of GA would decrease the compressive strength of the mortar in the absence of GP. Incorporating both GA and GP could change the hydration environment, promote pozzolanic reaction of GP and improve the compressive strength. GP does not lead to but can effectively control ASR(Alkali Silica Reaction). GP and GA do not transform the type of hydrates, but have a great influence on the amounts of hydration products, and generate more calcium silicate hydrate(C-S-H gel) with lower Ca/Si ratio. GP and GA with good gradation will make the microstructure denser.     

Effect of calcium aluminate cement variety on the hydration of portland cement in blended system

Two kinds of CACs with different monocalcium aluminate（CA） contents were used in the PC/CAC（PAC） mixtures. Effects of CA and CACs on the properties of PAC were analyzed by setting times and the compressive strength tests, and also by means of calorimetry, XRD, DTA-TG and ESEM. The experimental results show that the compressive strength of the PAC mortars decreases with increasing content of CAC while it declines sharply with a higher content of CA in CAC. Compared with neat PC paste, the content of calcium hydroxide in hydrates of PAC paste decreases significantly, and the hydration time of PC is prominently prolonged. Additionally, the higher the content of CA in CAC, the more obviously the hydration of PC is delayed, confi rming that the CA phase in CAC plays an important role in the delay of PC hydration.     

干燥环境下乳化沥青改性水泥砂浆的试验研究

研究了干燥环境下乳化沥青对水泥砂浆流动性和力学性能的影响，试验结果表明乳化沥青能提高水泥砂浆的抗压强度、抗折强度，降低脆性。并简迷了乳化沥青对水泥砂浆的改性作用机理。     

Damage action of alkali-resistant glass fiber in cement-based material

The compressive strength and flexural strength with the same strength class cement mortar of the alkali-resistant glass fiber cement mortar were tested in standard and hot-water curing condition, and the damage mechanism of alkali-resistant glass fiber was studied. The interaction mechanisms of the chemical erosion and physical injury in different curing conditions were studied in order to summarize the damage mechanism of alkali-resistant glass fiber in cement-based materials, and chloride diffusivity coefficient and porosity of cement mortar were tested in the different curing conditions. The experimental results are that the strength of cement based materials and fiber cement slurry interface zone were closely related, and heat curing could accelerate the hydration of cement, but inevitably enlarge the defect.     

超缓凝剂对硅酸盐水泥砂浆性能的影响

目的为配制一种新型有机复合超缓凝剂，研究不同掺量及养护条件下其缓凝效果和硬化机理．使之可有效地应用于大体积混凝土及缓黏接预应力混凝土工程中．方法利用XRD和SEM等微观手段，对掺入超缓凝剂水泥砂浆的缓凝性能进行了测试和表征．结果超缓凝剂在不同养护条件下，可使水泥水化“休眠”20～40d，“休眠”结束后能迅速水化而结构不发生变化．XRD图谱表明并未发现异常水化物产生；SEM图像表明，掺超缓凝剂的水泥硬化结构更加致密．结论在标准养护条件下，掺量0．035％的超缓凝剂可使水泥水化“休眠”34d，“休眠”结束后59d可达空白试件28d强度．随养护温度增加和超缓凝剂掺量的降低，水化“休眠”期降低．超缓凝剂并未使水化产物发生本质变化，其耐久性应是可靠的．