聚羧酸减水剂在水泥自流平砂浆中的应用

对聚羧酸减水剂在水泥自流平砂浆中的应用进行了研究,认为聚羧酸减水剂适用于水泥自流平砂浆并且具有较高的性价比,但在水泥自流平砂浆面层配方设计中应注意气泡问题。     

聚丙烯纤维与胶粉复掺对砂浆强度和韧性的影响

采用聚丙烯纤维与聚合物胶粉复掺的方法配制了胶粉改性砂浆,并应用正交试验和多点分布的纤维单因素试验研究了聚丙烯纤维与聚合物胶粉复掺对砂浆强度和韧性的影响。结果表明：随着纤维掺量的增加,砂浆折压比总体上呈增加趋势,长度为10 mm的聚丙烯纤维增韧效应最优;当聚丙烯纤维复合胶粉改性砂浆的折压比在0．17～0．21时,韧性显著提高;配制参数纤维掺量为0．2％、纤维长度为10 mm、胶粉掺量为5％、硅粉掺量为5％的胶粉改性砂浆的综合强度和韧性最优,适合作为混凝土剥蚀面层的修复材料。     

尾矿砂对水泥胶砂性能影响的试验

将尾矿砂以不同比例代替天然砂,研究其对水泥胶砂性能的影响。试验结果表明,尾矿砂的掺入能够满足水泥胶砂流动度和强度的要求,与天然砂相比,掺加尾矿砂可以提高水泥胶砂的流动度,并使水泥胶砂3d抗折强度和抗压强度略有降低,但可以提高水泥胶砂28d抗折强度和抗压强度。     

A Rheological Model for Evaluating the Behavior of Shear Thickening of Highly Flowable Mortar

Neither the modified Bingham model nor the Herschel–Bulkley model can be used to characterize and calculate the performance of shear thickening of highly flowable mortar because of their incalculability of the rheological parameters. A new exponential rheological model was established to solve the characterization and calculation of shear thickening of the lubrication layer (highly flowable mortar) during the pumping of concrete in this paper. This new exponential rheological model has three rheological parameters, namely, yield stress, consistency coefficient, and consistency exponent. They can quantitatively describe the yield stress, differential viscosity, and shear thickening degree of highly flowable mortar. The calculating results of the rheological parameters of the newly established model for the mortars with different compositions showed that the consistency exponent of mortar decreased with the increase of its sand-binder ratio or the dosage of fly ash in the binder. This indicates that the shear thickening degree of mortar decreases. The consistency exponent of mortar initially decreases and subsequently increases with the increase in silica fume content or the dosage of the superplasticizer. It illustrates that the degree of the shear thickening of mortar initially decreased and subsequently increased. These varying patterns were confirmed by the rheological experiment of mortars.     

研钵研磨法氨基功能化改性蒙脱土

以钠基蒙脱土为基体、γ-氨丙基三乙氧基硅烷(KH-550)为改性剂,采用研钵研磨法、溶液搅拌法、微波加热法制备了有机改性蒙脱土,通过FT-IR、XRD、TG、SEM、UV-Vis等分析方法,对改性前后的蒙脱土样品进行了研究.结果表明:研钵研磨法能够实现对蒙脱土的氨基化合物的插层改性;相比于溶液搅拌法、微波加热法,研钵研磨法改性效果更好;经研钵研磨法改性后,钠基蒙脱土(001)面层间距由未改性时的1.07nm增加到2.42nm;研钵研磨法制备的有机蒙脱土上有机物负载率最高,700℃下失重率达16%;经研钵研磨法改性的蒙脱土在有机介质中的分散性和稳定性最好.     

防水剂对石灰-偏高岭土修补砂浆性能的影响

以石灰和偏高岭土为主要材料,制备一种适用于岩土类建筑的修补砂浆.用桐油和硬脂酸钙两种防水剂来改善砂浆的耐水性,研究桐油和硬脂酸钙对砂浆强度、反应过程、吸水率和软化系数、干燥收缩的影响,并通过XRD和SEM对砂浆进行物相分析和微观形貌观测.结果表明:桐油和硬脂酸钙可以显著提高石灰-偏高岭土砂浆的耐水性,可使吸水率下降至2.5%以下;桐油和硬脂酸都会阻碍偏高岭土的火山灰反应,在一定程度上降低砂浆的强度,但28d的抗压强度仍在5 MPa以上,达到天然水硬性石灰NHL5的强度等级;桐油和硬脂酸钙会影响石灰-偏高岭土砂浆的微观形态和结构,桐油使产物的颗粒更细小、更致密,硬脂酸钙则会使产物结构比较疏松.综合考虑砂浆强度、耐水性等因素,得出桐油和硬脂酸钙的最佳掺量分别为5%和1.5%.     

纤维增强磷酸钾镁水泥砂浆力学性能研究

研究了PVA纤维、PP纤维、玻璃纤维三种纤维在不同的w_(S/C)下对磷酸钾镁水泥砂浆力学性能的影响.结果表明:三种纤维都能在一定程度上增强磷酸钾镁水泥砂浆的力学性能,对磷酸钾镁水泥砂浆早期力学性能的影响比较大,后期力学性能的影响会有所降低.其中,PVA的增强效果最为明显,PP纤维次之,玻璃纤维增强效果最弱.同时得出,在同种纤维条件下,w_(S/C)不是磷酸钾镁水泥砂浆抗折强度的主要影响因素,但是其抗压强度均随着w_(S/C)的增大而增大.     

腐蚀砂浆锚固体形貌特征及分形维数

在砂浆锚固体腐蚀物理实验过程中所获得扫描电子显微镜(SEM)图像的基础上,通过图像处理技术提取了砂浆锚固体微观形貌特征,利用分形理论对形貌特征进行了定量描述,并建立了分形维数和砂浆锚固体的宏观粘结强度之间的关系,最后进行压汞试验,并与SEM图像处理的结果作对比分析。结果表明:随着腐蚀时间的增加,受力工况和未受力工况下锚固体的孔隙率均成线性增大,孔隙数量逐渐减少,孔隙的分形维数逐渐降低,分形维数和孔隙率成负线性关系;随着分形维数的减小,砂浆锚固体的粘结强度先增大后减小。压汞试验的测试结果与图像处理的结果对比,发现误差在5%~7%范围内。     

Mortar Element Method for Flow Problems in Primitive Variables Form

Parallel implementation of the finite element method for the Helmholtz equation and the Stokes equations is discussed in the environment of a distributed-memory massively parallel computer where data is shared among the processors by communication procedures called message-passing. For implementation of the finite element methods based on domain decomposition, “pre-assembly type” and “restriction type” are introduced for data on nodal points. They simplify the implementation and reduce the amount of message-passing between subdomains. In order to reduce this further, the mortar element method is applied to the primitive variables of the Stokes equations. It maintains natural treatment of stress boundary conditions, which is an advantage of the finite element method. Its implementation can be described concisely by the idea of the two data types.     

THEORETICAL ANALYSIS ON THE NUCLEATION OF MICRO-DAMAGE IN CEMENT MORTAR UNDER COMPRESSIVE LOADING AND SULFATE ATTACK

Effect of uniaxial compression on the nucleation of micro-damage in cement mortar under sulfate attack is investigated.Shape and size of micro-voids in cement mortar is detected using Micro Computed Tomography techniques.The formation of delayed ettringite crystal is analyzed using scanning electron microscope and energy disperse spectrum methods.Deformation of micro-voids and the distribution of stress at the surface of a micro-void are calculated.It is found that the nucleation of micro-cracks is caused by the tensile stress at the voids’ surface,and such damage nucleation will be speeded up by the remote uniaxial compressive load.