吸湿性聚乙烯的研制

本文介绍用腈纶废丝碱性水解产物、聚丙烯酸铵等高吸水性树脂与聚乙烯共混制备吸水性共混物,并研究了高吸水性树脂用量、粒经、OPE用量、偶联剂的种类和用量等对共混物吸水率和力学性能的影响.结果表明,随着高吸水性树脂用量的增加,吸水率显著增大,但同时,力学性能却明显下降,当高吸水性树脂用量为3%左右时,共混物的拉伸强度和断裂伸长率达到最大;高吸水性树脂的粒径越小,共混物的性能越好;使用偶联剂能较好地改善共混物的加工性能和力学性能,但吸水率降低,耐用性提高;由于加入了适量的高吸水性树脂,共混物还具有良好的抗静电性能,其体积电阻率为10~7Ω·m.     

膨胀剂与陶砂对低水灰比砂浆的减缩作用

为了有效减少低水灰比水泥基材料的收缩,研究了掺加硫铝酸钙膨胀剂与采用饱水陶砂作为内养护剂的低水灰比砂浆的收缩。结果表明:单独采用膨胀剂不能有效减少低水灰比砂浆的自收缩与干燥收缩;单独采用较高掺量的饱水陶砂时可以显著减少砂浆自收缩,但会增加干燥收缩,而且会明显降低强度;膨胀剂与陶砂复合可以明显减少砂浆自收缩与干燥收缩,在达到同等减缩效果时,可减小陶砂掺量从而基本消除对强度的不利影响:在饱水陶砂的内养护作用下膨胀剂能充分反应,可有效减少低水灰比水泥基材料的收缩。     

粉煤灰对脱硫石膏基砂浆物理力学性能的影响

研究了粉煤灰掺量变化对脱硫石膏基砂浆的稠度、体积密度、抗压强度、抗折强度、粘结拉伸强度、干燥收缩性能等物理力学性能的影响规律。结果表明,粉煤灰对脱硫石膏基砂浆物理力学性能具有显著影响,能使得脱硫石膏基砂浆稠度明显增大,新拌砂浆体积密度和硬化砂浆体积密度略微增大,抗压强度、抗折强度和粘结拉伸强度均显著提高;粉煤灰也能显著改善脱硫石膏基砂浆的干燥收缩性,降低干燥收缩率;且当粉煤灰掺量为20%~30%时,其对脱硫石膏基砂浆的上述物理力学性能改善效果最佳。     

杨木纤维对砂浆流动度、力学性能和自收缩的影响

本文采用控制变量法设计试验,探究了杨木纤维尺寸、体积分数对砂浆流动度、力学性能(抗压、抗折强度)及自收缩的影响。研究发现：与杨木纤维尺寸相比,杨木纤维体积分数对砂浆流动度的影响更为显著,当杨木纤维体积分数自1.0%增至3.0%时,砂浆流动度降低49.56%;增加杨木纤维尺寸和体积分数均会降低砂浆的抗折强度,而增加杨木纤维的体积分数有利于提高砂浆的抗压强度;杨木纤维体积分数比其尺寸对砂浆的减缩作用更显著,添加3.0%长度为0.30～1.25 mm的杨木纤维使砂浆72 h自收缩降低45.6%。     

不同养护条件下丁苯乳液改性水泥砂浆的物理性能

研究了丁苯乳液在水泥砂浆中的减水和保水作用,以及该乳液在不同养护条件下对砂浆物理性能的影响,发现丁苯乳液在砂浆中有良好的减水和保水作用.当聚灰比达13%时,其在砂浆中的减水率达到50%.固定流动度为(170±5)mm且聚灰比大于7%时,改性砂浆的保水率达99%.固定水灰比,丁苯乳液改性砂浆的体积密度在聚灰比10%左右出现极小值,而孔隙率和平均孔径的变化与之相反.但固定流动度为(170±5)mm时,丁苯乳液对砂浆体积密度和孔隙率及孔径的影响不显著.湿养改性砂浆的孔隙率和平均孔径比混养的低.丁苯乳液显著降低了砂浆的毛细孔吸水率.     

原料组成结构对MAPC砂浆性能的影响

通过测试MAPC砂浆的流动性和强度、观察MAPC硬化体的截面形貌,研究了胶砂比、碱酸比和水胶比对MAPC砂浆物理力学性能的影响.结果如下:MAPC砂浆的胶砂比对其物理力学性能有明显影响.在一定范围内,胶砂比的降低会大幅降低MAPC浆体的流动度;胶砂比取1/2.25时,MAPC砂浆的强度最高.MAPC砂浆的碱酸比对其物理力学性能有一定的影响.在一定范围内,随着m(M)/m(P)值的增大,流动度会轻微降低.m(M)/m(P)值取为2.00时,MAPC砂浆试件的抗压抗折强度最高.水胶比对MAPC砂浆试件的物理力学性能有明显影响.在一定范围内,水胶比的不断增大可以大幅增大MAPC砂浆的流动度,但是超过一定范围后,会出现明显的泌水现象,使其几乎丧失流动度;水胶比对MAPC砂浆硬化体的抗折强度的影响与普通硅酸盐一致,水胶比越大,其强度越低.     

木素磺酸盐代替无水石膏作为水泥熟料的缓凝剂

目前一些工业发达的国家如西德、美国、法国等都在研究用木素磺酸盐来代替水泥熟料通常用的缓凝剂——无水石膏来提高水泥的标号。水灰比是决定砂浆或混凝土强度的重要因素之一。水灰比愈小强度愈高,收缩性愈低并有更好的抗冻和抗腐蚀性能。普通水泥熟料加入了木素磺酸盐后制成的砂浆或混凝土在保持原流动度可减少水灰比。普通水泥(含有石膏)制成砂浆或混凝土水灰比为0.4～0.6。这比例超过了水泥水化的所需要的水量。根据理论计算水泥完整地水化所需的水量约为22～23%。用木素磺酸盐作为缓凝剂的水泥制成的砂浆或混凝土在保持原流动度     

水灰比对大掺量塑料砂浆力学及收缩性能影响研究

减小水泥基材料水灰比,提高胶凝材料含量是提高大掺量塑料砂浆力学性能的重要途径,然而,提高胶凝材料含量对大掺量塑料砂浆收缩性能的影响也不容忽视.使用PP塑料等体积替代20％砂子,研究不同水灰比对大掺量塑料砂浆物理性质、力学和收缩性能的影响.结果表明,减小水灰比可有效地补偿大掺量塑料砂浆力学强度,水灰比越小,则抗折强度和抗压强度均越高,近似呈线性关系.此外,水灰比越小,塑料砂浆微结构越密实,孔隙率较低,吸水率越小,密度越大.然而,水灰比越小,自收缩越大,干缩通常也越大.结合试验结果,优选水灰比为0.3或0.4.     

预湿水泥浆颗粒内养护材料对混凝土早期自收缩及抗压强度的影响

制备不同粒径和水灰比的水泥浆颗粒作为低水灰比混凝土内养护材料.以最佳内养护水灰比原则,设计了使用三种水灰比分别为0.6、0.7和0.8的同粒径水泥浆颗粒等体积取代砂子的混凝土.研究了不同水灰比水泥浆颗粒对混凝土早期自收缩、抗压强度和内部微结构的影响.结果表明:颗粒吸水率与其水灰比正相关、与其粒径负相关;预湿水泥浆颗粒可显著降低混凝土早期的自收缩,颗粒水灰比越大,自收缩降低效果越明显;但是掺入水泥浆颗粒也会降低混凝土的抗压强度,颗粒水灰比越高抗压强度降低越多,应用中应优化选择预湿颗粒的水灰比;水泥浆颗粒作为高性能混凝土内养护材料,可改善微观界面的孔隙结构,提高界面的密实性,减少混凝土早期的收缩和开裂.     

硅酸盐水泥对脱硫石膏基砂浆物理力学性能的影响

研究了硅酸盐水泥掺量变化对脱硫石膏基砂浆的稠度、体积密度、抗压强度、抗折强度、软化系数、黏结拉伸强度、干燥收缩性能等物理力学性能的影响规律.结果表明,硅酸盐水泥能显著提高脱硫石膏基砂浆稠度,增大流动性,使得新拌砂浆体积密度和硬化砂浆体积密度略微增大;显著提高脱硫石膏基砂浆的抗压强度、抗折强度和软化系数,尤其是后期强度;能明显提高黏结拉伸强度,显著降低干燥收缩率,改善干燥收缩性能,甚至使得砂浆早期具有微膨胀特点;硅酸盐水泥在脱硫石膏基中的掺量宜控制在20％以内.     

Mechanical and adhesion properties of polymer-modified cement mortars in relation with their microstructure

In this study, cement mortars were modified with a commercial polymer admixture. The aim of this study is to investigate the influence of the polymer content on the mechanical and adhesion properties of the mortars and to relate these properties with mortars’ microstructure. A series of mortars were produced with various polymer/cement/water/aggregate ratios. The adhesion properties of the mortars to clay bricks were tested with a simplified tensile testing measurement. The microstructure of mortars, as well as interfaces, were evaluated by Scanning Electron Microscopy (SEM). It was found that with high polymer content, large size hardened particles are formed, reducing the compressive strength of the mortars. Polymer addition enhances the adhesion between the mortar and brick. The mortar microstructure at the interface affects the adhesion properties and the mode of failure.     

碳纳米管-水泥基复合材料的力学性能和微观结构

研究了掺碳纳米管水泥砂浆的力学性能和微观结构,并与掺碳纤维水泥砂浆的性能进行了对比。低含量的碳纳米管-水泥复合材料具有良好的抗压强度和抗折强度。用扫描电镜对碳纳米管-水泥复合材料以及碳纤维-改性水泥复合材料的微观结构进行了分析。结果表明：复合材料中碳纳米管表面被水泥水化产物包裹,同时碳纳米管水泥砂浆的结构密实。碳纤维表面光滑,在碳纤维与水泥石之间存在明显裂缝。孔隙率测试结果表明碳纳米管的掺入改善了材料的孔结构。     

VAC/DMC阳离子无皂乳液改性水泥砂浆研究

利用醋酸乙烯酯／甲基丙烯酰氧乙基三甲基氯化铵（VAC／DMC）阳离子型无皂乳液对水泥砂浆进行了改性研究，并与普通VAC均聚物乳液进行了比较。研究表明，！与普通水泥砂浆相比，VAC/DMC节离子型无皂乳液改性砂浆（聚灰比为0．1时）的抗折强度较普通砂浆够提高77％，其改性效果明显好于普通VAC乳液，表明用阳离子无皂乳液改性水泥性能能够取得良好效果。探讨VAC／DMC对水泥砂浆改性的原因。     

内养护对不同细度水泥制备的砂浆性能的影响

研究了饱和轻骨料内养护对不同细度水泥配制的砂浆自收缩、强度、水化程度、显微硬度以及界面过渡区形貌等的影响。结果发现：内养护可显著降低不同细度水泥配制的砂浆的早期自收缩,但减缩效果随着水泥比表面积增大而降低;内养护的砂浆后期自收缩仍持续增加,水泥越粗,自收缩后期增长越大;内养护能够显著促进水泥早期水化,这种促进作用在细水泥中最显著。在相同条件下,轻骨料的引入对砂浆强度的影响作用与水泥细度有关;显微硬度以及界面过渡区微观形貌结果显示,轻骨料内养护能显著改善粗水泥体系微观结构,对细水泥体系微观结构的改善则无显著贡献。     

Effect of epoxy resin on the intrinsic properties of masonry mortars

The paper presents an assessment on the properties of three different types of masonry mortars, namely Portland cement mortar (CM), polymer cement mortar (PCM) and polymer mortar (PM) of various compositions. The effect of binder content (cement and/or epoxy) on CM, PCM or PM has been explored in the study. An assessment was carried out on the basis of mechanical (compressive, tensile and flexural strength), physical (water uptake, chloride ion permeability), morphological (porosity) and thermal (coefficient of thermal expansion) properties of the mortars. A comparative cost analysis of the mortars is also discussed in this article. The results show that the mechanical strength of both PCM and PM improves markedly with the addition of epoxy resin, and the higher rate of incremental strength is found for PM. Consequently, the chloride ion penetration, water uptake, porosity and thermal expansion of the mortars decrease significantly with the resin content, but the rate of drop in chloride ion penetration, water uptake, porosity and thermal expansion is much higher for PM. The test results indicate that the variation of binder content (epoxy/cement) is found to be the key factor determining the mortar properties and cost.     

Use of limestone obtained from waste of the mussel cannery industry for the production of mortars

Various types of cement−SiO₂−CaCO₃ mortar were prepared by replacing quarry limestone aggregate with limestone obtained as a by-product from waste of the mussel cannery industry. The CaCO₃ aggregate consists mainly of elongated prismatic particles less than 4 μm long rather than of the rounded particles of smaller size (2-6 μm) obtained with quarry limestone. The mechanical and structural properties of the mortars were found to be influenced by aggregate morphology. Setting of the different types of mortar after variable curing times was evaluated by scanning electron microscopy (SEM), thermogravimetric analysis (TG) and mercury intrusion porosimetry (MIP) techniques. Mortars with a high content in mussel shell limestone exhibited a more packed microstructure, which facilitates setting of cement and results in improved mortar strength. The enhanced mechanical properties of the new mortars allow the cement content in the final mortar composition to be decreased and production costs to be reduced as a result.     

醋酸乙烯阴离子型无皂乳液改性水泥砂浆性能的研究

将醋酸乙烯(vinylacetic acid,VAC)与丙烯酸钠(sodium acrylate,NaAA)共聚得到的阴离子型P(VAC-NaAA)无皂乳液用于水泥砂浆改性。流动性实验结果表明：阴离子型P(VAC-NaAA)无皂乳液对水泥砂浆的流动性没有改善,甚至稍有降低。X射线衍射的结果显示：P(VAC-NaAA)无皂乳液对水泥水化的影响远远小于普通聚醋酸乙烯乳液。P(VAC-NaAA)无皂乳液提高水泥砂浆抗折强度的作用非常明显,在聚灰比m(P)／m(c)为0．1时,干养护条件下,改性砂浆的抗折强度较同样养护条件下的未改性砂浆提高74％,较水养护条件下的未改性砂浆提高53％。由于无皂乳液的稳定性不受水泥砂浆中离子强度的影响,无皂乳液改性砂浆的断面上可以观察到均匀的聚合物膜。     

Physico-mechanical properties of mortars based on the addition of dune sand powder and the recycled fines using the mixture design modelling approach

Physico-mechanical properties of mortars based on the addition of dune sand powder (DSP) and the recycled fines (RF) using the mixture design modelling approach were investigated. This experimental program aims to provide solutions and answers on the use of DSP and the recycled concrete waste in the form of fines for manufacture of the mortar having good properties. For this purpose, both additions are added by substitution of cement up to 25%. Through the results obtained, we have noticed the interest of modelling the response studied by a polynomial which is then able to calculate all the responses of the field of study without being obliged to make all the experiments. The obtained results showed that the introduction of DSP and RF in cement (by substitution) leads to a considerable improvement of mechanical strengths. The dosages of the three factors have optimum values (respectively around 66.66% of cement, 33.33% of DSP, 0% of RF in substituted volume of 112.5 kg of cement) for which the compressive strength (Cs) reaches a maximum value. Cs increases when the percentage of additions increases till an optimum (8.33% DSP, 8.33% RF), then decreases for larger percentages. One can observe that after 28 days, highest flexural strengths are that of mortars M7 and M9, with an optimum effect for the mortar M7. In addition, the modelling of the workability shows that the presence of DSP improves the workability of the mortars in the fresh state. Recycled fines have a negative effect on the flow time.     

Effect of the Interfacial Transition Zone on the Conductivity of Portland Cement Mortars

The electrical conductivity of portland cement mortars was determined experimentally as a function of the volume fraction of sand and the degree of hydration. The results were analyzed using theoretical models that represent the mortars as three-phase, interactive composites. The three phases are the matrix paste, the aggregate, and the thin interfacial transition zone between the two. The microstructure and properties of the conductive phases (the transition zone and the matrix paste) were determined by a micrometer-scale microstructural model, and were used in conjunction with random-walk algorithms and differential-effective medium theory to determine the overall mortar conductivities. The presence of the transition zone was not found to significantly affect the global electrical conductivity of the mortar. However, there were significant differences in conductivity between the transition zone and matrix pastes when examined on a local level. These differences were found to vary with hydration and were most significant when the degree of hydration was between 0.5 and 0.8.