相对分子质量对脂肪族高效减水剂分散增强性能的影响

采用超滤法将脂肪族高效减水剂(SAF)切割为相对分子质量(以下简称分子量)范围依次为2 500、2 500~10 000、10 000~50 000和50 000的4个级分,测试结果表明,随级分分子量的增大,重均分子量、特性黏度依次增加,磺化度依次降低。对不同级分减水剂的应用性能研究表明,级分分子量增大,对水泥的减水分散性能显著提高,但对流动度的保持能力降低,同时磺酸根与羟基对Ca2+的络合作用逐渐减弱,使缓凝作用减小。与空白砂浆比较,掺4种级分的7 d和28 d硬化砂浆抗压强度均增大,增幅在30%~60%,并随分子量的增大而增加;掺量(减水剂相对水泥的质量分数)大于0.3%时,由于分子量较大的两个级分对掺量及用水量较敏感,使砂浆泌水严重,抗压强度比低掺量时略低。     

不同品质粉煤灰在砂浆中减水效应及强度规律的研究

选取甘肃地区4种不同品质的粉煤灰,研究各粉煤灰的减水率和同流动度条件下砂浆的强度.结果表明:粉煤灰的品质对砂浆的减水效果和强度有较大的影响,品质较优的FA1、FA2减水效应、各龄期砂浆强度均高于品质较劣的FK3、FA4.粉煤灰水泥砂浆抗压强度与粉煤灰减水率两者之间具有负线性相关.粉煤灰减水效果越好,其与强度的线性关联度...     

新型含苯环聚羧酸系减水剂的制备与性能

用烯丙基聚氧乙烯醚(APE)、丙烯酸(AA)、甲基丙烯磺酸钠(SMAS)和阿魏酸(FA)作为反应单体,在过硫酸铵(APS)引发下通过水溶液自由基共聚反应制备了一种新型含苯环聚羧酸系减水剂(FPC)。当n(APE)∶n(AA)∶n(SMAS)∶n(FA)=1∶5∶0.3∶0.15时,在反应温度为85℃、反应时间为4 h、引发剂APS用量为总单体质量的3%时得到的FPC性能最佳。FPC的主要特点是对含泥水泥具有较强的适应性。实验结果表明,FPC的折固掺量为0.2%时,含泥质量分数10%的水泥净浆流动度可达308 mm,初凝时间和终凝时间分别达430 min和502min,减水率可达33.2%;扫描电子显微镜(SEM)和水泥胶砂强度检测结果表明,FPC可使水泥石更加紧密均质,可以明显提高硬化水泥砂浆的抗压强度。     

不同分子量MPEG合成聚羧酸系减水剂的研究

使用不同分子量甲氧基聚乙二醇（MPEG）分别和甲基丙烯酸进行酯化反应合成大分子单体,然后与其他小分子单体进行自由基聚合,合成聚羧酸系减水剂。研制的聚羧酸系减水剂具有减水率高、混凝土坍落度损失小、水泥适应性广、增强效果好等特点。     

酶解木质素催化磺化衍生物作为水泥减水剂的研究

用固体酸催化剂催化酶解木质素的磺化反应,得到磺化产物SEHL,再用固体碱催化SEHL进一步进行磺甲基化反应,得到产物SH-SEHL。研究了酶解木质素磺化衍生物作为水泥减水剂在水泥净浆中的性能和减水作用机理,并探索了固体催化剂的重复使用性能。结果表明:水灰比为0.35时,掺有0.5%的SEHL和SH-SEHL的基准水泥净浆流动度分别达到205 mm和260 mm,120 min后流动度达到184 mm和223 mm;SEHL和SH-SEHL对各种水泥有良好的适应性;掺有0.25%的SEHL和SH-SEHL的水泥砂浆的减水率分别为17.0%和20.5%,28天的抗压强度比分别为112.4%和122.7%;SEHL和SH-SEHL主要通过提高水泥颗粒间静电斥力达到减水分散效果;固体催化剂二次使用时,SEHL和SH-SEHL的净浆流动度还可达到201 mm和253 mm,表明固体催化剂可以重复使用。     

CFB灰渣抹灰砂浆的组成设计与性能研究

为了提高抹灰砂浆的强度和体积稳定性,研究了水泥用量和灰渣比(循环硫化床(CFB)飞灰和CFB炉渣的质量比)对CFB灰渣抹灰砂浆2 h稠度损失率、抗压强度和体积稳定性的影响,并采用扫描电子显微镜、X射线能谱仪和X射线衍射仪对砂浆的微观形貌、元素分布和物相组成进行测试表征。结果表明,当水泥用量为5%、8%、12%(质量分数)时,CFB灰渣抹灰砂浆分别达到抹灰砂浆M10、M15、M20的强度等级。当胶凝材料用量一定时,随着水泥用量增大,砂浆2 h稠度损失率减小;当水泥用量一定时,随着灰渣比增大,砂浆2 h稠度损失率增大,膨胀效应减弱。CFB灰渣抹灰砂浆中生成的膨胀性钙矾石有效填充了颗粒之间的孔隙,从而提高砂浆的强度和体积稳定性。     

轻骨料对砂浆力学与毛细吸水性能的影响

采用等体积取代法制备了5种不同体积取代率的轻骨料水泥砂浆,借助抗压、抗折试验和称重法,研究了内掺轻骨料对水泥砂浆力学和毛细吸水性能的影响规律,并基于低场核磁共振技术和扫描电镜技术分析了内掺轻骨料砂浆微观结构特征。结果表明:内掺力学强度较低的轻骨料可对水泥砂浆整体力学性能产生影响,随着轻骨料取代率的增加,砂浆抗压、抗折强度相应降低;毛细吸水率随轻骨料取代率、养护龄期的增加而降低。核磁共振试验数据表明:小孔孔隙体积占比随着轻骨料取代率的增多而降低,中孔和大孔孔隙体积占比则与取代率呈正相关;随着龄期的增长,小孔信号弛豫幅值降低。利用扫描电镜对轻骨料砂浆界面过渡区观察,发现轻骨料砂浆界面区结构较致密。同时,由于水化产物堵塞轻骨料表面微孔,形成不透水边界和内部封闭孔,在毛细吸水过程中内掺轻骨料砂浆表现出高孔隙度低渗透性的特征。     

接枝磺化木质素高效减水剂的配伍性能研究

以酸析木质素为原料,通过接枝、磺化和缩合制得接枝磺化酸析木质素GSAL,研究了它与木质素磺酸盐和消泡剂的配伍性能。结果表明:GSAL分别与木质素磺酸盐及其改性产品复配,可得到减水剂GSAL1和GSAL2。当水灰比为0.29、掺量w(GSAL1)=0.6%时,水泥净浆流动度达243mm;掺量w(GSAL2)=0.8%时,水泥净浆初凝时间延长110min,终凝时间延长约7h。掺量w(GSAL1)=0.8%时,水泥净浆减水率为21.4%,砂浆3d和7d的抗压强度比分别为163%和143%,其对水泥的减水增强作用超过了萘系高效减水剂FDN。GSAL与消泡剂的复配产品起泡性降低,水泥净浆流动度、新拌砂浆密度和砂浆抗压强度比均增大,GSAL与磷酸三丁酯配伍后的综合性能最佳。     

聚苯乙烯接枝聚丙烯酸丁酯乳液改性水泥砂浆的性能及微观结构分析

合成了聚苯乙烯(PS)接枝聚丙烯酸丁酯(PBA)乳液(PS-g-PBA),并将其用于改性水泥砂浆,考察了PS-g-PBA乳液含量及PS与PBA的质量比对改性水泥砂浆的减水率、流动度、力学性能以及毛细孔吸水率的影响.结果表明,3种水泥改性剂的减水效果优异,减水率的极大值为56.7％,改性水泥砂浆的毛细孔吸水率下降明显,其...     

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.     

Performance of Softwood Soda-Anthraquinone Lignin–Polyethylene Glycol Derivatives as Water-Reducing Admixture for Concrete

We have developed a high-performance lignin-based water-reducing admixture. In this study, softwood soda-anthraquinone lignin was modified with mono-epoxide polyethylene glycols having chain lengths of 10, 25, and 50 mol (the number of repeating units of ethylene oxide). The mortar flow and concrete slump flow tests were used to investigate the performance of the lignin derivatives as a water-reducing admixture. All tested lignin-PEG derivatives performed considerably better than a commercial lignosulfonate water-reducing admixture in the mortar flow test. In particular, the derivative with a PEG chain length of 50 mol performed excellently in both tests. The optimum PEG content for mortar dispersion was approximately 40% for lignin derivatives with a PEG chain length of 50 mol; this content exhibited a dispersing effect that was four times higher than that of the lignosulfonate water-reducing admixture. The strength of concrete containing the lignin derivatives was almost the same strength as that of concrete containing the commercial lignosulfonate water-reducing admixture.     

Effects of polycarboxylate-type superplasticizer on fluidity and hydration behavior of cement paste

Polycarboxylate (PC)-type superplasticizers were synthesized with different average molecular weight of polyethylene oxide (PEO) graft groups, the molar ratios of graft group to carboxylic group, and then the chemical structure, polymerization condition, and physical and chemical properties were analyzed. In order to evaluate the effects of PC-type superplasticizers in cement paste, the adsorption, the initial plasticity and slump retention characteristics and the degree of hydration reaction were investigated. As the average molecular weight of graft group decreased and molar ratio increased, the conversion rate to copolymers, the adsorption amount of PC-type superplasticizer on cement particles improved; on the other hand, the hydration reaction was delayed.     

矿物掺合料对机制砂砂浆性能的影响

研究了在相同水灰比与流动度情况下,单掺或复掺硅灰及不同地区粉煤灰等矿物掺合料对机制砂砂浆流动性、强度的影响,并与标准砂砂浆进行了比较。结果表明、与标准砂相比,机制砂砂浆需水量大、保水性差、易泌水,但具有增强作用;硅灰引起机制砂砂浆流动性减小、减少泌水、增进强度。水灰比相同时,随掺量灰增大,机制砂砂浆流动性增大,不同龄期下砂浆抗压强度均下降。复掺硅灰与粉煤灰可提高机制砂的强度。上海与贵州两地的粉煤灰品质基本相同,对砂浆性能的影响也基本相同。     

玄武岩纤维及聚丙烯纤维对水泥砂浆性能影响的对比分析

以聚丙烯纤维为对比,研究了不同掺量的玄武岩纤维对水泥砂浆抗压、抗折、抗弯性能的影响,并采用扫描电子显微镜观察纤维在砂浆中的分布状态.结果表明:在最佳掺量下,玄武岩纤维水泥砂浆的各种力学性能优于聚丙烯纤维水泥砂浆并与砂浆具有更好的结合形态,可以取代聚丙烯纤维作为水泥基材料增强体,玄武岩纤维对水泥浆体早期具有显著的增强作用,但降低了水泥砂浆的28d强度;玄武岩纤维对砂浆的抗弯破坏荷载改善不显著,但明显增大了相同荷载下试件的挠度.     

高沸醇木质素环氧树脂改性水泥砂浆的力学性能研究

用高沸醇竹子木质素合成了木质素环氧树脂和木质素环氧树脂亲水衍生物。用红外光谱对产物进行了表征,并研究了不同聚/灰比和养护条件对高沸醇竹子木质素环氧树脂及其亲水衍生物改性水泥砂浆的力学性能的影响。结果表明:随着聚/灰比的增加,试样的抗折强度提高,而抗压强度降低,试样的韧性增强,当聚/灰比大于0.12时,抗折强度明显提高;混合养护条件所得试样的综合性能优于水养护条件。     

Properties of polymer-modified cement mortar using pre-enveloping method

A new method, pre-enveloping sand with polymer, was adopted to make polymer-modified cement mortar (PCM). In the research, two kinds of latex, i.e., styrene acrylate rubber and styrene butadiene rubber, were used. The experimental results of physical and mechanical tests showed that, at the same level of polymer cement ratio, pre-enveloping method was better than normal method regarding the performance of the resulted composite. Moreover, in the condition of relatively low addition of polymer, the improvement of physical and mechanical properties, especially the resistance to cycling of freezing-thawing, by the pre-enveloping method was more significant. Additionally, it was found that styrene butadiene rubber can improve the fluidity of the mortar, and mortar with styrene acrylate rubber can maintain the same fluidity as the control sample by adding small quantities of a superplasticizer. Styrene acrylate rubber had no water-reducing ability by itself.     

Strength and shrinkage properties of mortar containing a nonstandard high-calcium fly ash

A laboratory study was undertaken to assess the compressive and flexural tensile strength and drying shrinkage properties of mortar mixtures containing high-calcium nonstandard Afsin-Elbistan fly ash (FA). Possibility of using Afsin-Elbistan FA in cement-based materials as shrinkage-reducing or compensation agent was also discussed. Five mortar mixtures including control Portland cement (PC) and FA mortar mixtures were prepared. FA replaced the cement on mass basis at the replacement ratios of 10%, 20%, 30% and 40%. Water-cementitious materials ratio was 0.4 for all mixtures. The mixtures were cured at 65% relative humidity and 20±2 °C. The compressive and flexural tensile strength and drying shrinkage values of the mortar mixtures were measured. The results show that Afsin-Elbistan FA reduced drying shrinkage of the mortar by 40%. Therefore, it was concluded that Afsin-Elbistan FA can be used as a shrinkage-reducing agent. The mortar containing 40% FA expanded. This indicates that Afsin-Elbistan FA may be utilized to compensate drying shrinkage of cement-based materials.     

Experimental study on properties of polymer-modified cement mortars with silica fume

This paper discussed the flexural and the compressive strengths of polyacrylic ester (PAE) emulsion and silica fume (SF)-modified mortar. The chloride ion permeability in cement mortar and the interfacial microhardness between aggregates and matrix were measured. The chemical reactions between polymer and cement-hydrated product were investigated by the infrared spectral technology. The results show that the decrease of porosity and increase of density of cement mortars can be achieved by the pozzolanic effect of SF, the water-reducing and -filling effect of polymer. Lower porosity and higher density can give cement mortars such properties as higher flexural and compressive strength, higher microhardness value in interfacial zone and lower effective diffusion coefficient of chloride ion in matrix.     

改性磷石膏球作缓凝剂对水泥性能的影响

研究了工业化生产的改性磷石膏球对水泥标准稠度用水量、凝结时间、胶砂流动度、胶砂强度及水泥与减水剂相容性的影响,并与原状磷石膏和天然石膏进行对比,结合X-射线衍射、综合热分析等微观测试,分析了改性磷石膏球对水泥水化产物相、水化程度的影响.结果表明:采用改性磷石膏球配制的水泥,其初凝、终凝时间与掺配原状磷石膏水泥相比分别缩短217 min、227 min,1d、3d强度显著高于原状磷石膏配制的水泥,28d强度高于天然石膏配制的水泥,且标准稠度用水量、胶砂流动度、与减水剂的相容性等指标优于天然石膏配制的水泥.改性磷石膏球对水泥早期水化无不良延缓作用,且能提高水泥后期水化程度.综合对比上述三种石膏对水泥性能影响的各项指标,认为改性磷石膏球可以完全替代天然石膏作水泥缓凝剂.     

Preparation and characterization of a novel magnesium phosphate cement-based emulsified asphalt mortar

To improve the efficiency of repairing asphalt pavements, a rapid-hardening magnesium-based cement emulsified asphalt (MCEA) mortar was developed. The effect of mix parameters on the properties of MCEA sample was systematically discussed, including asphalt to cement (A/C) ratio, asphalt and cement (S/(A+C)) ratio, water to cement (W/C) ratio, and MgO to phosphate (M/P) ratio, as well as the fresh properties, mechanical behavior and microstructure of MCEA sample were investigated. The results show that the initial setting time of MCEA paste is within 30 min, and the fluidity is 60–180 mm, which can effectively improve the efficiency of pavement repair engineering. Meanwhile, by adjusting the mix proportion parameters, the setting time and fluidity can be adjusted according to engineering needs. The compressive and flexural strengths of plain magnesium phosphate cement mortar reach 46.45 and 7.7 MPa, respectively, and they decrease with the increase of A/C, W/C, and M/P ratios. With the increase of S/(A+C) ratio, the area of emulsified asphalt encapsulated particles decreases, which improves the mechanical properties of MCEA mortar. Increasing the A/C ratio results in an increase in the residual MgO content and a decrease in the struvite content in the MCEA paste. Meanwhile, the residual MgO content in the MCEA paste prepared by the S-type emulsified asphalt is significantly lower than that of the N-type MCEA paste, which is related to the water content of the emulsified asphalt. In addition, the incorporation of emulsified asphalt also increases the porosity of the MCEA sample, but the N-type emulsified asphalt can play a role in refining the pore structure of the sample.