海水和矿物掺合料对硫铝酸盐水泥砂浆性能的影响

本文研究了不同拌和水以及海水拌和时粉煤灰和硅灰掺量对硫铝酸盐水泥(SAC)砂浆力学性能和表观孔隙率以及净浆凝结时间、化学收缩、孔溶液pH值和氯离子结合能力等的影响,并通过XRD、SEM和EDS分析水泥水化产物和微观结构。结果表明,海水能加快SAC早期水化并提高其早期强度,但后期强度和淡水拌和时无明显差别。粉煤灰和硅灰均会延长SAC凝结时间,对早期抗压强度不利,而掺加质量分数为5.0%和7.5%的硅灰能提高SAC砂浆28 d抗压强度。硅灰掺量增加时会提高用水量和表观孔隙率,降低流动性,使水泥化学收缩增大,降低净浆pH值且减少氯离子结合量;粉煤灰能够提高砂浆流动性,减少水泥化学收缩,但掺量越大对SAC砂浆抗压强度和抗折强度越不利,掺质量分数为10%的粉煤灰可小幅提高氯离子结合量且减小表观孔隙率。     

高强机制砂混凝土工作性及力学性能的试验研究

通过偏高岭土和硅灰分别与粉煤灰双掺,使用机制砂混凝土调节剂,在机制砂级配不良,胶材用量仅为500 kg/m3,水胶比高达0.33的情况下配制出C80高强机制砂混凝土,并研究了调节剂、细集料类型、偏高岭土掺量、硅灰掺量对机制砂混凝土工作性及力学性能的影响.试验结果表明,适量调节剂可改善机制砂混凝土的工作性,并提高其抗压强度;机制砂对混凝土的工作性有不利影响,但对其劈裂抗拉强度和抗折强度均有所提高;偏高岭土和硅灰对机制砂混凝土的工作性及力学性能影响显著,随着其掺量的增加,机制砂混凝土的包裹性、和易性提高,而坍落度、扩展度、流动性减小,抗压强度、劈裂抗拉强度和抗折强度呈现先增大后减小的趋势.     

再生砂对砂浆的施工和易性及抗压强度的影响

将湖北襄阳地区的建筑垃圾粉碎筛分得到再生砂,以再生砂部分或全部取代建筑砂浆中的天然砂,用粉煤灰作为掺加料,制作再生砂浆,研究再生砂对砂浆和易性及抗压强度的影响.在砂浆流动性基本相同的情况下,随再生砂掺量增加,砂浆的用水量明显增大、保水性趋于提高.再生砂浆在再生砂取代量为40%时获得良好的骨料级配,强度提高.     

活性掺合料对环氧树脂修补砂浆综合性能的影响

为了探究活性掺合料对环氧树脂修补砂浆的改性效果,为修补工程应用提供依据。研究硅灰和粉煤灰对环氧树脂修补砂浆力学性能、粘结强度、尺寸稳定性和抗冻性的影响,并采用扫描电子显微镜(SEM)和压汞法探究和分析影响机理。结果表明:环氧树脂使砂浆抗压强度降低,掺入硅灰可补偿强度损失,掺粉煤灰砂浆的强度随龄期增加而增加,但其中28 d和56 d强度低于对照组;硅灰和低掺量(≤10%,质量分数)粉煤灰可以提高修补砂浆粘结强度;硅灰对修补砂浆尺寸稳定性有不利影响,粉煤灰则相反;砂浆的抗冻性随着硅灰掺量增加先增加后降低,随着粉煤灰掺量增加而降低。     

结构物混凝土早期抗冻能力影响因素灰色关联分析

采用灰色关联理论对结构物混凝土的早期抗冻能力影响因素进行研究,以抗冻临界强度作为评价指标,水灰比、冻结温度、粉煤灰掺量和硅灰掺量作为影响因素,试验研究发现:对混凝土的早期抗冻能力影响最大的是水灰比,其次是冻结温度和硅灰掺量,最后是粉煤灰掺量;本试验研究的水灰比、冻结温度、粉煤灰掺量和硅灰掺量四个因素与混凝土抗冻临界强度的灰色关联度均大于0.6,说明这四个因素对混凝土的早期抗冻性能均有重要影响.     

冻融环境下水灰比及掺合料对短期混凝土断裂能的影响研究

采用RILEM推荐的楔形劈裂试验方法,分别对经历不同冻融循环下水灰比为0.4和0.5的普通混凝土试块以及水灰比为0.5的单掺粉煤灰和复掺粉煤灰与硅灰的混凝土试块,进行28 d标准养护之后,对其进行楔形劈裂试验,并测量其抗压强度及相对动弹性模量.试验结果表明,在28 d标准养护条件下,水灰比越大混凝土的抗冻性表现越差,断裂能,韧性及抗压强度都明显低于水灰比小的混凝土;掺加粉煤灰的混凝土试块抗冻性低于普通混凝土但是抗裂性能以及韧性都明显强于同等水灰比下的普通混凝土试块,双掺粉煤灰和硅灰的混凝土试块的无论是抗冻性能还是抗裂性能、强度以及韧性都明显高于普通混凝土试块和单掺粉煤灰的试块.     

普通硅酸盐水泥基矿物掺合料对硫铝酸盐水泥性能的影响

本文研究了普通硅酸盐水泥掺量及不同种类和掺量的矿物掺合料对硫铝酸盐水泥性能的影响.结果表明普通硅酸盐水泥掺量小于60％时,普硅水泥-硫铝酸盐水泥体系(OPC-SAC体系)的胶砂强度随着普通硅酸水泥掺量的增加而降低,普通硅酸盐水泥掺量大于60％时,OPC-SAC体系的胶砂强度随着普通硅酸水泥掺量的增加而增大.并且对早期强度的影响较大.在硫铝酸盐水泥体系中掺入矿渣、粉煤灰和硅灰时,其胶砂强度随着掺量的增加而降低,在相同掺量下,矿物掺合料对强度的贡献率为:硅灰＞矿粉＞粉煤灰,对凝结时间的影响强弱为:硅灰＞矿粉＞粉煤灰.     

粉煤灰对人工砂高性能混凝土性能的影响

研究了粉煤灰对人工砂高性能混凝土和易性和抗压强度的影响。试验表明:掺加一定量优质粉煤灰,能显著改善人工砂高性能混凝土拌合物的和易性、降低泌水;水泥用量相同时,大掺灰量人工砂混凝土28d强度较高;胶凝材料用量相同,大掺灰量混凝土用水量少、水胶比低,其强度与水泥用量大、掺灰少的混凝土基本相同。     

粉煤灰掺量对钢纤维砂浆流动性及强度的影响

研究了粉煤灰掺量对钢纤维砂浆的流动性、体积密度及强度的影响。结果表明 :粉煤灰取代水泥 ,能使钢纤维砂浆早期强度降低 ,降低幅度随取代量增加而增大 ;粉煤灰掺量适当时 ,对早期强度影响较小 ,但可提高砂浆的流动性、密实性和后期强度 ,起增强钢纤维的作用     

掺合料对自燃煤矸石砂轻混凝土抗渗和抗冻影响

自燃煤矸石粗骨料在表面质构和强度等方面,与天然碎石存在较大差异,特别是多孔、吸水,使其作为粗骨料配制的混凝土耐久性受到工程界质疑.采用正交试验,研究硅灰、粉煤灰等复掺对自燃煤矸石砂轻混凝土抗氯离子渗透和抗冻性能的影响.结果表明:硅灰掺量对自燃煤矸石砂轻混凝土抗氯离子渗透影响非常显著、对抗冻性能影响不明显,粉煤灰掺量对自燃煤矸石砂轻混凝土抗冻性能影响非常显著、对抗氯离子渗透影响不明显;扫描电镜表征,硅灰、粉煤灰以及矿渣复掺的综合效应,使混凝土结构密实、火山灰反应更加充分,Ca(OH)2含量降低,但冻后出现针状钙矾石.     

粉煤灰/硅灰复合掺合料对水泥净浆性能的影响

研究了水泥标准稠度用水量、粉煤灰掺量、硅灰掺量、粉煤灰与硅灰双掺对水泥净浆性能的影响.结果表明,硅灰使水泥净浆需水量明显增加,粉煤灰、硅灰双掺可克服单掺粉煤灰早期强度低的缺点,短期内能提高水泥净浆的抗压强度.     

The effect of mechanically and chemically activated fly ashes on mortar properties

Fly ash is a waste material from coal-burning power plants that consume pulverized solid fuels. Two fly ashes from Asturias (Spain) were activated mechanically by wet milling and chemically by leaching with sulfuric acid. The activated fly ashes were characterized in terms of physico-chemical characterization, granulometry, density, blaine, BET, XRD and SEM.A comparative study was carried out of several mortars, in some cases using different additions of silica fume or activated fly ash. The influence that these additives have on the mechanical resistance of the mortars was studied. As well as the possible use of these activated fly ashes as a replacement for silica fume in producing high-strength mortar or concrete. It was found that mortars containing activated fly ash presented higher compressive strengths.A mercury intrusion porosimetry study was carried out on cement mortars made with mineral additives such as silica fume and activated fly ashes. In general, the porosities values of these mortars showed that mineral admixtures improved mechanical resistance due to the decrease in pore size.     

分选与磨细粉煤灰对水泥胶砂性能的影响

研究了分选与磨细粉煤灰的颗粒分布与形貌的差异及对水泥胶砂性能的影响。研究结果表明:当勃氏比表面积相近,磨细粉煤灰的中位粒径大于分选细粉煤灰,其圆珠状颗粒较少,表面较为粗糙。在相同水胶比的条件下,掺分选粗粉煤灰的水泥胶砂流动度及强度均低;分选粗粉煤灰磨细后,不仅减少了颗粒的粘连,增加了比表面积,而且提高了粉煤灰的反应活性和水泥胶砂流动度及强度,虽其水泥胶砂流动度仍小于掺分选细粉煤灰的水泥,3d水泥胶砂强度也略低,但其28d水泥胶砂强度略高于掺分选细粉煤灰的水泥;在相同水泥胶砂流动度的条件下,掺磨细粉煤灰配制的水泥胶砂3d强度低于掺分选细粉煤灰的水泥,但随着水化龄期的增长,其差距逐步缩小,至60d时可超过后者。     

Curing requirements of silica fume and fly ash mortars

The curing requirements of silica fume and fly ash mortars were investigated in this study. Silica fume and fly ash mortar specimens were moist cured for periods of 0, 3, 7, 14 and 28 days. After each of the five periods, the moist curing was interrupted by oven-drying the specimens at a temperature of 110°C for 3 days. The specimens were later tested for compressive strength and absorptivity. In this study, it was also determined whether the losses in strength and impermeability of silica fume and fly ash mortars due to an interruption in curing could be regained by recuring. The test results clearly indicate that the curing requirement of silica fume mortar is less than that of plain cement mortar, while in the case of fly ash mortar it is hogher than that of plain cement mortar.     

新型高性能水泥基灌浆料的配制研究

以普通硅酸盐水泥、快硬硫铝酸盐水泥、硅灰和膨胀剂为胶凝材料,再以石英砂为骨料制作灌浆砂浆,通过正交试验设计出高强胶凝材料的最佳配比。最后以上述胶凝材料为基础,粗中细三种砂子为骨料,并添加高性能外加剂,通过改变水和胶凝材料以及胶凝材料和骨料的比例,得到符合标准规范的高性能水泥基灌浆料。掺入快硬水泥有快硬早强的效果;为减小灌浆材料的收缩可以掺入适量膨胀剂;掺入硅灰可以提高灌浆材料的强度。综合考虑灌浆料的流动性,竖向膨胀率以及强度和收缩性的影响,确定灌浆料胶砂比为1.2,水胶比为0.34。研究成果对今后水泥基灌浆材料的发展具有一定的参考价值。     

Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar

In this paper, the influence of fineness of fly ash on water demand and some of the properties of hardened mortar are examined. In addition to the original fly ash (OFA), five different fineness values of fly ash were obtained by sieving and by using an air separator. Two sieves, Nos. 200 and 325, were used to obtain two lots of graded fine fly ash. For the classification using air separator, the OFA was separated into fine, medium and coarse portions. The fly ash dosage of 40% by weight of binder was used throughout the experiment. From the tests, it was found that the compressive strength of mortar depended on the fineness of fly ash. The strength of mortar containing fine fly ash was better than that of OFA mortar at all ages with the very fine fly ash giving the highest strength. The use of all fly ashes resulted in significant improvement in drying shrinkage with the coarse fly ash showing the least improvement owing primarily to the high water to binder ratio (W/B) of the mix. Significant improvement of resistance to sulfate expansion was obtained for all fineness values except for the coarse fly ash where greater expansion was observed. The resistance to sulfuric acid attack was also improved with the incorporation of all fly ashes. In this case the coarse fly ash gave the best performance with the lowest rate of the weight loss owing probably to the better bonding of the coarse fly ash particles to the cement matrix and less hydration products. It is suggested that the fine fly ash is more reactive and its use resulted in a denser cement matrix and better mechanical properties of mortar.     

矿物掺合料对UHPC性能的影响

传统超高性能混凝土(UHPC)的硅灰用量一般都比较高,导致其制作成本较高,而且自收缩比较大,对实际工程应用造成了一定的影响。本文用粉煤灰和矿粉部分或全部替代硅灰制备UHPC,并对其工作性能、力学性能、自收缩及孔结构特征进行了试验研究。结果表明:采用粉煤灰或矿粉替代硅灰可以改善UHPC拌合物的流动性,替代率越高,拌合物的流动度越大;当采用粉煤灰或矿粉替代50%(质量分数)硅灰时,在标准养护下,对28 d抗压强度的影响较小,而在高温蒸养下,则会导致28 d抗压强度下降,当替代率达到100%(质量分数)时,无论是标准养护还是高温蒸养,都会显著降低28 d抗压强度;采用粉煤灰或矿粉替代硅灰能降低细孔的占比,增大孔径,减少自收缩,且粉煤灰对于自收缩的抑制效果优于矿粉。     

不同pH值碱性电解水对砂浆工作性能和强度的影响

碱性电解水具有强碱性、高活性、离子性和吸附性等优点,本文利用不同pH值(9.5、10.5、11.5)的碱性电解水制备粉煤灰砂浆,并在粉煤灰取代率为0%、15%及30%(质量分数)的条件下,系统研究了不同pH值碱性电解水对粉煤灰砂浆的工作性能、力学性能以及Ca(OH)₂等水泥水化产物含量的影响规律,并利用XRD、SEM等微观试验对比分析了不同pH值的粉煤灰净浆的结构组成和微观形貌特征。试验结果表明:随着pH值的提高,相较于普通自来水粉煤灰砂浆,碱性电解水粉煤灰砂浆的流动度、抗压强度和抗折强度逐渐提高,水化产物Ca(OH)₂含量逐渐降低。当碱性电解水pH值为10.5,粉煤灰取代率为15%时,碱性电解水粉煤灰砂浆的早期强度和流动度的改善效果达到最佳,28 d的抗压强度和抗折强度较普通水砂浆分别提高了8.4%和12.5%。同时,相较于普通自来水净浆,不同pH值的碱性电解水净浆的团簇化和颗粒化均表现得更加明显,这对于促进水泥水化进程,提高砂浆流动性,激发粉煤灰早期活性起到了积极作用,除了生成更多的C-S-H凝胶体和Ca(OH)₂等水化产物以外,还生成了钾长石等其他水化产物。