水泥硅灰固化超盐渍土的抗剪强度试验

为了揭示硅灰部分替代水泥对改良盐渍土抗剪强度的影响,采用宁夏平罗县姚伏镇的超盐渍土,分别掺入２％、４％、６％水泥和１０％、２０％、３０％硅灰替代水泥进行超盐渍土改良固化,通过７和２８ｄ龄期的三轴试验,结果表明：对７ｄ龄期固化超盐渍土,当水泥掺量为２％时,硅灰的替代掺量２０％较佳,当水泥掺量为４％时,硅灰的替代掺量在１０％以内较佳,当水泥掺量为６％时,仅参考粘聚力增量,硅灰的替代掺量在２０％以内较佳;对２８ｄ龄期固化超盐渍土,当水泥掺量在２％时,硅灰掺量采用１０％替代水泥为佳,当水泥掺量增加时,需减少硅灰的替代掺量;水泥和硅灰可以降低和抑制固化盐渍土中盐分的
析出,可有效减少盐渍土地基对混凝土基础或者构造物的盐腐蚀病害。     

Reaction degree of silica fume and its effect on compressive strength of cement-silica fume blends

The compressive strength of the cement-silica fume blends with 5mass%, 10mass%, 20mass% and 30mass% of silica fume and water to binder ratio of 0.28, 0.32 and 0.36 from three days to ninety days were investigated. The reaction degree of silica fume was calculated from the Q4 silica tetrahedron, which was used as a probe obtained from 29 Si solid state nuclear magnetic resonance analysis. The fl at of compressive strength after 28 days disappeared for blended cement with inereasing reaction degree of silica fume. The compressive strength of the blended cement pastes approached that of P.I. cement pastes after 56 days and exceeded that after 90 days. The addition of silica fume and the w/b ratio of blends are both critical to the reaction degree of silica fume. The appropriate addition of silica fume, high silica fume reaction degree and low w/b ratio are benefi cial to the compressive strength of the cement-silica fume blends.     

Effect of superplasticizers on the early age hydration of sulfoaluminate cement

The effects of two types of superplasticizers on the properties of CSA cement pastes during early hydration were studied. The influences of two types of superplasticizers on the properties of cement pastes, including the normal consistency, setting time, fl uidity, and compressive strength, were investigated by using various methods. The hydration products of the cement pastes cured for 1 day and 3 days were studied by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results show that the PCE type superplasticizer retards the early age hydration while the FDN type superplasticizer accelerates the early age hydration of the CSA cement. Both types of superplasticizers have no infl uence on the further hydration of CSA cement, confi rmed by the calorimeter tests as well. The ultrasonic pulse velocity measurements were used to probe the influence of two types of superplasticizers on the hydration of CSA cement pastes at a high water-cement ratio（0.45）. The results show that the PCE type superplasticizer retards the early age hydration of the CSA cement while the FDN type superplasticizer has little infl uence on the early age hydration of the CSA cement.     

Influence of fly ash and silica fume on water-resistant property of magnesium oxychloride cement

By incorporation of fly ash or silica fume into magnesium oxychloride (MOC) cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on water-resistant property were investigated by SEM and EDS. It is found that the incorporation of fly ash or silica fume can improve the water-resistance of the MOC. The improvement of the water resistance of the MOC incorporated with fly ash or silica fume may be attributed to the alumino-silicate 5·1·8 gel or silicate 5·1·8 gel.     

冻融环境对聚合物水泥砂浆粘结强度的影响

为了分析冻融环境对外墙外保温系统中聚合物水泥砂浆粘结强度的影响,根据寒冷地区温度变化情况,设计了聚合物水泥砂浆的配合比,在冻融环境条件下进行了不同冻融循环次数时聚合物水泥砂浆的粘结强度试验.探讨了冻融循环和胶粉掺量对聚合物水泥砂浆粘结强度的影响,得到了冻融环境条件下粘结强度的变化规律,分析了冻融环境对聚合物水泥砂浆粘结强度的影响机理.结果表明,随着冻融循环次数的增加,聚合物水泥砂浆的粘结强度逐步降低;随着胶粉含量的增加,聚合物水泥砂浆的粘结强度逐步增大.     

外加剂及其交互作用对水泥胶砂试件抗压强度的影响

通过正交设计,选择了四因子三水平L3427的正交表,进行了27组试验,检测了试件的1d和28d的抗压强度,采用了极差分析、方差分析、影响率分析、试验水平分析和多重比较T法的分析方法,研究了影响水泥胶砂试件强度的显著因素和外加剂之间的交互作用.结果表明,影响1d抗压强度的特别显著因素是水泥用量,显著因素是膨胀剂、增黏剂,外加剂之间的交互影响可以忽略.影响水泥胶砂28d抗压强度的特别显著影响因素是水泥用量、速凝剂以及增粘剂,显著的是膨胀剂和速凝剂的交互作用.     

聚合物改性砂浆强度的回弹法检测试验研究

采用L9(34)正交试验研究了胶粉掺量、水胶比、灰砂比以及硅粉掺量对聚合物改性砂浆表面硬度和抗压强度的影响,通过对散点图的拟合分析确定了聚合物改性砂浆抗压强度与回弹推定值的相关关系.结果表明,各因素对抗压强度和回弹推定值的影响主次顺序一致,影响因素顺序由大到小为胶粉掺量、水胶比、硅粉掺量、灰砂比;抗压强度随胶粉掺量、水胶比的增大而减小,随硅粉掺量和灰砂比的增加而增大;聚合物改性砂浆抗压强度与回弹推定值之间存在线性正相关关系,且在显著性水平α=0.01下其相关关系显著.     

硅灰改性高韧性水泥基材料性能试验研究

工程水泥复合材料（ECC）具有良好的韧性和裂缝控制能力,可用于解决地下和水工工程中的混凝土开裂和渗漏水问题。高水灰比ECC(w/c=1.03)流动度好,但抗渗性能差,且水灰比过高使得材料坍落度大、黏聚性差,不满足可喷射性的指标要求。为了解决上述问题,将硅灰（SF）以不同的SF/水泥质量比引入高水灰比ECC中,以改善其工作性能、抗渗性能、微观结构和力学性能。结果表明,当SF/水泥比为15％时,高水灰比ECC的工作性能大大提高,达到新拌材料可泵送及可喷射的指标要求,高水灰比ECC的抗渗性能提高至P8以上;扫描电镜(SEM)和能量分散光谱仪（EDS）的观察结果证实,添加SF使ECC的显微组织更致密,而且还可以减少碱性物质的产生,从而抑制碱集料反应,提高耐久性。对ECC展开韧性、抗渗性及工作性能(可泵送及可喷涂)研究,获得了高韧性、高抗渗、可喷可泵的ECC配合比,为其在实际工程中的推广及应用奠定了基础。     

Analysis of the Damping Behavior and Microstructure of Cement Matrix with Silane-treated Silica Fume

The surface treatment of silca fume with silane coupling agent prior w incorporation in a cement mortar resulted in composites exhibiting increuses in loss tangent by 5%-200% and storage modulus by 10%-20% , relative to the value obtained by using as-received silica fume. The scanning electron microscopy （SEM） images iindicate that there is a morphological difference in the cement paste with treated and as-received silica fume, The, X-ray diffraction （XRD）, infrared （IR） spectrum analyses and mercury intrusion porosimetry （ MIP ） have provided evidence to understand the reaction mechanism between treated silica .fume and the hydrate product of cement. This has led to the establishment of an initial microscopic model describing the damping behavior of cement matrix.     

复合外掺料对高性能水泥胶砂性能的影响

以低水胶比高强度水泥胶砂为研究对象,初步探讨了高效减水剂、矿渣、粉煤灰、膨胀剂、高吸水树脂及聚合物纤维等组分构成的复合外掺料对水泥基材料的工作性、早期自收缩和力学性能的影响.通过试验结果的对比,发现同时掺入高效减水剂、矿渣、粉煤灰、膨胀剂和高吸水树脂的水泥胶砂流动性最好,流动度经时损失最慢,早期自收缩最小,同时早期力学性能较好.聚合物纤维的掺入有效地提高了水泥胶砂的韧性和体积稳定性.     

Influence of Superplasticizers on Strength and Shrinkage Cracking of Cement Mortar under Drying Conditions

The effects of polynaphthalene series superplasticizers（PNS） with a low content of sodium sulfate （H-UNF）,with a high content of sodium sulfate（C-UNF） and polycarboxylate type superplasticizer （PC） on strength and shrinkage cracking of cement mortar under drying conditions were investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase the initial cracking time of mortars, and decrease the cracking sensitivity of mortars. As for decreasing the cracking sensitivity of mortars, PC〉H-UNF〉C-UNF. To incorporate superplasticizers is apparently to increase the free shrinkage of mortars when keeping the constant w/b ratio and the content of cement pastes. As for the effect of controlling the volume stability of mortars, PC〉C-UNF〉H-UNF. Maximum crack width of mortars containing PC is lower, but the development rate of maximum crack width of mortars containing H-UNF is faster in comparison with control mortars. The flexural and compressive strengths of mortars at 28-day increase with increasing superplasticizer dosages under drying conditions. PC was superior to PNS in the aspect of increasing strength.     

硫酸铵侵蚀作用下水泥砂浆的抗压强度试验研究

为了研究硫酸铵作用下水泥砂浆受腐蚀劣化的力学性能变化规律,通过室内试验研究,分别探讨了在不同水灰比、不同浓度、不同腐蚀龄期下对水泥砂浆的外观形态、质量变化、应力应变关系和抗压强度的影响.结果表明:硫酸铵对水泥砂浆的侵蚀性比较明显,腐蚀后砂浆抗压强度先有所下降然后上升,再下降;随着腐蚀的进行,水泥砂浆试块表面先开裂、剥落,再失去棱角,最后因膨胀而破坏;而溶液浓度越大,水泥砂浆受腐蚀的程度越深;低水灰比的水泥砂浆抵抗硫酸铵溶液腐蚀的能力越强.     

基于正交试验的水泥砂浆开裂敏感性研究

选取比表面积、SO3含量、碱含量、水灰比及养护温度5种因素,采用正交设计理论,通过水泥砂浆的圆环约束试验,分析讨论各因素对砂浆开裂敏感性影响的显著程度,为水泥的生产如何适应混凝土的质量要求以及如何在配合比设计和施工中提高混凝土的抗裂性提供参考.结果表明:各因素对水泥砂浆开裂敏感性的影响程度为比表面积水灰比养护温度碱含量SO3含量,水灰比、比表面积和养护温度对水泥砂浆开裂有显著影响.水灰比降低、比表面积增大和养护温度提高都会引起水泥砂浆开裂趋势的增大,显著降低水泥砂浆的抗裂性能,应引起足够的重视.     

早强复合型水泥混合材料的研制

部分固体废弃物在单独作混合材时,对水泥的早期强度(3 d)有不利影响,从而有可能影响水泥的使用.为此,选取了粉煤灰、矿粉、石灰石粉、赤泥4种固体废弃物,先将它们以5%,10%,15%的比例单独取代水泥熟料,在此基础上,固定混合材的总比例为15%,将它们混掺,且其中赤泥的比例固定为5%,研究了它们对水泥3,28 d强度的影响.试验结果表明,10%矿粉和5%赤泥以及粉煤灰、矿粉、赤泥各占5%时,组成的混合材,不仅能提高水泥28 d的强度,而且还能提高其3 d的强度.     

煅烧对微硅粉性能的影响

采用同步热分析法、X射线衍射、扫描电镜、比表面积和白度等测试手段对煅烧前后的微硅粉样品进行了分析.实验结果表明:在600℃、4 h煅烧时微硅粉的除碳效果最佳,煅烧后样品中碳的质量分数由1.96%下降到0.65%;样品主要成分二氧化硅晶体结构并未变化,仍旧为非晶态,煅烧后仍出现了碳化硅的特征峰,表明煅烧去除的主要为游离碳;微观形貌分析表明,煅烧后样品微观颗粒粒径在长大,片状物质的含量却明显减少,但是组成颗粒的一次粒子长大并不明显;比表面积测试表明煅烧前后比表面积变化不大,但白度由31.04提高到70.14.     

Effects of GH admixture on the early strength of fly ash concrete and mortar

The enhancement effects of GH admixture on the early strengths of fly ash concrete and mortar were studied, and the mechanism was analyzed by X-ray diffraction （XRD） and scanning electro microscope （SEM）. Experimental results show that, by the incorporation of GH admixture, both of cement hydration and pozzolanic reaction of fly ash are accelerated, the strengths of fly ash concrete and mortar are enhanced noticeably, especially the early strength. With a mixture design of 200 kg/m^3 OPC （Ordinary Portland Cement ）, 200 kg/m^3 fly ash and 50 kg/m^3 GH admixture, the strength of concrete at 1 d, 3 d and 28 d reaches 25 MPa, 50 MPa and 70 MPa respectively.     

Properties of High Volume Fly Ash Concrete Compensated by Metakaolin or Silica Fume

The compressive strength and dynamic modulus of high volume fly ash concrete with incorporation of either metakaolin or silica fume were investigated. The water to cementitious materials ratio was kept at 0.4 for all mixtures. The use of high volume fly ash in concrete greatly reduces the strength and dynamic modulus during the first 28 days. The decreased properties during the short term of high volume fly ash concrete is effectively compensated by the incorporation of metakaolin or silica fume. The DTA results confirmed that metakaolin or silica fume increase the amount of the hydration products. An empirical relationship between dynamic modulus and compressive strength of concrete has been obtained. This relation provides a nondestructive evaluation for estimating the strength of concrete by use of the dynamic modulus.     

SO4^2-、HCO3-侵蚀作用下水泥砂浆的抗压强度

工程结构中的水泥砂浆在使用过程中经常会受到侵蚀性离子的作用,致使水泥砂浆性能劣化强度降低.为了改善结构的耐久性,通过模拟试验,分别探讨了SO42-、HCO3-;这两种侵蚀性离子在不同浓度、不同龄期下对水泥砂浆的单轴抗压强度和应力应变关系的影响.试验结果表明,SO42-、HCO3-对水泥砂浆的侵蚀性均比较明显,其中一定浓度的SO42-对水泥砂浆的强度具有一定的增强作用.该研究对水泥砂浆在复杂环境中的应用有重要的参考价值.     

利用粉煤灰、拜耳法赤泥制备贝利特硫铝酸盐水泥

以粉煤灰、拜耳法赤泥为原料制备贝利特硫铝酸盐水泥,研究赤泥掺入及掺入量变化对水泥熟料烧结温度、工作性能、力学性能的影响,借助ＸＲＤ分析熟料的矿物组成及各矿物含量。结果表明：利用粉煤灰、拜耳法赤泥能制备出各项性能合格的贝利特硫铝酸盐水泥。赤泥的掺入能降低熟料的烧成温度,一定量赤泥的掺入能促进Ｃ_４Ａ_３Ｓ矿物的形成,提高水泥的抗压强度。当掺入量超过８％ （质量分数） 时,会引起强度的下降。赤泥掺量为４％时,所制水泥的２８ｄ抗压强度达到４８.９ＭＰａ。