萘系减水剂/氧化石墨烯复合材料对水泥石微观结构和性能的影响

采用Hummers法和超声剥离制备了氧化石墨烯(GO)纳米片层分散液,再与萘系减水剂(NS)复合得到NS/GO复合材料.研究了NS/GO复合材料对水泥净浆流动性和水泥石抗压耐折强度的影响.研究结果表明,当NS/GO的掺量为4.8g/0.06g(每100g水泥)时,净浆流动度可以达到204mm,所得水泥石的抗压强度为65.4MPa,且耐折强度达到10.6MPa,分别比对照样品提高了29.3%和41.4%.SEM形貌结果表明,GO能够促使水泥水化反应形成致密的片层状结构.这些结果对于提高混凝土的抗压耐折强度,以及抗裂性和耐久性等具有重要的意义.     

Adsorption mechanism of polycarboxylate-based superplasticizer in CFBC ash-Portland cement paste

Circulating fluidized bed combustion （CFBC） ash exhibits the desirable pozzolanic activity which makes it a potential supplementary cementitious material to replace cement for concrete production. However, the high unburnt carbon content and porous surface structure of CFBC ash may adsorb water reducer and thereby significantly reduce the efficiency of water-reducing agents. The adsorption mechanism of polycarboxylate superplasticizer in CFBC ash-Portland cement paste was investigated by ultraviolet-visible spectrophotometer, and the conception of ＂invalid adsorption site＂ of CFBC ash was presented. The results show that the adsorption behavior of polycarboxylate superplasticizer in coal ash-Portland cement paste can be described by Langmuir isothermal adsorption equation. The adsorption capacity of CFBC ash-Portland cement paste is higher than that of pulverized coal combustion （PCC） fly ash-Portland cement paste. Moreover, the adsorption amount of polycarboxylate superplasticizer increases with the ratio of ash-to-cement in the paste. At last, the fluidity of CFBC ash-Portland cement paste is lower than that of the PCC fly ash paste. This work suggests that when CFBC ash is used as concrete admixture, the poor flowability of the cementitious system due to the high adsorption of water and water-reducing agent should be taken into consideration.     

Effect of polycarboxylate-type superplasticizer on the paste fluidity based on the water film thickness of flocs

The excess water film theory and the properties of flocs are integrated to examine the effect of the polycarboxylate-type superplasticizer on the paste fluidity.The theory states that excess water can surround the flocs rather than the particles and that the cell consists of a floc and a superficial water film.Experiments on limestone powder pastes were conducted to verify the theory.The superplasticizer dosage(sp%)and the water–powder ratio by volume(Vw/Vp)were systematically varied.A sedimentation balance method was used to measure the size distribution of the flocs in the limestone powder pastes.The water film thickness(WFT)of flocs was then calculated and shown to determine the paste fluidity.Based on this WFT of flocs,the effect of the sp on the paste fluidity was determined and then compared with the effect of water.     

水泥沥青浆体中减水剂与乳化沥青的竞争吸附行为

为揭示水泥沥青砂浆(CA砂浆)中水泥对乳化沥青和减水剂的吸附规律,采用微量热仪分析了减水剂、乳化沥青(单掺及同掺)对水泥水化诱导期的延迟作用.采用"固含法"研究了减水剂种类对水泥-乳化沥青经时吸附规律的影响,以及减水剂在不同添加顺序时对水泥-乳化沥青经时吸附规律的影响.采用偏光显微镜对减水剂作用下水泥-乳化沥青的吸附行为进行了原位观测.结果表明:CA砂浆中的乳化沥青和减水剂均能显著延迟水泥的水化诱导期,两者同掺使延迟作用产生了明显的协同效应;聚羧酸减水剂与乳化沥青对水泥的吸附作用存在明显的竞争关系,两者同掺时水泥优先吸附减水剂分子,减水剂耗尽后,水泥再吸附乳化沥青.减水剂后掺时可使部分吸附的乳化沥青发生解吸附.     

Adsorption of superplasticizers in fly ash blended cement pastes and its rheological effects

The adsorption of superplasticizers in fly ash blended cement paste and its rheological effects were investigated.It is shown that the absorption of superplasticizer on portland cement particles is very different from that on fly ash particles.The fly ash particles have smooth surfaces and are negatively charged,so its adsorption capacity is weaker than the portland cement particles.The amount of adsorbed SP in the fly ash blended cement paste depends highly on the replacement proportion of portland cement with fly ash,and to a much less extent on the nature of the fly ash.However,the amount of adsorbed superplasticizer does not correspond well the ζ-potential of the solid particles,due the strong adsorbing capacities of the Portland cement particles.When fly ash replaces portland cement in the paste,the rheological behavior is radically changed,which is closely related to the fineness and density of the ash.The packing and agglomeration of the solid particles are the controlling factors on the rheological parameters of the fresh paste,instead of the amount and type of adsorbed superplasticizer.     

葡萄糖酸钠与高效减水剂复合使用对水泥水化历程的影响

用直接测温法及X射线衍射技术,系统研究了葡萄糖酸钠与萘系、氨基磺酸盐系及聚羧酸盐系3种高效减水剂复合使用对水泥水化热、水化温峰、温峰出现时间及不同水化龄期Ca(OH)2和钙矾石(AFt)生成量等方面的影响.结果表明:与糖钙和三聚磷酸钠相比,葡萄糖酸钠及其与高效减水剂复合对水泥水化历程的影响规律明显不同.单掺葡萄糖酸钠使水泥水化第2放热峰出现时间延迟,但温峰值及水化热与空白样基本持平,温峰时的Ca(OH)2生成量增大.复合使用葡萄糖酸钠与高效减水剂时,与不同品种高效减水剂复合使用对水泥水化历程的影响不同.     

酚醛-乙醇体系在石英纤维表面吸附行为研究

采用漫反射红外光谱研究酚醛树脂-乙醇体系在石英纤维表面的竞争性吸附行为;紫外吸收光谱分析表明酚醛树脂和乙醇之间存在很强的相互作用;粘度和表面自由能测量证实作为溶剂的乙醇被优先吸附.酚醛树脂在纤维表面的吸附是溶质、溶剂和纤维表面3者之间氢键共同作用的结果,乙醇和酚醛树脂在纤维表面形成竞争性吸附,溶质-溶剂间的氢键作用不利于酚醛树脂吸附.热失重分析表明作为溶剂的乙醇被优先吸附导致树脂在一维复合材料液体成型工艺模型内部不同位置分布不均.     

萘在松花江沉积物上的吸附解吸行为

为了探索萘在松花江沉积物上的吸附-解吸特性,采用实验室模拟方法进行研究.结果表明:萘在沉积物上的吸附在8 h内可以充分达到平衡,吸附过程表现出一定的非线性,与Linear和Langmuir方程相比,Freundlich方程能够较好地拟合萘的吸附和解吸过程,拟合度分别为0.93和0.962.萘的解吸行为存在较为明显的滞后现象,随水体中平衡浓度升高,萘的迟滞系数降低.     

壳聚糖聚多巴胺改性水凝胶对双氯芬酸钠的吸附实验研究

双氯芬酸钠是水体中广泛分布的新型污染物之一,关于其去除的研究备受关注。为提高水体中双氯芬酸钠的去除效率,获得经济高效、对环境友好的吸附剂,以壳聚糖为原料,通过光催化法在壳聚糖上引入聚多巴胺进行改性,制备新型壳聚糖-聚多巴胺改性水凝胶(CS-PDA),研究该材料对双氯芬酸钠的吸附性能。通过SEM、FTIR、XPS和BET测试对CS-PDA进行表征,材料呈网状结构,疏松多孔,比表面积达22.46 m²/g;探究时间、温度、初始浓度、pH值对吸附效果的影响。结果表明:pH值为4.3时CS-PDA对双氯芬酸钠的吸附容量最大;吸附动力学符合拟二级动力学模型,在240 min时达到吸附饱和;吸附等温线符合Langmuir等温线模型,在25℃时双氯芬酸钠的Langmuir理论最大吸附容量为333.2 mg/g。CS-PDA对双氯芬酸钠的吸附容量经历7个再生循环后仍大于70 mg/g。     

无机盐对硫酸盐与聚羧酸减水剂相互作用的影响

目的 探讨硫酸盐对聚羧酸减水剂分散效果的影响机理,改善硫酸盐对聚羧酸减水剂吸附性能的影响.方法 在粉煤灰中掺入硫酸钠以改变其体系中硫酸盐的含量,然后在硫酸盐-聚羧酸体系中加入无机盐,采用总有机碳质量浓度(TOC)、ζ电位以及红外光谱等试验.结果 当粉煤灰中硫酸钠质量分数为3％时,加入3％的硝酸钡以后,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到914 mg/L,ζ电位的绝对值由11.11 mV提高到14.6 mV;加入3％的氯化钙,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到1 141 mg/L,ζ电位的绝对值由11.11 mV提高到15.91 mV;同时当粉煤灰中硫酸钠质量分数为3％时,红外谱中透射率明显下降,但向体系中加入无机盐(3％硝酸钡或3％氯化钙)以后,红外谱中百分比透射率有很大提高.结论 硫酸钠与聚羧酸减水剂本身存在相互作用,粉煤灰中硫酸钠的含量越多对聚羧酸减水剂的吸附量增大,在硫酸盐-聚羧酸体系中加入无机盐,可以减弱硫酸盐对聚羧酸减水剂分散效果的影响.     

Effect of aggressive pH media on peat treated by cement and sodium silicate grout

The effects of aggressive peat nature (pH) on the strength of peat treated by cement and cement-sodium silicate grout were investigated by evaluating the changes in unconfined compressive strength,moisture content,and scanning electron microscopy (SEM) of samples with time in different pH media.The results indicate that peats treated by cement-silicate have higher strength than peats treated by cement,due to an increase in pH value of the media.Furthermore,cement and cement-silicate are highly effective in ...     

粘土对聚羧酸减水剂性能的影响及机理研究

粘土作为杂质存在于混凝土的组分如砂石中,粘土对聚羧酸减水剂有较强的吸附性,从而影响混凝土的工作性。研究了不同粘土对掺聚羧酸减水剂的水泥浆体及砂浆流动性的影响规律,探讨了聚羧酸减水剂与粘土的相互作用机理。研究结果表明,不同粘土对水泥浆体的流动性有不同程度的影响,蒙脱土和膨润土相对于高岭土及筛分土对砂浆的流动性影响更为显著;同时,相对于不掺聚羧酸的砂浆,粘土对掺聚羧酸减水剂砂浆的流动性影响更为显著。粘土自身的吸附性与疏水基的定向吸附共同作用及粘土中的金属离子与聚羧酸的螯合作用可能是粘土吸附聚羧酸减水剂的机理。     

高效减水剂分散、助磨与减水复合效应实验研究

研究了高效减水剂与胶凝材料共粉磨时间高效减水剂对物料分散性和物料物磨效率的影响,以及共粉磨法与同掺法对高效减水剂减水效果的影响,结果表明,高效减水剂的存在有助于改善粉磨物料分散性,并可提高粉磨效率。与同掺法相比,采用共粉磨法可提高高效减水剂的减水效果,且水泥净浆稠度经过变化小,从而表明,用共粉磨改性超细水泥配制高性能砼时,用水量相同情况下,其初始坍 落度较同掺法时大,而坍 落度损失较小。     

石墨烯对水泥净浆力学性能及微观结构的影响

为改善石墨烯纳米材料疏水性,采用硝酸氧化和超声波法制备石墨烯分散悬浮液,考察石墨烯质量分数对水泥净浆力学性能及其微观结构的影响,探讨石墨烯的增强增韧作用机制,结果表明,水泥基复合材料的抗压、抗折强度随着石墨烯质量分数的增加呈先增大后减小的趋势,且最佳质量分数为水泥质量的0.02%.通过SEM和FT-IR对硬化水泥石的结构进行表征,发现石墨烯能够促进水泥水化产物的生长,改变水化晶体的形状、尺寸,使其有形成完整、簇状的趋势,但并未与水泥发生化学反应,改变其生成物类型.     

养护制度对粉煤灰复合水泥浆体干燥收缩及孔径分布的影响

将水泥试件在水中养护6天和13天后放入干燥养护箱中,测定其质量损失和干燥收缩。采用氮吸附方法测定不同龄期时的孔径分布。结果表明:粉煤灰复合水泥浆体,干燥收缩早期变化较为明显,随着龄期延长,变化逐渐变缓;水养时间延长,干燥收缩减小;不同水养时间养护后,粉煤灰复合水泥浆体4-40nm孔径体积含量减小,相应干燥收缩减小。     

Effect of coal gangue with different kaolin contents on compressive strength and pore size of blended cement paste

The effects of activated coal gangue on compressive strength, porosity and pore size distribution of hardened cement pastes were investigated. Activated coal gangue with two different kaolin contents, one higher and one lower, were used to partially replace Portland cement at 0%, 10%, and 30% by weight. The water to binder ratio（w/b） of 0.5 was used for all the blended cement paste mixes. Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content. The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.     

溶液酸度对磁性活性炭吸附性能和磁性能的影响

以太西无烟煤为原料、Fe3O4为添加剂制备煤基磁性活性炭,用不同浓度的盐酸溶液浸泡,测定酸液浸泡前后活性炭的碘值和亚甲蓝值,采用X射线衍射仪和振动样品磁强计分别测定、表征活性炭中含铁化合物的组成和磁性能.结果表明,溶液酸度对磁性活性炭的吸附性能和磁性能均有影响,当溶液酸浓度达到1mol/L时,磁性活性炭浸泡后的碘值提高了7.9%、达732.49mg/g,比磁化系数从259×10-7 m3/kg降低到7.16×10-7 m3/kg,但仍能采用磁场分选回收;当溶液酸浓度达到2mol/L时,磁性活性炭完全失磁.     

Chemieal Strueturcs and Adsorptive Behaviors of Superplastieizers on β-C2S

The chemical structures of four types of superplasticizers （SPs） and their adsorptive behaviors on β-C2S were investigated. The adsorption properties of SPs on β-C2S were measured and the relationship between the adsorption quantity and the specific surface of β-C2S was analyzed. The experimental results show that the adsorption quantity increases with the surface area increase of β-C2S, but the adsorption quantity per surface area is similar, which means that the main adsorbent is β-C2S itself. Polycarboxylic ester （PCE） showed the highest adsorption amount on β-C2S, followed by β-naphthalene sulfonates （NSF） and formaldehyde-acetone condensates sulfonates （FAS）, amino sulphonate （AS） showed the least adsorption amount on β-C2S. PCE affected the surface potential of β-C2S particles in water differently in comparison with other types of SPs. The adsorption capacity of SPs on β-C2S is determined by factors such as molecular structure, functional groups and molecular weight of SPs.     

聚丙烯酸铵吸附对TiO2悬浮液稳定及流变性的影响

研究了NH4 PAA在纳米TiO2 悬浮液中的作用 .对NH4 PAA在TiO2 表面的吸附进行了探讨 .结果表明 ,NH4 PAA的吸附量随pH值的增大而减小 .随NH4 PAA添加量的增加 ,纳米TiO2 粉体的等电点由pH =5 .9移动到pH =2 .7处 .高浓度TiO2 悬浮液的流变性能与NH4 PAA的加入量有关 ,加入NH4 PAA可降低悬浮液的粘度 .选择适当的NH4 PAA的添加量与pH值范围可有效改善悬浮液的稳定性和流变性 .     

添加剂对高碱煤灰渣流动特性及钠捕获效率的影响

为了给液态排渣锅炉安全燃烧准东高碱煤提供理论依据,在水平管式炉上利用刚玉斜坡对添加不同质量分数 SiO₂、CaO、Fe₂O₃和MgO的准东煤灰渣在空气气氛下的流动性能进行研究. 利用XRF技术对煤灰渣的钠质量分数进行分析,并通过钠捕获效率来表征煤灰渣的固钠效果. 研究表明：SiO₂和Fe₂O₃能够促进准东煤灰熔融.当SiO₂的质量分数为10% 时,煤灰渣由结晶渣逐渐转变为玻璃体渣,流动性能大大提高;而CaO和MgO则会抑制煤灰熔融,导致流动性能降低. 随着SiO₂添加比例的增加,灰渣对钠的捕获效率逐渐升高,当SiO₂的质量分数达10%时,钠捕获效率由原先的23%上升至30%;而随着Fe₂O₃添加比例的增加,钠捕获效率缓慢降低. 因此,当SiO₂的质量分数为10%时即可有效改善煤灰渣的流动性能,又能提高钠的捕获效率.