免煅烧磷石膏砖的制备和性能研究

在活性激发剂的作用下,利用矿渣、磷石膏(PG)和水泥混合制备磷石膏基胶凝材料(PGS),然后研究砂率和粉煤灰掺量对PGS砂浆性能的影响.结果表明:当激发剂掺量为3％时,20℃(湿度大于70％)养护28d的PGS固化体的抗压强度和抗折强度(41.9MPa和7.1MPa)分别较未掺激发剂时提高了89.6％和73.2％,28d软化系数为0.94;PGS固化体28d的总孔隙率(12.21％)较7d的总孔隙率降低了46.8％;当砂率为1∶1时,磷石膏砖的性能最佳,28d的抗压强度和抗折强度分别为56.9MPa和4.8MPa;当粉煤灰掺量为20％时,磷石膏砖的28d抗压强度和抗折强度分别为35.8MPa和3.3MPa,28d吸水率和软化系数分别为2.3％和0.90,质量损失率、抗压强度损失率和抗折强度损失率分别为1.9％、5.5％和4.3％.     

磷酸镁水泥性能的研究进展

磷酸镁水泥由过烧氧化镁和可溶性磷酸盐组成,是一种新型的水硬性胶凝材料.它早期强度高、收缩小、抗硫酸盐侵蚀能力强,能够与硅酸盐水泥基材料形成较强的粘结力,但其耐水性较差,原材料成本较高.因此,各类矿物掺合料如矿渣、粉煤灰、偏高岭土等被尝试用来取代部分原材料.在适当的掺量与取代方式下,矿物掺合料能够延缓凝结时间,提高抗压强度,并且能够改善耐水性.此外,氧化镁与磷酸盐的物质的量比、水胶比等也决定着磷酸镁水泥的性能.本文对磷酸镁水泥的水化机理、抗压强度、粘结强度、耐久性、体积稳定性进行了总结,指出了现有研究中的不足,并给出了建议与展望.     

矿物掺合料对聚羧酸减水剂与水泥相容性的影响

高性能减水剂与水泥适应性差会导致混凝土流动性和坍落度损失过快,矿物掺合料将影响高性能减水剂与水泥的相容性。对比研究矿物掺合料种类和掺量对水泥净浆、砂浆和混凝土流动性的影响;采用TOC法测试了矿物掺合料对聚羧酸减水剂吸附量的影响;分析了矿物掺合料影响聚羧酸减水剂与水泥相容性的机理。结果表明,粉煤灰和矿渣对提高水泥净浆流动性具有一定的叠加效应,可用胶砂减水率的加权平均值进行量化;硅灰对水泥浆体流动性的不利影响远大于粉煤灰和矿渣的辅助减水分散作用,不利于改善聚羧酸减水剂与水泥的相容性;粉煤灰和矿渣增加聚羧酸减水剂在水泥体系中的吸附量;粉煤灰和矿渣对聚羧酸减水剂在混凝土中的减水分散效果有改善作用但不显著。     

活性掺合料对脱硫基粉刷石膏制品性能的影响

利用脱硫石膏生产建筑石膏已经成为当前解决固体排放物问题的有效途径。粉刷石膏在耐水性和力学性能等方面的弱点影响其使用范围。本文研究复合掺加不同含量的活性掺合料对石膏制品耐水性和力学性能的影响。研究表明,掺加水泥和矿渣的效果最好,其耐水性可以提高40%,力学性能提高48%。     

矿物掺合料对水泥砂浆TSA侵蚀的影响

研究了硅灰、粉煤灰、矿渣对水泥砂浆TSA侵蚀的影响,采用掺30%石灰石填料的砂浆件,测试各砂浆在5±1℃的2%MgSO4溶液中浸泡1年后的外观、强度及矿物成分变化.结果表明:掺石灰石粉使水泥砂浆受侵蚀后表面呈软泥状,主要腐蚀产物为硅灰石膏和石膏,表现为典型的TSA破坏特征,其强度损失率大于纯水泥砂浆.矿物掺合料的加入降低了水泥石中CH晶体含量,从而在一定程度上提高了水泥砂浆的抗TSA侵蚀能力.矿物掺合料对水泥石中CH晶体的减少与对抗TSA侵蚀性的改善效果具有相同的规律,其优劣次序为:60%矿渣粉>5%硅灰 25%矿渣粉>8%硅灰>30%矿渣粉>20%粉煤灰>无掺合料.     

激发剂在大掺量粉煤灰水泥中的应用研究

利用粉煤灰、水泥熟料、石灰、石膏辅助少量的粉煤灰活性激发剂研究生产高掺量粉煤灰水泥.试验表明,激发剂能大大提高粉煤灰的活性和早期强度.生产的大掺量粉煤灰水泥,其3天、28天的抗压强度分别达到18MPa和50MPa,并且凝结硬化快,早期强度高,后期强度发展迅速.     

矿物掺合料对水泥基材料耐海水侵蚀性能的影响研究

加入适当矿物掺合料是使水泥基材料达到高性能的重要手段之一。本课题从工程应用的角度出发,以磨细矿渣和磨细矿渣-粉煤灰复合掺合料为研究对象,着重研究了矿物掺合料对水泥基材料耐海水侵蚀性能的影响。     

活性掺合料对再生混凝土与钢筋粘结性能的影响

通过单掺粉煤灰、单掺矿渣、复掺粉煤灰和矿渣三种不同改性方案,研究矿物掺合料对再生混凝土与钢筋粘结强度的影响,为再生混凝土合理使用矿物掺合料提供试验依据。     

偏高岭土掺合料对水泥胶砂强度的影响

将不同比例的偏高岭土与矿渣、粉煤灰复合掺入水泥砂浆,分析水胶比和偏高岭土掺合料对水泥胶砂强度的影响,并借助活性指数综合分析偏高岭土掺合料的诱导激活效应。研究结果表明:偏高岭土与其他矿物参合料复掺比例一定时,随水胶比增大,水泥胶砂的强度呈下降趋势。当水胶比一定时,掺量在5%～15%范围之内,偏高岭土与矿渣复掺可提高水泥的早期强度;偏高岭土、矿渣与粉煤灰复掺更有助于改善水泥3～7d的抗折和抗压强度。偏高岭土在复掺比例为40%左右,水泥胶砂的抗折强度和抗压强度活性指数达到最佳。     

微组分对磷铝酸盐水泥耐水性的影响初探

以净浆力学强度及Ca”和[A1O4]^5-离子溶出浓度为耐水性评价指标，研究了微组分石膏对磷铝酸盐水泥（phosphoaluminate cement，PALC）的影响，并通过S电位、XRD和孔结构等技术分析了其耐水性机理。结果表明：在浸水过程中，掺石膏和未掺石膏的磷铝酸盐水泥硬化浆体的力学性能均在不断提高，Ca^2＋和[AIO4]^5-的溶出浓度不断减小。相比较而言，掺石膏的磷铝酸盐水泥试样在浸水早期的力学性能和离子溶出浓度较未掺的变化不大，但在长期浸水的过程中，前者力学性能明显高于后者，而Ca^2＋和EAIO4]^5-溶出浓度却显著下降，这表明在磷铝酸盐水泥中掺入石膏，对其早期耐水性影响不大，但对长期耐水性的提高是十分有利的。     

Simulation of a temperature rise in concrete incorporating fly ash or slag

Granulated slag from metal industries and fly ash from the combustion of coal are among the industrial by-products and have been widely used as mineral admixtures in normal and high strength concrete. Due to the reaction between calcium hydroxide and fly ash or slag, compared with Portland cement, the hydration of concrete containing fly ash or slag is much more complex. In this paper, by considering the producing of calcium hydroxide in cement hydration and the consumption of it in the reaction of mineral admixtures, a numerical model is proposed to simulate the hydration of concrete containing fly ash or slag. The heat evolution rate of fly ash or slag blended concrete is determined from the contribution of both cement hydration and the reaction of mineral admixtures. Furthermore, a temperature rise in blended concrete is evaluated based on the degree of hydration of cement and mineral admixtures. The proposed model is verified with experimental data on the concrete with different water-to-cement ratios and mineral admixtures substitution ratios.     

Influence of cement type on ITZ porosity and chloride resistance of self-compacting concrete

With the increasing use of self-compacting concrete (SCC) its durability has come into focus. Concerning the microstructure of concrete, the porosity in the interfacial transition zone (ITZ) is regarded as a key feature for permeability and durability. Generally, a combination of cement and mineral admixtures is used for the production of SCC. In the present study, ITZ porosity of four SCC mixtures produced with ordinary Portland cement, Portland limestone cement, slag cement and ordinary Portland cement combined with fly ash is analyzed. Additionally, the chloride migration coefficient is determined. ITZ porosity and width of the SCC mixtures are similar. The substantial differences in the chloride migration coefficients show that the binder type has a stronger influence on permeability than the pore volume in the ITZ.     

碱式硫酸镁水泥耐酸腐蚀性能研究

为了研究碱式硫酸镁水泥耐酸腐蚀性能,将不同配比的水泥试样分别在柠檬酸溶液及水中浸泡不同龄期,再进行质量变化测定及抗折强度和抗压强度试验。采用XRD与SEM技术分析不同配比水泥试样浸泡于两种溶液后的物相组成和显微形貌。结果表明,掺入的矿渣和粉煤灰对碱式硫酸镁水泥具有良好的密实填充作用,降低了水泥的孔隙率,有效阻止了侵蚀介质的进入,其耐酸腐蚀性能与未掺矿渣和粉煤灰的碱式硫酸镁水泥相比有明显提升,其中,掺矿渣的碱式硫酸镁水泥耐酸腐蚀性能更优。     

矿物掺合料早期水化活性的测试和分析

本文采用环境扫描电子显微镜(ESEM)和热重-差热(TG-DTA)分析仪对磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的早期水化活性进行了系统测试和分析.理论和试验结果分析表明,掺合料取代水泥时,浆体早期抗压强度的提高取决于掺合料自身参与水化反应的速度和水化产物的数量.水化产物在掺合料颗粒表面沉积的速度和浆体中硅酸盐、铝酸盐水化产物的非蒸发水量随掺合料活性的提高而提高.掺合料活性按磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的顺序降低,将磨细矿渣微粉或高钙粉煤灰与低钙粉煤灰复合,可以克服低钙粉煤灰大掺量取代水泥时混凝土早期强度降低的缺陷,这是提高低钙粉煤灰在高强高性能混凝土中掺量的一个有效措施.     

矿物掺合料对地聚合物抗冻性能的影响

以碱激发偏高岭土制备地聚合物混凝土,分别研究了掺入15%的钢渣、矿渣或粉煤灰的地聚合物混凝土的力学抗压强度和抗冻性能,测试了地聚合物混凝土的真空饱水体积吸液率,运用XRD、SEM和DSC-TG等测试方法分析了矿物掺合料对地聚合物微观结构和水化产物的影响。结果表明:钢渣或矿渣能有效提高地聚合物混凝土的抗压强度,而粉煤灰的掺入使其强度稍有降低;地聚合物表观形貌中存在较多的孔洞和微裂缝导致其抗冻性能较差,掺入钢渣或者矿渣后地聚合物形成了新的产物C-S-H凝胶、C-A-S-H凝胶等并填充在结构中形成更加密实的板状结构,降低了地聚合物混凝土冻融破坏速率,五次冻融循环后地聚合物的相对强度均在90%以上,抗冻性能得到提高;粉煤灰降低了制备地聚合物混凝土的用水量且未水化的粉煤灰颗粒镶嵌在结构中增加了其密实性和抗冻性能,五次冻融循环后相对强度为86.9%,基准组的相对强度仅为79.7%。     

Effect of fly ash fineness on compressive strength and pore size of blended cement paste

This paper presents an experimental investigation on the effect of fly ash fineness on compressive strength, porosity, and pore size distribution of hardened cement pastes. Class F fly ash with two fineness, an original fly ash and a classified fly ash, with median particle size of 19.1 and 6.4 μm respectively were used to partially replace portland cement at 0%, 20%, and 40% by weight. The water to binder ratio (w/b) of 0.35 was used for all the blended cement paste mixes.Test results indicated that the blended cement paste with classified fly ash produced paste with higher compressive strength than that with original fly ash. The porosity and pore size of blended cement paste was significantly affected by the replacement of fly ash and its fineness. The replacement of portland cement by original fly ash increased the porosity but decreased the average pore size of the paste. The measured gel porosity (5.7–10 nm) increased with an increase in the fly ash content. The incorporation of classified fly ash decreased the porosity and average pore size of the paste as compared to that with ordinary fly ash. The total porosity and capillary pores decreased while the gel pore increased as a result of the addition of finer fly ash at all replacement levels.     

含粉煤灰或矿渣水泥石的孔结构

本文对掺粉煤灰与掺矿渣的水泥石孔结构特征进行了比较，结果表明：与掺矿渣相比，掺粉煤灰时水泥石总孔隙率较大，但趋于小孔分布，增加的主要是孔径在5nm以下的孔，孔径大于5nm的孔反而较少。     

Effect of fly ash and slag on the fracture characteristics of high performance concrete

The premature deterioration of concrete structures in aggressive environments has necessitated the development of high performance concrete (HPC). The major difference between conventional concrete and HPC is essentially the use of chemical and mineral admixtures. The improved pore structure of HPC achieved by the use of chemical and mineral admixtures causes densification of paste-aggregate transition zone, which in turn affects the fracture characteristics. Hence, studies were taken up to investigate the effect of fly ash and slag on the fracture characteristics of HPC. Beam specimens (geometrically similar and single size variable notch) with locally available fly ash (25%) and slag (50%) as cement replacement materials were prepared and tested in a servo-controlled Universal Testing Machine (UTM) under displacement control. From the value of the peak load for each beam, various fracture parameters were calculated. The results show that there is a reduction in the fracture energy due to addition of fly ash or slag, which can be attributed to the presence of unhydrated particles of size larger than that of normal flaws in concrete. Also due to densification, the post peak behaviour is steeper for the fly ash or slag based HPC mixes. The results of the investigation are presented in this paper.     

铜渣粉作为混凝土掺合料的研究进展

铜渣是铜冶炼和精炼过程的副产物,以每产1 t铜副产2.2 t铜渣计算,2017年全球铜渣排放量达到了5 170万t。但目前的铜渣处理仍以堆放为主,不仅占用了大量土地,重金属成分对堆放地也造成了严重的环境污染。铜渣,特别是水淬铜渣中含有较多的玻璃体,用作混凝土掺合料可以替代粉煤灰和矿渣,解决某些地区掺合料紧缺的状况。本文归纳总结了铜渣粉对混凝土工作性、力学性能和耐久性的影响,分析了铜渣作为掺合料使用时的环境安全性,提出了铜渣作为掺合料使用应注意的问题,为铜渣粉在混凝土行业中规模化应用提供了参考。 近年的研究成果表明,水淬铜渣中的玻璃体含量高、活性更好,而缓冷铜渣的玻璃体含量虽低,但仍有一定的活性。由于存在活性低和重金属成分高的问题,铜渣粉对混凝土工作性、力学性能和耐久性的影响比矿渣、粉煤灰等常见掺合料复杂得多,阻碍了铜渣粉作为掺合料在混凝土中的应用。 虽然存在不同观点,但多数研究成果表明铜渣粉可起到降低放热量、改善工作性及减少用水量的作用,同时也会产生泌水率增加的问题。由于活性偏低、重金属成分较高,铜渣粉的缓凝作用明显,不过大掺量使用所引起的凝结时间延长问题在多数研究中是可控的。铜渣粉导致混凝土早期强度不足,可通过添加激发剂、提高细度、降低水灰比等方式予以缓解和控制。铜渣粉对混凝土强度的负面影响会随龄期延长逐渐减轻,甚至在一段时间后对强度有利。此外,铜渣粉还能提高混凝土弹性模量并减少收缩,对抗断裂性能也无明显不利影响。但以不同指标评价混凝土脆性时,铜渣粉的作用还存在较大的争议。由于可促使毛细孔隙等有害孔隙数量减少,铜渣粉可使混凝土的吸水速率和吸水量降低,从而使耐久性等级有所改善。除优化孔隙结构外,铜渣粉与Ca(OH)₂反应生成C-S-H凝胶,可改善过渡区,提高混凝土抗碳化、抗氯离子渗透性和抗硫酸盐侵蚀的能力。