共查询到17条相似文献,搜索用时 187 毫秒
1.
《深圳大学学报(理工版)》2014,(4)
研究磷酸盐对α半水脱硫石膏水化反应进程、液相离子浓度与过饱和度以及水化产物形貌与硬化体强度的影响,结合X光电子能谱分析技术对磷酸盐缓凝机理进行分析.结果表明,磷酸盐抑制α半水脱硫石膏早期水化,使水化放热减缓,早期水化速率降低,凝结时间延长;磷酸盐改变了二水石膏晶体生长习性,晶形由长棒状转化为板状,并使晶体粗化,硬化体强度降低;磷酸盐通过化学作用吸附在二水石膏晶体表面,抑制离子扩散和晶面生长,这是二水石膏缓凝的内因,对晶面的选择性吸附改变了二水石膏晶体生长习性和形貌,是硬化体强度降低的原因所在. 相似文献
2.
研究了草酸钠对硬石膏水化进程、硬化体显微结构与强度、液相离子浓度与二水石膏析晶过饱和度的影响,从二水石膏晶体成核与生长的角度探讨了草酸钠的作用机理.草酸钠使硬石膏水化率提高,水化热集中,水化潜伏期缩短,水化进程加快;草酸钠使二水石膏晶体细化,硬化体结构致密,强度提高,是硬石膏水化活性的高效激发剂.草酸钠作用机理归纳为:草酸钠与硬石膏反应形成草酸钙沉淀与可溶硫酸盐,使液相SO2-4浓度大幅提高;提高二水石膏析晶过饱和度,使二水石膏临界晶核半径减小,晶体成核与生长速率加快;草酸钠促进硬石膏溶解. 相似文献
3.
缓凝剂对建筑石膏结构与强度的负面影响 总被引:13,自引:0,他引:13
利用SEM扫描电镜、MIP压汞测孔技术等测试手段.系统深入地研究了柠檬酸、多聚磷酸钠、骨胶3类常用典型缓凝剂对建筑石膏水化早期液相过饱和度、晶体形貌以及硬化体孔结构的影响,研究了石膏强度损失的内在原因和机制.结果表明:缓凝剂降低了胶凝材水化早期液相过饱和度,改变了二水石膏结晶习性和晶体形貌,晶体明显粗化,晶形也由针状转变为短柱状,大大削弱了晶体间的搭接,硬化体孔径增大,大孔比例明显增加,孔结构劣化,并最终导致建筑石膏强度的大幅度降低.强度损失与其缓凝效果基本成正比,掺量越高,缓凝时间越长,强度损失越大. 相似文献
4.
共晶磷是磷石膏中仅次于可溶磷的有害杂质,影响了磷石膏的应用性能。采用分析纯模拟共晶磷的生成条件制取共晶磷含量较高的石膏样品,经煅烧成半水石膏后加入到天然建筑石膏中,进行物理力学性能试验,并利用扫描电镜、原子吸收光谱、红外吸收光谱结合化学分析的手段,研究了共晶磷对石膏性能的影响及其作用机理。结果表明:共晶磷明显降低了建筑石膏的水化率,使二水石膏析晶过饱和度降低,晶体粗化,结构疏松,硬化体强度降低。在二水石膏煅烧成半水石膏的过程中共晶磷并没有发生变化,仍存在于石膏晶格中;在建筑石膏水化过程中,共晶磷从晶格中溶出,变成可溶性磷HPO42-溶解在浆体中,HPO42-电离出H+和PO43-,其中PO43-又迅速与溶液中大量存在的Ca2+结合,转变为难溶性Ca3(PO4)2覆盖在晶体表面,阻碍了石膏的进一步水化,从而导致硬化体强度降低,而富余的H+则导致了浆体pH值的降低。 相似文献
5.
半水石膏性能与微观结构的探讨 总被引:7,自引:0,他引:7
XRD、SEM分析表明对α型半水石膏晶体呈短柱状、结晶完好,β型半水石膏晶体呈片状、结晶较差;α型半水石膏水化物晶体呈板柱状,晶体交织形成致密硬化体结构,β型半水石膏水化物晶体呈针状、纤维状,晶体交织形成疏松的硬化体结构。晶体结构与形貌上的差异是导致α型半水石膏与β型半水石膏性能特别是力学强度差异的原因。 相似文献
6.
柠檬酸对建筑石膏缓凝作用影响因素的研究 总被引:2,自引:0,他引:2
研究了柠檬酸对建筑石膏凝结时间与流动度经时性的影响,以及建筑石膏细度、相组成、pH值、水化温度对柠檬酸缓凝性的影响。结果表明:柠檬酸是建筑石膏高效缓凝剂,可有效抑制其流动度经时损失;Ⅲ型无水石膏和二水石膏削弱柠檬酸的缓凝效果,比表面积增加,凝结时间缩短;柠檬酸在弱碱性条件下缓凝效果最好;柠檬酸的缓凝效果对温度很敏感,温度升高,缓凝性降低。 相似文献
7.
磷石膏颗粒级配、结构与性能研究 总被引:15,自引:1,他引:14
磷石膏的颗粒级配、结构是影响性能的重要因素.采用筛分、沉降天平分析、SEM显微结构分析,研究了磷石膏颗粒级配与二水石膏晶体形貌,测定了不同形态磷与有机物等杂质在磷石膏中分布.分析、测试了磷石膏胶结材的结构与性能.结果表明磷石膏的颗粒级配、形貌与天然石膏存在明显差异,它的颗粒级配成正态分布,二水石膏晶体粗大、均匀,以板状为主,其尺度比天然二水石膏晶体粗大.可溶磷与有机物覆盖于二水石膏晶体表面,其含量随磷石膏粒度增加而增加.粉磨使磷石膏颗粒形貌多样化,并改善颗粒级配,降低其胶结材需水量,使硬化体结构趋于密实,强度得以提高.磷石膏经过中和、粉磨预处理可制备出优等品建筑石膏. 相似文献
8.
磷石膏颗粒级配、结构与性能研究 总被引:2,自引:0,他引:2
磷石膏的颗粒级配、结构是影响性能的重要因素.采用筛分、沉降天平分析、SEM显微结构分析。研究了磷石膏颗粒级配与二水石膏晶体形貌,测定了不同形态磷与有机物等杂质在磷石青中分布。分析、测试了磷石膏胶结材的结构与性能。结果表明:磷石膏的颗粒级配、形貌与天然石膏存在明显差异,它的颗粒级配成正态分布,二水石膏晶体粗大、均匀,以板状为主,其尺度比天然二水石膏晶体粗大。可溶磷与有机物覆盖于二水石膏晶体表面,其含量随磷石膏粒度增加而增加。粉磨使磷石膏颗粒形貌多样化,并改善颗料级配,降低其胶结材需水量,使硬化体结构趋地密实,强度得以提高,磷石膏经过中和、粉磨预处理可制备出优等品建筑石膏。 相似文献
9.
《武汉理工大学学报》2017,(10)
磷建筑石膏强度低,应用受限。通过掺入高强石膏以获取满足强度的石膏胶凝材料,利废环保。结果表明:随高强石膏掺量增加,硬化体的绝干强度增大,但低于线性内插法计算的强度值,误差小于10%;线性膨胀率先减小后增加。通过X射线衍射分析、X射线光电子能谱和拉曼光谱知,混合石膏相与单一石膏相的水化产物均为二水石膏,其原子排列的精细结构没有本质差别。通过扫描电子显微镜可知,混合相的水化产物兼有磷建筑石膏和高强石膏的水化产物特征形貌。两种半水石膏水化速率差别大,导致晶粒间存在内应力,是强度和线性膨胀率降低的原因。 相似文献
10.
11.
在研究建筑石膏的复合磷酸盐缓凝剂基础上,探讨了缓凝型膨胀剂对建筑石膏 凝结硬化性能和膨胀性能的影响。碱金属磷酸盐与建筑石膏作用后使实浆PH值升高,液相呈碱性,处于碱性环境中的铵盐在建筑石膏水化热的促进下产生NH3气,推动料浆膨胀。 相似文献
12.
Chemical compositions,mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover,hydration heat and hydration compositions of activated coal-gangue-calcium oxide system,as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2O3. With the exciting of gypsum,the reaction of activated coal-gangue and Ca(OH)2 would produce hydration products as ettringite,calcium silicate hydrate,and calcium aluminate. The relationship between the curing age and the content of Ca(OH)2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coal-gangue-cement paste were more than that in the neat cement paste at the same hydration periods,and even existed at the later stage of hydration. Furthermore,the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal,and improve the structure of hardened cement paste. 相似文献
13.
《武汉理工大学学报(材料科学英文版)》2018,(6)
The objective of this study was to assess the feasibility of using the plant-source polymer of the matcha powder as a composite admixture for hemihydrate gypsum. Hemihydrate gypsum was mixed with different contents of matcha powder, and then the water requirement for the normal consistency, setting times, density, strength, hydration and microstructure of the hardened mixture were evaluated. The experimental results showed that it increased the water requirement for the normal consistency, and it regulated the setting times and reduced the density. Hemihydrate gypsum with more matcha powder had the higher water requirement, longer setting times and lower density. Less than 1% matcha powder had slight impact on the strength of hardened paste, but more than 1% matcha powder had a remarkable one. Matcha powder changed the hydration process and prolonged the induction and acceleration period. Small needlelike crystals were transformed into longer, larger and thicker ones as more matcha powder was mixed. This case is closely related to the prolongation of the induction and acceleration period. Besides, more and larger pores were observed in the hardened paste with more matcha powder. It is attributed to the appearances of the tea polyphenol in matcha powder and the larger and longer crystal morphology in hardened paste as well as the high water requirement for the normal consistency. These results are important to the application of matcha powder as a composite admixture for the hemihydrate gypsum as well as the prosperity and development of the tea industry. 相似文献
14.
采用抗压强度试验、X射线衍射分析、电镜扫描及压汞仪法等测试技术,测试和分析了超硫酸盐水泥在不同龄期的强度、水化产物及孔结构,并将其与普通硅酸盐水泥、矿渣水泥对比,探讨超硫酸盐水泥的水化机理.研究结果表明,超硫酸盐水泥早期强度较低,但后期强度发展快,28 d强度高于42.5普硅水泥;超硫酸盐水泥的主要水化产物为水化硅酸钙、钙矾石及少量石膏晶体,未见普硅水泥及矿渣水泥的主要水化产物氢氧化钙;90 d时,超硫酸盐水泥硬化浆体的阈值孔径、最可几孔径、中孔孔径及平均孔径均小于普硅水泥和矿渣水泥,具有更小的孔隙率和更高的密实度,有效地促进了超硫酸盐水泥后期强度的增长. 相似文献
15.
潘志华 《武汉理工大学学报(材料科学英文版)》2009,24(1):161-165
Red mud was activated to be a mineral admixture for Portland cement by means of heating at different elevated temperatures
from 400 °C to 700 °C. Results show that heating was effective, among which thermal activation of red mud at 600 °C was most
effective. Chemical analysis suggested that cement added with 600 °C thermally activated red mud yielded more calcium ion
during the early stage of hydration and less at later stage in liquid phase of cement water suspension system, more combined
water and less calcium hydroxide in its hardened cement paste. MIP measurement and SEM observation proved that the hardened
cement paste had a similar total porosity and a less portion of large size pores hence a denser microstructure compared with
that added with original red mud.
Funded by the National 973 Program of China (No. 2001CB610703) 相似文献
16.
采用DTA—TG、XRD、SEM以及宏观水化收缩和强度试验等手段研究了粉煤灰一脱硫石膏一水泥三元复合胶凝体系的水化过程、活性效应及微观结构等,根据试验结果总结了复合胶凝材料的水化动力学过程。结果表明,粉煤灰一脱硫石膏水泥石的钙矾石吸热峰强于基准样;在各组分相互活性激发和外掺激发剂作用下,粉煤灰一脱硫石膏水泥石中2次水化效应明显;SEM、XRD表明水泥石早期有明显的钙矾石生成,同时粉煤灰颗粒的表面侵蚀现象明显,进一步说明复合胶凝体系的早期活性得到有效激发,硬化后综合性能得到有效保证。且宏观收缩及强度试验也从侧面印证了微观试验结果。粉煤灰一脱硫石膏水泥基复合胶凝材料体系的研发可大量消耗燃煤电厂的工业废渣,具有显著的“绿色”效应。 相似文献
17.
本文试验研究了“黑液”(以棉短绒为造纸原料的纸浆废液)对水泥浆性能的影响。试验研究结果表明:“黑液”不改变水化产物的相,仅在早期抑制水泥浆的水化;“黑液”的减水作用和分散作用改善了水泥浆的孔结构,使水泥水化物分布均匀,并且提高硬化水泥浆的强度达20~30%。 相似文献