| 摘要: |
| 选用聚羧酸醚（PCE）和萘系磺酸盐（PNS）2种超塑化剂和粒径分别为3000目（4μm），1500目（8μm）和1250目（10μm）的3种天然石灰石粉，制备了水灰比或水胶比（质量比）为0.3的硅酸盐水泥浆.采用同轴圆筒式流变仪测量其流变曲线，并应用H B流变模型对测试数据进行拟合处理.结果表明：当超塑化剂掺量达到一定量时，表征水泥浆剪切增稠流变行为的流变指数n大于1，超塑化剂掺量越大，n值越大；当两种超塑化剂掺量相同时，PCE的n值较PNS的大；平均粒径与水泥颗粒相差越大、粒径分布越分散的石灰石粉取代水泥后，n值越小.PCE的空间位阻作用分散减弱了水泥颗粒间相互作用力，剪切作用下水泥颗粒容易形成“动水颗粒丛”，水泥浆更易发生剪切增稠现象；多分散粒径比单粒径或粒径分布较窄的悬浮体系有更多的自由空间，颗粒间动水压力难以使颗粒形成“动水颗粒丛”，浆体不易发生剪切增稠现象. |
| 关键词: 水泥浆体 流变性能 剪切增稠 超塑化剂 石灰石粉 |
| DOI：10.3969/j.issn.1007 9629.2013.05.002 |
| 分类号: |
| 基金项目:铁道部重点科技项目计划（2010G002 F） |
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| Effect of Superplasticizers and Limestone Powders on Shear ThickeningBehavior of Cement Paste |
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DENG De hua, ZHU Rong, PENG Jian wei, WANG Chuan yan, WANG Shi xiong
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School of Civil Engineering, Central South of University, Changsha 410075, China
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| Abstract: |
| Two kinds of superplasticizer, polycarboxylate ether based superplasticizer(PCE) and polynaphthalene sulfonate based superplasticizer(PNS), and three kinds of natural limestone powder whose particle sizes are 3000 mesh(4μm), 1500 mesh(8μm) and 1250 mesh (10μm) respectively were added in Portland cement pastes with the water cement ratio of 0.3. The rheological curves of these cement pastes were determined by means of a concentric cylinder rheometer and all the rheological curves were modeled by Herschel Bulkleys equation. The results indicate that at a certain use level of superplasticizers, the rheological index n characteristic of shear thickening behavior is greater than 1, and the more the superplasticizers added, the greater the value. At the same content, the value n for the cement paste with PCE added is greater than that with PNS added. On the other hand, the limestone powder, as a replacement of some amounts of cement, can modify the intensity of shear thickening compared to plain cement pastes. When the average particle size and size distribution of the limestone powder are quite different from those of cement and the particle size in mixture becomes more and more polydisperse, the vulue n is smaller. The interaction forces among cement particles dispersed by steric repulsion are weaker than cement particles dispersed by electrostatic force, therefore, PCE are more likely to make cement particles form hydroclusters under a certain shear and cement pastes show shear thickening behavior. There is more space for flow in a polydisperse suspension compared to a monodisperse suspension, which results in lower hydrodynamic forces between the particles, hence the shear thickening behavior of the polydisperse cement paste is not markable |
| Key words: cement paste rheological behavior shear thickening superplasticizer limestone powder |
