摘要
为了在建筑工程中有效利用石灰石粉资源,本文运用混凝土材料科学基本理论,通过试验测试手段,分析了石灰石粉的基本性质,较为系统地研究了石灰石粉掺量、细度对砂浆、混凝土工作性能和强度的影响,并比较分析了掺石灰石粉的混凝土的碳化性能、干缩性能及孔隙结构。取得如下研究成果:
1、在试验采用的三个等级的石灰石粉、水泥和Ⅱ级粉煤灰中,小于10μm粒径的细颗粒含量分别为40.8%、43.8%、47.2%、20.3%、27.2%,需水量比分别为95.7%、93.9%、91.3%、100%、100%,可见石灰石粉中的细颗粒含量远大于水泥,其填充效应将产生一定的减水效果。
2、采用45μm方孔筛筛余4.6%的石灰石粉,当砂浆中石灰石粉掺量不大于20%时,石灰石粉的活性指数及水泥的强度贡献系数都较高,对体系中单位质量水泥强度的发挥有积极作用。
3、混凝土工作性能和抗压强度受石灰石粉掺量和细度影响较大。适当增大石灰石粉细度,能改善混凝土的工作性能,且能提高混凝土的早期强度。石灰石粉掺量大于20%后,混凝土的强度下降较快。掺入适量减水剂,有利于增大石灰石粉混凝土的流动性,强度略有升高。采用45μm方孔筛筛余4.6%的石灰石粉,在掺量不大于20%时,掺石灰石粉混凝土28天龄期抗压强度略低于普通混凝土,90天龄期抗压强度与普通混凝土相当。
4、石灰石粉适量取代水泥和细骨料,能够改善混凝土拌合物的流动性,增大其保水性和粘聚性,且能减小仅以石灰石粉等量取代水泥后对混凝土强度的不利影响。超量取代系数宜在1.3左右。
5、石灰石粉混凝土的毛细孔隙率要稍大于普通混凝土。石灰石粉掺量不大于20%时,石灰石粉混凝土的孔隙率随石灰石粉掺量的增加呈降低趋势。
6、同强度等级条件下,石灰石粉混凝土与普通混凝土的碳化性能无显著差异。石灰石粉混凝土的干缩随石灰石粉细度和掺量的增大呈现降低趋势,采用45μm方孔筛筛余为0.6%的石灰石粉,以15%的掺量,超量系数1.3配制的石灰石粉混凝土的干缩要稍低于普通混凝土。
In order to use limestone powder validly in the constructional engineering, the paper analyses the basic properties of limestone powder using the basic theory of concrete material science by means of laboratory test. It studies the influence to the workability and strength of mortar and concrete by adding quantity and fineness of limestone powder. Besides, this paper makes a comparative analysis on the anti-carbonation, dry shrinkage and pore structure of limestone concrete. The research results are as follows:
1. In the three degrees of the limestone powder,cement and class II Coal Ash used in the experiments, the content of fine particle whose grain diameter is smaller than 10μm is 40.8%、43.8%、47.2%、20.3%、27.2% and the water requirement is 95.7%、93.9%、91.3%、100%、100% respectively, the content of fine partice of limestone powder is more than that of cement, the filling effect of which can arouse water-reducing effect.
2. When the adding of mixing quantity of the limestone power in the mortar is not more than 20%, the activity index of limestone power and the strength factor of cement are both above normal by the use of limestone power with 4.6% 45μm sieve remains. It plays a positive role in unit mass of the cement strength in the whole system.
3. The adding content and fineness of limestone powder greatly affect the workability and compressive strength of concrete. Increasing the fineness properly can improve the workability and increase the early strength. If the content is more than 20%, the strength decreases rapidly. Adding the water-decreasing agent can help to improve the fluidness and the strength. When the limestone content of powder with 4.6% 45μm sieve remains is less than 20%, the 28 days' compressive strength is a little less than the normal concrete and the 90 days' compressive strength is nearly the same as the normal concrete.
4. The replacement of cement and fine aggregate by limestone powder can improve the workability and water-remain performance. This method is better than replacing the cement by the limestone powder. The exceeding substitution index is about 1.3.
5. The capillary porosity of limestone powder concrete is larger than that of the normal concrete. If the mixing quantity is less than 20%, the capillary porosity decreases with the content increases.
6. On condition of the same strength, the anti-carbonation properties between the limestone powder concrete and normal concrete is nearly the same. The dry shrinkage of limestone powder concrete decreases when the fineness and the content increases. When the content of limestone powder with 4.6% 45μm sieve remain is 15%, the exceed coefficient is 1.3, the dry shrinkage is smaller than the normal concrete.
引文
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