通过分别外掺Na2SO4(Na碱)和K2SO4(K碱)的方式,将低热水泥的总碱含量提高至0.8%,1.2%和1.6%,研究了不同碱含量和不同碱类型对低热水泥干燥收缩和自收缩的影响,并从水化动力学和孔结构方面,探究了不同碱含量和不同类型碱对低热水泥收缩性能的影响机制。结果表明,碱促进了低热水泥的干燥收缩和自收缩,这种促进作用不可忽略,且对自收缩影响时效短于干燥收缩,而以K2SO4形式存在的碱更易促进低热水泥干燥收缩和自收缩。基于水化动力学和孔结构研究,不同类型碱对低热水泥收缩性能的影响机制在于:碱促进了低热水泥结晶成核和晶体生长过程,细化了孔结构,增加了与收缩性能相关的孔分布,而以K2SO4形式存在的碱,能使这种促进作用和细化作用更加明显。该研究可为精细化提高混凝土耐久性提供数据支撑。
Abstract
The influence of type of alkali on the drying shrinkage and autogenous shrinkage of low-heat cement was investigated in this paper. By adding different dosages of Na2SO4 (Na alkali) and K2SO4 (K alkali), the total alkali content of low-heat cement was increased to 0.8%, 1.2%, and 1.6% respectively. The mechanism of different types of alkali in varied content affecting the shrinkage performance of low-heat cement was examined in terms of hydrokinetics and pore structure. Results illustrated that alkali could promote the drying shrinkage and autogenous shrinkage of low-heat cement, and such promotion should not be neglected. This effect on autogenous shrinkage required less time than that on drying shrinkage did. Besides, alkali in the form of K2SO4 was more likely to promote the drying shrinkage and autogenous shrinkage of low-heat cement. What’s more, alkali could promote the crystal nucleation and crystal growth stage of low-heat cement that led to the refinement of pore structure and the increment of pore distribution related to shrinkage properties. Such refinement and increment were more apparent when alkali existed in the form of K2SO4. The research finding offers data support for improving the durability of concrete.
关键词
低热水泥 /
收缩性能 /
碱 /
水化进程 /
水化动力学 /
孔结构
Key words
low-heat cement /
shrinkage performance /
alkali /
hydration process /
hydration kinetics /
pore structure
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1] 杨华全, 周世华,董 芸,等. 水泥－粉煤灰－矿渣粉三元胶凝体系体积稳定性的研究. 长江科学院院报,2009, 26(3):36-39.
[2] 李金玉,彭小平,曹建国,等. 高贝利特水泥低热高抗裂大坝混凝土性能的研究. 硅酸盐学报,2004,32(3):364-371.
[3] MEHTA P K.Concrete Technology at the Crossroads-Problems and Opportunities.ACI Special Publication,Concrete Technology:Past,Present and Future,1994,144:1-30.
[4] 理查德·W·伯罗斯,廉慧珍,覃维祖,等.混凝土的可见与不可见裂缝.北京:中国水利水电出版社,2013.
[5] HE Z,LI Z J. Influence of Alkali on Restrained Shrinkage Behavior of Cement-based Materials.Cement and Concrete Research,2005,35(3):457-463.
[6] 王 磊. C-S-H及其工程特性研究. 武汉:武汉大学出版社,2015.
[7] BENSTED J, BARNES P. Structure and Performance of Cements . Edition 2. USA: SPON Press, 2002.
[8] 陈美祝. 水泥基材料组分对早期水化及收缩开裂影响的研究. 武汉:武汉大学,2004.
[9] 刘 超,马忠诚,刘浩云. 水泥混凝土硫酸盐侵蚀综述. 材料导报,2013,27(7):67-71.
[10] HOSSACK A M, THOMAS M D A. Evaluation of the Effect of Tricalcium Aluminate Content on the Severity of Sulfate Attack in Portland Cement and Portland Limestone Cement Mortars. Cement and Concrete Composites, 2015, 56:115-120.
[11] 钱觉时,韦迎春,邓铃夕,等. 硅酸盐水泥中硫酸盐类型与作用. 硅酸盐学报,2014,42(2):169-177.
[12] LEE J K,CHU Y S,KWON C W. The Effects of Alkali Sulfate on the Hydration of a C3A-CaSO4·2H2O System. Journal of the Korean Ceramic Society,2007,14(44):471-476.
[13] LI Z J. Advanced Concrete Technology. USA: Wiley, 2011.
[14] TAZAWA E I,MIYAZAWA S,KASAI T. Chemical Shrinkage and Autogenous Shrinkage of Hydrating Cement Paste. Cement and Concrete Research,1995,25(2):288-292.
[15] SNYDER K A,BENTZ D P. Suspended Hydration and Loss of Freezable Water in Cement Pastes Exposed to 90% Relative Humidity. Cement and Concrete Research,2004, 34(11): 2045-2056.
[16] 李 洋,何 真,郭文康,等. 碱对低热水泥早期水化进程和微结构的影响. 建筑材料学报,2018,21(4):549-556.
[17] KRSTULOVI R,DABIP A. Conceptual Model of the Cement Hydration Process. Cement and Concrete Research,2000,30(5):693-698.
[18] 何 真,曹更新,李 洋,等. K+/Na+摩尔比对高碱含量水泥基材料早期开裂敏感性的影响. 水利学报,2016,47(12):1484-1492.
[19] MEHTA P K,MONTEIRO P J M. Concrete: Microstructure,Properties,and Materials . Edition 3. USA: Mc Graw-Hill Professional, 2006.
基金
中央级公益性科研院所基本科研业务费项目(CKSF2017034/GC,CKSF2017032/GC);国家重点基础研究发展计划(973计划)项目(2015CB655101)
PDF(1717 KB)
