The total alkali content of low heat Portland cement, medium heat Portland cement and ordinary Portland cement were adjusted to 1.2% by adding Na2SO4 and K2SO4 respectively, in which the K2O/Na2O (by weight) were in the range of 0.4-13.7. The influence of alkali of different K2O/Na2O on shrinkage properties and cracking properties of cement-based materials were explored. Besides, with the help of microcalorimetry, scanning electron microscopy and energy dispersive spectroscopy, the influence mechanism of alkali of different K2O/Na2O on shrinkage properties and cracking properties of cement-based materials was revealed. The results show that with the increase of K2O/Na2O, the autogenous shrinkage and drying shrinkage of low-heat and ordinary Portland cement intensified, while those of medium-heat cemet first decreased and then increased, and the cracking sensitivity of different cement-based materials always increased. The difference in shrinkage properties caused by K2O/Na2O was related to the hydration process of cement-based materials. The difference in cracking sensitivity was not only related to shrinkage properties, but also affected by the morphology of hydrated calcium silicate (C-S-H), calcium hydroxide (CH) and the enrichment of elements in the interfacial transition zone (ITZ).
Key words
K2O/Na2O /
shrinkage properties /
cracking properties /
micro-morphology /
interfacial transition zone
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References
[1] MEHTA P K. Concrete Technology at the Crossroads: Problems and Opportunities[C] //Concrete Technology: Past, Present and Future. Michigan: ACI Special Publication, 1994, 144: 1-30.
[2] 王铁梦.工程结构裂缝控制[M].北京:中国建筑工业出版社,1997.
[3] 理查德·W·伯罗斯.混凝土的可见与不可见裂缝[M].廉慧珍,覃维祖, 李文伟,译.北京:中国水利水电出版社,2013.
[4] YANG K, ZHONG M, MAGEE B, et al. Investigation of Effects of Portland Cement Fineness and Alkali Content on Concrete Plastic Shrinkage Cracking[J]. Construction and Building Materials, 2017, 144: 279-290.
[5] 刘慧娴.低热硅酸盐水泥在海工混凝土中的应用研究[D].广州:广州大学,2019.
[6] 肖忠明.现代混凝土开裂的原因之综述[J].水泥工程,2015(1):72-79.
[7] HE Z, LI Z J. Influence of Alkali on Restrained Shrinkage Behavior of Cement-Based Materials[J]. Cement and Concrete Research, 2005, 35(3): 457-463.
[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[D].武汉:武汉大学,2004.
[9] 王 磊. C-S-H及其工程特性研究[D].武汉:武汉大学,2015.
[10] 李 洋,王述银,殷海波,等.碱对水泥基材料水化及水化产物的影响研究综述[J].长江科学院院报, 2019,36(1):127-133.
[11] 李 洋,蒋 科,黄明辉,等.Na碱和K碱对低热水泥收缩性能的影响[J].长江科学院院报,2020,37(3):125-130.
[12] BENSTED J, BARNES P. Structure and Performance of Cements[M]. Edition 2. London: CRC Press, 2002.
[13] LEE J K,CHU Y S,KWON C W. The Effects of Alkali Sulfate on the Hydration of a C3A-CaSO4·2H2O System[J]. Journal of the Korean Ceramic Society,2007,14(44):471-476.
[14] TAZAWA E I, MIYAZAWA S, KASAI T. Chemical Shrinkage and Autogenous Shrinkage of Hydrating Cement Paste[J]. Cement and Concrete Research, 1995, 25(2): 288-292.
[15] WANG L, ZHOU S H, SHI Y, et al. Effect of Silica Fume and PVA Fiber on the Abrasion Resistance and Volume Stability of Concrete[J]. Composites, 2017, 130: 28-37.
[16] 李文伟,理查德·W·伯罗斯.混凝土开裂观察与思考[M].北京:中国水利水电出版社,2013.
[17] RICHARDSON I G. Tobermorite/Jennite- and Tobermorite/Calcium Hydroxide-based Models for the Structure of C-S-H: Applicability to Hardened Pastes of Tricalcium Silicate, β-Dicalcium Silicate, Portland Cement, and Blends of Portland Cement with Blast-Furnace Slag, Metakaolin, or Silica Fume[J]. Cement and Concrete Research, 2004, 34(9): 1733-1777.
[18] CONSTANTINER D, DIAMOND S. Alkali Release from Feldspars into Pore Solutions[J]. Cement & Concrete Research, 2003, 33(4): 549-554.
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