Effect of Metakaolin on Mechanical Properties and Microstructure of Reactive Powder Concrete

Abstract

Abstract: Reactive powder concrete (RPC) is a promising material which exhibits extrordinary mechanical properties and durability. To investigate the effect of metakaolin (MK) on RPC, the effects of 0%, 5%, 10%, 15% and 20% mass ratio of cementitious materials replaced by MK on the mechanical properties and microstructure of RPC were studied, which included MK pozzolanic activity index test, and the compressive, flexural strength and elastic modulus tests, X-ray diffraction analyzer (XRD), as well as scanning electron microscope (SEM), MIP and nanoindentation measurements. The results show that MK exhibits high pozzolanic activity at the early stage of cement hydration, and the 28 d compressive strength, flexural strength and elastic modulus of RPC with 10% MK increase by 20.1%, 18.0% and 11.4%, respectively, comparing with the reference group. The optimal dosage of MK is 10%. It shows that the incorporation of MK reduces the porosity of RPC matrix, and more additional C-S-H gel filling the pores of RPC matrix is generated by the “secondary hydration” reaction, which improves the microstructure of RPC after the microstructure analysis. Nanoindentation investigation shows that the mass fraction of 10% MK increases the content of high density C-S-H to increase the mechanical properties of RPC. This may be attributed to the pozzolanic activity and the micro-aggregate filling effect of MK.

Key words: metakaolin, reactive powder concrete, mechanical property, microstructure, nanoindentation

CLC Number:

TU528

CHEN Li, ZHOU Changshun, JIANG Chenhui. Effect of Metakaolin on Mechanical Properties and Microstructure of Reactive Powder Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(4): 1162-1169.

References

[1] 李新星,杨才千,周泉,等.基于正交试验的活性粉末混凝土强度及流动性研究[J].硅酸盐通报,2019,38(4):1201-1210.
LI X X, YANG C Q, ZHOU Q, et al. Research on strength and fluidity of reactive powder concrete based on orthogonal test[J]. Bulletin of the Chinese Ceramic Society, 2019, 38(4): 1201-1210 (in Chinese).
[2] 邓明科,马福栋,张阳玺,等.活性粉末混凝土抗压强度试验研究[J].硅酸盐通报,2017,36(8):2731-2736.
DENG M K, MA F D, ZHANG Y X, et al. Experimental study on the compressive strength of reactive powder concrete[J]. Bulletin of the Chinese Ceramic Society, 2017, 36(8): 2731-2736 (in Chinese).
[3] 安明喆,李同乐.活性粉末混凝土损伤后的抗氯离子渗透性能研究[J].混凝土,2012(3):15-17.
AN M Z, LI T L. Resistance to chloride ion penetration of reactive powder concrete after injury[J]. Concrete, 2012(3): 15-17 (in Chinese).
[4] BROOKS J J, MEGAT JOHARI M A. Effect of metakaolin on creep and shrinkage of concrete[J]. Cement and Concrete Composites, 2001, 23(6): 495-502.
[5] POON C S, KOU S C, LAM L. Compressive strength, chloride diffusivity and pore structure of high performance metakaolin and silica fume concrete[J]. Construction and Building Materials, 2006, 20(10): 858-865.
[6] COURARD L, DARIMONT A, SCHOUTERDEN M, et al. Durability of mortars modified with metakaolin[J]. Cement and Concrete Research, 2003, 33(9): 1473-1479.
[7] LI Z J, DING Z. Property improvement of Portland cement by incorporating with metakaolin and slag[J]. Cement and Concrete Research, 2003, 33(4): 579-584.
[8] 席书娜.偏高岭土在高性能混凝土中的应用研究[D].焦作:河南理工大学,2009.
XI S N. Application research of metakaolin in high performance concrete[D]. Jiaozuo: Henan Polytechnic University, 2009 (in Chinese).
[9] 姜广.生态型偏高岭土超高性能水泥基复合材料的制备及机理分析[D].南京:东南大学,2015.
JIANG G. Study on preparation and mechanism analysis of ecological metakaolin UHPFRCC[D]. Nanjing: Southeast University, 2015 (in Chinese).
[10] 赵晓刚.水化硅酸钙的合成及其组成、结构与形貌[D].武汉:武汉理工大学,2010.
ZHAO X G. Synthesis of calcium silicate hydrate and its composition, structure and morphology[D]. Wuhan: Wuhan University of Technology, 2010 (in Chinese).
[11] 李阳.偏高岭土提高水泥性能及水化机理研究[D].武汉:武汉理工大学,2017.
LI Y. Research on improving the performance of cement and hydration mechanism of metakaolin[D]. Wuhan: Wuhan University of Technology, 2017 (in Chinese).
[12] YOUNG J F. Review of the pore structure of cement paste and concrete and its influence on permeability[J]. ACI Special Publication, 1988, 108(1): 1-18.
[13] SIDDIQUE R, KLAUS J. Influence of metakaolin on the properties of mortar and concrete: a review[J]. Applied Clay Science, 2009, 43(3/4): 392-400.
[14] HE Z H, ZHAN P M, DU S G, et al. Creep behavior of concrete containing glass powder[J]. Composites Part B: Engineering, 2019, 166: 13-20.
[15] HE Z H, QIAN C X, ZHANG Y, et al. Nanoindentation characteristics of cement with different mineral admixtures[J]. Science China Technological Sciences, 2013, 56(5): 1119-1123.