Time-Dependent Evolution of Microstructure and Mechanical Properties of Mortar
This study investigates the evolution of the microstructure and mechanical properties of mortar. Mortar samples consisting of Portland cement CEM I42.5 R (~ 60 vol% of quartz sand 0/2 mm, w/c-ratio of 0.5) were prepared and stored according to EN 1015. After 1, 2, 7, 14 and 28 days, the samples were oven-dried until constant weight as well as vacuum-dried. The microstructure of the mortar samples was investigated using scanning electron microscopy. Phase analysis was performed using X-ray diffraction, allowing the description of the crystalline phase evolution during hardening. Mechanical properties were evaluated using nanoindentation. Based on the nanoindentation results, the effective Young’s modulus was calculated using the model by Hashin and Shtrikman. The moduli calculated based on the values of the nanoindentation experiments were compared to the Young’s modulus determined in compression experiments. The results show that the Young’s modulus determined by the nanoindentation and compression test describes a degressive curve progression. The studies show a correlation between the results from nanoindentation tests and the mechanical properties obtained from the compression tests. Therefore, the microstructural evolution of mortar, including the influence of pores on Young’s modulus, must be taken into account to estimate the macroproperties from the nanoindentation tests.
KeywordsMicrostructural evolution of mortar Nanoindentation Scanning electron microscopy Young’s modulus Hashin and Shtrikman model
Financial support was provided by the German Science Foundation (DFG) in the framework of the Collaborative Research Center SFB 837 “Interaction modeling in Mechanized Tunneling”. This support is gratefully acknowledged.
- 8.Shih-Wei C, Chung-Chia Y, Ran H (2000) Effect of aggregate volume fraction on the elastic moduli and void ratio of cement-based materials. J Mar Sci Technol 8(1):1–7Google Scholar
- 19.Acker P (2001) Micro-mechanical analysis of creep and shrinkage mechanisms. In: Ulm FJ, Bazant ZP, Wittmann FH (eds) Creep, shrinkage and durability mechanics of concrete and other quasi-brittle materials. In: Proc. of the sixth international conference CON-CREEP6, Elsevier, Oxford, pp 15–25Google Scholar
- 26.Gartner EM, Young JF, Damidot DA, Jawed I (2002) Hydration of Portland cement. In: Bensted J, Barnes P (eds) Structure and performance of cements, 2nd edn. Spon Press, London, New York, pp 57–113Google Scholar
- 35.Yoshitake I, Rajabipour F, Mimura Y, Scanlon A (2012) A prediction method of tensile Young’s modulus of concrete at early age. Adv Civil Eng (article ID 391214) Google Scholar
- 39.Wu Z (2012) Experimental research and 3D modeling of EPS cellular concrete. Master’s thesis, Shanghai Jiao Toing UniversityGoogle Scholar
- 43.Yang CC, Huiang R, Yeih W, Sue IC (1995) Aggregate effect on elastic moduli of cement-based composite materials. J Mar Sci Technol 3:5–10Google Scholar