Increased strength and related mechanisms for mortars at cryogenic temperatures

•Compressive and flexural strengths of mortars at 20 °C to −170 °C were tested.•Water content is the main factor influencing the cryogenic strength increase.•The freezing of capillary water leads to rapid increase of strength.•Both ice formed in capillary pores and gel pores contributes to the cryog...

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Bibliographic Details
Published in:Cryogenics (Guildford) 2018-09, Vol.94, p.5-13
Main Authors: Zhengwu, Jiang, Zilong, Deng, Xinping, Zhu, Wenting, Li
Format: Article
Language:English
Subjects:
Compressive strength
Cryoforming
Cryogenic temperature
Cryogenic temperatures
Flexural strength
Freezing
Ice formation
Low temperature physics
Moisture content
Mortars (material)
Pore size distribution
Pore water
Porosity
Shear strength
Thermodynamics
Thermoporometry
Water
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Summary:•Compressive and flexural strengths of mortars at 20 °C to −170 °C were tested.•Water content is the main factor influencing the cryogenic strength increase.•The freezing of capillary water leads to rapid increase of strength.•Both ice formed in capillary pores and gel pores contributes to the cryogenic strength increase. Properties of cement-based materials at cryogenic temperatures are quite different from those at room temperatures. The strength of mortars at cryogenic temperatures was experimentally studied and an empirical model was established. The freezing thermodynamic process of pore water and pore size distribution in mortars were characterized by differential scanning calorimeter (DSC) and thermoporometry (TPM), respectively. The relationship between the increased cryogenic strength and pore ice formation was discussed. The results showed that flexural strength of mortars increased at a higher rate than compressive strength. Water content and initial strength at room temperatures were the main factors influencing the cryogenic strength. Higher water content and higher initial strength resulted in higher cryogenic strength. Ice formation in pores is one of the main reasons for the mortar’s cryogenic strength increase. Nearly half of the water remained unfrozen in pores with radius less than 40 nm at −40 °C. Both ice formed in capillary pores and gel pores contributes to the strength increase observed at cryogenic temperatures.
ISSN:0011-2275
1879-2235
DOI:10.1016/j.cryogenics.2018.06.005