Fundamental investigation on the frost resistance of mortar with microencapsulated phase change materials

C Romero Rodríguez,F França De Mendonça Filho,S Chaves Figueiredo,E Schlangen,B Šavija

doi:10.1016/j.cemconcomp.2020.103705

C Romero Rodríguez, F França De Mendonça Filho + Show 3 more

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https://doi.org/10.1016/j.cemconcomp.2020.103705

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Abstract

Recent studies have shown that concrete containing Phase Change Materials (PCM) with low transition temperatures may reduce the number of freeze/thaw cycles suffered by the cementitious composite in temperate climates. Nevertheless, the positive influence of such admixtures on the frost resistance of cement-based materials has not been directly shown, nor the negative. In this study, mortars with different contents of microencapsulated PCM by volume of cement paste were studied with regard to the progression of their internal and salt scaling damages during freeze/thaw cycles. X-ray micro tomography was used to monitor damage development and spatial distribution in the mortars. Furthermore, the pore system and microstructure of the PCM-modified mortars were characterized to unveil the causes of the observed macroscopic behavior during frost weathering. The results show that limited amounts of PCM in mortar, namely 10% by volume of cement paste, results beneficial for the frost and scaling resistance of the composite. Whereas, for larger PCM additions, like 30% by volume of paste, the changes in microstructure, porosity and mechanical strength brought in by these admixtures resulted in worsened performance against freeze/thawing cycles.

Highlights

Concrete structures in cold climates may deteriorate due to frost action
As studied elsewhere [15], Phase Change Materials (PCM) can potentially smooth the temperature peaks during exposure and lessen the period to which the mortars are exposed to such extreme temperatures. In this experimental investigation we studied the frost resistance of mortar with different amounts of microencapsulated PCM
The internal damage and salt scaling were assessed via standardized methods such as length change measurements and monitoring of scaled mass, and a spatial distribution of the damage could be extracted from X-ray microtomography data

Summary

Introduction

Concrete structures in cold climates may deteriorate due to frost action. Freezing and thawing cycles may cause significant damage to structures such as concrete pavements, retaining walls, and bridge decks [1]. As the volume of ice is larger than the volume of the pore water, it will cause expansive pressures in the concrete unless there is sufficient space to accommodate this expansion [3]. Cracks in con crete present rapid pathways for ingress of deleterious species, such as moisture, CO2, and chlorides. Once these aggressive substances reach the reinforcement, they will lead to corrosion initiation and the end of service life. This may cause heavy expenditures for repair and replacement of such structures already at the early stage of exploitation. Excessive cracking should be avoided especially in cold cli mates where freezing and thawing often go hand in hand with appli cation of deicing salts

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