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Evolution of internal temperature and relative humidity in mortar and concrete

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The continuously evolving state of moisture distribution in cement mortar and concrete plays a significant role in governing their deterioration. The absence of strong drying conditions in an indoor residential environment results in sustained dampness. The persistence of dampness can, in turn, enable damage through a wide range of degradation mechanisms including but not limited to mold growth, alkali-silica reaction, and corrosion of embedded steel elements.

The gradual loss of moisture due to drying or by self-desiccation may result in the manifestation of shrinkage cracks at later ages. The study of the evolution of moisture distribution in an initially saturated element subjected to realistic drying conditions enables an assessment of the potential damage. Over the last three decades, many researchers have pursued investigations to this end to better comprehend the evolution of internal temperature and relative humidity (RH) under different exposure conditions using sensor-based moisture meters.

The internal RH was observed to drop more rapidly in mixes with a lower w/b ratio and higher levels of OPC replacement. However, in a later study based on laboratory drying carried out at 20⁰C and 58% RH, it has been reported that the w/b ratio and the period of initial moist curing have little effect on the evolution of RH profiles in concrete.

It was also reported that the internal RH in samples exposed to rainfall was higher than those which were dried indoors. In addition to the contradictory observations on the effect of the w/b ratio, a limitation of these studies is the exclusion of the description of internal temperature conditions in concrete during the drying process.

Also, there is a dearth of data to establish the effect of w/b ratio. This also reflects in the contradicting conclusions made by some earlier studies. Most of the articles presented internal temperature and RH distributions in drying mortar and concrete, however, the studies related to the assessment of moisture transport parameters using such profiles are far apart and hard to find in the literature.

The reliable establishment of transport parameters, for example, hydraulic diffusivity is extremely important for designers and practitioners to understand the state of moisture distribution in the drying environment of the concerned material. The conduction of such experimental studies from the domain of durability of structures is soon going to be undertaken by teaching professionals and students at SGT University in the Department of Civil Engineering.

Written by
Dr. Mohammad Kamran
Assistant Professor
SGT University Gurugram