# Effect of Microwave Radiation on the Properties of Hydrogel, Cork, Perlite, and Ceramsite

## TL;DR

This study examines how microwave radiation affects the water release and physical properties of hydrogel, cork, perlite, and ceramsite, with potential applications in materials engineering.

## Contribution

The novelty lies in analyzing microwave-induced water release and its impact on material properties for internal concrete curing.

## Key findings

- Hydrogels showed the highest water absorption (1000%) and fastest water release (45 min) under microwave radiation.
- After water release, hydrogels retained their water absorption ability but formed a solid structure instead of returning to a powdered state.
- Cork's water absorption varied depending on the material fraction.

## Abstract

The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material.