# Thermal Insulation and Compressive Strength of Lightweight Geopolymer Foam Concrete Exposed to Accelerated Weathering by Carbonation, Salt Fog and UV Light

## TL;DR

This study examines how geopolymer foam concrete degrades under carbonation, salt fog, and UV exposure, finding that salt fog causes the most significant mechanical damage.

## Contribution

The study introduces a novel evaluation of geopolymer foam concrete's performance under combined accelerated weathering conditions.

## Key findings

- Carbonation at 40°C increased thermal conductivity by ~48% due to reduced porosity.
- Salt fog exposure reduced compressive strength by 69% due to NaCl penetration.
- UV radiation caused minor compressive strength reduction of up to 7%.

## Abstract

This study investigates the deterioration of the thermal and mechanical properties of geopolymer foam concrete (GFC) subjected to accelerated weathering through carbonation, salt fog, and UV radiation. GFC blocks were synthesized using metakaolin as the aluminosilicate precursor, activated with an alkaline solution consisting of 8 M NaOH and sodium silicate (Na2SiO3) at a NaOH/Na2SiO3 ratio of 0.51 wt.%. A 30% (v/v) H2O2 solution served as the foaming agent, and olive oil was used as the surfactant. Accelerated carbonation tests were conducted at 25 ± 3 °C and 40 ± 3 °C, under 60 ± 5% relative humidity and 5% CO2, with carbonation depth, carbonation percentage, density, porosity, and thermal conductivity evaluated over a 7-day period. In parallel, specimens were exposed to salt fog and UV radiation for 12 weeks in accordance with ASTM B117-19 and ASTM G154-23, respectively. Compressive strength was monitored every week throughout the exposure period. Results show that carbonation temperature governs the type and kinetics of carbonate formation. The carbonation process, at 40 °C for 7 days, increased the density and reduced the porosity of GFC, resulting in a ~48% increase in thermal conductivity. Salt fog exposure led to severe mechanical degradation, with NaCl penetration reducing compressive strength by 69%. In contrast, UV radiation caused only minor deterioration, decreasing compressive strength by up to 7%, likely due to surface-level carbonation.