Effects of carbonation on mechanical properties of two types of concrete under extreme loadings of high temperature and impact

Abstract

This paper presents the results of an experimental study to investigate changes in mechanical properties of two types of concrete under normal and extreme loading conditions pre- and post-carbonation. Specimens of CEM I and CEM II concrete (concrete prepared with 20% replacement cement with PFA) were cured for 28 days before accelerated carbonation under 4% CO2 for 28 days at 20 °C and 57% relative humidity. Static compressive mechanical tests at ambient temperature were carried out for both concrete types. For CEM I concrete, static compressive mechanical tests were performed at elevated temperatures of 300, 500 and 650 °C, and high strain-rate tests at ambient and elevated temperature of 500 °C. The results show that the mechanical performance of CEM I concrete was improved after carbonation, i.e. increase of static compressive strength at ambient and elevated temperatures, and higher dynamic strength than fresh concrete at the same strain-rate at both ambient and elevated temperatures. However, CEM II concrete suffers reductions in compressive strength after carbonation.