Effects of carbonation on mechanical properties of concrete under high temperature and impact

Abstract

This paper presents the results of an experimental study that investigated changes in the 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 pulverised-fuel ash) were cured for 28 days before accelerated carbonation under 4% carbon dioxide (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 were performed at ambient temperature and elevated temperature of 500°C. The results show that the mechanical performance of CEM I concrete was improved after carbonation – that is, static compressive strength increased at ambient and elevated temperatures, and the dynamic strength was higher than that of fresh concrete at the same strain rate at both ambient and elevated temperatures. However, CEM II concrete suffered reductions in compressive strength after carbonation.