Evaluation the potential of carbonation of hydrated limes paste

ABSTRACT

Hydrated lime is an air binder widely used in construction, mainly used in mortars for improving rheological behavior. The improvement in the technology of building materials reduced the use of hydrated lime mortars and has been replaced by additives and mineral admixtures, which in most cases confer similar characteristics of mortars in the fresh state but reduced performance in the hardened state. Another important factor which contributes to reduction of its use in mortars refers to the reduced gain strength at early ages, due to slow hardening speed; the solidification depends on the contact with the carbon dioxide from the air. The use of high thicknesses of lime mortar is also a factor in reducing its use because it makes the reaction even slower, affecting the construction schedule. In this context, this article aims to evaluate the potential for carbonation of five different types of hydrated limes found in the Paraná market. To evaluate the carbonation, lime pastes were made and were packed in the laboratory environment and in carbonation chamber with controlled temperature and humidity. It became possible to observe the progress of carbonation by weighing of samples and for further evaluation was carried out the diffraction X-Ray analysis. It was found that samples were placed in the chamber weigh gain only during the first days. Samples were left in the laboratory environment at different behavior: at the beginning of the experiment the carbonation rate was low, but at the end, compared with the sample in the chamber, the rate was higher. This may due to the rapid carbonation on the surface, and consequently reducing the surface pores of the samples in the chamber, hindered the penetration of CO₂ throughout the experiment in deeper layers. In this way, the laboratorial environmental showed more favorable conditions to the carbonation reaction than carbonation chamber, because of the temperature (average of 20° C) and humidity (up to 80%). The progress of the carbonation reaction in the carbonation chamber wasn't favorable because of the aggressive environmental conditions.

Keywords:
hydrated lime; carbonation; mortar; carbon dioxide