A study on development of recycled cement made from waste cementitious powder

With the goal of achieving sustainable development, many studies have been performed on approaches to reducing environmental load and cutting construction-related waste and greenhouse gas emissions. For this reason, this study aims to reduce carbon emissions and preserve the fixed materials such as limestone by utilizing the presumably high value-added cementitious powder of waste concrete, which is not currently being recycled. First, the chemical properties of cementitious powder were analyzed to manufacture recycled carbonic cement by deriving the optimal mix proportion of the materials using the industrial byproduct (former slag) and limestone as a property adjustment. To make a clinkering evaluation, Free CaO measurement, an XRD analysis, a thermal analysis, a compressive strength test and a flowability analysis were performed. Through this series of analyses, overall properties were found to be at 80% those of OPC or better. In addition, when using the cementitious powder as a substitute for limestone, it was discovered that the carbon emissions were reduced by up to 46%. However, as the amount of fine aggregate that was not separated from the cementitious powder due to its similar grain size and shape increased, the plasticity and the reduction in carbon emissions were radically decreased. Moreover, when the fine aggregate was mixed in the proportion of more than 30%, it is believed to be hardly materialized. Therefore, an effective separation technology of cementitious powder from fine aggregate should be researched and developed in the future. (C) 2015 Elsevier Ltd. All rights reserved.