Mixed construction and demolition powder as a supplementary cementitious material: study in packaged pastes

estudo em pastas empacotadas

Resumen

The replacement of Portland cement (OPC) with mixed recycled powder (RMP) from demolition construction waste (CDW) intends more sustainable scenarios to produce less emissive cement, being the aim of this study. The CDW was first subjected to grinding and sieving until obtaining a fraction <0.15 mm. Then the particles were thermally activated at 800°C in a muffle for 0.5, 1, 2 and 3 hours. The levels of replacement of OPC by RMP were defined based on the particle packing method, varying between 0 and 65%. The study was carried out on pastes with a water/fines ratio between 0.07 and 0.14 and a superplasticizer admixture, with an evaluation of the compressive strength at 28, 63, and 91 days. The mechanical and environmental performance results of Portland cement pastes composed with CDW showed compressive strength superior to the reference, reaching 37 MPa for a replacement content of 45% at 28 days, promoting a reduction of up to 53% in CO₂ emissions per m³ of paste. The study indicated that treating and packaging RMP particles could potentially increase mechanical and environmental performance, becoming an alternative to promote the circular economy and cement with reduced carbon emissions.