Eco-Pozzolans as Raw Material for Sustainable Construction Industry: Comparative Evaluation of Reactivity Through Direct and Indirect Methods

A solution to reduce the consumption of raw materials and the generation of greenhouse gases is the partial replacement of clinker (the main constituent of cement) with supplementary cementitious materials. This study aimed to compare the reactivity of ten supplementary cementitious materials—synthetic/commercial ones and those from industrial and agricultural waste (eco-pozzolans). The characterization of the raw materials was carried out using X-ray fluorescence, the loss on ignition, X-ray diffraction, and the determination of the amorphous silica content and particle size distribution. The pozzolanicity assessment was carried out using the Frattini test (direct method) and electrical conductivity and pH tests (indirect method), with the latter presenting greater sensitivity and precision, enabling us to classify the pozzolan reactivity. Although synthetic/commercial pozzolans have higher silica content, the eco-pozzolans showed excellent reactivity results, thus indicating their use as sustainable pozzolans, presenting characteristics that enhance the performance of cement matrices and reduce the environmental impacts of production. Nyasil and rice leaf ash were the pozzolans that presented the greatest reactivity among those studied. The obtained results suggest that using industrial/agricultural waste like reactive pozzolans can help to mitigate the adverse impacts of cement production, address natural resource shortages, and promote a circular economy.