A comparative study on the pozzolanic activity between bamboo leaves ash and silica fume: Kinetic parameters

Silica fume is the most performing siliceous product among the pozzolanic materials. This is mainly related to his high content (around of 90%) of amorphous silica. However, this residue has a high cost and the quantities available are limited. This limits its use in the modern construction industry, particularly in developing countries. For this reason it is motivating to look for an alternative to replace it with other waste materials with similar behavior, especially in these countries. It is known that bamboo leaf ash (BLAsh) is a pozzolan with high reactivity, possessing a high amount of amorphous silica. The paper presents a qualitative and quantitative characterization of the pozzolanic reactivity of bamboo leaf ash (BLAsh) and silica fume (SF). The pozzolanic activity is evaluated by using a conductometric method. In this method the electrical conductivity in a BLAsh/Ca(OH)2 and SF/Ca(OH)2 solution is measured with the reaction time. Latter, a kinetic-diffusive model is applied which allows computing the kinetic parameters of the pozzolanic reaction. The values of these parameters, specifically the reaction rate constant, characterize the reacting process and allow evaluating quantitatively the pozzolanic activity of these materials. The application of other experimental techniques employed in this research [X-ray diffraction (XRD) and scanning electron microscopy (SEM)], support the results coming from the conductometric method. The results show that BLAsh and SF are formed fundamentally by amorphous silica with a high pozzolanic activity. The comparison of BLAsh with SF allows concluding that both have a similar reactivity with reaction rate constant of 4.78 × 10−1 and 5.11 × 10−1 h−1 respectively. This fact reveals the importance of this agricultural residue for their use in the manufacture of blended cements.The authors thank CNPq (Process No. 313782/2013-0, Project PVE), CNPq (ref: 306386/2013-5). FAPESP (Process No. 2018/10719-6) for its financial support and the Collaboration Agreement between IETcc/CSIC (Spain) and FZEA/USP (Brazil) (ref: 2013040043).Peer reviewe