Pozzolanic activity of volcanic ashes produced by the eruption of the Tajogaite Volcano in La Palma, Canary Islands

It is estimated that the eruption of the Tajogaite volcano ejected more than 20 million cubic meters of tephra whose fragments of less than 2 mm are called volcanic ash. The presence of this volcanic ash throughout the island requires the search for solutions that allow a sustainable management of this material. This article studies the pozzolanic activity of volcanic ash from La Palma by determining the Strength Activity Index (SAI) in order to determine if its use as an additive in cement manufacturing is possible. The cement manufacturing process involves between 8% and 10% of CO2 emissions worldwide. The reduction of these emissions is possible by replacing part of the clinker with materials that have pozzolanic activity. In this work, the SAI values of 93 specimens made with volcanic ash are compared with the SAI values of 52 specimens made with silica sand that does not present pozzolanic activity. The application of the Mann-Whitney U test shows that the behaviour of volcanic ash from La Palma does not correspond with an inert material. The volcanic ash ejected by the La Palma volcano has pozzolanic activity with an average value of SAI at 28 days equal to a 77.5 ± 6.1% for a size of 45 μm and this value increases to 85.2±3.3% when the particle size is reduced to 23 μm. These results obtained from the pozzolanic activity of the volcanic ash from La Palma are equivalent to those of the fly ash that is currently used as an addition to clinker. •Volcanic ashes of the Tajogaite Volcano: an opportunity to reduce CO2 emissions.•Manufacture of cement using the volcanic ashes produced by the eruption in La Palma.•Sustainable reconstruction using the volcanic ashes of the Tajogaite Volcano.