The technology enables to reuse waste with at least 20% clay-based material to obtain cement.
An estimated 450 million tons of ceramic waste (tiles, bricks and bathroom building materials) are produced in Europe every year, mainly out of demolition materials from buildings treated in recycling facilities. Only 5% of those leftovers are recycled in Spain —a very low percentage compared to other countries: 90% in the Netherlands for example.
A team of scientists, led by researcher Mª Isabel Sánchez de Rojas, have developed a technology to reuse waste with at least 20% clay-based material. The final product, prepared in several stages, is a homogeneous ceramic material with a suitable granular structure, similar to cement. That material can be added to cement instead of the usual natural pozzolana and other recycled substances (silica fume and fly ash).
Cement is basically made out of clinker [limestone and baked clay] and gypsum, added as a hardening regulator so as it does not solidify immediately. Other materials such as silica fume, fly ash (both recycled waste) or natural pozzolana can be added to that basic mixture.
As Mª Isabel Sánchez de Rojas explains, ‘the most frequent added materials in Spain are silica fume and fly ash, but the first one is scarce. Fly ashes come from thermal power stations where other materials are burnt besides coal, which affects the characteristics and composition of the ashes and can alter their quality.’ On the other hand, natural pozzolanic ashes are found in natural deposits.
It is the first technology which enables to reuse ceramic waste adding it to cement
‘Many deposits of natural pozzolana can be found in Spain, such as materials of volcanic origin. Running them is easy but ruins the landscape. Current research is trying to find out alternatives to reduce the impact, recycling materials that used to be piled up in landfills at the end of their lifespan and had no further use.’
That nationally patented technology innovates doubly: even if the ceramic materials are reused, they can have other applications, such as recycled aggregate in concrete or roads, bases and subbases for roads or as filling and/or drainage material. Therefore, that it is the first technology which enables to reuse ceramic waste adding it to cement.
That method offers several advantages, among which we can highlight a lower clinker consumption (which reduces environmental impact when obtaining prime materials and releases less gases into the atmosphere) and a composition close to the industrial waste currently added to cement. The final cements, both Portland and white, fulfill the physical, chemical and mechanic requirements set out by cement standards.
Contact:
Marisa Carrascoso Arranz
Vicepresidencia Adjunta
de Transferencia del Conocimiento (CSIC)
Tel.: + 34 – 91 568 15 33