Use of ceramic industry milling and glazing waste as an active addition in cement

Abstract

The beneficial effects of pozzolans on cement manufacture have encouraged their use in that industry. Traditional natural pozzolan have become less available of late, however, due to a decline in quarrying intensity aimed at minimizing the impact on the landscape. At the same time, environmental policies pursue the reduction or elimination of spoil heaps by valorizing industrial waste and by-products as raw materials, in keeping with the principles of the circular economy.The quest for new types of waste and by-products with pozzolanic properties has consequently become a priority line of research. This study explored the valorization of one such by-product, the ceramic sludge resulting from fired clay industry milling and glazing, as a component in new, more eco-sustainable cements. The sludge was characterized physically, chemically, morphologically, and mineralogically to determine its suitability as a pozzolanic addition in cement. The findings showed that ceramic sludge consists in clustered particles ranging in size from 100 lm to 1 lm. SiO 2 , Al 2 O 3 , and Fe 2 O 3 together comprise over 70% of the total composition, while the reactive silica content is greater than the 25% required by the existing legislation. The predominant minerals are quartz, kaolinite, and muscovite, with some zircon. A study of pozzolanic reaction kinetics in the ceramic sludge/lime system revealed that over time this waste can fix lime, generating products such as calcium aluminate hydrates and C-S-H gels. The cements made with ceramic sludge proved to be standard-compliant in terms of water demand, setting, drying shrinkage and mechanical strength. K E Y W O R D S cements, ceramic waste, pozzolanic activity, supplementary cementitious materials

Durability and chromatic behavior in cement pastes containing ceramic industry milling and glazing by‐products

“…The Si replacement by Al in the gel led to lower Ca/Si ratios (1.72). The foregoing was consistent with premises set out by other authors as well as with earlier results for the CS/Ca(OH) 2 system and cements containing granite sludge, in which the addition of pozzolans led to lower Ca/Si ratios than found in OPC.…”

“…X‐ray diffraction analyses conducted in an earlier study showed the main crystalline phases in the CS to be: quartz, kaolinite, muscovite, illite, hematite, magnetite, calcite, dolomite, albite, and zircon (zirconium silicate).…”

“…Further to the data given in Table , the sludge had high silica, aluminum oxide, and iron oxide contents, together amounting to over 70 wt%. As reactive silica accounted for 33.10 wt%, the waste met the EN 197‐1 2 requirement for pozzolanicity …”

“…Monocarbonate, portlandite, calcite, and anhydrous larnite were also observed in the CS‐PC specimens, along with the zircon and quartz present in the CS as discussed earlier. The intensity of the portlandite reflections declined as a result not only of lower cement content, but also of the pozzolanic reaction induced by the CS …”

“…This study assessed the effect of ceramic industry milling and glazing sludge on durability. This type of waste, managed by a company in Spain, was shown in earlier research to exhibit pozzolanicity and have a beneficial impact on the properties of the cements to which it is added . The use of similar waste in new cement manufacture has been studied by other authors as well …”