Mineralogy and Microstructure of Hydrated Phases During the Pozzolanic Reaction in the Sanitary Ware Waste/Ca(OH)₂ System

Abstract

Despite technological improvements in its production process, the sanitary ware industry inevitably generates a certain volume of discards, products whose quality is not up to standard. The present paper is the first to scientifically explore clay‐based sanitary ware waste (SW) with a view to its valorization as an addition in the design of new, more environmentally friendly cements. The focus is on characterization of the waste and its pozzolanicity, as well as the structural and microstructural changes taking place in the pozzolan/Ca(OH)2 system in the first 90 d of reaction. The findings show that pozzolanicity in clay‐based waste is comparable to the activity observed in silica fume (SF) and higher than that found in other clay‐based materials and fly ash (FA). The microstructural study of the clay‐based waste/Ca(OH)2 system, in turn, reveals that the proportion of C–S–H gels rises with hydration time. These gels are characterized by long mean chain lengths (MCL) and low Ca/Si ratios. The intrinsic characteristics of this thermally activated clay‐based waste qualify it as a type Q pozzolans as defined in the European cement standards, making it apt for use in the manufacture of CEM II, IV, and V cements.

Long-term performance of novel high-calcium one-part alkali-activated cement developed from thermally activated lime kiln dust

“…16c. This illustrates the pozzolanic reaction of Si and Al with Ca +2 cations, which encourages further dissolution and breaking the Si-O and Al-O bonds in both MK and NP [77]. Ak products can be distinguished clearly as a predominant phase of flat continuous gels in all blends, but its lowest appearance can be seen in AAC11, which agrees with the XRD patterns.…”

Coal Mining Waste as a Future Eco-Efficient Supplementary Cementing Material: Scientific Aspects

“…The main difference between the two spectra was that the Q1 unit signal was much more intense in the OPC than in the 20% ACW cement paste, denoting a smaller proportion of end of chain units and hence a higher degree of polymerization in the latter. Other authors have reported similar results for the pozzolanic reaction in fired clay-based waste [34]. Furthermore, the amount, distribution and microstructural characteristics of the C-S-H gel formed have a significant effect on the mechanical strength of the cement.…”

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

“…Fired clay industry waste is one of the new pozzolans explored by researchers. A number of prior studies on this material showed that fired clay of different origins has very promising pozzolanic properties because when fired at temperatures of 600°C‐900°C and ground to cement fineness, initially inert clay minerals acquire substantial pozzolanicity . The evaporation of chemically combined water at such temperatures and the resulting breakdown of the crystalline network of clay constituents induces the formation of an amorphous or vitreous material.…”