Abstract
This study examines the effect of curd whey, introduced as part of the mixing liquid, on the shrinkage and water absorption of fired clay building ceramics. The ceramic body was prepared from a 50:50 mixture of low-firing clays from the Ivanovo and 24th Party Congress deposits (Akmola Region, Kazakhstan). Curd whey replaced 15% and 20% of the mixing liquid by volume, with a whey-free composition used as the reference. Specimens were shaped by plastic forming and fired at 850, 900, 950, 1000, 1050, and 1100 °C. Firing shrinkage, total shrinkage, and water absorption were determined on five specimens for each combination of composition and firing temperature; no values were recorded for seven combinations, which are identified in the text. The addition of 15% whey reduced firing shrinkage at every firing temperature at which it was measured: at 1050 °C, firing shrinkage was 0.9 ± 0.08% for the composition containing 15% whey against 1.6 ± 0.08% for the reference. Water absorption of the 15% whey composition remained higher than that of the reference at every firing temperature at which both were tested, reaching 7.9 ± 0.25% against 5.2 ± 0.20% at 1100 °C, whereas the 20% whey composition exceeded the reference at 950–1050 °C but not at 850 and 900 °C. These trends are consistent with the formation of additional porosity through decomposition of the organic constituents of the whey during firing; porosity, density, and microstructure were not measured directly in the present work, so this interpretation is presented as a proposed explanation. The results show that liquid curd whey can be used as part of the forming liquid to modify the shrinkage behavior of clay ceramics and provide a basis for the mechanical and microstructural characterization needed to establish practical performance.