Potential pathway for recycling of the paper mill sludge compost for brick making

This study's focus was to develop a potential pathway for recycling of the paper mill sludge compost (PMSC) in brick making. Composting reduces the paper mill sludge (PMS) moisture content considerably and shredding becomes easier. The addition of PMSC leads to an increase of porosities in bricks and makes them lighter, besides delivering energy to the firing process from burning organics. Lighter construction materials help minimize construction outlay by reducing labour and transportation costs and lesser expense on foundation construction. The variability in the experimental data and the brick properties were investigated for two types of soils, typical in the brick industry of India (alluvial and laterite soil), blended with PMSC in five mix ratios (0%, 5%, 10%, 15% and 20%). The samples of oven-dried bricks were fired at two different temperatures (850 and 900 ˚C) in an electrically operated muffle furnace representing typical conditions of a brick kiln. Various properties of bricks were analyzed which included linear shrinkage, bulk density, water absorption and compressive strength. Conclusions were drawn based on these properties. It was found that the addition of PMSC to the alluvial and laterite soil by up to 10% weight yield mechanical properties of fired bricks compliant with the relevant Indian and ASTM codes. Toxicity characteristic leaching procedure (TCLP) tests showed that PMSC incorporated fired bricks are safe to use in regular applications as non-load-bearing and infill walls. This study is timely in light of the European Green Deal putting focus on circular economy. Besides, it fulfils the objective of UN sustainable development goals (SDG)

Raw kaolinitic-illitic clays for the production of refractory ceramics

The study makes a unique effort to characterize all the necessary characteristics of refractory clays and products fired at temperatures between 1100 and 1300 °C on a laboratory level. For 19 composite samples from the recently opened reservoir, thorough instrumental and ceramic-technological data are presented. The potential for using Serbian raw refractory clays from the recently discovered deposit is investigated. The composites had a variety of qualities and varied in composition, but they were majorly composed of kaolinite and illite and had a significant share of fluxes. The samples had high quantities of clay minerals and organic matter, which is seen as the most intense mass loss in the 400–600 °C range. Low-duty and high-duty refractories could be distinguished by their refractoriness over 1581 °C. This parameter was mostly influenced by the content of alumina and kaolinite within the materials. Hydraulically-pressed ceramic tiles, following the firing stage, showed water absorption was between 9.02–1.42 % and a modulus of rupture of 16.5 – 53.6 MPa. Color is determined by spectrophotometer and correlated to the composition of the initial clay and fired products. For the lining of ceramic and glass furnaces, the majority of these clays can be used as natural refractory materials. Some of the samples' organic content has a detrimental effect on the fast-firing procedure, since the occurrence of the entrapped air (bloating)

Influence of coal ashes on fired clay brick quality: Random forest regression and artificial neural networks modeling

Finding a solution to the problem of the large buildup of coal ashes is a vital necessity. Although the use of coal ashes in fired clay bricks has been thoroughly investigated, there is insufficient information on their industrial utilization and researchers do not agree on whether or not this addition improves the quality of the final products. Therefore, a database has gathered 20 years of research containing key factors related to the quality of the bricks (i.e., chemical composition, firing temperature, soaking time, open porosity, water absorption and compressive strength). Then, random forest regression and artificial neural networks (ANN) modeling were used to separately predict the parameters concerning the quality of the final products. The overall conclusions were that the compressive strengths were the highest when using fly ashes and that class F ashes were highly suitable to be used in the brick industry as a replacement material for brick clay. In addition, the ANN models showed higher coefficients of determination and an overall better fit to the experimental data. By changing the chemical makeup of the initial materials and their proportions, the particle size of the ashes, the firing temperature and soaking time, as well as the size of a product, the created models can be used to estimate the quality of the brick containing coal ash. That is crucial because the inconsistent chemical composition of ash is generally the main obstacle to its utilization. The local sensitivity analysis revealed the highest influence of the content of the alkali oxides in the initial clay on the fired clay bricks due to their fluxing effect. In the case of ash-clay bricks, the decisive factors were the type of furnace used, the ashes' class, the Na2O content in raw clay, and the K2O introduced with the ash. The F class ashes containing about 2–3% of K2O and [removed