Process Design for a Production of Sustainable Materials from Post-Production Clay

Abstract

Alkali activated cement (AAC) can be manufactured from industrial by-products to achieve goals of “zero-waste” production. We discuss in detail the AAC production process from (waste) post-production clay, which serves as the calcium-rich material. The effect of different parameters on the changes in properties of the final product, including morphology, phase formation, compressive strength, resistance to the high temperature, and long-term curing is presented. The drying and grinding of clay are required, even if both processes are energy-intensive; the reduction of particle size and the increase of specific surface area is crucial. Furthermore, calcination at 750 °C ensure approximately 20% higher compressive strength of final AAC in comparison to calcination performed at 700 °C. It resulted from the different ratio of phases: Calcite, mullite, quartz, gehlenite, and wollastonite in the final AAC. The type of activators (NaOH, NaOH:KOH mixtures, KOH) affected AAC mechanical properties, significantly. Sodium activators enabled obtaining higher values of strength. However, if KOH is required, the supplementation of initial materials with fly ash or metakaolin could improve the mechanical properties and durability of AAC, even c.a. 28%. The presented results confirm the possibility of recycling post-production clay from the Raciszyn II Jurassic limestone deposit.

Hybrid Materials Based on Fly Ash, Metakaolin, and Cement for 3D Printing

“…In earlier studies, we showed the beneficial effect of grinding the raw materials, even if the process is energy-intensive; the reduction of particle size and the increase of specific surface area were crucial to obtaining the higher reaction rate of the precursor, more reacted final material and the proper mechanical properties of the geopolymer products [80]. The size reduction throughout the milling process is recognized as a mechanical activation of the material, resulting in an increase in compressive strength [75,79].…”

“…On the other hand, the crystalline quartz phase, due to the aluminosilicate compounds, can improve the physical and mechanical properties of geopolymers [99]. The kaolinite in MK may demonstrate an incomplete calcination process, which is dependent on the temperature treatment [80,100,101]. The asymmetrical hump appearing clearly in the range of 20-30 • (2θ) is commonly identified in MKs and indicates an amorphous phase related to aluminosilicate glass (Figure S4 in the Supplementary Materials) [85,102].…”

“…(2) the formulation of aggregates [75][76][77][78]80]; and (3) specific modifications, including reinforcing additives [59,121], agents controlling the geopolymer macrostructure [58,59], and curing conditions.…”

Eco-Geopolymers: Physico-Mechanical Features, Radiation Absorption Properties, and Mathematical Model

“…Therefore, the final geopolymer properties may be the complementary result of both factors-the total content of Si and Al components but also the modifying effect of CaO [21]. FFAs can be classified as; (i) silica-aluminum, (ii) alumina-silica, (iii) calcium sulphate, and (iv) calcium types [43,44]. According to the results, both FFAs can be defined as an alumina-silica type.…”

“…Generally, the raw material reactivity was controlled by numerous intrinsic (e.g., the mineralogical, chemical, structural composition, amount of reactive fraction of SiO 2 and Al 2 O 3 ) and extrinsic parameters (e.g., FA fineness level, type and proportion of raw materials, the ratio of activators, duration and temperature of the process) (Figure 1, Tables 2, 3 and 5), which consequently affected GPBM mechanical properties and homogeneity (Table 5). It is well known that a greater fineness level of the FFA increases paste workability and the rate of geopolymerization, shortens setting time, and improves physical (density), mechanical (compressive and flexural strength), and microstructural (compact and uniform matrix) properties of the geopolymer [21,44]. The mechanism of improving the physical and mechanical properties of GPBM is also attributed to a higher amount of alkaline aluminosilicate gel [21,[49][50][51][52].…”