The aim of this study is to assess the process of synthesizing potassium-based geopolymers (KGL) into leucite ceramics with regard to five variables, namely, alkaline solution ratio (R), sintering time (S), calcining temperature (T), mixing time (M), and curing time (C). Under these conditions, the specimens were tested by the viscosity test, the mechanical properties test, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) to understand the geopolymerization reactions and the characteristics of the KGL network. The results indicate that a KOH to K₂O/SiO₂ ratio of 1:1 promotes the reaction within metakaolin. XRD analysis of the KGL shows that, when the temperature is 1100 °C, the phase transforms into the leucite phase. Moreover, XRD analysis, mechanical properties, and FTIR all indicate improved characteristics when the curing time increases from 1 to 8 h. This might be attributed to the enhancement of the strong interaction between the matrix and the alkaline solution upon achieving adequate time to complete the geopolymerization process and forming a more stable three-dimensional structure. The formulation which formed the purest leucite phase consisted of: a 1:1 alkaline solution ratio, 10 min mixing time, 8 h curing time, 1200 °C calcining temperature, and 2 h sintering time.

In this study, the feasibility of producing eco-friendly bricks by using geopolymer technology and a waste grinding wheel (WGW) from the grinding wheel industries was investigated. Nowadays, in order to meet industrial needs, for instance, in Taiwan, approximately 500,000 grinding wheels are used annually. That is, a large number of “waste” grinding wheels are produced. Furthermore, few studies have been conducted on the use of WGWs as raw materials in geopolymer applications. The use of geopolymer technology to form bricks can avoid the utilization of clay and cement and even prevent the use of a high-temperature process in kilns. Moreover, it can decrease CO2 emission and energy consumption and thus, protect the environment. In this study, the following three major factors were considered: press-forming pressure (70 and 100 kgf/cm2 ), NaOH molar concentration (2 and 4M), and the ratio of binder fineaggregate (1:3, 1:4, and 1:5). Under these conditions, the specimens were tested using the compressive strength test, water absorption test, microstructure analysis, a freezing–thawing test and toxicity characteristic leaching procedure test. The optimal formulation was composed of 1:4 binder fine-aggregate ratio, 4M NaOH concentration, and 100-kgf/cm2 pressure. Furthermore, we used a WGW and achieved a compressive strength of 50.6 MPa after 28 days, which was greater than 32 MPa and conformed to the Grade A brick standard of National Standards of the Republic of China (13295). In conclusion, this brick fabrication method based on geopolymer technology was not only beneficial to the environment but also improved the efficiency of reutilizing WGW.

This study explores the practicability of using drill cutting (DC) as raw material to fabricate building bricks through the high-temperature sintering method and low-temperature geopolymeric setting (LTGS) process. Drilling mud can be recycled and reutilized after certain treatment procedures and is considered as a non-hazardous waste. However, the treatment process is time-consuming and not cost-effective. For the sintering method, low porosity and high mechanical strength bricks can be sintered at temperatures above 800 °C and meet CNS standards. For the low-temperature geopolymeric setting process, sodium silicate was selected as an activating agent for geopolymerization of drill cutting. Several process parameters, such as Si₂O/Na₂O modulus of alkali solution and low-temperature geopolymeric setting temperature, were investigated. The physical and mechanical properties of the fabricated brick were evaluated. According to the test results, 72.4 MPa compressive strength building bricks with low porosity (13.9%) and water absorption (6.0%) can be fabricated with 2.0 Si₂O/Na₂O alkali solution at 500 °C. The drill cutting brick fabricated not only meets the CNS 382.R2002 common brick standard, but also solve its disposal problem.