Engineering topics
Yu, Hua
Publications and source records attributed to Yu, Hua.
Characterization of coal extracts and their performances as binder for new carbon-based structural units
Coal production and usage have been declining in the past decade due to the transition to renewable energies, environmental regulations to reduce environmental pollution due to direct coal combustion from coal-fired power stations, and administrative policies. This downturn has created tremendous challenges for the coal industry, and many states rely on revenue from coal mining. Developing new valorization routes with high coal demand is essential and using coal-derived materials to make engineered products does offer an eco-friendly, attractive, and value-added use. This paper presents a brief introduction to the extraction process to derive coal deposits, extracts, and residuals (CDERs) and a comprehensive characterization analysis to determine the suitability of CDERs as binders to produce an innovative construction material named the carbon-based structural unit (CSU). CDERs are used to prepare the CSU with or without using mesophase pitch (MP) as binders and selected CDERs are heat-treated and pressure-heat-treated to improve their binding capabilities. The performances of the CSU specimens are evaluated based on compressive strength, density, and thermal conductivity. The CSU specimens mixed with distilled residue (DR) to pyrolysis char (PC) ratio of 1:2 achieve a compressive strength of 54.85 MPa, which is higher than the compressive strength of 30 MPa of normal concrete. The CSU specimens with deposit (De) and tetralin insoluble (TI) require the addition of MP to obtain compressive strengths greater than 30 MPa. Furthermore, these CSU specimens possess a relatively low density of about 1 g/cm 3 and low thermal conductivity of less than 0.25 W/m.K.
Eco-Friendly High-Performance Carbon Building Material Development from Coal
The development of eco-friendly high-performance building materials based on coal-derived materials is greatly beneficial for promoting environmental sustainability and the coal industry. This project focused on advancing technology to create innovative and scalable construction materials from two domestic sources: (1) coal-derived pyrolyzed char (PC), and (2) solvent-extracted coal deposit, extracts, and residue (CDER). It aimed to simultaneously develop and produce two types of coal-derived building products: (1) char-based concrete bricks (CCB) for wall construction in buildings, and (2) carbon-based structural units (CSU) intended as alternatives to traditional wood, concrete, or steel framing structures. The project team has successfully developed methods for manufacturing CCB samples. Extensive experiments were conducted to assess various manufacturing techniques for these samples. This included measuring their physical properties such as thermal conductivity (ranging from 0.26 to 0.38 W/mK) and bulk density (ranging from 0.85 to 1.15 g/cm 3 ), along with their mechanical properties (e.g., compressive strength ranging from 14 to 16 MPa at 28 days) for samples with a PC composition of 70%. Quality assurance and quality control tests, focusing on density and compressive strength, were also performed on samples selected randomly from pilot-scale production, and cured for a long term (over three months). The average long-term compressive strength of two randomly selected CCB samples was measured as 15.1 MPa, which was higher than the required target strength of 14 MPa. This indicates that the manufactured CCB samples from the preliminary pilot scale production run have good quality control and long-term strength performance.
New coal char-based bricks: Effects of curing temperature, humidity, pressing pressure, and addition of superplasticizer on the physical, mechanical, and thermal properties
Coal char, as a sustainable and eco-friendly material, holds significant potential for use in new construction materials, specifically, coal char-based bricks. This study employed the pre-pressing method to create char bricks containing high char content of 70%. The impact of various curing temperatures (20, 40, 60 °C), humidity levels (15% and 90%), and pressing pressures (3.5, 7, and 10 MPa) on the density, X-ray diffraction, compressive strength, and thermal conductivity of char-based samples were examined. The addition of superplasticizer and the performance of char bricks were assessed by comparing them to traditional clay bricks and corresponding standards. The study discovers that the temperature of 40 °C enhances the early 7-day strength of char brick samples, while the highest 28-day strength is observed in char bricks at a temperature of 20 °C and humidity of 90%. Compared to conventional clay bricks (with density of 1.9 g/cm3, thermal conductivity of 0.39-0.63 W/mK, compressive strength of 10-20 MPa), the proposed char bricks exhibit lower density (~0.8 g/cm 3 ), lower thermal conductivity (0.26-0.35 W/mK), and good performance in compressive strength (up to 15 MPa). Lastly, coal char-based bricks with high char content demonstrate significant advantages over traditional clay bricks, making them a sustainable and environmentally friendly building material option.