Mechanical, Durability, and Microstructure Assessment of Wastepaper Fiber-Reinforced Concrete Containing Metakaolin.

This study evaluates the potential use of discarded plasterboard paper as fibers from buildings to reinforce concrete. Various concentrations of wastepaper fibers (0.5%, 1%, 1.5%, 2%, and 2.5% by weight of the binder) were investigated in this research. To mitigate the water absorption effect of the paper fibers, metakaolin was employed as a partial cement replacement. The results demonstrate that the inclusion of the wastepaper fiber enhances the mechanical and durability performance of the concrete. The optimal fiber proportion was identified as 1%, leading to a 29% increase in the compressive strength, a 38% increase in the splitting tensile strength, a 12% decrease in the water absorption, and a 23% decrease in the drying shrinkage with respect to the concrete containing 20% metakaolin. However, exceeding this optimal fiber content results in decreased mechanical and durability properties due to the fiber agglomeration and non-uniform fiber distribution within the concrete matrix. Based on the microstructural analysis, the improved performance of the concrete is ascribed to decreased porosity, more refined pore structure, and reduced propagation of microcracks within the concrete matrix in the presence of wastepaper fiber. According to the results, concrete containing 20% metakaolin and 1% wastepaper fiber exhibits durability and mechanical properties comparable to those of the traditional concrete. This finding highlights the significant promise of reducing dependency on conventional cement and incorporating suitable recycled materials, such as discarded plasterboard, and secondary by-products like metakaolin. Such a strategy encourages the preservation of resources, reduction in carbon dioxide emissions, and a decrease in the ecological footprint resulting from concrete production.

Phenol formaldehyde resin modified by cellulose and lignin nanomaterials: Review and recent progress.

In recent years, growing consideration of the concepts of ecological sustainability, environmentally friendly, recyclability, non-toxicity and biodegradability towards a green environment, have led scientists to focus on the utilization of natural fibers as green reinforcing agents for improving thermal, physical, and mechanical characteristics of composites. In this way, cellulose and lignin (nano) materials are receiving global attention due to their unique and potentially useful features, containing abundance, renewability, low cost, excellent physical-mechanical properties, environmental friendliness, and low weight. Therefore, this research, addressed a survey of the literature on extending the performance of phenol-formaldehyde (phenolic) composites reinforced by cellulose and lignin nano materials that were explored in the last decade. Physical, mechanical behavior and thermal stability of the phenolic composites were comprehensively examined. Indeed, different types of phenolic composites modified with nanocellulose and nanolignin have been made using various advanced synthesis processes. The results were unanimous and highlighted the remarkable effect of nanocellulose and nanolignin on improving the overall performance of the fabricated composites.

High performance curcumin subcritical water extraction from turmeric (Curcuma longa L.).

Curcumin is a hydrophobic polyphenolic compound derived from turmeric rhizome, which consists about 2-5% of the total rhizome content and is a more valuable component of turmeric. For reducing the drawbacks of conventional extraction (using organic solvents) of curcumin, the water as a clean solvent was used for extracting curcumin. Subcritical water extraction (SWE) experimental setup was fabricated in a laboratory scale and the influences of some parameters (e.g. extraction temperature, particle size, retention time and pressure) on the yield of extraction were investigated. Optimum extraction conditions such as SWE pressure of 10bar, extractive temperature of 140°C, particle size of 0.71mm and retention time of 14min were defined. The maximum amount of curcumin extracted at the optimum condition was 3.8wt%. The yield of curcumin extraction was more than 76wt% with regards to the maximum possible curcumin content of turmeric, as known to be 5%. The scanning electron microscope (SEM) images from the outer surface of turmeric, before and after extraction, clearly demonstrated the effect of each parameter; changes in porosity and hardness of turmeric that is directly related to the amount of extracted curcumin in process optimization of the extraction parameters.