For the first time, the constitutive relation of magnesium phosphate cement is proposed successfully by Dr. Zigeng Wang and his team

Significance 

Recent advancement in construction and related industries have led to the development of magnesium phosphate cement for repair and strengthening applications. It comprises of magnesium potassium phosphate hexahydrate and magnesium oxide components. Although not common as other concrete materials, its use has recently attracted significant attention of researchers due to its excellent properties such as high bonding strength. However, the focus is mainly on its properties, mechanisms and performance.

Presently, several methods have been developed to investigate the performance of cement-based materials. For instance, many studies have emphasized the influence of various parameters such as molar ratio and water-to-cement ratio on the mechanical properties like compressive strength and water resistance. Even though these works have resulted in remarkable achievement that have henceforth improved properties of magnesium phosphate cement materials, limited work have been conducted on the strength formation mechanism. To this end, researchers and scientists have been looking for an alternative and have identified nanoindentation technology and X-ray computed tomography technology for investigating the performance of cement-based materials, as a promising solution.

In a recent research work published in the research journal, Construction and Building Materials, Prof. Yue Li, Dr. Guosheng Zhang, Prof. Zigeng Wang (as the corresponding author) and Dr. Zhongzheng Guan at Beijing University of Technology developed an experimental-computational approach for investigating the compressive strength of magnesium phosphate cement. The authors used a combination of nanoindentation and finite element analysis. They wanted to overcome the challenges associated with the previously used methods.

Briefly, the authors commenced their experimental work by using the homogenization method to determine the microscopic elastic moduli of the magnesium phosphate cement components. Consequently, several techniques such as nanoindentation, press and X-ray diffraction were used to test the various material parameters. Furthermore, three-dimensional structure to be used for finite element analysis was obtained by scanning the magnesium phosphate cement by X-ray computed tomography. Eventually, the homogenization results were used to calibrate the input parameters and thereafter the experimental results compared with the simulated load-displacement results.

From the experimental results, the authors observed that the AVIZO software was suitable for efficiently processing the computed tomography data of the magnesium phosphate cement. Thus, an accurate internal meshing structure was obtained as well. On the other hand, through homogenization method, it was possible to calculate the elastic moduli of the cement components. Most importantly, the proposed accurate constitutive relations of the magnesium oxide and magnesium potassium phosphate hexahydrate precisely calibrated input parameters and compressive test simulations.

The authors preeminently developed an experimental-computational approach for investigating the compressive strength of magnesium phosphate cement thereby overcoming the drawback of the previously used methods as a significant progress and breakthrough in the research history of civil engineering and materials. Owing to the agreement of the experimental and simulation results, the study will advance the development of high-performance magnesium phosphate cement with the desired properties suitable for various applications. Also, it forms the basis for future research work for improved properties.

About the author

Dr. Zigeng Wang obtained his Ph.D. in 2016 Michigan Technological University with Wilbur Haas Graduate Research Excellence Award. Afterward, he joined Beijing University of Technology as an assistant professor. In his research career, he has completed research projects on a wide range of subjects including Portland cement and concrete, magnesium phosphate cement, asphalt materials, building structure and construction technology, finite element analysis, discrete element method, computational fluid dynamics, imaging process, molecular dynamics simulation. Dr. Wang’s contribution to concrete materials and structures has been featured in newspapers, magazines, and other media. He has been presiding and participating many research projects such as National Key Technologies R&D Program of China, National Natural Science Foundation of China, Beijing Natural Science Foundation.

He has published over 30 papers in peer reviewed journals and conference proceedings. These publications include prestigious journals such as Construction and building Materials, ASCE Journal of Materials in Civil Engineering, KSCE Journal of Civil Engineering. In addition, he has also delivered over 20 presentations worldwide. Dr. Wang has been an effective teacher with his unique teaching philosophy. His teaching interests include transportation materials, concrete structure design, asphalt pavement engineering, materials mechanics.

Reference

Li, Y., Zhang, G., Wang, Z., & Guan, Z. (2018). Experimental-computational approach to investigate compressive strength of magnesium phosphate cement with nanoindentation and finite element analysis. Construction and Building Materials, 190, 414-426.

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