Recently, the team led by Professor Xiao Jianzhuang, President of Guangxi University, has made important progress in the theoretical study of interfacial mechanics of recycled concrete. The related findings were published in the form of a Perspective in Science Bulletin and The Innovation Insights.

Since the advent of Portland cement, concrete has gradually become the cornerstone of modern civilization. At present, annual concrete consumption exceeds 30 billion tons, covering types such as natural aggregate concrete, recycled aggregate concrete, and ultra-high-performance concrete. For a long time, academia has tended to develop separate regulation theories, standards and specifications, and academic platforms for each type of concrete, which has to some extent led to insufficient resource integration and duplicated investment. Consequently, a fundamental question is worth considering: can a foundational theory applicable to all concrete be developed, abstracting concrete into a theoretical “unified concrete” model? When analyzing a specific type of concrete, one would only need to adjust the corresponding interfacial parameters under this unified model, supplemented by matrix and aggregate parameters when necessary, to predict its performance.

Focusing on this fundamental scientific question in the field of concrete, Professor Xiao Jianzhuang's team has carried out sustained scientific and technological research in recent years and has made progress. The team systematically reviewed the theoretical framework of "unified concrete" and distilled three fundamental problems that need to be solved in constructing the theory of interfacial mechanics for recycled concrete: anisotropy, time-varying characteristics, and scale characteristics. They also elucidated the intrinsic coupling relationships among the three, laying a framework for establishing a unified foundational theory of concrete.

Given the importance of the theory of interfacial mechanics for recycled concrete and the foundational significance of the MITZ, the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) established Technical Committee TC-MTZ, with Xiao Jianzhuang serving as Chair. The TC brings together experts and scholars from China, the United States, the United Kingdom, Japan, Australia, and other countries, as well as from Europe, the Middle East, and other regions. In 2025, the committee held its kick-off meeting in Hanoi, Vietnam, and its various activities are being carried out in an orderly manner.

In addition, Xiao Jianzhuang initiated and successively chaired two sessions of the "Symposium on Interfacial Mechanics of Concrete," bringing together more than 100 experts and scholars from home and abroad for exchange and discussion. The third symposium will be held at Tsinghua University in October 2026, and the fourth is planned to be held at Guangxi University in October 2027.

Fig. 1 Comparison of interfacial transition zones in recycled aggregate concrete and natural aggregate concrete

Fig. 2 Theoretical framework of interfacial mechanics for recycled concrete

Fig. 3 Kick-off meeting of RILEM TC-MTZ in Vietnam