Concrete is not only the most important building material of the last century, but also the most important building material of this century, with a very large application. After 2012, the amount of concrete used has exceeded 6 billion tons. With the diversified development of building structures, the application environment of concrete is becoming increasingly complex and harsh, which requires higher performance of concrete.

As an important component of concrete, sand and gravel aggregates have a significant impact on the performance of concrete. In people's traditional understanding of sand and gravel, there is a bias that sand and gravel only play a filling role in concrete and their quality is insignificant, as long as more cement is added. In fact, the role of sand and gravel aggregates in concrete is very important. They play a skeleton role, transmit stress, and even without cement slurry, the aggregates can support the load while suppressing shrinkage and preventing cracking.

Since the 1990s, the development trend of concrete has been towards high-performance concrete, with aggregates gradually being used as the main structural material, and the less cement used, the better. The development of high-performance concrete requires high-quality sand and gravel aggregates. Experts in the field of concrete in China regard the quality of sand and gravel aggregates as a bottleneck that restricts the development of concrete in our country.

With the increasing shortage of natural sand and gravel resources and the increasing requirements of the state for environmental protection, artificial sand and gravel have developed rapidly in China in recent years. Professor Jiang Zhengwu from the School of Materials Science and Engineering at Tongji University believes that machine-made sand has unparalleled advantages over natural sand and gravel. In the context of a shortage of natural sand and gravel, he believes that the time has come for the development of aggregates to shift from natural aggregates to artificial aggregates.

He stated that the biggest advantage of machine-made sand is its controllable and adjustable quality, which can be optimized through reasonable production processes to produce machine-made sand that meets the needs of different levels. Taking high-quality machine-made sand as an example, different types of high-quality concrete can be prepared, which can achieve C100 in the laboratory, while ordinary limestone is difficult to achieve such high strength.

Professor Jiang Zhengwu believes that the first step in producing high-quality machine-made sand is material selection. The source materials must meet the standards in order to control the quality. Secondly, the indicator characteristics of the spherical shape of machine-made sand indicate that high-quality machine-made sand should be closer to river sand. Finally, control the mud content. If the mud content is controlled, the content of stone powder can actually be appropriately relaxed.

From an industry perspective, Professor Jiang believes that the future trend of mechanism sand is to replace river sand and gravel, which is an inevitable trend. The management technology and capital advantages of aggregates will dominate the industry. The industry standards for mechanism sand should be further refined to guide the development of future technologies.

Professor Jiang Zhengwu said that from the perspective of the entire industry chain, what is the demand for concrete, what performance concrete is needed, and in turn, what quality of mechanism sand should be produced. In the current situation where the requirements for sand and gravel aggregates in concrete are constantly increasing, enterprises should provide high-quality machine-made sand as much as possible, so that the government can feel that high-quality machine-made sand can be produced, rather than blindly believing that all machine-made sand is inferior. In this way, he believes that the government can establish reasonable regulatory guidance mechanisms for the sand market, ultimately achieving a win-win situation for all parties and ensuring the sustainable development of the sand, gravel, and concrete industries.