Complete recycle of concrete wastes combined with steel making process
Research outline
This module aims to achieve the complete recycling of concrete waste by proposing and developing two key technologies: a simple upcycling process for recycled aggregates that avoids complex steps; and a technology that converts concrete fines into slag using steel making blast furnace technology.
Reusing the concrete fines directly contributes to reducing the amount of cement used in concrete and the associated CO2 emissions, and this module achieve this by melting concrete fines and forming slag through the blast furnace technology; this process also leads to a reduction in limestone consumption and associated CO2 emissions within existing blast furnace operations.
Currently there are concerns regarding the future supply of materials used in concrete, such as fine aggregates (sand) and admixtures (blast furnace slag, fly ash etc.). This research also contributes to ensuring a stable supply of these materials in the future.
Research backgoround
Although it is considered that the technologies are well developed to reuse the crushed stone and aggregates derived from waste concretes, applications remain largely limited to “downcycling” as roadbed material. “Upcycling” them into new concrete as recycled aggregate is still considered difficult. Even regarding their use as road base material, issues of the market saturation and surplus stockpiles are emerging. Meanwhile, concrete fines separated from aggregates are generally discarded, as their reuse in new concrete is considered difficult on a global scale.
Research originality
Although methodology aimed at improving the surface conditions of crushed stone and aggregates derived from waste concrete have been proposed in academic literatures, they often involve complex processes, and thus, have not been implemented in practice. This project aims to upcycle these materials into new concrete as recycled aggregates using a very simple treatment method. On the other hand, concrete fines separated from the aggregates are difficult to use directly, due to their physical shape and characteristics, but these issues can be resolved, as we propose, by melting the material and converting it into slag.
Module members
KINOSHITA Hajime
Professor
Faculty of Engineering
Project management, Aqueous treatment of recovered aggregates
OHNO Koichiro
Professor
Faculty of Engineering
Application of concrete fines for steel making process and slag formation
SAITO Noritaka
Professor
Faculty of Engineering
High temperature melting treatment of concrete fines
FUKUNAGA Takayuki
Assistant Professor
Faculty of Engineering
Application of slag made from concrete fines
Expected results and outcomes of the collaboration
Sustainable technology development is becoming an essential element across various industries. The cement and concrete industry is known for significant CO2 emissions, and consequently, reducing cement consumption through the reuse of concrete fines can directly contribute to lowering CO2 emissions. This project aims to utilise blast furnace technology used in steelmaking, which would also lead to a reduction in limestone consumption and associated CO2 emissions within current blast furnace operations.