Enabling three dimensional printing of concrete by application of granular physics.

Digital fabrication of concrete structures has gained substantial research traction over the last decade, enabling efficient material use and can add more architectural freedom. Current research focuses on chemical and mineral admixtures, as well as manipulating the cement hydration reaction to control the yield stress evolution of time in the cement paste. This work calls for employing concrete, instead of just cement based materials, in order to decrease the cost of printing and to enable steel reinforcement in the different concrete elements. The main process control parameter in 3-D printing with concrete materials is the yield stress. The yield stress is the stress value above which the concrete behaves as a viscous fluid, and below which it responds as a (weak) elastic solid. 3-D printing depends strongly on the yield stress value and its evolution with time. The proposed research work focuses on frictional contact between the aggregates as a primary source of yield stress instead of the cement paste, and on how vibration can be used as a printing control parameter, as it has been demonstrated that vibration decreases the yield stress. Furthermore, reinforcing 3-D printed concrete structures is a challenging task and current strategies have many shortcomings. With the proposed paradigm of granular physics controlling concrete rheology, the idea is to use minimal vibration energy to insert the reinforcement shortly after printing without destroying the printed layers stability. The vision of the research team is to enable 3-D printing of reinforced concrete structures through control of vibration energy, based on the principle of granular physics. The proposed project is a first step in this grand scheme, investigating the response of concrete materials to different levels vibration, laying the basis for larger research proposals and activities. The proposed project will investigate in detail the change in concrete yield stress under different levels of vibration, the zone of action as a function of vibration energy, and building a prototype for a 3-D printer to evaluate printability of the material. Concrete parameters include the aggregate volume fraction, as this value needs to be between two critical values for the concept to work, the aggregate size, angularity, and the paste properties. The first three parameters are expected to influence vibration energy transmission and the value of the yield stress, while the latter controls the viscous damping of the applied energy. The vision of the research team, which starts with this proposed project, is strongly aligned with the Saudi Vision 2030 and its Housing Program, accelerating construction, reducing dependability on foreign labours and implementing modern building technologies in the life of Saudi residents. This project is expected to give KFUPM a leadership position in Saudi Arabia and in the world in developing and implementing this research over the upcoming years. The project team possesses significant experience in the area of the project. The project would be completed in 15 months at a cost of SR 240,000