The characteristics of fresh and young concrete have a significant influence on both the mechanical and durability properties of hardened concrete. Fresh concrete refers to concrete that has just been cast while young concrete refers to concrete only a few days old. The characteristics to be investigated include: deformation, defects, rheology as well as mix design. Due to the wide scope of this field, the current focus is on the prevention of early age cracking of concrete, since the presence of these early cracks can have a major detrimental effect on the service life of any concrete structure. The research activities include research on plastic settlement cracking, plastic shrinkage cracking and thermal cracking of fresh and young concrete and are aimed at providing guidelines as well as the understanding needed for the prevention of early age cracking of fresh and young concrete.
Plastic Cracking of Concrete
Postdoctoral Fellow: Dr Muzafalu Kayondo
Supervisor: Prof WP Boshoff
The long-term performance of concrete structures is highly influenced by what happens to the concrete within its first few hours of being cast – while in its plastic state. The cracking of concrete during this fragile stage (plastic cracking) turns out to be an elusive subject matter among many concrete engineers and scientists. In this research, the fundamentals have largely been emphasized using new methods and approaches, and an extra step taken to clarify the elusive aspects of plastic cracking of concrete.
Rheology, Plastic Cracking and Viscoplastic Behaviour of Concrete
Student: John Kolawole (PhD)
Supervisors: Prof WP Boshoff & Dr R Combrinck
Concrete in its fresh state is susceptible to plastic settlement and plastic shrinkage cracking. For the first few hours after mixing, it also undergoes creep and relaxation. Rheology plays an important role in all of these. The goal of this study is to determine how rheology influences the plastic cracking behaviour of concrete.
Creep and Relaxation of Plastic Concrete
Student: Yaseen Khan (M.Eng)
Supervisor: Dr R Combrinck
The cracking of plastic concrete often occurs in large, flat concrete elements exposed to high evaporation rates. This includes both plastic settlement and plastic shrinkage cracking. These cracks are unsightly and result in premature durability issues in the concrete structure by acting as pathways for corrosive agents to enter the concrete. The creep and relaxation behaviour of plastic concrete greatly influence the cracking behaviour of plastic concrete. However, no research could be found in literature regarding this subject. This study entails the measurement and characterisation of the creep and relaxation behaviour of plastic concrete using a state-of-the-art tensile setup.