The present work focuses on investigating the characteristics of the fracture process zone (FPZ) in concrete. The Single-edge notched (SEN) concrete beams under three-points bending are employed for conducting mode I fracture propagation. The displacement fields on the specimen surface and the internal AE signal of specimen are obtained simultaneously in real time by digital image correlation (DIC) and acoustic emission (AE) techniques. The experimental and analytical results indicated that the crack tip position, the crack extension length and the stress intensity factors (SIF) are obtained dynamically and quantitatively by DIC technique, and the length of FPZ is identified, respectively, by DIC and AE techniques in the crack extension process. The distribution of internal AE events is consistent with that of FPZ identified from surface deformation of specimens.

A main challenge in the large-scale application of the microbially induced carbonate precipitation (MICP) technique includes the low efficiency of the cementation of coarse grains. Actually, in the MICP treatment process, the cementation effect of the bonding points was more important than pore filling due to the large porosity for coarse grains. To achieve a better cementation effect at bonding points between coarse particles, the quick formation and growth of a biofilm is necessary. In this study, an optimized medium was proposed to improve the cementation effects for coarse materials. The optimized medium and other different media were used for bio-cementation tests with MICP. The viable cell concentrations, strengths, microscopic characteristics, biofilm contents, and calcium carbonate (CaCO3) contents were used to evaluate the bio-cementation and its effects. In bio-cementation tests, the optimized medium led to increased CaCO3 precipitation at the bonding points and better cementation effects compared to other media. Indeed, the strength of the sample treated with the optimized medium was more than 1.2–4 times higher that of the values for other media. The advantages of the optimized medium were demonstrated via bio-cementation tests.

A method for determining mode I and mixed-mode I-II stress intensity factors of concrete material was developed in this research on the basis of the displacement fields obtained through a digital image correlation (DIC) approach. Single-edge notched (SEN) concrete beams subjected to three points bending and four points shearing exertions were implemented for conducting the experiments to evaluate the mode I and mixed-mode I-II fracture propagations. The dynamically varying displacement fields around the crack tip are determined by the DIC approach corresponding to the crack propagation. The instant positions of the crack tip and the corresponding stress intensity factors were determined with utilization of the displacement fields around the crack tip. The results of the research showed that the mode I and mixed-mode I-II stress intensity factors and crack tip positions of concrete materials can be accurately and effectively determined with the method developed. More significantly, the displacement field and the fracture parameters of the concert material can all be quantitatively determined for any instance corresponding to the processes of the crack propagations.