The interface between filler and hydration products can have a significant effect on the mechanical properties of the cement paste system. With different adhesion properties between filler and hydration products, the effect of microstructural features (size, shape, surface roughness), particle distribution and area fraction of filler on the fracture behavior of a blended cement paste system is supposed to be different, as well. In order to understand the effect of the microstructural features, particle distribution and area fraction of filler on the fracture behavior of a blended cement paste system with either strong or weak filler-matrix interface, microscale simulations with a lattice model are carried out. The results show that the strength of the filler-matrix interface plays a more important role than the microstructural features, particle distribution and area fraction of filler in the crack propagation and the strength of blended cement paste. The knowledge acquired here provides a clue, or direction, for improving the performance of existing fillers. To improve the performance of fillers in cement paste in terms of strength, priority should be given to improving the bond strength between filler particles and matrix, not to modifying the microstructural features (i.e., shape and surface roughness) of the filler.@en

Self-healing concrete can repair itself by closing micro-cracks and thus protect itself from ingress of deleterious gasses and liquids that can affect its durability. Many self-healing concepts have been developed in the recent years which target on the recovery of water tightness after cracking. Among those systems, the bio-based healing agents have shown promising results regarding the crack sealing performance. This paper studies the crack sealing efficiency of bio-based healing mortar with expanded clay particles. The investigation of sealing performance is conducted through experimental and computational approaches. Image processing and crack permeability test results are compared with results obtained by computer simulations. The study reveals that the experimental approaches might overestimate the crack closure percentage, while the computer simulation mostly underestimates the crack sealing. Finally, recommendations are given to improve the results obtained by both methodologies.

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In the three-span concrete cable-stayed bridge, de-icing salt spraying during winter will cause chloride attack on the concrete components, posing significant risk on the corrosion of the reinforcing bars. In order to study the durability performance of this bridge, a numerical simulation based study is proposed. Since different concrete strength grades are adopted for the bridge girder and pylon, different material parameters are input in the numerical simulation process, which describes the chloride diffusion and binding effects. At the same time, due to the complicated cross sections of the girder and pylon, situations with different corner angles are calculated to take the two-dimensional features of the cross sections into consideration. Based on the numerical chloride ingress calculation, three diffusion states of reinforcement corrosion are determined as the criterions. Locations of the reinforcement bars are indicated in the two-dimensional illustration of the three criterions. The most unfavorable sections are selected for the girder and pylon, the corrosion initiation times of which are calculated on the base of the life-cycle analysis. The results indicate that corresponding maintenance strategies are needed for the most unfavorable pylon section at the completion of the bridge, and for the most unfavorable girder section at 40 years of service.@en