Conference Agenda

The water-to-binder (w/b) ratio is the prime factor governing the degree of hydration and composition of hydration products in cementitious composites. The hydrated phase composition consequently governs the performance of composites under different mechanical and environmental loadings. In this study, the effects of w/b ratios on the self-healing characteristics (under wetting-drying cycles) of carbonated reactive magnesia cement (RMC) based composites were investigated. This investigation focuses on the study of healed products and corresponding microstructure evolution. The study was conducted on RMC-based composites with w/b ratios of 0.30 and 0.40. The behavior was characterized on 7-day and 90-day matured composites to understand the effects on early-age crack mitigation and long-term performance simultaneously. The self-healing efficiency was characterized using crack width closure. The chemical characterization of the healing products was done using XRD and TGA analysis, and the morphology of the healing products was studied using SEM and EDS. The results demonstrate almost 100% crack closure in composites with a low w/b ratio than 80-90% crack closure at a high w/b ratio. The main healing product in low w/b RMC composite was amorphous magnesium-silicate-hydrate (MSH), whereas hydrated magnesium carbonates (HMCs) were observed in 0.40 w/b ratio RMC composite due to the increased porosity. The composition of healing products was different at the surface and core region of the healed matrix. The results will enable the tailoring of RMC-based composites to have desirable self-healing attributes.

The mechanical performance of fiber-reinforced cementitious composites (FRCCs) significantly depends on the strength of the interface bond between the fibers and the cement matrix. An important aspect that can affect the properties of the fiber-matrix interface is interfacial healing – a process wherein the interface undergoes repair after being damaged. In this study, we investigate the interfacial healing efficiency of mechanically preloaded and then environmentally conditioned specimens using the single-fiber pullout test. In the experimental setup, single-fiber specimens were subjected to preloading to induce damage, followed by environmental conditioning to promote interfacial healing. The effectiveness of the healing process was assessed by performing the single-fiber pullout test on the healed specimens. For comparison, specimens that were not preloaded but subjected to identical environmental conditions were also evaluated. The bond strength and interface bond recovery of the specimens were quantitatively assessed.

An experimental study is carried out to investigate the structural behaviour and durability performance of hybrid reinforced concrete beams with U-shaped covers made via mould-casting method and 3D printing method. Structural behaviour, surface crack pattern and crack propagation between the reinforced concrete core and U-shaped SHCC cover are studied. A qualitative assessment of the crack appearance before and after healing was also performed. Findings reveal that mould-casted SH-SHCC covers enhance crack control without compromising beam properties, offering comparable or improved load capacity and ductility under shear and flexure. Although 3D-printed covers are slightly less effective in crack control, they still improve overall performance and offer advantages in manufacturing efficiency. Both cover types effectively prevent delamination and disperse major cracks into finer, healable cracks, facilitating crack healing observed after one-month moist curing.

Filler into concrete cracks is one of the repair methods for in-service concrete structures. Applying epoxy-based filler to the structures combines concrete material with epoxy resin and protects re-degradation. However, the insufficient filling of the filler into cracks can reduce the repair effectiveness. By the authors, epoxy-based filler mixed with hollow particles has been developed for improving mechanical properties of the repaired concrete and inspecting the insufficient filling well. In particular, this study focuses on non-destructive detection of the insufficient filling of the mixed filler into an artificial concrete crack using active infrared thermography. In lab experiment, we performed active infrared thermography with 20-minute heating and 40-minute cooling for four concrete samples. The concrete samples had an artificial crack that was filled with epoxy-based filler mixed with hollow particles. Each filling proportion into the crack was set to 20%, 50%, 80%, and 100%. The volume ratio of the epoxy resin to the hollow particles in the filler was 2 to 1. In analysis, we analyze the surface temperature fields of the samples using thermal images and the inner temperature fields using a two-dimensional heat conduction simulation. As a result, in the 20%-filling sample, which has the smallest filling proportion, the standard deviations of the filler temperatures during first 60 seconds of the cooling are largest in the samples. Additionally, in the same sample, changes of the heat flux in the depth direction around the surface, which is determined by the simulation, are also largest. The characteristics of the temperature variation and heat conduction probably depend on the hollow particles. The filler mixed with the hollow particles enables us to detect the filling into the crack accurately, quickly, and remotely. Thus, this study provides the non-destructive method for monitoring the repair using the hollow particle mixed filler.

Wollastonite, a low-lime calcium silicate offers low carbon emissions and forms stable calcium carbonates under carbonation. This study explores the integration of Wollastonite and Portland cement in a blended system designed for carbonation curing. While traditional accelerated carbonation curing improves surface hardness in ordinary Portland cement (OPC), its effectiveness is limited in deeper regions due to restricted CO2 diffusion, which hinders both mechanical enhancement and CO₂ sequestration. To address this, a novel approach utilizing embedded 3D-printed vascular networks is introduced, facilitating deeper CO₂ penetration and a higher overall carbonation degree. The vascular channels, with diameters of 300, 500, 700, and 900 μm, were evaluated for their impact on the morphology and composition of the channel walls post-carbonation. Additionally, the compressive strength of 500 μm cubic samples oriented radially from the channels was assessed. The results provide valuable insights for optimizing vascular network designs in carbonation-hardened cementitious materials.