Conference Agenda

This study aims at investigating the influence of fibers on the punching shear capacity of plain ECC slabs. An experimental investigation was conducted on the punching shear resistance of plain ECC slabs with varying fiber volume fractions (FVFs). A total of sixteen plain ECC slabs were cast and tested, each with dimensions of 300 mm in side length and 40 mm in thickness. All slabs were simply supported on a bespoke steel framework with eight supports and concentrically loaded through a circular steel column stub with dimensions of 66 mm in diameter and 30 mm in height. The experimental results revealed that the plain ECC slabs with FVFs of 1.0%, 1.5% and 2.0% were characterized by punching shear failure, while slabs featuring 0.5% FVF were governed by flexural failure. It can be concluded that increasing FVF enhances the flexural capacity of plain ECC slabs more significantly than their punching shear capacity. Moreover, increasing the fiber volume fraction resulted in an increase in both crack resistance and ultimate load-carrying capacity. Notably, the punching shear capacity of plain ECC slabs increased almost linearly with increasing fiber volume fractions.

Seawater sea-sand concrete reinforced with non-corrosive reinforcements is attractive for marine infrastructures, while self-healing of cracks can enhance the longevity of concrete structures under harsh marine environments. However, current knowledge on the self-healing properties of Seawater Sea-sand Strain-Hardening Cementitious Composites (SS-SHCC) remains limited. This study aims to address this gap by investigating the self-healing mechanism and multi-scale healing performance of SS-SHCC. Firstly, the self-healing mechanism of SS-SHCC was explored at a single crack level. The effects of binder composition, initial crack width, and exposed conditions (involving seawater wet-dry cycling and immersion) on the self-healing behavior of the matrix were explored. Crack width was monitored throughout the healing period, and the self-healing products were characterized using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Subsequently, the multi-scale self-healing performance of the SS-SHCC was evaluated across four simulated marine environments. Surface crack healing and resonant frequency measurements were assessed during self-healing, while permeability and mechanical performance tests were conducted after self-healing. The findings revealed that the primary self-healing products in marine environments consisted of portlandite, brucite, aragonite, and calcite. The self-healing performance was primarily governed by the availability of Ca²⁺ and OH⁻ ions precipitating from the matrix. The presence of seawater in marine environments is pivotal for the self-healing efficacy of SS-SHCC, and the self-healing of SS-SHCC in the air zone was less pronounced. With the exception of the air zone, SS-SHCC's normalized resonant frequency recovered to more than 75% of its initial value, while permeability stayed below 1×10-10 m/s, preserving outstanding mechanical properties. These findings provide valuable insights for the design and application of SS-SHCC, contributing to enhanced durability and longevity of marine infrastructures.

It is crucial to investigate the cyclic compression performance of low-carbon engineered cementitious composites(ECC) with limestone and calcined clay(LCC) during earthquakes. In this paper, the effects of water-binder ratios and replacement rates of LCC were investigated on the mechanical properties of LCC-ECC under uniaxial cyclic compression. The failure mode was observed, and the law of the stress-strain curves was summarized. The influences of the water-binder ratio and LCC substitution rate on the stress degradation, stiffness degradation, and hysteretic energy dissipation were analyzed for specimens subjected to uniaxial cyclic compressive loading. The results showed that reducing water-binder ratio can effectively decrease the stiffness degradation and hysteretic energy dissipation, but had little effect on the stress degradation. The replacement rate of LCC significantly affected the stress degradation, stiffness degradation, and hysteretic energy dissipation of the specimens. In particular, the ductility and energy dissipation of the specimens were notably improved at a 50%.substitution rate. Finally, a damage constitutive model for LCC-ECC under uniaxial cyclic compression is proposed. The model accurately predicted the unloading path, reloading path, residual strain development, and damage evolution of LCC-ECC.

Accurately predicting concrete failure under compression remains a challenging task in numerical modeling. Manzoli et al. [1] introduced the Mesh Fragmentation Technique, which employs high aspect ratio interface elements between standard mesh elements to define potential crack paths. Building on this, Gimenes et al. [2] proposed an extended approach using a two-layer condensed interface element. This enhancement enables the effective modeling of compressive failure as a combination of debonding (mode-I) and sliding (mode-II) cracking, governed by tensile and shear-frictional constitutive damage models, respectively. This study highlights recent advancements in using condensed high aspect ratio interface elements to model compressive fracture in concrete. The approach is particularly well-suited for mesoscale modeling, successfully simulating uniaxial compression tests on both conventional and recycled aggregate concrete [2]. It also provides insight into the role of individual phases - aggregate, mortar matrix, and the interfacial transition zone - in the material’s response. Additionally, the method can easily simulate varying friction conditions between concrete specimens and steel loading plates. The technique is evaluated for its suitability in analyzing structural elements, such as reinforced concrete beams, on a macroscale level. The results demonstrate that the model accurately represents failure modes, including concrete crushing and shear-compression. Using two independent damage variables also allows for a clear assessment of the predominant failure mechanisms in different beam configurations.