This paper experimentally studies the effects of fly ash on the diffusion, bonding, and micro-properties of chloride penetration in concrete in a water soaking environment based on the natural diffusion law. Different fly ash replacement ratio of cement in normal concrete was investigated. The effect of fly ash on chloride transportation, diffusion, coefficient, free chloride content, and binding chloride content were quantified, and the concrete porosity and microstructure were also reported through mercury intrusion perimetry and scanning electron microscopy, respectively. It was concluded from the test results that fly ash particles and hydration products (filling and pozzolanic effects) led to the densification of microstructures in concrete. The addition of fly ash greatly reduced the deposition of chloride ions. The chloride ion diffusion coefficient considerably decreased with increasing fly ash replacement, and fly ash benefits the binding of chloride in concrete. Additionally, a new equation is proposed to predict chloride binding capacity based on the test results.

Limestone calcined clay cement (LC3), consisting of ordinary Portland cement (OPC) clinker, calcined clay, limestone powder, and gypsum, has been considere

Limestone calcined clay cement (LC³) is successfully used to fabricate engineered cementitious composites (ECC) exhibiting tensile strength σ_tu of 9.55 ± 0.59 MPa or tensile strain capacity ε_tu of 8.53 ± 0.30%. The high tensile strength of the composites is closely related to the improvement of fiber/matrix interfacial bond strength, and the high ductility is attributed to the enhancement of fiber dispersion homogeneity. For the case of ECC incorporating 50% LC³, the reduction of initial cracking stress σ_tc that favors the growth of the crack in a controlled manner also contributes to the improvement of strain hardening behavior. The composition analysis indicates that carboaluminates and additional hydration products including C-(A)-S-H and ettringite are generated, which contributes to the densification of the microstructure of the ECC matrix. The pore structure is thus remarkably refined. Besides, when ordinary Portland cement (OPC) is partly replaced by LC³, the consumed energy and equivalent CO₂ emission decrease, especially the equivalent CO₂ emission with the reduction ratio attaining 40.31%. It is found that ECC using 35% LC³ exhibits the highest mechanical resistance and ECC incorporating 50% LC³ shows the highest ductility from the environmental point of view.