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A new kind of functional gradient material (FGM) based on engineering cementitious composites (ECC) and normal concrete (NC) was proposed in this study. This material offers enhanced crack control while minimizing ECC consumption. Foremost, uniaxial compression tests were carried out on single-layer NC-ECC composites featuring varying ECC volume fractions (0%, 20%, 40%, 60%, 80%, and 100%). These tests yield an elastic modulus formula, E(y), for the NC-ECC composite. Subsequently, based on the E(y) formula, a 5-layer NC-ECC FGM is designed, with each sub-layer having distinct ECC volume fractions. This is contrasted with pure ECC and 2-layer NC-ECC specimens for reference. The study concludes with an analysis of the failure patterns, load-displacement curves, and elastic moduli of the NC-ECC FGM. The results demonstrate consistent performance trends of elastic modulus in single-layer NC-ECC composite specimens, confirming the feasibility of employing a functional gradient between NC and ECC. Utilizing the formula E(y) derived from single-layer NC-ECC, the ECC volume fractions in the 5-layer NC-ECC FGM are computed as 100%, 86.89%, 68.13%, 41.55%, and 0% for each layer. Importantly, the NC-ECC FGM exhibits a failure mode resembling ECC specimens, with primary cracks not extending along interfacial layers. In contrast, 2-layer NC-ECC specimens experience cracking along interfacial boundaries. The compressive strength of NC-ECC FGM surpasses that of ECC specimens by 1.42 times while retaining ECC-like ductility, showcasing a 25.85% improvement over 2-layer NC-ECC. The findings from this study provide valuable insights for the design and subsequent engineering applications of functional gradient materials.

After coupling long-period seismic motions with the soil–structure interaction (SSI) effect, isolated structures can easily be resonated, and the seismic response of the structure is significantly enhanced. The SSI effect can alter the dynamic characteristics of a structure, resulting in a deviation between the assumed seismic-isolation effect of the rigid foundation and the theoretical results. To investigate the dynamic characteristics and seismic-response laws of interlayer structures considering SSI under long-term seismic motion, four types of ground motions (near-field ordinary, far-field ordinary, near-field pulse, and far-field harmonic ground motions) were selected, and two structural models (rigid-foundation and soft soil foundation interlayer seismic-isolation structure models) were established. Experiments were conducted using a combination of shaking-table tests and finite-element simulations. The results show that the use of the SSI effect caused the decrease in the acceleration response of the upper structure of both models under four types of seismic motions and increased the seismic peak ground acceleration (PGA). In addition, the weakening of the acceleration response of the upper structure under ordinary seismic motion is significant for longer periods of seismic motion. Furthermore, when considering the SSI effect, the displacement response ratio under long periods and ordinary ground motions is greater than that of rigid foundations, and the horizontal deformation of the isolation layer under long-period ground motions is greater than that under ordinary ground motions. This shows that the SSI effect weakens the interlayer shear force under ordinary seismic action more than that under long-period seismic action. When PGA increases, the interlayer shear force response of the interlayer isolation structure model with a soft soil foundation under a long-period seismic action may be smaller than that of the rigid-foundation model.

As a high-quality building material exhibiting excellent toughness and durability, ultrahigh-performance concrete (UHPC) is increasingly being used in the construction industry and as building reinforcement. During the reinforcement of existing concrete structures with UHPC, their interface is the weakest part of a structure. Interface bonding ensures the operation of two types of materials together. However, existing studies rarely report the bonding of the UHPC–normal concrete (NC) interface. Herein, the existing test methods and interface bonding mechanisms are summarized. Subsequently, the differences among relevant design codes are investigated by comparing different theoretical formulas. Important influencing factors of the reinforcement method, namely, interface roughness, fiber type and content, interface agent type and content, moisture content, existing concrete strength, cementitious material content, curing conditions, freeze–thaw cycles, and chloride ions, are also considered. Further, the enhancement mechanism of the characteristics of the UHPC–NC interface is clearly described. Finally, the shortcomings and application prospects of the interfacial bonding properties are highlighted.

To evaluate the chloride ion corrosion resistance of proposed innovative self-healing concrete based on shape memory alloys (SMA) and engineering cementitious composites (ECC), a total of 2 kinds of 22 specimens were prepared. Chloride ion corrosion tests of self-healing SMA-ECC concrete under dry-wet cycles were carried out. It was found that the chloride ion erosion depths of SMA-ECC were significantly smaller than that of MC, and the growth rate of erosion depth of SMA-ECC was obviously smaller than that of MC after 15 dry-wet (dry and wet) corrosion cycles. The chloride ion content of SMA-ECC vanished at the erosion depth more than 10 mm, which was consistent with the test result of AgNO3 solution color-rendering test. Test results indicate that, compared to marine concrete (MC), SMA-ECC has a better chloride ion corrosion resistance behavior. Moreover, the chloride ion concentration of SMA-ECC at a chloride ion erosion depth of less than 10 mm decreased more significantly than that of MC, indicating that almost all chloride salt solution reacted in the outer layer of SMA-ECC, which is consistent with the conclusions of 4.1 and 4.2. Finally, based on the erosion distribution of chloride ions and Fick’s second law, a calculation model describing the relationship between the apparent chloride ion diffusion coefficient and the boundary condition of the chloride ion content was proposed.