This paper proposes using waste seashells as raw materials to partially replace fly ash in alkali-activated concrete (AAC). Fifteen groups of alkali-activated mortar and concrete were designed, with seashell powder (SP) substitution and sodium hydroxide molar concentration as variables. The material's workability, compressive strength, hydration products and micropore structures were examined. The results showed that the 3 days compressive strength of AAC with SP enhanced significantly, exhibiting an increase of nearly 30 % compared to the fly ash control. The 28 days compressive strength showed that the optimal proportion of SP replacing fly ash was 45 %. SEM images showed that micro/nanoparticles of SP filled the pores in the concrete and provided nucleation sites. Nano CT and MIP analyses indicated that the addition of SP could refine the pore structure of concrete, reducing the total porosity by nearly 30 %. Finally, the carbon emission data for 1 m³ of concrete were analyzed using a life cycle assessment approach. The carbon emissions from AAC with 45 % SP were 173.4 kg CO/m³, compared to the reference ordinary concrete reduction of approximately 60–70 %.

中文翻译：

---

贝壳粉作为粘结材料对低碳可持续碱激活混凝土性能和微观结构的影响

本文提出以废弃贝壳为原料，部分替代碱激活混凝土（AAC）中的粉煤灰。以贝壳粉（SP）替代量和氢氧化钠摩尔浓度为变量，设计了15组碱激活砂浆和混凝土。检查了材料的可加工性、抗压强度、水化产物和微孔结构。结果表明，添加SP的AAC的3天抗压强度显着增强，与粉煤灰对照相比增加了近30%。 28天抗压强度表明SP替代粉煤灰的最佳比例为45%。 SEM 图像显示 SP 微/纳米颗粒填充了混凝土中的孔隙并提供了成核位点。纳米CT和MIP分析表明，SP的添加可以细化混凝土的孔隙结构，使总孔隙率降低近30%。最后，利用生命周期评估方法分析了1立方米混凝土的碳排放数据。含有 45% SP 的 AAC 的碳排放量为 173.4 kg CO/m3，与参考普通混凝土相比减少了约 60-70%。