The shortage of construction materials for concrete production on islands far from mainland is a long-standing problem. Coral waste is a by-product during some marine engineering works and it has the potential to be recycled as concrete ingredients. The present work reports the hydration, mechanical and durability-related properties as well as the ecological impacts of marine mortars based on coral waste and metakaolin (MK). Results show that coral waste mortar presents obviously lower compressive strength and chloride resistance than conventional river sand mortar. These defects can be overcome by MK addition due to the formation of carboaluminate, pozzolanic reaction as well as the increased water-retention of paste, which prevents water from being absorbed by coral waste sand (CS) to ensure better uniformity of matrix. Coral waste powder (CP) accelerates cement hydration but reduces the cumulative heat release due to dilution effect. The binary use of CP and MK results in a suspected heat release peak corresponding to the formation of carboaluminate at 26 h. Without sacrifice of the mechanical properties and durability, the coral waste based marine mortar incorporating 10 wt% MK reduces more than 35% non-renewable energy consumption and 40% carbon emission compared to conventional river sand mortar.

在远离大陆的岛屿上，用于混凝土生产的建筑材料的短缺是一个长期存在的问题。在某些海洋工程工作中，珊瑚废料是副产品，并且有可能作为混凝土成分进行回收。本工作报告了基于珊瑚废料和偏高岭土（MK）的海洋砂浆的水化，机械和耐久性相关特性以及对生态的影响。结果表明，与常规河砂砂浆相比，珊瑚废砂浆的抗压强度和抗氯性明显降低。通过形成碳铝酸盐，火山灰反应以及糊剂的保水性增加，可以通过添加MK来克服这些缺陷，这可以防止水被珊瑚废砂（CS）吸收，从而确保更好的基质均匀性。珊瑚废粉（CP）加速了水泥的水合作用，但由于稀释作用而减少了累积的热量释放。CP和MK的二元使用导致可疑的放热峰，其对应于26 h时碳铝酸盐的形成。在不牺牲机械性能和耐用性的前提下，与传统的河砂砂浆相比，掺入10％（重量）MK的基于珊瑚废料的海洋砂浆可减少35％以上的不可再生能源消耗和40％的碳排放量。