混凝土制备低碳化演进与展望

混凝土制备低碳化是建筑领域实现“双碳目标”的重要环节。从混凝土原材料入手,综述了复合水泥、地聚合物、再生骨料的碳减排效益及潜力; 明晰了不同低碳原材料对混凝土碳排放与强度的影响规律,在碳排放-强度联合目标下,提出了低碳混凝土的简化设计思路; 最后从目标建模、优化算法两方面归纳了现有的基于强度与碳排放的混凝土配合比设计算法。结果表明:复合水泥的碳减排潜力主要取决于满足目标性能条件下高炉矿渣、粉煤灰等的最大掺入率; 相比复合水泥,地聚合物具有更大的碳减排潜力; 再生骨料在避免废弃混凝土填埋、减少运输距离与贮存阶段的碳吸收等方面具有碳减排潜力; 在不同碳排放分配方式下,固废再生产品碳减排结论差异显著,工业固废回收待建立统一碳排放分配模型,再生骨料建议采用闭环分析,避免碳排放分配; 在设定混凝土强度条件下,以降低碳排放为目标,采用复合水泥、地聚合物、再生骨料等都可以作为减碳的重要手段,碳减排幅度与低碳材料掺量、目标强度等相关; 不同低碳材料之间力学性能的协同作用以及多目标下生命周期碳减排优化模型等仍需要深入研究。

Evolution and Prospects of Low-carbon Concrete Preparation

The low-carbon development of concrete preparation is a key task of achieving the targets of carbon peak and carbon neutrality in the construction field. Based on the analysis of concrete raw materials, the carbon emission reduction benefits and potentials of blended cement, geopolymer and recycled aggregates were summarized. The influence of different low-carbon raw materials on carbon emission and strength was clarified. Under the combined goal of carbon emission and strength, a simplified design idea of low carbon concrete was provided. Finally, the existing concrete mix design algorithms based on strength and carbon emission were overviewed from two aspects of target modeling and optimization algorithm. The results show that the carbon emission reduction potential of composite cement mainly depends on the maximum incorporation rate of blast furnace slag and fly ash under the condition of satisfying the target performance. Geopolymer has greater carbon emission reduction potential than blended cement. The carbon emission reduction benefit of recycled aggregate is reflected in avoiding construction waste landfill, reducing transportation distance and carbon absorption during storage stage. The conclusion of carbon emission reduction varies significantly with different carbon emission allocation methods. A unified carbon emission reduction distribution model for industrial solid waste needs to be established, and closed-loop analysis is recommended for recycled aggregate to avoid carbon distribution. Under the setting of concrete strength, blended cement, recycled aggregate, geopolymer etc. can be used as important means of carbon reduction. Carbon emission reduction potential is related to low-carbon material content, target strength etc. The synergistic effect of mechanical properties of different low-carbon materials and the optimization model of carbon emission reduction in the life cycle under multiple objectives need further research.