Capture: Regulating CaCO3 polymorphism to unlock the potential of carbonated steel slag as a cement replacement

英国政府承诺到2050年实现净零排放。水泥和钢铁行业的碳捕获和利用（CCU）被认为是实现这一雄心勃勃的目标的核心措施。通过降低熟料比例来改变硅酸盐水泥（PC）的组成，是建筑行业脱碳的有效途径。用石灰石（CaCO3，主要是方解石）代替熟料被证明可以有效地抵消二氧化碳的排放，同时改善PC的性能。同时，各种碱性固体废物（ASW）具有捕获CO2的潜力，同时根据碳化条件产生不同的CaCO3多晶态。然而，关于含有一系列CaCO3多晶的PC的水化特性的知识缺乏。在这个概念验证项目中，我们将以钢渣（SS）作为代表性的ASW来验证以下假设：(i) CaCO3多态性可以通过控制钢渣的碳化条件来调节；（ii）不同的CaCO3多态性与PC的相互作用不同。该项目的主要目的是在英国、中国和新加坡的研究人员之间建立长期的合作伙伴关系，共同解决更有效地利用ASW作为水泥添加剂的技术挑战。来自卡迪夫大学（英国）、南京工业大学（中国）和新加坡理工学院（新加坡）的项目成员在ASW表征和碳化、水泥科学和结构工程方面具有互补的专业知识。团队的共同点是我们对CCU在建筑材料方面的研究兴趣。我们的目的是分享我们的知识和技能，促进全球对水泥和混凝土中ASW碳化和利用的理解，并探索来自不同国家的学者之间未来的研究机会。

The UK government pledges to achieve net zero emissions by 2050. Carbon capture and utilisation (CCU) in the cement and iron & steel sectors is considered a core measure toward this ambitious goal. An effective way of decarbonising the construction industry is to modify the Portland cement (PC) composition by reducing the clinker proportion. Replacing clinker with limestone (CaCO3, mainly calcite) proved to offset the CO2 emissions effectively while improving PC properties. Meanwhile, various alkaline solid wastes (ASW) have a significant potential of capturing CO2 whilst producing different CaCO3 polymorphs depending on the carbonation conditions. However, there is a lack of knowledge regarding the hydration characteristics of PC containing a range of CaCO3 polymorphs. In this proof-of-concept project, we will adopt steel slag (SS) as a representative ASW to validate the hypotheses that: (i) CaCO3 polymorphism can be regulated via controlling the carbonation conditions of SS and (ii) distinctively different CaCO3 polymorphs interact with PC differently. The main purpose of this project is to build a long-lasting partnership between researchers from the UK, China and Singapore, to collectively address the technical challenges of utilising ASW more efficiently and effectively as cement additives. The assembled project members from Cardiff University (UK), Nanjing Tech University (China) and Singapore Institute of Technology (Singapore) have complementary expertise in ASW characterisation and carbonation, cement science and structural engineering. The commonality of the team is our research interest in CCU in construction materials. Our intention is to share our knowledge and skills, advance the global understanding of ASW carbonation and utilisation in cement and concrete, and explore future research opportunities between academics from different countries.