The role of timely controlled PCC in concrete performance development

本课题将研究适时控制沉淀碳酸钙（PCC）技术在混凝土中的碳化诱导水化及其相关的CO2封存的基础科学，以实现环境、技术和经济的综合效益。排放到大气中的二氧化碳有很大一部分来自点源。找到从点源捕获或回收的二氧化碳的商业用途，对减少温室气体排放至关重要。其中一个很有前途的方法是通过它们的产品将二氧化碳隔离在混凝土中。麦吉尔大学（McGill University）的研究表明，如果美国和加拿大的四种混凝土产品都经过碳化处理，那么每年大约可以在混凝土产品（如砌块、摊铺机、水泥板和纤维板）中封存180万吨二氧化碳。水泥行业二氧化碳排放量减少2.6%。它意义重大，但仍然不大。为了进一步增强混凝土的固存能力，需要探索更高的反应效率和更多的生态位应用产品。本研究将重点研究早期通用混凝土的碳化过程，建立一个碳化和水化顺序发生的过程，在保持水化特性的同时封存足够的碳。目标是：(1)了解早期（0.5至24小时）PCC形成的机制，(2)量化不同龄期碳化对二氧化碳的吸收，(3)研究混凝土中PCC的优势，(4)利用回收的二氧化碳和烟气开发加压和真空PCC技术，(5)通过碳化制造混凝土管道以吸收碳和抗硫酸盐。(6)对预制混凝土进行可控碳化，使其吸碳和碱硅反应（ASR）还原；(7)对GFRP筋加固的预制混凝土进行强碳化，使其吸碳和耐久性提高；(8)开发现浇混凝土的真空碳化，使其吸碳和快速凝固。拟议的碳封存技术是可持续的，因为它是经济的一个组成部分，可以在未来几十年在全球任何地方使用。

The proposed research will study fundamental science on timely controlled precipitated calcium carbonate (PCC) technology for carbonation induced hydration and its associated CO2 sequestration in concrete for combined environmental, technical and economical benefits. A significant fraction of the CO2 discharged to the atmosphere comes from point sources. Finding commercial uses of as-captured or recovered CO2 at point sources is critical to greenhouse gas emissions reduction. One of the promising approaches is to sequester carbon dioxide in concrete through their productions. Research at McGill University has shown that approximately 1.8 million tones of CO2 can be sequestered annually in concrete products such as blocks, pavers, cement boards and fibreboards, if all four products in US and Canada are carbonation treated. It reduces CO2 emission from cement industry by 2.6%. It is significant but still modest. To further enhance the sequestration capacity by concrete, higher reaction efficiency and more products of niche applications should be explored. The proposed research will focus on carbonation of general use concrete at early ages to establish a process in which carbonation and hydration can occur sequentially to sequester sufficient carbon while maintaining hydration features. The objectives are (1) to understand the mechanism of PCC formation at early age (0.5 to 24 hours), (2) to quantify CO2 uptake by carbonation at different ages, (3) to investigate the advantages of having PCC in concrete, (4) to develop pressurized and vacuum PCC technology using recovered CO2 and flue gas, (5) to fabricate concrete pipes by carbonation for carbon uptake and sulfate resistance, (6) to perform controlled carbonation to precast concrete for carbon uptake and alkali silica reaction (ASR) reduction, (7) to perform strong carbonation to precast concrete reinforced by GFRP rebar for carbon uptake and durability, (8) to develop a vacuum carbonation for cast-in-place concrete for carbon uptake and fast setting. The proposed carbon sequestration technology is sustainable because it is an integrated part of economy and can be used anywhere worldwide for decades to come.