An Electrochemical Approach to Study Carbonation of Novel Lime Based Materials

该项目旨在促进当前对石灰和水泥材料中碳化作用的理解。提出了一种利用微pH电极研究二氧化碳反应的新方法。样品表面的薄水膜中的pH变化将使反应机理得以确定。通过全面的电子、光学和表面分析研究，将提供对表面形态和成分的详细了解。这些材料与二氧化碳的反应非常有趣，因为封存二氧化碳是旨在减少气候变化的一项关键举措。与水泥等替代产品相比，石灰在固化过程中能够吸收明显更多的二氧化碳，除了翻新和新建项目外，石灰还在历史建筑的修复和保护中具有重要应用。水泥的强度是通过活性硅酸盐和铝酸盐熟料相的水化来获得的，然而，从长远来看，这些相的碳化会导致力学性能的降低和钢筋的腐蚀。尽管碳化的化学过程众所周知，但人们对石灰和水泥砂浆中的机理知之甚少。这项研究计划旨在解决这个问题。近年来，大麻和一系列工业过程中产生的废物等低碳足迹材料的生产商表示有兴趣将它们的材料作为填充剂和添加剂加入石灰和水泥产品，包括砂浆、抹灰、石膏和混凝土。这些环境友好材料的加入不仅会影响微孔和宏观孔结构，而且可溶组分可能会在孔隙水中引入离子物种，其对碳化作用的影响尚不清楚。这项建议旨在通过监测氢氧化钙衬底表面液膜内不同位置的离子浓度来研究碳化过程。质子浓度将使用专门制造的微电极测量，该微电极由直径约10微米的纳米结构氢化钯盘组成，并电沉积在普通微盘电极的末端。用微型定位器精确控制，PH值微电极将被带到距离被研究表面几微米的范围内。以类似的方式，商业上可用的离子选择电极将被用来确定钙离子浓度。在该项目的第二阶段，将调查从通常与石灰一起使用的添加剂中浸出的离子的影响。它们可分为以下五类：高炉渣(GGBS)、瓶装玻璃、木灰、大麻和偏高岭土。感兴趣的添加剂将包括玻璃、灰渣和有机表面活性剂。

This project seeks to advance the current understanding of carbonation in lime and cement materials. A novel approach is proposed where the reaction with carbon dioxide will be studied using micro pH electrodes. pH variations in a thin water film at the sample surface will allow the reaction mechanism to be determined. A detailed understanding of the surface morphology and composition will be provided by a comprehensive electron optical and surface analytical study. The reaction of these materials with carbon dioxide is or great interest as sequestration of carbon dioxide is a key initiative aimed at reducing climate change. Lime has the ability to adsorb significantly higher quantities of carbon dioxide during the setting process in comparison to alternative products such as cement and has important applications in the restoration and conservation of historic buildings in addition to renovation and new build projects. Cement acquires its strength from hydration of reactive silicate and aluminate clinker phases however in the long term carbonation of these phases can lead to a reduction in mechanical performance and the corrosion of steel reinforcements if present.Although the chemical process of carbonation is well known the mechanisms in lime and cement mortars are poorly understood. This research programme seeks to address this issue.In recent years the producers of low carbon footprint materials such as hemp and wastes from a range of industrial processes have expressed interest in the incorporation of their materials as fillers and additives in lime and cement products including mortars, renders, plasters and concrete. The addition of these environmentally friendly materials not only influence the micro and macro pore structure but soluble constituents may introduce ionic species into the pore water, the influence of which on carbonation is unknown. This proposal aims to study the carbonation process by monitoring ion concentrations at different locations within the liquid film on the surface of a calcium hydroxide substrate. Proton concentrations will be measured using specially manufactured microelectrodes consisting of nanostructured palladium hydride discs approximately 10 micrometers in diameter and electrodeposited on the end of a normal microdisc electrode. Held precisely with a micropositioner the pH microelectrode will be brought to within a few micrometres from the surface under investigation. In a similar way, commercially available ion selective electrodes will be used to determine the calcium ion concentration. In the second phase of the project the effect of ions leached from additives commonly used in conjunction with lime will be investigated. These can be divided into the following five groups, blast furnace slag (GGBS), bottle glass, wood ash, hemp and metakaolin.Additives of interest will include glass, ashes / slag and organic surfactants.