An Electrochemical Approach to Study Carbonation of Novel Lime Based Materials

该项目旨在促进目前对石灰和水泥材料碳化的理解。提出了一种利用微pH电极研究与二氧化碳反应的新方法。样品表面水膜的pH值变化将使反应机理得以确定。全面的电子光学和表面分析研究将提供对表面形貌和组成的详细了解。这些材料与二氧化碳的反应引起了人们极大的兴趣，因为二氧化碳的封存是减少气候变化的关键举措。与水泥等替代产品相比，石灰在固化过程中能够吸附大量的二氧化碳，除了翻新和新建项目外，在修复和保护历史建筑方面也有重要的应用。水泥从活性硅酸盐和铝酸盐熟料相的水化中获得强度，然而，从长期来看，这些相的碳化会导致机械性能的降低和钢增强物的腐蚀。虽然碳酸化的化学过程是众所周知的，但石灰和水泥砂浆中的机制却知之甚少。本研究方案旨在解决这一问题。近年来，低碳足迹材料的生产商，如大麻和来自一系列工业过程的废物，对将其材料作为填料和添加剂掺入石灰和水泥产品（包括砂浆、渲染、石膏和混凝土）表示了兴趣。这些环保材料的加入不仅影响微观和宏观孔隙结构，而且可溶性成分可能会将离子引入孔隙水，而离子对碳化的影响尚不清楚。本提案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。质子浓度将使用由直径约10微米的纳米结构氢化钯圆盘组成的特殊制造的微电极来测量，并电沉积在普通微圆盘电极的末端。用微定位器精确地保持pH微电极将被带到距离被调查表面几微米的范围内。以类似的方式，市售的离子选择电极将用于测定钙离子浓度。在该项目的第二阶段，将研究常用添加剂与石灰联合浸出的离子的影响。这些可分为以下五类，高炉渣（GGBS），瓶玻璃，木灰，大麻和偏高岭土。感兴趣的添加剂将包括玻璃，灰烬/炉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.