INTERACTION BETWEEN SURFACE CHARGE PHENOMENA AND MULTI-SPECIES DIFFUSION IN CEMENT BASED MATERIALS
Measurements strongly indicate that the inner surface of the microscopic structure ofcement based materials has a fixed negative charge. This charge contributes to the formationof so-called electrical double layers. In the case of cement based materials the ionic specieslocated in such layers are typically potassium -, sodium-and calcium ions. Due to the highspecific surface area of hydrated cement, a large amount of ions can be located in thesesdouble layers even if the surface charge is relatively low. The attraction force, caused by thefixed surface charge on ions located close to surfaces, is one possible explanation for theobserved low global diffusion rates in the pore system of positively charged ions compared tothe negatively charged ones. Here it is of interest to simulate the multi ionic diffusionbehavior when assigning positively charged ions a comparably lower diffusion constant andalso including a negatively charged ion with an extremely low diffusion constant so as torepresent a fixed negative surface charge. The theoretical results from such simulations, usinga tailor made finite element technique, indicates a strong influence of surface charges onglobal diffusion of different ionic species in the pore system of cement based materials.
B.Johannesson
Technical University of Denmark,Department of Civil Engineering,Denmark
国际会议
南京
英文
565-574
2008-10-13（万方平台首次上网日期，不代表论文的发表时间）