ABSTRACT
The share of unreacted cement in the compacted body, initially zi, is under the assumption that no cement is hydrated during the compaction, as follows: zi = z0(1 – y) (7.1) Since the volume share of cement that the water y can hydrate is zh = y/k (7.2),the fraction of unhydrated cement after hydration will be z = zi – zh = zi – yk (7.3) Taking into account that z0 + x = 1, Eqs. 7.1 and 7.2 give z = (1 – x)(1 – y) – y/k (7.4) Now the porosity in the hydrated body can be calculated asvol.% pores = y – zh€,where € is a volume increase factor = cement density/hydrate density. The hydrated cement has lower density than the unreacted cement phases, so it expands and partially fills up the pores left by the water when it reacts with the cement. Equations 7.2, 7.3, and 7.4 now yield vol.% pores = y – €[(1 – x)(1 – y) – z] The k value is different for different cement types. References 1. Hermansson, L. (2011), Nanostructural chemically bonded Ca-aluminate based biomaterials, in Biomaterials: Physics and Chemistry, Ed. R. Pignatello (INTECH, Rijeka). 2. Adolfsson, E. (1993), Phase and Porosity Development in the CaO-Al2O3-
