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detected by MIP and thus the intrusion curves do not describe the whole pore system of a
material. Hence it is more useful to redraw the porosity data to a form of column plot (Figure 2)
covering the whole size range of pores.
Pore volume/cm 3 g -1
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.001 0.010 0.100 1.000 10.000 100.000
Pore diameter/μm
Figure 1: MIP intrusion curves of thermally loaded composites
The material T in its initial – not annealed – state (sample T‐ref) features the pore size
distribution being typical for cementitious materials. The most frequent are the gel pores (d = 10
to 100 nm), the sample contains also certain amount of large technological pores. The pore
distribution of sample T 600 (annealed at 600˚C) is similar to the unloaded one; there is
observed certain increase of gel pores, the capillary and technological pores remain mostly
unaffected by this temperature. The dramatic changes of pore size distribution take place when
the sample is annealed at 800˚C and continue at 1000˚C as well. The volume of gel pores is
reduced. It is caused by thermal decomposition of cement binder. The binding components
(CSH gels and portlandite) dehydrate back to clinker minerals and CaO (it converts to calcite
spontaneously). These decomposition processes are accompanied by sintering of binder which
results to the gel pores diminishing.
Pore volume/cm 3 g -1
0.250
0.200
0.150
0.100
0.050
0.000
T-ref
T 600
T 800
T 1000
T ref
T 600
T 800
T 1000
0.001-0.01 0.01-0.1 0.1-1 1-10 10-100 > 100
Pore diameter/μm
Figure 2: Histogram of pore size distribution of thermally loaded composites T
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