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mixture by short mixing, the mixture put into the forms, evacuated for one hour and
autoclaved.
Before the measurements, all specimens were dried in an oven at 110°C. In the experiments,
four various sample pre‐treatment conditions were tested: reference specimen not exposed to
any load (denoted as T‐ref in what follows), specimen exposed to a gradual temperature
increase up to 600, 800 and 1000°C during two hours, then left for another 2 hours at the final
temperature and slowly cooled (denoted as T‐600, T‐800 and T‐1000 according to the loading
temperature).
Experimental Methods
Table 1: Composition of the studied composite material
Components Amount [%kg/kg]
Cement CEM I 52.5 36
Siliceous aggregates 17
Microsilica 940 US 4
Wollastonite 39
Aramid fiber 1.5 mm 2
Aramid fiber 6 mm 2
w/c 0.9
1.1. Determination of pore size distribution
The texture changes of the studied composite were described by means of porosity and pore
size distribution. Total porosity was calculated by help of bulk density and matrix density.
Matrix density was determined by helium pycnometry (Pycnomatic ATC, Porotec, Germany),
bulk density by weighing and measuring dimensions of rectangular specimens. Pore size
distribution was determined by Mercury Intrusion Porosimetry (MIP) by equipment Pascal 140
+ 440 (Thermo Electron Corp., Italy). The contact angle was assumed to be 130˚. The material’s
samples for MIP were crushed to pieces of about 2 mm in order to avoid presence of any large
free spaces in the sample. Since only the pores of diameter from 0.003 to 100 μm are visible for
MIP, the volume of pores over 100 μm was estimated by help of total pore volume Vp and pore
volume measured by MIP ‐ VHg which corresponds to pores having d < 100 μm.
Water vapor transport properties
The wet cup method and dry cup method [1] were employed in the measurements of
water vapor transport parameters. The specimens were water and vapor proof insulated by
epoxy resin on all lateral sides, put into the cup and sealed by technical plasticine. The
impermeability of the plasticine sealing was achieved by heating it first for better workability
and subsequent cooling that resulted in its hardening. In the wet cup method the sealed cup
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