ASTM C666 (A) Freeze-Thaw Durability of Air-Entrained Wet- and Dry-Mix Shotcreteby Benoît Durand, IREQ Hydro-Quebec, Varennes, Canada,
Jahangir Mirza, IREQ Hydro-Quebec, Varennes, Canada,
Abstract: In order to assess the freeze-thaw durability of shotcrete, six samples of dry-mix shotcrete and one sample of wet-mix shotcrete were mixed outdoors at Hydro-Quebec's research institute (IREQ). All samples contained silica fume, type 10 or type 30 Portland cement, and steel or polypropylene fibres. An air-entraining agent was added to the mixing water of all samples except for one of the dry-mix shotcretes, sample DS1b. With the exception of DS3, all the samples had a compressive strength above 34 MPa. After 500 freeze-thaw cycles, sample DS3 showed a durability factor of 84 despite an average spacing factor of 159 μm. All the other air-entrained mixes showed excellent durability factors (DF>100) and spacing factors of less than 230 μm. The spacing and durability factors for the DS1b dry-mix shotcrete sample were 272 μm and 64, respectively. The study results showed that it is possible to entrain air in some dry-mix shotcrete mixes through the use of an air-entraining agent and to thus increase the freeze-thaw durability of such concretes.
Subject Headings: Shotcrete | Materials processing | Freeze and thaw | Entrainment | Material durability | Spacing | Compressive strength
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