Kansas aggregates are frequently alkali reactive or subject to d-cracking when used in concrete. The use of deicing salt, usually halite (nacl) in kansas, makes those problems worse. Salt allows the concrete to become wet and to stay wet longer, increasing the time for reactions to occur. Clays in limestone aggregates have been altered by deicing salt solutions remaining in the aggregates. Degraded illite changed to sodium montmorillonite. Quartz has been altered by electric currents induced in the concrete. Some quartz took on an optical property, undulatory extinction, that is frequently associated with potential alkali reactivity. Salt (nacl) scaling of concrete blocks and slabs without freeze-thaw has been observed. Monitoring salt water movement through the walls of concrete cups has provided insight on how and where salt water moves in concrete. The salt water movement and deposition of salt crystals has caused considerable scaling of both the cement paste and the limestone aggregates of the concrete. The salt "gnaws away" or corrodes the limestone aggregate andcement paste, attacking the most accessible and most susceptible parts first. Particles as large as 0.6 In. Have scaled from limestone aggregates. Most of the scaled flakes are oatmeal size and no largerthan 0.2 In. In length. A silane "sealer" did not prevent salt water from moving through the limestone aggregates in the concrete cups.All three cups treated with silane cracked on the first salt treatment cycle (five days filled with salt water, emptied, soaked in plain water, then nine days of air drying). Untreated cups did not crack even after 12 cycles. No freeze-thaw was involved. This paper appears in transportation research record no. 1250, Innovation in aggregate testing.
Abstract