SULFATE ATTACK IN CEMENT-TREATED BASES

US 85 in north-eastern Wyoming experienced severe distress after construction in 1992. Transverse bumps resembling frost heaves damaged the road to the point that it had to be reconstructed two years after the initial construction. After determining that a materials problem led to the heaving, a research project was set up to establish test procedures that would prevent such problems in the future. Length changes of CTB (cement-treated base) bars were evaluated in the laboratory. Three aggregate types were included in the evaluation. Gypsum and clay were added to determine their effects on expansion of the CTB. Based on these results, limits on sulfate content were proposed for aggregate used in CTB. (a)