Concrete durability studies

Fine and coarse aggregate from nine Montana sources were incorporated in standard State Highway mix.designs using high-and low-alkali cements.Admixtures of "fly ash" and Protex, an air-entraining agent, were used in conjunction with the above mixes.Compression tests were made using 6" x 12" cylinders, outdoor weathering specimens were made using 6" x 6" cubes, and freezing and thawing specimens were made using 3" x 6" cylinders.The nine aggregates were known to have varying degrees of "alkali-reactivity", as a result of previous chemical tests.The results from the weathering and freezing and thawing tests were correlated with the chemical reactivity tests of the aggregate and mortar-bar expansion specimens.The chemical tests showed that some of the aggregates were reactive, however, the mortar-bar expansion specimens only indicated expansions ranging from 0.002 per cent to 0.017 per cent after twelve months, After the concrete had been subjected to 73 cycles of freezing and thawing, the concrete evidenced no signs of disintegration that could be discerned by visual inspection.The concrete containing the two admixtures, in general, had lower 28 day compressive strengths than the concrete made with Portland cement, which was expected.