Experiments were conducted to determine the influence of immersion vibration on the air-void system parameters of air-entrained concrete, as a function of both radial distance and depth from the point of vibrator insertion. For a 1½ in. (40 mm) diameter immersion vibrator, one could conclude that vibration has little or no effect on air-void systems at distances of 5, 8, or 10 in. (125, 200, or 250 mm) from the point of insertion. The same vibrator in the same concrete can reduce the total air content by 50 percent, and increase specific surface by as much as 100 percent directly at the point of vibrator insertion. Which particular effect one may observe in hardened concrete, therefore, depends on the selection of core location relative to point of vibrator insertion. These observations have implications for specifying, casting, and testing air-entrained concrete.

The 100 m reinforced concrete open spandrel arch bridge over the Storms River Gorge was constructed in the mid-1950s, and in 1982 surface cracking of the concrete was noticed. Cores were obtained from the various members and laboratory testing confirmed that the concrete was suffering from the effects of alkali-aggregate reaction (AAR). In 1986, the decision was made to rehabilitate this bridge, consisting of two distinct stages, of which the first was widening and strengthening the superstructure, as well as strengthening the concrete arch rib itself. The second stage consisted of treating the concrete surfaces with a hydrophobic coating to halt any further effects of AAR. To assess the long-term effectiveness of the hydrophobic coating, the bridge was instrumented and strain gage readings were taken at regular intervals. The analysis of the readings show that the concrete has been shrinking since the strain readings were started, confirming that, to date, the silane hydrophobic coating is still effective.

Among the important stages of the overall SR process as it occurs in concrete is the conversion of alkali sulfate dissolved from the cement to alkali hydroxide. The results of laboratory studies are presented to provide an understanding of this process and its effects. This conversion process depends on continued formation of ettringite and does not take place until the cement gypsum is exhausted. Provision of a large excess of gypsum or interference with early ettringite production by high-temperature exposure may postpone or prevent it, thus reducing the OH - ion concentration and the possibility of ASR reaction.

As the sole domestic building material in Iceland, concrete is widely used for house construction as well as for other construction, such as dams, bridges, and harbors. In Iceland, conditions are in many ways extreme: the climatic conditions are harsh, the cement is high in alkalies, aggregates are of varying quality (some being reactive), and codes and standards have been sparse. Field surveys have shown that alkali-aggregate reaction (AAR) damage occurs where no preventive measures were taken and other conditions were unfavorable. Preventive measures taken in dam and bridge construction have proven to be effective. No AAR damage has been found in constructions erected after 1979, when several preventive measures were taken. The most important one is 5 to 7+ percent replacement of cement with silica fume Stricter criteria have been enforced to secure freeze-thaw durability, and durability design is improving. Research in repair and maintenance methods has had considerable influence on the construction industry.

One of the major problems with rehabilitation of frost damage in old non-air-entrained hydraulic structures is prevention of failure of the repaired surface at the new/old concrete interface or in the old substrate concrete below the repair due to trapped moisture and subsequent freezing of the critically saturated substrate. A survey of several 40- to 75-year-old, non-air-entrained concrete dams indicated that in many cases the concrete at the water line was not damaged due to freezing and thawing. This would appear to contradict conventional wisdom based on ASTM C 666 testing of non-air-entrained concrete. Instead, most of the deterioration had taken place on the inclined downstream faces of the gravity sections, away from direct exposure to water, but subject to many cycles of freezing in air. In some cases, water leaked through joints in the concrete and initiated progressive raveling. However, in other cases, it appeared that moisture was drawn to the exposed surfaces by capillary suction. As a result of these observations, it was decided to develop a one-sided freezing test, with the unfrozen side exposed to water and the freezing side exposed to air, to better simulate field exposure. The cylindrical concrete specimens are monitored with temperature, relative humidity, and moisture probes at various depths during testing. This should allow evaluation of non-air-entrained concrete and various repair materials on the freezing surface to observe whether moisture is building up to critically saturated levels that would result in deterioration. While the equipment for this test has been designed and built, testing is at a preliminary stage. Describes the nature of frost damage in hydraulic structures and then describes the new test procedure in detail.