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The authors indicate that, in addition to steel corrosion, calcium chloride can act specifically as an aggressive agent for concrete through the formation of calcium oxychloride (3CaO CaCl 2 15H 2O). This product is formed by reaction of CaCl 2 diffusing through the cover and Ca(OH) 2 produced by cement hydration. The main purpose of the paper was to study the influence of the cementitious system (portland cement with and without a pozzolanic addition) on the damaging effect caused by CaCl 2 used as a deicing agent. To block both steel corrosion and concrete deterioration, the reduction of the water-cement ratio in the concrete mix should be accompanied by the utilization of slag cement or pozzolanic cement. The slag content should be at least 50 percent of the cement, but silica fume (> 15 percent by weight of cement) instead of fly ash (30 percent) is preferred.

The validity of recent revisions to CAN/CSA A23.1 and ACI 318, which change the criteria for durability under various exposure conditions involving freezing and thawing from limits on water-cement ratio (w/c) to limits on water-cementitious materials ratio (w/cm), is challenged for conditions that involve freezing and thawing with deicing salts. Test results to quantitatively determine resistance to deicer scaling in terms of weight loss per unit area of exposed surface show that concretes with fly ash or silica fume as part of the cementitious material behave very differently from each other and from concretes with only cement as the binder. Fly ash concretes generally scale severely with weight losses in excess of 1 kg/m 2 even when w/cm values are well below the code maximum of 0.45. Performance appears unrelated to w/cm and instead quite closely related to w/c. Silica fume concretes exhibit superior scaling resistance with weight losses less than 0.5 kg/m 2 even when w/cm values approach or exceed the 0.45 limit. Reference concretes exhibit satisfactory scaling resistance at w/c values of 0.45 or less. Clearly, the composition of the cementitious material has a major effect on resistance to scaling in the presence of deicing salts. Replacing the traditional w/c limits with w/cm in CAN/CSA A23.1 and ACI 318 is unjustifiable and may lead to serious scaling problems with concretes proportioned to meet the current w/cm code requirements, particularly those containing fly ash. The traditional w/c limit of 0.45 is associated with satisfactory scaling resistance for properly air-entrained concretes containing cement alone or in combination with silica fume. This limit also appears applicable to the fly ash concretes evaluated according to the trend of available data, but confirmatory tests at w/c values below 0.50 are needed.

The commonly used deicing salts (sodium and calcium chloride) are well known for their ability to melt ice, but unfortunately are also well known for their detrimental effect on freeze-thaw resistance and surface scaling of concrete. For the past several years, the authors have been conducting a search for a noncorrosive deicer to replace or modify sodium and calcium chloride. The investigation focused on phosphate-chloride mixtures, but also included potassium acetate, calcium magnesium acetate, and phosphate pretreatments of specimens. Testing was done on mortars containing a known, frost-susceptible aggregate (shale sand); the mortar was exposed to various destructive deicer concentrations under freezing and thawing conditions. Scaling loss and ice-melting ability of the various concentrations are compared. Simple experiments to evaluate corrosion of steel were also performed. Although phosphate salts have long been suggested as alternate deicers, they are not effective by themselves. Most promising in the current study are the monophosphates of sodium, potassium, and calcium mixed in specific proportions with chlorides. The phosphate-chloride mixtures also provide some corrosion protection. A deicer mixture of sodium chloride with a relatively small proportion of phosphate may prove to be an effective, benign, and economic deicer.

This laboratory and field investigation studied the deicer scaling resistance of ground granulated blast furnace (GGBF) slag concretes. The laboratory part of the investigation used the ASTM C 672 test with up to four different curing routines: air, curing compound, the standard procedure, and intermittent wet cure. The field part evaluated three curing routines: air, curing compound, and intermittent wet cure. It also evaluated two different finishing tools, and the effect of a linseed oil-kerosene sealer applied at 90 days. Overall, regarding the effect of GGBF slag dose on scaling resistance, and relative to portland cement content: 25 percent improved resistance, 35 percent was better in the laboratory and similar in the field, 50 percent was variably better or the same or worse, and 65 percent scaled more in the laboratory and less in the field.

An overview of the scientific and technical literature published on the subject is presented. The first part of this report is devoted to the fundamentals of frost action in concrete. The mechanisms of freezing and hypotheses explaining the detrimental effects of deicing salts are discussed. Special attention is paid to the influence of the concrete curing temperature and moisture history on its frost durability. A critical appraisal of three different test procedures designed to assess the deicer salt scaling resistance of concrete is given in the second section. Each test method is evaluated on the basis of reproducibility, variability of test results, operating cost, and relationship to field exposure conditions. Finally, the influence of various parameters on the deicer salt scaling resistance of concrete is discussed. Topics such as mix composition, air entrainment, casting operations, curing, and use of concrete sealers are reviewed.