High Performance Concrete Specifications and Practices for Bridges (2013) / Chapter Skim
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From page 18... ...
18 chapter three cURRENT SPEcIFIcATIONS AND PRAcTIcES FOR cAST-IN-PLAcE cONcRETE a w/cm ratio, at least two states specify an upper limit for the total water content. The total water content includes any water in the SCMs and admixtures and any water beyond the saturated surface dry condition of the fine and coarse aggregates.
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From page 19... ...
19 cONcRETE cONSTITUENT MATERIALS Most state bridge standards define that concrete shall consist of hydraulic cement or portland cement, SCMs, fine aggregate, coarse aggregate, water, chemical admixtures, and air-entraining admixtures. Other state specifications do not include a precise definition, although all the concrete constituent materials are included in the specifications.
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From page 20... ...
20 Aggregates Aggregates for concrete used in bridge decks may be normal weight aggregates conforming to AASHTO Specifications M 6 and M 80, lightweight aggregates conforming to AASHTO M 195, or a combination of them. The coarse aggregate size is generally selected to be the largest size practical under job conditions (Kosmatka and Wilson 2011)
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From page 21... ...
21 The data indicate that agencies use a variety of the chemical admixtures specified in AASHTO M 194 with Type A -- water-reducing and Type F -- high range waterreducing being the more frequently used types and Type E -- water reducing and accelerating the least common. Corrosion inhibitors, shrinkage reducing admixtures, and expansive components are used by a few agencies.
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From page 22... ...
22 curing periods from three to 14 days, with the most frequent value being seven days (Russell 2004)
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From page 23... ...
23 Strategy to Minimize Bridge Deck Cracking 2012 Survey Responses 2003 Survey Responses No. %1 % Specify maximum w/cm ratio 34 94 -- Specify minimum concrete compressive strength 33 94 -- Specify maximum concrete temperature at placement 32 94 80 Specify maximum slump 30 86 98 Specify minimum concrete temperature at placement 30 83 -- Required fogging when evaporation rates are high 27 77 67 Specify minimum cementitious materials content 26 76 -- Specify maximum cementitious materials content 19 54 33 Require use of the ACI surface evaporation nomograph 18 55 -- Specify maximum water content 14 42 -- Require windbreaks during concrete placement 13 38 22 Specify maximum concrete temperature during curing 9 30 -- Require evaporation retardants 9 28 29 Specify a ratio between 7- and 28-day compressive strengths 5 16 -- Specify a maximum concrete compressive strength 4 13 4 1 Percentages appear inconsistent because not every respondent answered every option.
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From page 24... ...
24 • Maximum fly ash content of 15% to 30% of the total cementitious materials content, • Maximum silica fume content of 7% to 10% of the total cementitious materials content, • Minimum silica fume content of 5% to 7% of the total cementitious materials content, when used, and • Maximum slag cement content of 30% to 50% of the total cementitious materials content. Specified maximum w/cm ratios generally range from 0.40 to 0.50 for bridge decks.
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