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From page 64... ...
The moti vation for the case example DOTs to use SCMs and ASCMs began with the desire to mitigate ASR, improve concrete durability, and capture economic benefits. However, the pathways for implementation and development of specifications differed according to the state DOTs' needs and preferences.
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From page 65... ...
Ternary and quaternary blends are allowed in pavements and structures. Caltrans allows Class F ash, ultrafine fly ash, harvested or beneficiated fly ash meeting ASTM C618-23/AASHTO M 295, slag cement, silica fume, calcined clay, calcined shale, calcined pumice, metakaolin, and rice husk ash (although rice husk ash is not commonly used)
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From page 66... ...
90-1.01D(5) allows concrete mixtures 42 days to attain required strength when the mixture design–specified strength is greater than 3,600 psi.
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From page 67... ...
This ongoing work by Caltrans and researchers will develop the targets that need to be met for Caltrans and guide updates to the specification provisions. Material characteristics and performance targets will be transferred to the approved material list requirements, along with instructions on format, amount of testing, number of replicates, and other requirements that need to be met to request review and inclusion on the approved materials list.
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From page 68... ...
Recent legislation requiring reductions in GHGs has resulted in Caltrans using concrete mixtures with a relatively low impact compared to the concrete mixtures used by many other agencies. Because Caltrans may need to continue to lower GHGs, the agency must carefully consider the baseline values to which the GHG emissions of new mixtures can be compared.
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From page 69... ...
, including the quantity in blended cement, lb/cu yd UF = silica fume, metakaolin, or UFFA [ultrafine fly ash] , including the quantity in blended cement, lb/cu yd TC = total quantity of cementitious material used, lb/cu yd For concrete satisfying the equation above, test for the compressive strength at least once every 500 cu.
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From page 70... ...
Fly ash supplier is responsible for testing the commingled fly ash The quantity of cement and SCM in concrete must comply with the minimum cementitious material content specified.
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From page 71... ...
20 percent natural pozzolan or fly ash with a CaO content of up to 10 percent, 5 percent silica fume, and 75 percent Portland cement or Type IL cement
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From page 72... ...
50 percent GGBFS and 50 percent Portland cement or Type IL cement For structures, the total cementitious material must be composed of one of the following options, by weight: 1. 25 percent natural pozzolan or fly ash with a CaO content of up to 10 percent and 75 percent Portland cement or Type IL cement.
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From page 73... ...
SL = GGBFS, including the quantity in blended cement, lb/cu yd TC = total quantity of cementitious material, lb/cu yd X = 1.8 for innocuous aggregate, 3.0 for all other aggregate MC = minimum quantity of cementitious material specified, lb/cu yd 90-2.02B Cementitious Material Minor concrete must contain at least 505 pounds of cementitious material per cubic yard. You may use rice hull ash as an SCM.
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From page 74... ...
a When tested under AASHTO M 307 for strength activity testing of silica fume. b In the test mix, Type II or V Portland cement must be replaced with at least 12 percent rice hull ash by weight.
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From page 75... ...
Allowable SCMs include Classes F and C fly ash, harvested or beneficiated fly ash meeting ASTM C618-23/ AASHTO M 295, slag cement, silica fume, calcined clay, calcined shale, calcined pumice, meta kaolin, and rice husk ash. CDOT has not experienced challenges associated with the use of SCMs with Type IL cement.
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From page 76... ...
Driven by the performance-based specification provisions that allow flexibility in material selection and mixture proportioning, contractors and ready-mixed concrete suppliers are finding means to meet Buy Clean Colorado provisions and lower GWP. CDOT is finding that its paving contractors are outperforming ready mixed concrete suppliers in terms of reducing cement content.
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From page 77... ...
Concrete mixtures currently provided for its infrastructure include high replacement rates of cement with SCMs, often in ternary blends. This has been a function of LaDOTD's specifications moving toward use of surface resistivity to support the desired durability benefits, and also industry's desire to use SCMs for economic and mixture workability reasons.
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From page 78... ...
Silica fume is also allowed at replacement rates of up to 10%, but it is typically only seen in precast concrete applications. ASTM C618 is used to guide the use of fly ash and NPs, and LaDOTD also has a slag specifica tion.
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From page 79... ...
In moving to allow higher SCM replacement rates, LaDOTD initially thought it would see cost savings passed on in bid prices since SCMs can often be lower in price than cement. However, the cost of concrete increased slightly, likely due to the surface resistivity requirements implemented in the specifications.
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From page 80... ...
MnDOT designed and trial batched all concrete mixture designs, providing a prescribed mix design to concrete producers, which led MnDOT to not have a 28-day compres sive strength requirement but only an anticipated strength expectation until 2016 when contrac tor mix designs were fully implemented. In the 1990s, MnDOT started experimenting with slag as an SCM in some concrete paving and larger bridge structures, then fully allowed it beginning with the 2000 MnDOT Standard Specifications with a cement replacement of 35%.
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From page 81... ...
MnDOT's specifications particularly support use of SCMs in concrete classes that require low permeability to improve durability performance. MnDOT's specification provisions and the contractors' positive experiences with SCMs improving construction characteristics of the mixtures have driven use of SCMs and the replacement rates.
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From page 82... ...
For general concrete mixtures, trial batching or strength performance data are required to provide a mixture design that contains greater than 15% fly ash or greater than 35% slag cement. Trial batching is not required for concrete paving projects; however, MnDOT specifications do require test results for rapid chloride permeability (ASTM C1202)
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From page 83... ...
The natural ash has been found to mitigate ASR and also does not adversely affect the water demand of concrete mixtures. The producer of the pumice material is not quite set up to produce the quantities needed for supplying UDOT projects, but the agency anticipates there will be a supply of this material in the future.
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From page 84... ...
Several different ternary blends are commonly used in Utah. One particular supplier has found success using mixtures containing NPs at 25% replacement rates and fly ash at a 5% replacement rate.
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From page 85... ...
Opportunities Associated with SCMs and ASCMs ASCMs are allowed by UDOT at replacement rates of up to 30%. Similarly to conventional SCMs, concrete with ASCMs must be qualified through tests such as those for compressive strength of concrete, surface resistivity, shrinkage, freeze–thaw durability, and air-void system parameters.
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