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From page 8... ...
The three conventional types of SCMs used in con crete, and discussed in this report, are coal ash (fly ash) , slag cement, and silica fume.
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From page 9... ...
. ASTM C618-23 Updates In ASTM C618-23, Standard Specification for Coal Ash and Raw or Calcined Natural Pozzolans for Use in Concrete, the term "coal ash" includes both fly ash and bottom ash produced from current power plants or harvested from landfills and impoundments.
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From page 10... ...
. The most effective method for evaluating the performance of fly ash in concrete Table 1. Changes in the properties of concrete when Class C or Class F coal ash is used to replace Portland cement in a mixture (Kosmatka and Wilson 2011)
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From page 11... ...
Since coal ash has a lower specific gravity (2.28–2.7) than that of Portland cement (typically 3.15)
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Permeability and Durability Use of fly ash in concrete mixtures reduces the permeability and improves the durability of concrete structures so that they better resist ASR, sulfate attack, and chloride penetration; it also
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with an increase in the percentage of fly ash replacement in cement in concrete mixtures (Figure 3) (Armaghani et al.
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Concrete mixtures that include Class C fly ash with a high percentage of CaO, especially when used at high rate of cement replacement (30%) , are highly susceptible to sulfate attack and deterioration (Tikalsky and Carrasquillo 1993)
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From page 15... ...
Harvested Coal Ash Use of harvested coal ash is one of the solutions for the decline in the availability of coal fly ash. Over the years, a significant amount of ash that had been produced in coal-burning power plants was discarded in landfills due to noncompliance with the prevailing specifications governing beneficial reuse at the time, including previous versions of ASTM C618 for fly ash use in concrete.
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From page 16... ...
. Strength activity index results for harvested coal ash may be slightly lower, higher, or compa rable to those of conventional fly ash, depending in part on the particle size distribution of the material.
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The specific gravity of slag cement ranges from 2.85 to 2.94, depending on the slag source, as compared to 3.15 for Portland cement [Slag Cement Association (SCA)
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From page 18... ...
. Properties of Fresh Concrete with Slag Cement Workability and Water Demand In general, slag cement improves the workability and cohesion of concrete mixtures due to the added paste volume from a high replacement rate for Portland cement and the lower spe cific gravity of slag (2.85–2.94)
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From page 19... ...
. Set Time Delays in set time can be expected when more than 25% slag cement is used as a replacement for Portland cement in a concrete mixture.
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From page 20... ...
Figure 7. Compressive strength of concrete containing various percentages slag cement content compared with no-slag concrete (Hogan and Meusel 1981)
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From page 21... ...
Also, by reducing the heat generated in mass-concrete elements, slag cement contributes to controlling temperature rise at early ages to prevent thermally induced cracking and loss of durability. Resistance to ASR Use of slag cement as a partial replacement for Portland cement is known to reduce ASR and its associated damaging expansion of concrete (Hogan and Meusel 1981)
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From page 22... ...
. Air-entrained concrete containing 50% slag cement was found to be resistant to freezing and thawing, even though a measurable difference in mass loss was found when compared to the concrete made with Type II Portland cement and tested using ASTM C666/C666M (Procedure A)
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From page 23... ...
. Table 4. Chemical compositions of cement, fly ash, slag, and silica fume (Kosmatka et al.
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From page 24... ...
. Silica fume may be added directly to concrete mixtures as a binary ingredient with Portland cement, in ternary mixtures with Portland cement and another SCM, or in quaternary mixtures with Portland cement, coal ash, and slag cement.
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From page 25... ...
As such, adding silica fume to concrete mixtures increases the water demand compared to ordinary concrete mixtures. However, adding more water to the mixture will not be a good option since this tends to negate the positive impact of silica fume on strength and durability.
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From page 26... ...
Resistance to ASR Use of silica fume in sufficient quantities in concrete with or without other SCMs (slag cement or fly ash) can be effective in resisting ASR.
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. Performance of Silica Fume in Pavements In cold regions, use of silica fume in concrete mixtures for pavement for highways and other flat surfaces improves resistance to the effects of freeze–thaw cycles and deicing salts.
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It has been used not only in binary concrete mixtures but also in ternary mixtures in combinations with either Class C or Class F fly ash or silica fume (ACI 232.1R-12)
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From page 29... ...
. To achieve such benefits, RHA is included in the concrete mixture at 5% to 15% replacement by mass of Portland cement.
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From page 30... ...
Performance criteria, such as ASR mitigation, sul fate resistance, and temperature rise, could dictate the required minimum quantity of NP to be incorporated as a percentage of the total cementitious material. The partial replacement of Portland cement by conventional and natural pozzolans with high levels of silica, alumina, and iron oxide increases the resistance of concrete to ASR, sulfate attack, Figure 12. Effect of replacing part of Portland cement in concrete with metakaolin on calcium hydroxide content of concrete as it cures (Kostuch et al.
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From page 31... ...
This is mostly due to the quantity of Portland cement they replace. The setting-time characteristics of concrete containing an NP are influenced by ambient and concrete temperature; cement type, source, content, and fineness; water content of the paste; water-soluble alkalis; and use and dosages of other admixtures.
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From page 32... ...
An NP of high pozzolanic reactivity, such as metakaolin, may increase both early- and later-age strengths when used as replacement by mass or volume of the Portland cement in the mixture, as shown in Figure 13 (Hooton et al.
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From page 33... ...
One study showed that the sulfate resistance of mortar is highest when silica fume or a highly siliceous natural pozzolan is used. The relative improvement is greater for concrete with low cement content and with Portland cement of higher C3A content (Mather 1982)
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From page 34... ...
. Table 6. Impact of SCMs on properties of hardened concrete (Kosmatka et al.
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From page 35... ...
while ensuring effective curing will achieve the desired fresh and hardened concrete properties. The use of ternary mixtures incorporating Portland cement, silica fume, and either fly ash or slag cement has been on the increase in the last few years, as will be shown in discussion of the survey results of state DOTs in Chapter 3.
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From page 36... ...
. For example, when slag cement is used in concrete mixtures with silica fume, the amount of silica fume can be reduced compared to a mix ture of equivalent durability with Portland cement and silica fume.
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From page 37... ...
. Recent advancements in understanding the reactivity of an ASCM have been made, including the use of the R3 test, which is now ASTM C1897, Standard Test Methods for Measuring the Reactivity of Supplementary Cementitious Materials by Isothermal Calorimetry and Bound Water Measurements (Snellings et al.
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From page 38... ...
The impact of the material on a concrete mixture's workability/finishability, strength gain, and durability must also be assessed. The potential of these materials to have adverse environmental effects must also be considered (Cavalline and Sutter 2024)
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From page 39... ...
. Studies have shown that mortar and concrete including GGP exhibit reduced absorption and permeability, which lowers susceptibility to sulfate attack, improves resistance to chloride penetration, and reduces carbonation potential (Shi et al.
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From page 40... ...
. Studies have shown that the reactivity of waste ceramic ASCMs in mortar and concrete is similar to that of coal ash or natural pozzolans (Snellings et al.
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From page 41... ...
. A key challenge to use of MSWI ash in the United States is that many MSWI plants combine residues produced (bottom ash, fly ash, and air pollution control residues)
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From page 42... ...
. Using the R3 reactivity test, the reactivity of NFM slag has been shown to be similar to that of coal ash, with a similar later-age strength gain (Hallet et al.
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From page 43... ...
and product (concrete) produced using the material • The potential variability of the material's characteristics • The performance of the ASCM or system containing the ASCM • Implementation of measures during design, construction, and use to mitigate potential envi ronmental impacts ASTM C1709, Standard Guide for Evaluation of Alternative Supplementary Cementitious Materials (ASCM)
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From page 44... ...
Material Characterization and Application Testing • Tests for qualification/preconstruction stage - Tests of byproduct material - Tests of application containing byproduct material • Tests upon delivery or construction - Tests of byproduct material - Tests of application containing byproduct material Environmental Analysis • Chemical analysis • Toxicity Characteristic Leaching Procedure (TCLP) • Other tests required by agency or regulations • Design considerations to protect the environment • Construction considerations to protect the environment • Environmental Product Declaration (EPD)
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From page 45... ...
In Stage IV, concrete mixtures are prepared to facilitate evaluation of the ASCM in fresh and hardened concrete. The mixture(s)
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