Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report A : evaluation of HVFA cementitious paste and concrete mixtures.
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Design and evaluation of high-volume fly ash (HVFA) concrete mixes, report A : evaluation of HVFA cementitious paste and concrete mixtures.

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      NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance ; NTL-HIGHWAY/ROAD TRANSPORTATION-Design ;
    • Abstract:
      In the Paste Screening Study, 25 combinations of five Type I/II portland cements and five Class C fly ashes commonly used in Missouri were tested in paste form with no chemical or powder additives. Testing procedures included semi-adiabatic calorimetry, Vicat setting time, miniature slump, and compressive strength at one and 28 days. The two most reactive and two least reactive combinations (defined by one day strengths) were further evaluated in the Paste Main Effects Study. Eighty mixtures were examined. In the Paste Main Effects Study, the effects of two levels each of WR/HRWR, gypsum, calcium hydroxide (lime), rapid set cement (RSC), and gypsum-lime, and gypsum-RSC were determined. Except for the WR/HRWR dosage level experiment, all other mixtures contained a low WR/HRWR dosage. Except for the gypsum level experiment, all other mixtures contained 4% gypsum. The lime levels were 5 and 10% and the RSC levels were 10 and 20%. All percentages are by mass of fly ash. Sixty-four mixtures were examined. The objective of the Concrete Properties Study was to scale up from paste to concrete the most promising powder additive combinations and then evaluate the mixtures in terms of plastic and hardened properties. Thus the mixture matrix included ordinary portland cement (OPC)-fly ash blends at two levels (same as in the Paste Main Effects Study) and fly ash at three levels (zero, 50 and 70%). WR dosage (nominal dosage), gypsum content (4%), lime content (10%), and RSC content (20%) were held constant. Ten concrete mixtures were evaluated. At the 50% fly ash level, one day strengths were low no matter which powder additives was used, but good strengths were achieved by day 3. At the 70% fly ash level, the concrete was weaker than at zero and 50% fly ash, but reasonable strengths were reached at 28 days. At 50% fly ash, abrasion resistance was somewhat lower. At 70% the effect was much worse. In regard to drying shrinkage, it appears that HVFA mixtures shrink less than their OPC counterparts. In a comparison to OPC mixtures, rapid chloride permeability (RCP) was lower for 50% fly ash mixtures, but 70% fly ash mixtures are more permeable. All HVFA mixtures had greater freeze-thaw Durability Factors than the OPC mixtures, and were at 93 or above. However, all fly ash mixtures did poorly in regard to salt scaling. Reaction time (calorimeter curve time, setting time, stiffening time) varied as a function of characteristics of the OPC and fly ash in conjunction with each other, type and level of powder additives used, dosage of WR/HRWR, and the type of test method used for evaluation.
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