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Min max dosage of admixture
This document provides information on determining the minimum and maximum dosage ranges for concrete admixtures. It recommends conducting a Marsh cone flow test to establish the saturation point for different admixture dosages. The test involves mixing cement and admixture slurry at varying dosage levels and measuring flow time. The results are plotted to identify the saturation point beyond which excess admixture will not improve workability and may cause segregation issues. Optimal admixture dosage should not exceed this saturation point determined from the Marsh flow test data.
Min max dosage of admixture
- 1. Title MINIMUM ANDMAXIMUM DOSAGEOF ADMIXTURES Basic Information Learning relatedto function QualityManagement Discipline Civil Construction Package Civil Quality Learning Details Description To facilitate approval of admixture inconcrete mix, the typical dosage and possible detrimental effectsof underandoverdosage isrequired. The minimumandmaximumdosage shouldbe knownpriortocarry out concrete mix designsatsite. Root Cause GenerallyinDatasheetsof admixture the minimumandmaximum value isgivenas1.0 % to 2.0 %.But it mayvarieswiththe Grade and Brand of cementand shouldbe determinedpriortoconcrete trials. SolutionAdopted Testthe consistencyof cementadmixture slurrywithMarshcone isas follows: -Mix the cementmortar withw/c0.32 to .035 -Watershouldmixedinsteps70% of watershall be mixedincement inbeginningandrest30% wateris mixedalongwithadmixture. -Cementadmixture slurrythenpouredthroughMarshCone andtime will be measuredinseconds. -The procedure isrepeatedwithincrementof admixture havingsame w/c ratio. -Graph isplottedwithtime (Yaxis) vsdosage of admixture ( Xaxis). -Saturationpointandlimitsof mixingdosage of admixtureinconcrete isdeterminedfromthistest. Learning Recommendedoptimal dosage isnottoexceedthe saturationpoint foundfromthe Marsh Flow TestData. Excessive dosage beyond saturationpointmayleadto segregationproblem. Impact These valuesare beneficial indesignof everygrade of concrete mix and limitsthe hitandtrial methodtofindoptimumdosage of admixture in concrete, Hence savestime. RecommendedPractices Do’s Mix the cementmortarwithw/c 0.32 to .035 Don’t Don’tmix 100 % of waterwhile mixingincementin beginning Attachment And References :Site Civil QualityManual,Docno.LTPQ-S-MNL-C-001,Revno.01
- 2. Attachment Brand ofCement:Ultratech Brand of Admixture :FosrocSP 500 Observations Sr No W/C Wt of Admixture Wt of cement % Admixture of cement Time of flow gms. gms sec. 1. 0.33 4.0 600.0 0.67 162 2. 0.33 5.0 600.0 0.83 132 3. 0.33 6.0 600.0 1.00 110 4. 0.33 7.0 600.0 1.17 106 5. 0.33 8.0 600.0 1.33 111 6. 0.33 9.0 600.0 1.50 124 7. 0.33 10.0 600.0 1.67 145 8. 0.33 11.0 600.0 1.83 170 0 20 40 60 80 100 120 140 160 180 0.00 0.50 1.00 1.50 2.00 % age admixture of cement Timetakeninseconds
- 3. Saturation Point:Here thesaturationpointisfoundat1.1 %. Hence the dosage of admixture cannotbe increasedabove than1.1% insite concrete.Compare the marshcone dosage withdesignmix dosage.If the difference ismore than0.15-0.2%,call/checkwiththe manufacturer.