Determining the rime setting of portland cement

1. DETERMININGTHETIMEOF
SETTINGOFPORTLAND
CEMENT

2. WILFREDO B. BANIQUED- BSCE CHEMISTRY FOR CIVIL ENGINEERS
TABLEOFCONTENTS
-INTRODUCTION -APPARATUS
-WHATISSETTINGTIME? -PROCEDURE
-WHATISTHEINITIALSETTINGTIMEOFCEMENT? -FIGURE
-WHATISTHE FINALSETTINGTIMEOFCEMENT? -OBSERVATIONSTABLE
-SIGNIFICANCE OFINITIALAND FINAL SETTINGTIMEOFCEMENT -CALCULATIONS
-AIM -RESULTS

3. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
DURINGCONSTRUCTION USING CONCRETE, CEMENT PASTE, TRANSPORTATION,
PLACING,COMPACTING ANDFINISHING. DURINGTHIS TIMECONCRETE MORTAR, CEMENT PASTE
SHOULD BEINPLASTIC CONDITION ANDSHOULD NOTHARDEN ANDIT ISMANDATORY THATONE
SHOULD USE THECONCRETE BEFORE ITSTARTS TOLOOSE ITS PLASTICITY.
SO HOWSHOULD SOMEONE KNOWHOWLONGISCONCRETE WORKABLE?
AND HOWMUCH TRAVELTIMEIS PERMITTED FORCONCRETE?
WELLITSSETTING TIMETHATTELLSUSHOWLONGCONCRETE ISGOING TOBE WORKABLE. NOW
THEQUESTION WHATIS THESETTING TIMEOF CEMENT?
INTRODUCTION

4. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
SETTINGTIMEOFCEMENT
SETTING TIMEOF CEMENT IS THEREQUIREDSTIFFENING OF
CEMENT PASTE TOADEFINED CONSISTENCY. SETTING TIME
ISTHENCLASSIFIED INTOTWOTYPES, INITIALSETTING TIME
AND FINALSETTING TIMEBASED ONPLASTICITY.

5. WHATISTHEINITIALSETTINGTIMEOF
CEMENT?
TIMEELAPSED BETWEEN WATERADDED ANDTIMEATWHICH CEMENT PASTE JUSTSTARTS
LOOSING ITS PLASTICITY ISCALLED ASINITIALSETTING TIMEOF CEMENT. NORMALLYFOROPC
INITIALSETTING TIMEIS30MINUTES BUTSHOULDNOTBEMORE THAN60MINUTES.

6. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
WHATISTHEFINAL SETTINGTIME
OFCEMENT?
TIMEELAPSED BETWEEN WATERADDED ANDTIMEATWHICH
CEMENT PASTE COMPLETELY LOOSE ITSPLASTICITY ISCALLED
AS FINALSETTING TIME. NORMALLYFOROPC FINALSETTING TIME
IS10HOURS ANDNOTMORE THANTHAT.

7. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
SIGNIFICANCEOFINITIALANDFINALSETTINGTIMEOF
CEMENT
SETTINGTIMEPLAYS AVITALROLEINANY KINDOFCONSTRUCTIONWORK.CONCRETESHOULDSETTOOEARLY
NORTOOLATE.CONCRETESETBEFOREPLACING RESULTSINRIGIDITYBEFOREPLACINGORLOWWORKABILITY.IN
THECONVERSESCENARIO,LATE SETTINGWILLRESULTININADEQUATE STRENGTH ATDESIREDAGE.
INITIALSETTINGTIME ISTIMESPAN BETWEENTHEADDITIONOFWATERAND THETIMEWHENCEMENT
PASTESTARTS TOLOOSEITSPLASTICITY.THAT’SWHYINITIALTIMESETTINGTESTISIMPORTANTFOR
TRANSPORTATION, PLACING,COMPACTINGANDCURINGOFCEMENTCONCRETE.
FINAL SETTINGTIMEISTHETIMESPAN BETWEENWATERADDED AND THETIMEWHENCONCRETECOMPLETELY
LOOSEITSPLASTICITY.FINAL SETTINGTIMEOFCEMENTHELPSINTHE SAFE REMOVAL OFTHE SCAFFOLDING.

8. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
APPARATUS
VICATAPPARATUS
NEEDLES FORTEST
WEIGHTBALANCE
STOPWATCH

9. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
PROCEDURE
1.)FIRST, TAKE 300GRAMS OFCEMENT INAPANANDMIXWITHTHE KNOWN PERCENTAGE
OFWATERBYWEIGHT OFCEMENT, ASSUME STARTING FROM 26% AND THENINCREASE IT
BY 2%UNTILTHENORMALCONSISTENCY IS ACHIEVED.
PREPARATION:
2.) WITHCONTINUOUS MIXING.
3.) START THESTOPWATCH AS SOON ASTHE WATERADDED TOTHECEMENT.
4.) NOWFILLTHE PASTE INTOTHEMOULDWITHNON-POROUS PLATEBELOW.LEVELAND
SMOOTHEN THESURFACE OF THEPASTE

10. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
PROCEDURE
1.)PLACE THEMOULDINTO THEVICUT APPARATUS ALLOWTHENEEDLE TOTOUCH THESURFACE OF
PASTE ANDTHENQUICKLY RELEASE ALLOWINGITTOFREELY SINKINTOPASTE.
INITIALSETTINGTIMETEST:
2.) REPEATTHEPROCEDURE UNTILTHENEEDLEWHEN RELEASE FAILS TOPENETRATE
THEBLOCK BEYOND 5mmFROM THEBOTTOMOF THEMOULD.
3.) RECORD THIS TIMEANDTHIS SHALLBE THEINITIALSETTING TIME.

11. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
PROCEDURE
1.)REPLACE THENEEDLEBYFINALSETTING TIMENEEDLE.
FINAL SETTINGTIMETEST:
2.) THECEMENT SHALLBE CONSIDERED ASFINALLYSET WHEN, UPON APPLYINGTHE
NEEDLE GENTLYONTHESURFECE OFTHETEST BLOCK, THENEEDLE MAKES AN
IMPRESSION AND FAILSTOPENETRATE.
3.) THETIMEELAPSED BETWEEN THETIMEWHENWATERISADDED AND THE THETIMEATWHICHTHE
NEEDLE MAKES ANIMPRESSION ONTHESURFACE OFTHETEST BLOCK SHALLBECONSIDERED AS
FINALSETTING TIMEOF CEMENT SAMPLE..

12. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
FIGURE
3.)

13. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
OBSERVATIONTABLE
SR. NO. SETTING TIME PENETRATION(mm)
1.
2.
3.
4.

14. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
CALCULATIONS
INITIALSETTINGTIMEFORMULA
INITIALSETTING TIMET2-T1
FINALSETTINGTIMEFORMULA
FINALSETTING TIMET3-T1
T1=TIMEOFADDITION OFWATER TOCEMENT
T2=TIMEWHEN THENEEDLE RELEASED FAILS
TOPENETRATE THEBLOCK BEYOND 5mmFROM
THEBOTTOMOF THE MOULD.
T3=THETIMEATWHICHTHENEEDLE MAKES AN
IMPRESSION ON THESURFACE OF THETEST
BLOCK.

15. THE CRYSTAL LATTICE IS A
REPEATING NUMBER OF
IDENTICAL UNITS, CALLED
UNIT CELL.
CALCULATIONS
RESULTS
INITIALSETTING TIMEOF PORTLAND CEMENT IS------
FINALSETTING TIMEOF PORTLAND CEMENT IS------
THANKYOU