material laboratory.docx

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Laboratory 1 – Test on fresh concreteMaterial and Concrete Technology

(CON3312)

Higher Dilo!a in Ci"il #ngineering#$11%1&1'1NC11 $ro D

$ro !e!bers*ON$ H+N$ ,+ 1-&331%12

L+.N$ /HON$ ,+N

CH.N CH+ L#ON$ 1-&%0&-L+ CHN *+T 1-&314%4



II Procedurese the follo5ing !i6 roortion to reare a batch of freshconcrete Ce!ent'474 8g 2& !! agg'107 8g9ater'%7% 8g 1& !! agg'474 8g

:ine agg'1372 8g

9eight correct a!ont of aggregate and ce!ent7 Mi6 the! in drythoroghly7



9eight correct a!ont of 5ater; add it into the !i6tre and !i6

the! thoroghly7



Hold the cone <r!ly on the base late; then <ll

the cone by 3 e=al layers of fresh concrete7 Ta! each layer by 2-ti!es 5ith a ta!ing rod7 >e sre to enetrate to the re"ios layer5hen ta!ing7

Clean a5ay concrete sillage 5ith a sa5ing and rolling !otion of theta!ing rod7 Lift the cone slo5ly and steadily in <"e to ten seconds7+f the sl!ed concrete shear or collase; the test !st be restartedfro! the <rst ste7 +f tre sl! is achie"ed; contine to the ne6tste7



+n"ert the cone and stand it beside the sl!ed concrete7 Lay theta!ing rod across the cone and abo"e the sl!ed concrete7

?ecord the height di@erent bet5een the nderside of the rod andthe to of the sl!ed concrete to the nearest - !!7

Clean the !old and roerly tighten the bolts7 #"enly aly a thin<l! of !old oil on the inside srface of the !old7 :ill the !old5ith fresh concrete to a thic8ness of abot -& !!7 se aco!acting bar to co!act the concrete7 ?efer to the table belo5for the !ini!! of stro8es7 ?eeat ste 3 and ste % ntil the!old is fll7 Le"el the to 5ith a tro5el7 Co"er the !old 5ith a



lastic sheet or Aerse6 co"er7

.dd &74 8g of 5ater !ore into the !i6tre and !i6 the! thoroghly

again7



Measre the three di!ensions (l1; l2 and l3) of the cbe 5ith thecalier727 9eight the stirr i!!ersed in 5ater or set the balance readingBero737 Alace the concrete on the stirr and flly i!!ersed it in 5ater7%7 ?ecord the aarent !ass of the seci!en 5ith correction for theaarent !assof the e!ty stirr (!5)7-7 9ie the seci!en to re!o"e the srface 5ater and 5eight it inair (!a)77 Aerfor! the test once for each test seci!en7



Clean the srface of the cbe 5ith a to5el7 Dra5 lines on t5ooosite faces (not the tro5elled face) of the cbe sch that eachface is sbdi"ided into nine e=al s=ares7 Careflly lace the cbein the co!ression !achine sch that B The tro5elled face is"ertical; B The faces 5ith lines dra5n are "ertical and accessible

fro! the front or rear of the co!ression !achine7 .ly loading of1-4 – 22- 8N to hold the cbe7 :or each face; test 5ith the ch!idtrebond ha!!er on the centre of each s=are and record therebond n!ber



+dentify and re!o"e the cbe seci!en fro! cring tan87 9ie o@e6cess 5ater fro! seci!en srfaces 5ith a iece of cloth7 ?ecordthe date of the seci!en cast7 ?ecord the cbe if it is ha"ing anedge bro8en for 2&!! or !ore in any direction7 Alace the cbe incbe chec8ing ig 5ith the tro5elled srface 5ards7 Chec8 thecontract bet5een the cbe and the ib 5ith the feeler gages7 Trnthe cbe throgh &E and reeat the chec87 Measre the length(l1); 5idth (l2) and height (l) bet5een the three airs of oosingfaces of the cbe 5ith a calier7 9eigh the cbe7 Alace the cbe onthe centre of the lo5er laten 5ith the tro5elled srface of the cbe"ertical7 .ly the test load steadily so that the stress is increasedat a rate 5ithin the range of &72 NF!!2 er second to &7% NF!!2er second ntil no greater load can be sstained7 ?ecord the!a6i!! load alied (:) to the cbe seci!en7



Alace the test seci!en in the centering ig 5ith ac8ing stris andloading ieces7 Alace the ig in the co!ression !achine carefllyso that the sace!en is located centrally7 .lied the load steadilyand 5ithot shoc8 sch that the stress is increased at a rate 5ithinthe range of &7&2 MAaFs to &7&% MAaFs7 ?ecord the !a6i!! loadattained (:)7

Careflly lace the seci!en in the Ge6ral loading de"ice schthat B the tro5elled face is "ertical; B the seci!en is in the centreof the loading de"ice; and B the longitdinal a6is of the seci!en isat right angle to the rollers7 .lied the load steadily and 5ithotshoc8 sch that the stress is increased at a rate 5ithin the range of&7&3 MAaFs to &7& MAaFs7 ?ecord the !a6i!! load attained7(:ailres otside the !iddle one'third of the distance bet5een the

sorting rollers shall render the test in"alid7)



:irst Cbe (nor!al)Date Cast: 2&1-'11'11 Age: 24 daySlump: 30!! water cementratio:0.5Appearance: da!aged corner

Dimension: l ₁ 1%742!!lI1-&70!! lJ1-&7!!Weight in air: 4&71g Weight in

water: %gMaximum load attained: 123*NDensit determined ! dimension: 23-72% 8gF!3

Densit determined ! water displacement: 2337%3& 8gF!3

Compressi"e strength: 55.#$ NF!!2%ailure Pattern %

econd Cbe(#6tra HIO)Date Cast: 2&1-'11'11 Age 24 daySlump: 140!! water cement ratio:0.5&Appearance: da!aged cornerDimension: l ₁ 1%71!! lI1-&730!! lJ1-&7-0!!Weight in air: 0%27-g Weight in water: %--70gMaximum load attained: 43%74*NDensit determined ! dimension: 23-37-02 8gF!3

Densit determined ! water displacement: 2303712% 8gF!3

Compressi"e strength: '(.)'$ NF!!2

%ailure Pattern: 1Which cu!e has higher strength* Wh its strength is higherthan another one*:irst Cbe strength higher than the second cbe (#6tra H2O);becase The !ore the 5Fc ratio is increased (that is; the !ore 5aterthat is added for a <6ed a!ont of ce!ent); the !ore the strengthof the reslting concrete is redced7 This is !ostly becase adding!ore 5ater creates a dilted aste that is 5ea8er and !oresscetible to crac8ing and shrin8age7 hrin8age leads to !icro'crac8s; 5hich are Bones of 5ea8ness7 Once the fresh concrete islaced; e6cess 5ater is s=eeBed ot of the aste by the 5eight of

the aggregate and the ce!ent aste itself7 9hen there is a largee6cess of 5ater; that 5ater bleeds ot onto the srface7 The !icrochannels and assages that 5ere created inside the concrete toallo5 that 5ater to Go5 beco!e 5ea8 Bones and !icro'crac8s7

Schmidt +e!ound ,ammer:?ebondn!ber Concrete

strength

3%3&

%2%%

%%%4

333

%1%2

%1%2

%2 %%

%& %&

34 30



#sti!ated co!ressi"e strength %&.ctal co!ressi"e strength --7%

-ensile splitting strength:."erage !easred dia!eter; d1-&72!!."erage !easred length; L27-32-!!Ma6i!! load attained; :2-170*N Tensile slitting strength 37-&2 NF!!2

:le6ral strength9idth of the seci!en; dK1&&7!!Deth of the seci!en; dI1&&70!!acing of the lo5er rollers; L3&&!!Ma6i!! load attained; :1-7%*N :le6ral strength %7030 NF!!2

!ser"ation and In/erence

9hat is the e@ect of the =antity of !i6ing5ater on the 5or8ability of fresh concrete

+n general; 5ith increasing 5Fc the strength sholddecrease as !ore 5ater 5ill reslt in higher (caillary)orosity7 Ths holds at least for the co!!only sed 5Fc;e"en the lo5 ones (yo can i!agine that for the "ery lo55Fc the strength 5old decrease again as the ce!entcold not hydrate sciently; bt sch lo5 5Fc are hardlye"er sed)7 There e6ist e!irical relationshis to relate5Fc to strength bt they are de<netely not robst7

.s for the cosistency; this deends on so!e additionalfactors7 :Or the "ery sti@ consistency there !ay be a lot of



large air soc8ets entraed that cold be considered asdefects and therefore decrease the strength7 :ro! thisersecti"e; !ore Gid concrete shold lead to better<lling of the !olds and easier e"acation of (other5ise)

entraed air7 On the other hand; too Gid consistency!ay lead to segregation of the !i6tre and roble!s 5ithstrength7 .lso; too !ch lasticiBer added to obtaincertain consistency !ay lead to slo5er hydration andtherefore slo5er de"elo!ent of strength7

9hich cbe; the <rst or the second one; yothin8 is stronger; 5hy

The <rst one becase the 5ater ce!ent ratio is betterthan the second one7

material laboratory.docx

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