Shrinkage Test- Result 90 Days

8/6/2019 Shrinkage Test- Result 90 Days

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BATULAWA BRIDGE EXTENSIONALSON CHIN

SHRINKAGE TEST

INTRODUCTION

1. This paper descripts the results of an experimental investigation carried out to determinethe shrinkage of the high strength concrete.

2.

To compare the shrinkage strain for in order to choose the better type of concrete incontrol the shrinkage crack of concrete.

Contractor : Hart Builders S/BConsultant : TCS Consultant

Concrete Supply : Hailek Concrete S/B

Test Periods : 8th

March3rd

June 2011

PROBLEM IDENTIFICATION

Plastic shrinkage normally occurs after the fresh concrete place during the first few days. When

the water evaporates from the surface of freshly placed concrete faster than it is replaced bybleed water, the surface concrete shrinks. Paste of rich mixes such as high strength concrete will

be more susceptible to plastic shrinkage than normal concrete.

The drying shrinkage crack appears as the inevitable especially the under side of the desk slab.It seems common defects for a bridge after long term. It happens after the concrete had already

attained its final set and a good portion of the chemical hydration process in the cement gel has

been accomplished.

Both shrinkages will be measure during this experiment. The dial gauge reading will be taken for

the each day for 90 days. The experimental started since 8th March 2011 and end at 3rd June

2011. The changes in length of each specimen were calculated from the different of final andinitial dial gauge readings. Then shrinkage strain was calculated.

EQUIPMENTS

Dial Gauge (X 0.01mm) 2 nos

Frame 1 noPins 2 nos

Test Piece (100mmX 100mm X 600mm) 2 nos


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SHRINKAGE TEST

EXPERIMENTAL PROGRAMME

Shrinkage of concrete was measured with the help of Shrinkage Apparatus as shown below.

Then original Concrete beams specimens of 75mm x 75mm in cross section and 280mm length

had changed to 100mm x 100mm x 600mm in order scale up the shrinkage rate.

Then specimens were cast with 2 different concrete mixes. Both specimens are pump mix design

with Grade 40 with high workability. But one of it mixed with Daratard 45 as the retarder toslow down the hydration of concrete.

Shrinkage measuring apparatus along with specimen

Dial gauge

Specimen

Pin

600mm

100mm


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Pins were embedded at both ends of the specimens to hold them in the shrinkage apparatus.

Specimens were cured in water for 7 days before testing for shrinkage. Initial readings of thespecimens were taken with the help of dial gauge attached to the apparatus. Then the specimens

were air dried for 90 days. Again the final reading of each specimen was taken after the specified

period of air drying.

The change in length of each specimen was calculated from the difference of final and initial dial

gauge readings. Then the shrinkage strain was calculated and compared with the prediction of

the shrinkage strain in theory.

COMPOSIION OF MIX

Material

0.3m

Pump Mix P40(Mix 1)

Pump Mix P40(with retarder) (Mix 2)

Cement (kg) 14.1 14.1

Water (kg) 3.64 3.65

Total Aggregate (kg) 51.59 51.54

Fine Agg.(kg) 20.59 (39.33%) 20.59 (39.29%)

Coarse Agg.(kg) 30.00 (60.67%) 30.00 (60.73%)

Daracem 100 (L) 0.169 0.169

Daratard 45 (L) - 0.017

Density of concrete (kg/m) 2317.8 2317.01Slump Obtained (mm) 120 120

Table 1: Composition of design mix for deck slab concreting works.


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Mix Design Change in length L (0.01 mm) after days

Days 1 day 2 3 4 5 6 7 8 9 10 11 12 13 14 15

without Daratard 45 - - 0.08 0.10 0.04 0.03 0.02 0.00 -0.02 -0.04 -0.06 -0.04 -0.11 -0.13 -0.08

with Daratard 45 - - 0.26 0.34 0.43 0.43 0.51 0.50 0.57 0.64 0.65 0.63 0.72 0.74 0.75

Days 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

without Daratard 45 -0.07 -0.06 -0.03 0.02 0.02 0.01 0.00 -0.01 -0.01 0.01 0.03 0.06 0.03 0.05 0.04

with Daratard 45 0.76 0.79 0.82 0.81 0.85 0.86 0.87 0.88 0.89 0.88 0.87 0.90 0.91 0.92 0.93

Days 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

without Daratard 45 0.03 0.06 0.09 0.10 0.06 0.08 0.05 0.07 0.08 0.09 0.10 0.08 0.10 0.10 0.09

with Daratard 45 0.91 0.93 0.90 0.94 0.93 0.93 0.92 0.94 0.92 0.89 0.93 0.93 0.94 0.95 0.91

Days 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

without Daratard 45 0.12 0.11 0.08 0.08 0.12 0.11 0.10 0.11 0.00 -0.05 -0.05 0.04 0.05 0.06

with Daratard 45 0.94 0.9 0.93 0.94 0.94 0.95 0.94 0.95 1.02 1.02 0.96 1.00 0.99 0.97

Days 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75


with Daratard 45 0.93 0.95 0.97 0.97 1.00 0.98 0.99 1.00 0.97 0.95 0.96 0.95 0.98 0.99 0.98

Days 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

without Daratard 45 0.13 0.14 0.11 0.10 0.12 0.13 0.13 0.15 0.15

with Daratard 45 0.99 0.98 0.99 0.99 1.00 0.99 0.96 0.98 0.97

Table 3: Test results of shrinkage of concrete Change of length (0.01 mm) after days


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Mix Design Shrinkage strain, (L/L)x 10 after days

Days 1 day 2 3 4 5 6 7 8 9 10 11 12 13 14 15

without Daratard 45 - - 1.325 1.656 0.662 0.497 0.331 0 -0.33 -0.66 -0.99 -0.66 -1.82 -2.15 -1.32

with Daratard 45 - - 4.312 5.638 7.131 7.131 8.458 8.292 9.453 10.61 10.78 10.45 11.94 12.27 12.44

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

without Daratard 45 -1.15894 -0.99 -0.5 0.331 0.331 0.166 0 -0.17 -0.17 0.166 0.497 0.993 0.497 0.828 0.662

with Daratard 45 12.6036 13.1 13.6 13.43 14.1 14.26 14.43 14.59 14.76 14.59 14.43 14.93 15.09 15.26 15.42

31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

without Daratard 45 0.49669 0.993 1.49 1.656 0.993 1.325 0.828 1.159 1.325 1.49 1.656 1.325 1.656 1.656 1.49with Daratard 45 15.0912 15.42 14.93 15.59 15.42 15.42 15.26 15.59 15.26 14.76 15.42 15.42 15.59 15.75 15.09

46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

without Daratard 45 1.98675 1.821 1.325 1.325 1.987 1.821 1.656 1.821 0 -0.83 -0.83 0.662 0.828 0.993

with Daratard 45 15.5887 14.93 15.42 15.59 15.59 15.75 15.59 15.75 16.92 16.92 15.92 16.58 16.42 16.09

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75


with Daratard 45 15.4229 15.75 16.09 16.09 16.58 16.25 16.42 16.58 16.09 15.75 15.92 15.75 16.25 16.42 16.25

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

without Daratard 45 2.15 2.32 1.82 1.66 1.99 2.15 2.15 2.48 2.48

with Daratard 45 16.42 16.25 16.42 16.42 16.58 16.42 15.92 16.25 16.09

length , L for mix 1 = 604mm length , L for mix 2 = 603mm

+ value indeicated shrinkage & - value indicated expansion for the concrete

Table 4: Test results of shrinkage strain of concrete after days


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Figure 1 : Variation of shrinkage strain of concrete with Mix 1 & Mix 2 versus age (days)

-5.00

0.00

5.00

10.00

15.00

20.00

0 10 20 30 40 50 60 70 80 90 100

SHRINKAGESTRAIN(

L/L)x10

afterdays

DAYS

TEST RESULT OF THE SHRINKAGE WITH MIX 1 (WITHOUT DARATAD 45) AND MIX 2

(WITH DARATARD 45)

LENGTH OF SPECIMEN 600mm

Mix 1

Mix 2

Poly. (Mix 1)

Poly. (Mix 2)


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DISCUSSION OF RESULTS

This discussion will be separated to 2 parts, mainly discussed on the plastic shrinkage and drying

shrinkage crack. Results shown from day first to 7th

days been observed for the plastic shrinkage

until the final set observed. Then remaining results shall use for extracting shrinkage strain for

drying shrinkage crack.

Mix 1 is the Pump mix with design of concrete strength G40 used of super plasticizer Daracem

100 and Mix 2 indicated the same design strength but use the admixture ( Daracem 100 andDaratard 45)

Part 1: Plastic Shrinkage crack (1 day to 7 days)From the results it is concluded that the shrinkage strain for Mix 1 decreases with time from then

day 1 to days 3 and it turned to negative value at days 4 to days 7, it mean then concrete shown

expansion with time after 3 days.

Mix 2 which added with Daratard 45 shown shrinkage increase with time from then 1 day to 7

days. The shrinkage strain was larger compare to mix 1.

The cement has higher-than-normal quantities of tricalcium aluminate (C3A) and calcium sulfate.Expansion is caused by the hydration of these materials. Expansion can occur if concrete is

cured by immersing in water. Daracem 100 allowed develops of early strength process hydration

during the 1st

3 days. Then water (H2O) need for the process hydration and after 3rd

day the water

is sucked into the concrete to counteract self desiccation and to swell and hydrate the CSHphases in Mix 1.

Cement chemist notation : C3S + H C-S-H + CH

Standard notation : Ca3SiO5 + H2O (CaO)(SiO2)(H2O)(gel) + Ca(OH)2Balanced : 2Ca3SiO5 + 7H2O 3(CaO)2(SiO2)4(H2O)(gel) + 3Ca(OH)2
http://en.wikipedia.org/wiki/Cement_chemist_notationhttp://en.wikipedia.org/wiki/Cement_chemist_notation


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Meanwhile Mix 2 with presents of admixture Daratard 45, the shrinkage strain increase with

time and gradually slower rate as show as figure 1

The retarder was used to slower the initial and final setting time of the concrete. For initial

setting, it extends the setting time by 2-3 hours at 21C to insure sufficient delivery, placement,

vibration or compaction time, such as in hot weather concreting transit mix concrete and pre-stressed concrete. Daratard 40 is also used in special applications, as in bridge decks where it

extends plastic characteristics of the concrete until progressive deflection resulting from

increasing loads is completed.For final setting, Retarders help to reduce the possibility of early dry-shrink cracking and reduce

the maximum temperature rise in mass concreting, by extending the heat-dissipation period.

The superplasticiser for the high workability concrete, Daracem 100 had used as the high range

water reducer specially formulated for extended slump life. It provides improved slump retention

in flowable concrete and it is ideal for low water cement ratio concrete designed for high earlycompressive and flexural strengths with exceptional workability and flow characteristics.

Daratard 45 retards the initial and final set of concrete. At the usual addition rate of 300 ml /100

kg cementitious material it will extend the initial setting time of portland cement concrete by 2 to

3 hours at 21C. Daratard 45 is used wherever a delay in setting time is required to insuresufficient delivery, placement, vibration or compaction time, such as in hot weather concreting

transit mix concrete and pre-stressed concrete

Daratard 45 is also used in special applications, as in bridge decks where it extends plasticcharacteristics of the concrete until progressive deflection resulting from increasing loads is

completed.

Part 2 Drying Shrinkage Test (7 days to 90 days)

Refer to the Figure 1: Variation of shrinkage strain of concrete with Mix 1 & Mix 2 versus age

(days).

Mix 1 (Without Daratard 45)The Shrinkage strain for days It is concluded that the shrinkage strain for Mix 1 increase with

time form 0.166E4 to 2.48E4 since the 25th

days to 88th

days which indicated the shrinkage after

the final setting. The overall shrinkage strain was desired and low compared to the Mix 2 whichachieves 16.09E4 at days 88th.

After the final set, the curing process occurs and the concrete mix begins to gain strength Themajority of chemical reactions between admixtures and other concrete components take place

during this phase. There should be a constant shrinkage rate with the slower or minor hydration

process.

Mix 2 (with Daratad 45)Mix 2 which added with Daratard 45 shown shrinkage increase with time from then 7 th day to

28th

days. Then high rate of shrinkage rate increase from 8.29E4 (8th

days) to 15.09E4 (28th

days)

It was believed, the retarder have slows the process of hydration and the shrinkage strain from28th days to 88th days only increase 1.00E4 which shows the concrete specimen achieved the

final set.


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CONCLUSIONOn the basis of test results the following major conclusions can be drawn:

1. The use of trial mix 1 (without Daratard 45) as approved design mix for deck slabconcreting works. (Attached with the Trial Mix Design)

2. After drying for 7 days, there is obvious difference between the shrinkage of Mix 1 andMix 2 made with Daratard 45, the add of retarder causes a high increase in the shrinkage

stains of Mix 2.

3. Both the shrinkage strain of the concrete increases with time from 28 th to 88th days butthe shrinkage strains of the Mix 2 (with Daratard 45) is higher then Mix 1 (withoutDaratard 45)

Shrinkage Test- Result 90 Days

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