Concrete Curing:Concrete Curing: Plastic Plastic Shrinkage Cracking, Bleeding, Shrinkage Cracking, Bleeding, Evaporation, and TemperatureEvaporation, and Temperature

Jennifer A. Distlehorst Cliff HobsonJennifer A. Distlehorst Cliff Hobson

Dave Meggers John WojakowskiDave Meggers John Wojakowski

Kansas DOTKansas DOT

Plastic Shrinkage CrackingPlastic Shrinkage CrackingAnalysis of the termAnalysis of the term

Plastic - capable of continuous and Plastic - capable of continuous and permanent change in any direction permanent change in any direction without breaking apartwithout breaking apart

Cracking - breaking apart or splittingCracking - breaking apart or splitting

Plastic Shrinkage CrackingPlastic Shrinkage Cracking

Plastic Shrinkage Cracking Plastic Shrinkage Cracking FactorsFactors

Evaporation Rate - Evaporation Rate - Menzel, 1954; Lerch,1957Menzel, 1954; Lerch,1957 Combination of 4 Factors - Concrete and Air Combination of 4 Factors - Concrete and Air

Temperatures, Humidity and Wind Speed Temperatures, Humidity and Wind Speed Critical Value from Lerch, 1957 – 0.2 lb/sq ft/hrCritical Value from Lerch, 1957 – 0.2 lb/sq ft/hr

Bleeding of the ConcreteBleeding of the Concrete Are Today’s Concretes Still the Same? Similar?Are Today’s Concretes Still the Same? Similar? New Value for regular, let alone high New Value for regular, let alone high

performance concrete?performance concrete?

Bleed Test of Concrete Bleed Test of Concrete ASTM C 232ASTM C 232

Bleeding of Concrete and Loss Bleeding of Concrete and Loss of Water at Various of Water at Various Evaporation RatesEvaporation Rates

Cum

ula

tive w

ate

r ble

d o

r evapora

ted,

lb/f

t2

0.2

0.3

0.4

0.5

0.6

0.1

time in hours0 0:43 1:26 2:09 2:52

0.2

0.1

0.05

0.15

bleed water

Laboratory Concrete, Air Entrained

I-635 Example - Hand I-635 Example - Hand PlacementPlacement

0.2

0.3

0.4

0.5

0.6

0.1

bleed water

0.1

Measured evaporation rate 0.07 lb/sq.ft/hr

Cum

ula

tive w

ate

r ble

d o

r evapora

ted,

lb/f

t2

Du

mp

10:

35

Co

nso

lidat

ion

10:

40

Tin

ing

10:

45

Cu

rin

g C

om

po

un

d 1

0:50

time of day10:30 11:00 11:30 12:00

92-95 F,

ADJACENT CURED CONCRETE 106 F 0.

2

I-70 Example -Slip FormedI-70 Example -Slip Formed

0.2

0.3

0.4

0.5

0.6

0.1

bleed water

0.1evaporation 0.12 lb/sq.ft/hr

Cum

ula

tive w

ate

r ble

d o

r evapora

ted,

lb/f

t2

Du

mp

2:0

5

time of day2:00 2:30 3:30 4:00

Co

nso

lidat

ion

2:1

0

Tin

ing

3:0

0

Cu

rin

g C

om

po

un

d 3

:40

3:00

0.2

Louisburg Example - Slip Louisburg Example - Slip FormedFormed

0.2

0.3

0.4

0.5

0.6

0.1bleed water

0.1

0.13 lb/sq.ft/hr

Cum

ula

tive w

ate

r ble

d o

r evapora

ted,

lb/f

t2

Du

mp

1:1

7

time of day1:30 2:30 3:00

Tin

ing

2:1

0

Cu

rin

g C

om

po

un

d 2

:18

2:00

0.2

I-635 Bridge ExampleI-635 Bridge Example

0.2

0.3

0.4

0.5

0.6

0.1

bleed water

0.1

0.05 lb/sq.ft/hr

Cum

ula

tive w

ate

r ble

d o

r evapora

ted,

lb/f

t2

Du

mp

8:5

0

time of day9:00 10:00 10:30

Bu

rlap

10:

45

9:30

Conso

lidati

on

9:0

0

Grade 30, Field Concrete

0.2

If the evaporation rate is If the evaporation rate is greater than the bleeding greater than the bleeding

rate why isn’t there a lot of rate why isn’t there a lot of plastic shrinkage cracking in plastic shrinkage cracking in

our concrete?our concrete? Stiffer, cohesive concrete (used in slip form Stiffer, cohesive concrete (used in slip form

paving & bridge decks) has some tensile strength paving & bridge decks) has some tensile strength to resist the force imposed by the surface tension to resist the force imposed by the surface tension of waterof water

Water reducers used in these mixtures reduce the Water reducers used in these mixtures reduce the surface tension of the watersurface tension of the water

KDOT Bridge Deck Curing KDOT Bridge Deck Curing Specification 90M/R-91-R13*Specification 90M/R-91-R13*

Measure the evaporation rate on the Measure the evaporation rate on the bridge deck regularlybridge deck regularly

Use monomolecular/precure immediately Use monomolecular/precure immediately after the bridge deck finisherafter the bridge deck finisher

Fog immediately behind the tining floatFog immediately behind the tining float Produce a gloss to a semi-gloss sheen Produce a gloss to a semi-gloss sheen

without water runoffwithout water runoff

KDOT Bridge Deck Curing KDOT Bridge Deck Curing Specification 90M/R-91-R13*Specification 90M/R-91-R13*

Apply curing compound to the damp Apply curing compound to the damp wearing surfacewearing surface

Cover with wet burlap for seven daysCover with wet burlap for seven days Use soaker hosesUse soaker hoses Polyethylene sheeting is not allowed Polyethylene sheeting is not allowed

until the evening of the day following until the evening of the day following placement if the temperature is placement if the temperature is forecast to be above 50 Fforecast to be above 50 F

Temperatures of a Slab Temperatures of a Slab BridgeBridge

60

70

80

90

100

110

120

130

140

06/

26/2

003

08:

22

06/

26/2

003

13:

02

06/

26/2

003

17:

42

06/

26/2

003

22:

22

06/

27/2

003

03:

02

06/

27/2

003

07:

42

06/

27/2

003

12:

22

06/

27/2

003

17:

02

06/

27/2

003

21:

42

06/

28/2

003

02:

22

06/

28/2

003

07:

02

06/

28/2

003

11:

42

06/

28/2

003

16:

22

06/

28/2

003

21:

02

06/

29/2

003

01:

42

06/

29/2

003

06:

22

06/

29/2

003

11:

02

06/

29/2

003

15:

42

06/

29/2

003

20:

22

06/

30/2

003

01:

02

06/

30/2

003

05:

42

06/

30/2

003

10:

22

06/

30/2

003

15:

02

06/

30/2

003

19:

42

07/

01/2

003

00:

22

07/

01/2

003

05:

02

07/

01/2

003

09:

42

07/

01/2

003

14:

22

07/

01/2

003

19:

02

07/

01/2

003

23:

42

07/

02/2

003

04:

22

07/

02/2

003

09:

02

07/

02/2

003

13:

42

Tem

per

atu

re,

F

Concrete

Air

Top button at the haunch in a middle pier

AirN N N N N N N = noon

PLASTIC PLACED

15 F

Evaporation retarder applied Evaporation retarder applied immediatelyimmediately

E. Holt, Concrete International , Sept 2000

E. Holt, Concrete International , Sept 2000

(0.1 psf = 0.02 in)

Water applied after 1 hourWater applied after 1 hour

E. Holt, Concrete International , Sept 2000

(0.2 psf = 04 in)