High Molecular Weight Methacrylate Crack

Penetration Study

Michael J. Lee

Structure Maintenance and Investigations

Robert A. Reis

Materials, Engineering and Testing Services

A Brief History

• Early 1980’s Caltrans experiments with resins to repair

cracks by gravity or capillary action.

• High Molecular Weight resin (HMWM), with viscosity

<25 cps, is determined best suited for the job.<25 cps, is determined best suited for the job.

• 1984 Caltrans writes HMWM bridge deck treatment

specification .

• Flooding bridge decks with HMWM to repair pattern

deck cracks becomes a standard practice.

• Bridge Preservation gets a funding boost.

• 1998 Caltrans treats 30 bridges with HMWM. 1999

the number of bridges jumps to 300.

• Caltrans spends over $90 million per year on bridge

preservation activities. Deck treatment is a significant preservation activities. Deck treatment is a significant

portion of this amount.

• Are we getting our monies worth?

Let’s find out.

Study Overview

• Determine the effectiveness of high molecular weight methacrylate to penetrate concrete bridge deck cracks.

• Starting in 2007, core every bridge deck treated with HMWM.HMWM.

• 2 ea. – 2”x5” cores. 8 cores max. per bridge. 1200 cores are collected.

• 200 randomly selected cores are evaluated.

Here’s what we found.

Concrete Core Operation

Crack Width Distribution

9285

60

80

100

Nu

mb

er

of

Sa

mp

les

14

6

0

20

40

0.0 to 0.2mm 0.3 to 0.6mm 0.7 to 1.0 mm 1.1 to 2.0 mm

Crack Width (mm)

Nu

mb

er

of

Sa

mp

les

Crack Width Distribution

0.0 to 0.2mm

47%

0.7 to 1.0 mm

7%

1.1 to 2.0 mm

3%

0.3 to 0.6mm

43%

Crack Depth Distribution

59

66

40

50

60

70

Nu

mb

er

of

Sa

mp

les

28

19

25

0

10

20

30

40

0 - 25 mm 26 - 50 mm 51 - 75 mm 76 - 100 mm > 100 mm

Crack Depth (mm)

Nu

mb

er

of

Sa

mp

les

Crack Depth Distribution

0 - 25 mm

14%

76 - 100 mm

10%

> 100 mm

13%

26 - 50 mm

30%

51 - 75 mm

33%

Percent Penetration Distribution

(without considering depth of crack)

121

80

100

120

140

Nu

mb

er

of

Sa

mp

les

812 13

1810

0

20

40

60

80

> 90% 70% - 90% 50% - 70% 30% - 50% 10% - 30% <10%

Percent Penetration

Nu

mb

er

of

Sa

mp

les

Full Depth Penetration

(considering depth of crack)

58%64% 64% 63% 61%

60%

80%

100%

Pe

rce

nt

of

Sa

mp

les

0%

20%

40%

< 35 mm < 50 mm < 75 mm < 100 mm < 120 mm

Depth of Crack (mm)

Pe

rce

nt

of

Sa

mp

les

Questions?a. Does bridge age make a difference with a. Does bridge age make a difference with

penetration?

Answer: No.