Critical Freeze-Thaw Saturation Measurement of In-Service Masonry · 2016-12-15 · Field Sampling...

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Critical Freeze-Thaw Saturation

Measurement of In-Service Masonry

Buildings XIII Conference, Clearwater Beach, FL

December 5, 2016

R. Van Straaten, P.Eng., RDH Building Science Inc.

T. Trainor, M.A.Sc., RDH Building Science Laboratories

C. J. Schumacher, M.A.Sc., RDH Building Science Laboratories

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Greetings from the co-authors

Randy Van Straaten Trevor Trainor

at home, finishing his PhD arrives in Clearwater tomorrow

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Outline

Quick Review

Critical Freeze-Thaw Saturation

The Overall Process

Addressing Some Issues

Material Sampling Methods

Measurement Repeatability and Reproducibility

Growing Confidence in the Approach

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Freeze-Thaw Risk-Assessment

using Critical Saturation

A Quick Review

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The Critical Saturation Approach (to Freeze-Thaw)

Fagerlund (Lund University, 1970s)

No such thing as a freeze-thaw resistant material!

There is a critical degree of saturation , Scrit

Below Scrit

no freeze-thaw damage will occur regardless of

number of freeze-thaw cycles

Above Scrit

damage is measurable after only a few cycles

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The Critical Saturation Approach (to Freeze-Thaw)

Fagerlund (1977) porous, brittle materials below a certain

moisture content level can be freeze-thaw cycled repeatedly

without any measureable damage

∆𝑓𝑡=𝑙ft − 𝑙0𝑙0

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The Overall Process

Building

Assessment

Material

Sample

Collection

Hygrothermal

Simulation

Material

Property

Testing

Freeze-Thaw

Risk

Assessment

Using the Critical Saturation approach to assess the Freeze-

Thaw Risk associated with a real building

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Building Assessment (the Four Cs)

Construction

Condition

Concentrations

Connections

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Material Sample Collection

Represent range of important masonry materials on site

Number of different types of units?

› Face brick, infill brick, backup brick, block, tile

› Stones in the field, at trim, accents (e.g. quoins)

Number of samples of each type?

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Material Property Testing

Hygrothermal Simulations

Density

Liquid Water Uptake

Moisture Storage Fn

Reference MC

Free Water Saturation

Vacuum Saturation

Vapor Permeability

Freeze-Thaw Risk Assessment

Critical Degree of Saturation

-200

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.50 0.60 0.70 0.80 0.90 1.00

Mic

ros

tra

in G

row

th (

-)

Degree of Saturation (-)

Round 1

Round 2

Round 3

Round 4

Round 5

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Hygrothermal Simulations

Using multi-year weather data from the building locale

Model each different construction and exposure

Introduce moisture leaks to reflect connections

Parametric evaluation of moisture loading

Calibrate to existing then consider retrofit

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Freeze-Thaw risk assessment

Freeze-Thaw Cycle

Material temperature cycles below -5°C (23°F) and

back up above freezing

Damaging Freeze-Thaw Cycle

Freeze-thaw cycle occurs while material moisture content

is above the critical degree of saturation

Dunning Place - Base Case, North Facing, High Rain Exposure

Temperature and Moisture Content of Grey Face Brick

-60

-40

-20

0

20

40

60

80

100

120

21-Jun 10-Aug 29-Sep 18-Nov 7-Jan 26-Feb 17-Apr 6-Jun

Time

Tem

pera

ture

(°C

)

-60

-40

-20

0

20

40

60

80

100

120

Mo

istu

re C

on

ten

t (k

g/m

3)

Temperature Moisture Content

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Freeze-Thaw risk assessment

Existing wall w/ high rain exposure Retrofit wall w/ high rain exposure

Consider degree of saturation (moisture content) during hours

when temperature is below -5°C (23°F)

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Material Sampling


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Sampling Challenges

coordinate sampling

locations

New mechanical openings

New wheelchair access

New elevators / stairs

Areas on “blind sides”

From attic stock

Units that can be replaced

by attic stock

Don’t only sample damaged

units that will be replaced

Does the sampling consider

enough areas to be truly

representative ?

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Sampling Challenges

Course removal of a large area

of wall is easy for a contractor

but destructive and, in most

cases not acceptable to owners

Careful removal of individual

units is possible and preferred

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Field Sampling of Masonry Units

Bulk Sampling

Retrieve a large number of

samples (10-100/type)

More samples improves

population representation

Pre-screen whole units back

at the lab (A-value tests)

liquid transport coeffs

surrogate for other moisture

transport and storage

properties

Time consuming and

expensive

Non-Destructive Field Testing

Pre-screen units in-situ on

the wall assembly

Reduces number of samples

collected (4-12/type)

Pre-screen by assessing rate

of drying or “drying slope”

as an in-situ surrogate

Requires experience to

interpret results

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Bulk Sampling Example

1 bldg., 47 bricks

(ID: location-number)

7 types

(by type of clay,

frogs, stamps, etc.)

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Non-Destructive Field Testing Procedure

Identify candidate locations

and bricks

Measure starting MC

Spray 15 ml of water

Measure “redistribution” MC

at 2 minutes

Measure “drying” MC

at 8 minutes

Calculate drying slope and

group candidate bricks

Identify final sample units

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Non-Destructive Field Testing Example

ሶ𝑀 =𝑀2𝑚𝑖𝑛 −𝑀10𝑚𝑖𝑛

8𝑚𝑖𝑛

1 owner, 2 bldgs., 2 types of brick, limited sampling

Initial moisture meter reading and drying slope measurements

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Non-Destructive Field Testing

Comparison of water uptake and

drying slope for selected bricks

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Measurement Repeatability

and Reproducibility


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Measurement Challenges

Length measurement figures

highly in the determination of

the critical saturation

Multiple measurements on a

given sample are averaged to

reduce uncertainty

Concerns:

Repeatability of measurement

on a single sample

Reproducibility from one lab

tech / engineer to another

(Length & Critical Saturation)

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Sample Slice Length Measurements Repeatability

Repeated length measurements of six limestone slices

1 initial measurement then 8 more following immediately

3 operators taking care to use the same procedure

(placement, number of clicks on the micrometer ratchet, etc.)

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Sample Slice Length Measurements Repeatability

Accounting for rate of wear:

adjusted equivalent strain relative

to first Operator A measurement

∆𝑒𝑞′ =

𝑙n −𝑚(𝑛 − 1) − 𝑙1𝑙1

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Length Measurement Procedure

For Initial Length (before F/T):

Make repeat measurements

until consistent within

+/- 0.00005 in.

Intent is to displace loose

material at the surface

For Final Length (after F/T):

Make a single measurement

being careful seat the

micrometer slowly

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Within-Lab Critical Saturation Measurement Reproducibility

Histogram of slice dilation after 12 cycles (total of 48 slices)

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Histogram of slice dilation after 24 cycles

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Mean and 95th

percentile strain after 12 and 24 freeze-thaw cycles

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Repeatability and reproducibility tests show

Measurement method allows good repeatability from one length

measurement to the next

Measurement and analysis methdos excellent reproducibility of

length measurement and Critical Saturation from one operator to

the next

Table 1. Critical Freeze-thaw Saturation Measurements

12 Freeze-thaw Cycles 24 Free Thaw Cycles

Operator # of

Saturation Samples

Mean 95th

Percentile # of

Saturation Samples

Mean 95th

Percentile

All Data 16 77.4% 76.3% 14 77.4% 77.2% A 4 76.5% 74.8% 2 77.0% 76.3% B 12 77.4% 76.5% 12 77.6% 77.3%

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In the Critical Saturation Approach

to assessing Freeze-Thaw Risk

Growing Confidence

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Armoury to Recreation Center Conversion, VT

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-25

-20

-15

-10

-5

0

5

10

15

20

25

01-N

ov

08-N

ov

15-N

ov

22-N

ov

29-N

ov

06-D

ec

13-D

ec

20-D

ec

27-D

ec

03-J

an

10-J

an

17-J

an

24-J

an

31-J

an

07-F

eb

14-F

eb

21-F

eb

28-F

eb

07-M

ar

14-M

ar

21-M

ar

28-M

ar

Bri

ck T

em

pera

ture

(oC

)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Wate

r S

atu

rati

on

Brick TemperatureHighly Absorptive Brick

Less Absorptive Brick

Rain Exposure

High

Medium

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Chemistry Lab to Business School Conversion, NJ

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Chemistry Lab to Business School Conversion, NJ

Predicted moisture distribution during freezing

temperatures, Existing Wall Assembly, Argillite

Stone, High Rain Exposure, Southwest-facing

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Historic Armoury Building, NS, Canada

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1

10

100

1,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ho

urs

Degree of Saturation

Exterior 10mm

1

10

100

1,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ho

urs


20mm Depth

1

10

100

1,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ho

urs


35mm Depth

1

10

100

1,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ho

urs


60mm Depth

1

10

100

1,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ho

urs


100mm Depth

Predicted moisture distribution during freezing

temperatures, Existing Wall Assembly, Sandstone,

High Rain Exposure, North-facing

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Acknowledgements

Kohta Ueno of BSC

Collaboration on

numerous projects

Site documentation

Sample collection

Logistics

Pier review

Etc…

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FOR FURTHER INFORMATION PLEASE VISIT

www.rdh.com

www.buildingsciencelabs.com

OR CONTACT US AT

[email protected]

[email protected]

[email protected]

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References

Fagerlund, G. 1977. The critical degree of saturation method of assessing the freeze/thaw resistance of

concrete. Journal of Structures and Materials 10(58):217–229.

Mensinga, P., J. Straube, and C. Schumacher. 2010. Assessing the freeze-thaw resistance of clay brick

for interior insulation retrofit projects. Proceedings of Performance of the Exterior Envelopes of Whole

Buildings XI, Atlanta, GA.

RILEM. 1980. Recommended tests to measure the deterioration of stone and to assess the effectiveness

of treatment methods/ Tentative Recommendations, RILEM Commission 25-PEM. Materiaux et

Constructions 13(75), 175-253.

Straube, J., and C. Schumacher. 2006. Assessing the durability impact of energy efficient enclosure

upgrades using hygrothermal modeling. Research report 0605. Somerville, MA: Building Science

Corporation.

Ueno, K., P. Kerrigan, H. Wytrykowska, and R. Van Straaten. 2013a. Retrofit of a mulitfamily mass

masonry building in New England.” Washington, DC: Building America Building Technologies Program,

Office of Energy Efficiency and Renewable Energy U.S. Department of Energy.

Ueno, K., R. Van Straaten, and C. Schumacher. 2013b. Interior insulation of mass masonry walls: Joist

monitoring, material test optimization, salt effects. Washington, DC: Building America Building

Technologies Program, Office of Energy Efficiency and Renewable Energy U.S. Department of Energy.

Van Straaten, R. 2014. Improving access to the frost dilatometry methodology for assessing brick

masonry freeze thaw degradation risk. Proceedings, Canadian Conference on Building Science and

Technology, Toronto, ON.

Wilson, M., M. Carter, W. Hoff. 1999. British Standard and RILEM water absorption tests: A critical

evaluation. Materials and Structures 32:571-578.

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Another example

Existing wall before insulation Retrofit wall with insulation

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Critical Freeze-Thaw Saturation Measurement of In-Service Masonry · 2016-12-15 · Field Sampling...

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