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Brick effloresence & mortar loss & spalling © D Friedman at InspectApedia.com Concrete, Block & Brick Structural Test Methods

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Concrete, Brick & Other masonry non-destructive test methods & equipment:

This article describes and provides research on a wide range of non-destructive inspection & test methods, tools, procedures & standards used to examine concrete structures as well as masonry block, brick and other structures for hidden damage such as cracks, voids, omission of steel reinforcement, re-bar corrosion, and similar concerns.

This article series explains how to recognize, diagnose, & repair concrete & other masonry materials used for foundations, walls, floors, roofs, and other structures. These methods can evaluate the masonry or solid concrete for signs of failures such as cracks, spalling, movement, bulging, leaks, damage due to impact, settlement, frost or water damage, corroded re-bar, corroded steel beams, vibration, and other problems.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Non-Destructive Inspection & Test Methods for Concrete, Block & Other Structures

Structural brick wall with rain screen opening between wythes © D Friedman at InspectApedia.com

Methods of Detection of Hidden Cracks or Other Structural Damage in Concrete & Masonry Walls & Foundations are described here.

Question: Is it possible to detect cracks in brick walls or concrete walls and slabs that are hidden from view by plaster?

2017/05/29 Parth Bathia said:

Is it possible to detect cracks in brick walls or concrete walls and slabs that are hidden from view by plaster?

Like there is no through and through air pockets.

If there is a way. I want to know how is it possible to detect the same.

I get the use of thermal imaging but that is only possible for detecting temperatures on surface.

I want something that might be able to detect cracks that is hidden about 6 - 8 inches inside the walls without breaking or damaging the wall.

This question was posted originally at BRICK FOUNDATIONS & WALLS

Reply:

What an interesting question; thank you. I have some obvious and some speculative answers:

1. Obvious cracks will often show up through plaster if there is ongoing movement in the masonry wall that has been plastered-over, either as plaster cracks or sometimes as a plaster bulge.

2. With thermal imaging there is a small chance you'd see a wall crack IF the crack were leaking water AND you happen to scan the wall when the leak is enough in quantity and lower temperature to show up as a temperature variation - but I'd consider such "detection" speculative.

3. There are non-destructive testing methods (such as the Echo Impact method) that can find cracks or voids in masonry structures, though in my opinion those are going to work best on placed (poured) concrete that would not be expected to have many voids.

A structural brick wall will usually have an interior wall cavity and may have many other smaller voids that can be confusing when using an echo-impact masonry void detector.

Types of Non-Destructive Methods for Concrete Damage Detection

Parking level collapse at Northridge Meados, Los Angeles Earthquake (C) Daniel Friedman at InspectApedia.comThe tools and methods listed below are used by experts to screen or scan concrete structures for various defects such as delamination, voids, or large cracks. I'm doubtful that many of these work very well on a brick wall for reasons I cited above.

Photo: Partial collapse of the rear or West parking lot at Northridge Meadows after the Los Angeles earthquake. Even as a layman inspecting this collapse it appeared to me that even by casual inspection - after the catastrophe - one could see that the steel reinforcement had been interrupted when and just where the collapsed section of raised parking lot had broken and collapsed during this earthquake.

More about the Northridge Earthquake is at EARTHQUAKE DAMAGE PHOTOS CA 1994

Article Contents

Drossbach & Similar Grouted Joint & Rebar Assessment

Definition: Drossbach ducting is a metal tube manufactured from galvanised steel to create a spiral round duct that may be used along with rebar and grout to connect pre-cast concrete building components such as wall panels and floors.

Definition: A Drossbach-type joint combines the ducting with re-bar and grout to join these building components. Drossbach ducting, rebar and grout jproduces post-tensioned tendons used to secure the joint between the precast wall and floor or for similar connections.

The Drossbach joint may use 0.3mm galvanised steel strips with an internal diameter from 33 to 107mm- Adapted & expanded from Contech cited below.

[Illustrations needed, CONTACT us if you can provide images.]

In New Zealand experts are finding increasing examples where grouted rebar connections typically between concrete floor and precast wall panels have not been addressed, compromising seismic performance and leading to horizontal cracking between floor and walls on external faces - see first link, below, courtesy of Paul Probett, Incodo, New Zealand, for suggesting this topic.

Overstrength factors for reinforced concrete structures are defined in the New. Zealand Concrete Structures Standard, NZS 3101:2006

Mr. Probett, director of Incodo, Forensic Building Pathology, can be contacted at Incodo Ltd., Post Box 8202, Cherrywood, Tauranga, 3110, Courier 4/511 Cameron Rd, Tauranga, New Zealand, tel: +64 7 578 7499 M +64 27 28 000 36, Email: mail2us@incodo.co.nz Website: www.incodo.co.nz Skype: paulprobett

Research on detection of missing rebar, Drossbach grouted joint assessment, voids in concrete, & re-bar assessment

CONTACT us if you have suggestions for this topic.

Concrete and re-bar joint assessment tools include GPR (Ground Penetrating Radar), electrical resistance and other electrical tests, and other methods discussed by the authors cited below.

Thermography for Detecting Damaged Masonry Structures

Thermal image example, Paul Probett, Incodo 2008

Image courtesy Paul Probett, Incodo, cited at the Thermal Imaging Thermography article linked-to below.

Infrared Scanners (IR) or Thermography (IT) can detect temperature variations across a masonry surface.

Watch out: Using either an IR thermometer that measures temperature variation, or currently more popular, diagnostic, and more expensive, thermal imaging can show up the presence of moisture IF the moisture or leak is current.

IR or IT will not reliably show up leaks whose moisture has dried since the leak occurred, though some other moisture meters that rely on resistance measurement might detect mineral salt variations left behind by prior leaks (efflorescence).

See THERMAL IMAGING, THERMOGRAPHY

Also see BRICK WALL FROST & WATER CRACKS, EFFLORESCENCE, SPALLING

Delmhorst pin type moisture meter with long probes © Daniel Friedman at InspectApedia.com

Moisture Meters for Masonry Structure Damage Detection

Moisture meters, both pin-type and electronic, can detect variations in the moisture level across all types of masonry surfaces.

The depth of sensing of pin type moisture meters (shown above) is limited to the depth of penetrations of pins of the sensor into the material, while an electronic moisture meter (shown below) can penetrate inches into the material, depending on its density and electrical properties.

Tramex moisture encounter in field use © Daniel Friedman at InspectApedia.com

As with our IR and IT scanning comments in this article, a moisture meter won't reliably detect prior leaks that happen to be dry at the time of inspection and testing.

See MOISTURE METER STUDY for a description of the effectiveness of different types of moisture meters used in buildings.

Ultrasound or Ultrasonic Detectors for Detecting Masonry or Concrete Structure Defects

Ultrasonic testing devices use a probe and sensor that can measure the thickness of steel reinforcement or steel beams that are nearly-buried in a masonry structure, as long as one side of the steel member can be accessed. This approach might permit detection of rust damage or loss of steel material in the hidden interior of the structural wall, roof, or slab.

Vibration Monitors for Concrere Structure Assessment

Vibration monitoring can assess the amount of building movement caused by traffic, an earthquake, or nearby construction work or blasting. Vibration monitoring is particularly apt to monitor nearby buildings for the impact of an ongoing construction project.

Photograph: using a borescope to examine a building wall cavity

Borescopes for Investigating Structural Damage to Buildings

A borescope won't be much help in an external screen of a masonry structure for hidden damage but it might allow a view of exposed surfaces that are blocked by obstructions such as a radiator or HVAC equipment.

A simple inspection mirror and a good light may also suffice. Borescopes can give a limited view of the inspection of a wall cavity. So you might inspect the cavity side of a brick veneer wall by probing the wall cavity from the building interior.

See HIDDEN MOLD in CEILINGS / WALLS for examples of better use of a borescope.

Pachometer Tests on Masonry Structures

A pachometer is a non-destructive magnetic sensor that can find buried steel in masonry structures. A pachometer can be used thus to find re-bar, reinforcing steel mesh, and hidden steel beams.

Keep in mind that pipes, expanded metal lath, metal conduit will also be detected by this tool. Technical use of a pachometer in evaluating a concrete structure would be the confirmation of re-bar spacing and sizes as well as depth of the re-bar in a concrete ceiling, roof, wall, foundation, or slab. We might aso use a pachometer to check the depth of metal radiant heat piping in an older radiant heat floor.

Flat-Jack Tester & Flat Jack Testing Methods for Masonry Wall Damage Assessment

Flatjack testing can detect deformed or stressed unreinforced masonry walls (concrete block, brick) and may detect deformation in concrete walls & foundations. Flatjack testing is also described (Carpinteri 2004) as acoustic emission (AE) technique, a non-destructive instrumental investigation method ... to measure and check the evolution of damage in concrete and masonry structures.

Ground Penetrating Radar for Building Reinforcement Assessment

Crack monitor (C) Carson Dunlop Associates

Ground penetrating radar (GPR) is widely used in broad-scope sitework to locate buried metal items such as a buried oil tank.

GPR uses an electromagnetic pulse that is reflected back to the instrument at varying signal levels based on what the pulse encounters in the pulsed area. Synonyms for ground penetrating radar or GPR include EMR (Electromagnetic Reflection), SIR (Subsurface Interface Radar), georadar, subsurface penetrating radar, and soil radar. (Blindow 2007).

GPR is also used in a more-technical application to find buried steel beams or reinforcement in a concrete structure. GPR can report on the location and thickness of steel or other metallic components hidden from view in solid structures, including re-bar, steel mesh, beams, as well as conduit and metal water pipes, even metallic ducctwork.

Avongard crack monitor (C) Avongard Co.

Strain Gauge Testing Equipment for Monitoring Movement or Deformation in Masonry Structures

Strain gauge monitoring equipment or devices are affixed in place across concrete, masonry block, brick or other surfaces where cracks are to be monitored for movement, deformation, or change.

Once the Crack Monitor is in position across a crack, the cross hairs shift vertically or horizontally on the grid if movement occurs,so that anyone can easily see and track crack movement." (Photo at left of a crack monitor in place is courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].)

See CRACK MONITORING METHODS - Methods for Monitoring Foundations for Evidence of Ongoing or Episodic Movement.

Impact Echo Testing for Concrete Structure Defects

Impact-echo testing, one of the most widely-used concrete testing method for concrete and masonry, combines an impact device and sensor with (typically) a computer and special software to analyze sound waves or vibrations in solid concrete structural walls, floors, ceilings.

Impact echo testing can locate areas of damage to the concrete structure that are not readily visible, such as cracks in a concrete wall that are covered by plaster. Echo tests can report on the location, size, pattern, and thus severity of cracks in the structure.

Rebound Hammer Method for Testing Solid Masonry: concrete

A rebound hammer is used to evaluate the quality and uniformity of "cured" or hardened concrete walls, floors, foundations. ASTM C805 describes the use of this test to assess the uniformity of concrete "in place" and to find "regions of poor quality or deteriorated concrete".

The accuracy of this test method is affected by a number of site factors including the smoothness of the concrete surface, the age and moisture content of the concrete, extent of surface carbonation, the use of aggregate and its properties, the presence of air voids, the nearby presence of reinforcing steel, the concrete temperature, and the care with which the rebound hammer was calibrated.

CEMTEX offers this clear description of the rebound hammer:

The [rebound hammer] consists of a plunger rod and an internal spring loaded steel hammer and a latching mechanism.

When the extended plunger rod is pushed against a hard surface, the spring connecting the hammer is stretched and when pushed to an internal limit, the latch is released causing the energy stored in the stretched spring to propel the hammer against the plunger tip. The hammer strikes the shoulder of the plunger rod and rebounds a certain distance.

There is a slide indicator on the outside of the unit that records the distance traveled during the rebound. This indication is known as the rebound number. By pressing the button on the side of the unit, the plunger is then locked in the retracted position and the rebound number (R-number) can be read from the graduated scale.

A higher R-number indicates a greater hardness of the concrete surface. - CEMEX Technical Bulletin No. 2 (2013)

Half-Cell Tests for Metal Corrosion in Masonry Structure Reinforcements

Half-cell testing is an electronic test method that guesses at the level of active corrosion of steel reinforcement (re-bar or steel mesh) in reinforced concrete structures. In most-general terms, a half-cell test for metal corrosion is based on the reaction of anodes and cathodes.

A voltmeter has its positive lead connected to an exposed end of steel reinforcement in a concrete structure such as an end of a rebar. The negative lead of the voltmeter is connected to a reference electrode that is placed on to the surface of the concrete. (Gu 1998)

Factors influencing the accuracy of half-cell tests on concrete to screen for corrosion of its rebar include the oxygen concentration at the interface of the re-bar and the concrete, the amount of concrete carbonation (reaction between atmospheric CO2 and CaOH in the concrete that reduces the pH of the steel-concrete interface, chloride ion concentration, the use of corrosion inhibitors at the time of construction, the use of expoxy-coated or galvanized re-bar, the density of the concrete cover, the use ofhigh-resistance concrete, the presence of organic coatings or sealants on the concrete surface, the presence of a concrete patch or other repair, and the presence of cathodic protection systems attached to the re-bar along with the problem of stray electrical currents.

Although it was blamed on excessive piling up of snow, the 2007 collapse of a section of the Poughkeepsie Galleria's parking garage might have been predicted had a prior survey been made using Half-Cell testing and a Pachometer to assess the presence of steel reinforcement as well as its condition.

 


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2017-05-17 by (mod) re: drying out a brick foundation walled crawl space

Linda

I agree that one needs to find the source of water or moisture in order to be able to correct it, followed by drying out the crawl area.

Please take a look at this diagnostic/repair article series beginning at CRAWL SPACE DRYOUT https://inspectapedia.com/structure/Crawl_Space_Dryout.php

and let me know what specific questions remain.

On 2017-05-17 by Linda

We lifted our house due to flooding from sandy. Part of our house has brickexterior ( veneer I guess) we now have access to our crawl space and I can see the foundation is wet. I am trying to figure out why? So I can then figure out how to fix it

On 2017-03-13 by (mod) re: signs of footing movement

Most likely the footing has shifted, or if the brick is a veneer wall its support or the attachment of that support to the foundation (some veneers used an L-bracket) may have failed. We'd need to see details or photos - for which you can use the page top or bottom CONTACT link if you like.

Watch out: loose brick walls, if the bond courses or for a veneer the connections to the structure are broken there is danger of a collapse that could cause injuries or worse.

On 2017-03-13 by Nick

What is the possible cause of a brick wall that has shifted on the foundation footing on one end. There is about 1/2" of overhang of the bricks on the footing on about 1/4 of the wall. There has been movement and repairs to the foundation.

On 2017-02-22 by (mod) re: diagnosing a severe foundation wall failure

Fran

I can't reliably diagnose your foundation wall failure from just your e-text; one needs to look both outside and inside for conditions that affect the foundation.

A foundation damage diagnosis of "failure over time" is 100 % baloney despite your inspector's credentials. It is in essence nearly content-free.

A building foundation is not a consumable that gets "used-up" over time until it fails.

Rather what your engineer may have meant to say (perhaps he skipped Freshman English) was that the cracked or buckled foundation damage did not occur in a single event but rather that it happened over time.

To support that conclusion, and to avoid an endless battle of "opinions" in our current world where objective data and facts are either insufficiently valued or are deliberately de-valued in order to serve someone's purpose, a decent engineer ought to have said what he observed, found, measured, that supported that conclusion.

For example if I find old paint, dust, dirt, inside a horizontal crack in a bulged block foundation wall I am confident that the bulge and crack didn't happen yesterday, even if yesterday's forces might have exacerbated it.

So sad.

The engineer's report is unreliable and insufficient because it

- by your account gives no information to support the conclusion
- fails to explain the cause of the damage
- fails to describe the extent of damage
- doesn't tell us if repairs are needed
- doesn't tell us what actions are needed to prevent further or future foundation damage

IF you have photographs of the foundation wall before the flooding and freezing event that your email suggests occurred then you could prove rather convincingly that the even coincided with the burst hose and - this is correct, right? - that the soaking of the ground was followed by freezing weather that might have added frost-push to wet-soil loading against the wall.

On 2017-02-22 by (mod)

Anonymous: reposting translated to English

Sir my wall I get damp and mildew-like color white, and then it exits tell Solution

Reply:

It sounds as if you are describing mineral salts or effloresence - search InspectApedia for EFFLORESCENCE to read the details of what this is and how to prevent it.

aisa lagata hai ki aap khanij lavan ya aiffloraisainchai varnan kar rahe hain - yah kya hai aur kaise ise rokane ke lie ke vivaran ko padhane ke lie aiffloraisainchai ke lie khoj inspaichtapaidi।

On 2017-02-22 y Fran

Hi, on my old house cement block basement failure. Back yard has a slight grade toward the house,but, has grade away from house 6 to 7 inchess out about 8 ft a garden hose was left on & it burst under the porch for several hrs in cold weather, Wall has about 4ft.

Of dirt cover & basement height is low , about 5ft 5in., my INS. Co. Sent an engineer & he said failure over time. I feel it was the hose water that saturated the soil & froze. Bowed in with large cracks & No indication of water now .even after a heavy rain. Thank you for your opinion

On 2017-02-03 by Anonymous

sir meri ghar ki dewar main seelan aati hai aur colour fafundi ki tarah white hokar bahar nikalta hai to iska solution bataiye

On 2016-05-30 by (mod) re: broiken lintels in a London home

Zwai:

As a lintel usually carries weight, I wouldn't assume that a break is harmless unless you mean to say that the lintel was too long for the space into which it was being inserted and one-end broke off; that is, any crack or break in the open span of the lintel is surely going to mean trouble, as might insufficient bearing area under the lintel ends in the wall. You can send photos using the page top or bottom CONTACT link.

On 2016-05-30 by Zwai, East London

The lintel in my garage is too long about 6m long. It broke while the builder was placing it. I'm wondering if it will not cause problems in a long run. Please advise

On 2016-05-02 by Doug Pera

I have a leaning exterior brick wall that is approximately 5' tall and 20 'long. It is leaning and also needs some tuck pointing . Is there anyway of bracing the way other than tearing it down and starting over? The earth on one side of wall is higher than the other. Also, I am not sure of any footings.
Thank you
doug

On 2015-12-02 by (mod) re: footing width for a brick wall

Vic

For a brick wall that is supported by a foundation, the width of that footing is determined by the original design engineer, architect or contractor based on soil properties as well as anticipated weight or loading from above.

If the footing width were so wide that you could in principle move the brick wall that rests on it 50cm without finding the brick wall now off of the foundation completely, you could do so, but the risk is that the wall begins to tip or lean, ultimately collapsing.

On 2015-12-02 by victory crown

My question is can I move a brick wall fence, with foundation of reinforced concrete strip foundation, to the right or left up to 50cm?

On 2015-06-18 by Anonymous

Many bricks are chipped mold has repeatedly been corrected, only on inside wall. Soon the new paint on that inside wall is peeling. This is a COOP. It is now two & halp years.

I cannot get a full nights sleep waking up with itchy eyes.

Question: Aussie readers & brick construction

Great article! Although this information isn't specific to Australia, it has still helped me understand more in my building contractor course. Thomas Wong, 11/29/2011

Reply:

Thomas thanks for the nice comment about our website content. We know that we have many readers in Australia and New Zealand and I'm anxious to add terms and technical details that match those used in your area.

While climate and constuction practices vary around the world, brick and masonry construction in general suffers similar problems in most places - often it's the local names for materials & construction methods that vary more than the materials and pracices themselves. One man's septic drainfield is another's soakaway bed.

We'd welcome specific questions, comments on different construction terminology used in different parts of the world, etc. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. Working together and exchanging information makes us better informed than any individual can be working alone.


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