Inside This Special PART ONE CONT’D

PART TWO: THE IMPOR-TANCE OF CONCRETE CURING

PART TWO CONT’D PART THREE: MOTHER NATURE HAS CONTROL.

PART THREE CONT’D COLD WEATHER QUIZ

Thanks to this past brutal winter, many of you are noticing scaling or mortar flaking in new exterior concrete flatwork such as sidewalks, driveways, parking lots, and curbs and gutters. This superficial deterioration can be the result of many factors, includ-ing inadequate concrete curing.

Proper concrete curing involves providing and/or maintaining adequate moisture and temper-ature to permit the portland cement in the con-crete mix to properly hydrate and gain strength with time. The freeze-thaw durability of con-crete is dependent upon three factors: 1) the in-corporation of fine air voids (air entrainment) in the concrete, 2) proper finishing, and 3) cur-ing for the development of durability strength. These factors result in beneficial properties that maximize water-tightness, freeze-thaw durability and volume stability.

It’s important, however, to note: Curing is the final step in the nearly 70-step, highly complex process of concrete production and placement. As in any process, missing or poorly perform-ing any step can negatively impact the out-come (i.e., finished concrete) in terms of appearance and sustainability.

Proper curing is not only necessary; it’s criti-cal. Still, proper curing practices are often overlooked due to a number of factors such as scheduling, environmental constraints and aes-thetics. Granted, these factors present some very hard choices on the part of the construc-tion team/owner.

Environmental conditionsThe Upper Midwest’s typical early-winter weather and its potential for numerous freeze-thaw cycles can wreak havoc on early-age concrete, especially that which isn’t properly finished and cured. Design concrete strength, which at 4500 psi is the minimum strength specified to resist repetitive freeze-thaw cycles, can be attained under proper ambient conditions at 28 days; the longer the curing

process, the greater likelihood of reaching the design strength. However, the practicalities of modern construction scheduling do not permit a 28-day curing interval. Not incorporating plans for providing the best finishing and cur-ing at the time of your work may prove costly if winter weather comes early.

Early-age concrete that reaches its design strength may still be relatively porous. As a result, design strength doesn’t necessarily equal durability strength. Concrete requires additional time for the complete hydration of the cement to fill pore spaces and capillaries, which, if unfilled, can represent avenues for significant moisture intrusion leading to saturation. The critical saturation of this paste can overwhelm even properly air entrained early-age concrete. In addition, research and experience suggest that concrete given time before winter to sig-nificantly dry after proper curing will perform better in real-life durability testing.

Aesthetic requirementsConcrete can be cured through the use of water and various chemicals called curing com-pounds/sealers (we’ll discuss the properties of each in part two of this article). Certain curing practices can affect the appearance and wear resistance of the finished concrete. For exam-ple, the use of polyethylene, burlap, or a com-bined product called “burlene” can result in color variations, termed “tiger striping,” to the finished concrete when differential drying has occurred. Likewise, some departments of transportation may specify the use of a curing compound for their roads and bridges, which is very effective for curing, but its potential for non-uniform color and wear is not aestheti-cally acceptable for most other commercial and residential applications.

TimingCuring should take place immediately after concrete is placed and finished; not hours later, and certainly not on the following day. It is critical for early-age concrete to be sub-jected to moisture and temperatures above 50 degrees Fahrenheit for appropriate strength gain. Low humidity and even a slight wind can quickly compromise surface paste and result in a network of fine, random surface cracks, known as “crazing cracks,” which generally occur within 24 hours after place-ment. Furthermore, if the concrete dries out or temperatures dip to near freezing, its strength and durability can be compromised. Construction schedules should allow for cur-ing to take place right away, and with the proper materials.

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Consider the Cure Part One | continued on page 2

PART ONE: FACTORS AFFECTING PROPER CONCRETE CURING PRACTICESORIGINALLY PUBLISHED IN THE SUMMER 2014 AMERICAN EDGE

BY TERRY SWOR, PG, AND GERARD MOULZOLF, PG – AET SAINT PAUL

SPECIAL SERIES: CONSIDER THE CURE A NEWSLETTER FOR CLIENTS AND BUSINESS PARTNERS OF AMERICAN ENGINEERING TESTING, INC.

800.972.6364 • WWW.AMENGTEST.COM

A common complaint. This surmountable curb was cured in fall 2013 and suffered from the harsh winter; scaling and pop-outs are apparent.

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Qualified professionalsThe curing of concrete is an art as well as a science. It requires a skilled professional to coordinate activities with the producer and to perform the proper placement, finishing and cur-ing techniques. Make sure the professionals you choose for your job are qualified as such by the

American Concrete Institute’s Certified Concrete Finisher program or similar accreditation.

Part two of this series focuses on construction considerations for curing exterior concrete late in the construction season.

For further reading:Aggregate & Ready Mix Association of

Minnesota’s Curing Guidelines brochure – www.armofmn.com/resources

“Curing Concrete,” by Peter C. Taylor, 2014 CRC Press.Dr. Kim Basham’s presentation on “Avoiding Surface Defects on Exterior Slabs” (presented to the Minnesota Concrete Council on May 15, 2014) – www.minnesotaconcretecouncil.com

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CONSIDER THE CURE

Part One | continued from page 1

Carbonation (unstained paste) proceeds up to 3 mm deep in a freshly sawcut and lapped cross section of concrete exposed to pH indicator. Note sub-horizontal microcracking (incipient scaling) within the carbonated paste. Carbonated paste (low pH) is a sign of compromised surface paste and is not freeze-thaw resistant.

In part one of this article (Summer Issue 2014), we discussed the critical role proper concrete curing practices play in the longevity and performance of exterior concrete. Now, as the Upper Midwest looks ahead once again to cooler temperatures, we’re focusing part two of our series on the importance of concrete curing—the challenges associated with new variables presented by the advent of winter, proper placement and finishing procedures, and considerations for late-fall curing. Ironically, many industry practitioners think curing is only necessary for the attainment of design strength; however, it’s critical to both the short- and long-term performance of exterior concrete.

What is concrete curing?According to Dr. Peter C. Taylor, associate director of the National Center for Concrete Pavement Technology and author of “Curing Concrete,” curing is generally defined as “actions taken to maintain moisture and tem-perature conditions in a freshly placed cementitious mixture to allow hydraulic cement hydration and pozzolanic reactions to occur so that the potential properties of the mixture may develop.” Most of the criti-cal performance properties for early-age exterior concrete are actually related to the paste development within the upper 30 mm

(1.2 inches) of the concrete member.

The real costs of proper curing can be rela-tively low when compared to the perfor-mance benefits it provides, namely the pres-ervation of the mix’s design durability and longevity. Simply stated, you can pay now for proper curing, or you can pay in the near future for concrete replacement.

The importance of water and temperatureWater plays an essential role in the production and placement of cast-in-place concrete. Water is needed to hydrate the cement (water

of necessity) and to assist in the placement process (water of convenience). At AET, we also understand the “Rule of 20” with respect to the speed of chemical reactions associated with the hydration of cement. For every 20°F increase in temperature, these reactions will occur twice as fast; for every 20°F drop in temperature, they occur half as fast. If a con-crete placement occurs in colder temperatures and is not protected and/or heated, the delayed progress of hydration will significantly impact the timing of finishing, curing methods, heat-loss protection and length of time the curing should be conducted.

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Part Two | continued on page 3

PART TWO: THE IMPORTANCE OF CONCRETE CURINGORIGINALLY PUBLISHED IN THE FALL 2014 AMERICAN EDGE

BY TERRY SWOR, PG, AND GERARD MOULZOLF, PG – AET SAINT PAUL

Cold-weather construction issuesCold weather puts immature concrete at risk:

1. It increases the rate of evaporation of water from the concrete’s surface, leading to plastic shrinkage cracking

2. In rapidly decreasing temperatures, the pore water can freeze, causing internal damage

3. Colder temperatures greatly slow the rate of hydration of the cement (hydration essentially stops at 29°F)

4. Thermal shock related to rapid evaporation and temperature change once temperature protection is removed

A sample of well-cured concrete with minimal carbonation (left) and poorly cured concrete with ample carbonation (unstained paste). Carbonated paste (low pH) is a sign of compromised surface paste and is not freeze-thaw resistant.

6 mm

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CONSIDER THE CURE

800.972.6364 • WWW.AMENGTEST.COM

normal time delay needs to occur between placement and finishing phases to allow the water of convenience to rise to the top of the concrete and evaporate away (termed bleed water). Colder temperatures delay this pro-cess significantly; an unsuspecting finisher could either seal off or work the bleed water back into the concrete surface, negatively impacting its strength and durability.

Cast-in-place concrete has pores, and although bleeding occurs, the pores typically retain water, which is available for continued hydra-tion. Nevertheless, if temperatures prevent complete hydration from occurring, the satu-rated pores may cause freezing deterioration of the concrete’s upper surface.

Common curing challengesHorizontal surfaces, especially exterior slabs, often present the most challenge given the large surface-to volume-ratio and the usual demand for these features to be serviceable as quickly as possible. Furthermore, these mem-bers are often placed at the tail end of a proj-ect, which generally occurs in the fall when weather conditions—low relative humidity, cooler temperatures and blustery winds—are less than ideal. (See sidebar for additional notes on cold-weather construction issues.)

Curing methodsThere are two methods for curing exterior concrete: one includes the use of water; the other includes the use of a chemical com-pound.

Generally speaking, water cur-ing for seven days is the most effective curing method, espe-cially if the project schedule and weather permit. The ben-efits of a water cure include the maximization of the hydra-tion reaction; the availability of water is essential to the hydration process—and a properly performed hydration process is key to reducing the potential for plastic shrinkage cracking. (In part one, we addressed the use of materials such as polyethylene, burlap and” burlene” covers to maintain the avail-ability of water at the concrete’s surface.)

If the shape of the member (e.g., as in a vertical structure), weather conditions, time of the year, aesthetics, and final use of the

placement do not allow for water curing, so a chemical compound may be used.

Chemical curing compounds fall into one of two categories of liquid membrane-forming chemicals under ASTM Specifications C 309 or C 1315. The distinction between the mate-rials complying with C 309 is that these chemicals primarily provide curing properties during the early hardening stages of concrete, whereas materials consistent with C1315 also incorporate longer-term sealing characteris-tics, as well as alkali resistance, resistance to degradation from ultraviolet light, and non-interference with adhesion properties.

Curing benefit studiesThe American Concrete Institute’s (ACI) “308R-01: Guide to Curing Concrete (Reapproved 2008)” extols the benefits of properly water curing exterior concrete. Below is a figure from Murdock, Brock and Dewar (1991) that shows the relationship between days of water curing and freeze-thaw resistance of early-age concrete. In part one of this article, we noted that exterior concrete, as specified by ACI, should have a maximum w/c ratio (water to cementitious content) of 0.45. Using that curve, testing for freeze-thaw resistance dramatically illustrates the value of improved performance of the concrete after just seven days of water curing.

The reason for improved durability is illus-trated in other studies that show reductions of 50% in surface (the upper 10 mm or 0.4 inches) absorption of concrete by simply extending the water cure from one to four

days. Testing for abrasion and deicing chemi-cal resistance shows the same benefits for improved surface performance are possible by adopting a longer-term water cure.

The availability of the water within the proper temperature range drives the hydration pro-cess to fill in the capillaries and pores in the upper portion of the placement.

Late-fall considerationsACI and other experts indicate that newly placed concrete requires 21 days to air-dry after water curing. If the advent of colder weather doesn’t allow for this critical step, decisions must be made regarding the use of a chemical compound. Dr. Kim Basham of KB Engineering suggests there are two options:

1. Use a penetrating water-repellent prod-uct such as silane and siloxane. These materials are breathable, plus their hydrophobic properties restrict the ingress of water molecules and deicers, providing added protection for the advent of winter weather.

2. In accordance with ACI 308R-15, select a combination curing and sealer product meeting the C1315 specification, which ACI recognizes as breathable.

Furthermore, to avoid the use of deicers dur-ing the first winter season experienced by the exterior concrete, it is highly recommended to simply broadcast sand for better traction.

As always, the use of proper curing tech-niques is highly dependent upon construction planning and its ability to accommodate spe-cial performance needs of exterior concrete design. Too often, planning is ignored for reasons of costs, schedule and weather con-straints. However, giving full consideration to proper curing techniques is key to a success-ful project—one that will withstand the test of time for years to come.

Length of moist curing, days

No.

of c

ycle

s of

free

zing

and

thaw

ing

to

prod

uce

a 25

% lo

ss in

wei

ght

W/C ratio = 0·45

Average

W/C ratio = 0·80

W/C ratio = 0·82

Influence of duration of moist-curing time on freezing and thawing durability of concrete, also as a function of w/c (Murdock, Brook, and Dewar 1991).

Part Two | continued from page 2

CONSIDER THE CURE

In part one of this series (Summer Issue 2014), AET discussed the critical role proper concrete curing practices play in the longevity and performance of exterior concrete. In part two (Fall Issue 2014), we focused on parameters that affect curing such as, given our geographical location, cold-weather construction. In this third and final article of our series, we explore meth-ods—as outlined by the results of a recent Minnesota Concrete Council (MCC) study—for achieving the best results possible from late-season placement of exterior concrete.

Freezicles and Call BacksIn our first article of this series, Terry Swor and Gerard Moulzolf described the winter of 2013-2014 as “brutal to exterior concrete performance.” To properly understand this characterization, it is important to compare the environmental conditions in the Twin Cities during this time (3.5 inches of precipi-tation) to the most recent winter (2014-2015), which experienced only 1.9 inches of precip-itation.

However, the amount of precipitation alone is not what causes a winter to wreak havoc on early-age concrete; the combination of the amount of precipitation and the number of freeze-thaw cycles is what determines if marginal concrete and concrete placement/curing practices will be able to resist scal-ing. When a precipitation event proceeds a freeze-thaw cycle, AET affectionately calls it a “freezicle.”

Freezicles cause water to move in the concrete matrix from where it cannot freeze—in the small gel and capillary pores—to where it can freeze, such as in air voids and larger capillaries. This movement

of moisture causes internal hydraulic and osmotic pressures that may result in scaling. Concrete that has the proper water/cementi-tious ratio, air-void system, finishing, and, last but not least, proper curing, will have the best chance of resisting the detrimental effects of freezicles. (AET’s second article extolled the benefits of even a minimal dura-tion (i.e., four days) of wet cure in improving both the scaling resistance and freeze-thaw durability of late-placement exterior concrete.)

To continue our comparison of the last two winters in the Twin Cities: Winter #1 (2013-2014) experienced 24 freezicles, while winter #2 (2014-2015) experienced only seven freezicles. A less scientific but possibly more accurate quantification of the severity of the two winters is a measure of owner dissatis-faction, which is evidenced by the number of requests AET receives to identify the cause(s) of concrete distress. We call these requests “call backs.” Between the dates of April 1 and June 16, 2014, AET performed 173 call backs. Conversely, we have yet to be involved in any call backs for exterior concrete that was placed late in 2014.

MCC Laboratory StudyMany of the call backs experienced during the spring of 2014 were late-season place-ments of 2013. In response to the inordinate number of call backs, the MCC undertook a study titled “Scaling of Late Season Concrete Placements.” The goal of the study: to explore methods that could opti-mize the scaling resistance of exterior concrete during a late-season placement.

The study consisted of a 23 factorial statisti-cal design laboratory phase and a 15 yd3

field placement phase. It considered these three independent variables:

1. Curing time2. Type of sealer3. Deicer exposure

All laboratory specimens had a curing interval comprised of an initial water cure for 50% of the time followed by an air cure for the second half before being subjected to a freezicle. Some specimens, as shown in the table below, were given a four-week curing interval before being subjected to a freezicle, whereas others were given two- and three-week curing intervals. Thus, all specimens were subjected to better-than-average curing environments for late-season placement of exterior concrete.

The dependent variable (response) was scal-ing, which was determined in the laboratory by ASTM C672 “Standard Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals.” The test, by its very nature, is aggressive—it is designed to characterize scaling of exterior concrete during a normal service life.The table above gives a summary of the study’s design and results.

Responses to each of the ten factorial points can be seen in the last column of the table above (scaling rating).

The following two graphs illustrate the average of the scaling responses of the samples, based on curing interval and sealer application.

Curing

Part Three | continued on page 5

CONSIDER THE CURE – PART THREE: MOTHER NATURE HAS CONTROL ORIGINALLY PUBLISHED IN THE FALL 2014 AMERICAN EDGE

BY TERRY SWOR, PG, AND DAN VRUNO, PE – AET SAINT PAUL

These test-in-place research samples demonstrate the importance of curing. Improperly cured concrete (left) dis-plays telltale signs of scaling distress. Properly cured and

2.6

1.75

1.1

0

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CONSIDER THE CURE

The graph above shows that concrete that has been allowed to cure for four weeks before it is subjected to freezicles experi-ences significantly less scaling than concrete that was given only two weeks of cure time.

Sealers

The effectiveness of early application of penetrating sealers can be seen in the graph below. The use of 8% siloxane resulted in the concrete with the lowest scaling rating (i.e., the highest resistance to scaling). However, it should be noted that the MCC

study prepared the laboratory test speci-

mens with an optimal curing environment before subjecting the specimens to the scal-ing test. This curing regimen rarely happens in the practical world of late-season exterior slab placements. As such, if specimens with and without penetrating sealers had been tested without receiving the water curing, it is likely all of the specimens would have resulted in higher scaling ratings. Moreover, the performance results should not be viewed as an endorsement of the siloxane penetrating sealers over those comprised of silane. We have seen other studies find the opposite results, although both penetrating sealers were shown to improve the perfor-mance of concrete.

Summary

The significance of the MCC study for AET’s “Consider The Cure” series relates to the practicalities of modern scheduling, which does not always give priority to proper curing. Exterior concrete slabs are particularly vulner-able as late-season placements given that the slab surface area is so large in comparison to the thickness or mass of the concrete. As we discussed in part two of this curing series, cold weather puts early age concrete at risk. Therefore, it is imperative to plan—and to implement adequate cold-weather protection and curing.

Nevertheless, a heuristic approach that prescribes a consistent curing plan for late-

season placement will not always work. As the comparison of the weather data for the past two winters revealed, it is often Mother Nature that determines whether or not a curing plan can be implemented. The MCC study provides substantiation for the recom-mendation provided by Dr. Peter Taylor for late-season concrete placements: If water curing is not possible due to weather, consider using a penetrating sealer to improve the performance of exterior concrete!

We trust the information in this three-part series will help you to consider the cure.

A full presentation of the MCC study’s findings will take place at MCC’s fall breakfast meeting, which will be held on October 22 at Midland Hills Country Club in St. Paul, MN. AET’s Dan Vruno will be one of the presenters. For more information, visit www.mnconcretecouncil.com. The timing of the presentation will, of course, coincide with when the industry is most interested in late-season placement of concrete.

Thank you for considering the cure.Contact the Authors of This SeriesTerry Swor is Chairman of the Board. He can be reached at tswor@amengtest.com.

Gerard Moulzolf is a vice president over-seeing AET’s petrographics and chemistry groups. He can be reached at gmoulzolf@amengtest.com.

Dan Vruno is a principal engineer and can be reached at dvruno@amengtest.com.

The scaling response of the laboratory specimens was rated as follows: 0 – no scaling; 1 – very slight scaling (3 mm depth, no coarse aggregate visible); 2 – slight to moderate scaling; 3 – moderate scaling (some coarse aggregate vis-ible); 4 – moderate to severe scaling; 5 – severe scaling (coarse aggregate visible over entire surface), photo at left.

Factorial Points Curing Sealer Deicer Exposure Scaling Rating

1 4 weeks 8% siloxane CaCl2 0

2 4 weeks 40 % silane CaCl2 0

3 4 weeks None None 1

4 4 weeks None CaCl2 3.5

5 2 weeks 8% siloxane CaCl2 2

6 2 weeks 40 % silane CaCl2 3

7 2 weeks None CaCl2 4.5

8 2 weeks None None 1

9 3 weeks 8% siloxane CaCl2 1.5

10 3 weeks 40 % silane CaCl2 2

2.5

1.7

1.2

0

0.5

1

1.5

2

2.5

3

No Sealer 40% Silane 8% Siloxane

Scal

ing

Rati

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5800.972.6364 • WWW.AMENGTEST.COM

Part Three | continued from page 4

The production, delivery, placement and finishing of concrete is a complex process—and is influenced by many factors. To achieve strong, durable and aesthetically pleasing cast-in-place concrete, you must be prepared to anticipate and address critical elements, especially when conditions are less than ideal.

To help you gauge your level of prepared-ness, we’ve assembled the short quiz below. Choose an answer for each question, and check your responses against the answer key on page 3. Should you have any questions regarding this topic, please send them to us at info@amengtest.com and we’ll include our response in the next American Edge.

1. According to the American ConcreteInstitute, cold weather is defined as “aperiod when for more than threesuccessive days the average dailytemperature drops below 40 °F and staysbelow 50 °F for more than one half of any24 hour interval.” T or F

2. The earliest recorded summer date for atemperature below 32 °F in Minnesota isSeptember 13. T or F

3. A temperature below 32 °F has neverbeen recorded in Minnesota past May 15.T or F

4. The reaction between cement and wateris termed “exothermic” and results in thegeneration of heat. T or F

5. The hydration of cement is negligibleat 29 °F and is nonexistent at 14 °F.T or F

6. Concrete attains its full potential strength best when the curing temperatures arebetween 40 °F and 80 °F. T or F

7. Mix proportions do not influence theproper hydration of cement. T or F

8. The reaction time for the hydration ofcement is doubled by every 20 °F changein ambient temperature. In other words,if the temperature drops 20 degrees, thecement hydration process will take twiceas long. T or F

9. The setting of concrete doesn’t impactthe workability or finishing of a concreteplacement. T or F

10. The early-age strength of concrete needsto be at least 500 PSI to be able to resistone freeze-thaw cycle withoutexperiencing internal damage. T or F

11. The greatest number of requests forinsulation blankets to be delivered to aconstruction site for both soil andconcrete protection are made inDecember. T or F

ANSWER KEY:1. T; 2. T; 3. F The latest recorded springdate for a temperature below 32 °F is May25.; 4. T; 5. T; 6. F Concrete attains its fullpotential strength best when the curing tem-peratures are between 50 °F and 70 °F; 7. FMix proportions, along with ambient tem-perature, concrete volume, and insulation,do influence the proper hydration of cement;8. T; 9. F The setting of concrete does impactthe workability or finishing of a concreteplacement; 10. T; 11. T

Determine Your Readiness ScoreNumber of Correct Answers:0 to 4 ........................................Brrr! Freezing4 to 7 ..................................Prone to Frostbite8 to 10 ........................Ahhh! Warm and safe

QUIZ: SCORE YOUR READINESS FOR COLD-WEATHER CONCRETE PLACEMENTS

GO PAPERLESSTo sign up for electronic delivery and manage other AET communications subscriptions,please visit www.amengtest.com/newsletters

American Engineering Testing, Inc.550 Cleveland Avenue NorthSaint Paul, MN 55114

BY TERRY SWOR – AET SAINT PAUL

6

www.amengtest.com800.972.6364

AET Consulting ServicesAIR QUALITY SERVICES• Air permit applications• Ambient air monitoring• Stack emissions monitoring• New source review• PSD applicability determinations• Air contaminant monitoring• Facility auditing

BUILDING FORENSICS• Structural collapse/failure• Fire and storm damage• Condition assessments• Ground Penetrating Radar (GPR)• Mold/microbiological/bioaerosol• Water leakage/infiltration• Thermal surveys• Cracking, deterioration, and corrosion• Preservation services• Flooring problems

CEMENTITIOUS MATERIALS PETROGRAPHY• Alkali-silica reaction (ASR)• Alkali-carbonate reaction (ACR)• Coefficient of thermal expansion• Delayed Ettringite Formation (DEF)• Cracking• Fire damage• Low strength• Popouts• Aggregates• Scaling or spalling• Delamination• Freeze-thaw

CONSTRUCTION SERVICES• Excavation observations• Piling and drilled pier observation• Geopier observations• Soil testing• Concrete testing• Masonry testing• Aggregate testing• Admixture testing• Repair materials testing• Concrete mix designs• Special Inspections• Vibration monitoring• Building condition surveys• Floor flatness testing• DOT field/lab testing/observation

ENVIRONMENTAL SERVICES• Phase I & Phase II ESAs• Brownfield redevelopment, grants• Storm/waste water infiltration• Asbestos assessments• Hazardous material assessments• Remedial investigations• Treatability/feasibility studies• Wastewater discharge monitoring• Geoprobe investigations• Monitoring well installation• Underground tank assessments• Ground water modeling• Dredge sediment testing/permitting• Spill Prevention, Control, and

Countermeasure (SPCC) planning

GEOTECHNICAL ENGINEERING AND EXPLORATION• Soil borings/rock coring• Engineering analysis and reports• Structural foundations• Infrastructure• Ground improvement• Earth structures• Forensic evaluations• Piezocone/pressuremeter/vane shear• Laboratory testing• Dynamic pile testing

PAVEMENT SERVICES • Advanced bituminous testing• Falling Weight Deflectometer (FWD)• Pavement design optimization• Ground Penetrating Radar (GPR)• Construction QC/QA testing• Stabilized full depth reclamation and

cold in place recycling mix designs• Pavement rehabilitation design• Pavement condition surveys

CHEMICAL ANALYSIS• Wet chemistry• X-ray Diffraction (XRD)• X-ray Fluorescence (XRF)• Cement chemistry• Fourier Transform Infrared (FTIR)

NONDESTRUCTIVE TESTING (NDT)• NDT consulting• Fireproofing testing• Welding consulting• Welding monitoring

Vertical construction

Energy

Transportation

TRUST DELIVERED.American Engineering Testing (AET)provides geotechnical, environmental, materials and forensic engineering, testing, and laboratory services in a broad range of market sectors including agriculture, transportation, energy, government and commercial. Our services include:

General Firm InformationFirm name: American Engineering Testing, Inc. (AET)Subsidiary of: American Consulting Services, Inc. (ACS)Ownership: Employee-ownedLegal status: S-CorpLeadership: CE0/Chairman, Terry Swor, PG; President, Dan Larson, PE

Locations

American Engineering Testing (AET) is an employee-owned corporation providing geotechnical, environmental, materials and forensics consulting and testing services to public and private sector clients in a broad spectrum of industries. Our headquarters are in St. Paul and our service area is expanded by offices in Minnesota: Albertville, Duluth, International Falls, Mankato, Marshall, and Rochester; Wisconsin: Chippewa Falls, Menomonie, Wasau, and Green Bay; South Dakota: Rapid City, Pierre, Sioux Falls, and Beresford; Williston and Dickinson, North Dakota; Gary, Indiana; and Palatka, Florida.

Working Philosophy

We embrace hands-on participation of principals and senior-level personnel in daily project work. This experienced perspective enhances the quality and timeliness of our services and strengthens the overall ability of project team members to handle unforeseen conditions effectively. We feel it’s a key reason AET is a recognized leader in the geotechnical, environmental and materials fields.

AET is committed to assigning field personnel who can performinterdisciplinary tasks (both environmental and geotechnical), depending on site conditions and project schedules. Upon identification of the specific project schedules and final scope of work, we coordinate field personnel for specific services to minimize costs, such as providing a qualified, experienced field technician to conduct environmental, asbestos and geotechnical testing activities on a site.

HISTORY1971 – Founded in Roseville, MN as Geotechnical Engineering Corporation (GEC)

1990 – GEC renamed American Engineering Testing, Inc.,moved to St. Paul Midway area

2004 – Acquired GME

2010 – Acquired service lines from Tetra Tech, Inc.

Honors and Awards

2014 - Midway Chamber of Commerce Large Business Award

2014 - ACEC/MN Honor Award

2012 - ASCE OPAL (Outstanding Projects & Leaders) Sustainability Award2012 - MCA Award of Excellence for New Sustainable Concrete Mix Design2012 - ACEC/MN Grand and People’s Choice Awards

2011 - MEI Award in Sustainable Communities category

2011 - ACEC National Recognition Award

2011 - ACEC/MN Grand Award

2011 - MnSPE Seven Wonders of Engineering Award

2010 - ACEC/MN Honor Award

2009 - ACEC/MN Honor Award

2009 - MSPE Merit Award

2008 - ACEC/MN Honor Award

2008 - MSPE Merit Award

2007 - Roads & Bridges #1 Road

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Locations Map

1. Williston, ND2. Dickinson, ND3. Rapid City, SD4. Pierre, SD5. Sioux Falls, SD6. Beresford, SD7. Marshall, MN8. Mankato, MN9. Albertville, MN10. International Falls, MN

11. Saint Paul, MN12. Duluth, MN13. Rochester, MN14. Menomonie, WI15. Eau Claire, WI (NDT field)16. Chippewa Falls, WI17. Schofield (Wausau), WI18. Green Bay, WI19. Gary, IN (NDT field)20. Palatka, FL (NDT field)

Nondestructive Field OfficesEau Claire, WI; Gary, IN & Palatka, FLContact: Dave Fitterer, ASNT, III Toll Free: 800-972-6364dfitterer@amengtest.com

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Bill Rebel

ContactsPetrographics

Gerard Moulzolf, PG, Vice President

Email: gmoulzolf@amengtest.com

Direct: 651.659.346

Mobile: 612.616.6155

Chris Tillema, Sr. Petrographer

Email: ctillema@amengtest.com

Direct: 651.659.1353

Megan Huberty, Petrographer

Email: mhuberty@amengtest.com

Main: 651.659.1328

Construction Materials Testing

Willy Morrison, Construction Laboratory Manager

Email: wmorrison@amengtest.com

Direct: 651.659.1333

Mobile: 847.902.7548

Dan Vruno, PE, Principal Engineer

Email: dvruno@amengtest.com

Direct: 651.659.1334

Chemistry

Bill Rebel, Principal Chemist

Email: brebel@amengtest.com

Direct: 651.603.6633

Gerard Moulzolf, PG

Willy Morrison

EXTENSIVE RESOURCESVice President Gerard Moulzolf, PG and Principal Petrographer who has been with AET for 25 yrs.

Willy Morrison, Concrete Laboratory Manager, formerly with CTL Group and Wiss, Janney, Elstner Associates

Bill Rebel, Principal Chemist, formerly of Rebel Construction Chemistry (RCC) and CTL Group

Chris Tillema, Senior Petrographer, has 20 years of petrographic experience

Cyler Hayes, Senior Chemist, formerly of CTL Group, has 25 years of experience with exten-sive knowledge of coat-ings, admixtures, and adhesives

John Beaty, PhD., Historic Preservation Specialist, provides in-depth experience of historic preservation, historic mortars, and provenance

www.amengtest.com800.972.6364

Concrete and Aggregate AnalysisAET’s Petrographics department specializes in the microscopic analysis of concrete and its aggregate mixes. Almost every concrete-related distress can be diagnosed through optical microscopy (petrography) following ASTM C856 guidelines. Problems such as Alkali Silica Reaction (ASR), Alkali Carbonate Reaction (ACR), Delayed Ettringite Formation (DEF), freeze-thaw scaling, spalling, cracking and low strength are routinely documented through thorough petrographic analysis of concrete. All forms of cementitious-based materials, such as concrete, mortar, repairments, grout, block and pavers can be analyzed.

Our reports include full photographic documentation of our investigations which allows our clients to understand our reports and conclusions.

At AET, we go the extra step for you in terms of timeliness. Knowing that turnaround can be critical to your project, we can provide verbal test results quickly for priority investigations.

In concrete aggregates, AET can analyze:

• Alkali carbonate reactivity (ACR)• Alkali silica reactivity (ASR)• Freeze/thaw deterioration (D-cracking)• Wet/dry deterioration• Popouts• Staining• Low strength problems

Our extensive list of analyses include:

• ASTM C295: petrographic analysis of aggregate• ASTM C117 and C136: gradations• ASTM C142: clay lumps and friable particles• ASTM C40: organic impurities• ASTM C127 and C128: specific gravity and absorption• ASTM C123: lightweight particles• ASTM C29: unit weight• ASTM C131 and C535: abrasion loss• ASTM C88: sulfate soundness• ASTM D4791: flat and elongated• ASTM D5821: fractured particles• ASTM C227, C1260, and C1293: alkali silica

physical tests in mortar and concrete• ASTM D4992, D5312, D5313, and D6473: analysis

for rock used as erosion control (rip rap)

Petrographic analysis

Concrete cores prepared for microscopic analysis

Concerns are identified and assessed

TRUST DELIVERED.AET will perform petrographic analysis (ASTM C295) on any type of aggregate source, including synthetic aggregates.

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Construction Materials Testing - Physical Whether you are measuring the compressive strength of a concrete cylinder or conducting long-term creep and shrinkage tests, AET can evaluate and pre-qualify construction materials via our impressive range of laboratory testing and analysis services. We offer over 300 standards-based concrete and cementitious product tests, one of the largest lists of services in the industry.

We participate in the Concrete and Cement Reference Laboratory (CCRL) program. As part of this program, a comprehensive examination of AET’s laboratory procedures and equipment is conducted biannually. Also, AET is recognized and certified by AASHTO and validated by the Corps of Engineers. AET is active in technical organizations such as ASTM, ACI, and PCI, and participates in the development, adaptation and implementation of many test standards.

Test schedules are developed to meet your needs including rush services to minimize or eliminate your project downtime. Test results are reported promptly. For long-term tests such as creep and shrinkage, alkali-silica reactivity, and admixture evaluations, interim results are provided.

Our extensive list of tests include but aren’t limited to:

• ASTM C666 Resistance of Concrete toRapid Freezing and Thawing

• ASTM C512 Creep of Concrete in Compression• ASTM C1260 Potential Alkali Reactivity of Aggregates• NT Build 492 Chloride Migration Coefficient• AASHTO T336 Coefficient of Thermal Expansion of Concrete• ASTM C465 Processing Additions for use in Cement• ASTM C1293 Length Change of Concrete

Due to Alkalai-Silica Reaction

10,000+ square feet of laboratory space includes:

• Numerous controlled environmental rooms (-10°F to 130°F,some with controlled humidity)

• Seven freeze-thaw chambers• Compression testing machines with capacities from several

pounds to 650,000 pounds• 0oF walk-in-freezer• Specialized facilities for mix design verification, casting,

and curing of test specimens• A full service cement/mortar laboratory

Mass concrete analysis

ASTM C666 - AET has seven freeze-thaw chambers

ASTM C512 - Creep of Concrete in Compression

TRUST DELIVERED.AET brings unparalleled experience to standard and specialized testing of cements, aggregates, mineral admixtures, chemical admixtures, concrete, stone, and concrete products.

www.amengtest.com800.972.6364

Ground Penetrating Radar - ForensicsGround Penetrating Radar (GPR) is a useful nondestructive testing tool that can locate embedded objects in concrete, buried subsurface objects, conditions below the ground surface. GPR requires access to only one side of the element being scanned. The data is collected on-site by a portable computer module where it can be reviewed on-the-spot to mark out locations for coring or cutting of concrete. GPR and it’s software can be used to document the depth to embedded reinforcing steel, voids, spacing and thickness of concrete.

AET has used GPR radar equipment everywhere from airport terminals and sports arenas to retirement homes and nuclear power plants.

Applications

The 1500 MHz antenna can help locate items such as the following metallic and non-metallic objects in concrete/masonry up to 24” thick:

• Reinforcing steel• Post-tensioned tendons• Encased steel beams or columns• Conduit and piping• Voids and delaminations• Deteriorated concrete• Concrete or bituminous thickness• Grouted or ungrouted masonry cells

The 400 MHz or lower-frequency antenna records images in soil up to a depth of 10 - 30 feet. This can detect conditions such as:

• Underground storage tanks• Utility lines• Foundations• Bedrock contact surfaces• Stratigraphic mapping, sinkholes• Voids or cavities

Impact Echo

The impact echo nondestructive testing method is used accordance with ASTM: C1383, “Measuring the P-Wave Speed and Thickness of Concrete Placed Using Impact Echo,” to document the thickness of concrete and to indicate a potential for internal flaws or cracks. This procedure is performed on concrete surfaces with a smooth finish. The test data will typically be collected on a grid pattern across the concrete in question and results will be compared at each location. This equipment measures to a maximum depth of approximately 36”.

Scanning for embedded reinforcing steel

Looking for drain tile in a educational facility

Impact echo testing in a parking ramp column

SAFE TECHNOLOGYGPR instruments do not emit harmful radiation. Normal business operations may be maintained while our GPR work is performed. There is no need to evacuate the areas being surveyed as required with x-ray or radiographic testing. The total power output of the unit is less than that of a CB radio.

www.amengtest.com800.972.6364

Aggregate Alkali-Silica Reactivity (ASR)Aggregate Alkali-Silica Reactivity (ASR) testing represents an integral part of laboratory testing services. We can test for this important parameter using accepted ASTM methods. AET is USACE-validated and AASHTO-accredited for all of these methods.

To determine AASHTO expansion, fine and coarse aggregates can be tested using materials provided. For specific projects, testing may be performed with the proposed materials for the new construction. Representative testing in early stages can minimize problems in the future.

Our scope of services for ASR testing:

Test Method Name of TestCompletion Time

Sample Size (lbs.)

ASTM C1260 Potential alkali reactivity of aggregates (Rapid Mortar Bar Method)

3 - 4 weeks10# Aggregate3# Cement

ASTM C1293 Length change of concrete due to alkali-sil-ica reaction

12 months minimum

200# Aggregate

ASTM C1567Potential alkali reactivity of aggregates with cement/supplementary cementitious material combinations

3 - 4 weeks10# Aggregate3# Cement3# Fly Ash/Slag

ASTM C227 Potential alkali reactivity of cement-aggre-gates combinations

6 months15# Aggregate5# Cementitious(of each size & source)

ASTM C289 Potential alkali-silica reactivity of aggregates (Chemical Method)

3 - 4 weeks 5# Aggregate

ASTM C295 Petrographic examination of aggregates for concrete

2 - 4 weeks5# Fine aggregate30# Coarse aggregate(of each size & source)

ASTM C856 Petrographic examination of hardened concrete

2 - 3 weeksFor rush orders: add 20% to cost

Concrete Cores

ABOUT ASRASR is the reaction between unstable silica in aggregates and the alkali in the cement paste, which produces an expansive gel. This reaction causes extensive cracking and expansion within the aggregate particles and ultimately damages the concrete itself. Common reactive aggregates include chert and shale as well as igneous and metamorphic rocks containing strained quartz.

As these reactions are driven by moisture, reactive aggregates used in exterior construction are typically the most susceptible. The reaction continues as long as reactive silica and moisture are available.

Contact:

Willy Morrison Laboratory Manager Direct: 651.659.1333 wmorrison@amengtest.com

Gerard Mouzolf, PG, VP Principal Petrographer Direct: 651.659.1346 gmoulzolf@amengtest.com

www.amengtest.com800.972.6364

Fourier Transform Infrared SpectrometerFourier Transform Infrared Spectrometer (FTIR) uses electromagnetic energy that upon interaction with a material can be collected to obtain an infrared pattern or infrared spectrum. Molecules absorb frequencies that are characteristic of their structure which allows identification by interpretation of the location, shape and intensity of spectra peaks. Solids, liquids and gases can be analyzed using infrared spectroscopy. Infrared spectroscopy is strongly associated with the identification of organic materials. In the construction industry, this includes polymers, coatings, adhesives, chemical admixtures, additives and is used for identification, trouble shooting, failure analysis and reverse engineering. FTIR is also a tool in the analysis of inorganic materials, including cement, SCMs, and aggregates. FTIR has numerous collection accessories; one is ATR (attenuated total reflectance) that allows samples to be analyzed with little or no sample preparation. It is an excellent complement to XRD, XRF and optical microscopy.

Processing an FTIR sample in the lab

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X-RAY DIFFRACTION (XRD)X-ray Diffraction (XRD) identifies unknown materials bydiffracting x-rays off of their crystalline structure, producing anindividual pattern which can then be searched against a standard library. XRD is very useful in identifying reaction products incementitious materials or in the identification of efflorescence.Further, aggregate petrography is enhanced through the useof XRD by identifying uncommon minerals or determining thepresence of a more reactive species or polymorphs of SiO2 such as cristobalite, tridymite and coesite. Our x-ray diffractometer andsoftware is capable of quantitative Rietveld analysis.

Samples are placed in small disc for XRD processing

Sample XRD results

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X-RAY Fluorescence (XRF)Wavelength dispersive X-ray Fluorescence (XRF) identifies and can quantify the elemental content of unknowns by exposing the materials (solids or liquids) to x-rays and measuring the created x-ray fluorescence radiation. The radiation produced is characteristic for each element. The intensity of the radiation is proportional to the concentration of each element in the sample. Wavelength dispersive XRF is unrivaled in terms of accuracy when utilized to measure the composition of portland cement, flyash, or other cementitious material to determine consistency in their production. Further, XRF is a useful tool in forensic work to determine the composition of unknown materials.

The XRF can process many samples, concurrently

Sample XRF results

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Ground Penetrating Radar for HighwaysGround Penetrating Radar (GPR) offers a non-destructive means of material analysis without coring or probing. GPR uses high frequency electromagnetic (radio) waves to measure material depths and determine where material types change. As the antenna moves continuously across the test surface it transmits short pulses into the substrate which is reflected back to the receiver and interpreted into a linear scan profile. The arrival time and strength of reflections determine and boundaries of dissimilar materials are profiled as the radio waves reflect back, identifying depth, extent, and locations of materials.

In pavements, GPR continuously collects data and measures layer thicknesses by identifying depths at which bituminous, concrete and aggregate base materials change. For most applications, data is collected at highway speeds without inconveniencing and compromising the safety of the traveling public with road closures. GPR data collected for pavement thickness is performed at a rate of one vertical scan per foot at 55 mph, with only a few cores recommended to be taken for confirmation of material types. Typical projects include identifying where pavement rehabilitation approaches, such as reclaiming depths for pavements and bases and mill and overlay depths, are most appropriate to avoid construction delays and claims.

GPR can also be used hand-held or walk-behind cart.

GRP is typically collected at 1ft intervals with data tied to GPS coordinates.

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3D views of concrete pavement and bridge decks can be generated from collected data.

GPR FOR STRUCTURES

Did you know that AET’s Building Technology Group can also use handheld GPR in concrete walls and floor slabs to identify the thickness of the walls, the location and orientation of reinforcement and voids or inconsistencies including depth and continuity of cracks in the material.

We can provide 3D imaging of the data and a pictorial interpretation on projects that include identification of thickness/voids beneath floor slabs or behind walls and identification of the placement of structural reinforcement where cracks are developing.

We can also use GPR to identify the severity and extent of cracking for concerns of structural integrity and safety. Thickness profile of an Alaskan highway pavement.

Contact:

Chunhua Han, PhD, PE651.603.6631 directchan@amengtest.com

David Rettner, PE651.755.5795 directdrettner@amengtest.com

www.amengtest.com800.972.6364

QA/QC and Laboratory AccreditationAmerican Engineering Testing, Inc. (AET) has an operating Quality Assurance Program (QAP) that guides our staff during technical work. The QAP requires use of standard methods for sampling, observations, testing, documentation and reporting. All personnel, procedures, equipment and materials used in the course of our work are in compliance with the QAP which is designed to comply with the requirements of ISO/IEC Standard 17025 General Requirements for the Competence of Testing and Calibration Laboratories.

AET’s QAP provides compliance with the requirements of these ASTM standards:

ASTM:C1077 Standard Practice for Laboratories Testing Concrete and Concrete Aggregates for use in Construction and Criteria for Laboratory Evaluation

ASTM:C1093 Accreditation of Testing Agencies for Unit Masonry

ASTM:D3666 Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials

ASTM:D3740 Minimum Requirements for Agencies Engaged in the Testing and/or Inspection of Soils and Rock as used in Engineering Design and Construction

ASTM:E329 Standard Specification for Agencies Engaged in the Testing and /or Inspection of Materials used in Construction

ASTM:E543 Standard Practice for Agencies Performing Nondestructive Testing

Laboratory Accreditation

AET’s locations in Saint Paul, Rochester, Duluth, Wausau and Sioux Falls are accredited by the AASHTO Materials Reference Laboratory (AMRL) in geotechnical and construction materials engineering and testing. Assessments are conducted according to the AASHTO R18 standard: Establishing and Implementing a Quality System for Construction Materials Testing Laboratories. Our QAP meets the requirements of the US Army Corps of Engineers (USACE), and our Saint Paul and Duluth locations carry a laboratory validation designation by the USACE.

AET’s Environmental Field group in Saint Paul is accredited by the American Association for Laboratory Accreditation (A2LA) signifying that our staff and our quality system have been evaluated by a third party assessor. Copies of accredited test methods are available upon request.

ACCREDITED

COMPLIANCE

AET conducts annual internal audits to assess the effectiveness of implementation of our Quality Assurance Program and measure compliance with the 17025 standard.

Personnel are trained in the Technical Standard Operating Procedures (T-SOPs) performed, are certified either externally by Mn/DOT, Wis/DOT, SD/DOT, NICET, ACI, ICC or other recognized certifying authority, or internally by AET.

AET regularly participates in relevant CCRL (Cement and Concrete Reference Laboratory) and AMRL (AASHTO Materials Reference Laboratory) proficiency test programs.

Test and inspection equipment meets industry and procedural requirements, is maintained in proper working order, and is in current calibration with traceability to national standards such as those maintained by the National Institute of Standards and Technology (NIST).

Contact:

Tracey Lee, QA/QC Manager651.659.9001 maintlee@amengtest.com