Tennessee Concrete Winter 2022 Magazine

WINTER 2022 Volume 36, No. 3

GOING BEYOND ACI 332 ENHANCED DURABILITY CONCRETE

See page 8

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contents

WINTER 2022, VOL. 36, NO. 3 TENNESSEE CONCRETE magazine is published for the Tennessee Concrete Association— 3026 Owen Drive Antioch, TN 37013 Phone: 615.360.7393 Fax: 615.360.6670 Website: www.tnconcrete.org

4

PRESIDENT THANK YOU TO TCAs ANNUAL SPONSORS

by Sam Pittenger

Publisher: Kahoy Group, LLC Editor: Alan Sparkman Advertising Director:

6

EXECUTIVE DIRECTOR 2022 DRAWING TO A CLOSE

by Alan Sparkman

J. Morris Woods Art Direction: Donna G. Heninger For advertising rates and information, contact Morris at 800.315.9950 x602.

Subscriptions in US, free upon request.

Outside US, $12 per year. To subscribe, contact TCA at the above address.

Articles appearing in Tennessee Concrete are frequently contributed by outside, independent sources.

Conclusions drawn from these articles may be at variance with the opinions of our readers.

Tennessee Concrete welcomes response and rebuttal and will make every effort to print these responses. Send comments to: Editor, Tennessee Concrete, 699 President Place, Suite 400, Smyrna, TN 37167.

Tennessee Concrete and its publishers assume no liability for errors or omissions in articles or advertisements appearing in Tennessee Concrete. © 2022 Kahoy Group, LLC All rights reserved. The contents of this publication may not be reproduced by any means, in whole or in part, without the prior written consent of the publisher.

7

2023 ANNUAL CONVENTION FEBRUARY 8–10 RETENTION AND TRAINING Marriott-Franklin Cook Spring

8

GOING BEYOND ACI 332

COMMERCIAL/RESIDENTIAL ENHANCED DURABILITY CONCRETE: PHASE III — THE EFFECT OF LIMITED CURING

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman, and John Pearson

17

TECHNICAL DIRECTOR THE RIGHT TOOL FOR THE JOB

by John B. Pearson, P.E.

18

CIM UPDATE Middle Tennessee State University Officially Opens the New School of Concrete and Construction Management Building WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  3

PRESIDENT’S MESSAGE

THANK YOU TO TCAs

ANNUAL SPONSORS

B Sam Pittenger TCA President

Moving back to Davidson County: 3026 Owen Dr. Suite 101 Antioch, TN 37013

y the time you read this TCA should

are already working for us. We have a great

be moved into their new home. We are

morning session lined up with some outstanding

back in Davidson County in the Cane Ridge/

speakers (see the Annual Convention schedule

Antioch community where your TCA staff

included in this issue) who will address labor

is busy outfitting our new Concrete Lab and

force demographics, fire and building codes,

Training Room, along with the rest of the space.

and improving your personal use of technology.

I would like to say a special Thank You to all

Plus, we will hear an update of the CIM program

of our TCA members who contributed to help

from CIM Director Jon Huddleston.

us outfit the Lab! And, please feel free to stop

Our Annual Concrete Design Awards

in and visit our new space on your next trip

presentation will be held during lunch, so if you

to Nashville. Our new address is 3026 Owen

haven’t sent your projects in to be considered

Drive, Suite 101, Antioch, TN 37013. The

put that on your immediate TO-DO list! The

office is conveniently located just off of I-24,

Design Awards celebrate the best projects and

Exit 62, on the southeast side of Nashville.

the best people in our industry — make sure

I would also like to thank all of TCA’s Annual

Annual Concrete Design Awards will be held during lunch

A special thanks to TCA's Annual Sponsors

your projects and people don’t get left out.

Sponsors, both Presenting and Platinum. For

Our afternoon session this year is special

2022, we had a total of 18 annual sponsors

and is designed to help you start the process

— a record number! Our Annual Sponsors

of improving your organization’s retention

show their commitment to our organization

program. This will be a hands-on workshop

with financial support above and beyond their

lead by retention specialist Cara Silletto of

annual dues. Their support makes it possible

Magnet Culture. This workshop is designed

for TCA to provide a higher level of service to

for you and your workforce team to kickstart

all of member companies, so please support our

your efforts and to keep the great people you

sponsors by giving them the first opportunity to

already have. So, please consider bringing your

earn your business. We are signing up Annual

key workforce people to the TCA Convention

Sponsors for 2023 right now. Please consider

to be part of this dynamic opportunity.

adding your organization to this great group of TCA supporters.

Finally, I would like to extend my personal invitation for you to attend our 2023 Annual Convention (February 8–9, 2023, at Franklin/ Cool Springs Marriott). Our focus this year will be on Workforce with special attention on how we can retain the employees who

4  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

All of this is included in your Annual Convention registration (thanks in large part to that great group of TCA Annual Sponsors!) so get your team signed up today.

Looking forward to seeing you at the Convention! ■

– 1225 Parkway – Sevierville, TN 37862

DENNIE UNDERWOOD (865) 453-4433 (phone) (865) 428-6083 (fax) (865) 654-2912

SICALCO, LTD is your concrete industry partner since 1979

Heath Rogers, Middle Tennessee Christopher.Rogers@Holcim.com www.Holcim.US

Benoit Cotnoir, Area Sales Manager Benoit.Cotnoir@Holcim.com www.Holcim.US

Contact our service center @ 800-435-1919 or general offices at 630-371-2655 for customer service

Corporate Office: (731) 968-2537 P.O. Box 1090 • Lexington, TN 38351 Radio Dispatched GPS Trucks for Fast Dependable Service

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(731) 686-2288 714 West Main, Suite 205 • Murfreesboro, TN 37129 205  Nashville, Tennessee 37220-13 (731) 642-66724825 Trousdale Drive, Suite(615) 333-9882 Fax (615) 333-9883 FAX (615) 333-9882 (731) 885-7060

"Building the South with top quality ready mix concrete & masonry products at a resonable price."

(615) 333-9883

WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  5

E X E C U T I V E D I R E C T O R ’ S M E S S A G E — A L A N S PA R K M A N

2022 DRAWING TO A CLOSE 2022

is rapidly drawing to a close. It has been (and continues to be) a busy year for the concrete industry across the state in spite of numerous challenges like material availability and of course finding and keeping good people. Concrete production in Tennessee through mid-year is slightly above the record concrete production that we posted in 2021 in spite of all these challenges. The outlook for 2023 is clouded by a number of unknowns but most forecasters are not predicting a dramatic drop off in construction activity, even though many are predicting a slowdown in the rate of growth, or even a small (3 to 5 percent) decline in overall construction activity.

Even if we see a slight drop in construction activity the concrete industry (and most other industries) will continue to scramble to find enough people to operate their business. The NRMCA reports in their recently released Mixer Driver Recruitment and Retention Survey that our industry continues to lose drivers at a high rate with a 28 percent quit rate (above the national average for all industries of 25 percent). The survey also documents that our overall number of drivers in the concrete industry is not growing while the amount of concrete production continues to grow year-over-year. This means that the majority of ready mix producers (about 70 percent) report they don’t have enough drivers to fully service their business and are losing yardage because they don’t have enough drivers to carry those loads.

The survey also documents that the median age of a ready mix operator is 47 years old, slightly above the national average for all industries. This means that half of our current driver pool is over 47 years old and we will lose many drivers from our pool as they retire, in addition to the large number who quit for

other reasons. While this is not necessarily a new problem it will become an increasingly urgent problem for one very important reason — demographics.

U.S. population growth has been below replacement level for nearly 50 years with the end result of having fewer people enter the workforce than will be exiting the workforce, especially as the Baby Boomer generation retires. For industries like construction this is especially troubling as we typically hire our replacement workers from this youngest portion of the population. We will be facing this shortage of new workers for many years and there is no quick fix.

While this is sobering it is also something we can see coming and thus plan for. TCA is putting together our 2023 Annual Convention program with this in mind so I encourage you to attend and soak up timely, relevant information that will be critical to your future planning for your organization. Our kick-off speaker (on Thursday, Feb. 9, 2023) is an expert on demographics and how this will impact the workforce of the very near future. Plus, we have put together an entire afternoon session that will focus on retaining the workforce you already have — one person retained is one that you don’t have to replace.

This session will be interactive and hands on, not just a slide deck. It is designed to guide your organization through the process of creating your own retention plan so you will leave the session with a critically important building block for your organization’s future.

Plan to bring your workforce team to the Convention so you can participate in this vital workshop.

TCA’s ability to bring this caliber of speakers to our membership is due in large part to our Annual Sponsors — so a big shoutout to those 18 companies that became Annual Sponsors in 2022. We are recruiting 2023

Annual Sponsors right now so please consider joining this elite group of TCA members!

Plan to stop by and visit TCA in our new space located at 3026 Owen Drive, Suite 101, Antioch, TN 37013. We look forward to giving you a personal tour!

6  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3 677247_Chryso.indd 1

1/22/14 8:54 PM

2023 ANNUAL



FEBRUARY 8–9

CONVENTION

RETENTION AND TRAINING

REGISTRATION FEES AND SPONSORSHIP OPPORTUNITIES • Annual Convention Registration: $575 • Annual Convention Award Winner Lunch Ticket: $150 Intended for family members of winners, co-workers, and extended project members beyond the Ready Mixed companies. Not needed with full convention ticket purchase!

• Eats & Drinks Sponsor: $375 • Tabletop Sponsor: $995 Includes one full convention registration and a tabletop for display at convention.

• Tabletop Sponsor Plus: $995 Includes one full convention registration and a tabletop for display at convention.

SCHEDULE Wednesday Evening

ROOM BLOCK Visit our website tnconcrete.org to access Room Block for the dates of Feb. 8–10.

Rooms are $189. For a room outside those dates, please call the hotel directly at (615) 261-6100.

5:30–6:30

Statewide Eats and Drinks Reception (near the bar)

Thursday

Morning • Afternoon • Evening

7:30*

Breakfast Buffet open

8:00

TCA Annual Membership Meeting and Election

8:15

Morning Technology Tip with Beth Z

8:30

The Demographic Drought: Bridging the Labor Gap with Ron Hetrick (via Zoom)

9:30

CIM Program Update with John Huddleston

10:00

Break (15 minutes)

10:15

Fire & Building Codes: How they Impact our Concrete Markets with Shimim Rashid-Sumar, NRMCA VP of Codes

11:15

Morning Summary and Lunch Instructions

11:30–1:00* Annual Concrete Design Awards Banquet 1:15–4:15*

MARRIOTT FRANKLIN COOL SPRINGS 700 Cool Springs Boulevard Franklin, TN 37067

Retention Workshop—Keeping Your Valuable Workforce with Cara Silletto

NEW! SPECIAL ONE-ON-ONE COACHING SESSIONS 30-minute time slots - $49 Each additional track 3–5 p.m.

(Only 4 slots available for each track.)

TECHNOLOGY UP How to use your tech more effectively.

Coaching provided by Beth Z — Your Nerdy Best Friend.

(NOTE: This is a hands-on workshop. You will leave with a plan to improve retention in your organization! Bring your team, e.g., HR, managers, etc., and get started on your plan to keep your workforce)

Friday 8:00–Noon

Morning

SOCIAL MEDIA Increase your understanding and improve your message. Coaching provided by Onwrd&Upwrd.

TCA Board of Directors Meeting & Breakfast (Invitation Only)

VISIT TNCONCRETE.ORG TO REGISTER OR SPONSOR! QUESTIONS, CONTACT TCA AT (615) 360-7393 *Included with your registration!

WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  7

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332:

Commercial/Residential Enhanced Durability Concrete: Phase III — The Effect of Limited Curing ABSTRACT An absence or shortened amount of curing time for Portland cement concrete can reduce the potential degree of hydration in that concrete. Adequate curing can increase the potential for hydration, the chemical reaction between cement and water, and thus potentially increase the amount of hydration products.

Hydration products not only increase strength, they also occupy the void space left by water used for hydration, creating a less permeable concrete matrix. Through these mechanisms, curing can increase both the strength and durability.

Curing concrete is often overlooked in practice due to its time-consuming process. Although the curing process can potentially slow down the progress of a project, it is crucial for the strength and durability development of concrete. Using a variety of common mixes (commercial 3500, commercial ACI, and CRED) and exposing them to limited various amounts of curing, the objective of this research is show how curing effects 28-day hardened properties.Six batches of each mixture were used. Sixteen four-inch by eight-inch cylinders were cast from each batch. The cylinders from each batch were divided into four sets of four and each cured for a different length of time (0, 3, 7, and 14 days). Surface resistivity, compressive strength, and split tensile strength were determined at 28 days. The effects of extended amounts of curing increased the benefits of strength and durability properties in 38 out of 54 instances.

The compressive strength yielded the most improvement due to longer amounts of immersion curing, however split tensile and surface resistivity also had improvements in results based on curing time.

INTRODUCTION AND LITERATURE REVIEW The process required to adequately cure concrete can be seen by many contractors as overwhelming or not worth the time and money. Common curing methods such as water ponding and the installation of wetted burlap, both for extended amounts of time, can stall the progress of a project and lead to scheduling problems.

However, the process of curing concrete ensures adequate strength 8  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

development and promotion of durability characteristics (1). A concrete’s strength is undoubtedly an important characteristic and is a main describing factor in its production, while the durability of a concrete impacts the longevity of a concrete’s service life. An absence or shortened amount of time allowed for curing can lead to a decrease in both the strength and durability in concrete (2).

The introduction of external water after a concrete’s final set provides moisture that can be used to keep the relative humidity (RH) of the concrete’s matrix high and provide extra water to further promote the hydration of Portland cement (2). The longer this external water is present, the more opportunity the concrete has to reach a higher degree of hydration. Hydration products take the place of the space previously occupied by the mixing water, so this promotion of hydration leads to more products being available to occupy what would have been permeable pore space, making the concrete stronger and less susceptible to harmful chloride ion penetration (3). Chloride ion penetration and sorptivity are durability problems in concrete that can lessen the service life of concrete and have been seen to be higher with concrete being only air cured (4).

An absence of external water after a concrete’s final set, or air cured, has been seen in studies, such as a comparative study by Goel, to cause a lesser compressive and tensile strength than a concrete that has been cured via water immersion or under plastic film. This decrease in strength properties was seen in early age (3-7 days) as well as late age (28-56 days) testing, the latter of which produced the biggest difference due to the higher degree of hydration from the immersion groups (5). According to a study

by Senbetta, a poorly cured concrete contained a chloride ion concentration of nearly 50% greater than a concrete that was well cured (6). This characteristic can lead to severe durability concerns for a concrete and lead to a shortened service life.

MATERIALS AND PROCEDURE The materials used in this experiment are shown in Table 1, Column 1. The three mixes chosen to be used in this study have been used in two previous phases of research and are meant to —Continued on page 20

TABLE 1. MATERIALS USED MATERIALS

COMMERCIAL 3500-PSI

COMMERCIAL ACI 332

CRED

375

451

312

Class F Fly Ash, (lbs/CY)

0

0

187.2

Class C Fly Ash, (lbs/CY)

150

113

0

0

0

20.8

No. 57 Stone, (SSD lbs/CY)

1816

1854

1911

River Sand, (SSD lbs/CY)

1281

1217

1252

250

250

203

6

5

6

1.1

1.1

0.6

Type I/II PC, (lbs/CY)

Metakaolin, (lbs/CY)

Water (lbs/CY) Design Percent Air Air Entrainer, (oz/cwt) Mid-Range Water Reducer (oz/cwt)

4.2

7.4

8.8

High-Range Water Reducer (oz/cwt)

0.0

0.0

7.3

TABLE 2. TYPE OF CURING LEADING UP TO AGE AGE (DAYS)

CYLINDER IDs

0 to 1

1 to 3

3 to 7

7 to 14

14 to 26

26 to 28

1–4

Mold

Air

Air

Air

Air

Immersion

5–8

Mold

Immersion

Air

Air

Air

Immersion

9–12

Mold

Immersion

Immersion

Air

Air

Immersion

13–16

Mold

Immersion

Immersion

Immersion

Air

Immersion

TABLE 3. 28-DAY SR RESULTS, kilohm-cm MIXTURE

Commercial 3500

Commercial ACI

CRED

CURING AGE (DAYS)

BATCH 1

BATCH 2

BATCH 3

BATCH 4

BATCH 5

BATCH 6

MEAN

RANGE

0

6.7

6.4

6.8

7.0

6.7

6.0

6.6

3.3

3

7.2

7.3

7.9

7.7

7.6

6.8

7.4

3.7

7

8.2

8.2

8.4

8.3

7.7

7.8

8.1

4.1

14

8.8

8.6

8.6

8.4

8.1

8.2

8.5

4.2

0

8.2

7.8

7.0

8.7

8.5

8.4

8.1

1.7

3

8.7

8.6

7.7

7.3

8.7

8.7

8.3

1.4

7

8.6

7.8

7.6

7.1

8.4

8.6

8.0

1.5

14

8.9

8.3

7.5

9.0

8.9

9.3

8.7

1.8

0

20.1

20.3

20.6

19.9

20.3

19.7

20.2

0.9

3

19.9

20.5

19.8

19.2

20.3

19.6

19.9

1.3

7

20.4

21.9

21.0

20.7

21.9

21.4

21.2

1.5

14

22.2

22.3

22.3

21.5

21.9

22.5

22.1

1.0

WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  9

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332:

Commercial/Residential Enhanced Durability Concrete: Phase III — The Effect of Limited Curing represent a spectrum of low to high end performance based off of strength and durability characteristics. This spectrum is displayed left to right across the top of Table 1. The percent substitution of Class F fly ash in CRED is still beyond the maximum percentage allowed by ACI 332 for concrete subjected to RF3 and RF4 exposure classes, as it was in Phases I and II (8).

Six 1.06-cubic foot batches of each mixture were made with each batch consisting of sixteen four-inch by eight-inch cylinders.

Sets of four cylinders within each batch were subjected to a certain amount of immersion curing time, namely 0, 3, 7 and 14 days. The lime-water immersion curing conforms to ASTM C192 specifications (9). Once the sets of cylinders had reached their prescribed amount of curing, they were removed from the immersion tank and left to air cure at room temperature. This curing schedule can be seen in Table 2.

At 28 days, three out of four cylinders of each set were tested for chloride ion penetration via surface resistivity (SR). SR measures the concrete’s resistance to harmful chloride ion penetration, so the higher the SR value, the less permeable the concrete is. In order to conform to SR’s test method, AASHTO T358-17, of testing saturated cylinders, every cylinder was placed back into the curing tank 48 hours prior to testing (10). This was done so as not to provide any additional curing as well as to provide moisture for adequate testing. Compressive strength and tensile strength

were also tested at 28 days, directly after SR had taken place due to its non-destructive nature. Two cylinders of each set were tested in compression, and the other two were tested in tension.

Compressive strength was tested in accordance to ASTM C39, and tensile strength was tested in accordance to ASTM C496 (11, 12).

RESULTS The results for SR of each mixture at each curing age is shown in Table 3. Tables 4 and 5 display the results for compressive strength and tensile strength, respectively.

QUALITY OF RESULTS Tables A-1, A-2, and A-3 in Appendix A show the comparison of actual and allowable ranges for each hardened state test. The allowable ranges were calculated via multiplying the mean result of each batch by a factor for maximum acceptable range from ASTM C670 that depends on the number of test results, as well as a coefficient of variation factor (COV) from each test’s individual test method criteria (13). Note that the test method for split tensile strength, ASTM C496, does not include a COV factor for four-inch by eight-inch cylinders, however it does recommend a factor for six-inch by twelve-inch cylinders (12). This recommended factor

TABLE 4. 28-DAY COMPRESSIVE STRENGTH RESULTS, PSI MIXTURE

Commercial 3500

Commercial ACI

CRED

CURING AGE (DAYS)

BATCH 1

BATCH 2

BATCH 3

BATCH 4

BATCH 5

BATCH 6

MEAN

RANGE

0

1960

1910

2100

2150

2300

2050

2078

390

3

2350

2400

2590

2590

2640

2480

2508

290

7

2670

2920

2790

2790

2780

2740

2782

250

14

3000

3000

3050

3040

2800

2940

2972

250

0

2720

2620

2750

2890

2890

2790

2777

270

3

3080

3060

3390

3220

3190

3150

3182

330

7

3470

3480

3720

3450

3530

3370

3503

350

14

3620

3560

3720

3590

3520

3610

3603

200

0

3280

3580

3650

3780

3740

3730

3627

500

3

3710

3830

4040

3920

3980

4140

3937

430

7

4100

4350

4380

4370

4300

4410

4318

310

14

4250

4340

4470

4550

4420

4710

4457

460

10  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

TABLE 5. 28-DAY SPLITTING TENSILE STRENGTH RESULTS, PSI MIXTURE

Commercial 3500

Commercial ACI

CRED

CURING AGE (DAYS)

BATCH 1

BATCH 2

BATCH 3

BATCH 4

BATCH 5

BATCH 6

MEAN

RANGE

0

235

220

235

215

255

215

229

40

3

290

290

260

290

295

270

283

35

7

320

320

280

305

310

280

303

40

14

290

315

300

305

325

335

312

45

0

300

280

310

305

305

300

300

30

3

350

300

350

345

340

345

338

50

7

315

335

340

360

345

335

338

45

14

370

385

345

370

370

340

363

45

0

340

345

355

325

360

315

340

45

3

345

375

345

325

415

355

360

90

7

415

375

365

385

380

335

376

80

14

400

400

400

415

390

390

399

25

was used in this quality analysis in order to provide a means of check on the ranges of the split tensile results.

The red shaded cells in Tables A-1, A-2, and A-3 in Appendix A represent instances when the range obtained exceeded the allowable range. Green shaded cells represent instances when the range obtained was lower than the upper limit set by the allowable range.

Four out of thirty-six cases across all mixtures and tests are seen to have an actual range greater than the allowable range.

Commercial 3500 and CRED with zero days of immersion curing experienced one batch having lower than normal compressive breaks. CRED with three and seven days of immersion curing experienced singular batches having higher than normal tensile strengths for their curing age. This is thought to be a symptom of sample size; however, the exact cause is unknown but considered not to be a problem.

ANALYSIS OF RESULTS A statistical analysis of the hardened property results for each mixture was conducted to determine which mix performed better with a certain duration of curing. A statistical t-test with the assumption of unequal variances was conducted in order to accomplish this. When the absolute value of the calculated t-statistic was found to be less than the critical t-value at the corresponding degree of freedom, the results corresponding to this specific comparison were deemed to be not statistically different

(NSD). When the absolute value of the calculated t-statistic was found to be greater than the critical t-value at the corresponding degree of freedom, the results corresponding to this specific comparison were deemed to be statistically significantly different (SSD). Once a comparison is deemed SSD, a closer look at the compared mean property values is required to declare which is superior or inferior.

The primary objective of this research involves comparing the results of different ages of curing within the same mixture as well as showing how different immersion curing periods affect the hardened property results. These comparisons are shown in Tables 9, 10, and 11. A secondary objective involves comparing results from the same curing age but between the three different mixes, which shows how each mixture compares to each other under the same limited curing conditions. These comparisons are shown in Tables 12, 13, and 14.

All mixtures in this study have been used in previous studies and were chosen for this experiment to represent a range of performance (from poorest to best performing: Commercial 3500, Commercial ACI, CRED). It is through research highlighted in the literature review that the hypothesis of samples being cured via immersion longer will perform better than samples that have not been cured via immersion for as long as that sample can be used. For Tables 9 through 12, green shaded cells represent an instance when the comparison is SSD and the result which has been immersion cured for the smaller period of time is inferior.

The percent difference in means of the comparison is shown in WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  11

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332:

Commercial/Residential Enhanced Durability Concrete: Phase III — The Effect of Limited Curing these tables as well. Orange shaded cells represent an instance when the comparison is NSD. For Tables 13 through 15, green shaded cells represent an instance when the lower-ranking mix is SSD and inferior to the higher-ranking mix at that level of curing age. The percent difference in means of the comparison is shown in these tables as well. Orange shaded cells represent an instance when the comparison is NSD.

DISCUSSION The effect of limiting the curing time a concrete can go through in early stages dampens its ability to promote strength and durability characteristics, as seen by the previous tables. Not allowing excess water to enter the concrete’s matrix after final set in order to increase both the rate and degree of hydration decreases the amount of strength gaining hydration product, calcium silica

TABLE 9. STATISTICAL COMPARISON OF SR RESULTS WITHIN EACH MIXTURE COMPARISON

COMMERCIAL 3500

COMMERCIAL ACI

CRED

NSD

0 Days vs. 3 Days

Inferior

-12.4%

NSD

0 Days vs. 7 Days

Inferior

-22.7%

NSD

Inferior

-5.3%

0 Days vs. 14 Days

Inferior

-28.0%

NSD

Inferior

-9.8%

3 Days vs. 7 Days

Inferior

-9.2%

NSD

Inferior

-6.7%

3 Days vs. 14 Days

Inferior

NSD

Inferior

-11.2%

NSD

Inferior

-4.2%

7 Days vs. 14 Days

-13.9% NSD

TABLE 10. STATISTICAL COMPARISON OF COMPRESSIVE STRENGTH RESULTS WITHIN EACH MIXTURE COMPARISON

COMMERCIAL 3500

COMMERCIAL ACI

CRED

0 Days vs. 3 Days

Inferior

-20.7%

Inferior

-14.6%

Inferior

-8.50%

0 Days vs. 7 Days

Inferior

-33.8%

Inferior

-26.2%

Inferior

-19.10%

0 Days vs. 14 Days

Inferior

-43.0%

Inferior

-29.8%

Inferior

-22.90%

3 Days vs. 7 Days

Inferior

-10.9%

Inferior

-10.1%

Inferior

-9.70%

3 Days vs. 14 Days

Inferior

-18.5%

Inferior

-13.3%

Inferior

-13.20%

7 Days vs. 14 Days

Inferior

-6.8%

NSD

NSD

TABLE 11. STATISTICAL COMPARISON OF TENSILE STRENGTH RESULTS WITHIN EACH MIXTURE COMPARISON

COMMERCIAL 3500

COMMERCIAL ACI

CRED

0 Days vs. 3 Days

Inferior

-23.3%

Inferior

-12.8%

0 Days vs. 7 Days

Inferior

-32.0%

Inferior

-12.8%

Inferior

-10.50%

0 Days vs. 14 Days

Inferior

-36.0%

Inferior

-21.1%

Inferior

-17.40%

3 Days vs. 7 Days 3 Days vs. 14 Days 7 Days vs. 14 Days

NSD Inferior

NSD

NSD -10.3%

NSD

12  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

NSD

Inferior

-7.4%

Inferior

-7.4%

Inferior

-10.90% NSD

—Continued on page 22

TABLE 12. STATISTICAL COMPARISON OF SR RESULTS WITHIN CURING AGES COMPARISON

0

3

7

14

NSD

NSD

Commercial 3500 vs.

Commercial ACI

Inferior

-22.7%

Inferior

-11.7%

Commercial 3500 vs. CRED

Inferior

-205.3%

Inferior

-168.1%

Inferior

-161.9%

Inferior

-161.7%

Commercial ACI vs. CRED

Inferior

-148.8%

Inferior

-140.0%

Inferior

-164.7%

Inferior

-155.7%

TABLE 13. STATISTICAL COMPARISON OF COMPRESSIVE STRENGTH RESULTSWITHIN CURING AGES COMPARISON

0

3

7

14

Commercial 3500 vs.

Commercial ACI

Inferior

-33.6%

Inferior

-26.8%

Inferior

-25.9%

Inferior

-21.3%

Commercial 3500 vs. CRED

Inferior

-74.5%

Inferior

-56.9%

Inferior

-55.2%

Inferior

-50.0%

Commercial ACI vs. CRED

Inferior

-30.6%

Inferior

-23.7%

Inferior

-23.3%

Inferior

-23.7%

TABLE 14. STATISTICAL COMPARISON OF TENSILE STRENGTH RESULTS WITHIN CURING AGES CURING AGE (DAYS)

COMPARISON

0

3

7

14

Commercial 3500 vs.

Commercial ACI

Inferior

-30.9%

Inferior

-19.8%

Inferior

-11.8%

Inferior

-16.6%

Commercial 3500 vs. CRED

Inferior

-48.4%

Inferior

-27.4%

Inferior

-24.2%

Inferior

-28.1%

Commercial ACI vs. CRED

Inferior

-13.3%

Inferior

-11.1%

Inferior

-9.9%

hydrate (CSH). With less CSH comes less strength bonds and more permeable pore space where these bonds would have taken place.

When examining the sole effect of curing time, as is done in Tables 9 through 11, it is seen that SR responded better to curing time in the commercial 3500 and CRED mixes than the commercial ACI. This could possibly be attributed to the mix design, as ACI has a higher amount of Portland cement than the other mixes, giving it much more opportunity to start making partial bonds through hydration and providing less permeable pore space. Commercial 3500 and CRED both responded well to SR in terms of immersion curing age, as 5 out of 6 cases in both mixtures proved the higher curing age to be beneficial.

The effect of providing more curing time had the greatest impact on compressive strength, as seen in Table 10. The commercial

NSD

3500 mixture’s results indicated that every instance of comparison shows more immersion curing time leads to an SSD and higher compressive strength than those with less immersion curing time.

Commercial ACI and CRED both experienced 5 out of 6 cases where more immersion curing time lead to an SSD and higher compressive strength as well.

Tensile strength performed well in both commercial 3500 and commercial ACI, with more curing time leading to SSD and higher tensile strengths in 4 and 5 out of 6 cases, respectfully. The CRED mixture seen split responses, with 3 out of 6 comparisons showing that an extended amount of immersion curing time caused SSD and higher tensile strengths than those with less immersion curing time.

The analysis shown in Tables 12 through 14 reaffirm the hierarchy of the mixtures shown in phase one of this research.

WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  13

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332:

Commercial/Residential Enhanced Durability Concrete: Phase III — The Effect of Limited Curing

Figures 1 and 2. Display how an increase in the amount of time a concrete is allowed to cure leads to higher strength and durability results. development. While the effects appear more prominent for compressive strength, tensile strength also has a similar strength development relationship.

CONCLUSIONS Using three mixtures that are meant to represent a broad spectrum of commercial and residential concrete and subjecting them to four different time periods of immersion curing, it can be concluded that: • Figure 2. Tensile Strength Results Compared to Days of Immersion Curing

Figure 1 (Left) displays the smaller amount of change seen in SR results when considering longer amounts of immersion curing time. This is due in part to the smaller value in number of SR when compared to larger numbers such as compressive or tensile strength. Figure 1 (Right) and Figure 2 provide a good visual on the effects that extended curing time has on strength 14  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

•

•

More immersion curing time can benefit both strength and durability properties.

If using the lower end of the commercial and residential concrete spectrum, which could be considered objectionable, simply curing for three days instead of not curing at all could lead to increase in compressive strength of up to 20%.

Using a concrete on the high end of the commercial and residential spectrum, such as CRED, increases the resistance to chloride ion permeability, thus increasing the durability of the concrete without regard to the amount of immersion curing time.

APPENDIX A TABLE A-1. COMPARISON OF ALL MIXTURE’S SR RANGES TO ALLOWABLE RANGES CURING AGE (DAYS)

COMMERCIAL 3500

COMMERCIAL ACI

CRED

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

0

1

3.3

1.7

4.1

0.9

10.1

3

1.1

3.7

1.4

4.1

1.3

9.9

7

0.7

4.1

1.5

4

1.5

10.6

14

0.7

4.2

1.8

4.3

1

11.1

TABLE A-2. COMPARISON OF ALL MIXTURE’S COMPRESSIVE STRENGTH RANGES TO ALLOWABLE RANGES CURING AGE (DAYS)

COMMERCIAL 3500

COMMERCIAL ACI

CRED

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

0

390

266

270

355

500

464

3

290

321

330

407

430

504

7

250

356

350

448

310

553

14

250

380

200

461

460

571

TABLE A-3. COMPARISON OF ALL MIXTURE’S TENSILE STRENGTH RANGES TO ALLOWABLE RANGES CURING AGE (DAYS)

COMMERCIAL 3500

COMMERCIAL ACI

CRED

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

Range (kilohm-cm)

Allowable Range (kilohm-cm)

0

40

45.8

30

60

45

68

3

35

56.5

50

67.7

90

72

7

40

60.5

45

67.7

80

75.2

14

45

62.3

45

72.7

25

79.8

REFERENCES 1. C. E. Proudley, “Curing Materials.” eds. R. Mielenz, D. Bloem, L. Gregg, L. Gregg, C. Kesler, and W. Price STP169AEB Significance of Tests and Properties of Concrete and Concrete-Making Materials. West Conshohocken, PA: ASTM

2.

International, 1966. 522-529. Web. 10 Aug 2021. <https:// doi.org/10.1520/STP49901S> ACI Committee 308. (2001). ACI 308R-01: Guide to Curing Concrete. Farmington Hill, MI: American Concrete Institute.

WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  15

by Robert Tyler Hughes, L. K. Crouch, Daniel Badoe, Kyle Wendt, Alan Sparkman and John Pearson

GOING BEYOND ACI 332:

Commercial/Residential Enhanced Durability Concrete: Phase III — The Effect of Limited Curing 3.

E. Senbetta, “Curing and Curing Materials.” eds. P. Klieger and J. Lamond STP169C-EB Significance of Tests and Properties of Concrete and Concrete-Making Materials. West Conshohocken, PA: ASTM International, 1994. 478-483.

Web. 10 Aug 2021. <https://doi.org/10.1520/STP36442S>.

4. Radlinski, Mateusz, and Jan Olek. “Effects of Curing Conditions on the Properties of Ternary (Ordinary Portland Cement/Fly Ash/Silica Fume) Concrete.” ACI Materials Journal, vol. 112, no. 1, 2015, pp. 49–58., doi:10.14359/51687307.

5. Goel, Ajay, Jyoti Narwal, Vivek Verma, Devender Sharma, and Bhupinder Singh. “A Comparative Study on the Effect of Curing on the Strength of Concrete.” International Journal of Engineering and Advanced Technology (IJEAT) 2 (2013): 401-406.

6. Senbetta, E. & Malchow, G. (1987). “Studies on Control of Durability of Concrete Through Proper Curing.” Symposium Paper, 100, 73-88. https://www.concrete.org/publications/int ernationalconcreteabstractsportal/m/details/id/3306 7. ACI Committee 332. (2014). ACI 332-14: Residential Code Requirements for Structural Concrete. Farmington Hill, MI: American Concrete Institute.

8. ACI Committee 332. (2020). ACI 332-14: Code Requirements for Residential Concrete. Farmington Hill, MI: American Concrete Institute.

9. ASTM Standard C192. (2018). “Standard practice for making and curing concrete test specimens in the laboratory.” ASTM International, West Conshohocken, PA, 2018. doi: https://doi. org/10.1520/C0192_C0192M-18 10. AASHTO T 358-17. “Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration.” American Association of State Highway and Transportation Officials. Provisional Standards, 2017 edition, April 2017.

11. ASTM Standard C39. (2018). “Standard test method for compressive strength of cylindrical concrete specimens.”

ASTM International, West Conshohocken, PA, 2018. doi: https://doi.org/10.1520/C0039_C0039M-18 12. ASTM Standard C496. (2017). “Standard test method for splitting tensile strength of 16  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

13. cylindrical concrete specimens.” ASTM International, West Conshohocken, PA, 2017. doi: https://doi.org/10.1520/ C0496_C0496M-17 14. ASTM Standard C670. (2015). “Standard practice for preparing precision and bias statements for test methods for construction materials.” ASTM International, West Conshohocken, PA, 2015. doi: https://doi.org/10.1520/ C0670-15 ACKNOWLEDGEMENTS The authors appreciate the financial and technical support provided by the Tennessee Concrete Association.

The authors would like to thank Denny Lind of BASF for extensive donations of chemical admixtures to the project. Also, the authors would like to thank Martin Medley for donations of materials used in this project.

In addition, the authors would like to thank Mark Davis for his patience and skill in fabrication, maintenance, and repair of the equipment.

Further, we appreciate the financial support of the TTU Department of Civil and Environmental Engineering.

Finally, the authors appreciate the administrative, financial and information technology support provided by the TTU Center for Energy Systems Research, particularly Dr. Satish Mahajan, Robert Craven, Barbara Fenlon, and Anysa Milum.

AUTHOR INFORMATION Robert Tyler Hughes, E.I.T. is a civil engineering master’s student at Tennessee Technological University.

L. K. Crouch, Ph.D., P.E. is a professor of Civil Engineering at Tennessee Technological University.

Daniel Badoe, Ph.D. is a professor of Civil Engineering at Tennessee Technological University.

Kyle Wendt is a future civil engineering master’s student and current civil engineering student at Tennessee Technological University.

Alan Sparkman, CAE, LEED AP, CCPf, is executive director of the Tennessee Concrete Association.

John Pearson, P.E. is the technical services director of the Tennessee Concrete Association.

T E C H N I C A L D I R E C T O R ’ S M E S S A G E — J O H N B . P E A R S O N , P. E .

THE RIGHT TOOL FOR THE JOB T

hose of you who know me know that I enjoy slow smoking meat on my homemade, offset, wood-fired smoker.

Controlling the temperatures across the cooker for a 14-hour cook can be a challenge, but it is a challenge that I have come to enjoy. Although I started out with just a single dial thermometer mounted in the chamber lid, I quickly came to realize that one thermometer would just not suffice. I now have probes made specifically for checking the temperatures at cooking grate level, probes to monitor the internal temperature of the meat, and infrared thermometers to check the surface temperatures on the tuning plates or on the outside of the smoke chamber or firebox.

If you are like my wife, you have probably already become bored with this topic. But there is a reason for my ramblings. Every one of these thermometers has a specific purpose. If you use the wrong tool, you will very likely get the wrong answer and you may end up making bad decisions based upon this information. Case in point, not too long ago I was over at a friend’s house, and he was cooking steak on his new outdoor griddle. He was quite proud of his griddle and especially proud of his new infrared surface thermometer which he believed somehow could magically provide a measure of the internal temperature of the steaks. I looked on in horror as I watched him check surface temperatures of the meat during the cook, knowing that he thought he was getting the internal temperature of the meat. For very thin pieces of meat, a surface thermometer might get you close, but should not be relied upon for food safety or quality. Fortunately, I like my steaks on the rare side, and no one ended up getting sick. I am just glad he was not cooking chicken.

I have seen the same type of issue come up in concrete testing.

I have had people insist that my reported concrete temperatures must be in error because my reading did not match what they were getting with their infrared surface thermometer. Infrared surface thermometers are great for their intended purpose and can provide some very quick information, but they cannot be used to determine the concrete temperature for acceptance.

For a representative concrete temperature, the probe must be protected from the influence of the ambient air. ASTM C1064 Temperature of Freshly Mixed Hydraulic Cement Concrete requires a thermometer long enough that the sensor can be submerged at least three inches into the concrete with at least

three inches of concrete cover in all directions. For concrete with larger aggregate, this distance increases to at least three times the nominal maximum size of the aggregate. This would mean for a 3-inch nominal max aggregate, nine inches of cover would be required in all directions. Surface thermometers, despite their speed and convenience, are not a reliable means to measure representative concrete temperatures for the purpose of acceptance testing.

These types of issues are not limited to temperature tests. The other fresh property tests for concrete have specific equipment requirements that are prescribed for a reason. Don’t get me wrong, sometimes I question the logic of certain requirements or restrictions included in the ASTM standards. I am not sure why it is acceptable to use the tamping rod, a float, or trowel to finish a concrete cylinder while a strike-off bar is not included in the list of acceptable tools for this purpose. By similar logic, one may question why a strike-off bar can be used for strike-off when determining air content by the pressure method, but a strikeoff plate is required for the density (unit weight) test. However, when you take the time to consider how the tests are performed, it becomes evident that strike-off is a much more critical process for the density test. Since density relies upon the relationship of weight to volume, an accurate density result relies on having the measure completely full (but not overfilled). A small error in strike-off will be magnified by a factor of four when the ¼ cubic foot air-pot base is used as the measure, thus skewing the results.

ASTM committees and subcommittees are continually reviewing and revising the specifications to improve the standards by removing overly restrictive requirements while also being clear and specific enough to ensure accuracy and repeatability.

We must resist the temptation to make modifications based upon our assumptions or presumptions. Occasionally, and under certain conditions, you may get lucky and your error may not have immediate negative consequences. However, just like undercooked food, your actions may come back to you or others with some rather unpleasant consequences.

—John Pearson WINTER 2022, Vol. 36, no. 3  Tennessee CONCRETE  17

CIM UPDATE

by Jon Huddleston, Associate Professor & CIM Director

O

fficials at Middle Tennessee State University cut the ribbon Thursday, October 13, to officially open the new $40.1 million School of Concrete and Construction Management Building on the west side of campus. The 54,000-square-foot facility will be an integrated and experiential learning laboratory for the 136 current Concrete Industry Management majors, and a major change from their approximately 9,000 square feet of space in the Voorhies Engineering Technology building.

MTSU ribbon cutting Dr. McPhee Speaking our commitment to maintaining the nation’s finest program in Concrete and Construction Management.”

McPhee said he was “amazed at the many ways concrete was utilized in the design and construction. Students will see firsthand how the many forms of concrete can add value and creativity to a structure. The building is a true living laboratory, with examples of various construction techniques and operating systems operating in full view of students.”

MTSU ribbon cutting Front of Building Among the building’s many features are a 200-seat lecture hall, four basic materials and building labs, a dedicated mechanical electrical plumbing, or MEP, classroom, a covered amphitheater, and two computer labs, including a virtual design and construction lab capable of advanced building models and construction simulations as well as an augmented virtual reality lab for immersive experiences.

University President Sidney A. McPhee calls it “the beginning of a new chapter in the success of our MTSU CIM (Concrete Industry Management) and CCM (Commercial Construction Management) programs. … With today’s dedication, we are publicly reaffirming

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18  Tennessee CONCRETE  WINTER 2022, Vol. 36, no. 3

Current Junior in CIM Aric Rickman speaks at ribbon cutting representing current students McPhee saluted industry partners who raised over $5 million in matching funding for the project and who “have been incredibly generous with their time and resources, enabling us to have an amazing facility for our students.”

The builder was Birmingham, Alabama-based Hoar Construction.

Orcut/Winslow was the architect. Construction began in January 2021 and finished in September.

The new facility marks an expansion of the university’s Corridor of Innovation in the heart of campus, anchored by the state-ofthe-art Science Building. In coming years, SCCM will have a new neighbor as the Applied Engineering Building will be built in that same area of campus.

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