Innovative Admixtures for Effective Control of the Hydration and Workability of Fresh Concrete Charles Nmai, Ph.D., P.E., FACI BASF Corporation (Admixture Systems) Beachwood, OH 44122

Overview Code and Standard Specification Provisions for Discharge of Concrete ASTM C94/C94M ACI 318-14; ACI 301-10 Review of the Hydration of Portland Cement Set-Control Admixtures Conventional Retarding Admixtures Hydration-Controlling Admixtures Workability-Retaining Admixture Summary

Re-affirmed in 1938 with a note! Time-to-Discharge of Concrete The Background Info… Specification tentatively used in 1933 and in 1935 was adopted in ASTM C94. ASTM C94-35; Sec. on Delivery, Time of Hauling: Concrete shall be delivered to the site of the work, and discharge from the hauling container shall be completed within a period of 11⁄2 h after the introduction of the mixing water to the dry materials.. Re-affirmed in 1938 with a note!

The two- and three-hour limit was removed in subsequent years Time-to-Discharge of Concrete The Background Info… The Note… “under specially favorable conditions periods up to 2 and 3 hours may be allowed” for concrete to be delivered to the site and discharged since “research has shown no detrimental effects at the 1.5 hour time limit.” The two- and three-hour limit was removed in subsequent years

Time-to-Discharge of Concrete Current Wording… ASTM C94/C94M - 16; Sec. 12.10: Discharge of the concrete shall be completed within 11/2 h after the introduction of the mixing water to the cement and aggregates or the introduction of the cement to the aggregates. This limitation is not prohibited from being waived by the purchaser if the concrete is of such slump or slump flow after the 11⁄2-h time has been reached that it can be placed, without the addition of water, to the batch.

Time-to-Discharge of Concrete ACI 318-14; Sec. 26.5.2 – Concrete Placement and Consolidation 26.5.2.1 Compliance Requirements: (g) Concrete that has been contaminated or has lost its initial workability to the extent that it can no longer be consolidated by the intended methods shall not be used. (h) Retempering concrete in accordance with the limits of ASTM C94 shall be permitted unless otherwise restricted by the licensed design professional.

Time-to-Discharge of Concrete ACI 301-10; Sec. 4.3 – Execution: 4.3.2.2 Time of discharge — Unless otherwise permitted, time for completion of discharge shall comply with ASTM C94/C94M. When discharge is permitted after more than 90 minutes have elapsed since batching or after the drum has revolved 300 revolutions, verify that air content of air-entrained concrete, slump, and temperature of concrete are as specified.

Calcium silicate hydrate Strength & Durability Properties of Concrete ...develop due to a chemical reaction between cementitious materials and water. Cement + Water C-S-H + Ca(OH)2 + Other Calcium silicate hydrate Calcium hydroxide

Stage of Cement Hydration Source: FHWA HIF-07-004: Integrated Materials and Construction Practices for Concrete Pavement

Heat Evolution: Stage 2 Source: FHWA HIF-07-004: Integrated Materials and Construction Practices for Concrete Pavement

Concrete Characteristics during Cement Hydration Source: FHWA HIF-07-004: Integrated Materials and Construction Practices for Concrete Pavement

Time-of-Set of Concrete Source: FHWA HIF-07-004: Integrated Materials and Construction Practices for Concrete Pavement

Retarding Admixtures Benefits include… Long hauls PURPOSE: Retarding admixtures are added to concrete to offset acceleration and unwanted effects of elevated temperatures to keep concrete workable during placement and consolidation. Benefits include… Long hauls (hydration-controlling types)

Function primarily by retarding reaction of silicates in cement Retarding Admixtures Function primarily by retarding reaction of silicates in cement Can accelerate the aluminate reaction

Effect of Retarders on Hydration

Hydration-Controlling Retarding Admixture Types Conventional Organic Inorganic Hydration-Controlling (or Extended-Set Control)

Hydration-Controlling Admixtures Function primarily by retarding reaction of all cement minerals & gypsum

Hydration-Controlling Admixtures Cement paste studies by Kinney indicated that during the induction period the HCA prevented: the conversion of calcium silicate hydrate (CSH) to a secondary hydrate the layer of ettringite coating C3A from reacting with the pore solution

Effect of Retarders on Hydration

Hydration Controlling Benefits of Retarding Admixtures Hydration Controlling Stabilization of: Concrete Washwater Returned Plastic Concrete Freshly-Batched Concrete (long hauls / time-to-discharge)

Long-Haul Benefits Hydration-Controlling Admixtures Total Control over Setting Characteristics Better Slump Retention Temperature Control

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Project: Light House Foundation - US Army Corps of Engineers Contractor: Ryba Marine Construction Ready Mix Supplier: Ozinga Ready Mix, Chicago, IL Treated Volume: ~ 200 yd3 (150 m3) ESC Admixture Dosage: 4 fl oz/cwt (260 mL/cwt) Haul Time: 3 hours

Hydration-Controlling Admixtures As Batched At Jobsite Slump: 6 in. (150 mm) 6 in. (150 mm) Temperature: 70 oF (21 oC) 67 oF (19 oC)

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application U.S. Dept. of Energy Microwave Tower Footing; Monument Valley, Utah: Several 45 yd3 (34 m3) concrete placements Batched in Flagstaff, Arizona, 250 miles (400 km) away Haul Time of 8 hours! Excellent temperature control 66 to 63 oF (19 to 17 oC) Slump decreased from 6.5 to 4 in. (165 to 100 mm) H-C Admixture Dosage: 8 fl oz/cwt (520 mL/100 kg)

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application U.S. Dept. of Energy Microwave Tower Footing; Monument Valley, Utah:

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Project: Useppa Island (off coast of Ft. Myers, FL) Date: August 1990 Treated Volume: ~ 60 yd3 (46 m3) Compressive Strength: 3,000 psi (21 MPa) Slump: 6.0 in. (150 mm) w/ minimal retempering Initial time-of-set*: 8 to 10 h (* Barge Haul Time of 1.5 h + 3 to 5 h b/n trucks + Safety Margin) Other: Temperature control + Float finish

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Time of Set Evaluation: Cement 450 lb/yd3 Class F Fly Ash 200 lb/yd3 Type A Admixture 7.5 fl oz/cwt Air-Entraining Admixture 1.0 fl oz/cwt Slump 5.5 in. Air Content 4.5 % Ambient Temperature 87 oF Concrete Temperature 92 oF Initial Time-of-Set Plain Reference 3 h 45 min HCA @ 2 fl oz/cwt 5 h 10 min HCA @ 4 ” 6 h 35 min HCA @ 6 ” 8 h 35 min

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application HCA @ 4 fl oz/cwt Truck #1 Truck #2 Batch Time 6:15 a.m 6:30 a.m. Slump 6.75 in. 6.50 in. Ambient Temperature 78 oF Concrete Temperature 91 oF Initial Set (Untreated) 4 h 20 min 4 h 35 min Initial Set (Treated) 10 h 45 min 11 h 15 min Start of Pumping 11:00 a.m. Time from Batching approx. 4 h 30 min approx. 6.0 in. (no retempering) less than 91 oF

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Flurlinger Tunnel; Switzerland HCA @ 7 fl oz/cwt Cement 716 lb/yd3 w/c 0.45 HRWR 10 fl oz/cwt Shotcrete Accelerator 60 fl oz/cwt DIN Flow: Initial 23.50 in. After 4 h 22.75 in. After 9 h 22.00 in. 28-d Comp. Strength* 4,860 psi Wet Shotcrete Application Local environmental ordinance restricted site batch plant operation to hours b/n 7 a.m. & 10 p.m. HCA-treated concrete used for shotcreting after 10 p.m. * Specified compressive strength: 3,600 psi

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application NYC MTA 7 Line Project 8+ h of Slump Retention Needed Concrete temperatures ranged from 60 to 90 oF over the period of the project Varying dosages of HCA used Pumped up to 5600 ft S3II….. Shotcrete Skanska….. Tunnel Lining Railworks…. Tracks

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Eliminates need for portable batch plants Extends service area of ready-mixed plants Reduces or eliminates costs associated with use of ice and liquid nitrogen

Hydration-Controlling Admixtures Performance benefits have been validated by: U.S. Army Corps of Engineers under Construction Productivity Advancement Research (CPAR) program (Report No. CPAR-SL-95-2; December 1995) ICBO Evaluation Services, Inc. (Report No. 4817, October, 1990)

Hydration-Controlling Admixtures

Hydration-Controlling Admixtures Approved by: 42 State DOTs & AASHTO NTPEP NSF International Locally…. Port Authority of NY/NJ NYC DEP TBTA SCA MTA DOB

Long-Haul Application Hydration-Controlling Admixtures Long-Haul Application Section 510.3.4.2.1 of the New Mexico DOT’s portland cement concrete specifications provides guidelines for extended mixing time when concreting is required in rural and remote areas where the normal mixing time cannot be met. Appendix B of the Iowa DOT’s Materials I.M.403 provides guidelines for dosages of retarding and water-reducing and retarding admixtures for bridge deck and drilled shaft concrete when extended working time is required (link… http://www.iowadot.gov/erl/current/IM/content/403ab.pdf

Workability-Retaining Admixture (a “recent” innovation) Admixtures for Maintaining Consistency of Concrete Workability-Retaining Admixture (a “recent” innovation)

Workability-Retaining Admixture (W-R-A) A revolutionary admixture formulated to provide workability (slump) retention of concrete without affecting other properties. Introduced in 2009 Varying degrees of workability retention, depending on dosage, without retardation & without any impact on early- age strength development For moderate to high slump mixtures, including SCC. The workability-retaining admixture was introduced in 2009. it is neither a retarding admixture nor a hydration-controlling admixture. Also, it is not a slump-retaining high-range water reducer, therefore it has no impact on water reduction or initial slump. The workability-retaining admixture functions by providing what would be analogous to a “time-release” dispersion of cementitious materials that helps to maintain slump and workability. It can be dosed to provide varying degrees of workability retention of up to about 2 hours, depending on application. Because of its unique chemistry, it has no impact on the time of set of concrete and, consequently, no impact on early-age strength development.

W-R-A vs. Retarding Admixture

Workability-Retaining Admixture Laboratory Performance Data   Mix #1 Mix #2 Mix #3 Type I Cement, lb/yd3 (kg/m3) 750 (445) w/cm 0.37 PCE High-Range Water Reducer, fl oz/cwt (mL/100 kg) 8.5 (555) 7.5 (490) Viscosity-Modifying Admixture, fl oz/cwt (mL/100 kg) 5.0 (325) Workability-Retaining Admixture, fl oz/cwt (mL/100 kg) 3.0 (195) 6.0 (390) Slump Flow, in. (mm) Initial 26.25 (670) 24.5 (620) 24.75 (630) 30 minutes 26.0 (660) 27.0 (685) 28.5 (725) 55 minutes 18.0 (460) 28.0 (730) 80 minutes 10.5 (265) 21.0 (535) 27.5 (700) Air Content, % 1.6 1.7 1.9 Time of Setting, h Initial 3.6 3.8 4.1 Final 4.7 4.9 5.3 Compressive Strength, psi (MPa) 12 hours 2490 (17.2) 2480 (17.1) 1 day 4640 (32.0) 4790 (33.0) 5330 (36.7) 7 days 8160 (56.3) 8550 (59.0) 8460 (58.3) 28 days 9340 (64.4) 9650 (66.5) 10410 (71.8)

(photo courtesy of Dominion Resources, Inc.) Slip-Formed Cooling Tower; Brayton Point, Somerset, MA 15 MPa (2,200 psi) in 24 h 10 L/m3 (2 gal/yd3) of nitrite-based inhibitor 76,400 m3 (100,000 yd3) Targets: 200 mm (8 in.) slump 6 percent air content (photo courtesy of Dominion Resources, Inc.)

(photo courtesy of Dominion Resources, Inc.) Slip-Formed Cooling Tower; Brayton Point, Somerset, MA   Slump Air Content No. of Measurements 362 Average 210 mm (8.2 in.) 6.2 percent Std. Dev. 29 mm (1.14 in.) 0.9 percent (photo courtesy of Dominion Resources, Inc.)

Workability-Retaining Admixture (W-R-A) Performance Data*: 5,000 psi (34.5 MPa) Concrete Slump Air Content Target 6 – 8 in. (150 – 200 mm) 5 + 1.5 percent No. of Records 107 Average 7.4 in. (185 mm) 4.7 percent Std. Dev. 0.95 in. (24 mm) 1.04 percent * Water reclamation facility (Puma County)

Benefits of Workability-Retaining Admixture Minimizes slump adjustment (retempering) at the job site Promotes greater consistency of concrete workability, air content and compressive strength Enhanced in-place performance Fewer rejected loads Faster truck turn-around time The primary benefit of the workability-retaining admixture is to eliminate either retempering or re-dosing of high-range water-reducing admixture at the jobsite in order to provide greater consistency of concrete workability, air content and compressive strength. Retempering of air-entrained concrete, in particular, can lead to undesired increases in air content that could result in rejection of a load. The ability to hold slump and workability over the duration of the placement therefore helps to promote consistency in air content.

World Trade Center Project, NY …Some Basic Facts Project Specifications and Other Details: 4 High Rise Buildings WTC 9/11 Memorial 1 Transportation Hub Up to 74% SCM Replacement using fly ash, slag cement & silica fume 14,000 psi @ 28 days 2,000 psi overdesign Modulus of Elasticity > 7.0 x 106 psi Nearly 1,000,000 yd3 to be used Required SCC spread of 27 in. Specifier – Port Authority of New York and New Jersey

World Trade Center Project, NY …Ex. HPGC Mixtures for Tower 1 14-ksi Mix 10-ksi Mix 8-ksi Mix* Cement, lb/yd3 300 288 Fly Ash, lb/yd3 70 160 100 Slag Cement, lb/yd3 485 495 450 Silica Fume, lb/yd3 35 -- SCM Content, percent 68 65 s/a 0.41 0.43 0.47 w/cm 0.24 0.26 0.40 PCE HRWR, fl oz/yd3 132 105 50 – 60 HCA, fl oz/yd3 48 50 50 – 70 Defoamer, fl oz/yd3 16 Work. Retainer, fl oz/yd3 As needed Slump Flow Spread, in. 27.0 28.5 25 – 30 * Winter version of mix.

So, To Summarize,…

Time-to-Discharge of Concrete Current Wording… ASTM C94/C94M - 16; Sec. 12.10: Discharge of the concrete shall be completed within 11/2 h after the introduction of the mixing water to the cement and aggregates or the introduction of the cement to the aggregates. This limitation is not prohibited from being waived by the purchaser if the concrete is of such slump or slump flow after the 11⁄2-h time has been reached that it can be placed, without the addition of water, to the batch.

Time-to-Discharge of Concrete ACI 318-14; Sec. 26.5.2 – Concrete Placement and Consolidation 26.5.2.1 Compliance Requirements: (g) Concrete that has been contaminated or has lost its initial workability to the extent that it can no longer be consolidated by the intended methods shall not be used. (h) Retempering concrete in accordance with the limits of ASTM C94 shall be permitted unless otherwise restricted by the licensed design professional.

Time-to-Discharge of Concrete ACI 301-10; Sec. 4.3 – Execution: 4.3.2.2 Time of discharge — Unless otherwise permitted, time for completion of discharge shall comply with ASTM C94/C94M. When discharge is permitted after more than 90 minutes have elapsed since batching or after the drum has revolved 300 revolutions, verify that air content of air-entrained concrete, slump, and temperature of concrete are as specified.

Whether over water or land! In Conclusion, Currently, innovative admixture technologies exist to permit waiver of the 90 minute, 300 rev limitation! Whether over water or land!

The End… Thank You!