1. 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

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

3. 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!

4. 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

5. Time-to-Discharge of Concrete Current Wording…
ASTM C94/C94M - 16; Sec :
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.

6. Time-to-Discharge of Concrete
ACI ; Sec
– Concrete Placement and Consolidation
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.

7. Time-to-Discharge of Concrete
ACI ; Sec. 4.3 – Execution:
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.

8. 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

9. Stage of Cement Hydration
Source: FHWA HIF : Integrated Materials and Construction Practices for Concrete Pavement

10. Heat Evolution: Stage 2
Source: FHWA HIF : Integrated Materials and Construction Practices for Concrete Pavement

11. Concrete Characteristics during Cement Hydration
Source: FHWA HIF : Integrated Materials and Construction Practices for Concrete Pavement

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

13. 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)

14. 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

15. Effect of Retarders on Hydration

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

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

19. 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

20. Effect of Retarders on Hydration

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

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

23. 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

24. 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)

25. 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)

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

27. 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 to 5 h b/n trucks + Safety Margin)
Other: Temperature control + Float finish

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

29. Long-Haul Application
Hydration-Controlling Admixtures
Long-Haul Application
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

30. Long-Haul Application
Hydration-Controlling Admixtures
Long-Haul Application
Flurlinger Tunnel; Switzerland
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

31. 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

32. 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

33. 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)

34. Hydration-Controlling Admixtures

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

36. Long-Haul Application
Hydration-Controlling Admixtures
Long-Haul Application
Section 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…

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

38. 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 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.

39. W-R-A vs. Retarding Admixture

40. 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) 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)

41. (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.)

42. (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.)

43. 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)
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)

44. 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.

45. 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, 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

46. 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.

47. So,
To Summarize,…

48. Time-to-Discharge of Concrete Current Wording…
ASTM C94/C94M - 16; Sec :
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.

49. Time-to-Discharge of Concrete
ACI ; Sec
– Concrete Placement and Consolidation
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.

50. Time-to-Discharge of Concrete
ACI ; Sec. 4.3 – Execution:
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.

51. 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!

52. The End…
Thank You!