Protecting Concrete From Freezing-And-Thawing Damage With Mineral-Blended Polymeric Microspheres

1. PROTECTING CONCRETE FROM
FREEZING-AND-THAWING DAMAGE
WITH MINERAL-BLENDED
POLYMERIC MICROSPHERES
Emmanuel K. Attiogbe, Ph.D., FACI
eattiogbe@ceminnovations.com

2. ■ Air entrainment with surfactants is an effective means of achieving a freeze-thaw damage resistant
concrete; however, controlling the amount of air in concrete is one of the most difficult and
frustrating aspects of concrete production.
■ Variability in air content of concrete due to variations in concrete materials, mixing, transportation,
ambient temperature, placement method, and testing leads to the following problems:
 Lower production rate of concrete
 More rejected loads
 Difficulty in achieving specified strength
 Difficulty in consistently obtaining target air-void systems
 Increased need for quality control at the project site
 Removal and replacement of hardened concrete that is determined to be non-compliant after
placement
■ Significant costs are associated with the problems listed above:
 These problems and costs suggest the need for alternative technologies to air entrainment.
2
Why Consider Use of Particles or Microspheres? (1)

3. ■ Expanded polymeric microspheres (in powder, paste or slurry form) have been found
to protect concrete from freeze-thaw damage since the 1970’s.
■ Polymeric microspheres, and other suitable particle types, would be insensitive to the
factors that impact air entrainment with surfactants, resulting in a more robust and
reliable alternative technology.
■ Hollow-core polymeric microspheres are dimensionally stable:
 Gas-filled wet-expanded microspheres in a wet foam or slurry form
 Gas-filled dry-expanded microspheres in a dry powder form
3
Why Consider Use of Particles or Microspheres? (2)

4. 4
Polymeric Microspheres
■ Expanded polymeric microspheres have very low densities and are difficult to handle in
dry powder form as the powder causes dusting.
■ The microsphere particles tend to adhere to each other or agglomerate, which may
cause poor dispersion and poor distribution in concrete.
■ A report published in 1981 has shown that microsphere agglomeration results in larger
quantities of microsphere to be required for freeze-thaw protection.
■ It would be preferred to use wet-expanded microspheres in slurry form in concrete to
avoid the problem of dusting.
■ The slurry is best produced at the point of use to minimize separation of the very low-
density microspheres from the liquid medium during storage:
 Leads to high production and logistics costs (stumbling blocks to introduction of the microsphere
technology into practice).
 A suitable method of delivery of polymeric microsphere powder into concrete, that
eliminates or minimizes particle agglomeration and dusting of the powder, would
facilitate introduction of the microsphere technology into practice.

5. ■ Compliance Concept: Suitable particle types would have higher coefficients of thermal
expansion (or contraction) than the concrete matrix and therefore would create annulus
voids which provide spaces for ice crystals to form:
■ Void-Particle Duality: An entrained air void is assumed to act as a particle with a
hypothetical annulus void whose size is determined based on the coefficient of thermal
expansion (or contraction) of air.
■ A particle type is equivalent to air voids if the particle type has the same diameter as the air
voids and the same compliance as the hypothetical compliance of the air voids.
■ The minimum diameter at which particles of a selected type are equivalent to air voids is
established as the effective diameter De.
■ A minimum annulus void size is established to achieve a freeze-thaw durable concrete at a
minimum volume fraction of the particles.
5
Overview of Particle Analysis for Freeze-Thaw Behavior (1)
Annulus
Void
How are microspheres, or particles in general, able to protect concrete?

6. ■ Equations are developed as a function of particle size (Dp), paste content of
the concrete (p) and the maximum spacing (𝑠𝑙𝑖𝑚𝑖𝑡) to calculate the minimum
volume fraction of particles or air voids (Amin) needed to achieve a freeze-
thaw durable concrete:
 When the annulus void sizes for the particles are equal to or larger than the
minimum annulus void size:
𝐴𝑚𝑖𝑛 =
𝑝𝐷𝑒
8𝑠𝑙𝑖𝑚𝑖𝑡 − 𝐷𝑒
𝑤ℎ𝑒𝑟𝑒 𝐷𝑝 ≤ 𝐷𝑒 𝐴𝑚𝑖𝑛 =
𝑝𝐷𝑝
8𝑠𝑙𝑖𝑚𝑖𝑡 − 𝐷𝑝
𝑤ℎ𝑒𝑟𝑒 𝐷𝑝 > 𝐷𝑒
(𝑠𝑙𝑖𝑚𝑖𝑡 is the maximum spacing of particles or air voids to achieve a freeze-thaw durable
concrete; 𝑠𝑙𝑖𝑚𝑖𝑡 has values of 190, 270, and 400 µm for w/cm values ≥ 0.45, between 0.35
and 0.45, and between 0.25 and 0.35, respectively.)
6
Overview of Particle Analysis for Freeze-Thaw Behavior (2)
How are microspheres, or particles in general, able to protect concrete?

7. 7
Overview of Particle Analysis for Freeze-Thaw Behavior (3)
Effective compliance ratio and minimum volume fraction of entrained air voids vs. air-void diameter:
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0
50
100
150
200
250
300
10 100
Min.
Volume
Fraction,
A
min
(%)
Effective
Compliance
Ratio,
C
ef
Air-Void Diameter or Effective Diameter, De (µm)
Effect. Compliance Ratio
Min. Volume Fraction
p = 0.30
w/cm ≥ 0.45
 The larger the diameter, the less compliant the air void
and the higher the minimum volume fraction of air
needed to achieve a freezing-and-thawing durable
concrete.

8. 8
Overview of Particle Analysis for Freeze-Thaw Behavior (4)
0
1
2
3
4
5
6
1.0 10.0 100.0 1,000.0
Min.
Volume
Fraction,
A
min
(%)
Microsphere or Air-Void Diameter, Dp (µm)
De = 52 µm (Microspheres)
Entrained
Air Voids
Polymeric
Microspheres
Polymeric
Microspheres
Minimum volume fraction of polymeric microspheres and entrained air voids vs. diameter:
p = 0.30
w/cm ≥ 0.45
 In general, microspheres with a diameter either smaller
than or larger than the effective diameter (De) for the
microsphere type, would require to be used at a higher
minimum volume fraction to achieve a freezing-and-
thawing durable concrete.

9. 9
Agglomeration of Microspheres
■ Expanded microspheres have very low densities and can agglomerate
in dry powder form, as well as in a slurry:
 The average size (Dp) of the agglomerated microspheres will be larger
than the size of the individual microspheres. Hence, the minimum
volume fraction (Amin), per the equation below, to achieve a freeze-thaw
durable concrete would be higher with agglomerated microspheres:
 𝐴𝑚𝑖𝑛 =
𝑝𝐷𝑝
8𝑠𝑙𝑖𝑚𝑖𝑡−𝐷𝑝
the cost to treat a unit volume of the concrete would be higher compared to
the cost associated with non-agglomerated microspheres.

10. 10
Blend of Microspheres and Mineral Powder to
Minimize/Eliminate Particle Agglomeration
■ Photomicrographs of powder blend showing spherical microspheres and mineral powder:
Microsphere-powder
blend
Powder blend under reflected light showing microspheres
with mineral powder adhering to them
Method of Delivery of Microspheres -
Powder blend in cross-polarized light showing
microspheres with mineral powder adhering to them

11. 11
Mix ID
A1 B1 C1 C2
Cement (kg/m3
) 335 335 335 335
Coarse Agg. (kg/m3
) 1104 1042 1104 1104
Fine Agg. (kg/m3
) 739 695 682 668
Water (kg/m3
) 174 174 174 174
w/c 0.52 0.52 0.52 0.52
AEA (mL/m3
) -- 96.2 -- --
Microspheres
(vol. % of concrete)
-- -- 1.0 1.25
Water Reducer,
(Type F) (mL/m3
)
923 -- 1235 1104
Slump (mm) 156 138 138 138
Air (vol. % of
concrete)
2.3 5.8 2.7 2.2
Unit Weight (kg/m3
) 2336 2248 2314 2307
28-day Compressive
Strength (MPa)
37.3 33.9 36.6 35.4
Freeze-Thaw Durability Testing – Concrete Mixture Design
Laboratory Drum Mixer

12. 12
Freeze-Thaw Durability Testing – ASTM C666/C666M
Testing for Slump and Air Content Compressive Strength and Freeze-Thaw Test Specimens

13. 13
Freeze-Thaw Durability and Scaling Resistance
Mix ID
A2 B2 C3
Cement (kg/m3
) 400 400 400
Coarse Agg. (kg/m3
) 1068 1009 1068
Fine Agg. (kg/m3
) 736 692 681
Water (kg/m3
) 168 168 168
w/c 0.42 0.42 0.42
AEA (mL/m3
) -- 230.8 --
Microspheres
(vol. % of concrete)
-- -- 1.0
Water Reducer,
(Type F) (mL/m3
)
2762 962 2623
Slump (mm) 114 133 108
Air
(vol. % of concrete)
2.1 5.9 2.6
Unit Weight (kg/m3
) 2375 2277 2320
28-day Compressive
Strength (MPa)
51.4 41.8 45.7
Freeze-Thaw Testing
Durability Factor (%)
(must be ≥ 60% @ 300
cycles)
Fail 90 84
Relative Dur. Factor (%)
(must be ≥ 80% @ 300
cycles)
-- 100 93
Scaling Rating @ 50
cycles
5 1 1
Scaling Mass Loss @ 50
cycles (g/m2
)
901 123 65
ASTM C672/C672M Test Specimens
Note: Microsphere-powder blend was dispensed into the
concrete mixture in a sack that completely disintegrated
during concrete mixing and released the microsphere powder.

14. 14
Freeze-Thaw Durability – ASTM C666/C666M
Powder blend with well-dispersed microspheres:
A minimum volume fraction of 1.0% needed for the concrete to be durable
0
20
40
60
80
100
0 50 100 150 200 250 300 350
Relative
Dynamic
Modulus
(%)
Number of Cycles
Non-Air Entrained
Air Entrained @ 5.8%
Microspheres @ 1.0%
Microspheres @ 1.25%
w/c = 0.52
Air-Entrained Concrete Microsphere Concrete
@ 300 cycles of freezing and thawing
 Surface-scaling levels are comparable after 300 cycles
of rapid freezing-and-thawing in water.

15. 15
Freeze-Thaw Durability and Scaling Resistance
Non-Air-Entrained
Concrete
Air-Entrained
Concrete
Microsphere
Concrete
0
200
400
600
800
1000
Mass
Loss
(g/m
2
)
0
20
40
60
80
100
0 50 100 150 200 250 300 350
Relative
Dynamic
Modulus
(%)
Number of Cycles
Non-Air Entrained
Air Entrained @ 5.9%
Microspheres @ 1.0%
ASTM C666 Test
ASTM C672 Test
@ 50 cycles of freezing and thawing
w/c = 0.42

16. 16
Mineral-Blended Polymeric Microspheres
Dosage
 Delivering the precoated microsphere powder in a sack that
disintegrates during concrete mixing facilitates adding the
right quantity of the microspheres by simply counting the
number of sacks:
 Quality control prior to concrete placement:
• Modified ASTM C173 for verification of microsphere content
o no use of isopropyl alcohol
Microspheres
Layer

17. 17
Photomicrograph of Microspheres in Hardened Concrete
@ 200x magnification
Air void
Microsphere
 Pre-qualification or post-placement assessment of microsphere concrete:
• Modified ASTM C457 for quantifying microsphere content of hardened concrete
o higher magnification than typically used

18. ■ Insensitive to the factors that render air entrainment with surfactants problematic,
resulting in a more robust and reliable alternative technology.
■ Enable the large-scale use of fly ash with high unburned carbon content as a
supplementary cementitious material.
■ Eliminate the production and placement issues related to pumped air-entrained
concrete.
■ Enable concretes with a stiff consistency that are difficult to air entrain, such as
pervious concrete and roller-compacted concrete, to be freeze-thaw durable.
■ Allow for dense, polished, machine-troweled surfaces to be specified for concrete
slabs in freeze-thaw environments.
18
Potential Benefits of Using Polymeric Microspheres

19. 19
Concluding Remarks
■ Precoating polymeric microspheres by blending dry-expanded microspheres with a
mineral powder minimizes agglomeration of the microspheres and promotes uniform
dispersion and distribution in a concrete mixture.
■ To facilitate handling, the microsphere-powder blend can be dispensed into a
concrete mixture in a sack that disintegrates during mixing and releases the powder.
■ Delivering the microspheres into a concrete mixture in a sack facilitates adding the
right quantity by simply counting the number of sacks; in addition, performing the
modified ASTM C173/C173M test without isopropyl alcohol would verify that the
microspheres are present in the right quantity.
■ Cyclic freeze-thaw and deicing salt scaling testing show that the microsphere-
powder blend at a microsphere content of 1.0% by volume of the concrete is as
effective as air entrainment in protecting concrete from freeze-thaw damage, but it is
not saddled with the uncertainties associated with air entrainment.

20. 20
List of References
 Poppe de Rook, “Process for Preparing Frost Resistant Concrete,” US Patent No. 4,057,526, Nov. 1977.
 Ozyildirim, Celik H. and Sprinkel, Michael M., “Investigation of Concrete Mixtures Incorporating Hollow
Plastic Microspheres,” Virginia Highway & Transportation Research Council and U.S. Department of
Transportation Federal Highway Administration, Report VHTRC 82-R7, Charlottesville, Virginia, July
1981, 38 pp.
 Bury, Mark A.; Ong, Frank; Attiogbe, Emmanuel; Nmai, Charles; and Smith, James, "Microsphere-Based
Admixture for Durable Concrete: A replacement for conventional air-entrainment," ACI Concrete
International, V. 36, No. 3, March 2014, pp. 59-63.
 Ong, Frank Shaode; Attiogbe, Emmanuel K.; Nmai, Charles K.; and Smith, James Curtis, "Freezing and
Thawing Behavior of Cementitious Systems with New Polymeric Microsphere-Based Admixture," ACI
Materials Journal, V. 112, No. 6, Nov.-Dec. 2015, pp. 735-743.
 Moffat, Edward G. and Thomas, Michael D. A., “Polymeric Microspheres Provide Resistance to Harsh
Winter Conditions,” Concrete International, V. 41, No. 1, Jan. 2019, pp. 36-41.
 Attiogbe, Emmanuel K., “Method of Delivery of Dry Polymeric Microsphere Powders for Protecting
Concrete from Freeze-Thaw Damage,” US Patent No. 10,730,794 B1, Aug. 2020.
 Attiogbe, Emmanuel K., “Compliance Concept in Protection of Concrete from Freeze-Thaw Damage,”
accepted for publication by ACI Materials Journal, V. 117, No. 6, Nov.-Dec. 2020, pp.187-200.
 Attiogbe, Emmanuel K., “A New Way to Deliver Protection from Freezing-and-Thawing Damage,”
Concrete International, V. 43, No. 1, Jan. 2021, pp. 27-33.

21. Email: eattiogbe@ceminnovations.com