Internal Curing of Pervious Concrete using Lightweight Aggregate
1. Internal Curing of Pervious
Concrete using Lightweight
Aggregate
John Kevern and Daron Brown
Pervious in Paradise 2014
2. The Good Stuff About Pervious
• Reduces stormwater volume
• Cleans stormwater
• Reduces the urban heat island
• Quiet
• Slip resistant
3. The Bad Stuff About Pervious
• The mix is different
• Not as many/improperly used standards
• Has to be cured under plastic
• It clogs
• It ravels
11/2/2015:3
4. Motivation
• Internal curing using a
super absorbent polymer
has shown beneficial to
pervious concrete
properties
• Internal curing is
commonly performed
using prewetted
lightweight fine
aggregate in
conventional concrete
5. Water to Cement Ratio
Cement
Hydration Products
Interlayer gel water
water
Chemical Shrinkage
Excess WaterExcess Cement
6. Internal Curing for Concrete
• Concrete needs water for hydration
• At w/c 0.42 and below self-desiccation
(autogenous shrinkage) causes significant
internal stresses
• Supplying external water to low w/c mixes only
impacts the surface
7. Internal Curing for Concrete
• Supplying additional water internally can
mitigate shrinkage stresses in low w/c
mixtures
• Saturated lightweight aggregates, saturated
porous aggregates, super absorbent polymers
can supply this extra internal water
8. Study Scope
• Determine if prewetted lightweight
aggregates can provide internal curing to
pervious concrete
9. Study Mixtures
• Control mixture had 7% fine aggregate by volume
• 100% of the conventional fine aggregate volume was replaced
with lightweight fine aggregate
• Admixtures were air, HRWR, and hydration stabilizer
*All samples individually placed to control
voids at 25%
Cement Coarse Aggregate Fine Aggregate Water
(pcy) SSD (pcy) SSD (pcy) (pcy)
PC(Control) 573 2214 164 195
PC- BDX (BuildexFines) 573 2214 126 (WSD) 195
PC- HPB(Hydraulic Press Brick Fines) 573 2214 145 (WSD) 195
PC- BRF (Big River Fines) 573 2214 98 (WSD) 195
PC- LW (AllHydraulic Press Brick) 573 1127 (WSD) 145 (WSD) 195
Mixture
Abs %
16%
19%
39%
11%
10. Tests
• Unit weight (ASTM C1688 and ASTM
C1754) and voids (ASTM C1754)
• Moisture loss
• Strength
• Permeability and infiltration
• Freeze thaw durability
• Shrinkage
• Degree of Hydration
11. Moisture Loss (ASTM C156)
• 9” x 13” x 2” samples
• Moisture loss over 72 hrs at 100°F and 32%
relative humidity
21. • Mixture containing prewetted fine lightweight
aggregate had better workability than the control
as indicated by greater fresh density.
• Moisture loss from mixtures containing prewetted
fine lightweight aggregate was similar to the
control samples.
• All lightweight aggregate tested produced
significant increases in the degree of hydration
over the control mixture. Performance was similar
between the aggregate types at 28 and 90 days.
Summary and Conclusions
22. • Samples containing fine prewetted lightweight
aggregate as a replacement for conventional sand
had similar compressive strengths to the control
mixture at 7 days. At 28 days the fine aggregate
samples all were stronger than the control.
• Prewetted lightweight aggregate improved freeze-
thaw durability. Performance was directly related
to the amount of additional pore space provided
within the lightweight particles.
• All samples containing lightweight aggregate had
significantly less shrinkage than the control
mixture in ring shrinkage testing.
Summary and Conclusions
23. Contact Information
John T. Kevern, PhD, PE, LEED AP
Associate Professor of Civil Engineering
370A Flarsheim Hall, 5110 Rockhill Rd.
University of Missouri – Kansas City
Kansas City, MO 64110
Phone: 816-235-5977
Fax: 816-235-1260
Email: kevernj@umkc.edu