2018 Spring NCC MeetingCoeur d’Alene, ID
April 24, 2018
Latex Modified Concrete: Missouri Perspective
Brett Trautman, P.E.Physical Laboratory Director
Construction and Materials Div.Missouri DOT
1) Purpose of Bridge Deck Overlays2) Types of Bridge Deck Overlays3) History in Missouri4) Pro’s and Con’s5) What is Latex Modified Concrete
(LMC)6) Key LMC Specifications7) Resistivity Testing
Outline
Keep deicing agents away from reinforcing steelSacrificial layer of low permeability concreteThickness ranges from 2 to 4 inches
Purpose of Deck Overlays
I I I
Deck Overlay
Bridge Deck (Structural Element)Epoxy
Rebar
1) LMC2) Low Slump Concrete3) Silica Fume Concrete4) High Early LMCCalcium Sulfoaluminate
(CSA) Cement Concrete Wearing Surface
Bridge Deck Overlay Types
Note: Experimental overlays (JSP)
Concrete Mixture- Cement Content = 818 – 827 lbs./cu. yd.- Amount of fine aggregate = 50% (absolute volume
of total aggregate)- Min. Air Content = 5.0%- Slump = ½ +/- ½ in. (max. 1 inch)Require Type A water reducerNo supplementary cementitious
materialsUtilize Type I or II cement
Low Slump Concrete
Determine in-place density- No less than 98% of the standard density- One in-place density per 100 sq. yds. - One standard density every two hours- Nuclear gauge correction factor (MoDOT TM 36)
Low Slump Concrete
Concrete Mixture- Cement Content = Min. 640 lbs./cu. yd.- Water/Cementitious Ratio = Max. 0.37- Silica Fume replacement = 6 – 8%- Amount of fine aggregate = 50 – 55% (absolute
volume of total aggregate)- Min. Air Content = 5.0%- Slump = 3 – 7 ½ inches
Utilize Type I cement
Silica Fume Concrete
Allow Type F or G HRWR to be usedNo supplementary cementitious materials
other than silica fumeEvaporation rate monitored- Precautions taken if over 0.1 lbs./sq.ft./hr.Evaporation retarders allowed- Used judiciously- Not used as a finishing aid
Silica Fume Concrete
Concrete Mixture- Cement Content = Min. 658 lbs./cu. yd.- Water/Cement Ratio = Max. 0.40- Latex Emulsion = 24.5 gal./cu. yd.- Amount of fine aggregate = 50 – 55%(absolute volume of total aggregate)
- Air Content = 0 – 6.5%- Slump = 3 – 6 inches
High Early LMC
No air entrainment admixture used Utilize Type HE high early strength cementNo supplementary cementitious materialsSet control allow- Cement manufacturer’s recommendationHarden Concrete Properties- Min. 28-day compressive strength = 4,500 psi- Max. 28-day rapid chloride permeability = 1,000
coulombs
High Early LMC
First project built in 2008Used on 25+ bridgesGood performance so far- Minimal de-bonding noted- Low severity cracking observed- 30+ yr. old bridge decks JSP based on experience
with Type Low P cement
CSA Cement Concrete Wearing Surface
2009
2016
Concrete Mixture- Cement Content = Min. 575 lbs./cu. yd.- Water/Cement Ratio = 0.42 – 0.45- Amount of fine aggregate = 50 – 55% (absolute
volume of total aggregate)- Air Content = 0 – 6.5%- Slump = 3 – 6 inches 7 to 10 minutes after
dischargeUtilize Type VRH cement (ASTM C1600)
CSA Cement Concrete Wearing Surface
No air entrainment admixture used No supplementary cementitious materialsCitric acid used for set controlHarden Concrete Properties- Min. 3-hour compressive strength = 3,000 psi- Min. 28-day compressive strength = 4,500 psi- Max. 28-day rapid chloride permeability = 1,000
coulombs
CSA Cement Concrete Wearing Surface
Started using bridge deck overlays in the early 1970’s
- LMC first used in 1973- Low Slump Concrete first used in 1977- Silica Fume Concrete first used in 1992- High Early Strength LMC first used in 2006Added LMC and Low Slump Concrete to
Standard Specification's in 1996Add Silica Fume Concrete in 1999Added High Early LMC in 2011
History in Missouri
Pro’s and Con’sLatex Modified Concrete
Low permeability Good performance
(20 to 25 yrs.) Resilient to bridge
movement during early ages
Sticky mix to finish Rough ride w/long
spans; slower set time Requires additional
subcontractor w/mobile mixer Latex is expensive
Pro’s Con’s
Pro’s and Con’sLow Slump Concrete
Pro’s Con’s
Low permeability Good performance
(15 to 20 yrs.)
Stiff mix to finish Difficult to consolidate Requires in-place
density testing Requires additional
subcontractor w/mobile mixer
Pro’s and Con’sSilica Fume Concrete
Prone to plastic shrinkage cracking Sticky mix to finish Extra effort to add
silica fume; in bags Bags don’t full
dissolve Silica fume not fully
dispersed
Pro’s Con’s
Very low permeability Decent performance
(10 to 15 yrs.) Does not require an
additional subcontractor w/mobile mixer
Pro’s and Con’sHigh Early LMC
Low permeability Good performance
(10 plus yrs.) Allows weekend
closures
Sticky mix to finish Requires additional
subcontractor w/mobile mixer Concrete mix is
expensive
Pro’s Con’s
Hydraulic cement and aggregates combined with latex emulsion during mixingPart of the mixing water
replaced with latex emulsionDesigned in late 1960’s by
Dow Chemical Co. Intended as a thin bonded
overlay
What is LMC
Suspension of styrene-butadiene polymer (Size: 0.2 micro) in waterTypical LMC formulation contains 15% latex
solids as a percent of cementPolymer fuses together when in close contact
to form a highly waterproof film
Latex Emulsion
Key LMC SpecificationUse a quality LMC mix
Use Type I or II cementNo supplementary cementitious materials
Properties MoDOT ACI 548.4
Air Content, % 0 to 6.5 3 to 7
Slump, inches Max. 9 4 to 6
% Fine Agg. (* by volume) (** by weight) 50 to 55* 55 to 70**
Min. Cement Content, lbs./cu. yd. 658 658
Latex Emulsion Admixture, gal./cu. yd. 24.5 ---
Max. Water/Cement Ratio 0.40 0.40
Utilize proper coarse aggregate- ¾ inch maximum top size unless plan thickness is
3 inch or greater- Very low deleterious content
Key LMC Specification
Material Percent by WeightDeleterious Rock 1.0Shale and Pyrite 0.2
Chert 0.5Other Foreign Material 0.1
Account for water in the latex emulsion admixture
- Admixture comprised of 47 to 54% water- This water impacts the w/cm ratio
Key LMC Specification
Use a quality latex emulsion- Comply with requirements in FHWA-RD-78-35
Key LMC Specification
Property MoDOT FHWAColor White White
Polymer Type Styrene-Butadiene Styrene-ButadienePercent Solids 46 - 53 46.0 – 53.0
pH 5.0 – 12.0 8.5 – 12.0Particle Size, Angstrons 1400 – 2500 1400 - 2500
Viscosity, centipoises +/- 20 +/- 20Percent Coagulum Max. 0.10 Max. 0.10
Freeze/Thaw Stability, % Max. 0.10 Max. 0.10Surface Tension, dynes/cm Max. 50.0 Max. 50.0
Percent Butadiene 30 - 40 30 - 40
Use a quality latex emulsion- Three products on MoDOT’s Pre-Acceptance List
Key LMC Specification
Surface preparation critical to achieving a satisfactory bond
- Remove all unsound concrete- Remove all dirt, oil, & other
foreign materialSand blasting followed by
air blasting- Hydro-demolition allowed
Key LMC Specification
Existing surface at SSD condition prior to LMC placement
- Surface wetted for a minimum 3 hours- Cover with polyethylene sheeting until placement- Remove standing water from depressions
Key LMC Specification
Protect the prepared surface from contamination during placement operations
- Cover surface with plastic sheeting
Key LMC Specification
Mobile mixer calibration critical to producing quality LMC
- Calibrate in the presence of the engineer
Key LMC Specification
Store latex emulsion correctly- Protect from exposure to
temperatures over 85 deg. F- Don’t store in direct sunlight- Protect from freezing
Key LMC Specification
Latex emulsion can separateMix latex emulsion prior to use- Mechanically agitate- Hand roll drums- Mechanical means in storage compartment
Key LMC Specification
Place overlay at the proper thicknessPoor performance if overlay placed to thin- Minimum 1 ¾ inches- From MoDOT Research Report entitled,
“MCHRP83-1 Performance of Latex Modified and Low Slump Concrete Overlays on Bridge Decks”
Key LMC Specification
Cure concrete properly- Wet cure for 48 hours
Key LMC Specification
Used to evaluate LMC used on two projects- Interstate 64, St. Louis County- Interstate 70, St. Louis CountyUtilized a Resipod
Resistivity Testing
Interstate 64 Interstate 70
Estimated the Rapid Chloride Permeability (RCP) using an equation developed from MoDOT research
- Research conducted by the University of Missouri –Kansas City
- Completed in early 2015
Resistivity Testing
Resistivity TestingUMKC Research (2015)
Test Age(days)
Surface Resistivity
(kohms-cm)
Est. RCP(coulombs)
Desired RCP
(coulombs)
14 27.9 1326
28 31.2 1185 1500
56 34.7 1065
91 38.9 950
Resistivity Testing Interstate 64, St. Louis County (2015)- Bridge over the Missouri River
Test Age(days)
Surface Resistivity
(kohms-cm)
Est. RCP(coulombs)
Desired RCP
(coulombs)
14 13.4 2767
28 16.7 2218 1500
56 19.3 1919
91 22.9 1616
Resistivity Testing Interstate 70, St. Louis County (2016)- Bridges over Interstate 170
