Post on 07-Jul-2020
Presented By:James A. Davies, P.Eng.
Advanced Construction Techniques Ltd.3935 Lloydtown Aurora Road
Kettleby, OntarioL0G 1J0
Toll Free Telephone: 877-373-7248Email: jdavies@agtgroup.com
State of the Art in Grout Mixes
BALANCED STABLE GROUTS
• Definitions• Theory• Materials• Testing
Definition
Balanced Stable Cement Grout
A homogenous balanced blend of water and cementcombined with selected additives and admixtures
producing a product with zero bleed, low cohesion andgood resistance to pressure filtration.
Balanced Stable Grout
GroutMixture
Balanced Stable Grout
Optimal Blendof physical &rheological
properties forapplication
Zero BleedHomogeneous
WaterCementAdditives
Admixtures
Unstable Grout Mixtures
• Variable Rheology• Poor Particle Orientation• High Segregation & Sedimentation• High Pressure Filtration Coefficient• Unpredictable Behavior• Unstable During Injection• Marginal Durability• High Bleed Potential
Theory
• Low cohesion• Viscosity consistent with acceptable
penetration rate• Minimal to zero bleed• Constant rheology during application• Dispersed particles• High durability
What are the desired properties of a cementbased suspension grout?
Grouting Theory - Neat Cement Grouts
P
P
Refusal penetration controlled by pressure,cohesion, changing rheology clumping,and bridging
Substantial water loss throughpressure filtration
Densificationof Grout
Post-grout Bleed Channels
Neat Cement Grouts
Bleed
Grouting Theory - Balanced, Stable Grouts
P
Refusal penetration controlledby pressure and cohesion
Minimal water loss throughpressure filtration
Minor Densificationof Grout
Zero or Negligible BleedChannels
P
Balanced Stable Grouts
Bleed
Grout Injection Theory
Stabilized vs. Neat Grouts
Neat Grouts
Grout Injection Theory
Stabilized vs. Neat Grouts
Neat Grouts
Clumping and Bridging
Start of Refusal Pressure Builds
Limited Penetration DueTo High Cohesion
Grout Injection Theory
Stabilized vs. Neat Grouts
Neat Grouts
Densification of Grout
Pressure Filtration
Substantial Water Loss
Refusal Controlled by Pressureand Cohesion
Grout Injection Theory
Stabilized vs. Neat Grouts
Neat Grouts
Post Grout Bleed Channels
Grout Injection Theory
Stabilized vs. Neat Grouts
Neat GroutsMORE HOLES
Grout Injection Theory
Stabilized vs. Neat Grouts
Stabilized Grouts
Grout Injection Theory
Stabilized vs. Neat Grouts
Stabilized GroutsMinor Densificationof Grout
Minimal Water Loss ThroughPressure Filtration
Refusal Controlled by Pressureand Cohesion
Greater Penetration DueTo Lower Cohesion
Grout Injection Theory
Stabilized vs. Neat Grouts
Stabilized Grouts
Minimal Bleed Channels
Grout placement isextremely effective resultingin a more durable treatment
Characteristics of Balanced StableCement-Based Suspension Grouts
• Cement + water + additives +admixtures
• Minimal to zero bleed• High resistance to pressure filtration• Organized particles due to electrostatic
and chemical interaction• High durability
Characteristics of UnstableWater Cement Grouts
• Cement + water• Considerable bleed potential• Low resistance to pressure filtration• Unorganized particles• Lower durability
Advantages of Balanced Stable Grouts• Dispersed structure, stable rheology and lower cohesion result in increased
penetrability and greater radius of grout spread
• Minimal to zero bleed – The fractures that are filled remain 100% filled
• Increased penetration and minimal to zero bleed result in lower residualpermeability
• Lower residual curtain and grout matrix permeability result in increaseddurability
Materials
• Bentonite• Silica Fume• Flyash (Type C or F)• Welan Gum• Dispersant (Super Plasticizer)
Common Additives to Balanced Stable Grout
Bentonite• Product
Natural sodiummontmorillonite clayproduct.Typical dosage is 2-8 % byweight of cement.Should be pre-hydratedand added as a slurry.
• Characteristics
AdvantagesReduced pressure filtrationReduced final bleedEnhanced stability
DisadvantagesIncreased cohesionIncreased viscosity
Silica Fume• Product
By-product of the productionsilicon.Very fine sphericalparticulate.Typical dosage between 4-8% by weight of cement.
• Characteristics
AdvantagesIncreased penetrabilityReduced final permeabilityEnhanced durabilityWater repellantReduces pressure filtration
DisadvantagesIncreased Strength
Welan Gum• Product
High molecular weightbipolymer.Used to increaseresistance to pressurefiltration and for artesianconditions.Typical dosage is 0.1 % byweight of cement.
• Characteristics
AdvantagesReduces pressure filtrationReduced segregationEnhanced water repellant
.DisadvantagesIncreases cohesion
Dispersant• Product
Naphthalene sulfonatebased.
Enrobes cement particleswith a negative charge soparticles repell.
Typical dosage is 1- 2% byweight of cement.
• Characteristics
AdvantagesIncreased penetrabilityIncreased pumping time
.DisadvantagesIncreases set time
Testing
Properties Test UnitsCohesion Viscometer PaViscosity Marsh Funnel SecPressure Filtration Filter Press KpfBleed Cylinders %Density Mud Balance #/ft3Set Time Vicat Needle HrsCompressive Strength Cubes psi
Cohesion Testing
• Viscometer Test� Cohesion
pascals (Pa)
Evolution of Cohesion
Evolution of Viscosity from Shear Tube Test
1
10
100
1,000
10,000
0 180 360 540 720 900 1080 1260Time (minutes)
Shea
r Str
engt
h (P
a)
Mix B Mix C Mix D Mix E Mix F
Viscosity (Marsh Funnel)• Viscosity Reading
seconds
• Measure of flowabilityof fluid grout
• Water = 28 sec
• Grout = 32 – 70 sec
Pressure Filtration Testing
volume of water ejectedKpf = _____________________________________________________
initial volume of grout x (filtration time (min))1/2
Pressure Filtration Coefficients
0
0.01
0.02
0.03
0.04
0.05
0 5 10 15 20 25 30 35
Time (minutes)
Coe
ffic
ient
(1/m
in^-
1/2)
Mix A Mix B Mix C Mix D Mix E Mix F
Mud Balance
• Measures Density
• Useful test for qualitycontrol on mixconsistency
Set Time
• Vicat NeedleInitial set 25 mmFinal set 0 mm
THANK YOUPresented By:
James A. Davies, P.Eng.Advanced Construction Techniques Ltd.
3935 Lloydtown Aurora RoadKettleby, Ontario
L0G 1J0Toll Free Telephone: 877-373-7248
Email: jdavies@agtgroup.com