High Shear Mixing and High-Energy Mixing in Two-Stage mixing concrete

M. Yahg: High Shear Mixing (HSM)

Vladlen Fridman: High-Energy Mixing

(HEM)

Cement + Water (Slurry) Cement + Water (Slurry) Cement + Water + Sand

(Mortar)

Main result of

method

“Disperse cohesive powders, such as cement powder”, “increase area of interface

between the components”, “inhomogeneities are reduced”

Increase C-S-H gel formation, accelerate cement

hydration.

Main idea of

method

Provide in “laminar shear flow” Shear stress and Shear rate to break cement

agglomerates, “

Provide increased Energy absorption to activate cement

hydration and create nanostructure of CSH gel (bottom-

up approach in Nanotechnology)

Parameters of

mixing

1/2hp (368wt) Osterizer blender, Speed above 3000 rpm, Energy about 5.5KJ/kg, time

1 min. (M. Yang, H.M. Jennings “Influences of Mixing Methods on the

Microstructure And Rheological Behavior of cement Paste”, Elsevier Science Inc.,

1995

Energy 5.0-400 KJ/kg, Power 30-600wt/kg, quasi

laminar flow, Re number 20-800, Np= 0.1-4.0, time 3-5

min. (Vladlen Fridman, US 20130305963)

Comparison of

Energy

absorption in

Mixing process

0

50

100

150

200

250

0 50 100 150 200 250 300

Ne

t P

ow

er

wat

t/kg

Time of mixing, sec

Specific Net Power

HSM Slurry

HEM Slurry

HEM Mortar

Parameters for

Processes

fulfilled

in lab.

conditions

HSM

W/C = 0.37

Absorbed Energy 4432 J/kg, average Re number = 1718, average Np = 0.027

HEM

W/C = 0.37

Absorbed Energy 32220

J/kg, average

Re number = 529, average

Power number

Np = 0.15

HEM

W/C/S = 0.39/1/2

Absorbed Energy 32108

J/kg,

Average Re number

110.5

Average Power number

Np = 0.86

Rate of

Hardening

With

Penetration

Resistance

Method

(Tuthill

and Cordon)

High-Energy Mixed

Slurry W/C=0.37

Bleeding water 0.18%

of total quantity.

Syneresis visible

on samples magnified

x100

High-Energy mixed mortar W/C/S = 0.39/1/2,

High-Shear mixed slurry W/C=0.37 Bleeding water 0.0 %

Bleeding water 0.58% of total water Macro-syneresis of HEM activated mortar

(evidence of C-S-H gel formation)

Allowed quantity of Fly Ash

without loss of concrete strength

HSM (C+W)

No more than 15% of cement quantity

-----

HEM (C+W+S)

Up to 50% of cement quantity

0

1000

2000

3000

4000

5000

6000

0 2 4 6 8 10

Pe

ne

trat

ion

re

sist

ance

, psi

Time, hours

Control

HSM

0

2000

4000

6000

8000

0 5 10 15

pe

ne

trat

ion

re

sist

ance

, psi

Time, hours

control

HEM

0

2000

4000

6000

8000

10000

0 2 4 6 8 10

Pe

ne

tre

tio

n r

esi

stan

ce, p

si

Time, hours

control

HEM

Power absorption in activation with two methods: HEM and HSM

a) Cement – Water mixes

High-Shear Mixing, η=55%

Re=4874, N=7115,W/C=0.43

High-Shear Mixing, η=34%

N=5615, Re=1718 W/C=0.36

High-Shear Mixing, η=10%

N=3045rpm,Re=580 W/C=0.37

0

50

100

150

200

250

300

350

0 1000 2000 3000 4000 5000 6000

Net

Po

we

r, w

t/kg

Re number

Power absorption by the cement-water mixtures

High-Energy Mixing, η = 10-54% C-S-H gel Creation Re=20-800, N=600-3000 rpm, w/c=0.26-0.40

b) Cement – Sand - Water mixes

High-Shear Mixing, η=10%

N=3045rpm,Re=580 W/C=0.37

0

50

100

150

200

250

300

350

0 1000 2000 3000 4000 5000 6000

Net

Po

we

r w

t/kg

Re number

Power absorption by the cement-sand-water mixtures

High-Shear mixing,η = 55%, Re=4874, N=7115,W/C=0.43

High-Shear Mixing,η = 34% N=5615, Re=1718 W/C=0.36

High-Energy Mixing, η=10-55% C-S-H gel creation, Re=20-800 N=600-3000rpm, W/C=0.0.36-0.58 C/S=0.25-3.0