Hydrophobic Coatings for

Granular Materials

Sérgio D.N. Lourenço,

Department of Civil Engineering, The University of Hong Kong

Innotech Forum on Geotechnology (Hong Kong) - 30 May 2019

Hydrophobic coatings

2

textiles

glass

sono-tek.com

reedoshowers.com

water drop 10mm

lotus leaf

water drop

hydrophobic volcanic soil

NatureMaterials

Hydrophobic

surfaces…

Hydrophilic soil Hydrophobic soil

1mm 1mm

Granular materials

3

Animation Mr Shuang Zheng

Soils can be

hydrophobic

Applications

4

Barriers

Aim:To establish the conditions under which synthetic hydrophobic

granular materials can be deployed in ground interfaces

soil soilstructure

Advantages vs limitations…

Hydrophobic granular

materials for ground

interfaces

Lourenço SDN, Saulick Y, Zheng S, Kang H, Liu D, Lin H, Ting Y, 2018, Soil wettability in ground engineering: fundamentals, methods and, applications, Acta Geotechnica 13, 1, 1-14

Coatings

5

Natural (organic matter…)

Synthetic (silanes, oils…)

Physical characteristics

Particle size and shape

Surface roughness

uncoated coated

Hydrophobicity

depends on surface

chemistry and

topography

Lourenço SDN, Woche SK, Bachmann J, Saulick Y 2015. Wettability of crushed air-dried minerals, Géotechnique Letters 5(3), 173–177

Chan CSH, Lourenço SDN, 2016, Comparison of three silane compounds to impart water repellency in an industrial sand, Géotechnique Letters 6, 4, 1–4

Lourenço SDN, Jones N, Morley C, Doerr S, Bryant R, 2015, Hysteresis in the soil water retention of a sand-clay mixture with contact angles lower than ninety-degrees, Vadose Zone Journal 14, 7

Coatings

6

Using chemistry

Silanes (DMDCS and others)

Stearic acid + Octadecane

Oils

SAND SILT CLAY

Hydrophobicity can

be induced on sands,

silts and clays

Lin H, Lourenço SDN, Yao T, Zhou Z, Yeung AT, Hallett P, Patton G, Shih K, Hau BCH, Cheuk J, 2019, Imparting water repellency in completely decomposed granite with Tung oil, Journal of

Cleaner Production 10.1016/j.jclepro.2019.05.032

Ng SHY, Lourenço SDN, 2016. Conditions to induce water repellency in soils with dimethyldicholorosilane, Géotechnique 66(5), 441–444

Coatings

7

Using chemistry

Silanes

Graph Dr Yunesh Saulick

Critical concentration

Saulick Y, Lourenço SDN, Baudet, 2017. A semi-automated technique for repeatable and reproducible contact angle measurements in granular materials using the Sessile Drop Method, Soil

Science Society of America Journal 81 (2), 241-249

Coatings

8

Using chemistry

Silanes

uncoated particle surface coated particle surface

Coatings are thin

films (nm to µm)

Lourenço SDN, Saulick Y, Zheng S, Kang H, Liu D, Lin H, Ting Y, 2018, Soil wettability in ground engineering: fundamentals, methods and, applications, Acta Geotechnica 13, 1, 1-14

Coatings

9

Using physical characteristics

Particle size and shape & particle surface roughness

9

Particle size enhances

hydrophobicity

Saulick Y, Lourenco SDN, Baudet BA, Woche S, Bachmann J. 2018, Physical-properties controlling water repellency in synthesised granular solids, European Journal of Soil Science

10.1111/ejss.12555

Kang H, Lourenço SDN, Yan RWM. 2018. Lattice Boltzmann simulation of droplet dynamics on granular surfaces with variable wettability, Phys. Rev. E 98, 012902

Coatings

10

Properties

Triaxial

0

500

1000

1500

2000

2500

3000

0 5 10 15 20

q:

kP

a

: %

(a)

Natural sandCoated sand (0.05%)Coated sand (3%)

0

500

1000

1500

2000

2500

3000

0 500 1000 1500 2000

q:

kP

a

p': kPa

(b)

Natural sandCoated sand (0.05%)Coated sand (3%)

Undrained shear behaviour (p'=500 kPa, e = 0.651):

(a) stress-strain relation; (b) stress path

Coatings thickness

may influence

mechanical behaviour

Liu D, Sandeep CS, Senetakis K, Nardelli V, Lourenco SDN, 2019. Micromechanical behaviour of a polymer-coated sand, Powder Technology 10.1016/j.powtec.2019.02.030

Liu D, Lourenço SDN, Yang J, 2018. Critical state of polymer-coated sands, Géotechnique 10.1680/jgeot.18.P.015

Applications – slopes

11

Hydrophilic sand

0

0.1

0.2

0.3

0.4

0.5

0 5 10 15 20 25 30

vo

lum

etr

ic w

ate

r

co

nte

nt

Time (minutes)

vwc 1 vwc 2 vwc 3 vwc 4

10 min 20 min

4

2

3

1

With infiltration

Zheng S, Lourenço SDN, Cleall P, Chui TFM, Ng A, Millis S. 2017, Hydrologic behaviour of model slopes with synthetic water repellent soils, Journal of Hydrology 554C, 582-599

Lourenço SDN, Wang G-H, Kamai T 2015. Processes in model slopes made of mixtures of wettable and water repellent sand: implications for the initiation of debris flows in dry slopes,

Engineering Geology 196, 47-58

Applications – slopes

12

Hydrophobic sand

0

0.1

0.2

0.3

0.4

0.5

0 5 10 15 20 25 30

vo

lum

etr

ic w

ate

r

co

nte

nt

Time (minutes)

vwc 1 vwc 2 vwc 3 vwc 4

10 min 20 min

4

2

3

1

No infiltration

Zheng S, Lourenço SDN, Cleall P, Chui TFM, Ng A, Millis S. 2017, Hydrologic behaviour of model slopes with synthetic water repellent soils, Journal of Hydrology 554C, 582-599

Lourenço SDN, Wang G-H, Kamai T 2015. Processes in model slopes made of mixtures of wettable and water repellent sand: implications for the initiation of debris flows in dry slopes,

Engineering Geology 196, 47-58

Final thoughts

13

Inducing hydrophobicity in granular materials OK

Optimizing hydrophobicity in granular materials for

specific ground applications

Optimization…

Selected outputs1. Lin H, Lourenço SDN, Yao T, Zhou Z, Yeung AT, Hallett P, Patton G, Shih K, Hau BCH, Cheuk J, 2019, Imparting water

repellency in completely decomposed granite with Tung oil, Journal of Cleaner Production 10.1016/j.jclepro.2019.05.032

2. Liu D, Sandeep CS, Senetakis K, NardelliV, Lourenco SDN, 2019. Micromechanical behaviour of a polymer-coated sand,

Powder Technology 10.1016/j.powtec.2019.02.030

3. Liu D, Lourenço SDN, Yang J, 2018. Critical state of polymer-coated sands, Géotechnique 10.1680/jgeot.18.P.015

4. Kang H, Lourenço SDN, Yan RWM. 2018. Lattice Boltzmann simulation of droplet dynamics on granular surfaces with

variable wettability, Phys. Rev. E 98, 012902

5. SaulickY, Lourenco SDN, Baudet BA, Woche S, Bachmann J. 2018, Physical-properties controlling water repellency in

synthesised granular solids, European Journal of Soil Science 10.1111/ejss.12555

6. Zheng S, Lourenço SDN, Cleall P, Chui TFM, Ng A, Millis S. 2017, Hydrologic behaviour of model slopes with synthetic water

repellent soils, Journal of Hydrology 554C, 582-599

7. SaulickY, Lourenço SDN, Baudet, 2017. A semi-automated technique for repeatable and reproducible contact angle

measurements in granular materials using the Sessile Drop Method, Soil Science Society of America Journal 81 (2), 241-249

8. Ng SHY, Lourenço SDN, 2016. Conditions to induce water repellency in soils with dimethyldicholorosilane, Géotechnique

66(5), 441–444

9. Chan CSH, Lourenço SDN, 2016, Comparison of three silane compounds to impart water repellency in an industrial sand,

Géotechnique Letters 6, 4, 1–4

10. Lourenço SDN, Jones N, Morley C, Doerr SH, Bryant R, 2015, Hysteresis in the soil water retention of a sand-clay mixture

with contact angles lower than ninety-degrees, Vadose Zone Journal 14, 7

11. Lourenço SDN, Woche SK, Bachmann J, SaulickY 2015. Wettability of crushed air-dried minerals, Géotechnique Letters 5(3),

173–177

12. Lourenço SDN, Wang G-H, Kamai T 2015. Processes in model slopes made of mixtures of wettable and water repellent sand:

implications for the initiation of debris flows in dry slopes, Engineering Geology 196, 47-58

14

AcknowledgementsHong Kong

1. 2017-2020 GRF (HK Research Grants Council), Physically-enhanced water repellency in granular materials, PI Lourenço, Co-

I’s: Prof G McHale & Dr G Wells (Northumbria), Dr B Baudet (UCL)

2. 2016-2019 GRF (HK Research Grants Council), Durable synthetic water repellent soils for sustainable ground infrastructure,

PI Lourenço, Co-I’s: Dr Johnny Cheuk (AECOM HK), Prof Paul Hallett & Prof Graeme Paton (Aberdeen University), Dr

Albert Yeung (HKU)

3. 2015-2018 GRF (HK Research Grants Council), Hydrologic optimum of water repellent soils for slope protection, PI

Lourenço, Co-I’s: Dr. Peter Cleall (Cardiff University), Prof. Joerg Bachmann (Leibniz University Hannover)

United Kingdom

1. 2011-2013 EPSRC (Engineering and Physical Sciences Research Council UK) First Grant, The impact of water repellency on

soil mechanics EP/I008756/I, PI Lourenço, Project Partner Swansea University

2. 2012-2013 EPSRC OTG, Measurement of water menisci contact angles in bulk soil samples EP/K007904/I, PI Lourenço,

Project Partner Leibniz University Hannover

15

Thank you

16

Sérgio D.N. Lourenço

Department of Civil Engineering

The University of Hong Kong

lourenco@hku.hk