Hydrophobic hemp shiv aggregates using a facile one-step silica based coating for the building industry


Chemical composition and the geometric structure of a surface of a material are the two main attributes that govern the wettability characteristics of any material. In pursuit for better and economical building materials, researchers have unearthed hemp shiv: the woody core of the hemp plant. Hemp shiv has been seen to possess exemplary attributes (such as excellent thermal insulation, hygroscopicity, mechanic-ability, biodegradability and good acoustic absorbance) that approve its utilization in the fabrication of light weight composites. Contra wise, not only does hemp shiv possess a higher water absorption rate due to its highly porous structure, but also has cellulose, hemicellulose and lignin which make it incompatible with hydrophobic thermoset/thermoplastic polymers. Excess moisture conditions can lead to degradation and decay of hemp based composites. Consequently, this can be resolved by converting cellulose-based hydrophilic materials to hydrophobic via chemical modification. Several techniques have already been established, however, none is applicable for the treatment of hemp shiv. Fortunately, sol-gel technology has shown good results when used to deposit silica-based water repellant coatings on bio-based materials. Therefore, there is need to investigate its capability to efficiently coat hemp shiv.

To this note, a team of researchers, Atif Hussain (PhD Student), Dr Juliana Calabria-Holley, Dr Yunhong Jiang and Dr. Mike Lawrence at the BRE Centre for Innovative Construction Materials- Department of Architecture and Civil Engineering at University of Bath in the UK in collaboration with Canadian researchers at University of Laval, Dr Diane Schorr and Professor Pierre Blanchet incorporated sol-gel technology for the first time in the treatment of hemp shiv in order to develop a superior bio-based aggregate for sustainable high performance thermal insulation building composites. Additionally, they investigated the influence of catalysts, solvent dilution and hexadecyltrimethoxysilane (HDTMS) loading in the silica sols on the hydrophobicity of hemp shiv surface. Their work is currently published in the research journal, Applied Surface Science.

Their research method commenced with the preparation of the hydrophobic coatings. Next, the water contact angle of the uncoated hemp shiv samples was determined. Using 3D optical profilometer, the researchers obtained the topography and surface roughness of the samples. They then proceeded to analyze the surface elemental and chemical composition of the samples. Lastly, they characterized the surface morphology of the specimens using scanning electron microscopy.

The authors observed that the hydrophobicity of sol-gel coated hemp shiv increased significantly when using acid catalyzed sols which provided water contact angles of up to 118° at 1% HDTMS loading. The researches also noted that the ethanol diluted sol-gel coatings enhanced the surface roughness of the hemp shiv by 36% as observed under 3D optical profilometer. Finally, the X-ray photoelectron spectroscopy results revealed that the surface chemical composition of the hemp shiv was altered by the sol-gel coating, blocking the hydroxyl sites responsible for hydrophilicity.

Atif Hussain and colleagues study presented a facile single step dip-coating process that was successfully applied to form a hydrophobic surface onto an extremely hydrophilic bio-based aggregate. Generally, the hydrophobic properties were achieved through a combination of topological alteration and chemical modification of the hemp shiv by the modified silica-based sol-gel coatings. Altogether, coatings with low HDTMS precursor loading would be of interest to the bio-based building industry due to its hygroscopic properties, long shelf life, economical and lower environmental impact.

Hydrophobic hemp shiv aggregates using a facile one-step silica based coating for the building industry - Advances in Engineering

Hydrophobic hemp shiv aggregates using a facile one-step silica based coating for the building industry - Advances in Engineering

Hydrophobic hemp shiv aggregates using a facile one-step silica based coating for the building industry - Advances in Engineering


About the author

Atif Hussain (Corresponding Author) is a Doctoral Researcher in the Department of Architecture & Civil Engineering, University of Bath, United Kingdom. His PhD focuses on enhancing the hydrophobicity of bio-based aggregates using functionalised silica coatings for the development of novel high performance thermal insulation building materials. Atif is currently working on the European Union Horizon2020 funded research programme ISOBIO involving several industrial and academic partners. Atif has received the title of a Queen Elizabeth Scholar (QES) in 2016 for being awarded the prestigious QES scholarship by the Canadian Government for a Doctoral Fellowship at Université Laval, Quebec.

Atif is a material scientist and his interests mainly focus on the development of innovative polymeric composites using organic or inorganic fillers. He has expertise in nano-surface engineering, formulation and application of multi-functional coatings, interface micro-structure and mechanical behaviour of composites. His publication record holds 7 peer reviewed journal papers and 6 conference papers.

Atif obtained a first degree in Biotechnology from Manipal University, Dubai in 2008 followed by Master’s degree in Chemical Engineering from University of Leeds, United Kingdom in 2011. Prior to joining as a PhD student at University of Bath in 2015, he had been working as a Research Assistant at the Chemical Engineering Department, United Arab Emirates University, Abu Dhabi for three years developing thermal insulation materials made of polymer and fillers such as recycled rubber, clay and date fibres.

About the author

Dr Juliana Calabria-Holley is a Lecturer in the Department of Architecture and Civil Engineering. Her main research interests lay with nanotechnology applied to innovative construction materials.

Dr Calabria-Holley is a material Scientist and experienced Architect. As an Architect she has conducted over ten years of self-employed architectural practice, six years of which were carried out simultaneously with her Masters from Federal University of Minas Gerais (UFMG), Brazil and her PhD from UFMG, Brazil and Imperial College of London, UK. Both in the field of Materials Science and Engineering.

She joined the University of Bath as a Lecturer in May 2014, appointed to the BRE Centre for Innovative Construction Materials (BRE CICM) research group. Her research expertise spans from architecture to material science, and is focused on the interdisciplinary development of innovative and low carbon construction materials. Her research activities centre on nanotechnology applied to cementitious systems, surface engineering via sol-gel, adsorption processes and porosity systems, micro and nanostructure of natural building materials. Academically her work is cross-disciplinary, expanding boundaries and, more importantly, delivering a new interdisciplinary interface. Dr Calabria-Holley’s innovative work has led to an award winning publication in her field, and over 25 high profile journal and conference papers.

About the author

Dr Diane Schorr is a post doctorate researcher at Laval University, Quebec City, Canada under the mentorship of Pr Pierre Blanchet. She is working with FPInnovations to improve the dimensional stability of wood for exterior application (siding). She obtained a BSc in chemistry from University of Brest in 2008, a master degree on analytical chemistry from University of Nantes in France in 2010 and a PhD on wood science from Laval University in Quebec City in 2014. She has published more than 12 peer-reviewed papers, 2 book chapters and 3 conference papers. She supervised the work of 5 MSc and PhD students during her post doctorate period.

Her research interests are characterization and valorization of biomass. She worked in projects involving the isolation of the lignins of the black liquor and their modification to incorporate them in composite polymers. She conducts research in the area of volatile organic compounds and formaldehyde regulations, and of wood modification in order to help the wood industries in their issues of exterior wood application.

About the author

Dr Yunhong Jiang earned his PhD in Chemical Engineering in 2011 from the University of Leeds, after his BEng (2003) and MSc (2006) from China. He has been working on nanomaterials and bio-based sustainable materials at the University of Bath since 2015 and has extensive research experience in nanomaterials synthesis, materials characterization, sustainable chemistry and functional nanostructure materials. He has published over 20 peer-reviewed journals (H-Index of 11) and one book chapters. He has been invited as a reviewer more than 30 times by 16 different peer-reviewed journals and has been awarded the Outstanding Contribution in Reviewing for Composites Part A (2017). He has been serving as an editorial board member of reputed Journals.

His research interests cover a wide range including:

  • Innovative and Sustainable Construction Materials
  • Advanced Functional Composite Nanomaterials
  • Nanoparticle Synthesis, Characterisation and Application
  • Application of Nanotechnology in Bio-based Building Materials
  • Hygrothermal Performance of Bio-based Materials
  • Nano-Biological Cell Interactions and Nano-Toxicity

About the author

Mike Lawrence PhD MSc MA CEnv FIMMM FCMA FHEA is a Lecturer in Low Carbon Design at the University of Bath, Department of Architecture and Civil Engineering. He is also a founding director and trustee of Earth Building UK and Ireland Ltd, and chairman of Low Carbon Consultancy Limited. Mike’s interests and expertise revolve around sustainable construction with particular emphasis on bio-based materials as well as all forms of historic construction including timber frame, earth, lime, stone and brick.

In addition to his academic qualifications, Mike is a Chartered Environmentalist, a Fellow of the Institute of Materials, Minerals and Mining, a Fellow of the Higher Education Academy and a Fellow of the Chartered Institute of Management Accountants.

Mike has been the Principal Investigator at the University of Bath for three substantial research projects to the combined value of in excess of €8 million, and co-investigator of further projects to the value of €6 million. Mike also founded the Building Research Park, which now hosts multiple research programmes into sustainable construction.

Mike Lawrence trained as an accountant working in banking, the photographic and pharmaceutical industries. This was followed by 13 years running a bookselling business during which time he obtained an MA with distinction in Arts Education at the Central School of Speech and Drama. Between 1995 and 2011 he was Managing Director of the Ham Hill Stone Company and managing director Conservation Consultants (Worldwide) Ltd, offering consultation into the conservation of historic buildings between 1995 and 2012. He has worked at the BRE Centre for Innovative Construction Materials at the University of Bath since 2007. His publication record includes 50 peer reviewed journal papers, and a further 40 pieces including conference papers, book chapters and articles.

About the author

Pierre Blanchet, Ph.D. Holder of NESERC industrial research chair on ecoresponsible wood construction is Professor of secondary manufacturing in the wood engineering program at Laval University. He is the holder of the National Science and Engineering Research Council of Canada industrial research chair on ecoresponsible wood construction, a major research initiative with $7, 400,000 funding. 69 postgraduate projects were achieved since 2013 in his research program.

His research interests are from the design to the end of life of the buildings in the climate change challenge. Most of his research is achieved under industry-university partnership, leading him to actively work with 22 industrial partners and government agencies. He has published 106 peer reviewed paper in a wide variety of journals; product development, design, material science, coatings, green chemistry, construction management, wood technology and more.

He has active international collaboration with research scientists and professors in Chili, USA, UK, France, Belgium, Italy, Finland, Nederland and Austria. He is part of two research groups, the Research Center for Renewable Materials (CRMR) and the Interdisciplinary Research Center on Sustainable Development operationalization (CIRODD). Pierre is a member of the Quebec Forest Engineer Order and Canadian Green Building Council.

Prior to 2013, he was research leader with Forintek Canada Corp and FPInnovations for 10 years, leading the research program of Canada’s national forest product institutes in secondary manufacturing and value-added wood products.


Atif Hussain, Juliana Calabria-Holley, Diane Schorr, Yunhong Jiang, Mike Lawrence, Pierre Blanchet. Hydrophobicity of hemp shiv treated with sol-gel coatings. Applied Surface Science, volume 434 (2018) page 850–860

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