SUPERHYDROPHOBIC CONCRETE

America’s Infrastructure Problem:

New Concrete for Solid Infrastructure

Recent development from UW Collaborative Teams

Problem Statement

America’s infrastructure is in urgent need for repair, especially in those parts of the country subject to freezing and thawing cycles. Much of existing infrastructure was built using older design guidelines for lighter traffic levels (Abkowitz et al, 2012) and is nearing the end of its useful life. The U.S. has 18,000 bridges that could collapse without warning, according to a March 2012 report in Bloomburg Business Week on 'America's Broken Bridges'. Bridges built in the 1960's and 1970's have a life span of approximately fifty years. In July of 2012 it was stated that there are 150,000 aging US highway bridges. According to The American Society of Civil Engineers, 13% or 73,000 U.S. bridges are structurally deficient due to maintenance and corrosion issues. Globally, 360 bridges have suddenly collapsed with great loss of life.

A recent report from the American Society of Civil Engineers estimated that deficient and deteriorating roads will cost U.S. companies a cumulative $430 billion by 2020 to pay for transportation delays and vehicle repairs (ASCE, 2011). The U.S. is placed 25th in terms of quality of transportation conditions, compared to other nations belonging to the Organization for Economic Co-operation and Development (OECD) (Eloff et al 2012). In comparison between 1995 and 2009, both Japan and Western Europe have raced ahead, to spend more on inland transport infrastructure (International Transport Forum). Meanwhile, U.S. traffic congestion is worse than Western Europe and our road fatality rate is 60% above the OECD average. Over the last sixty years, total expenditures the U.S. has spent on transportation infrastructure has fallen dramatically from 5% in the 1960s to 2.4% of GDP today. In comparison, Europe spends 5% and China 9%.

Climate change is also having an impact on transportation infrastructure. Extreme and unusual weather patterns in recent years has resulted in roads and highway overpasses buckling or failing, train tracks to kink and bend and nuclear power facility cooling pools to overheat or even run completely dry. The crumbling infrastructure in the U.S. has led many civil engineers to re-evaluate their structural standards (Natural News, 2012). The New York Times stated, “Leading climate models suggest that weather-sensitive parts of the infrastructure will be seeing many more extreme episodes, along with shifts in weather patterns and rising maximum (and minimum) temperatures.” Vicki Arroyo, head of Georgetown Climate Center, a clearinghouse on climate-change adaptation strategies, remarked that “in general, nobody in charge of anything made of steel and concrete can plan based on past trends”. (Wald and Schwartz, 2012) 

Wisconsin’s concrete infrastructure has an average lifespan of 40-50 years, but approximately 10% of the infrastructure utilizes uncoated steel reinforcement prone to corrosion, providing only a 30 year lifespan (Tabatabai et al, 2005). It is essential to implement a more durable, long lasting concrete that will be safer and significantly reduce the high cost required for regular maintenance and repairs of deficient structures.

Solutions: The Next Generation of Concrete

Recent CFIRE innovative research at UW-Milwaukee offers the next generation of concrete, superhydrophobic engineered cementitious composites. This newly developed composite is made of cement-based materials with polyvinyl alcohol fibers and superhydrophobic admixtures. This material has exceptional strength and durability, essential in addressing current challenges for sustainable transportation infrastructure and safety. This novel material can replace normal concrete in critical infrastructure elements and provide an astounding lifespan of 120+ years. With this material, long term costs can be significantly lowered and a more sustainable, green product with improved durability can grace our roads, highways, and bridges.

The concept of using fibers to reinforce brittle materials is not new; in fact it has been around for thousands of years, going back to the Egyptians who used horse hair or straw to reinforce mud bricks. Frequently, the application of fibers for concrete reinforcement has focused more on non-structural applications, such as concrete art, or curvilinear concrete wall panels, enabling the concrete to be cast in a variety of shapes. However, some applications of fiber reinforced concrete especially high-performance and ultra-high performance fiber reinforced concrete (HPFRC/UHPFRC) have been implemented in structural applications boosting the performance and reducing labor costs. Experiments by Victor C. Li at the University of Michigan have demonstrated that the use of 2% by volume of polyvinyl alcohol fibers (PVA) produces excellent ductility and greater strain hardening resulting in a novel type of HPFRC, engineered cementitious composite (ECC). The strain capacity of ECC can be increased by a factor of 200 when high-strength reinforcing fibers, such as polyvinyl alcohol PVA are dispersed three dimensionally in the mortar. Shrinkage and cracking are thus controlled, but also provide extreme deformation and strain enhancement. Reduction of cracking means that water cannot penetrate the concrete and so reducing steel corrosion and deterioration of the structure. The addition of selected by-product materials or supplementary cementitious materials (SCMs) to the cementitious matrix produces a more environmentally friendly material with significantly improved durability.

Solutions: Superhydrophobic Concrete

CFIRE projects 04-09/05-10 demonstrated the feasibility of a new material based on ECC with superhydrophobic hybridization (SECC). The superhydrophobic modification approach is a highly effective method for improving the durability of concrete, especially of concrete with large volumes (up to 50%) of mineral additives or by-products used as cement replacements. Due to the reduction of portland cement and improved concrete durability, the proposed concept provides a paradigm shift in cement and concrete technology that can serve as a backbone for the sustainable development of the concrete industries. Until now, this concept has not been applied to fiber reinforced composite materials. Recent research has demonstrated that SECC provides extreme deformation and strain enhancement, over performing ECC as illustrated in Fig.1. This is possible as voids created by superhydrophobic admixtures act as artificial flaws to promote multi-cracking behavior in high strength cementitious matrices.

Fig 1. The Strain-Hardening and Improved Ductility Performance of developed SECC (Sobolev K. et al., 2013)

Superhydrophobic hybridization of concrete engages inter-disciplinary work combining biomimetics (lotus effect) (Koch et al, 2008), chemistry (siloxane polymers) (Sobolev and Batakov, 2007) and nanotechnology (nano-SiO2 particles) (Poole, 2005) to resolve the fundamental problems of concrete such as insufficient durability and corrosion resistance. The superhydrophobic admixture is used to change the volume, size, and distribution of air voids in the concrete, as well as to control the bond with PVA fibers to realize the controlled pull-out behavior. Furthermore, the controlled air void structure results in preferred multi-cracking fracture modes, Fig. 1.

Fig 2. Flexural Behavior of ECC tested at UW-Milwaukee (Sobolev K. et al., 2013)

Ensuring Smooth Connections

Another area of the collaborative UW team research is focused on ensuring a smooth transition between roadways and bridges. A “bump” forms at bridge junctions and the approach slab, as a result of uneven settlement of these structures. Different ECC/SECC mixes were tested and various criteria were studied including mixing techniques, mixing order, tools and formwork. Suitable mixes were selected for slab construction based on crack patterns, peak load, and the ability to deflect after reaching the peak load.

Looking Ahead

Research has resulted in an optimal SECC mix design and mixing protocol, providing great workability, compressive strength and flexural characteristics. Optimal fiber type and content was established as 2.5-2.75% (RECS 15X12 mm) PVA fibers. The addition of supplementary cementitious materials (SCM) resulted in an environmentally friendly composite, reducing the burden from cement production. Research has demonstrated that utilizing 5% silica fume and 45% granulated blast furnace slag creates a SECC material with an enhanced super-durable matrix. These SCMs can thus be used in SECC for material intended to last 120 or more years (Muzenski, 2012).

Contact info


  • Professor Konstantin Sobolev
    Department of Civil Engineering & Mechanics University of Wisconsin-Milwaukee
    • Email: sobolev@uwm.edu
    • Tel: (414) 229-3198

  • Professor Michael Oliva
    Department of Civil and Environmental Engineering University of Wisconsin-Madison
    • Email: oliva@engr.wisc.edu
    • Tel: (608) 262-7241

References:


  • Sobolev, Konstantin, Habib Tabatabai, Jian Zhao, Michael G. Oliva, Ismael Flores-Vivian, Rossana Rivero, Scott Muzenski, and Rehan Rauf, 2013
    • "Superhydrophobic Engineered Cementitious Composites for Highway Applications: Phase I. "No. CFIRE 04-09.

  • Abkowitz M., Camp J., Holloway T. and Harkey M., 2012

  • Eloff J., Smirnov O.A. and Lindquist P.S., 2012
    • "Transportation Infrastructure, Industrial Productivity and ROI". Mid-Continent Transportation Research Forum.

  • Muzenski S., 2012
    • "The Development of Superhydrophobic Engineered Cementitious Composites (SECC) for Use in Highway Applications". University of Wisconsin-Milwaukee. MS in Engineering.

  • Wald M.L. and Schwartz J., 2012
    • Weather Extremes Leave Parts of U.S. Grid Buckling, New York Times.

  • American Society of Civil Engineers, 2011
    • "Failure to Act: The Economic Impact of Current Investment Trends in Surface Transportation Infrastructure"., Reston, VA

  • Tabatabai H., Tabatabai M. and Lee C., 2010
    • "Reliability of Bridge Decks in Wisconsin". ASCE Journal of Bridge Engineering.

  • Kerstin Koch, Bharat Bhushan and Wilhelm Barthlott. 2008
    • "Diversity of structure, morphology and wetting of plant surfaces", Soft Matter, 4, 1943 – 1963.

  • Sobolev K. and Batrakov V., 2007
    • "The Effect of a PEHSO on the Durability of Concrete with Supplementary Cementitious Materials."., ASCE J.Materials Civil Engineering, 19(10), 809-819.

  • Becky Poole, 2005

  • Tabatabai H., Ghorbanpoor A. and Turnquest-Nass A., 2005
    • "Rehabilitation Techniques for Concrete Bridges".WHRP Report 05-01, Wisconsin Highway Research Program. p. 310.

  • Li, Victor C., 2003
    • "On engineered cementitious composites (ECC).", Journal of advanced concrete technology 1, no. 3, 215-230.

  • Kuraray Co. LTD
    • "PVA-fiber for Ductile Fiber Reinforced Cementitious Composite"

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