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HISTORIC INFRASTRUCTURE REHABILITATION WITH FABRIC REINFORCED CEMENTITIOUS MATRIX (FRCM)

COMPOSITES

Diana Arboleda, Francisco De Caso, and Antonio Nanni

INTRODUCTIONTourism in Cuba is expected to grow exponentiallynow that the United States government has easedsome of the travel restrictions to that country. Sud-denly, Cuba is one of the hottest destinations on theplanet (ABC News, 2016). Two of the main touristdraws are the vintage cars and the diverse historicalarchitecture, both captured like in a time capsule,practically frozen in time since the Cuban revolutionover 50 years ago. Cuba—and especially Havana—isa treasure trove of architectural styles spanning sixcenturies. With buildings dating from the 16ththrough the 19th centuries, Havana is one of themost authentic colonial cities in the Americas (Hava-na Architecture, 2016). Its architectural diversity in-cludes the Colonial & Baroque period (16-17th cen-tury), Neo-classical period (18-19th century), ArtNouveau, Art Deco & Eclectic influences (20th cen-tury), as well as modernist, revolutionary, and con-temporary styles. Slowly over time, however, thebeauty and grandeur of Cuba faded away as Havana’shistoric buildings began to decay and deteriorate dueto lack of maintenance, lack of funds, an aggressiveclimate and non-existent governmental programs topreserve Cuba’s architectural heritage (Thirdeye-mom, 2016).

The positive impact that the influx of tourists willhave on the Cuban economy is clear, but so is thetremendous strain on Cuba’s aging infrastructurewhich is already in distress. In addition to new con-struction to satisfy the increased demand, rehabilita-

tion of current structures, especially historical ones, isimperative.

CHALLENGES BEING ADDRESSEDImproving structures related to tourism and trans-portation infrastructure are key priorities for the Cu-ban government (Green, 2016). The state of disre-pair of the architectural heritage as well as of thetransportation infrastructure (roads, bridges, airports,ports, railroads) is always in focus when discussionsof investment and tourism in Cuba take place. Alongwith others, the City of Havana, designated WorldHeritage Site by UNESCO, is currently in very poorshape, with crumbling infrastructure, inadequateroads, and crumbling façades (Patel, 2015). Much ofOld Havana’s built fabric is in disrepair due to decay,chronic neglect and the natural elements (UNESCO,1982).

Most roadways, highways and streets are in dire needof safety improvements such as pavement restoration,including fixing pot holes, along with resurfacing toincrease the life, rideability, and overall structuralperformance (Alfonso and Penin, 2009). Inefficientmaintenance, advanced corrosion, and seismic vul-nerability of bridges in Cuba make them a priorityfor repair and restoration (Subiaut, 2012, Sánchez etal., 2012).

STRUCTURAL REHABILITATIONTraditional techniques for rehabilitation of damagedor deteriorated structures include external applica-tion of fiber-reinforced polymers (FRP), steel plate

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bonding, section enlargement, and external post-ten-sioning. These methods are already known and usedin Cuba. The country has a strong background in en-gineering education and training, due in part to sev-eral university institutions (Alfonso and Penin,2009). One of the most commonly used external re-pair/strengthening method is the use of FRP, whichconsists of applying a “skin” on the damaged struc-tural element. This “skin” is defined as a structuralfabric applied with a polymer (Figures 1 and 2); ithas numerous advantages such as compatibility withthe substrate, protective of the substrate, lightweight,durable, and does not require formwork.

The FRP solution, however, also has some disadvan-tages such as no inherent fire protection, not suitablefor historical restoration (if removal were to be neces-sary or if vapor permeability were to be required), in-tense substrate preparation, poor behavior of epoxyresins at temperatures above the glass transition tem-perature, inability to apply on wet surfaces or at lowtemperatures, and some concern that epoxy resinscould be a toxic hazard to the installer. Additionallythere is a required level of skill needed to ensureproper installation of such technologies.

An alternative to FRP involves replacing the poly-meric matrix with a cementitious matrix such as fer-rocement, textile reinforced mortar (TRM), and fab-ric reinforced cementitious matrix (FRCM)composites which are also external repair systems.Ferrocement, already well known and used in Cuba,consists of a metal mesh embedded in mortar/paste.These systems offer the same advantages as FRP plus

fire protection, suitability for historical restoration,ease of substrate preparation, compatible permeabili-ty with the substrate, and an inorganic, non-toxicmatrix.

FRCM SYSTEMA new class of composite materials, FRCM is consid-ered as the natural evolution of ferrocement wherethe steel mesh reinforcement, which is vulnerable tocorrosion, is replaced with man-made and naturalmaterials such as carbon, basalt, polyparaphenylenebenzobisoxazole (PBO), hemp, flax, bamboo, or glassfiber fabrics (Figure 3).

The possibility of using thin-section cementitiousproducts as repair materials for concrete and masonrystructures makes them ideal for historic restoration.FRCM is a system where all constituents are devel-oped and tested as a unique combination and shouldnot be created by randomly selecting and mixingproducts available in the marketplace. FRCM can be

Figure 1. Typical FRP application

Figure 2. Examples of strengthening of historical and modern masonry with FRP

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applied to substrate surfaces subjected to moisturevapor transmission. The transmission of moisture va-por from a substrate surface does not typically com-promise the bond between the FRCM and substrate.

Typical FRCM installation involves first a simplepreparation of the substrate that involves removal ofprevious damage and cleaning to eliminate debris.Then, a thin layer of the mortar (cementitious ma-trix) is applied to the surface of the structural mem-ber to be strengthened manually with a trowel as inFigure 4 (left), then the fabric is applied with the pri-mary fabric orientation in the direction of the load asin Figure 4 (center), and a finishing layer of the mor-tar is applied to the last fabric layer, completing thecomposite as in Figure 4 (right). The FRCM com-posite hardens within a few hours and achieves fullstrength at 28 days.

Installation of FRCM is simple and can be per-formed by construction workers after minimal train-ing.

FRCM APPLICATIONSNumerous commercial projects in Europe and theUnited States have already demonstrated the poten-tial for FRCM composite applications (Nanni 2012)

for infrastructure strengthening. In Figure 5, a work-er installs FRCM onto the soffit of an unreinforcedconcrete vault, then advances rolls of the fabric net-work. Then a second fabric layer is installed over thefirst layer. Figure 6 shows how rolls of the fabric net-work hang from the vault as the scaffolding is ad-vanced (Nanni, 2012).

Figure 3. FRCM reinforcement fabric examples. Left: carbon fabric, right: PBO fabric

Figure 4. Application of FRCM on a masonry wall

Figure 5. Repair of unreinforced concrete vault

Source: Nanni, 2012

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Figure 7 shows a structural steel trestle supported bynumerous trapezoidal concrete pedestals in need ofrepair and in Figure 8, workers apply PBO fabricover a layer of the cementitious mortar matrix thathad already been applied to one of the pedestals(Nanni, 2012).

PROVISIONS FOR FRCM

In the United States, new materials such as FRCMcan be accepted as code compliant by the Interna-tional Building Code (IBC), by means of supportingevidence in the form of valid research reports demon-

strating compliance to published acceptance criteria,performed by accredited laboratories. A criterion forevaluation and characterization of passive FRCMcomposite systems used to strengthen existing ma-sonry and concrete structures was developed and re-cently published by the International Code CouncilEvaluation Service (ICC-ES) in conjunction with ac-ademia. The ICC-ES document is titled: AC434,“Acceptance Criteria for Masonry and ConcreteStrengthening Using Fabric-Reinforced Cementi-tious Matrix (FRCM) and Steel Reinforced Grout(SRG) Composite Systems”, and it establishes theguidelines for tests and calculations in order to re-ceive an Evaluation (Research) Report (ESR) fromICC-ES. The research report is then used to demon-strate code compliance with any of the I-Codes.FRCM properties evaluated include axial, flexuraland shear capacities of the FRCM system; perfor-mance of the FRCM system under environmentalexposures; performance under exposure to fire condi-tions; and structural design procedures.

Furthermore, the American Concrete Institute pub-lished ACI 549.4R-13, “Guide to Design and Con-struction of Externally Bonded Fabric-ReinforcedCementitious Matrix (FRCM) Systems for Repairand Strengthening Concrete and Masonry Struc-tures.” This guide provides background information,field applications, FRCM material properties, capaci-ties of the FRCM-strengthened structures (axial, flex-

Figure 6. Rolls of fabric hang while scaffolding is advanced.

Source: Nanni, 2012

Figure 7. Structural steel trestle supported by trapezoidal concrete pedestals

Source: Nanni, 2012

Figure 8. Application of PBO fabric over the cementitious matrix

Source: Nanni, 2012

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ural, and shear), and structural design procedures.ACI 549 is harmonized with AC434 and uses its pro-tocols for FRCM characterization

CONCLUSION

Cuba’s tourism will increase exponentially as a resultof normalization of relations with the US. While Cu-ban authorities and the private sector are already ad-dressing new construction and repair of the inade-

quate and aging infrastructure and architecturalheritage, this paper presented the state of FRCMcomposite systems as a reliable and adequate solutionfor historical rehabilitation. FRCM as a repair tech-nology can greatly benefit the restoration of Cubanhistorical treasures and infrastructure and positivelyimpact the Cuban economy.

REFERENCES

ABC News. 2016. “What U.S. Tourism Means forCuba,” http://abcnews.go.com/International/american-tourism-cuba/story?id=39968117. Ac-cessed July 26, 2016.

AC434. 2016. “Acceptance Criteria for Masonry andConcrete Strengthening Using Fabric-Rein-forced Cementitious Matrix (FRCM) and SteelReinforced Grout (SRG) Composite Systems,”Whittier, CA: ICC Evaluation Service.

ACI Committee 549. 2013. “Guide to Design andConstruction of Externally Bonded Fabric-Rein-forced Cementitious Matrix (FRCM) Systemsfor Repair and Strengthening Concrete and Ma-sonry Structures,” Farmington Hills, MI: Ameri-can Concrete Institute.

Alfonso, S. and Penin, C. 2009. “Transportation In-frastructure in a free Cuba: How to Meet De-mands in a Challenging Economic Environ-ment,” Cuba in Transition--Volume 19,Association for the Study of the Cuban Econo-my, 487-492.

Green, E. 2016. “The State of Cuba’s Infrastruc-ture,” http://www.engineering.com/IOT/Arti-cleID/11567/The-State-of-Cubas-Infrastruc-ture.aspx. Accessed July 20, 2016.

Havana Architecture. 2016. http://www.havanaar-chitecture.info. Accessed July 19, 2016.

Nanni, A. 2012. “A new tool in the concrete and ma-sonry repair,” Concrete International, April, 43-47.

Patel, N. 2015. “The Future of Havana: Architectureas Ticking Time Bomb,” https://www.in-verse.com/article/9039-the-future-of-havana-ar-chitecture-as-ticking-time-bomb. Accessed July20, 2016

Sánchez, D.C., Melgares, G.G., Cornier, F.C. 2012.“Métodos Experimentales para la Estimación dela Vulnerabilidad Sísmica de Puentes Prefabrica-dos de Hormigón: Puente Arroyito," Rev. Fac.Ing. UCV, vol.27 no.2, Caracas.

Subiaut, K. 2012. “El Puente de Hierro en MatanzasLlegó al Final de su Vida,” https://espejodecu-ba.wordpress.com/2012/02/14/el-puente-de-hi-erro-de-versalles-en-matanzas-llego-al-final-de-su-vida. Accessed July 20, 2016.

Thirdeyemom. 2016. https://thirdeyemom.com/2014/04/15/saving-old-havanas-beautiful-past.Assessed July 19, 2016.

UNESCO. 1982. http://whc.unesco.org/en/list/204.Accessed July 20, 2016.