Cluj-Napoca

1. Riverbank protectionvia highstrength R/C structuresA. Catarig,L. Kopenetz, P. Alexa, Aliz MatheFaculty of Civil EngineeringTechnical University of Cluj-NapocaRomania Cluj-Napoca

2. CONTEXT OF CURRENT CONTRIBUTION - LIGHTWEIGHT STRUCTURES THROUGH HEAVY CONCRETE LIGHTWEIGHT STRUCTURES  HIGH STRENGTH R/C • Though it looks a contradiction in terms, we all know that large • R/C light weight structures can be built using high strength • concrete. • The idea of using concrete for lightweight structures is neither • new nor unknown. RIVER BANK EROSION AND FLOODS  PERENIAL PROBLEMS IN ROMANIA • Romania has experienced for a long time difficulties and never solved problems regarding mainly the protection of river banks and – in general – of shore protection. Every year somwhere a bank is either sliding or some area is flooded. Recently, a national program of river bank protection has started to be implemented. LOOKING FOR A TECHNICALLY FEASIBLE AND TECHNOLOGICALLY EFFICIENT SOLUTION VIA HIGH STRENGTH R/C • Our small research team (in lightweight structures) decided to participate in the first phase – that of proposing technical and technological solutions (on a contractual basis) to this program. This is the context the present contribution of our group has come to be a current research concern. • The research program includes, also, a well known (in Romania) contractor, mainly, in dam constructions. Together, we decided to propose a technically feasible and technologically efficient solution for bank protection using modulated highstrength R/C elements that make up large lightweight strcutures.

3. Loads • Wave actions • Wind actions • Earthquake • Geological tranformations of neightbouring enviroment

4. Uncertainties • Impossibility of a total control structural behaviour in marine and other bank environments • Limits of mechanical parameters of R/C sections in marine and bank environments • Lowest geometrical limits of R/C sections in marine and bank environments

5. Short history of R/C in marine structures • Marine containers of Pier Luigi NERVI-1943. Started with a 40 mm thickness wall. Ended up with 12 mm thickness. • Technological difficulties postponed further use until 1985- development of: • High strength R/C • Self compacted R/C technology • Fibre reinforced concrete

6. Some mechanical parameters of high strength concrete • Minimum strength in compression fck= 51.0 MPa • Current values of strength in compression fck= 60.0-150.0 MPa • Reported values in laboratory investigations over 150.0 MPa • Very dense material structures • High initial compression strength • Reduced thermal reological properties • High endogen shrinkage in its first stage cracks immediately after pouring • Reduced fire resistance

7. Improving some properties • Adding steel, carbon, polypropilene fibres higher ductility, higher fire resistance • Substituting usual aggregates with lightweight aggregates reduced shrinkage and cracks • Adding silica powder (ground glass) used in electro-filters in fero-silica industry. Specific surface of a silica granule is 2000.0 sqm/kg (versus 280.0 – 450.0 sqm/kg of the usual Portland cement) better cohesion, reduced thermal reological phenomena, higher elasticity module. • Also, silica powder reduced workability higher W/C ratio. • The W/C ratio has to be between 0.20 -0.40, therefore the use of plasticizers is vital. • Plasticizers: form-aldehides, polycondenced sulphonates, melanimes (dosage under 1 %)

8. Classical bank protection solution

9. Proposed high strength R/C solutionusing shell elements river

10. Proposed highstrength R/C solution • Legend 1- Foundation 2- Equalizing concrete layer 3- Ferrocement precast shell 4- Selfcompacting concrete 5- Hole for concrete 6- Hole for air extraction

11. Proposed high strength R/C solution for retaining walls

12. Proposed floating erection technology Crane