Riverbank protection via highstrength R/C structures A. Catarig,L. Kopenetz, P. Alexa, Aliz Mathe Faculty of Civil Engineering Technical University of Cluj-Napoca Romania Cluj-Napoca

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.

Loads Wave actions Wind actions Earthquake Geological tranformations of neightbouring enviroment

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

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

Some mechanical parameters of high strength concrete Minimum strength in compression f ck = 51.0 MPa Current values of strength in compression f ck = MPa Reported values in laboratory investigations over 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

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 sqm/kg (versus – 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 , therefore the use of plasticizers is vital. Plasticizers: form-aldehides, polycondenced sulphonates, melanimes (dosage under 1 %)

Classical bank protection solution

Proposed high strength R/C solution using shell elements river

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

Proposed high strength R/C solution for retaining walls

Proposed floating erection technology Crane