riverbank protection via highstrength r/c structures a. catarig,l. kopenetz, p. alexa, aliz mathe...
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Riverbank protectionvia highstrength R/C structuresA. Catarig,L. Kopenetz, P. Alexa, Aliz Mathe
Faculty of Civil EngineeringTechnical University of Cluj-Napoca
Romania
Riverbank protectionvia highstrength R/C structuresA. Catarig,L. Kopenetz, P. Alexa, Aliz Mathe
Faculty of Civil EngineeringTechnical 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-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
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
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 %)
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