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 %)

Classical bank protection solution

Proposed high strength R/C solutionusing 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