Protection Repair and Maintenance of Rcc Structures

8/3/2019 Protection Repair and Maintenance of Rcc Structures

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GUIDED BY

MALINI K.V. PRESENTED BY

ASST.PROFESSOR KEVIN SHIMO S7

DEPARTMENT OF CIVIL ENG.


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` Concrete expected to give trouble free service

throughout design life.

` Concrete decay is cancerous caused by

carcinogenic agents.` Physical damage caused due to fire,explosion and

restraints both external and internal.


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` Seal the surface of the concrete

` Modify the concrete to reduce its permeability

` Protect the reinforcing bars to reduce the effect of

chlorides


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` ood concrete practice

` Latex modified concrete

` Silica fume concrete

` Epoxy coated reinforcement` Providing membranes and sealers

` Cathodic protection

` Electro osmosis

` Inorganic corrosion inhibitors

` Organic corrosion inhibitors


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` Specify and introduce Chloride limit

` Maintain a low water-cement ratio in concrete

` Provide adequate cover to the reinforcing steel

`

Provide adequate curing` Use of water-reducing admixtures

` Consolidating the concrete thoroughly

` Use post tensioning

`

Include provision for immediate repair of cracks


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` Latex modified concrete is prepared by adding

liquid styrene butadiene latex to conventional

concrete

` Latex modified concrete should be placed in theevening or at night to reduce cracking


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` Silica fume reacts with calcium hydroxide to form

additional cementitious material

` Silica fume is extremely puzzolonic material that

reacts with calcium hydroxide` Performance of concrete is good to excellent


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` Pre-cleaned reinforcing steel bars are protectedwith a coating of powdered epoxy

` Coating blocks chloride ions

` Performance is poor to excellent


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` Membranes and sealers help prevent chloride

entry

` Urethanes, neoprene, or epoxies are usually used

to built up in multiple layers of membranes` The performances of these materials vary

depending upon the base of the sealer

` Sealers- linseed oil and sophisticated silanes and

siloxanes


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` controls corrosion of steel by applying direct

current

` is a complicated process that requires extensive

pre installation and monitoring` Corrosion of steel in concrete is a electrochemical

process

` Steel (reinforcement) inside the concrete act as

cathode and provide protection` Concrete act as anode

` Not recommended for carbonated concrete


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` Electro Osmosis makes it possible to restore the

initial alkalinity of the concrete

` externally applied alkaline gel covering the

external conductor is drawn` alkalinity increase of a carbonated concrete

restores the passivation

` The carbonate problem is solved


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` combine other organic chemicals for successfully

inhibiting corrosion

` inhibitor forms a protective barrier on the

reinforcing steel` barrier prevents reaction between the iron and

chloride


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` . Experience has shown that there are certain

portions of exposed concrete structures more

vulnerable than others to deterioration from

weathering in freezing climates` Concrete sealing compounds and coatings that

provide good protection from weathering


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` Determine the cause(s) of damage

` Evaluate the extent of damage

` Evaluate the need to repair

` Select the repair method` Prepare the old concrete for repair

` Apply the repair method

` Cure the repair properly


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` Surface Grinding

` Using Portland Cement Mortar

` Dry Pack and Epoxy-Bonded Dry Pack

` Preplaced Aggregate Concrete` Replacement Concrete

` Epoxy-Bonded Epoxy Mortar

` Polymer Concrete

` Silica Fume Concrete


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` It can be used to repair some bulges, offsets andother irregularities.

` Grinding of sufaces subjected to cavitation erosionshould be limited in depth so that no aggregateparticles more than 1/16th inch in cross section areexposed to finished surface.

` Grinding of surfaces exposed to public viewshould be limited in depth so that no aggregate

particles more than 1/4 inch in cross section areexposed at the finished surface


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` Dry pack is a combination of Portland cement and

sand passing a No. 16 sieve

` Dry pack should be used for filling holes having a

depth equal to, or greater than, the least surfacedimension of the repair area; for cone bolt, she

bolt etc.


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` Preplaced aggregate concrete is made by

injecting portland cement grout, with or without

sand, into the voids of a formed, compacted mass

of clean, graded, coarse aggregate` The preplaced aggregated is washed and

screened to remove fines before placing into the

forms


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` Concrete repairs made by bonding new concrete

to repair areas without use of an epoxy bonding

agent or mortar grout applied on the prepared

surface should be made when the area exceeds 1square foot and has a depth greater than 6 inches.

` Replacement concrete repairs are made by

bonding new concrete to the repair areas without

the use of a bonding agent or Portland cementgrout


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` Portland cement mortar may be used for repairing

defects on surfaces not prominently exposed

` Repairs may be made either by use of shotcrete

or by hand application methods


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` Epoxybonded epoxy mortar should be used where

the depth of repair is less than 1-1/2 inches and

the exposure conditions are such that relatively

constant temperatures can be expected` Epoxy mortars have thermal coefficients of

expansion that may be significantly different from

conventional concrete


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` difference in potential can result in the formation of

a galvanic corrosion cell with accelerated

corrosion at the repair perimeters

` The epoxy bond coat and epoxy mortar createzones of electrical potential that are different from

the electrical potential in the surrounding concrete


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` Polymer concrete (PC) is a concrete systemcomposed of a polymeric resin binder and fine andcoarse aggregate

` Water is not used to mix polymer concrete

` PC is commonly used to repair potholes inconcrete highway bridge decks,

` thereby eliminating the necessity of long andcostly road closures or detours

` the monomer molecules are chemically linked andcross linked to form a hard, glassy plastic knownas a polymer.


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` Silica fume concrete is conventional portland

cement concrete containing admixtures of silica

fume

`

Silica fume is a finely divided powder byproductresulting from the use of electric arc furnaces


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` Repair and prepared corrected area should be

carried out systematically

` application of protective coatings are required to

be properly supervised and carried out.` Surface defects like bugs holes and honey comb

require immediate repairs


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Protection Repair and Maintenance of Rcc Structures

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