AVOIDING COMMON CONCRETE PROBLEMS

• DISCOLORATION• SCALING• CRAZING• CRACKING• CURLING• BLISTERS• DELAMINATION• DUSTING• EFFLORESCENCE• SPALLING• POPOUTS

DISCOLORATION

• ANY ALTERATION IN THE MIX AND BATCH MATERIALS FROM THE READY MIX LEADS TO DISCOLORATION.

• CONCRETE DISCOLORATION COULD OCCUR IF WATER IS BEING ADDED AT THE JOBSITE,BY POOR WORKMANSHIP ,DIFFERENT CEMENT MATERIAL AND EVEN IF CALCIUM CHLORIDE IS ADDED TO THE MIX.

HOW TO AVOID

• WAIT UNTIL ALL WATER HAS EVAPORATED TO START FINISHING CONCRETE

• AVOID HARD TROWELING ON EXTERIOR CONCRETE SURFACE

• CURE CONCRETE UNIFORMLY OVER THE ENTIRE SURFACE.

SCALING

• SCALING OCCURS WHEN THE CONCRETE SURFACE BREAKS OFF TO 2 INCHES AND KEEPS PEELING AWAY.

• THIS NORMALLY OCCURS DUE TO INADEQUATE CONCRETE STRENGTH,OR INADEQUATE CURING PROCEDURE.

• IT ALSO OCCURS WHEN WATER SEEPS INTO POROUS ,NON AIR ENTRAINED CONCRETE EXPOSED TO FREEZE THAW CYCLES

• CONCRETE SLABS EXPOSED TO FREEZING AND THAWING IN THE PRESENCE OF MOISTURE CAN SCALE.

HOW TO AVOID?• CONCRETE EXPOSED TO FREEZING AND

THAWING MUST BE AIR ENTRAINED.• PROTECT THE CONCRETE FROM THE HARSH WET

WINTER ENVIRONMENT• AFTER 28 DAYS SEAL THE SURFACE.

CRAZING• IT IS THE DEVELOPMENT OF A NETWORK OF FINE

RANDOM CRACKS OR FISSURES ON THE SURFACE OF CONCRETE.

• THESE CRACKS ARE RARELY MORE THAN 1/8 INCH(3MM) DEEP AND MORE NOTICEABLE ON STEEL TROWELED SYRFACES.

• OFTEN THEY ARE NOT READILY VISIBLE UNTIL THE SURFACE HAS BEEN WETTED AND IT IS BEGINNING TO DRY.

• THEY RARELY AFFECT THE DURABILITY.

CAUSES

• POOR OR INADEQUATE CURING• INTERMITTENT WET CURING AND DRYING• EXCESSIVE FLOATING ,IS THE ACCUMULATION

OF CEMENT PASTE ON THE TOP OF CONCRETE WHILE COARSE AGGREGATES SETTLES DOWN.

• EXCESSIVE LAITANCE ON SURFACE

HOW TO AVOID CRAZING• PROPER AND EARLY START OF CURING

PREVENTS LOSS OF MOISTURE IN CONCRETE AND HELPS IN HYDRATION PROCESS OF CONCRETE

• NEVER SPRINKLE DRY CEMENT OR A MIXTURE OF CEMENT AND FINE SAND ON THE SURFACE OF THE CONCRETE.

• AVOID GROUTING PROCESS OR RUBBIN THE SURFACE WITH NEAT CEMENT PASTE.

CRACKING• EXCESS OF WATER IN MIX• SHRINKAGE• DUE TO DEVELOPMENT OF THERMAL STRESSES• CORROSION OF REINFORCEMENT• POOR CONSTRUCTION PRACTICES

HOW TO AVOID

• CRACKS IN CONCRETE CANNOT BE ENTIRELY PREVENTED ,BUT THEY CAN BE MINIMIZED AND CONTROLLED WITH PROPERLY DESIGNED JOINTS.

• Dr FIXIT CAN BE USED AS CRACK FILLER.

CURLING• IT IS THE DISTORTION OF A SLAB INTO A CURVED

SHAPE BY UPWARD OR DOWNWARD BENDING OF THE EDGES

• IT IS DUE TO DIFFERENCES IN MOISTURE OR TEMPERATURE BETWEEN THE TOP AND BOTTOM SURFACES OF A CONCRETE SLAB.

HOW TO AVOID• THOROGH CURING IS REQUIRED DURING EARLY

STAGES• REDUCING MOISTURE BY APPLYING

COATINGS,SEALRS AND WAXES• DESIGN THICKER SLABS.THINNER SLABS ARE

MORE LIKELY TO CURL

BLISTERS• BLISTERS ARE HOLLOW ,LOW PROFILE BUMPS ON

THE CONCRETE SURFACE TYPICALLY OF 1 INCH SIZE

• IT OCCURS WHEN AIR GETS TRAPPED IN THE CONCRETE AND CANT BREAK OUT OF THE SEAL.

HOW TO AVOID• FINISHING SHOULD BE DONE PROPERLY.• EPOXY COATINGS CAN BE GIVEN.

POPOUTS• POPOUTS OCCUR WHEN SMALL PORTIONS OF THE

SURFACE MORTAR BREAK AWAY FROM THE CONCRETE FLATWORK.

• THIS LEAVES SHALLOW AND CONE SHAPED HOLES WITH BROKEN,DETERIORATING MATERIAL AT THE BOTTOM OF THE HOLES.

• THESE ARE CAUSED NEAR SURFACE AGGREGATE PARTICLES OR CONTAMINANTS SUCH AS CHERT,SOFT AND FINE GRAIN LIMESTONE,SAND STONE,SHALE,CLAY LUMPS.

HOW TO AVOID• USE PROPER FINISHING TECHNIQUES.• PROTECT SURFACE FROM RAPID MOISTURE LOSS.• CONSIDER SEALING THE SURFACE WITH A

BREATHABLE SEALER SUCH AS SILANE/SILAXANE.• USE ADMIXTURES LIKE FLYASH.

SPALLING• CONCRETE SPALLING IS MUCH MORE KNOWN AS

CONCRETE CANCER.• IT IS A SURFACE FAILURE THAT OCCURS WHEN

SURFACE IS SUBJECTED TO EXECESS MOISTURE,CORROSION,WEATHERING AND MUCH MORE.

HOW TO AVOID• CORROSION PROTECTION IS PROVIDED BY THE

AMOUNT OF CONCRETE COVER PROTECTING THE STEEL.

• PREVENTING SPALLATION IS USUALLY DONE AT THE OUTSET OF MIXING THE CONCRETE ,BY USING AIR ENTRAINED CONCRETE,CURING WELL

• WATER REPELENT SEALER CAN BE APPLIED AFTER THE SLAB IS CURED

EFFLORESCENCE• EFFLORESCENCE IS A CRYSTALLINE

DEPOSIT(CACO3) ON SURFACES OF MASONARY.IT IS IN WHITISH IN APPEARANCE .

• IT IS CAUSED WHEN SOLUBLE SALTS (CALCIUM HYDROXIDE)AND OTHER WATER DISPERSIBLE MATERIALS COME TO THE SURFACE OF CONCRETE AND MORTARS.IT CAN OCCUR VERY SOON AFTER EXPOSURE TO MOIST OR COOL CONDITIONS .

HOW TO AVOID• TO AVOID THE PROBLEM CONSIDER USING A

COLORED CURING COMPOUND OR CURE AND SEAL TO MATCH THE COLOR OF THE CONCRETE

• TO FIX THE PROBLEM,CLEAN THE SURFACE WITH MILD ACID OR EFFLOROSCENCE REMOVER FOLLOWED BY SEALING.

DELAMINATION• WHEN FRESH CONCRETE IS PLACED AND

COMPACTED,THE SOLIDS SETTLE.THIS NATURAL SETTLEMENT CAUSES EXCESS MIX WATER AND ENTRAPPED AIR TO BE DISPLACED AND LIGHTER PARTICLES MIGRATE TOWARDS THE SURFACE.IF FINISHING OPERATIONS START PREMATURELY DELAMINATION OCCURS

HOW TO AVOID• THE SIMPLEST WAY TO PREVENT DELAMINATION IS

TO START FINAL FINISHING OF THE SLAB AFTER THE BLEEDING PROCESS HAS RUN ITS COURSE.

• DON’T CLOSE THE SLAB SURFACE TOO EARLY

DUSTING• FORMATION OF LOOSE POWDER RESULTING FROM

DISINTEGRATION OF SURFACE OF HARDENED CONCRETE IS CALLED DUSTING/CHALKING.

• IT IS CAUSED BY EXPOSURE TO RAINFALL DURING FINISHING,A LOW CEMENT CONTENT,LACK OF PROPER CURING,CARBONATION OF SURFACE,DIRTY AGGREGATES.

HOW TO AVOID

• IT CAN BE AVOIDED BY USING PROPER MIX DESIGN AND CONSTRUCTION PRACTISE TO GIVE REQUIRED SLUMP,WITHOUT EXCESSIVE BLEEDING , SEGREGATION.

• PROVIDE PROPER CURING• NEVER SPRINKLE OR TROWEL DRY CEMENT

INTO THE SURFACE OF PLASTIC CONCRETE TO ABSORB BLEED WATER.

• SURFACE HARDENER CAN BE APPLIED OVER SLAB

CONCLUSION• THE CONSTRUCTION PROCESS MUST BE DONE IN

VERY EFFICIENT MANNER ,A SINGLE MISTAKE MAY SOMETIMES LEAD TO SERIOUS ISSSUES.SO A WELL MANNERED CONSTRUCTION PROCESS MUST BE ADOPTED TO HAVE A SAFE ,SUSTAINED,DURABLE STRUCTURE.

THANKYOU