ML12153A409
| ML12153A409 | |
| Person / Time | |
|---|---|
| Issue date: | 06/01/2012 |
| From: | Office of the Chief Human Capital Officer |
| To: | |
| References | |
| Download: ML12153A409 (68) | |
Text
ology and Codes ology and Codes Troubleshooting Hardened Concrete ProblemsConcrete Techn oConcrete Techn o
When troubleshooting concrete problems it is important to relate the
s y m p tom to causes of distress yp and deterioration.
Identify Concrete Surface Identify Concrete Surface Defects DefectsACI 201.1 R ACI 201.1 R Dusting Blisters Delaminations Crazing Popouts Mortar Flaking & Scaling Spalling Bugholes Cold Joint Discoloration EfflorescenceHoneycombing (Internal?)
References References ACI 201-Condition SurveyPCA-IS177-Concrete Surface DefectsCorps of Engineers-Evaluation and Repair Guide Surface Defects Surface Defects-
-Dusting Dusting Development of a fine, powdery material at the surface of hardened
concrete.
Use Ventilated Heaters Use Ventilated Heaters Surface Defects Surface Defects-
-Blistering BlisteringThe irregular raising of a thin layer at the surface of placed mortar or
concrete durin g or soon after gcompletion of the finishing
operation.
Blisters Blisters Causes:Too many finesToomuchortoolittlevibrationToo much or too little vibrationEarly finishing
Blisters Blisters Prevention:Avoid high slumps and excess finesUseappropriatecementcontentUse appropriate cement contentWarm subgrade in cold weatherDo not place slab directly on vapor retarder Blisters Blisters Prevention:Do not overwork the concreteDonotseal(finish)thesurfacetoosoon Do not seal (finish) the surface too soonUse proper finishing techniques and timingReduce evaporationAvoid air contents of more than 3% for
interior slabs
Surface Defects Surface Defects-
-Delamination Delamination A separation along a plane parallel to a surface. In the case of a concrete slab, a horizontal s p littin g , crackin g , pggor separation of a slab in a plane
roughly parallel to, and generally near, the upper surface.
Sealing The Surface Sealing The SurfaceImproper ToolingTraps Bleed Water and Air Beneath Layer of
Mortar
Surface Defects Surface Defects-
-Crazing CrazingFine, random cracks or fissures in the surface of plaster, cement paste, mortar, or concrete.
Crazing Crazing Causes:Rapid surface drying after settingApplying dry cement to surface during finishing
Surface Defects Surface Defects-
-Popouts PopoutsConical fragment that breaks from the concrete surface. A fractured
a gg re g ate p article is often at the gggpbottom of the hole.
Popouts Popouts Causes:Porous rock with high absorption, low specific gravity:PyriteHard-burned dolomiteCoalShaleSoft, fine-grained limestoneChert Alkali-aggregate reactivity
Popouts Popouts Prevention:Use low slump, low water content mixUsedurablecrushedstoneorbeneficiated Use durable crushed stone or beneficiated aggregateSlope the slab surface to drain water properlyUse supplementary cementing materials to control ASR-induced popouts Surface Defects Surface Defects-
-Mortar Flaking Mortar Flaking A form of scaling over coarse aggregate ("popoffs")
Surface Defects Surface Defects-
-Scaling ScalingLocal flaking or peeling away of the near-surface portion of concrete or
mortar.
Surface Defects Surface Defects-
-Spalling SpallingA fragment, usually in the shape of a flake, detached from a larger mass
b y a blow, b y the action of weather, yyby pressure, or by expansion within
the larger mass.
Surface Defects Surface Defects-
-Bugholes Bugholes Small regular or irregular cavities, usually not exceeding 15 mm in
diameter, resultin g from entra p ment gpof air bubbles in the surface of formed concrete during placement
and compaction.
Surface Defects Surface Defects-
-Cold Joint Cold JointVisible lines on the surfaces of formed concrete indicating the p resence of joints where one la y er of pjyconcrete had hardened before subsequent concrete was placed.
Surface Defects Surface Defects-
-Discoloration DiscolorationA departure of color from that which is normal or desired.
Surface Defects Surface Defects-
-Staining StainingSpotted or mottled light or dark blotches.
Surface Defects Surface Defects-
-Efflorescence EfflorescenceDeposit, usually white, formed on a surface, the substance having
emer ged in solution from within gconcrete or masonry and subsequently having been precipitated by evaporation.
Surface (Internal?) DefectsSurface (Internal?) Defects-
-Honeycombing HoneycombingVoids left in concrete due to failure of the mortar to effectively fill the
s p aces amon g course a gg re g ate pgggg particles.
Durability Durability Chemical Attack Chemical Attack Durability Durability Freeze Freeze--Thaw Failure Thaw Failure Durability Durability Alkali Alkali--Aggregate Reactivity Aggregate Reactivity Durability Durability Corrosion Corrosion When troubleshooting concrete problems it is important to relate the
s y m p tom to causes of distress yp and deterioration.