Causes for Concrete Deterioration

causes for concrete deterioration are many, 1. Accidental loading: earth quake Spalling or cracking can occur, this failure are can not be predicted. Hence during construction time structure has to be design with extra caution or safety. 2. Chemical reactions:  Acids: reacts adversely with calcium silicate hydrate and weakens the concrete. Sulphuric acid when exposed to concrete surface weakens the concrete, and when it reaches to steel creates much damage. Effects : loss of cement paste and aggregate from matrix. Protection measures: An approved coating or treatment, or using dense concrete while construction with low w/c ratio will protect when mild exposure is noted.  Aggressive water attack: aggressive water is soft water and having low concentration of dissolved minerals. Effects : Leaching of concrete (removes calcium form cement paste). Protection measures: Cement based coating (not Portland) can be applied.  Alkali-carbonate rock reaction: Occurs when impure dolomitic aggregates exist. Effects : map or pattern crack , Using petrographic examination it can be identified Protection measures: such aggregate should be avoid for using.  Alkali-silica reaction: calcium alkali silica or alkali silica compound will consume water and it will expand. Causes concrete to distress Effects : map or pattern crack , Protection measures : Using concrete that should be less than 0.60% alkalies.  Various chemical attcks: concrete can with stand for moderate chemical. Where such cases when high exposure rate (such as in concrete pipes passing fluid with high pressure) have potential to ingress and can create damage. Protection measures : Using approved protective coating.  Sulfate attack: Sulphateconcrete(react with free calcium hydroxide)=calcium sulphate(gypsum)+hydrated calcium aluminate=calcium sulfoaluminate= this reaction can cause increase in volume and causes distress. Effects : map or pattern crack , Protection measures : low water cement ratio, and dense concrete 3. Poor workmen ship:  Adding to much water  Poor alignment of formwork

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Improper consolidation Adding extra layer concrete to existing surface. Use of tamper Other miscellaneous

4. Corrosion: Corrosion of reinforced bar, can causes cracking of surface, and spalling of concrete  Provide adequate cover to reinforcement  Provide suitable drainage.  Pay attention to any protrusions, such as bolts and anchors.

5. Design mistake: Inadequate structural design, neglecting minor design details Provide 6. Abrasion: cause for this failure is water borne debris, it will roll on the concrete surface and grind the surface. Reason for this poor hydraulic design 7. Design mistake:Corrosion of reinforced bar, can causes cracking of surface, and spalling of concrete