कंक्रीट में नुकसान / गिरावट के कारण क्या हैं?
कंक्रीट में नुकसान के कारण क्या हैं?
संकट का अर्थ है कि क्षति
इसकी डिजाइन अवधि के दौरान विभिन्न कारकों से कंक्रीट को नुकसान हो सकता है
निर्माण सामग्री की विविधता, विधि की उपलब्धता, उपयोगिता, पर्यावरणीय स्थिति, स्थान इत्यादि के कारण, इसलिए, निर्माण कार्य की समय अवधि या सेवा शर्तों के दौरान कंक्रीट की गुणवत्ता संकट में हो सकती है।
क्षति या संकट या कंक्रीट के बिगड़ने के कारण
- संरचनात्मक कारण (Structural causes)
- बाहरी रूप से लगाए गए भार (Externally applied loads)
- पर्यावरण भार (Environmental loads)
- दुर्घटनाएँ (Accidents)
- सब्सिडी आदि (Subsidences)
- डिजाइन विचार में त्रुटियां
- खराब निर्माण कार्य
- निर्माण अधिभार
- सुखाने की सिकुड़न (Drying shrinkage)
- ताप का दबाव
- रासायनिक प्रतिक्रिया
- अपक्षय प्रभाव
- संक्षारण (Corrosion)
- प्लास्टिक संकोचन
- क्रैकिंग सेटलमेंट
- फ्रेमवर्क को जल्दी निकालना
- अनुचित डिजाइन की रूपरेखा न होना
|
Damage / Distress |
Cause |
Prevention |
Remedy |
|
Cracks
in the horizontal surface as concrete stiffens |
Plastic
shrinkage: rapid drying of concrete airfare |
Shelter during placing. Cover as early as possible. Use air-entrainment |
Seal
by brushing in cement or low viscosity polymer
|
|
Cracks
in thick sections as concrete cools |
When
contraction due to fall in temperature is prevented |
Minimize
restraint to contraction Delay
cooling until the concrete has gained strength |
Seal
crack |
|
Cracks
above ties, reinforcements etc in deep lifts |
Plastic
settlement concrete continues to settle after starting to stiffen |
Change
mix design. Use air-entrainment |
Re-compact the upper layer of concrete while still plastic. Seal cracks after the concrete have
handed |
|
Voids
in concrete |
Inadequate compaction, grout loss |
Reduce maximum size of aggregate. Improve compaction, prevent leakage of grout
|
Cut out and make good. Inject resin |
|
Rust
stains |
Pyrites in aggregate Ain streaking from unprotected steel. Rubbish in formwork. Ends of finding wires and ties |
Avoid contaminated aggregate. Protect exposed steel. Clean forms thoroughly. Turn
ends of ties inward |
Clean
with dilute acid or sodium citrate/sodium dithionite. Apply surface coating |
|
blowholes
in form faces of concrete |
Air or water trapped against formwork, inadequate compaction. Mix designs not
suitable |
Change
mix design, improve vibration, use absorbent formwork |
Fill
holes with polymer-modified fine mortar |
|
lack
of minimum cover to reinforcements |
Reinforcements
not properly fixed or moved during placing of concrete. Inadequate tolerances
in detailing |
More accurate steel fixing. Greater tolerances in detailing |
Apply
polymer modified cement and sand rendering. Apply
protective coating |
|
Erosion
of vertical faces |
Scouring:
Water moving upwards against form face |
Reduce
water content, make the mix of concrete more cohesive |
Rub
in polymer modified fine mortar |
|
plucked
surface |
Insufficient
release agent, careless removal of formwork |
More
care in applications of release
against, and removal of formwork |
Rub
in fine mortar |
