Concrete Flashcards
__ reacts with___ in the concrete. __ing the _ and creating _
What is carbonation, and how does it affect reinforced concrete?
Carbonation occurs when CO2 reacts with calcium hydroxide in the concrete, reducing the pH and creating calcium carbonate. This leads to corrosion of steel reinforcement, weakening the structure.
How does chloride attack cause deterioration in reinforced concrete?
Chlorides from sources like de-icing salts or seawater penetrate the concrete and corrode the steel reinforcement, reducing durability.
What is freeze-thaw damage, and how does it affect concrete?
Water inside the concrete freezes and expands, causing cracks and weakening the structure, especially in cold climates.
What is Alkali-Silica Reaction (ASR), and what are its effects?
ASR occurs when alkalis in cement react with silica in aggregates to form an expansive gel that absorbs water, causing internal stress and cracking.
What is sulfate attack, and how does it damage reinforced concrete?
Sulfates in groundwater or soil react with the concrete, leading to softening, expansion, and structural damage.
What is honeycombing in concrete, and what causes it?
Honeycombing refers to voids or gaps in concrete caused by inadequate compaction or too much water in the mix.
How does environmental exposure contribute to concrete deterioration?
Prolonged exposure to UV radiation, acidic rain, or industrial pollutants erodes the concrete surface and weakens it over time.
How do poor-quality materials affect reinforced concrete?
Low-grade aggregates or contaminated water used in the mix lead to reduced durability and strength.
How does mechanical overloading deteriorate reinforced concrete?
Excessive loads or unexpected stresses cause cracking and fatigue, reducing the structures lifespan.
What role does physical damage play in concrete deterioration?
Impacts, abrasion, or vibrations can weaken the concrete, making it more susceptible to further damage.
How does inadequate concrete cover contribute to deterioration?
Insufficient cover exposes steel reinforcement to environmental elements, increasing the risk of corrosion.
Why is improper reinforcement placement a problem?
Poor spacing or misalignment reduces structural integrity and load distribution, weakening the concrete.
What is the effect of poor compaction on concrete?
Insufficient vibration during pouring creates voids or honeycombing, reducing strength and durability.
How does an incorrect water-cement ratio affect concrete?
Excess water increases porosity, weakening the concrete, while insufficient water leads to incomplete hydration and reduced strength.
How does inconsistent mix design contribute to concrete issues?
Incorrect ratios of cement, aggregates, and water create weak or brittle concrete that is more prone to cracking.
Why is improper curing a significant construction error?
Insufficient curing time or poor methods result in incomplete hydration of cement, reducing the final strength and durability.
How can formwork issues contribute to concrete deterioration?
Leaking or misaligned formwork causes grout loss, leading to uneven surfaces and structural weaknesses.
What is the impact of contaminated materials in concrete?
Contaminants like salts or organic materials in water or aggregates weaken the concrete and reduce its lifespan.
How does inadequate joint design lead to deterioration?
Poorly designed joints are prone to cracking and allow water ingress, accelerating deterioration.
Why is a lack of quality control during construction harmful to reinforced concrete?
Errors during mixing, placement, or curing can go unnoticed, resulting in weakened structures.
How can carbonation in concrete be repaired?
- Remove and replace carbonated concrete,
- apply corrosion inhibitors to exposed reinforcement,
- Use coatings to prevent future CO2 ingress.
Surface carbonation
Where you can see the bubbling, cracking of concrete on the surface
Depth carbonation
- c02 deep in concrete matrix
- decreases the pH and alkalinity.
- Depth carbonation also increases the risk of corrosion of embedded reinforcement steel by disrupting the passivation layer
- and facilitating the ingress of chlorides and other corrosive agents.
What are the solutions to protect concrete from chloride attack?
Apply surface sealers to prevent chloride ingress and use cathodic protection systems to counteract steel corrosion.
