👉Concrete Admixtures
💫In concrete mix design, Superplasticizers, Accelerators, and Retarders are key admixtures that modify the properties of fresh and hardened concrete.
⭐️Here’s a breakdown of each:
⚡️1. Superplasticizer (High-Range Waters Reducer)
⏺Purpose:
Increases workability without adding extra water.
Reduces the water-cement ratio, enhancing strength and durability.
Helps in producing self-consolidating concrete (SCC).
⏺Types:
Sulfonated Melamine Formaldehyde (SMF)
Sulfonated Naphthalene Formaldehyde (SNF)
Polycarboxylate Ether (PCE) – Most advanced, high efficiency
⏺Dosage: Typically 0.1–2% by weight of cement.
📍Advantages:
Improves slump without compromising strength.
Reduces segregation and bleeding.
Enhances durability and resistance to sulfate/chloride attack.
⚡️2. Accelerator
⏺Purpose:
Speeds up the setting time and early strength development.
Useful in cold weather concreting.
Helps in rapid repairs and early formwork removal.
⏺Types:
Calcium Chloride (CaCl₂) – Common but not recommended for reinforced concrete due to corrosion risk.
Non-chloride accelerators (Calcium Nitrate, Calcium Formate, Sodium Thiocyanate, etc.) – Safer for reinforced concrete.
⏺Dosage: 1–3% by weight of cement.
📍Advantages:
Faster setting and early strength gain.
Reduces bleeding and shrinkage cracking.
Increases freeze-thaw resistance in cold climates.
⚡️3. Retarder
⏺Purpose:
Delays setting time to prevent premature hardening.
Useful in hot weather to avoid rapid hydration.
Helps in large pours or long transportation times.
⏺Types:
Lignosulfonates
Hydroxycarboxylic acids (e.g., tartaric acid, citric acid)
Sugars (like glucose-based compounds in small amounts)
⏺Dosage: 0.1–1.5% by weight of cement.
📍Advantages:
Extends workability time.
Reduces heat of hydration in mass concreting.
Improves surface finishing by preventing cold joints.
Choosing the Right Admixture
For high-strength concrete → Use superplasticizer (PCE preferred).
For cold weather → Use a non-chloride accelerator.
For hot weather or long transport → Use a retarder.
@etconp
💫In concrete mix design, Superplasticizers, Accelerators, and Retarders are key admixtures that modify the properties of fresh and hardened concrete.
⭐️Here’s a breakdown of each:
⚡️1. Superplasticizer (High-Range Waters Reducer)
⏺Purpose:
Increases workability without adding extra water.
Reduces the water-cement ratio, enhancing strength and durability.
Helps in producing self-consolidating concrete (SCC).
⏺Types:
Sulfonated Melamine Formaldehyde (SMF)
Sulfonated Naphthalene Formaldehyde (SNF)
Polycarboxylate Ether (PCE) – Most advanced, high efficiency
⏺Dosage: Typically 0.1–2% by weight of cement.
📍Advantages:
Improves slump without compromising strength.
Reduces segregation and bleeding.
Enhances durability and resistance to sulfate/chloride attack.
⚡️2. Accelerator
⏺Purpose:
Speeds up the setting time and early strength development.
Useful in cold weather concreting.
Helps in rapid repairs and early formwork removal.
⏺Types:
Calcium Chloride (CaCl₂) – Common but not recommended for reinforced concrete due to corrosion risk.
Non-chloride accelerators (Calcium Nitrate, Calcium Formate, Sodium Thiocyanate, etc.) – Safer for reinforced concrete.
⏺Dosage: 1–3% by weight of cement.
📍Advantages:
Faster setting and early strength gain.
Reduces bleeding and shrinkage cracking.
Increases freeze-thaw resistance in cold climates.
⚡️3. Retarder
⏺Purpose:
Delays setting time to prevent premature hardening.
Useful in hot weather to avoid rapid hydration.
Helps in large pours or long transportation times.
⏺Types:
Lignosulfonates
Hydroxycarboxylic acids (e.g., tartaric acid, citric acid)
Sugars (like glucose-based compounds in small amounts)
⏺Dosage: 0.1–1.5% by weight of cement.
📍Advantages:
Extends workability time.
Reduces heat of hydration in mass concreting.
Improves surface finishing by preventing cold joints.
Choosing the Right Admixture
For high-strength concrete → Use superplasticizer (PCE preferred).
For cold weather → Use a non-chloride accelerator.
For hot weather or long transport → Use a retarder.
@etconp