are you having problems with the surface of your concrete scaling: this could be why

Updated: March 12, 2025

Author: Mike Day

concrete surface issues t1l

The shift from Type 1 cement to Type 1L cement in ready-mix concrete is primarily driven by the need to reduce the carbon footprint of the construction industry.

Here's a breakdown of the key reasons:

Reduced Carbon Emissions:

  • Cement production is a significant contributor to global CO2 emissions. Type 1L cement, also known as Portland Limestone Cement (PLC), reduces these emissions by substituting a portion of the clinker (a key ingredient in traditional cement) with limestone.  
  • This substitution lowers the amount of energy required for clinker production, resulting in a substantial decrease in CO2 output.
  • The construction industry is increasingly focused on sustainability, driven by factors like climate change concerns and regulatory pressures.

is type 1L concrete causing surface scaling problems?

concrete surface scaling issues t1l
concrete surface scaling issues type 1l cement

While Type 1L cement offers significant environmental benefits, its use can introduce some potential challenges in concrete performance.

Here are some of the key concerns:  

Surface Characteristics:

  • Type 1L concrete can sometimes result in a softer, more porous surface. This can increase its susceptibility to scratches, staining, and other forms of damage.  
  • This can also create issues with finishing, particularly in applications requiring smooth, durable surfaces like polished concrete floors.  

Water Demand and Workability:

  • Type 1L concrete often requires higher water demand, which can affect its workability and finishing characteristics.   
  •  Changes in water demand can also lead to issues with bleeding (water rising to the surface) and setting times. 

Cracking:

  • Increased water demand can contribute to higher shrinkage, which can increase the risk of plastic and drying shrinkage cracks. 

Set Times:

  • Variations in limestone content can affect the setting time of the concrete, leading to inconsistencies in construction schedules. 

Admixture Compatibility:

  • The interaction between Type 1L cement and concrete admixtures can differ from that of traditional Type 1 cement. This may require adjustments to admixture dosages and mix designs. 

Strength Development:

  • In some cases, Type 1L concrete may exhibit slightly slower early strength gain compared to Type 1 concrete.

Concrete contractors and industry experts thoughts about type 1l concrete

Type 1L concrete contains interground limestone, this presents challenges like reduced durability, increased water demand, and potential for cracking, especially in harsh environments or with improper curing, compared to traditional Type 1 concrete.

Here's a more detailed breakdown of the potential problems associated with Type 1L concrete:

1. Reduced Durability & Increased Susceptibility to Damage:

* Softer Surface: Type 1L concrete tends to have a softer, more porous surface, making it more susceptible to scratches, staining, and other forms of damage.

* Increased Cracking: It may be more prone to cracking, shrinkage, and deterioration over time, especially in harsh environmental conditions or exposure to aggressive chemicals. 

* Weak and Dusty Surface: Improper curing can lead to a weak and dusty surface.

2. Finishability Issues:

* Increased Water Demand: Type 1L concrete requires more water to achieve the same slump, which can lead to challenges in achieving desired finishes.

* Lack of Bleed Water: A lack of bleed water can result in plastic shrinkage cracking, crusting, and the need for evaporation retarders.

* Delamination: Delamination of concrete surfaces can occur due to delayed bleed water.

3. Other Challenges:

* Variable Set Times: The set times of Type 1L concrete can vary depending on the limestone content and particle fineness.

* Reduced Strength (Dilution Effect): Type 1L cement can produce slightly lower compressive strengths compared to concrete made with Type I/II cement due to the reduced proportion of Ordinary Portland Cement (OPC).

* Sensitivity to Particle Size: Research indicates that Type 1L cement is highly sensitive to the particle size of the limestone after grinding.

* Material Variability: The use of Type 1L cement varies across different locations, and contractors need to be aware of the specific issues and requirements in each area.

* Requires special formulations of densifier designed to react with the excessive amounts of limestone in the mix design.

What are some of the best ways to prevent concrete surface scaling issues related to using Type 1L cement?

Dealing with surface scaling in concrete, especially when using Type 1L cement, requires a multifaceted approach.

Here's a breakdown of the best preventive measures:

1. Proper Mix Design:

  • Water-Cementitious Materials Ratio (w/cm): A low w/cm ratio is crucial. Excess water weakens the surface, making it prone to scaling. Careful control of water content is essential.  
  • Air Entrainment: Especially in freeze-thaw climates, air entrainment is vital. It creates microscopic air bubbles that relieve internal pressure caused by freezing water. Ensure proper air entrainment levels are achieved and verified.  
  • Aggregate Selection: Use durable, well-graded aggregates. Ensure they are clean and free of contaminants.
  • Admixture Compatibility: Work closely with admixture suppliers to ensure compatibility with Type 1L cement. Adjust dosages as needed.

2. Finishing Practices:

  • Timing: Avoid premature finishing. Wait until bleed water has evaporated before finishing. Overworking the surface while bleed water is present weakens it.  
  • Proper Techniques: Use appropriate finishing tools and techniques. Avoid over-finishing, which can trap water at the surface.

3. Curing:

  • Adequate Curing: Proper curing is paramount. 
  • Maintain adequate moisture and temperature for the required curing period. This allows the concrete to gain strength and durability.   
  •  Methods include: Using curing compounds. Covering with plastic sheeting. Keeping the surface wet.
  • Curing timing: Begin curing as soon as possible after the finishing process is complete.

4. Protection:

  • Deicing Salts: Minimize exposure to deicing salts, especially during the first year. If used, opt for less aggressive options.  
  • Sealants: Apply a high-quality penetrating sealer to protect the concrete surface from moisture and deicing salts. Silane sealers are often recommended.

5. Additional Considerations:

  • Early Engagement: Communicate with ready-mix suppliers and contractors early in the project to discuss the specific characteristics of Type 1L concrete.
  • Quality Control: Implement strict quality control measures throughout the construction process, from mix design to placement and curing.

in conclusion:

The shift from Type 1 to Type 1L cement represents a significant step towards a more sustainable construction industry, primarily driven by the need to reduce carbon emissions.

While Type 1L offers substantial environmental benefits, it introduces potential challenges related to surface characteristics, water demand, and setting times.

However, by implementing careful mix design, proper finishing and curing techniques, and diligent quality control, these challenges can be effectively mitigated.

Ultimately, the successful adoption of Type 1L cement requires a collaborative effort between cement producers, ready-mix companies, and contractors to ensure durable and sustainable concrete structures.

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