Dr SB Hegde highlights how AdoCem® WE++ grinding aid improves cement fineness and reduces water demand, effectively minimising slump loss and enhancing concrete workability retention. The study confirms its role in improving both slump retention and compressive strength over time.
In the production of concrete, maintaining consistent workability is crucial for efficient mixing, transporting, and placing of the material. However, concrete slump loss, or the reduction in workability over time, is a common challenge, particularly in large-scale projects where the concrete mix needs to remain workable for extended periods, such as during long-distance transportation or complex placements. Slump loss greater than 150 mm within 3 hours can lead to difficulties in handling and finishing, impacting both the quality and the efficiency of construction.
One effective solution to control slump loss is the use of grinding aids during the cement production process. This technical note focuses on the application of AdoCem® WE++ grinding aid during the cement grinding of Ordinary Portland Cement (OPC) to resolve slump loss issues and improve concrete workability retention.
The role of AdoCem® WE++ grinding aid
AdoCem® WE++ is a high-performance grinding aid designed to improve the efficiency of cement grinding by reducing the energy required to achieve a desired fineness. It works by modifying the surface properties of cement particles, reducing agglomeration, and improving the flowability of the material. As a result, it enhances the production process, reduces specific energy consumption, and improves the overall quality of the cement.
In addition to its primary function in cement grinding, AdoCem® WE++ has been shown to have beneficial effects on the physical properties of the cement, particularly in terms of workability and water demand in concrete mixes. By optimising the cement particle size distribution, the grinding aid can reduce water requirements, resulting in better workability retention and lower slump loss over time.
Slump loss problem in concrete
Concrete slump loss is a significant issue
that affects the workability of fresh concrete. Over time, fresh concrete tends to lose its fluidity, which can lead to challenges in handling and placing the mix. The rate of slump loss is influenced by several factors, including:
- Cement fineness: Finer cement particles tend to absorb more water, requiring higher water-to-cement ratios to maintain a constant slump. This leads to increased slump loss.
- Cement composition: The chemical composition and particle size distribution of the cement affect hydration rates and, consequently, the workability over time.
- Environmental conditions: Temperature, humidity, and mixing conditions also play a critical role in slump retention.
In this context, the introduction of AdoCem® WE++ grinding aid helps optimise cement properties, ensuring that the water demand is minimised and workability is better maintained over an extended period, thereby mitigating slump loss.
Research methodology 4.1 Materials
- Cement: Ordinary Portland Cement (OPC) was used in this study.
- Grinding aid: AdoCem® WE++ was used as the grinding aid, added at dosages of 0.06 per cent, 0.08 per cent, and 0.10 per cent by weight of cement.
- Concrete mix: A standard concrete mix with a water-to-cement ratio of 0.50 was prepared. The target slump was 150 mm, with slump loss measurements taken at intervals up to 3 hours.
4.2 Experimental setup
- Cement grinding: OPC was ground in a ball mill, with the addition of AdoCem® WE++ at the specified dosages. The energy consumption, fineness, and particle size distribution of the cement were analysed.
- Concrete mix preparation: Concrete was mixed using cement treated with AdoCem® WE++ grinding aid, along with conventional mixing procedures.
- Slump testing: Slump was measured using the standard slump cone test at 0, 30, 60, 90, and 180 minutes after mixing to determine the rate of slump loss.
- Compressive strength: Concrete cubes (150 mm x 150 mm) were cast, cured, and tested at 7, 28, and 90 days to assess the impact of grinding aids on strength development.
Results and discussion
5.1 Cement fineness and energy consumption
The use of AdoCem® WE++ significantly improved the grinding efficiency, resulting in a more uniform particle size distribution. The cement treated with AdoCem® WE++ showed a Blaine fineness of 320 m²/kg, compared to 300 m²/kg for the control cement, indicating that the grinding aid allowed for finer grinding without increasing energy consumption. This reduced the production costs while improving cement quality.
5.2 Slump retention
The main focus of this study was to evaluate the effect of AdoCem® WE++ on slump retention. Concrete mixes with grinding aid-treated cement showed a notable improvement in slump retention over time compared to the control mix.
- Control cement (no grinding aid): The control mix experienced a slump loss of 80 mm after
2 hours.
- AdoCem® WE++ at 0.06 per cent dosage: Concrete with cement treated with 0.06 per cent AdoCem® WE++ showed a slump loss of 100 mm after 3 hours, a significant improvement over the control mix.
- AdoCem® WE++ at 0.08 per cent dosage: At a dosage of 0.08 per cent, the slump loss was reduced to 120 mm after 3 hours, demonstrating further improvement.
- AdoCem® WE++ at 0.10 per cent dosage: The highest dosage of AdoCem® WE++ resulted in the best performance, with only a 150 mm slump loss after 3 hours, which meets the target of maintaining workability over extended periods.
5.3 Hydration behaviour and setting time
The addition of AdoCem® WE++ appeared to slightly delay the initial setting time compared to the control mix. This delay in setting time helps to extend the period during which the concrete remains workable, thereby reducing the risk of excessive slump loss. The improved hydration behaviour
also contributed to better overall consistency in the concrete mix.
5.4 Compressive strength
Concrete cubes made with cement treated by AdoCem® WE++ exhibited slightly higher compressive strength compared to the control mix. At 28 days, the compressive strength of the AdoCem® WE++ mixes were 5 per cent to 8 per cent higher, indicating that the grinding aid not only improved workability but also contributed to more efficient cement hydration and stronger concrete.
Conclusion
The addition of AdoCem® WE++ grinding aid during the cement grinding process significantly improves the workability retention of concrete, effectively maintaining slump loss over a 3-hour period. By optimising the particle size distribution of cement, AdoCem® WE++ reduces water demand and enhances the stability of the concrete mix, thereby ensuring that the slump remains within the desired range (150 mm) for an extended period. Furthermore, the grinding aid improves cement efficiency, reduces energy consumption during grinding, and enhances the strength development of concrete.
This study demonstrates that AdoCem® WE++ is an effective solution for mitigating concrete slump loss, making it a valuable tool for construction projects where concrete workability must be maintained over longer periods. The optimal dosage of AdoCem® WE++ for achieving the best performance in terms of slump retention and strength is around 0.1 per cent by weight of cement.
About the author:
Dr SB Hegde, a global cement industry leader with over 30 years of experience, is a Professor at Jain College of Engineering, India, and a Visiting Professor at Pennsylvania State University, USA.
