Focus on Cellulose ethers

Effect of Cellulose Ether (HPMC/MHEC) on Cement Hydration

Cellulose ethers, especially hydroxypropylmethylcellulose (HPMC) and methylhydroxyethylcellulose (MHEC), have been widely used as cementitious material additives in construction applications. Known for their water-retaining properties, these materials can enhance the workability, rheology and bond strength of cementitious materials. However, their influence on cement hydration is not always clear.

Cement hydration refers to the chemical reaction between water and cementitious materials to produce hydration products such as calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)2). This process is critical to the development of concrete’s mechanical strength and durability.

The addition of cellulose ethers to cementitious materials can have both positive and negative effects on the hydration process. On the one hand, the water retention performance of cellulose ether can promote the cement to continuously obtain water for reaction, thereby increasing the speed and degree of hydration. This shortens setting time, accelerates strength development and improves the overall properties of the concrete.

Cellulose ether can also act as a protective colloid to prevent the aggregation and settlement of cement particles. This results in a more uniform and stable microstructure, which further enhances the mechanical and durable properties of concrete.

On the other hand, excessive use of cellulose ethers can negatively affect cement hydration. Because cellulose ether is partially hydrophobic, it blocks the ingress of water into the gelling material, resulting in delayed or incomplete hydration. This results in a reduction in the strength and durability of the concrete.

If the concentration of cellulose ether is too high, it will occupy the space in the cement slurry that should be filled by cement particles. As a result, the total solids content of the slurry will decrease, resulting in reduced mechanical properties. Excess cellulose ethers can also act as a barrier, preventing the interaction between cement particles and water, further slowing down the hydration process.

It is crucial to determine the optimal amount of cellulose ether to use to improve the properties of the gelled material while avoiding any negative impact on hydration. The amount depends on many factors, such as the type of cellulose ether, cement composition, water-cement ratio and curing conditions.

Cellulose ethers, especially HPMC and MHEC, can have a positive effect on cement hydration, depending on their concentration and the specific composition of the cementitious material. The amount of cellulose ether used must be carefully considered to achieve the desired properties without compromising the properties of the concrete. With proper use and optimization, cellulose ethers can contribute to the development of more durable, long-lasting and sustainable construction materials.

Post time: Aug-23-2023
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