In terms of cement-based dry mixtures produced for structure chemicals, cement is important as are other inputs. Many minor inputs such as polymers, celluloses, water-repelling agents, plasticizers, etc. contribute to the performance of the mixture and help to create durable mortars.
One of the most important additives of this kind is cellulose ether and it is used in many areas such as construction materials, paint and trim industry, food, pharmaceutical, cosmetics, etc.
In the first part of this post, we will give information about cellulose ethers and cement systems as well as their working mechanisms. And in the second part of this post, we will comment on various cement types and the effect of different cellulose ethers on the performance of the mixture through experimental methods.
What is Cellulose? What are the types of Cellulose Ether?
As an organic compound, cellulose is a carbohydrate consisting of hundreds of molecules bonding with each other to make a chain. There are various types of cellulose ethers used in cement-based construction chemicals materials such as hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), hydroxyethyl methylcellulose (HEMC), hydroxyethyl cellulose (HEC).
- Hydroxypropyl methylcellulose (HPMC) may be used in construction materials, trim materials, ceramic industry, and general chemistry industry. It is an odorless, white, and non-toxic powder. It has various properties such as film forming, moisture holding, protecting and absorption.
Figure 1. HPMC structure
- Hydroxyethyl methylcellulose (HEMC) has similar properties with other methylcelluloses such as thickening and water retention. Ceramic adhesives are preferred in plasters and some paint materials.
Figure 2. HEMC structure
What are the effects of Cellulose Ether on Adhesives?
Cellulose ethers have effects on various properties of adhesives such as;
- Viscosity,
- Air gap stabilization,
- Water retention,
- Workability,
- Open time,
- Adhesion to the substrate.
Cellulose ethers hold mixture water with increased viscosity and prevent the substrate to absorb mixture water as it gives the mortar the ability of water retention.
Figure 3: Water retention property of cellulose ethers within the mixture
Hydration continues when there is no water loss, and the mortar would not suffer from strength loss. However, water retention slows down hydration reactions. Many literature studies show that water retention property of the mortar increases with the cellulose amount. Moreover, they also show that increase in molecule weight or viscosity of HEMC leads to increase in water retention capacity of the mortar. However, changes in cement properties also influence water retention performance. The water retention capacity of the mortar may be calculated according to ASTM C 1506 standard.
Characterization of Cement Types and Cellulose Ether Used
Thanks to its customer-focused approach, Çimsa is aware of the importance of workability and open waiting periods of mortars which are important parameters in the construction chemicals sector. Special solutions are offered for the construction chemicals sector through segment-based cement production. In this study, we aimed to analyze the interaction between different cellulose ether types and different cements. In line with this purpose, we examined the performances of ceramic adhesives prepared using 4 different cements and 4 different cellulose ethers.
As part of the study, CEM I 52.5 Super White, CEM I 52.5 Motiva Slow, CEM II 42.5 Eco White and CEM I 42.5 Gray cement found in the Çimsa portfolio were used.
Four separate hydroxyethyl methyl celluloses with different viscosity properties and modifications were used as part of the study. Viscosity and modification properties of the utilized celluloses are presented in Table 1.
Table 1. Viscosity Values of Cellulose Ethers.
Water retention, slip resistance and open time properties of the cellulose ethers utilized in the study which have effects on the performance of the mortar are presented in Tablo 2.
Table 2. Performance Properties of Cellulose Ethers
Performances of cements utilized in the study were tested at Formülhane, Çimsa’s R&D Center. For each cement, the following tests were conducted; setting time, XRD-Rietveld, XRF, particle size distribution (PSD), Blaine test, strength, and water demand.
- According to XRD analysis results, the cement with highest Alite value was Motiva Slow, followed by Super white cement. Eco white cement had higher calcite amounts as a blended cement.
- Particle size distribution and fineness values can be seen in Table 3.
Table 3. Physical Properties of Cements
When physical, chemical and phase analyses of utilized cements are examined, cements with the highest setting start times were B3>G1>B2>B in that order.
We observe that cement setting times are influenced by optimum particle distribution, cement phases and chemical properties alongside the Blaine value.
What are the Effects of Cellulose Ether Types on White Cement Based Ceramic Adhesives?
We identified 4 separate cellulose ethers and cements to see the effects of cellulose ethers on different cement types in this post. We analyzed the properties of cellulose and cement types utilized in this study. In the following part of our post, we will create recipe designs for ceramic adhesive mortars and assess performances of white cement based ceramic adhesives.
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