White Cement Based Ceramic Adhesives and Cellulose Ether II

In the first part of our article, we explained the properties of cellulose ether, its usage in cement-based mortars and water retention mechanism. We examined the characteristics of both cellulose ethers and cement types in order to see the interaction of cellulose ether types with different cements. We compared different cement types in physical, chemical, mechanical, and mineralogical terms.  In this part of our article, we will use experimental methods to explain the effects of cement types and cellulose ethers on ceramic adhesives on which cellulose ethers are frequently used in the construction chemicals sector.

Ceramic Adhesive Tests with Different Cement Types

In the construction chemicals sector, ceramic adhesive mortars are used with different cement types and modified ceramic adhesives. The sizes of the ceramic to be used and the application conditions of the mortar create a need for ceramic mortars with different standards. A standard cement and aggregate percentage were determined to be tested with different cement types in this study. Cellulose amount required for the mortar to reach a stable consistency using a fixed amount of water was determined with the purpose of understanding the effect of cellulose ether.

The following tests were conducted for the mixtures prepared with each cement type.

• Consistency
• Skid Resistance
• Fast Open Waiting Test 
• Setting Time
• Flexural and Compressive Strength Tests

What are the effects of Cellulose Ether on Adhesives?

Initial tests were conducted in order to determine the water and cellulose amount to be used for each cement type. Mortar propagation tests were done with increasing cellulose amount using a fixed amount of water. It was observed that mortar’s propagation decreases as cellulose ether amount increases at a fixed water/cement rate. Following pre-tests, a standard recipe was created for the ceramic adhesive mortar. (Table 1).

Figure 1. Open Waiting Time Tests with Grey Cement

Figure 2. Open Waiting Time Tests with White Cement

Water retention capacities of ceramic adhesives were measured with cellulose ether and cement types with different viscosity and modifications.

The best water retention capacity was obtained with SE1 in the mixture prepared with grey cement;

The best water retention capacity was obtained with SE1 and SE2 in the mixture prepared with Eco White.

The best water retention capacity was obtained with SE3 and SE2 in the mixture prepared with Super White. 

Water retention capacities of the mixtures prepared with Motiva Slow had the highest values among all cellulose ether types.

Initial setting and final setting tests were conducted for each ceramic adhesive mixture. Cellulose ethers caused retardation in setting times in all tested ceramic adhesives.

What are the Effects of Cellulose Ether Types on White Cement Based Ceramic Adhesives?

Mixtures were prepared with all cement and cellulose types as part of the study. 30% cement and 70% silica sand were used in the mixture.

The effects of mortars prepared using a fixed amount of water on the performance were examined to understand the effects of cellulose ethers on each cement.

Results and Assessment

Cellulose ethers increase viscosities, workability, open time, water retention and adhesion capacities of ceramic adhesives.

Cellulose ethers prevent the mortar from losing the water required for hydration thanks to their water retention capabilities. Therefore, they cause retardation in hydration time. Fast open waiting tests were conducted before testing different cement types in the study and 0.25% cellulose ether percentage was found to be the optimum amount for a recipe at a fixed consistency (170±10 mm). The results of tests showed that;

• Mortar’s propagation decreases as cellulose ether amount increases at a fixed water/cement rate,
• Fast open time values are lower in mortars prepared with low viscosity cellulose ethers compared to the mortars prepared with high viscosity cellulose ethers,
• At a fixed consistency of 170±10 mm, water demand of the mortar increases as SE viscosity increases,
• At a fixed consistency of 170±10 mm, water demand of the mortar increases as SE modification increases,
• Water retention values increase as SE ether’s viscosity or modification increase.        

According to Tensile Adhesive standard (0.5 N/mm² ) and open time standard (EN 1346), the best performing cement was found to be Motiva Slow, and this result was confirmed through fast open time tests as well. This study showed that cement parameters are as important as used additives in the performance of cement-based mortars, especially parameters such as water retention and workability.

References:

• Standard Test Method for Water Retention of Hydraulic Cement-Based Mortars and Plasters
• White Cement Based Ceramic Adhesives and Cellulose Ether