Performance Analysis of Redispersible Polymer Powder (RDP) in Tile Adhesive

The effect of RDP mixing amount on the shrinkage performance of tile adhesive 1

Compared with other wall materials and floor decoration materials, ceramic tiles have excellent advantages in cleaning, care, and durability and have become an indispensable building material in modern architecture.

With the continuous expansion of the application field of ceramic tiles and the rapid development of manufacturing technology, the quality of ceramic tiles has been greatly improved. The traditional ceramic tile pasting process can no longer meet its application requirements. For this reason, building materials manufacturers have successively introduced re-dispersible polymer powder (RDP) modified tile adhesive. Its purpose is to improve the bonding performance of ceramic tile adhesive and simplify the construction process of ceramic tile sticking. According to the experimental results, this paper analyzes RDP’s influence on the properties of ceramic tile adhesive.

  1. Material and Methods

1.1 Material

(1) Cement;

(2) Fly ash: secondary fly ash;

(3) Cellulose ether: Melacoll, viscosity about 60,000;

(4) RDP: Mikrant;

(5) Sand: dry sand and screen it into different particle sizes as required;

(6) Mixing water: tap water.

1.2 Methods

This experiment mainly investigates the tensile adhesive strength of tile adhesive after thermal aging and water immersion. The preparation, maintenance, and experimental methods of specimen items shall be carried out according to the relevant standards’ relevant provisions.

(1) The ingredients of tile adhesive powder: weigh cement, quartz sand, cellulose ethers, and other raw materials in a certain proportion, add them into a mixer, and stir them evenly.

(2) The preparation of tile adhesive: Firstly, add powdery ingredients corresponding to their water consumption into a mixing container, add corresponding experiment powdery ingredients, and thoroughly and evenly mix for 30 seconds with a mortar mixer.

  1. Result and Analysis

2.1. The influence of the dosage of RDP on the tensile adhesive strength of tile adhesive.

Table 1: RDP’s effect on the bonding strength of ceramic tile adhesive is shown in the following table.

EXPERIMENT NO.

MIXING AMOUNT OF RDP/%

ORIGINAL ADHESIVE STRENGTH OF RDP/MPa

WATER IMMERSION STRENGTH/MPa

THERMAL AGING STRENGTH/MPa

1

1.5

1.15

0.81

0.52

2

3

1.13

0.84

0.67

2

4.5

1.24

0.85

0.75

 

From Table 1, the strength of cement-based tile adhesive after soaking in water and the strength after the thermal ageing show an increasing trend with the increase of RDP dosage. Among them, the most apparent increasing trend is thermal ageing performance. The reason is that the flexibility of tile adhesive increases with the increase of RDP (while the amount of other raw materials remains unchanged). The damage caused by the corresponding force change at high temperature to the bonding performance of tile adhesive is reduced, manifested by the improvement of bonding performance, and directly reflected by the increase of bonding tensile strength after thermal ageing shown in Figure 2-1. The van der Waals force at the interface between tile adhesive and ceramic tile is destroyed by water entry after immersion. In general, keeping the mixture ratio of other raw materials unchanged and adding RDP, the paste’s viscosity decreases to a certain extent. Increasing the dosage of RDP will reduce the thickness of the tile paste. Improving the compactness of tile adhesive makes it difficult for water to enter the interior of tile adhesive, and the failure trend of van der Waals force slows down, which can improve the tensile bonding properties of ceramic tile adhesive after soaking in water. As mentioned above, the tensile adhesive strength of tile adhesive after soaking in water and after thermal ageing will increase with the mixing amount of RDP. This phenomenon may be due to the closer relationship between the thermal ageing resistance and flexibility of tile adhesive for the remarkable improvement of ageing resistance. The flexibility of RDP and tile adhesive is directly related. Considering the properties and price of tile adhesive, the best dosage of RDP is 3%.

 

2.2 The effect of RDP on the shrinkage of ceramic tile is shown below.

The effect of RDP mixing amount on the shrinkage performance of tile adhesive

Figure 1: The effect of RDP mixing amount on the shrinkage performance of tile adhesive

From Figure 1, the shrinkage value of ceramic tile adhesive will increase with the increase of age.

Before the 10-day age, the shrinkage value increased significantly. After ten days, the shrinkage deformation will slow down. The change of shrinkage value of ceramic tile adhesive is closely related to the action mechanism of raw materials in ceramic tile adhesive. As a mixed material with potential hydraulic activity, fly ash has poor early chemical reaction ability and low particle surface energy. Water between fly ash particles is quickly evaporated and lost. However, cement is in a “severe” hydration period at this stage, and the increase of early shrinkage is relatively significant. With curing age development, under the excitation of Ca(OH) released from cement hydration, fly ash undergoes secondary hydration. The structure of ceramic tile adhesive becomes denser, the strength is greatly improved, and the shrinkage deformation of ceramic tile adhesive will slow down. From Figure 1, the shrinkage deformation value of ceramic tile adhesive will increase with the increase of the mixing amount of RDP. When the mixing amount of RDP is 5%, the shrinkage value of ceramic tile adhesive is close to 0.2%. The reason may be that the incorporation of RDP improves the flexibility of cement-based ceramic tile adhesive. With the increase of RDP’s mixing amount, the rigidity of ceramic tile adhesive will decrease, the flexibility will increase, and the resistance of ceramic tile adhesive to shrinkage deformation will decrease, which will lead to the increase of shrinkage value of ceramic tile adhesive.

2.3. The influence of the mixing amount of RDP on the lateral deformation of tile adhesive is shown below.

The effect of the mixing amount of RDP on the lateral deformation of tile adhesive

Figure 2: The effect of the mixing amount of RDP on the lateral deformation of  tile adhesive

From Figure 2, we can see that RDP has a great influence on the lateral deformation ability of tile adhesive. The lateral deformation value of tile adhesive will increase with the mixing amount of RDP. When the mixing amount of RDP is 2%, its lateral deformation will be greater than 2.5mm, which can meet the S1 grade adhesive standard requirements. When the mixing amount of RDP is less than 4%, its lateral deformation can reach more than 5.0mm, which can meet the S2 grade adhesive standard requirements. The reason is that with the increase of the mixing amount of RDP, the slurry viscosity of tile adhesive will decrease slightly, its compactness will increase, its bonding strength will increase, and its anti-cracking ability will also increase. The RDP has a better increase in toughness, so the lateral deformation ability of tile adhesive increases.

  1. Conclusion:

(1) The RDP has a significant influence on the bonding strength of cement-based tile adhesive. With the increase of RDP mixing, the water resistance and ageing resistance of tile adhesive will increase. Among them, the rise in ageing resistance is remarkable.

(2) The shrinkage value of tile adhesive will increase with the addition of RDP. But the incorporation of RDP is beneficial to the overall performance of ceramic tile adhesive.

(3)  The addition of RDP can improve the lateral deformation ability of cement-based tile adhesive. When the mixing amount of RDP is 2%, its lateral deformation can meet the requirements of the S1 grade of the adhesive standard; When the mixing amount of RDP is more than 4%, its lateral deformation can meet the S2 grade adhesive standard requirements.

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