HPMC-Hydroxypropyl methyl cellulose introduction
November 21st 2024
RDP develop several properties that have significant affect on the mortar mix. RDP modifies the cement in several ways. For instance, RDP improves the brittleness of conventional cement mortar. It also enhances the tensile bond strength along with its flexibility. It also decreases the risk of developing cracks on cemented surfaces.
The polymer and cement mortar form a strong matrix and creates a uniform film over the pores. It helps to strengthen the tensile bond between aggregates and can block some pores within the mortar. Once it gets hard, the RDP-mixed mortar is superior in quality to conventional cement mortar.
Here are the distinct properties that mortar or cement develop when they are made by mixing redispersible polymer powder –
Redispersible polymer powders give incredible bonding power to the mortar. The bonding strength of mortar grows directly in proportion when you add a greater amount of RDP. However, this can inversely affect the mortar’s compressive strength. This is why there is a specific amount of RDP that you can mix to improve the bonding strength of mortar mix, without compromising compressive strength.
In addition, RDP is quite expensive, and adding more of it into the mortar mix can cause the cost of construction to rise. Apart from this, a higher bond strength can have a restrictive effect on the contraction. Though the stress generated by deformation can be dispersed it is important to have greater bond strength to prevent cracks from developing.
The elastic modulus of redispersible polymer powder is lower than that of cement mortar. Hence, the elastic modulus of cement mortar gets reduced when you add extra RDP.
However, the dosage and type of polymer powder also affects the elastic modulus. In general, the risk of deformation increases in a mortar mix when the elastic modulus gets reduced and the cement-polymer ratio increases.
Redispersible polymer powder also has excellent water and alkali resistance. This provides the finished surface protection against impact and abrasion.
The polymer particles in RDP form a thin film that blocks the cracks and holes in cement mortar. This helps to reduce the porosity of hardened surfaces. In turn, this effectively improves the impermeability, making the mortar mix resistant to frost and water damage. This property can be enhanced by increasing the cement-polymer ratio in the mortar mix.
Abrasion-resistant property in the mortar is directly related to the type of polymer used in the polymer powder. Generally, abrasion resistance improves as the polymer-cement ratio increases.
The polymer mix formed after the redispersible polymer powder is mixed with water creates a continuous film of the mortar once it solidifies. This thin cover of RDP prevents migration of water. This way, RDP effectively reduces water loss from the mortar, and essentially enhances its water retention properties.
The toughness of polymer-induced cement mortar is significantly higher than that of ordinary cement mortar. Fracture-resistance power of RDP-mixed mortar cement is twice that of conventional cement mortar. Besides this, increasing the polymer-cement ratio also enhances the mortar’s toughness and ability to resist impact.
By increasing the amount of polymer powder, you can ensure good stress dispersion, and restrict the risk of developing cracks.
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