Laviosa Bentonite Rheological Additives for Water-Based Systems in the Construction Sector

Laviosa Chimica Mineraria Spa is one of the world's leading manufacturers of bentonite-based rheological additives.

Our core business is to research bentonite and other clay minerals and ensure their conversion into high-value-added ideas and solutions. Our strength comes from raw material control, process technology, our production facilities in different regions of the world, product application expertise, logistics support and customer-focused approach. As Laviosa, we have a portfolio of more than 1500 customers in over 80 countries worldwide.

What is Bentonite?

Bentonite, commonly known as such, is a special clay mineral belonging to the smectite group, also called Montmorillonite. Montmorillonite is an aluminium hydrosilicate that morphologically consists of an alumina octahedron layer sandwiched between two silica tetrahedral layers. In the octahedral layer, aluminium can be substituted by magnesium, which creates an excess negative charge. The excess negative charge is compensated by different mono and bivalent cations. (Ca, Mg, Na..) This typical crystal structure gives the simple montmorillonite particle the flat particle shape we call a platelet. These "platelets" are held together by Van der Waals forces; however, they disperse in water as sub-micron particles, which creates a surface area of an impressive value such as 800 m²/g. A montmorillonite platelet carries extensive negative charge on its surface and very small positive charge on its edges. LAVIOTHIX® and LAVIOKOLL® are high-performance and effective clay-based inorganic products that impart high pseudoplastic and thixotropic behaviour particularly to water-based formulations. These products are thickeners and anti-settling agents based on specially selected, purified and activated bentonite clay containing high montmorillonite content. Activation is entirely related to its hydration capacity and ensures the dispersion of micron and sub-micron particles. They help form the body of the formulated product through the formation of a three-dimensional internal structure in which different particles and fillers can come together. These basic particles are responsible for the product's thixotropy, anti-settling, absorptive and binding properties.

Key Properties and Application in the Construction Sector

In building systems such as mortars, plasters, ground systems and construction adhesives, spread control is very important, and in these systems cellulose ether is the main additive used to provide thickening and water-retention properties. However, system performance and application properties can be significantly improved by using clay-based thickeners together with cellulose ether. Clay can be used in many different systems in the construction sector to modify spread and application properties.

Properties and Performance

The aggregated network of bentonite clay imparts thixotropic flow properties. At low shear rates, the clay network creates high viscosity. When shear force is applied, whether through mixing, pumping or trowelling, the network breaks down in all cases and viscosity decreases to allow easy application. When the shear force is removed, the flat particles (platelets) return to their original aggregated network structure and viscosity increases over time. This is typical thixotropic behaviour; each flat clay particle reduces friction between sand and fillers, which facilitates trowelling or smoothing application and also reduces pumping pressure.

Yield Value

In construction products and other systems, a strong network formation is used both to modify spread behaviour and to control sedimentation of solid particles and flow on vertical surfaces. This performance is expressed rheologically as yield value. Yield Value is the minimum shear stress applied to provide fluidity. Compared to cellulose ether, which does not have a significant yield value, bentonite clay creates a network with high yield value, which provides flow and sedimentation resistance, controlling settling and bleeding.

Shear Effect

Flat clay particles reduce the stickiness that occurs on application tools caused by cellulose ether or powder polymer; thereby improving properties such as application speed and surface quality. In building systems such as mortars, plasters, ground systems and construction adhesives, spread control is very important to achieve optimum thickening and water-retention properties. The use of bentonite rheological additives can significantly improve the performance and application properties of building systems.

Properties to be Improved

Easy workability and convenient use of application tools • Flow resistance, • Anti-settling properties, • Storage stability, • Bleeding prevention. The network-forming property of bentonite modifies spread behaviour, controls flow on vertical surfaces and reduces sedimentation of solid particles. Flat particles act as lubricants by reducing friction between sand and cement particles and reduce the stickiness on application tools caused by cellulose ether. For more detailed technical information and sample requests, please contact our Turkey representative Turkuaz Kimya. Author: Elena Menicagli / Product Manager / Laviosa Chimica Mineraria SpA Translator: Füsun Özkamışlı / Director / Turkuaz Kimya ve Tarım San.Tic. A.Ş.