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The tile industry has been steadily moving towards larger tiles for faster installation. The Azelis Laboratory took on a challenge to make a cement tile adhesive (CTA) that could hold a very large and heavy stone veneer tile that needed to be applied vertically with no sag. It also needed to pass the national standard for high performance tile adhesive, ANSI 118.15.

The final mortar formulated by the Azelis Americas Construction Solutions Chemists was smooth and easy to trowel, which is always an important feature for applicators in the field. When the stone veneer tile was subjected to the ANSI sag test, virtually zero sag was observed.

In addition to passing the sag requirement, this mortar also passed all the strength testing requirements in ANSI 118.15, as well as additional compressive strength testing. The CTA had excellent long term workability and open time.

Two key additives helped us achieve the zero sag feature: Starvis® T 50 F and Starvis® RS 421/01 F

Starvis® T 50 F is a specially designed thickener based on polyacrylamide. It shows delayed thickening and enables easy mixing. This rheology additive is especially suited for sag-resistant applications.

Starvis® RS 421/01 F is a ready to use rheology modifying and water storage agent with outstanding rheological properties Suitable for demanding dry mortar applications concerning high sag resistance and water storage. Multifunctional additive that can reduce the number of additives in your formulation.

Performance Results

The formulation submitted exceeded all testing requirements.

The stone veneer tile was 30 pounds and approximately 12 x 24 inches in dimension. It was applied it to freshly troweled mortar and held vertically for 20 minutes and measured for distance sagged. The ANSI tolerance is a slim 0.5mm. The original formulation had very poor sag resistance, sliding down the mortar several inches over the course of the 20 minute test. The final formulation developed by Azelis had zero measured sag after 20 minutes, a huge improvement to the original mortar.

Physical Properties (based on performance of market material provided by customer)Result
Sag (target <0.5mm)0.0 mm
Open Time (target > 40 min)~1 hour
Density (Target >1.65 g/cc)1.72
28 day dry shear strength (target >475 psi)536
28 day freeze thaw (target >275 psi)328
28 day compressive strength (target >2400 psi)2785


Azelis Construction Solutions Lab was tasked to improve upon an existing stone veneer tile adhesive to compete with a competitive mortar currently in the market. The lab needed to match the competitive mortar’s performance in open time, set time, workability, and strength, as well as excellent sag resistant for the heavy and large stone veneer tiles provided.


The main challenges were improving sag resistance and texture. Several rheology modifying additives were utilized from the Azelis portfolio to reduce stickiness and provide excellent sag resistance, including starch ether, polyacrylamide, and polyelectrolyte.

Starvis T 50 F is an additive that provides strong sag resistance at very small dosages, in this formulation we added 0.06% Starvis T 50 F.

Starvis RS 421/01 F helps to provide workability, open time, sag resistance, and adhesion. We started testing an existing formulation and removed three ingredients and replaced them with Starvis RS 421/01 F . The original formulation was well designed but was improved with this substitution.

Other enhancements included improved wetout and workability by introducing a fast-acting superplasticizer, which made the mortar a little looser and easier to work with without adding water, as well as improved open time, provided by a higher viscosity cellulose ether. The formulation also incorporated a more compatible redispersible polymer to create stronger bonding.

Open time was improved at 20 minutes and early shear bond strength improved by 20% at a constant water dosage.

A starting point formulation for the Azelis large format tile adhesive is available from your Azelis representative, or can be requested through Chat.


Using Starvis® T 50 F, Starvis® RS 421/01 F and other products from the Azelis portfolio, the latest large format cement tile adhesive not only exceeded the strength testing requirements specified, but passed the challenging sag test on a 30 pound stone veneer tile. The end product was also a user-friendly material that was easy to trowel and work with.

Our additives allowed for an easy to use product that exceeded performance requirements. 

Ready to share in our success? Launch your next project with help from the Azelis Americas Chemists! Get innovative solutions to your everyday challenges while maintaining high quality end results.

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The information contained in this document is made without guarantee and warranty, express or implied, regarding the suitability for use, merchantability, or performance of the formulation and its ingredients in any application. It is the sole responsibility of the user of this information to determine validity, applicability, and performance of the information, formulations, and claims prior to commercialization, use, and application thereof.