KEY INSIGHTS

Ceramic tiles find application in construction sector both indoors and outdoors. The system consists of ceramic tiles, ceramic tile adhesive (CTA), tile grout and the substrate. Various factors affect the interfacial layers of this system that could lead to adhesion failure. The presented conversation allows to create an easy bridge for formulating CTA by understanding the technical details by learning about the core ingredients. Lastly, a few formulations have been provided as obtained from the published papers.

BULLET POINTS

• The presented conversation provides introduction to tile adhesives.
• The ingredients of tile adhesive, its role along with a few examples of each have been mentioned.
• Lastly, a few tile adhesive formulations, as obtained during the literature survey, have been presented.

KEYWORDS

Ceramic Tile Adhesive, Binders, Aggregates, Additives, Tile adhesive formulations

DETAILED REPORT

Ceramic tiles are used indoors and outdoors for various applications like cladding, flooring and swimming pools. Typically fixed with a polymer-modified cementitious adhesive mortar to the substrate, e.g. concrete, their performance is affected by the climatic conditions like moisture, temperature, etc. They may also vary within a tiling especially in the case of large tiles, from rim to centre of the individual tile. The local conditions cause moisture and hydration gradients across and parallel to the mortar bed. The gradients influence the thermal shrinkage and expansion behaviour, initiating micro-cracks preferentially at the edges of the tiles, where the highest shear stresses between tile and adhesive mortar occur potentially leading to partial delamination or complete loss of adhesion. Especially in exterior application, stresses induced by the weathering conditions may cause a more rapid progress of failure development [1]. If the bond strength is sufficient, the tendency of this differential movements may get constrained, causing high stress built up those later damages the system at weaker points. This leads to disintegration of the system causing tile falling, tile cracking, tile buckling and tile staining[2].

Thus the modern ceramic tile adhesive (CTA) demands the judicious selection of its components added in optimum proportions to maximise the overall performance. A CTA may contain a dozen of ingredients. These ingredients can be classified as binders both mineral and polymer based, aggregates, and additives. In order to design high performance tile adhesives the interactions between all the components, the adhesion mechanisms between the adhesive and the substrate and the effect of various additives should be recognized. Other parameters that influence interfacial strength includes ceramic tile water absorption, installation process, and water-to-cement ratio, the method of mixing, implementation and curing conditions [3].

The following table gives the list of additives along with its function in the CTA and a few examples. The numbers or the range provided in the parenthesis denotes the amount of each ingredient to be added in CTA and is obtained from the literature. The required properties of CTA may demand the employment of one or more kind of each additive. At the end of this conversation we present a few example of CTA formulations employed in the literature.

Additives	Role and examples	Reference
Binders	It binds all the ingredients together.   Examples: Portland pozzolan cement, Portland cement, and high-alumina cement, sulfoaluminate cement, hydrated lime gypsum	[4–6]
Aggregates/ fillers	Serve as reinforcing and structural element, increasing the strength of the CTA. Generally aggregates ensure the packing density, flexural strength and durability. Examples: Sand, Quartz fillers with quartz sand granulation in the range of 0.05-0.5 mm. (45-70%), Limestone, hydrated lime, Clay (0.9%), fly ash (5%), silica sand (1.63%), Diatomite sand, aluminosilicate microspheres, Tripoli powder. Pozzolanic fillers like Rice husk ash (20%) and corn husk ash (15%), low lime fly ash (5%)	[2,4–10]
Plasticizers, dispersants or water reducing agents	Also known as water reducing agents or water reducersDisperse binder particles and increase the fluidity of the binder.Plasticizers help reduce the water/cement ratio by 5-10% thus reducing the total porosity of concrete.The reduction in the amount of water benefits durability and workability and shrinkage reduction. Examples: Melamine-based agents, lignin-based agents, and poly carboxylate based compounds	[3,11]
Superplasticizers	Superplasticizers reduces the water/cement ratio by 25%.  Increases the fluidity of the mortar and opening time and also has a positive effect on the mechanical strength of the adhesive.The efficiency of superplasticizer depends on functional group, number and density of the adsorbing groups and the length of the side-chain, as well as grafting density.Improves the tensile adhesion strength of the adhesive. Examples: Major classes of superplasticizers include lignosulfates, sulfonates, naphthanates, melamine sulfonates and polycarboxylates. Polycarboxylate ethers (0-0.2%), sulfonated naphthalene formaldehyde (0-1%), sulfonated melamine formaldehyde	[3,9,11–13]
Accelerators	Increase the rate of cement hydration and reduce setting time and hardening, consequently increasing the strength of the adhesive in lesser duration. Raises flow of mixture even in small amount of water present, raises adhesion, accelerates mixture spillage, and lowers self-shrinkage deformation. Examples: Calcium formate (<1-2%), calcium carbonate, silica sand. Organic additives such as diethanolamine, triethanolamine, propionate, glyoxal, urea, and formate are used. Inorganic additives mostly consist of fluorides, aluminates, borates, silicates, nitrites, chlorides, and others.	[2,3,6,14]
Redispersible polymer powders (RPP)	The actual performance depends on the concentration and type of RPP used. In general it enhances the adhesive properties, workability, water retention capability, waterproofing abilities, durability (imparting slip and impact resistance to prevent formation of cracks), and increase flexibility by modifying its elastic modulus, and malleability i.e. fresh mortar rheology.The higher the polymer content the higher is the flexibility but lower the compressive strength. Generally, the lower the Tg of RPP, the lower the Young’s Modulus of the mortar.Enhances the qualities such as plasticity, tensile strength, flexural strength, and resistance to abrasion.Flexural strength increases with increasing latex incorporation due to latex polymer film bridge micro-cracks and reduce their propagation during tensile loading.The polymeric film formed, seals off crevices and pores which boosts the mortar’s water retention capacity. The film closes the pores and cracks of the hardened mortar, preventing water evaporation. It also improves the impermeability to substances as water and alkali.Water quickly evaporates from the adhesive’s surface in fresh mortar. A thin layer of polymer is formed within few minutes, preventing further evaporation.The volume of porosity, average pore diameter and mean sphericity of pores are affected by the type of RPP being used. Examples: Styrene Butadiene Rubber (0-25%), Poly (ethylene-vinyl acetate) (0-20%), Poly (vinyl acetate-vinyl versatate) (0-20%), Poly (styrene-acrylic ester) (0-20%), Copolymer of ethylene-vinyl acetate-vinyl ester, Terpolymer of ethylene-vinyl chloride-vinyl laurate (10%), Acrylate copolymer, Terpolymer of vinyl acetate-ethylene-vinyl ester of versatic acid (10%), Siloxane based RPP (0.117-0.75%)	[3–6,11,13,15–26]
Water soluble polymers (WSP)	The performance of water soluble polymers depends on the type (degree of substitution (DS), molar substitution (MS), degree of polymerization and molecular weight), concentration and combination of the polymers employed. The lower the DS or MS, the greater the retardation impact on cement hydration.Improves concrete construction by improving cohesion thus reducing crack formation. It improves workability, durability, flow properties. It helps to reduce shrinkage (Hydroxy ethyl methyl cellulose (HEMC) and polyethylene glycol (PEG) reduces shrinkage. The higher the molecular weight of PEG the better the efficiency. In case of polypropylene glycol (PPG), the lower the molecular weight the better.)It improves water retention by preventing its evaporation leading to better cement hydration, thus enhancing material flexibility and strength. The selection of water soluble polymer is critical to control skin formation in order to obtain the desirable wettability to the tile (i.e.. open time). Skinning is essential to prevent surface drying of the mortar ridges applied on to a concrete slab, but skin control is also indispensable as: (a) A too thin skin that dissolves permits surface evaporation and, hence, local decohesion of the matter. (b) A too thick skin due to high residual CE concentration in the pore solution does not allow local remixing of the matter while tiling, with dissolution of the cellulose ether film into the mortar.WSP alters cement microstructure and characteristics, resulting in increased air void contents, reduced mass density, decreased viscosity, and diminished porous interfacial transition zones.Air entrapment protects concrete against freezing and thawing. Carbonation process may be effectively delayed by using cellulose ether. Chloride ions can cause corrosion in concrete, affecting steel reinforcement. The use of PEG improves the grout’s potential to bind chloride, due to the development of hydrogen links between PEG and chloride ions. It is reported that using 5% PEG lowers the diffusion coefficient by 30% after 28 days.The use of WSP beyond the optimum level retards the cement hydration process. This delay seemed to depend mainly on the chemical structure of the molecule and in particular, on the degree of substitution. In case of cellulose ether (CE) the lower the content of methoxyl groups, the larger will be the retardation of cement setting time. The increase in CE dose, the longer the setting time of mortar. It also causes a greater decrease in the rate of heat evolved during the acceleration period as well as the peak heat value.The use of oxalic acid in CE-modified mortar enhances the strength.The higher the CE content, the greater the chemical resistance of the mortar. In some applications, the mortar are subjected to contact with chemicals. For example, tile adhesives that are used for swimming pools come into regular contact with sanitary chemicals.Incorporation of CE improves mechanical strength up to a certain level. The enhancement in mechanical strength due to better cohesion of microstructure is greater than the degradation due to retardation of cement hydration and air entrainment.In order to mitigate the negative impact of CE, addition of additives (such as accelerators and defoamers) is required. Examples: Cellulose ethers like Methylcellulose (MC) derivative (Culminal_ 4051) (0.5-1%), hydroxy ethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl guars (HPG) and hydroxy ethyl cellulose (HEC), Polyvinyl alcohol (up to 2%)	[6,11,12,27,28]
Thickeners	It helps to increase the viscosity of mortar. Examples: Cellulose ether like HEC, HEMC, HPMC and MC, starch derivative, Polyvinyl alcohol (PVA), polyacrylamide (PAM), polyethylene oxide (PEO), and PEG.	[2,3,5,6,12,19,20,29–31]
Fibers	Reduce the flow value and thus the workability of fresh mortar.Hydrophilic fibers interact well with cement than hydrophobic ones. Hydrophobic can also improve properties of cement after its surface treatment.At optimum loading of fibers, both the compressive and flexural strength of cement-mortar increases. Examples: Polypropylene (0.4-1%), polyethylene (1-2.5%), polyamide (0.25-0.75%), polyvinyl alcohol (0.1-1%), polyethylene terephthalate fibers, steel and cellulose	[11,32]
Rheology modifier	This stabilizing admixture regulates marginal shear stress size and plastic mixture viscosity and doesn’t allow for water and mixture to separate into layers when the flow of mixture is too high. It also increases viscositySecure proper rheological properties including slip resistance and water retention. Examples: MC derivative (0.4-1%), HEMC, HPMC, hydroxy propyl guars (HPG) and HEC (0.6%), xanthan gum, welan gum, Starch ether (0.01-0.3%)	[12,14,17,25,26]
Water-retaining agents	Helps to retain water, reduce air entrapment. Examples: HPMC (0.2-0.5%), HEMC, PAM, PVA (<2%), MC (0.082%)	[5,6,16,19,29,30]
Retarders	It delays the setting process of cement, so extending its period of freshness before it sets.It impedes the process of cement hydration, resulting in a prolonged curing time and increased workability. It may decrease the compressive strength. Examples: Inorganic retarders such as oxides of Zinc and lead, magnesium, phosphates, salts, borates and, fluorates are commonly utilized for this purpose. On the other hand, organic retarders include Calcium, sodium, and ammonium salts of lingnosulfonic acids, as well as citric acid, gluconic acid, adipic acid, heptonic acid, carbohydrates, succinic acid, and tartaric acid.	[6,12]
Defoaming agent	It was also found that the use of defoamers helps to reduce the degradation in mechanical strengths of the CE-modified mortars by reducing air entrainment by CE addition. Examples: Tributyl phosphate, polydimethylsiloxanes. Non-soluble oils on a carrier of silica, specific alcohols, polyalkylene glycols, and stearates, polyether modified silicone	[6,13]

Example of few formulations

The following formulations are taken from the literature (references mentioned) and doesn’t claim to be the final composition. The industrial formulations are the trade secrets. However, we hope that these formulations will guide you to construct the best performing ceramic tile adhesive.

[8]
Ingredients	Wt %
Cement	32.68
Sand	49.02
Filler (silica)	1.63
Polymer emulsion	6.54
Superplasticizer	0.32
Water	13.07

[6]
Ingredients	Wt %
Cement type II-V	36.8
Siliceous sand	55.5
Calcium carbonate	5.17
Modified hydroxy ethyl methyl cellulose	0.33
Calcium formate	0.2
Redispersible polymer	2-3
Water	23

[28]
Ingredients	Wt %
Cem I 52.5 N cement	36
Silica sand	58.36
Calcium carbonate	2
Cellulose ether	0.34
Calcium formate	0.3
Redispersible polymer	3
Water/ powder	25

[33]
Ingredients	Wt %
Portland cement CEM II/C-S 32.5 N	30
Quartz sand PB150-1	58.75-66.25
Fine filler: limestone powder/ silica flour	2.5-10
Cellulose ether Berm Coll ME1000X	0.25
Polymer powder Elotex 60W	1
Water	23-24

[20]
Ingredients	Wt %
Ordinary Portland cement	35
Quartz sand	40
Carbonate powder	22.5
Cellulose ether	0.5
Redispersible powder	2
Water	25.5

REFERENCES

[1]      F. Winnefeld, J. Kaufmann, E. Hack, S. Harzer, A. Wetzel, R. Zurbriggen, Moisture induced length changes of tile adhesive mortars and their impact on adhesion strength, Constr. Build. Mater. 30 (2012) 426–438. doi:10.1016/j.conbuildmat.2011.12.023.

[2]      Ö. Andiç, K. Ramyar, Ö. Korkut, Effect of fly ash addition on the mechanical properties of tile adhesive, Constr. Build. Mater. 19 (2005) 564–569. doi:10.1016/j.conbuildmat.2004.08.007.

[3]      S. Ahmadi, R. Momeni, Effect of Composition on the Properties of Cementitious Tile Adhesive Complied with EN 12004, Iran. J. Mater. Sci. Eng. 20 (2023) 1–13. doi:10.22068/ijmse.3391.

[4]      N. Tarannum, K. Pooja, R. Khan, Preparation and applications of hydrophobic multicomponent based redispersible polymer powder: A review, Constr. Build. Mater. 247 (2020) 118579. doi:10.1016/j.conbuildmat.2020.118579.

[5]      J. Michalak, Ceramic tile adhesives from the producer’s perspective: A literature review, Ceramics. 4 (2021) 378–390. doi:10.3390/ceramics4030027.

[6]      H. Kareem, Z.K.M. Al-Obad, Effect of Adding Redispersible Polymer Powder to Cementitious Tile Adhesive: A Literature Review, Ann. Chim. Sci. Des Mater. 48 (2024) 585–594. doi:10.18280/acsm.480415.

[7]      R. Ahumada, H. Ospina-Mateus, K. Salas-Navarro, Use of the rice and corn husk ashes as an innovative pozzolanic material in ceramic tile adhesive production, Procedia Comput. Sci. 198 (2022) 572–577. doi:10.1016/j.procs.2021.12.288.

[8]      R.P. Ribeiro, S.T.F. Moreiras, V.J. dos S. Baldan, G. de C. Xavier, S.N. Monteiro, A.R.G. de Azevedo, Relationships between the surface roughness of Brazilian dimension stones and the adhesion to mortars, Case Stud. Constr. Mater. 18 (2023) 1–8. doi:10.1016/j.cscm.2023.e01868.

[9]      L. Dvorkin, O. Dvorkin, Y. Garnitsky, Y. Ribakov, Adhesive and cohesive properties of glue cement mortars with addition of organic-mineral modifiers, Mater. Des. 53 (2014) 558–595. doi:10.1016/j.matdes.2013.07.026.

[10]    V.A. Voitovich, Cement-polymer adhesive materials, Polym. Sci. – Ser. D. 2 (2009) 183–186. doi:10.1134/S1995421209030137.

[11]     W. Kujawa, E. Olewnik-Kruszkowska, J. Nowaczyk, Concrete strengthening by introducing polymer-based additives into the cement matrix-a mini review, Materials (Basel). 14 (2021). doi:10.3390/ma14206071.

[12]    Nitin, V. Chaudhary, Yeshpal, Review of advanced cementitious composites using water soluble polymer based admixture, J. Appl. Polym. Sci. 141 (2024) 1–16. doi:10.1002/app.55430.

[13]    S.J. Liu, H. Li, H.J. Liu, J.B. Chen, F.Q. Zhao, Preparation of a new polymer-modified adhesive mortar using fine iron tailings as aggregate, J. Adhes. Sci. Technol. 27 (2013) 951–962. doi:10.1080/01694243.2012.727167.

[14]    R. Zurauskiene, L. Navickiene, Foam Glass Granule Usage in Tile Glue Mixtures That Use a Reduced Portland Cement Amount, Materials (Basel). 16 (2023). doi:10.3390/ma16031269.

[15]    G. Zhao, P. Wang, G. Zhang, Principles of polymer film in tile adhesive mortars at early ages, Mater. Res. Express. 6 (2019) 25317. doi:10.1088/2053-1591/aaf2a2.

[16]    T. Matsumoto, T. Mahaboonpachai, Y. Inaba, R. Rumbayan, Thermal stress analysis and fatigue strength measurement of the interface between concrete and polymer cement mortar, Proc. 6th Int. Conf. Fract. Mech. Concr. Concr. Struct. 3 (2007) 1737–1745.

[17]    J.J. Assaad, Development and use of polymer-modified cement for adhesive and repair applications, Constr. Build. Mater. 163 (2018) 139–148. doi:10.1016/j.conbuildmat.2017.12.103.

[18]    L. Bureau, A. Alliche, P. Pilvin, S. Pascal, Mechanical characterization of a styrene – butadiene modified mortar, Mater. Sci. Eng. A. 308 (2001) 233–240.

[19]    A. Jenni, L. Holzer, R. Zurbriggen, M. Herwegh, Influence of polymers on microstructure and adhesive strength of cementitious tile adhesive mortars, Cem. Concr. Res. 35 (2005) 35–50. doi:10.1016/j.cemconres.2004.06.039.

[20]    A. Jenni, M. Herwegh, R. Zurbriggen, T. Aberle, L. Holzer, Quantitative microstructure analysis of polymer-modified mortars, J. Microsc. 212 (2003) 186–196. doi:10.1046/j.1365-2818.2003.01230.x.

[21]    T. Mahaboonpachai, Y. Kuromiya, T. Matsumoto, Experimental investigation of adhesion failure of the interface between concrete and polymer-cement mortar in an external wall tile structure under a thermal load, Constr. Build. Mater. 22 (2008) 2001–2006. doi:10.1016/j.conbuildmat.2007.07.002.

[22]    D.A. Silva, P.J.M. Monteiro, ESEM analysis of polymeric film in EVA-modified cement paste, Cem. Concr. Res. 35 (2005) 2047–2050. doi:10.1016/j.cemconres.2004.10.037.

[23]    L. Li, K. Liu, B. Chen, R. Wang, Effect of cyclic curing conditions on the tensile bond strength between the polymer modified mortar and the tile, Case Stud. Constr. Mater. 17 (2022) e01531. doi:10.1016/j.cscm.2022.e01531.

[24]    F.L. Maranhão, V.M. John, Bond strength and transversal deformation aging on cement-polymer adhesive mortar, Constr. Build. Mater. 23 (2009) 1022–1027. doi:10.1016/j.conbuildmat.2008.05.019.

[25]    F.L. Maranhão, K. Loh, V.M. John, The influence of moisture on the deformability of cement-polymer adhesive mortar, Constr. Build. Mater. 25 (2011) 2948–2954. doi:10.1016/j.conbuildmat.2010.12.004.

[26]    F.L. Maranhão, M.M. Resende, V.M. John, M.M.S. Bottura De Barros, The bond strength behavior of polymer-modified mortars during a wetting and drying process, Mater. Res. 18 (2015) 1354–1361. doi:10.1590/1516-1439.028915.

[27]    D.D. Nguyen, L.P. Devlin, P. Koshy, C.C. Sorrell, Impact of water-soluble cellulose ethers on polymer-modified mortars, J. Mater. Sci. 49 (2014) 923–951. doi:10.1007/s10853-013-7732-8.

[28]    J.Y. Petit, E. Wirquin, Evaluation of various cellulose ethers performance in ceramic tile adhesive mortars, Int. J. Adhes. Adhes. 40 (2013) 202–209. doi:10.1016/j.ijadhadh.2012.09.007.

[29]    S.K. Turki, S.I. Ibrahim, M.H.D. Almaamori, The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials, Open Eng. 14 (2024). doi:10.1515/eng-2022-0580.

[30]    A. Jenni, R. Zurbriggen, L. Holzer, M. Herwegh, Changes in microstructures and physical properties of polymer-modified mortars during wet storage, Cem. Concr. Res. 36 (2006) 79–90. doi:10.1016/j.cemconres.2005.06.001.

[31]    J.G. Vieira, G. de C. Oliveira, G.R. Filho, R.M.N. de Assunção, C. da S. Meireles, D.A. Cerqueira, W.G. Silva, L.A. de C. Motta, Production, characterization and evaluation of methylcellulose from sugarcane bagasse for applications as viscosity enhancing admixture for cement based material, Carbohydr. Polym. 78 (2009) 779–783. doi:10.1016/j.carbpol.2009.06.016.

[32]    P.I. Abdulrahman, D.K. Bzeni, Bond strength evaluation of polymer modified cement mortar incorporated with polypropylene fibers, Case Stud. Constr. Mater. 17 (2022) e01387. doi:10.1016/j.cscm.2022.e01387.

[33]    A. Pustovgar, A. Zhuravlev, S. Nefedov, I. Ivanova, A. Adamtsevich, A. Esenov, V. Medvedev, Comparison of the effectiveness of fine mineral fillers in cement-based tile adhesives, Adv. Mater. Res. 1004–1005 (2014) 1496–1502. doi:10.4028/www.scientific.net/AMR.1004-1005.1496.