Colloidal interaction between vinylacetate ethylene latex stabilized by polyvinyl alcohol and portland cement
- 89 Downloads
Interaction between three Vinylacetate Ethylene (VAE) latices with varied surface properties (charge or PVOH stabilized) and cement were studied, through the combined techniques of adsorption and zeta potential measurement. The results showed that all the VAE latices possessed a negative charge in neutral pH, but a lower charge density at a high pH. The non-adsorbed amount was excluded, based on extrapolation from the linear regression of the total depletion amount. Thereof, the calculated results indicated an analogous Langmuir type adsorption for all the latices. The zeta potential results showed a negligible effect of the non-ionic latices on the electro kinetic properties of the cement. This revealed the significance of PVOH on the adsorption of non-ionic latices.
KeywordsNon-ionic latex Polyvinyl alcohol Adsorption Cement
Synthetic polymer has been used to modify cement based materials for many years [1, 2], of which latex or polymer dispersions being one of the most important categories. Latex modified cement or concrete improves the elastic modulus, adhesion, impact resistance, abrasion resistance, etc. of the hardened material . The synergy effect of the latex modified cement composite is related to its microstructure . As a result of its positive effects, studies on the microstructure of latex modified cementitious materials have drawn great attention lately [5, 6, 7, 8].
Recently researchers have gradually come to focus on the interaction mechanism between latex and cement in colloid systems [9, 10, 11, 12]. Interaction in a colloid system is important with respect to cement hydration, as well as to the distribution of the polymer film afterwards, since it determines the microstructure of the composite. Merlin et al.  have investigated the interaction between non-ionic methyl methacrylate/butyl acrylate latex and pure cement minerals by means of a depletion method. Although negligible adsorption was found for the non-ionic alkyl phenol poly(ethylene oxide) surfactant, the adsorption of latex particles was remarkable; this being attributed to the negative surface charge of the latex polymer. Plank et al.  have studied the adsorption of anionic and cationic latices on cement by means of electroacoustic measurements, with preferred adsorption due to opposite surface charges being postulated. Lu et al.  have found that the adsorption of polystyrene latices on cement is dependent on the surface charge density of the latex particles, which significantly affects the rheology of the mixture.
Vinylacetate Ethylene (VAE) latex stabilized by partially hydrolyzed poly (vinyl alcohol-co-vinyl acetate) (PVOH) is considered to be non-ionic. Interaction between latex particles and cement, besides electrostatic forces, may indicate weak adsorption, which should actually be similar to the low adsorption amount of PVOH on minerals, either in the presence of polyacrylic acid  or sodium oleate . In other words, electrostatic interaction is the main driving force for the adsorption of polymers on minerals. Kaufmann et al.  have investigated the interaction between VAE latex and cement by means of the electroacoustic method, speculating that limited adsorption occurs, since little influence on the zeta potential of the cement suspension was observed.
However, VAE based dispersible polymer powder, which is chemically similar to VAE latex stabilized by PVOH, has been observed to affect the hydration of tricalcium aluminate (C3A), behaving differently when interacting with tricalcium silicate (C3S) [15, 16]. Furthermore, changes in the rheology of VAE modified cement paste indicates moderate adsorption . Accordingly, in this study two model VAE latices, stabilized by PVOH and one reference anionic VAE latex possessing an anionic surfactant, were investigated to clarify the possibility of existing interaction mechanisms, other than electrostatic forces between PVOH stabilized latex and cement. The first part of the study was focused on surface characterization of the VAE latices. Consequently, adsorption or depletion was semi-quantitatively determined by a method revised according to Merlin et al. . The zeta potential of cement-latex suspensions was also determined, in order to indicate the possible influence of latex adsorption on electrokinetic properties and to provide indirect proof of an adsorption mechanism. Moreover, the adsorption of PVOH on clinker phases was measured, in order to link the behavior of individual PVOH with VAE latex, stabilized by PVOH.
2 Materials and methods
Ordinary Portland cement, CEM I 42.5 R provided by Schwenk Zement, Bernburg/Germany, with a mineral composition of tricalcium silicate (59.9 wt%), dicalcium silicate (9.4 wt%), tricalcium aluminate (7.9 wt%), tetracalcium aluminate ferrite (9.2 wt%), anhydrite (3.6 wt%), calcite (3.4 wt%) etc., was used in this study. Pure tricalcium silicate and tricalcium aluminate synthetic mineral were purchased and provided by Wacker Chemie and checked with XRD prior to this study.
All materials were used without further purification. Deionized water (conductivity ~ 0.055 µS/cm) was used for all experiments.
2.2 Characterization of the latex polymer and minerals
Characterization of VAE Latices
Specific surface area (m2/g)
Number mean particle size (µm)
Specific surface area of minerals
Laser granulometry (m2/g)
2.3 Adsorption measurements
Latex adsorption on cement, C3S and C3A was investigated. 18 g polymer dispersions with different concentrations, ranging from 0 to 5 wt%, were prepared. Half of the polymer dispersion was mixed with 1 g of mineral for 1 min with a vortex mixer from VWR. Subsequently, a three step method, put forward by Merlin et al. , was carried out to separate the fine mineral particles from the polymer dispersions. Firstly, the tube of polymer/mineral mixture was kept upright for 10 min; secondly, the supernatant was extracted and allowed stand for a further 20 min for non-ionic latex, or centrifuged at 100 g force for the anionic latex, respectively. The second supernatant was recovered with the addition of 0.5 mL of 30 wt% HCl. Finally, the second supernatant was diluted to the same volume as the other untreated half polymer dispersions. Turbidity was measured with a Shimadzu UV 1650 PC spectrometer, at a single wavelength of 800 nm (non-ionic latex) or 850 nm (anionic latex). Depletion was calculated directly, based on the ratio between the values of the supernatant and the untreated polymer dispersions.
PVOH adsorption was investigated on clinker phases. 2.7 g of polymer solution, with different concentrations ranging from 0 to 0.20 wt%, were prepared. The solution was then mixed with 0.3 g of mineral for 1 min and centrifuged for another 15 min at 3000 g force. The supernatant was extracted by syringe and filtered with a 0.4 µm disc filter. 20 µl of 30 wt% HCl was added to the filtrate and diluted to 20 ml. The final solution was measured by a TOC-L from Shimadzu. The filtration of the cement/water mixture was measured as blank. The PVOH solution with specific concentrations was also measured, for the calculation of PVOH depletion.
2.4 Zeta potential (electroacoustic) measurement
Zeta potential was measured using a DT310 from Dispersion Technology. It was calculated according to the colloidal vibration current (CVI), which was induced by ultrasound propagation through a suspension. The principle of this method, as well as its applications, have been described in detail elsewhere . Though this method is able to measure a high solid ratio specimen, high water/cement ratio suspensions were performed in accordance with an adsorption protocol.
20 g of cement powder was mixed with 180 g of polymer dispersion. The polymer concentration ranges from 0 to 1 wt%, with an increment of 0.25 wt%. Because of high ionic background induced by cement hydration, filtration of the cement suspensions was measured prior to the measurements to determine its ionic vibration current, which was set as background and subtracted from the measured CVI in the presence of cement and latex particles. After that, Zeta potential was calculated with the recorded CVI.
2.5 Mix design of the samples
3 Results and discussion
3.1 Surface properties of the latices
3.2 Depletion and adsorption of latex on cement minerals
3.3 Colloidal interaction between non-ionic VAE latex and Portland cement: the role of PVOH
Firstly, polymer like PVOH provides not only steric stabilization but also depletion stabilization in colloids . Change of polymer concentration in the colloids affects local stabilization of colloidal particles, which may result in deposition of colloidal particles on mineral surfaces (via the Van der Waals force). Secondly, latex particles can adsorb onto the mineral surface via surface PVOH. Thirdly, if PVOH is present on the mineral surface, it can exert steric repulsion between the mineral surface and the latex particle. This may be speculated from Fig. 8, where latex adsorption was higher on the surface of C3S than on cement. Since PVOH showed strong interaction with C3A, accumulation of PVOH on the surface of the aluminate phase can be expected. As a result, the silicate surface was more favorable for the adsorption of the latex particles.
Colloidal interaction between VAE latex stabilized by PVOH and Portland cement was found to be less relevant to the surface charge of latex, than to the role of PVOH, which is different from electrostatic/electrosteric stabilized latex. Initial surface coverage on cement minerals is subject to both the adsorption amount and the particle size of the colloids (or specific surface area). Considering this, a weak influence of the VAE latex, stabilized by PVOH on the initial dissolution of cement minerals, can be expected. As such, cement hydration should be less affected by the latex particles. However, a strong interaction of PVOH with the aluminate phase was observed, which undoubtedly affects the hydration kinetics of cement at an early age. The interaction of PVOH with cement minerals would reversely affect the adsorption of the latex particles, which would make the interaction between the VAE latex stabilized by PVOH and cement much more complex.
Yu Jin gratefully acknowledges the scholarship provided by DAAD (German academic exchange service). The authors also greatly appreciate Dr. Ulf Dietrich for the synthesis of model latices and Dr. Wolf-Dieter Hergeth for the helpful discussions. We also appreciate Ms. Jessica Grewe for the TOC measurements.
Compliance with ethical standards
This work is part of Yu Jin’s PhD thesis, which can be found in the repository from TU Berlin (https://depositonce.tu-berlin.de/).
Conflict of interest
The authors declare that they have no conflict of interest.
- 1.Ohama Y (1995) Handbook of polymer-modified concrete and mortars. Properties and process technology. Noyes Publications, Park RidgeGoogle Scholar
- 2.Chandra S, Ohama Y (1994) Polymers in concrete. CRC Press, Boca RatonGoogle Scholar
- 4.van Gemert D (2007) Cement-concrete and concrete-polymer composites. Two merging worlds. In: Kyu-Seok Y (ed) Polymers in concrete, vol 1. Kangwon National University, Chuncheon, pp 3–15Google Scholar
- 11.Kaufmann J, Winnefeld F, Zurbriggen R (2012) Polymer dispersions and their interaction with mortar constituents and ceramic tile surfaces studied by zeta-potential measurements and atomic force microscopy. Cem Concr Compos 34(5):604–611. https://doi.org/10.1016/j.cemconcomp.2012.01.012 CrossRefGoogle Scholar
- 14.Labidi NS, Djebaili A (2008) Studies of the mechanism of polyvinyl alcohol adsorption on the calcite/water interface in the presence of sodium oleate. J Miner Mater Charact Eng 7(2):147–161Google Scholar
- 20.Jin Y (2016) Interaction between vinyl acetate-ethylene latex stabilized with polyvinyl alcohol and Portland cement. Ph. D. dissertation, Technische Univeristät BerlinGoogle Scholar
- 21.Dukhin AS, Goetz PJ (2002) Ultrasound for characterizing colloids. Particle sizing, zeta potential, rheology, vol 15. Elsevier, AmstedamGoogle Scholar
- 22.Chen J, Heitmann JA, Hubbe MA (2003) Dependency of polyelectrolyte complex stoichiometry on the order of addition. 1. Effect of salt concentration during streaming current titrations with strong poly-acid and poly-base. Colloids Surf A Physicochem Eng Asp 223(1–3):215–230. https://doi.org/10.1016/s0927-7757(03)00222-x CrossRefGoogle Scholar
- 25.Al Kelzenberg, Tracy SL, Christiansen BJ et al (1998) Chemistry of the aqueous phase of ordinary Portland. J Am Ceram Soc 81(9):2349–2359Google Scholar
- 30.Allen T (1997) Particle size measurement. Powder technology series, 5th edn. Chapman & Hall, LondonGoogle Scholar