Polycarboxylate Polymers and Blends in Different Cements

Abstract

During the last few years, polycarboxylate based polymers have become very popular. They contain a polycarboxylic backbone onto which ethyleneoxide side chains have been grafted. However its dispersing and slump keeping properties vary significantly, depending on the chemical structure. The dispersing properties of two polymers having a different number of polyoxyethlene (PEO) graft chains relative to the length of the backbone were evaluated in cement paste by measuring adsorption on cement paste and flow properties in different mortar compositions. The effects of the polymers on the fluidity and the retention of flow of the cementitious systems are significantly different. While one polymer gives a very strong initial water reduction, the second one shows excellent flow retaining properties. When combined, the two polymers are well suited for the production of RMC and self-consolidating concrete mixes with different cements and in different climate zones.

Adsorption of superplasticizer admixtures on alkali-activated slag pastes

“…In the resulting dispersion, the water retained in the flocs is released, enhancing flowability. Other authors have described the factors affecting the fluidizing effect of superplasticizer admixtures, concluding that it depends not only on the type of admixture used, but also on factors associated with the cement itself, such as C 3 A content, type and content of calcium sulphate used as a setting regulator [11][12][13], alkalis content [14], specific surface and particle size distribution [9,15] and type of mineral additions [10,16].…”

Reología y potencial zeta de pastas de cemento con lodos de embalse calcinados y escorias granuladas de horno alto

“…Other authors have described the factors that raise paste flowability and the effect of the type of superplasticiser used. The conclusion reached is that flowability depends not only the type of admixture, but also on the characteristics of the cement itself, such as C 3 A content, type and content of calcium sulphate used as a setting regulator (21-23), alkali content (24), specific surface, particle size distribution (21,25) and type of mineral additions (22,26).…”

“…During hydration, cements with higher C 3 A and sulfate contents form larger amounts of ettringite, a phase with a positive zeta potential (43). Less of this phase forms when the superplasticisers are adsorbed as a result of the interaction between their anions (COO -in PCE and S 3 O -in SNF) and the positively charged sites on adsorben como resultado de la interacción entre sus aniones (COO -en PCE y S 3 O -en SNF) y la carga positiva presente en la superficie de las partículas de cemento y de la adición mineral (GGBS y LC), (26,46 El valor absoluto del potencial zeta aumentaba claramente al aumentar la dosificación de SNF. En las suspensiones de TM, el potencial sólo aumentó ligeramente al aña-dirse entre un 0,2 y un 0,5% de SNF, pero subió de forma notable al añadirse entre un 0,5 y un 1%.…”

“…El SNF se adsorbía a la superficie de las partículas de la pasta, por lo que el potencial zeta de la superficie pasaba the cement and mineral addition (GGBS and CS) particles (26,46 Figure 12). The zeta potential remained essentially unaffected in both types of pastes when a 0.1% dose of PCE was added.…”

“…Otros autores han descrito los factores que aumentan la fluidez de la pasta y el efecto que tiene la naturaleza de superplastificante empleado. Se ha llegado a la conclusión de que la fluidez no sólo depende del tipo de aditivo, sino también de las caracterís-ticas del propio cemento, como el contenido en C 3 A, el tipo y el contenido en sulfato cálcico empleado como regulador de fraguado (21)(22)(23), el contenido en álcalis (24), la superficie específica, la granulometría (21, 25) y la naturaleza de las adiciones minerales (22,26).…”