Our researchers

Javier Lanas González

Most recent scientific publications (since 2010)

Authors: Álvarez, J.I.;
Journal: Construction and Building Materials
ISSN 0950-0618  Vol. 25  Nº 2  2011  pp. 992 - 1000
A polypropylene fibre was added to lime-based mortars in order to check whether they were improved by this admixture. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time; hardened state properties such as density, shrinkage, water absorption through capillarity, water vapour permeability, long-term flexural and compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing-thawing cycles. An improvement in some properties of aerial lime-based mortars - such as permeability, mechanical strengths, reduction in macroscopic cracks or durability in the face of freezing-thawing cycles - was achieved when fibre was added at a low dosage. When a larger amount of additive was used, only the reduction in cracks and the durability of the material were improved.
Authors: Álvarez, J.I.;
Journal: CEMENT AND CONCRETE COMPOSITES
ISSN 0958-9465  Vol. 33  Nº 2  2011  pp. 309 - 318
Two different commercial additives that have been reported to act as viscosity enhancing, water retaining admixtures, namely hydroxypropyl methylcellulose and a guar gum derivative, were added to lime-based mortars in order to test their performance. Different properties of lime-based mortars were evaluated: fresh mixture behaviour through water retention, air content and setting time; hardened mixtures properties such as density, shrinkage, water absorption through capillarity, water vapour permeability, long-term compressive strengths, pore structure through mercury intrusion porosimetry and durability assessed by means of freezing-thawing cycles. Hydroxypropyl methylcellulose, unlike its well-known effect in cement-based materials, showed a very limited viscosity enhancing behaviour in aerial lime mortars. An adsorption mechanism of this additive on the Ca(OH)(2) crystals was reported to reduce its entanglement between chains and hence the viscosity of the pastes as well as its water retention ability. The guar gum derivative, which has a larger quantity of ionized groups at alkaline pH, reduced its adsorption onto slaked lime particles and gave rise to a clear increase in viscosity. However, this involved a larger water-retention capacity, which in fact resulted in a delay in setting time. The guar gum derivative proved to raise the air content, and changed the pore size distribution of the hardened mortars, thus improving the water absorption through capillarity and durability in the face of freezing-thawing cycles.
Authors: Álvarez, J.I.;
Journal: Cement and Concrete Research
ISSN 0008-8846  Vol. 40  Nº 7  2010  pp. 1081 - 1095
Authors: Álvarez, J.I.;
Journal: Carbohydrate Polymers
ISSN 0144-8617  Vol. 80  Nº 1  2010  pp. 222 - 228
Different dosages of a commercialized potato starch were added to aerial lime-based mortars in order to check its efficiency as a rheological modifier. Several fresh state properties of the mortars were studied: consistency, density, air content, water retention capacity, setting time and evolution when applied on support. The effect of the starch on zeta-potential of the lime particle surface as well as the particle size distribution and viscosity changes in lime pastes were also assessed in order to elucidate the action mechanism of the polymer. The behaviour of this starch polymer was found to be strongly dosage-dependent: it acted as a thickener when the incorporated dosage was up to 0.30% of lime weight; conversely, above that dosage, it behaved as a plasticizer. The thickening effect took place because polymer molecules were adsorbed onto lime particles acting as a flocculant, as confirmed by zeta-potential and particle size distribution results.