Nuestros investigadores

Javier Lanas González

Publicaciones científicas más recientes (desde 2010)

Autores: Fernández Álvarez, José María; Durán Benito, Adrián; Navarro Blasco, Íñigo; et al.
Revista: CEMENT AND CONCRETE RESEARCH
ISSN 0008-8846  Vol. 43  Nº 1  2013  págs. 12 - 24
The effect of individual and combined addition of both nanosilica (NS) and polycarboxylate-ether plasticizer (PCE) admixtures on aerial lime mortars was studied. The sole incorporation of NS increased the water demand, as proved by the mini-spread flow test. An interaction between NS and hydrated lime particles was observed in fresh mixtures by means of particle size distribution studies, zeta potential measurements and optical microscopy, giving rise to agglomerates. On the other hand, the addition of PCE to a lime mortar increased the flowability and accelerated the setting process. PCE was shown to act in lime media as a deflocculating agent, reducing the particle size of the agglomerates through a steric hindrance mechanism. Mechanical strengths were improved in the presence of either NS or PCE, the optimum being attained in the combined presence of both admixtures that involved relevant microstructural modifications, as proved by pore size distributions and SEM observations.
Autores: Izaguirre Eseverri, Ana; Lanas González, Javier; Álvarez Galindo, José Ignacio
Revista: Construction and Building Materials
ISSN 0950-0618  Vol. 25  Nº 2  2011  págs. 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.
Autores: Izaguirre Eseverri, Ana; Lanas González, Javier; Álvarez Galindo, José Ignacio
Revista: CEMENT AND CONCRETE COMPOSITES
ISSN 0958-9465  Vol. 33  Nº 2  2011  págs. 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.
Autores: Izaguirre Eseverri, Ana; Lanas González, Javier; Álvarez Galindo, José Ignacio
Revista: Cement and Concrete Research
ISSN 0008-8846  Vol. 40  Nº 7  2010  págs. 1081 - 1095
Autores: Izaguirre Eseverri, Ana; Lanas González, Javier; Álvarez Galindo, José Ignacio
Revista: Carbohydrate Polymers
ISSN 0144-8617  Vol. 80  Nº 1  2010  págs. 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.
Autores: Navarro Blasco, Íñigo; Durán Benito, Adrián; Fernández Álvarez, José María; et al.
Libro:  Proceedings of the 3rd Historic Mortars Conference HMC 13
2013  págs. 1 - 8
This work deals with the effect of the nanosilica addition on the performance of aerial lime mortars. Several lime mortars were prepared and modified upon the addition of 3, 6, 10 and 20 wt.% of nanosilica. The presence of nanosilica increased the water demand of the fresh mixtures and reduced the appearance of superficial cracks after the spreading of the mortars onto a porous stone. Setting time underwent a delay when the amount of nanosilica ranged from 3 to 10 wt.%. However, samples with 20 wt.% of nanosilica showed a shortened setting time compared to plain lime mortars. Nanosilica reacted with Ca(OH)2 particles, yielding C-S-H compounds and, acting as a nanofiller, nanosilica also caused a pore blockage in the mesoporous range. These facts resulted in an increase in both compressive strength and durability after undergoing freezing-thawing processes. Overall, the addition of nanosilica clearly improves several characteristics of the aerial lime mortars in order to prepare enhanced mixtures to be used for restoration works.