Izaguirre, A. (Ana)
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- Effect of a polypropylene fibre on the behaviour of aerial lime-based mortars(Elsevier, 2011-02) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)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.
- Ageing of lime mortars with admixtures: durability and strength assessment(Elsevier, 2010-07) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)Lime-based mortars modified with admixtures were prepared and subjected to different environments such as outdoor and indoor exposures, climatic chamber, SO2-chamber, and freezing-thawing cycles. The influence that the different admixtures (water repellents, water retainers, polypropylene fibre and a viscosity modifier) had on the pore size distribution of the hardened specimens was assessed and related to the water absorption capacity, and hence to the durability. Ageing resistance and mechanical strengths improved when additives reduced the water intake and increased the air-content. High dosages of water repellents were necessary to enhance the durability, sodium oleate being the most effective additive to endure freezing processes. Also the low tested dosage of fibre, a water retainer (guar gum derivative), and a starch proved to be useful. SO2 deposition caused the formation of calcium sulphite hemihydrate as the main degradation product. A very small amount of calcium sulphate dihydrate was observed. A crystal habit composed of acicular agglomerates of calcium sulphite hemihydrate was detected in SO2 deposition on calcareous materials.
- Characterization of aerial lime-based mortars modified by the addition of two different water-retaining agents(Elsevier, 2011-02) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)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.
- Effect of water-repellent admixtures on the behaviour of aerial lime-based mortars(Elsevier, 2009-11) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)Two different anionic surfactants, sodium oleate and calcium stearate, commercialized as water repellents for cement-based mortars, were added to lime-based mortars in order to check whether they were improved by these admixtures. 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, 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. A clear improvement in lime-based mortars was achieved when sodium oleate was added: strong capillarity reduction and excellent durability in the face of freezing-thawing processes, without any compressive strength drop. The mechanism for this improvement was related to air void formation due to the air entraining ability of these surfactants. Insolubility of calcium stearate turned out to be responsible for fewer air bubbles - as SEM examination revealed – and showed lower effectiveness.
- Behaviour of a starch as a viscosity modifier for aerial lime-based mortars(Elsevier, 2010-03-25) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)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 ζ-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. For large amounts of polymer, steric hindrance and electrostatic repulsive forces appeared, leading to a dispersion mechanism which explained the plasticizing effect as well as the fresh mortar behaviour.
- Biocomposites for building purposes: effect of a guar gum derivative and a potato starch as viscosity modifiers for aerial lime-based mortars(Mahatma Gandhi University, 2010-09-24) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Navarro-Blasco, I. (Iñigo); Fernandez-Alvarez, J.M. (José María); Izaguirre, A. (Ana)Invited lecture presented by Dr. Álvarez on 24th September 2010 at the Windsor Castle on ocassion of the Second International Conference on Natural Polymers held in Kottayam, India.
- Effect of a biodegradable natural polymer on the properties of hardened lime-based mortars(CSIC, 2011-04) Lanas, J. (Javier); Alvarez-Galindo, J.I. (José Ignacio); Izaguirre, A. (Ana)As an environmentally friendly and energy-saving alternative to cement-based materials and to some chemically obtained water-reducers, a commercialized starch was incorporated into aerial lime-based matrix. Five different dosages were tested in order to study the influence that the amount of additive exerted on the properties of the material. Density, shrinkage, water absorption through capillarity, water vapour permeability, mechanical strengths, porosity, pore size distribution, and durability in the face of freezing-thawing cycles were studied in the polymer modified mortars. The tested starch acted as a thickener for dosages up to 0.30%, and changed its behaviour for the largest dosage (0.50%): in that case it behaved as a plasticizer, dispersing the lime through the fresh mass and generating a more workable material. As a result, the matrix of the hardened mortar presented great coherence, owing to its large density and low porosity, characteristics which led to lower capillarity and permeability absorptions, better mechanical properties and improved durability.