A Comperative Study on the Influence of Mineral Additives to the Physicomechanical Properties of NHL Mortars Cured in Water (original) (raw)
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180 different mortars made with a natural hydraulic lime and different kinds of aggregates were prepared in order to be used in restoration works. The factors affecting the mechanical behavior have been studied at long-term test. Compressive and flexural strengths of the specimens were discussed according to curing time, binder:aggregate ratios, attributes of the aggregates and porosity. Three phases of hardening have been established as a function of the chemical composition: C 3 S contributes to the strength at early ages. C 2 S and the carbonation process give their strengths at long term. Specimens with larger binder amounts have shown higher porosity and strength. The characteristics of the aggregates have been correlated with the strength and porosity. Limestone aggregates contribute to the strength. Rounded shaped aggregates, increasing large pores, cause a strength reduction, so their use is not advisable. Aggregates with small grain size show a good cohesion at the interface improving the strength.
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2010
Water content affects mortar properties and the quality of the resultant masonry, however, it is often subjectively determined by the mason by assessing workability. This lack of explicit methodology and data, can lead to lack of mortar consistency and field performance, adversely affecting full uptake of lime mortars into mainstream technology. The aim of this research is to assist develop consistent lime mortars of high quality, that would improve the strength and durability of masonry. To this aim, the paper investigates the compressive, flexural and bond strength of clay brick masonry bound with natural hydraulic lime mortar (NHL2), at variable water contents delivering different workabilities. The results evidenced that increasing the water content by 1% yields a 5mm increase in initial flow (from 165 to 170mm). It was found that this water increment significantly increases the mortar's compressive strength simultaneously reducing its flexural strength, but it does not increase stiffness under compression. It was also evidenced that the 1% water increment significantly enhances the masonry's compressive, bond and flexural strengths. From these, it was concluded that mixing NHL2 mortars to produce a 170mm initial flow will result in a consistently adequate strength and mechanical behaviour for mortar and masonry.
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Most historic and traditional mortars were made with lime. Due to their nature and function lime mortars weather and need to be replaced. Ordinary portland cement mortars can often be incompatible with historic masonry causing structural and aesthetic damage. Petrographic analysis of original mortars from Clonmacnoise Monastery and Ardamullivan Castle evidenced that they were fabricated with feebly hydraulic and magnesian lime respectively. Within a National Monuments’ conservation programme, the original mortars were replicated and tested and the best performers selected to undertake repairs. This paper investigates mortars made with four types of lime binder: fat, feebly-hydraulic, moderately-hydraulic and magnesian lime. The results indicate that lime mortars conduct moisture to a greater extent than OPC mortars. The feebly-hydraulic lime mortar has the lightest microstructure and highest porosity and absorption, being capable of holding the greatest amount of moisture thus being...
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Natural Hydraulic Lime (NHL) mortars are well-extended in restoration works presently. However, there is still a lack of standardization on their dosage methodology. Thus, seven types of mortar were fabricated and five factors which have an influence on their properties have been studied, in particular the water-binder ratio, the mold material, the aggregate size and type and the different curing conditions. Furthermore, an advanced mechanical characterization has been performed on these mortars, including the measurement of the fracture energy. Finally, some empirical equations for determining the relationships between these mechanical properties were proposed, which could be helpful when simulating the numerical models of historical constructions.
Natural hydraulic lime mortars: influence of the aggregates
Natural hydraulic lime specifications changed with the new version of standard EN 459-1: 2010 and a new Portuguese NHL3.5 appeared in the market. The characteristics of mortars depend on many different parameters such as the type of binder, the type of aggregates, the use of fillers and of superplasticizers; also on mixing and curing conditions. In this paper NHL3.5 mortars with binder:aggregate volumetric proportions1:3 were prepared, varying the aggregates type and proportions between them. Two coarse sands, a medium sand, a river sand, a finer sand, a calcareous filler and a ceramic powder were used. The two last mentioned aggregates were byproducts from industry. Prismatic mortar samples and samples of mortar applied over brick were prepared and conditioned in two different situationsfollowing standard EN 1015-11 and at 65% relative humidity with initial daily water spray. Mortars were characterized in the fresh state and at the age of 28 days. Results showed the influence namely of the curing, particularly in terms of water capillary, of the superplasticizer and of the fillers. They also showed that NHL3.5 mortars seem to be adequate for old masonries conservation and repair and, in some situations, they can be an alternative to air lime based mortars.
Construction and Building Materials, 2014
The new version of EN 459-1 standard for building limes redefined the classes of hydraulic limes and made the producers reformulate or reclassify their natural hydraulic limes. This work evaluates the mechanical, physical and microstructural behavior of mortars formulated with a recently produced natural hydraulic lime NHL3.5 that conforms to EN 459-1, submitted to natural marine environment, humid and standardized conditions, and also the benefits and drawbacks of adding metakaolin in partial replacement of lime. Mortars with NHL3.5 present positive results at young ages. The metakaolin addition increases strength while decreasing the capillary water coefficient. The behavior in an aggressive marine environment seems promising.
Effect of mortar water content in the properties of masonry
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Water content affects mortar and masonry properties however, it is often determined by the mason assessing mortar workability. This can lead to lack of consistency and variable masonry performance. This paper investigates the compressive, flexural and bond strength and stiffness of brick masonry bound with natural hydraulic limes (NHL2, 3.5 and 5), hydrated lime (calcium limeCL90s) and cement-lime mortars with two different water contents (those required to produce a 165 and a 170mm initial flow) both delivering an adequate workability. Increasing water content by 0.61.3% generated the required 5mm flow increase. It was found that this water increment generally improves the compressive/flexural/bond strength and stiffness of the cement-lime and NHL masonry whereas it adversely affects the properties of CL masonry. The results also indicate that varying water content affects brick masonry stiffness, bond and flexural strength to a greater extent than compressive strength; and that th...
Natural hydraulic lime mortars with ceramic residues for masonry
In Portugal natural hydraulic limes have recently been formulated to accomplish EN 459-1:2010 requirements and, for that reason, knowledge on mortars with that particular binder is still recent. With the downturn of the building sector and sustainable practices awareness, many ceramic factories and construction sites have had to reconsider the management of their wastes. Ceramic wastes were often used in the past as pozzolans of air lime mortars. Bearing these considerations in mind, mortars with low content of a natural hydraulic lime and additions of two ceramic wastes were formulated, cured in laboratory conditions and exterior environment and characterized by destructive and non-destructive methods. Aspects related to workability, mechanical resistances, water absorption, drying and resistance to sulphates´ attack are analysed. The viability and drawbacks of the addition of ceramic wastes to low binder content natural hydraulic lime-based mortars to be applied on masonries are highlighted.