Characterization of Hydraulic Lime Mortar Containing Opuntia ficus-indica as a Bio-Admixture for Restoration Applications

Many successful and long lasting structures that contain lime mortars are hydraulic in nature. Organic admixtures are added to lime mortar mix to modify their fresh and hardened state properties. The present work proposes plant extract as bio-admixture for repair mortar towards the protection of heritage structures. The effect of cactus extract on the properties of hydraulic lime mortar is studied. Mortar´s composition is selected with respect to the composition of historic mortars and modern restoration practice. Cactus extract was added to the lime sand mixture with varying concentrations (25%, 50%, 75%, and 100%) and with different fermentation periods of 0, 1, and 2 days The consistency and workability of modified mortar, mechanical behavior, water absorption, porosity, and water/salt absorption through capillary rise, salt crystallization have been studied. Micro structural properties of the resulting mortar have been evaluated by XRD and FT-IR to identify their mineralogical composition and morphology by SEM-EDX. It is observed that addition of 75% cactus extract with 1-day fermentation produces maximum positive effect on the strength and durability properties of lime mortar. It improves the mechanical characteristics, limits water and salt absorption by capillarity into mortar and also show resistance to salt crystallization cycles.     

Effect of natural polymers from cissus glauca roxb on the mechanical and durability properties of hydraulic lime mortar

The tradition of using lime as a binder has been in practice over the centuries and is cited in the architectural feats of all kinds of civilizations. Besides the basic ingredients of lime, sand and water, organic admixtures were also mixed into the mortars to modify fresh and hardened state properties as well as to enhance its durability. The motivation of the present study was to develop a replacement of synthetic admixtures by the bio-admixtures. The plant extract of Cissus glauca Roxb (CGR) which is being used in ancient temples and monuments in Kerala has been tested as admixture in varying concentrations and fermentation periods in lime mortar mix. The admixture is polysaccharide rich and a moisturizing agent.

Tests were conducted to measure changes in microstructure of the mortar; fresh state properties such as setting time and workability, mechanical properties such as compressive strength and flexural strength. Also, physical characteristics of admixture modified mortars such as bulk density, porosity and water absorption were also determined. Morphological analysis using SEM with EDX, mineralogical analysis using XRD and organic analysis adopting FT- IR have been done to validate the results of mechanical and physical tests. Capillary water and salt absorption by suction and resistance to salt crystallization cycles were measured as an indicator of durability properties.

The admixture modified mortar resulted in increased mechanical properties and reduced water absorption. It also limits the capillary rise of water and salt intrusion through the hydrophobic nature. The admixture modified mortar have also offered better resistance against the damaging action of deteriorating salts such as sodium chloride and sodium sulphate crystallization cycles. Polysaccharides and proteins in the plant extract interact with the calcium hydroxide of slaked lime and forms complexes. Hence the, natural polymer has increased the durability of hydraulic lime mortars used for repair and it could be a natural alternative to synthetic admixture.     

Asymmetric Encounters in Native Canada

Occasionally in recent decades, relations between the Canadian state and particular Native communities have spiralled into open confrontation and violence. While such instances reflect the failure of conciliatory or decolonizing politics within a liberal–democratic milieu, scholarship has barely begun to analyze these events in a systematic fashion. This article applies to long-standing questions about political behaviour to the study of Native-state relations in Canada. By this, the authors particularly mean the dynamics of Native peoples' mobilization and institutional engagement. Examining several recent cases of open confrontation, this article looks for the basic circumstances in which violence arises, and how confrontation alters internal political dynamics in Native communities.