Historic structures weathering

Overview of Weathering and Implications for Preserving Historic Structures... 

Talc is the magnesium silicate structural analog to pyrophyllite. Its properties are nearly identical to pyrophyllite, except that Al3+ cations have been replaced by Mg2+ cations [25], Talc occurs in secondary deposits and is formed by the weathering of magnesium silicate minerals such as olivine and pyroxene [2], In bulk form, talc is also called soapstone and steatite. A typical composition for talc is given in Table 7 [22], Historically, talc has been used extensively in electrical insulator applications, in paints, and as talcum powder [2],... 

Mortar (sometimes called cement) is used to bond surfaces like bricks together, but also for plastering walls. Historically, it has been composed variously of lime, sand, clay, volcanic rock and ash, brick dust, and potsherds. Early lime mortars that set simply by reaction between the lime and carbon dioxide in the air offered little protection from deleterious effects of water to the structure. Aggregate mortars that incorporatepozzolans and silicates, which react to bond with calcium, do not need C02, and some can even set underwater. These are called hydraulic mortars, and offer durability in weather, but are less suitable for situations where plasticity is needed, as in restoration projects, for example. 

Building Materials. Reconsideration of the performance of materials has resulted in numerous modifications to those materials and the structures in which they are used. Energy-efficient modifications are incorporated into the building structure even before the foundation is formed. Foundations themselves are historically responsible for unregulated heat transfer into and out of buildings in the underground levels. Heated basements tend to lose much of their heat to conductive basement walls, while the coolness of those same walls in warm weather contributes to moisture, mildew, and mold problems. 

The degradation of synthetic polymers has been investigated since their commercial introduction because nearly all plastics are affected by exposure to natural weathering forces such as sunlight, oxygen, water, and heat. Historically, most research has focused on developing stable and durable polymer structures that resist these forces. Modern plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyvinyl chloride (PVC) are strong, inexpensive, easily processible, and durable. Durability attributes have led to difficulties when these plastic materials enter the waste stream. 

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