Performance Of Building Materials

Front 1

Durability, or service life, must always be related to what for the useful life of a material?

Back 1

The context/ particular site conditions involved.

Front 2

What property of a material determines the reactivity of it to other materials and to some elements of the environment?

Back 2

The chemical nature

Front 3

True or False:

Small changes in composition canhave a profound influence on the resulting properties

Back 3

True,

Even trace amounts of some substances, as with metal alloys

Front 4

What is a common influence of ultraviolet radiation onorganic materials?

Back 4

Organic molecule has bonds that can be broken and that other changes can be induced through the action of UV radiation.

NOTE: This does not happen with metals or cementitious materials.

Front 5

True or False:

Gypsum plaster can be unstable at relatively moderate temperature conditions and can undergo decomposition at low relative humidity.

Back 5

True

Front 6

What should be considered when determining the physical and mechanical behaviour of a material?

Back 6

Consideration must be given tothe grain, crystallite or polymer molecules, the assemblage of these into the many geometricarrangements that occur, the space or porosity around the units, and the nature and extent of the"bonds," which are the forces that hold these building blocks together. Microstructure

Front 7

What are Non-Porous materials?

Back 7

Includes polymers, metals and ceramics.They are polycrystalline and characterized by continuous grain boundaries. main characterisitic = placticity

Front 8

What are Porous Materials?

Back 8

Most naturally occurring materials and cementitious materials are porous. They contain spaces around crystallites or grains that are interconnected. Important to distinguish spaces that are isolated 'bubbles' vs interconnected.

Front 9

Which material would be considered to have a larger surface area, one with interconnected openings or one with isolated bubbles?

Back 9

The one with interconnected openings aka the porous material.

Front 10

What is the most important parameter to consider when determining the microstructure of a material?

Back 10

Total Porosity

It has a greateffect upon strength but, more important, it providesthe "reservoir" for water which can undergo freezing with corresponding dilation, or a medium fordissolution of constituents for reactions with foreign substances from the atmosphere.

Front 11

True or False:

Normal plastercan have a porosity over 50 per cent by volume, and concrete can be equally porous in extreme cases.

Back 11

True,

Front 12

What are some environmental factors that interact with a material?

Back 12

NOTE: Their significance to the performance of a material lies in the degree of their interaction with the material.

Temperature - material responds to actual temperature and its variation inside the material.

Moisture - moisture content and its change in the material (cycle from wet to dry or reverse). is influenced by rain, wind, humidity and other factors

Solar radiation - UV light deterioration of organic materials,

Foreign matter - any substance or agent that comes in direct contact with a given material. (gas, liquid, bacteria, fungus, animal, insect or even another component of the same structure)

Front 13

Why is identification of the environmental processes or factors responsible for failure extremely difficult?

Back 13

Because environmental factors act in combinations & go through daily & seasonal cycles,imposing constantly changing conditions, resulting in a complex set of variables that controlsthe successive or simultaneous chemical and physical processes responsible for changes in materials.

Front 14

What is the aging of a material vs curing.

Back 14

Aging- slow chemical and physical changes some period after their manufacture. They may involve the completion ofsome of the reactions of forming or the reverse reactions when the material tries to adjust toconditions of storage or service.

Curing - to process or promote the hardening of.

Front 15

True or False,

Plastics and Sealants do not undergo aging.

Back 15

False,

Many organic materials such as plastics and sealants undergo aging. Plastic floor tile often shrinks fora period after manufacture; and freshly fired brick or clay tile also may undergo dimensional changesin storage while adjusting to new conditions of moisture content.

Front 16

What is the chemical/physical process characterized by salts being dissolved and moved by free water in the pores of a materialto the surface where the water evaporates, leaving the salts in the form of a stain?

Back 16

Efflorescence and Crystallization of Soluble Salts

Because of this action ofcrystallizing salts the process has often been linked with frost action, where water in the pores of material crystallizes to ice, also with an expansive force. The best safeguard is to prevent entry ofwater into the material.

Front 17

What chemical/physical process is characterized by the freezing of water in porous materials?

Back 17

Frost Action

The most important cause of weathering of materials in canada. Occurs only in materials that are frequently frozen when very wet, much effort has been made to establish a criterion for the degree of wetness at which a materialbecomes susceptible to frost action, but no single parameter has been established.

Front 18

What are the characteristics of materials that are generally more susceptible to frost action?

Back 18

high porosity and small pores

Front 19

What are some failures that may present in a material affected by wetting and drying movement and/or thermal movement?

Back 19

Can result in stresses within the material and can cause cracking as is the case with dryingshrinkage of concrete. Cracks caused by moisture and thermal movements may not always cause failure bythemselves, they often serve as openings through which more rain can enter the structure, making iteasy for other processes of salt crystallization and frost action to take place.

Front 20

What are some common "chemical attack" changes in materials?

Back 20

Corrosion of metals

Alkali-aggregate reactions in concrete

Sulphate attack on concrete

Weathering of stone and mortar by the action of rain water acidified by the sulphur gases in the air

Photochemical reactions involving ultraviolet light from sunlight and organic materials

Front 21

True or False,

If materials are kept dry much of the failures associated with "chemical attack" can be stopped.

Back 21

True,

For chemical reaction to take place the "ingredients" must come into contact, usually through acommon medium such as water. Reactions usually occur at the surface (in porous materials this includes the internalsurface), so that a highly porous stone is much more subject to attack by sulphur gases than lessporous stone.

Front 22

Temperature is also a contributing factor to chemical attack. At what temperature intervals does the reaction rate double?

Back 22

With every10-degree Centigrade rise in temperature

Front 23

What is a Dilating Pressure?

Back 23

The pressure produced when a Chemical attack alters the properties of the parent material and produces products that may occupy a larger volume. It is a destructive process similar to frost action, that may initiate cracks in the material.

Front 24

What is the only complete test of performance?

Back 24

Trial by Use.

Predictionwill always be limited by lack of complete knowledge; trial by use will be limited by time and inabilityto extrapolate to new conditions. Test methods can be used to supplement knowledge and experiencein predicting performance.