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CIM 3000 Written Exam 2 questions and answers verified 2024
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CIM 3000 Written Exam 2 questions and answers verified 2024
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CIM 3000 Written Exam 2Are aggregates classified according to density? - correct answer ✔Yes.
-Those used to make normal-density concrete are called normal-density
aggregated.
-Those for low-density concrete (historically known as "lightweight" concrete)
that have an air-dried density at 28 days usually in the range of 1440 to 1850
kg/m^3, are called low density aggregates.
-Those for high-density concrete, ranging in density from about 2880-5600
Kg/m^3, are called high-density aggregates.
What are the advantages of low-density aggregate? - correct answer ✔Low-
density aggregate is used to produce concrete with low density.
- Low-density aggregates provide thermal insulation, internal curing, and
better compatibility between the paste and the aggregate.
When is low density / nonstructural concretes used? - correct answer
✔Having an oven-dry density of 800 kg/m^3 or less. These concrete achieve
their low density by incorporating low-density aggregates, air entrainment, or
performed foam.
- These concretes are most commonly used in roof deck systems, where the
advantages include insulating value and improved fire resistance.
What are high-density aggregates? - correct answer ✔generally consist of
high-density minerals or rocks, or they consist of man-made materials, such
as steel or iron.
- High density aggregates are used to produce concrete that has higher than
normal density, usually for radiation shielding or an application where high-
density concrete is needed for counter balancing, ballasting, or stabilizing.
- High density concrete may be used in sound or vibration attenuation and in
improving the abrasion resistance in industrial facilities.
, What is the most important requirement of a concrete aggregate? - correct
answer ✔Aggregate should be resistant to degradation and not undergo
harmful reactions under the conditions to which it will be exposed.
- Deleteriously reactive constituents in an otherwise satisfactory aggregate will
be rendered harmless if used with a portland cement having sufficiently low-
alkali content or if a sufficient amount of pozzolan or slag is used.
- Testing the aggregate with the proposed job materials and considering the
availability of alkalies from outside sources, such as deicing salts, are
recommended
Does the selection of aggregates affect concrete durability? - correct answer
✔Yes. Selecting aggregates that are stable and durable by themselves has
always been a primary requirement for durable concrete.
-Recent developments however, have shown that sometimes aggregates that
are durable by themselves can be deleteriously reactive with alkalies from the
cement or elsewhere.
How can durable aggregates be ensured? - correct answer ✔Durable
aggregates can be ensured by a knowledge of their past performance under
conditions similar to those expected for the structure in question. Where only
new and untried materials are available, examination by a petrographer at the
sources and in the lab, as well as lab tests are justified for important
structures.
What characteristics of the aggregate are of principle concern in affecting the
strength of the concrete? - correct answer ✔- Particle shape, surface texture,
size range of the particles, combination of sizes (grading), and strength and
elastic modulus of the aggregate are important.
- A very high modulus aggregate will contribute to volume stability by increase
brittleness.
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