CEM 200 CONCRETE CONSTRUCTION
(FINAL) QUESTIONS AND ANSWERS
WITH SOLUTIONS 2024
Lec. 6 - ANSWER Lec. 6
What are some characteristics of aggregates? - ANSWER Cleanness, grading, particle shape, texture,
specific gravity, absorption and moisture content, unit weight
What is cleanness? - ANSWER The idea that the presence of contaminating substances reduces
significantly the properties of concrete mix
(Cleanness) Clay and Silt - ANSWER Weaker bond, lower strength, higher mix water
(Cleanness) Organic Materials - ANSWER Better strength and appearance
What is grading? - ANSWER It is the distribution of particle sizes on several specified sizes of sieves; the
test for gradation is known as sieve analysis
What are the standard sieve sizes for coarse aggregate? - ANSWER 2, 1 ½, 1, 3/4, 1/2, 3/8, #4
What are the standard sieve sizes for fine aggregate? - ANSWER #4,#8,#10,#16,#30,#50,#100,#200
What is fineness modulus? - ANSWER Fineness modulus of aggregate is a measure of its fineness; the
fineness modulus can be applied to the entire aggregate, but most usage is found in its application to
fine aggregate
True or False:
In general, higher fineness modulus indicates coarser aggregate, and smaller one indicates a finer
material - ANSWER True
, What are the general particle shapes of aggregate? - ANSWER Round, sub-rounded, sub-angular or
angular
What is the main influence of particle shape? - ANSWER The main influence is on the workability of fresh
concrete;
flat and elongated pieces cause poor workability
What is aggregate texture and why is it important? - ANSWER Aggregate particles may have smooth or
rough surfaces;
roughness is desirable, as it provides better bond with the paste
Moisture content (oven dry) - ANSWER Contains no moisture at all
Moisture content (air dry) - ANSWER Contains less moisture than the aggregate capable of absorbing
Moisture content (saturated surface dry) - ANSWER Contains only absorbed moisture, no more, no less
Moisture content (moist or wet) - ANSWER Contains free moisture on the surface in addition to the
absorbed moisture
True or False:
Absorption of Aggregate should exceed 1%. - ANSWER False
What do higher absorption percentages indicate? - ANSWER Higher percentages indicate porous
aggregate, low specific gravity and lead to poor quality concrete
What is specific gravity? - ANSWER It is the ratio of the weight of the aggregate to the weight of water,
for example: Average specific gravity is 2.65 for gravel
(FINAL) QUESTIONS AND ANSWERS
WITH SOLUTIONS 2024
Lec. 6 - ANSWER Lec. 6
What are some characteristics of aggregates? - ANSWER Cleanness, grading, particle shape, texture,
specific gravity, absorption and moisture content, unit weight
What is cleanness? - ANSWER The idea that the presence of contaminating substances reduces
significantly the properties of concrete mix
(Cleanness) Clay and Silt - ANSWER Weaker bond, lower strength, higher mix water
(Cleanness) Organic Materials - ANSWER Better strength and appearance
What is grading? - ANSWER It is the distribution of particle sizes on several specified sizes of sieves; the
test for gradation is known as sieve analysis
What are the standard sieve sizes for coarse aggregate? - ANSWER 2, 1 ½, 1, 3/4, 1/2, 3/8, #4
What are the standard sieve sizes for fine aggregate? - ANSWER #4,#8,#10,#16,#30,#50,#100,#200
What is fineness modulus? - ANSWER Fineness modulus of aggregate is a measure of its fineness; the
fineness modulus can be applied to the entire aggregate, but most usage is found in its application to
fine aggregate
True or False:
In general, higher fineness modulus indicates coarser aggregate, and smaller one indicates a finer
material - ANSWER True
, What are the general particle shapes of aggregate? - ANSWER Round, sub-rounded, sub-angular or
angular
What is the main influence of particle shape? - ANSWER The main influence is on the workability of fresh
concrete;
flat and elongated pieces cause poor workability
What is aggregate texture and why is it important? - ANSWER Aggregate particles may have smooth or
rough surfaces;
roughness is desirable, as it provides better bond with the paste
Moisture content (oven dry) - ANSWER Contains no moisture at all
Moisture content (air dry) - ANSWER Contains less moisture than the aggregate capable of absorbing
Moisture content (saturated surface dry) - ANSWER Contains only absorbed moisture, no more, no less
Moisture content (moist or wet) - ANSWER Contains free moisture on the surface in addition to the
absorbed moisture
True or False:
Absorption of Aggregate should exceed 1%. - ANSWER False
What do higher absorption percentages indicate? - ANSWER Higher percentages indicate porous
aggregate, low specific gravity and lead to poor quality concrete
What is specific gravity? - ANSWER It is the ratio of the weight of the aggregate to the weight of water,
for example: Average specific gravity is 2.65 for gravel
