COSC 253 EXAM 2 HARTELL EXAMS QUESTIONS AND ANSWERS
How is concrete priced and ordered? - CORRECT ANSWER✅✅- Concrete is typically measured and
ordered by the cubic yard
- Typical transit-mix truck can mix and deliver up to 10 cubic yards
- Wet(fresh) concrete weighs approximately 150 lbs per cubic foot or 4,050 lbs per cubic yard
Construction steps of concrete construction - CORRECT ANSWER✅✅1. Mixture design to meet
specification
2. Batching of ingredients and mixing of concrete
3. Handling and placement of concrete
4. Consolidation procedures
5. Finishing procedures
6. Curing of concrete
Normal strength concrete - CORRECT ANSWER✅✅- 2500 to 6000 psi compressive
strength
- Made with conventional ingredients
High strength concrete - CORRECT ANSWER✅✅- Greater than 6,000 psi to roughly 20,000 psi
- Admixtures and supplementary cementitious materials are required to reach higher strengths
Batching of ingredients and mixing of concrete - CORRECT ANSWER✅✅- Most concrete is prepared at
batch plants and delivered to the construction site in the transit-mix trucks
- The mixing trucks are constantly rotating so that the concrete is ready to be placed when arriving on
site
- Smaller batches may be prepared on site by hand or with power mixers
Placing concrete - CORRECT ANSWER✅✅- Avoid delays - place ASAP
- Depending on the conditions, concrete can be - placed up to 90 minutes after
, - Mixing commences (can't place after 90 minutes)
- May be placed directly from truck
- Pump truck
Aggregate Segregation - CORRECT ANSWER✅✅- Separation of large aggregate from the finer portions
of concrete mix - must be avoided
- Solution - Place concrete as close to the final position as possible
Consolidation Procedures - CORRECT ANSWER✅✅- Compaction eliminates voids and air pockets within
the concrete
1. Hand rodding or tramping
2. Screeding (top)
3. Vibration (bottom)
Finishing Procedures - CORRECT ANSWER✅✅- Finishing is required for exposed surfaces
- Various surface textures can be specified to add surface traction/friction or for architectural conditions
- Expansion/construction joints are made to minimize cracking
Curing of concrete - CORRECT ANSWER✅✅1. slump test
2. compressive test
Slump Test - CORRECT ANSWER✅✅- ASTM C143
- Used to determine workability/consistency or fresh/wet concrete
- Concrete with too low slump may be stiff and difficult to place
- Specified maximum slump is from 3 to 5 inches
Compressive Test - CORRECT ANSWER✅✅- ASTM C39
- Samples gathered from each batch of concrete delivered to the site
- Concrete is placed in cylindrical mold and consolidated to eliminate voids
How is concrete priced and ordered? - CORRECT ANSWER✅✅- Concrete is typically measured and
ordered by the cubic yard
- Typical transit-mix truck can mix and deliver up to 10 cubic yards
- Wet(fresh) concrete weighs approximately 150 lbs per cubic foot or 4,050 lbs per cubic yard
Construction steps of concrete construction - CORRECT ANSWER✅✅1. Mixture design to meet
specification
2. Batching of ingredients and mixing of concrete
3. Handling and placement of concrete
4. Consolidation procedures
5. Finishing procedures
6. Curing of concrete
Normal strength concrete - CORRECT ANSWER✅✅- 2500 to 6000 psi compressive
strength
- Made with conventional ingredients
High strength concrete - CORRECT ANSWER✅✅- Greater than 6,000 psi to roughly 20,000 psi
- Admixtures and supplementary cementitious materials are required to reach higher strengths
Batching of ingredients and mixing of concrete - CORRECT ANSWER✅✅- Most concrete is prepared at
batch plants and delivered to the construction site in the transit-mix trucks
- The mixing trucks are constantly rotating so that the concrete is ready to be placed when arriving on
site
- Smaller batches may be prepared on site by hand or with power mixers
Placing concrete - CORRECT ANSWER✅✅- Avoid delays - place ASAP
- Depending on the conditions, concrete can be - placed up to 90 minutes after
, - Mixing commences (can't place after 90 minutes)
- May be placed directly from truck
- Pump truck
Aggregate Segregation - CORRECT ANSWER✅✅- Separation of large aggregate from the finer portions
of concrete mix - must be avoided
- Solution - Place concrete as close to the final position as possible
Consolidation Procedures - CORRECT ANSWER✅✅- Compaction eliminates voids and air pockets within
the concrete
1. Hand rodding or tramping
2. Screeding (top)
3. Vibration (bottom)
Finishing Procedures - CORRECT ANSWER✅✅- Finishing is required for exposed surfaces
- Various surface textures can be specified to add surface traction/friction or for architectural conditions
- Expansion/construction joints are made to minimize cracking
Curing of concrete - CORRECT ANSWER✅✅1. slump test
2. compressive test
Slump Test - CORRECT ANSWER✅✅- ASTM C143
- Used to determine workability/consistency or fresh/wet concrete
- Concrete with too low slump may be stiff and difficult to place
- Specified maximum slump is from 3 to 5 inches
Compressive Test - CORRECT ANSWER✅✅- ASTM C39
- Samples gathered from each batch of concrete delivered to the site
- Concrete is placed in cylindrical mold and consolidated to eliminate voids
