COSC 253 EXAM 2 HARTELL | QUESTIONS AND ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTION
How is concrete priced and ordered? - (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 - (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 - (ANSWER)- 2500 to 6000 psi compressive
strength
- Made with conventional ingredients
High strength concrete - (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 - (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 - (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)
, COSC 253 EXAM 2 HARTELL | QUESTIONS AND ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTION
- May be placed directly from truck
- Pump truck
Aggregate Segregation - (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 - (ANSWER)- Compaction eliminates voids and air pockets within the concrete
1. Hand rodding or tramping
2. Screeding (top)
3. Vibration (bottom)
Finishing Procedures - (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 - (ANSWER)1. slump test
2. compressive test
Slump Test - (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 - (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
COMPLETE SOLUTION
How is concrete priced and ordered? - (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 - (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 - (ANSWER)- 2500 to 6000 psi compressive
strength
- Made with conventional ingredients
High strength concrete - (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 - (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 - (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)
, COSC 253 EXAM 2 HARTELL | QUESTIONS AND ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTION
- May be placed directly from truck
- Pump truck
Aggregate Segregation - (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 - (ANSWER)- Compaction eliminates voids and air pockets within the concrete
1. Hand rodding or tramping
2. Screeding (top)
3. Vibration (bottom)
Finishing Procedures - (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 - (ANSWER)1. slump test
2. compressive test
Slump Test - (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 - (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
