Civil and Construction Engineering Materials homework

CCE 321 Homework 3 Page 1 of 2

CCE 321: Civil and Construction Engineering Materials

Homework 3

Due: October 26th, 2018 by 11:00 am

1. In relation to fresh concrete, please answer the following.

a) Distinguish between consistency and cohesiveness in fresh concrete.

b) Describe how workability of fresh concrete changes over time (e.g. 0-6 hours). What are several factors that can change the workability of fresh concrete over the first 6 hours after it is mixed?

c) If you have lightweight expanded aggregate (e.g. absorption capacity around

15-30%) what is the appropriate test method for determining the fresh air content?

d) Describe proper concrete curing in the laboratory and in the field. 2. Distinguish between initial and final set. How do we measure this for concrete (not for cement paste)? 3. How does the w/cm ratio affect concrete properties? Please be thorough in your answer. 4. List and describe three different supplementary cementitious materials. Highlight advantages and disadvantages as well as approximate percentage replacements (typically a range) for portland cement. 5. Why is air entrainment used in concrete (focus on the main reason but include other reasons as well)? 6. Describe the steps for jointed plain concrete pavement (JPCP) construction. What is the reason for having joints in JPCP? 7. A normal strength concrete is produced and cast into 4 x 8 in. cylindrical molds. The unit weight of the concrete is estimated at 151 lb/ft3. The compressive loads at failure for three specimens after 28 days of proper curing are as follows: Specimen 1 – 70,163 lbf Specimen 2 – 66,719 lbf Specimen 3 – 71,006 lbf Please determine the following and state the assumptions that you used, also make sure to show your calculations.

CCE 321 Homework 3 Page 2 of 2

a) The average 28-day compressive strength (f’c) and standard deviation for this group of three cylinders.

b) The 28-day splitting tensile strength (f’t) (estimate using appropriate

equations)

c) The 28-day elastic modulus (E) (estimate using appropriate equations)