cee 3020 practice exam 1

8/10/2019 CEE 3020 Practice Exam 1

1/9

CE 3020 Construction Materials Fall 2004 MIDTERM1

Dr. Kurtis

100 Points Possible NAME:

NO cell phones, NO PDAs.

Calculators OK.

Honor CodeHaving read the Georgia Institute of Technology Academic Honor Code, I understand and accept

my responsibility as a member of the Georgia Tech Community to uphold the Honor Code at all

times. In addition, I understand my options for reporting honor violations as detailed in the code.

______________________________(your signature signifies compliance with the Georgia Tech honor code)


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Question 1 22 points

A concrete batch plant stockpiles two aggregates. Periodically, the field moisture content must be

determined for each aggregate sample. In these tests, 1000g of each aggregate type brought to theoven dry condition (OD) and weighed. Data for each test is given in the table below.

Table 1. Absorption capacity and moisture content data.

FA 1 CA 1

Field Weight (Ww) Ww = 1000.0g Ww =1000.0g

Oven Dry Weight (WOD) WOD= 983.0 WOD= 998.0

Absorption Capacity (%) AC = 0.5% AC = 0.5%

Specific Gravity, SSD 2.46 2.57

1.1) Describe the field moisture state (i.e. wet, SSD, or air dry) of each aggregate, FA1 and CA1.6 points

1.2) The batch plants typical mixture design for 4000 psi concrete consists of:

500 lbs/cu yd cement

300 lbs/cu yd water

1700 lbs/cu yd SSD coarse aggregate

1400 lbs/cu yd SSD fine aggregate

(a) What is the water-to-cement ratio of this mixture? 2 points

(b) Adjust the cement, water, coarse aggregate, and fine aggregate contents, as necessary, to

account for the field moisture conditions described in Table 1. 8 points


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1.3) If 1 cu. ft. of concrete prepared according to the SSD mix proportions given in question 1.2,and compacted in a standard way, was found to have a mass of 142.5 lbs, determine air content ofthe concrete. 4 points

1.4) Based upon your answer to question 1.3, would you expect this concrete to be air entrainedor non-air entrained? 2 points


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2.1) Assuming that all other factors remain the same, which aggregate would you expect to have

the highest compressive strengthin each of the situations 2.1-2.3 described below: 2 points each

a) An aggregate from a sedimentary ormetamorphicorigneous rock.

b) A coarse aggregate with 0.1% or1.0% porosity.c) A normal weight aggregate ora lightweight aggregate.

2.2)How important is the compressive strength of the coarse aggregate in controlling the strengthof normal weight, normal strength concrete? Why? 6 points

2.3) How does the elastic modulus (E) of the coarse aggregate affect the elastic modulus ofnormal weight, normal strength concrete? 4 points

2.4) What is the transition zone or the interfacial transition zone in concrete? What is the

significance of this feature? That is, how does it affect the mechanical behavior and durability ofconcrete? 5 points


5/9

Question 317 points

Fill in the chart below regarding normal hydration of portland cement. 12 points

C3A C3S C2S

Reaction rate

(indicate fastest,slowest, intermediate)

Heat of hydration

(indicate mostexothermic, least

exothermic,intermediate)

Reaction products innormal portland

cement hydration

Fill in the blanks below using 5 points

3.2) As cement hydration proceeds and less gypsum is available for reaction, some of the___________________ formed during early hydration will convert to ________________,making the concrete more vulnerable to sulfate attack.

3.4) The primary differences between ASTM Type I cement and ASTM Type III cement are thatthe Type III cement generally contains more _________ and _________ and less _________ andis ground more finely. As a result, Type III cement reacts more quickly, produces greater heat on

hydration, and produces concrete with higher early strength.


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Because of the ongoing cement shortage, a Type IP cement (a portland cement-pozzolan blend)

have been delivered to a construction site instead of the Type I cement specified by the projectmaterials engineer (You). The cement manufacturer has indicated that the Type IP cement has aspecific gravity of 3.03 and is a blend of portland cement and Class F fly ash. From your CEE

3020 course at Georgia Tech, you recall that the SGcement= 3.15 and the SGfly ash= 2.20.4.1) Determine the relative amounts of pozzolanic material and cement by weight in the cement

blend. 6 points

4.2) Advise the project manager and owner about at least 2 effectsof the partial substitution of fly

ash for cement on the properties of the fresh and/or hardened concrete. 6 points


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5.1) Assuming that all other factors remain the same, which concrete would you expect to have

the shorter setting time (i.e., sets more quickly)in each of the situations 5.1-5.3 described below:2 points each

a) Concrete produced with Type I orType IIIorType V cement.

b) Concrete placed at 10C or22C or34 C

c) Ordinary concrete orconcrete containing fly ash orconcrete containing silica fume

5.2) How does slump vary with w/c? How does is change with time for a given mixture? 4 points

5.3) What kind of chemical admixture(s) would you recommend: 6 points

- To improve the workability of a mixture while maintaining a constant w/c?

- When concreting in cold weather?

- To protect against damage from freeze/thaw cycles?


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Question 612 points

As a materials engineer at the Buzz Batch Plant, your tasks include tailoring existing concrete

mixture designs to suit the needs of your clients. The basic Buzz mixture design, whichconsistently produces workable concrete with normal strength (~5000 psi at 28 days), is describedin Table 1.

Table 1: Standard Buzz Mixture Design for 5000 psi concrete

Material Quantity Characteristics

Water 360 lbs./ cu. yd. tap water

Cement 600 lbs./cu. yd. Type I

Coarse Aggregate 1100 lbs./cu. yd. mixture of crushed granite and

crushed sandstone, MSA=1.5

Fine Aggregate 1500 lbs./cu. yd. FM = 2.8

Chemical Admixtures Air entrainer to produce 6%air

--

SCMs none --

Air content 6-7%

Slump 3.0+ 0.5

What changes do you recommend to the basic Buzz mixture for the following projects? Consider:w/c, ASTM cement Type, aggregate characteristics, mineral admixtures, and chemicaladmixtures. Supply at least 3 recommendationsper project and describe your reasoning behind

your recommendations.

6.1) Construction of a new taxiway at Hartsfield-Jackson Atlanta International airport is planned;

the owner would like a service life of 50+ years with minimal maintenance (its difficult to closea taxiway in the worlds busiest airport!). The taxiway will be treated with alkali-containing(potassium) deicing chemicals during its service life to prevent ice formation at the surface. And,

you are aware of reports of map cracking and gel protrusion in some 20+ year-old Atlantaconcrete structures. 6 points


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6.2) The city of Atlanta has asked Buzz to tailor their standard mixture for concrete constructionrelated to the citys sewer renewal project. The city desires a 100+ year service life in the new

concrete sewer system, with minimal maintenance. Tests of water carried in this system show arange of sulfate concentration from 500 to 1000 ppm SO4, which is typical of moderate sulfate

exposure conditions. 6 points

cee 3020 practice exam 1

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