University of Alabama – Birmingham
Department of Civil Engineering

Lab Summary 1

Dennis D Gray
Shayla Olson
Chelsea Caldwell
Collin Hipps
Jamieson Matthews
David Pritchett
Dustin Schultes
Michael Ragan
Mark Casson

02/15/13
CE 222
Materials Laboratory
Craig A. Copham

Introduction

The purpose of this lab was to design, mix, and test a specimen of concrete based on a

specified strength, and the ingredients used in the testing were cement, air, water, sand, and

stone. There was a batch of concrete design to reach the maximum of 5000 psi. The concrete mix

designed was done from ASTM ACI 211 Chapter 6. To determine the slump and air content

ASTM C143 and C231 were used. To calculate the unit weight and making curing concrete test

specimens in the laboratory ASTM C138 and C192 were used for these different test. Once the

test specimens were completely equipped they were covered for a period of time and additional

testing was done.

Results

Concrete Mix Design

|Material |SG |Design Wt.(pcy) |Vol. (ft^3) |MC % |Abs. % |
|Cement |3.15 |763 |763 |3.88 |782 |
|Water |1 |305 |292.04 |4.68 |299 |
|Stone |2.6 |1738 |1738 |10.71 |1780 |
|Sand |2.3 |884 |884 |6.17 |905 |
|Air | |5% |3.4% |0.92 | |
| | | | |Total Volume=26.36 | |

Mixed Proportions

|Cement |Water |Coarse Aggregate |Fine Aggregate |w/c Ratio |Air Dosage (oz/cwt) |
|782 |299 |1780 |905 |0.38 |0.360 |

Fresh Concrete Properties

Unit Weight (pcf)
Water (pcy) |Slump (in.) |Air Dosage (mL/ft^3) |Air % |w/c Ratio |Theoretical |Measured | |299 |4.75 |9.0 |3.4 |0.38 |140.96 |148.72 | |

Discussion of Results

The concrete mix design was developed through pre-determined values and design

specifications. The pre-determined values were the results of previous lab tests that were

conducted to determine the unit weights, specific gravity, absorption, and moisture content

for both the coarse and fine aggregate. Table 1 consisted of the design requirements of ¾ in.

slump and 5000 psi compressive strength. Also, Table 1 explains about cement, sand, water,

stone, and air used as the ingredients in testing the specimen. Table 1 consisted of values of the

specific gravity of cement which was 3.15, water was 1, stone 2.6 and sand 2.3. Table 6.3.4(a)

explain about the water cement ratio which was 0.40 determine by compressive strength of 5000

psi. The design water weight was 305 lb/yd3 from Table 6.3.3. The calculation of the design

weight for cement was done by taking the design weight of 305 lb/yd3 divided by water cement

ratio which was 0.40 was calculated to be 763 pcy. The total design volume was 27ft3. The

volumes of cement water, sand stone, and sand were calculated by using specific gravity, unit

weight of water, and design weight. The moisture content for stone was calculated to be 0.22 %

and sand was 0.06 %. The absorption for stone was calculated to be 0.7% and sand was 0.6%.

The mixed weight used for batch of concrete was 84.7 lbs for cement, 35.3 lbs for water, 193.5

lbs for stone, and 98.5 lbs for sand.

Table 2 describes the balanced mix design prepared by the concrete mix design. Table 2

entails specific gravity, design weight, actual, volume, and balanced weight. The difference

between the design weight and actual weight was the water. The reason for that is because 1.44

lb of water was withheld. That changed the design weight of 305 lbs to an actual weight of

292.04 lbs. The volumes for the balanced mix design remain the same as the concrete mix design

except for a change air due to the air content change from 5% to 3.4% and the volume of air is
0.92 ft3. The total sum of the volumes were 26.36 ft3 and it was compared to the total design

volume of 27 ft3. The balanced weight were then calculated to be cement 782 pcy, water 299

pcy, stone 1780 pcy, and sand 905 pcy.

Table 3 describes the mixed proportions. The cement, water, coarse aggregate, fine

aggregate were used from the balanced weight from Table 2. The water cement ratio was

calculated to be 38% which was lower than the 40% from Table 6.3.4(a). Since there was

water withheld at 1.44 lbs that is the difference between the balanced water cement ratio of 38%

compared to original water cement ratio of 40%. The air dosage was given at 0.360oz/cwt from

the DAREX requirements.

Table 4 describes the fresh concrete properties. The ASTM targeted slump fell in the

range of 3-4 inches but the measured slump in the mix was 4.75 inches. The percent error for

slump was 17 %. The error could have came from adding to much water to concrete mix. There

was 9mL of DAREX AEA (Grace) air dosage in the mix which equals to 0.359oz/cwt compared

to the design of 0.360oz/cwt. In ASTM C231 states that the air entrainment is 5%, but the air

entrainment measured in the mixed was 3.4%. The percent error for air content was 38 %. The

theoretical unit weight value was calculated at 140.96 pcf, and measured unit weightwas

calculated at 148.72 pcf.

There was a percent error calculated between the theoretical and measured weight of

5.5%. The error could have possibly came from the air content changing the amount of water

that was used. The withheld of water could had also had an effect on error due to it having

the water being withheld at 1.44lbs.

Conclusion

The concrete mix was designed using the five major components of air, water, sand,

cement, and stone to determine if it met the ASTM ACI 211 requirements of the 5000 psi

compressive strength. The different test used during this lab was ASTM ACI 211, 138, 192, 143,

and 291. The air content of the final mix was 3.4% which was lower than original air content of 5%. The slump proving to be a 4.75 in which it was above the ASTM target slump of 3-4 inches. We were able to completely fill all of our cylinders to the required levels. Strength is to be measured once samples are cured to confirm design.

Sample Calculations

Air Dosage

0.360 x [pic] = 2.75oz

2.75oz x [pic] = 81.32 mL

81.32mL x [pic] cyd = 9.03mL

9.03mL x [pic] = 0.305 oz

0.305/0.360= 0.85 cwt

0.305 oz/0.85 cwt= 0.359 oz/cwt

[pic]

[pic]

Measured Unit Weight =37.18/.25 = 148.72 pcf