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Optimization of Concrete Composites Using CCBs as Additives

Joshua L. Baker

Rockdale Magnet School for Science and Technology

Introduction

Coal combustion byproducts have potential for use in concrete composites. If a mix ratio of these byproducts that allows for a strong, yet flexible end product can be achieved, it will be possible to apply the concept to other building materials once the composites’ environmental interactions can be investigated.

Experimental Design Diagram

Materials

• Hydraulic Wedge• Concrete Mixer• Plastic 4” x 8” Cylindrical Molds, 42• CEMEX® Portland Cement, 76.52 lbs.• Headwaters Class C Fly Ash, 6.94 lbs.• Natural Sand, 155.10 lbs.• Headwaters Bottom Ash, sieved, 12.96 lbs.• Stone, Granite, 252.87 lbs.• Water, 40.29 lbs.

Experimentation Procedures Experimentation Procedures (continued)

Data Analysis

Data Analysis (continued)

Discussion and Conclusions

Acknowledgements

OPTIONALLOGO HERE

OPTIONALLOGO HERE

Hypothesis• Research Hypothesis: If 25% of the standard

cementitious material or fine aggregate is respectively replaced with Class C fly ash or bottom ash, then the resulting composite will perform within a 20% margin of similarity to the control.

• Sub-hypothesis: Mix 2 (25% Class C fly ash, 75% Portland cement, sand, stone) will perform similarly to or better than the control mix.

RationaleSuccessfully using CCBs as additives at a 25% replacement rate would greatly decrease negative human environmental impact stemming from dumping of these wastes in landfills and provide a strong, environmentally-responsible composite that can be adapted to new uses.

Each of the four concrete mixes was created using a concrete mixer.

A small amount of the first mix was poured into a unit weight container, and the unit weight was obtained. The cover was placed on the container, sealed, and the air content data was obtained. The unit weight container was cleaned out and the process was repeated with the remaining mixes.

A small amount of freshly-mixed concrete is poured into a mold and leveled off. The mold is then lifted off from the concrete, and the concrete is allowed to spread out. The slump, the distance the concrete spreads out is measured for each mix.

Concrete from each mix is poured into fourteen molds each, fifty-six in total, and then are left to set in room conditions for three days. The cylinders are then removed from their molds and placed into a curing room for another four days. Seven days after being poured in the molds, three samples from each group are placed in a hydraulic wedge, and the compressive strength and ultimate load data for each is obtained. The data and averages for each group are obtained in this way.

ANOVA Data:• Ultimate Load (Day 7): p = 0.005; 0.005 < 0.05; Null

hypothesis rejected• Compressive Strength (Day 7): p = 0.005; 0.005 < 0.05;

Null hypothesis rejected

• Based on the currently available data from experimentation and from data analysis, Mix 2 performed within the 20% margin of similarity to the control for its average compressive strength and ultimate load, thus rejecting the null hypothesis

• The data gathered for Mix 3 performed outside of this margin, supporting the null hypothesis

• More ultimate load and compressive strength data will be collected at the Day 90 curing point

RMSST:John Hendrix

Ernst Enterprises:Tony Dowdy

TEC Services:Steven Maloof and TechniciansBrian Wolfe

Future Research• Investigating the potential environmental effects the

composites may have in certain conditions• Determination of the toxicity of CCBs and their

flammability at different burn stages

Mix 1 (Control): 27.82 lbs. Portland Cement, 58.80 lbs. Natural Sand, 84.49 lbs. Stone

Mix 2: 6.94 lbs. Class C Fly Ash, 20.88 lbs. Portland Cement, 57.87 lbs. Natural Sand, 83.89 lbs. Stone

Mix 3: 27.52 lbs. Portland Cement, 12.96 lbs. Bottom Ash, 38.43 lbs. Natural Sand, 84.49 lbs. Stone

3 Trials 3 Trials 3 Trials

IV: Substituted Coal Combustion Byproduct

DV: Performance of Concrete Composite (Slump, Unit Weight/Density, Air Content, Water Content, Compressive Strength)

Constants: Brand and Type of Portland Cement, Class C Fly Ash, Bottom Ash, and Coarse Aggregate; Ambient Mixing Temperature; Ambient Curing Room Temperature and Moisture

Control 25% Class C Fly Ash 25% Bottom Ash136

138

140

142

144

146

148

150

152

Density

Target DensityActual Density

Mix Type

Dens

ity

(lb/f

3)

Control 25% Class C Fly Ash 25% Bottom Ash0

0.5

1

1.5

2

2.5

Air Content

Mix Type

Air C

onte

nt (%

)

Control Fly Ash Bottom Ash0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

54606.6666666667 55350

42946.6666666667

79870

93276.67

73530

Average Ultimate Load

Ultimate Load (lb) - Day 7Ultimate Load (lb) - Day 56

Ulti

mat

e Lo

ad (l

bs.)

Control Fly Ash Bottom Ash0

1000

2000

3000

4000

5000

6000

7000

8000

4343.33333333333 4403.33333333333

3416.66666666667

6356.67

7420

5850

Average Compressive Strength

Compressive Strength (psi) - Day 7Compressive Strength (psi) - Day 56

Com

pres

sive

Stre

ngth

(psi)