+1 862 207 3288 Engineering
Individual Discussion:
1. Based on each team’s actual mixing results and what you know about the effects of
water cement ratio on the strength and workability of PCC. Order the teams from 1
to 6 based on which team you think will have the highest compressive strength. If
you think more than one team will have the same (or approximately the same)
strength then rank both equally. Explain your ranking.
CEE 353 Engineering Material
LAB 9: Aggregate
Friday Lab
3/20/2015
Group 1
OBJECTIVE
In this lab, the properties of aggregates were investigated. The experiment contained six parts: sieve analysis, specific gravity and absorption of coarse aggregate, dry rodded unit weight and voids in aggregate, specific gravity and absorption of fine aggregate, moisture content of stockpile, and uncompacted void content of fine aggregate. The purpose of sieve analysis was to see how the particle size of a stockpile distributed. The specific gravity and absorption of coarse and fine aggregate experiment was to determine the mass-volume relationship quantities and water absorption potential. Dry rodded unit weight and voids experiments was to find the dry compacted unit weight. Finally, the moisture content experiment was to determine how much water was held in the aggregate stockpile.
PROCEDURE
PART I: Sieve Analysis(ASTM C136)
Step 1. Check the sieves order so that they were stacked correctly
Step 2. Measure the initial mass of the sample stockpile
Step 3. Put the aggregates on the top sieve and cover the sieve with a lid
Step 4. Put the stack of sieves on the sieve shaker and agitate the sample for 600 seconds
Step 5. Measure the mass of aggregates that retained in each sieve
PART II: Specific Gravity and Absorption of Coarse Aggregate
Step 1. Remove the water from the tray taken out of the water bath
Step 2. Put soaked coarse aggregate into the wire basket such that the sample was submerged in water.
Step 3. Hang the basket from the scale and record the submerged mass.
Step 4. Dry the surface of the aggregate with a towel and measure the saturated-surface-dry mass
Step 5. Put the sample back in the tray and oven dry it for one day, then measure the dry mass.
PART III: Dry Rodded Unit Weight and Voids in Aggregate
Step 1. Measure the mass of the cylindrical measure
Step 2. Fill the measure with aggregate one third full and rod the aggregate layer with 25 strokes
Step 3. Fill the measure two-thirds full and rod the layer with another 25 strokes
Step 4. Fill the measure and rod the layer as above
Step 5. Measure the mass of the measure plus its contents and the mass of the measure alone
PART IV: Specific Gravity and Absorption of Fine Aggregate
Step 1. Calibrate the pycnometer by weight the jar alone and fill it with water and weight it again
Step 2. Add 500 g ± 10g of SSD fine aggregate to the jar with 600ml water in it.
Step 3. Shake the jar for 5 minutes
Step 4. Fill the jar which contained sample with water all the way up the the calibrate point and measure its mass
Step 5. Remove the aggregate from the jar and oven dry it for one day.
Step 6. Weight the oven dried sample.
PART V: Moisture Content of Aggregate Stockpiles
Step 1. Weight the sample container and the aggregate sample
Step 2. Oven dry the sample for one day
Step 3. Weight the oven dried sample
PART VI: Uncompacted Void Content of Fine Aggregate
Step 1. Measure the mass of the container
Step 2. Position the jar and funnel in the stand and center of the cylindrical measure
Step 3. Block the opening of the funnel with a finger and put moderate amount of aggregate in the funnel
Step 4. Remove the finger and allow the sample fall into the container
Step 5. After the container was full, strike off excess heaped fine aggregate from the cylindrical measure by a simple rapid pass of the spatula.
Step 6. Weight the container plus its contents
CALCULATIONS AND RESULTS
PART I: Sieve Analysis(ASTM C136)
Original Total Mass = 4200g
Sieve Size Mass Retained (g) Cumul. Mass Retained (g) Cumul. Percent Retained (%) Percent Passing (%)
¾ in 279.5 279.5 6.58 93.42
½ in 596.8 876.3 20.62 79.38
⅜ in 815.3 1692.6 39.80 60.20
No.4 908.7 2600.3 61.17 38.83
No. 8 736.5 3336.8 78.50 21.50
No. 16 196.5 3533.3 83.12 16.88
No. 30 141.9 3675.2 86.46 13.54
No. 50 304.1 3979.3 93.62 6.38
No. 100 157 4136.3 97.31 2.69
No. 200 86.8 4223.1 99.35 0.65
Pan 27.6 4250.7 100.00 0
Total 4250.7 – – –
Table 1. Results of Sieve Analysis
Table 1 shows the calculated results of the sieve analysis test. The cumulative mass retained was the sum of the aggregate mass in current sieve and larger sieves. The percentage retained mass was equal to the cumulative mass retained divided by the total mass. Also, the percentage retained mass and the percentage passing add up to 100%.
Sample Calculation for Sieve Size No. 8.
CumulativeMassRetained=279.5+596.8+815.3+908.7+736.5=3336.8g
CumulativePercentageRetained=3336.8/4250.7×100=78.5
PercentagePassing=100-78.5=21.5
For a concrete mix design, fineness modulus was a measure of the gradation fineness. The formula of fineness modulus was expressed as follows:
█(Cumulativeretainedpercentage*@@Σ@FinenessModulus=)
* Specific sieves: No. 100, No. 50, No. 30, No. 16, No. 8, No. 4, 3/8″, 3/4″, 1.5″, 3″, and 6″
FinenessModulus=(6.58+20.62+39.8+61.17+78.5+83.12+86.46+93.62+97.31)/100
FinenessModulus=5.27
Figure 1. Semi Log Gradation Graph
Figure 2. 0.45 Power Graph
PART II: Specific Gravity and Absorption of Coarse Aggregate (ASTM C127)
A Mass of oven-dry test sample in air(g) 1853.7
B Mass of saturated-surface-dry test sample in air(g) 1990.1
C Apparent mass of saturated test sample in water (g) 1008.8
Table 2. Mass of Sample in Various Conditions
Table 2 shows the mass of coarse aggregate sample in different conditions. The masses were presented as “A”, “B” and “C”, which were used in following formulas for bulk specific gravity and absorption calculations.
Bulk Specific Gravity (OD)
BulkSp.Gr.(OD)=A/((B-C) )
BulkSp.Gr.(OD)=1853.7/(1990.1-1008.8)
BulkSp.Gr.(OD)=1.89
Bulk Specific Gravity (SSD)
BulkSp.Gr.(SSD)=B/((B-C) )
BulkSp.Gr.(SSD)=1990.1/(1990.1-1008.8)
BulkSp.Gr.(SSD)=2.03
Apparent Specific Gravity
ApparentSp.Gr.=A/((A-C) )
ApparentSp.Gr.=1853.7/(1853.7-1008.8)
ApparentSp.Gr.=2.19
Absorption
Absorption(┤)=(B-A)/A×100
Absorption(┤)=(1990.1-1853.7)/1853.7×100
Absorption(┤)=7.36
PART III: Dry Rodded Unit Weight and Voids in Aggregate (ASTM C29)
Volume(〖ft〗^3 ) W_measure (lb) W_total (lb) DRUM(lb⁄〖ft〗^3 ) Voids(┤)
0.25 8.503 33.246 98.972 15.95
Table 3 Results for Dry Rodded Experiment
Table 3 shows the results of aggregate sample measure during the lab. The mass of the cylindrical measure and aggregates were converted to weight. W_measurewas the weight of the measure alone. W_total was the weight of the measure plus the contents.
The following symbols were used in formulas for bulk specific gravity and absorption calculations.
M:bulkdensityoftheaggregate[lb⁄〖ft〗^3 ];
S:bulkspecificgravity(drybasis)asdetermined∈accordancewithTestMethodC127;
W:densityofwater[62.3 lb⁄ft ^3 ]
DRUW/Bulk Density
M=(W_total-W_measure)/Volume
M=(33.246-8.503)/0.25
M=98.972lb⁄〖ft〗^3
Void %
Voids=((S×W)-M)/(S×W)×100
Voids=((1.89×62.3)-98.972)/(1.89×62.3)×100
Voids=15.95
PART IV: Specific Gravity and Absorption of Fine Aggregate (ASTM C128)
A OD Sample (g) 444.2
B Pycnometer + water (g) 1445.2
C Pycnometer + Sample + Water (g) 1729.3
S SSD Sample (g) 504
Table 4. Mass of Sample and Pycnometer
Table 4 shows the mass of fine aggregate sample and mason jar in different conditions. The masses were presented as “A”, “B”, “C” and “S”, which were used in following formulas for bulk specific gravity and absorption calculations.
Bulk Specific Gravity (OD)
BulkSp.Gr.(OD)=A/((B+S-C) )
BulkSp.Gr.(OD)=444.2/(1445.2+504-1729.3)
BulkSp.Gr.(OD)=2.02
Bulk Specific Gravity (SSD)
BulkSp.Gr.(SSD)=S/((B+S-C) )
BulkSp.Gr.(SSD)=504/(1445.2+504-1729.3)
BulkSp.Gr.(SSD)=2.29
Apparent Specific Gravity
ApparentSpecificGravity=A/((B+A-C) )
ApparentSp.Gr.=444.2/(1445.2+444.2-1729.3)
ApparentSp.Gr.=2.77
Absorption
Absorption(┤)=(S-A)/A×100
Absorption(┤)=(504-444.2)/444.2×100
Absorption(┤)=13.46
PART V: Moisture Content of Aggregate Stockpiles (ASTM C566)
W Mass of original sample(g) 531.5
D Mass of dried sample(g) 530.3
Table 5. Mass of Fine Aggregate Sample
Table 5 shows the mass of fine aggregate whose amount was randomly taken from the stockpiles.
The moisture content was expressed as follows:
MoistureContent=(W-D)/D×100
MoistureContent=(531.5-530.3)/530.3×100
MoistureContent=0.23
PART VI: Uncompacted Void Content of Fine Aggregate (ASTM C1252)
Sample Container Volume(V), mL Mass Sample(F), g Specific Gravity (G) Voids %
Sand 1 100 154.3 2.545 39.37
Sand 2 100 156.4 2.545 38.55
Glass Bead 1 100 160 2.5 36
Glass Bead 2 100 158.7 2.5 36.52
Table 6 Uncompacted Voids for Fine Aggregate
Table 6 shows the results of the uncompacted voids for fine aggregate. The volume of container and specific gravity were given by the lab manual. The sample mass was the net mass of aggregate obtained by subtracting container mass from the total mass. The formula of uncompacted voids was:
Voids=(V-(F⁄G))/V×100
Sample Calculation for Glass bead 1
Voids=(100-(160⁄2.5))/100×100
Voids=36
DISCUSSION
From the gradation analysis and the stockpile definitions given in ASTM D448, the most likely aggregate stockpile that we have sieved is gravel.
There are a few sources of potential problems with the sieve analysis. One could be the time taken during the shaking process. The less time taken during shaking, the less accuracy the results will have, because some particles need more time and shaking to separate into their sieve. Another problem could be the mass of the sieves. The more particles stuck in a sieve the higher its mass will be, which could affect the test results. The sizes of the particles could also cause a potential problem. The amounts of aggregates that are retained in each sieve could be less accurate since it could change. The last potential problem could lie in the fact that sieves stick together after shaking and so when they’re separated, some particles are lost and some move to the wrong sieve, which causes inaccuracy in the results.
The results of relative density and apparent specific gravity calculations could differ significantly upon failure to dry the aggregate to SSD before weighing it. This occurs because the mass of the dried aggregate is less than the weight of the SSD aggregate.
RelativeDensity(OD)=A/(B-C)
RelativeDensity(SSD)=B/(B-C)
Apparentspecificgravity(G_s )=A/(A-C)
Where
A = Dry = 1853.7 g
B = Partially submerged = 1990.1 g
C= Submerged = 1008.8 g
Dried before SSD: Relative Density = 2.028
Not dried before SSD: Relative Density = 1.889
It is known that aggregate can capture water and asphalt binder in surface voids. The amount of water the aggregates absorb is essential for formulating or designing of a concrete. This is because moisture captured in the aggregate voids is not available to react with the cement, or in any way improve the workability of the plastic concrete. Absorption is also important when dealing with asphalt concrete. This is because absorbed asphalt is not available to act as a binder. For some highly absorptive aggregates, a great amount of asphalt binder is needed, making the mix more expensive. At the same time, some asphalt absorption is desired to promote bonding between the asphalt and the aggregate. Thus, low-absorption aggregates are desirable for asphalt concretes.
Although the specific gravity of coarse and fine aggregates is based upon the same basic physical phenomenon, they are computed differently. The difference is, is that the fine aggregate specific gravity accounts for the saturated surface, or the dry weight of the sample. When aggregates are mixed with asphalt binder, only a portion of the water-permeable voids are filled with asphalt. For this reasons, a fourth type of specific gravity is defined called effective specific gravity.
The coarse aggregate specific gravities can be found to the right while the fine aggregate specific gravities can be found to the left.
As shown in the formulas above, the specific gravities are very similar, except that in the fine aggregate specific gravity, the saturated surface for the bulk dry specific gravity must be accounted for. For the bulk SSD specific gravity, the saturated surface is used as the numerator and it’s added to the numerator as well. The absorption is very similar, in that the saturated surface dry weight is the same thing as SSD weight. Therefore, the absorption should be somewhat equal.
It is important to consider the specific gravity of both dry and SSD conditions because in a real-life scenario, it is essential to understand the specific gravity of an aggregate in different situations, for example, when it is dry and/or when it is saturated-surface dry. I only the dry specific gravity is taken into account then the material may act unexpectedly when the aggregate is exposed to very wet conditions. This could cause excessive cracking and/or failure in the material.
