Concrete and Mold
Procedure for mixing concrete
1. Weigh out the designed proportions for a 1.6 cubic foot batch of concrete.
a. Divide the water into two buckets, one with about 3/4 of the water. If using air entraining, put the air entraining agent in the 3/4 water bucket.
2. Put about half the coarse aggregate, half the fine aggregate and the 3/4 bucket of water with air entraining in the mixer.
3. Start the mixer and mix until the aggregate is thoroughly wet
4. Carefully add all the cement with the mixer running. Try not to make a lot of dust! Add a little more water and mix until all the cement is blended in.
5. Incrementally add the rest of the coarse and fine aggregate – mix until blended in
6. In very small increments, add enough water from the final quarter of the water to produce a workable mix. A little water goes a long way!!
7. Mix for three minutes, followed by a three minute rest, followed by a two minute final mixing. Cover the mixer opening with a damp towel while resting.
8. Dump some mix out of the mixer into a pan. Perform a slump test. If results are satisfactory, skip to the next step, otherwise:
a. If the slump is less than required, return the concrete to the mixer, add any remaining water, and mix for one minute.
b. Perform a second slump test. If results are satisfactory, move on.
c. If the slump is still less than required, return the concrete to the mixer, add additional water, as well as additional portland cement to maintain the desired water/cement ratio (Wt. of PC added = Wt. of water added/WC ratio), and mix for one minute.
d. Continue taking slump tests and adding water and cement until the desired slump is obtained.
9. Record the final slump and the actual weight of water and cement used.
10. If using superplasticizer, add it to the mixer and mix for one minute.
a. Perform another slump test and record the value.
Procedure for slump test
1. Dampen the slump test mold and place it on a flat, moist, nonabsorbent,
1. Weigh out the designed proportions for a 1.6 cubic foot batch of concrete.
a. Divide the water into two buckets, one with about 3/4 of the water. If using air entraining, put the air entraining agent in the 3/4 water bucket.
2. Put about half the coarse aggregate, half the fine aggregate and the 3/4 bucket of water with air entraining in the mixer.
3. Start the mixer and mix until the aggregate is thoroughly wet
4. Carefully add all the cement with the mixer running. Try not to make a lot of dust! Add a little more water and mix until all the cement is blended in.
5. Incrementally add the rest of the coarse and fine aggregate – mix until blended in
6. In very small increments, add enough water from the final quarter of the water to produce a workable mix. A little water goes a long way!!
7. Mix for three minutes, followed by a three minute rest, followed by a two minute final mixing. Cover the mixer opening with a damp towel while resting.
8. Dump some mix out of the mixer into a pan. Perform a slump test. If results are satisfactory, skip to the next step, otherwise:
a. If the slump is less than required, return the concrete to the mixer, add any remaining water, and mix for one minute.
b. Perform a second slump test. If results are satisfactory, move on.
c. If the slump is still less than required, return the concrete to the mixer, add additional water, as well as additional portland cement to maintain the desired water/cement ratio (Wt. of PC added = Wt. of water added/WC ratio), and mix for one minute.
d. Continue taking slump tests and adding water and cement until the desired slump is obtained.
9. Record the final slump and the actual weight of water and cement used.
10. If using superplasticizer, add it to the mixer and mix for one minute.
a. Perform another slump test and record the value.
Procedure for slump test
1. Dampen the slump test mold and place it on a flat, moist, nonabsorbent,