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Memorandum

Subject: Second Phase of concrete design; mixing batches.

This experiment was performed in the lab on October 10th01. The purpose of this memo is to

inform the reader about the process that was used and implemented to create mix batches ofconcrete. This lab was bro!en into measurements and calculation ratios" followed b# mixing.

This is the second phase of the concrete lab; $ix design.

The first part of the lab consisted of calculations. $an# of the calculations were ta!en from theP%&Design and Control of Concrete mixturesas much of the empirical data used in the

concrete design has been recorded o'er the #ears. %alculations were also achie'ed based on

mathematics and data from phase 1. The first calculations were determined b# the group" usingthe data and the boo!(s" was the ratio of water to cemenititious material" followed b# the amount

of water for the gi'en 'olume" then the air entrapment. The fineness modulus" with use of a

table" was used to determine the amount of fine aggregate that was used. )urthermore" the groupdetermined the amount of material that was to fill up the 'olume of the batch with the remaining

amount *a subtotal was gi'en in the P%&+ filled up b# the fine aggregate. %alculations for the

weight of materials added were con'erted to grams.

Once the calculations for the design of the concrete were done" the next step was mixing the

concrete. The concrete was added separatel# in thirds using a double pan with a di'ider to ensure

that the poured concrete is e,uall# distributed in the pan. -sing a simple concrete mixer pro'idedb# the lab" each material was weighed and added separatel# in thirds. The first addition was

water while the mixer was turning. &n extra 0 ml of water was added to insure a better and

easier mixture. The cemenititious material was added followed b# the coarse and the fine

aggregates. The mixture was mixed for se'eral minutes then remo'ed and put into a cone tomeasure the slump which was found to be /. inches. Since the slump was in range" the mixture

was placed bac! into the mixing machine and stirred again. hile the machine was stirring" 11hollow c#linders were collected and oiled down. &dditionall#" the group proceeded to fill the

c#linders with the mixture" placing them on a 'ibrator so as to remo'e the maximum amount of

air bubbles possible. The remaining air content was measured to be about ./ 2 of the 'olume.

The c#linders were left on the 'ibrator to dr# for one da#. The following da# the concrete wasremo'ed from the c#linder with half the batch curing in air and the other half curing in water.

3ach half had a proportional amount of basic concrete and admixture concrete. 4ab clean5up

followed at end of lab.

6n summation" from 'arious calculations and different mixtures" batches of small concretesamples were made. 7ased on data from phase 1 and empirical data fromDesign and Control ofConcrete Mixtures the portions and content of each batch was determined and respecti'el#

mixed. The reactions ta!ing place in the concrete happen due to the water. Therefore" %uring

under water will ma!e a stronger concrete since there is a constant suppl# of water that !eep thereactions going. %uring in air will ma!e the concrete slowl# lose water which will stop the

reactions and therefore decrease the strength of the concrete. &dditionall#" curing under water

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will get rid of air bubbles in the concrete and ma!e it stronger. Phase / will see how well these

samples hold under pressure.

Work Cited

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Kosmatka, Steven H. Design and Control of Concrete Mixtures. N.p.: Portland Cement

Association, 1988. Print.

Read, David . Materials and Measurements Laboratory Manuel at Idaho State University.

Pocatello: !da"o State #niversit$, %&&'. Print.