NEW ERA UNIVERSITYCOLLEGE OF ENGINEERING AND TECHNOLOGYDEPARTMENT OF CIVIL ENGINEERING

CONSTRUCTION MATERIALS AND TESTING

LABORATORY MANUAL(2012 EDITION)

BYGERMAN B. BARLIS, DT

Laboratory Exercise No. 16

AIR CONTENT OF FRESHY CONCRETEBY THE VOLUMETRIC METHOD

Name:Santos,Katrina Cassandra Date Performed:SEPTEMBER 19,2012

Course/Year: BSCE/4th YearDate Submitted:SEPTEMBER ,2012

Section:Wed 8:30-11:30aInstructor: Bro. GERMAN B. BARLIS

Laboratory Exercise No. 16AIR CONTENT OF FRESH CONCRETE BY THE VOLUMETRIC METHOD

FINAL DATA SHEET

A. Proportion by Mass

Trial Numbers

Descriptions1234

Mass of cement, kg

Mass of sand, kg

Mass of gravel ,kg

Mass of water, kg

Water-Cement Ratio

Air Content ,%

A. Proportion by Volume

Trial Numbers

Descriptions1234

Volume of cement, m30.027838

Volume of sand, m30.055676

Volume of gravel,m30.083514

Volume of water, m3UNKNOWNUNKNOWNUNKNOWNUNKNOWN

Water-Cement RatioUNKNOWNUNKNOWNUNKNOWNUNKNOWN

Air Content ,%2.5%

Name: Santos, Katrina Cassandra T.Date Performed: September 19.2012

Course/Year: 4th Year BS Civil EngineeringInstructor : Bro. German Barlis

Laboratory Exercise No. 16AIR CONTENT OF FRESH CONCRETE NY VOLUMETRIC METHOD

PRELIMINARY DATA SHEETB. Proportion by Mass

Trial Numbers

Descriptions1234

Mass of cement, kg

Mass of sand, kg

Mass of gravel,kg

Mass of water, kg

Water-Cement Ratio

Air Content,%

B. Proportion by Volume

Trial Numbers

Descriptions1234

Volume of cement, m30.027838

Volume of sand, m30.055676

Volume of gravel, m30.083514

Volume of water, m3UNKNOWNUNKNOWNUNKNOWNUNKNOWN

Water-Cement RatioUNKNOWNUNKNOWNUNKNOWNUNKNOWN

Air Content Ratio,%2.5%

Group No . 5

Group Leader :Caigas, YolleneGroup Members :Signature1. Balolong,Florence Joy__________________2. Elorde,Karina Klaire__________________3. Mendiola, Reyniel John__________________4. Santos, Katrina Cassandra__________________

Approved by;

Bro. German Barlis, D (Instructor)

SET UP OF APPARATUS

After placing a freshly mixed concrete Inside the Measuring bowl of the device, We rod each of the two layers twenty-five times.

After rodded each layer, we tapped the side of measuring bowl 10 times with the rubber mallet . Clean the top flange and exterior of the measuring bowl to remove excess concrete

After cleaning process, we placed the cover and tighten the clampWe put water inside the volumetric airmeter ,and tilted the device and vigorously roll the air meter

Place the meter upright , loosen the cap and allow the liquid level to stabilze until water level does not change by more than 0.1 percent. And then we repeat rolling and rocking procedure for one minute until two consecutive readings do not change by more than 0.25% air content.

SAMPLE COMPUTATION

Ratio 1:2:3

For Cement;

Cement = 0.027838m

For Sand;

Sand = 0.055676m

For Gravel;

Gravel= 0.083514m

ANALYSIS AND INTERPRETATION OF DATA AND RESULTIn this laboratory exercise, we learned The importance of volumetric method in measuring the air entrained ,it is also called the roll-a-meter, is practical for field-testing all concretes, including those with lightweight and porous aggregates. This method covers the two classification which are : Proportion by mass ,wherein the mass of cement, mass of sand, mass of gravel, and mass of water is being determine . The second classification is the Proportion by volume of the slump, wherein the volume of cement, sand,gravel, and water is being determined. For both classifications Water-cement ratio and slump is recorded. This test method has been developed to measure the air content of freshly mixed concrete. In this method, air entrained in concrete is released and allow to float by agitation. The volume released air is measured using the built in sight tube that provides direct reading of percentage if air content. As seen the tabulated data, we measured a freshly mixed concrete With a concrete Volume ratio of 1:2:3 , we have a total volume of cement which is 0.027833m3, a total volume of 0.055676m for sand, and a total volume of Gravel which. 0.083514m . And we measured a 2.5% air content. Thirdly, the pressure and volumetric methods measure the air content in the concrete before it has passed through the paver and undergone vibration and consolidation, further limiting their ability to accurately represent the concretes durability. These shortcomings limit the existing procedures usefulness in the field for quality control and quality assurance plans and specifications, particularly those aimed at long-term durability.

In addition, the volumetric method have three other major deficiencies. First, the methods yield total air content in concrete (entrained and entrapped air) rather than only the entrained air, which is what affects the durability of hardened concrete. Second, the methods give neither the size of air-entrained bubbles nor information on the spacing of bubbles.However, this method is not capable of accurately measuring air content of concrete made with synthetic air-entraining agents. Which produce small bubbles of high surface tension.

CONCLUSION

Upon the completion of this experiment, we were able to learn the right procedure of measuring the air entrained content of freshly mixed concrete and we also complied to the objectives in which to know the importance of air entrained content in a concrete. I therefore conclude that, The volumetric method simply tests fresh concretes containing any type of aggregate by measuring the volume of entrained air directly. \sample of the concrete is placed in the testing apparatus and air is expelled from the concrete by manual methods. A direct reading is made. This technique can also be employed using only mortar (cement, sand and water).

I also learned that Low air content concrete may be re-mixed at mixing speed and re-tested for acceptance. High air content concrete may be allowed to mix on agitating revolutions for a period of time and then be re-tested. The type of air entraining agent can have a major effect on the ability to entrain and hold air in concrete. Remixing air-entrained concrete should be done with caution, as too much mixing can cause too high an air, which can result in strength loss.