Control of air content in concrete portland cement association. Freezethaw resistance of concrete with marginal air content. Exposure class maximum wcm minimum f c, psi air content additional requirements 4. Cip 21 loss of air content in pumped concrete what is air loss in pumping. The aggregate correction factor explained in astm c 231 must be subtracted from your reading to obtain the net air content. The results showed that the air bubbles in concrete. It covers the reasons you are performing this test, the equipment needed, and the procedure of astm c231. The air content of the concrete in the mixer drum may increase when the mixer load size is three cubic yards or less while air content may decrease in larger load.
The results show that the pressure meter and astm c457 measurements of concrete cylinders were in reasonable agreement. How is the air content of hardened concrete determined. A type b pressure meter is used to determine the air content of normalweight concrete. High air content concrete with low strength could potentially be placed in the structure if boom configuration changes. Dec 12, 2002 air entrained concrete is made by adding a detergent an air entraining admixture to stabilize air bubbles trapped during mixing. There are a few unique procedures listed in the astm c8 to remember. Total air content astm c231b aashto t152 vs astm c457 astm c8 aashto t121 unit weight vs c457 air content astm c173 aashto t196. Airentrained concrete is made by adding a detergent an airentraining admixture to stabilize air bubbles trapped during mixing. Any air voids reduce the strength of concrete, with about a 5% reduction in strength for each 1% increase in the volume of air voids. Astm c173air content of concretevolume air meter duration. The spacing factor determined indicates the average distance from a point in the cement paste to an air void, and the specific surface indicates the average size of the. Standard test method for air content of freshly mixed concrete by the volumetric method 15 minutes 2540 minutes aashto t 121 astm c8.
For this reason, it is applicable to concrete made with relatively dense aggregate particles and requires determination of the aggregate correction factor see 6. Portland cement is the right cement to use, and the air content has to be controlled so that mix. Increasingly, specifiers are testing concrete at the discharge end of concrete pumps and, in some cases, finding air contents much lower than that in samples tested at the truck chute. The measurement of air content in fresh concrete of normal density is typically performed using the pressure method. In 1994, the strategic highway research program shrp published results from a research study on freezing and thawing of concrete, in which a number of concretes containing 2. Determine and record the mass of the measure and the concrete. Standard test method for density unit weight, yield, and air content gravimetric of concrete. The impact of air content on the durability of concrete under. Astm c185 20 standard test method for air content of. This report presents the results of a study of entrained air in portland cement concrete. Aggregates air content is reduced by both an increase in maximum aggregate size and a decrease in sand content.
Dilution of the agent is not recommended unless it is specifically asked for by the instructions given with the agent. Astm c8unit weight of concrete and c231air content via pressure air meter duration. However, the pressure method is frequently preferred because it is relatively fast. May 25, 2015 astm c173 air content of concrete volume air meter duration. The air content of concrete is influenced by many factors other than the potential of the cement for air. Air entrained concrete is produced using air entraining portland cement, or by the introduction of air entraining agents, under careful engineering supervision, as the concrete is mixed on the job. Air content using the super air meter sam optional if time permits 20 minutes aashto t 196 astm c173. Above a slump of 6 to 7 inches, concrete is often too fluid to retain entrained air and air content decreases. Prevent air loss in geiger readymix kansas city concrete author. Optimal air entrainment will protect concrete from the harmful. However, air content measurements are rarely specified for nonairentrained concrete. The amount of entrained air is usually between four and seven percent of the volume of the concrete, but may be varied as required by special. The air is produced in the concre te by the addition of an approved airentraining admixture. Pdf on jan 1, 2018, julia marczewska and others published the impact of air content on the durability of concrete under combined sulphate.
The air content of concrete is influenced by many factors other than the potential of the cement for air entrainment. Air content in pumped concrete, concrete international, volume 14, number 10, october 1992, pp. This is because the air voids formed due to lack of concrete will be measured as the air content of the concrete. Performance examination checklist astm c231 air content t. Revealing the cause for high air content in concrete. Divide the weight of concrete by the known volume 3 4 density, or fresh unit weight. Performance examination checklist astm c231 air content. It is intended to be a supplement to reading the astm as well as a study tool for the aci exam. It is not applicable to concrete made with lightweight aggregate or aircooled blast furnace slag.
Air entrained concrete is made by adding a commercial agent to the concrete in the quantities that each manufacturer will specify. If further reduction in the air content or the use of nonairentrained concrete is necessary, prior approval will be obtained from hqda daeneceg, washington, dc 20314 or the appropriate air force major command. Meter aci concrete field testing techniciangrade i page 4 of 4 in order to merit a passing overall score on the performance examination, each individual step must be passed on either the first or second trial, or on the retrial following a voluntary suspension. The number of voids per unit volume of concrete increased greatly with a small addition of entrained air. In some cases it is observed that air contents are much lower than that in samples tested at discharge from the truck chute. This method of test covers the procedure for determining the air content of freshly mixed concrete by the pressure method. Hardened concrete samples from cylinders or cores can be lapped ground smooth, not polished and subjected to a microscopic examination to determine the total air content. Intentionally entrained air voids improve the resistance of concrete to damage from cycles of freezing and thawing. As the watercement ratio increases, more free water is available for the generation of air bubbles, so air content increases. The amount varies with concrete air content, amount and type of airentraining admixture, cement content, or cement alkali content, and perhaps other factors.
Labora t o ry calculations indi cate that a cubic yard of concre t e with an air content in the range of 3 to 6 percent contains from 400 to. Pdf research results of the relationships between airvolume in airentrained cement paste, mortar and concrete, all designed according to. Clean off all excess concrete from the exterior of the measure including the rim. Air content test for concrete civil engineering world. Uses equalization to determine air content in the concrete. Airentrained concrete is produced using airentraining portland cement, or by the introduction of airentraining agents, under careful engineering supervision, as the concrete is mixed on the job. Freezethaw deterioration of nonairentrained concrete railing. Be sure your geiger readymix concrete doesn t lose any air content as it is being pumped. Airentrained concrete is typically specified in areas of the country where frostrelated damage can occur. Air content of freshly mixed concrete by the pressure method1 3. S44517 control of air content in concrete new manual provides concrete producers and users with tips on achieving and controlling air in concrete. Problems with the compression strength of weatherresistant concrete structures were discovered in.
This method is necessary since the standard pressure method will give false readings. Air content increase by mixing for up to 15 minutes and mixing beyond this time will decrease air content. In the paper, the problem of air entrainment is discussed, formed as a result of the functioning of a superplasticizer on the characteristics both of concrete and a mixture, depending on the content. The air content is read at the dial, which is calibrated for each apparatus. References astm c 231 air content of freshly mixed concrete by the pressure method. Control of air content in concrete air void analyzer figure 1. Either the contractor or the contracting officer may be. The test determines the air content of freshly mixed concrete exclusive of any air that may exist inside voids within aggregate particles. Several factors have been noted in the literature to affect the level of entrained air in concrete. One major disadvantage of concrete is its susceptibility to damage by single or multiple freezethaw cycles.
Increasingly, specifiers are requiring concrete to be tested for air content at the discharge end of concrete pumps at the point of placement in the concrete structure. Volume 19number 1 control of air content in concrete. May 24, 2019 record the number of cups added, and add to the final air content at the end. Astm c231 c231m 17a standard test method for air content. Control of air content in concrete airvoid analyzer figure 1. Entrained air will vary with type, physical condition, speed of the mixer and quantity of concrete that is being mixed. However, concrete can be made frostresistant by using air entraining admixtures.
The pressure measurement technique requires the concrete sample to undergo complete consolidation in a bowl. Because average void spacing decreases as air content increases, an optimum air content at which void spacing will prevent the development of excessive pressure due to. Comparison of fresh concrete air content test methods. Air entrainment and concrete some things every contractor should know about a combination that assures longerlasting and more attractive concrete this photomicrograph of air entrained plastic concrete suggests how minute bubbles of air function as very small ball bearings which make the concrete more workable than a non air entrained mix. A laboratory program at multiple scales including concrete air void analysis, the foam drainage test, and fundamental tests for microproperties of individual bubble shells was conducted. Tex417a, unit weight, yield, and air content gravimetric of concrete section 2 apparatus texas department of transportation 4 08990608 section 2 apparatus the following apparatus is required. Measurement of air content in concrete by pressure air method. Pdf relationship between aircontent in fresh cement paste. The apparatus equalizes and provides you with an air reading how much air it took to equalize the system. Concrete is routinely air entrained in the northern u. Freezethaw deterioration of non air entrained concrete railing. Entrained air is produced during mechanical mixing of concrete that contains an airentraining admixture. Airentrained concrete has air, in a finely divided and dispersed form, purposely induced at the time of mixing. This guide will teach you how to test air content of concrete with a type b pressure meter.
The measurement of air content in fresh concrete of normal density is typically performed using the pressure method astm c 231. Air entrainment is a necessary component of concrete mixtures exposed. The amount varies with concrete air content, amount and type of air entraining admixture, cement content, or cement alkali content, and perhaps other factors. Research has shawn that when the loss of air content is not too high about 3%, the air void system in the concrete may still be. Some highcement mixes made with silica fume that have air contents of 6 % or more may require more than 3 pt of alcohol. Pdf the impact of air content on the durability of concrete under. The shearing action of mixer blades continuously breaks. How to make air entrained concrete air entrained concrete. If the air content of the concrete is to be determined, proceed to rodding procedure step of the fop for aashto t 152. Astm c8 aci density, yield, and air content of concrete. Air entrainment and concrete some things every contractor should know about a combination that assures longerlasting and more attractive concrete this photomicrograph of air entrained plastic concrete suggests how minute bubbles of air function as very small ball bearings which make the concrete more workable than a nonair entrained mix.
Lately, high air contents of concrete have been occasionally observed in finland. Astm c231 aci concrete air content test, pressure method. A well designed concrete mix design with adequate air contents delivered by your company and placed by a. In the paper, the problem of airentrainment is discussed, formed as a result of the functioning of a superplasticizer on the characteristics both of concrete and a. Once the valve is depressed and held, equalization occurs when the known air in the air chamber releases into the unknown air content in the concrete sample in the bowl below. Standard test method for air content of freshly mixed. Mass per cubic foot meter, yield and air content gravimetric of freshly mixed concrete 2. Because of the high water absorption of lightweight aggregate, the air content of the mixture is measured using astm c 173 standard test met hod for air content of freshly mixed concrete by the volumetric method. Aggregatesair content is reduced by both an increase in maximum aggregate size and a decrease in sand content. Pdf control of air content in concrete semantic scholar.
Volume 19number 1 control of air content in concrete april 1998. Measurement of air content is an important checking sensor for the concrete user to know whether concrete will resist freezethaw damage. False, if the air content is more than 9%, the number of calibrated cups of water introduced into the meter to bring the liquid level within the graduated range must be added. Factors such as cement content and fineness, coarse aggregate size.
Specifications such as aci 301 and masterspec 033000 castinplace concrete, however, require a maximum air content in concrete floors to receive a hardtroweled finish. Factors which may influence air content air contents are an extremely important facet of todays concrete mix design criteria and subsequent inplace concrete performance and durability characteristics. In fresh concrete, the air bubbles reduce the water demand of the concrete and make the mix stickier, which helps to reduce segregation and reduces bleeding when air content is around 3%. Air entrainment and its effects in concrete aggregate. Proper rodding above a slump of 75mm, internal vibration below 25mm is necessary to undergo proper consolidation. It is not applicable to concrete made with lightweight aggregate or air cooled blast furnace slag. Entrained air will vary with type, physical condition, speed of. Air content of freshly mixed concrete by the pressure method txdot designation. By dividing the cement content of the concrete by the void content of the concrete the sum of air and water, when both are expressed in absolute. Density of fresh concrete california test 518 air content by pressure method california test 504 air content by volumetric method california test 543 proportion of coarse aggregate california test 529 tests for compressive strength california test 521 number of test cylinders. Apparatus air meter, type b, calibrated in accordance with aashto t 152 basic function check of air meter by iat air chamber can be pressurized to stabilized maximum ipl mark pressure loss no more than 12 ipl mark in 90 seconds. Determination of properties of air voids in concrete. The effects of air content, watercement ratio, and aggregate type on the flexural fatigue strength of plain concrete. This test method is intended for use with concrete made with relatively dense aggregates.