2 edition of Concrete pumping effects on entrained air-voids found in the catalog.
Concrete pumping effects on entrained air-voids
by Washington State Dept. of Transportation, Available through the National Technical Information Service in [Olympia, Wash.], [Springfield, Va
Written in English
|Statement||by William Elkey, Donald J. Janssen, Kenneth C. Hover.|
|Contributions||Janssen, Donald J., Hover, Kenneth C., Washington (State). Dept. of Transportation., Washington State Transportation Center., Washington State Transportation Commission.|
|The Physical Object|
|Pagination||2 v. :|
The procedures are applied to ten concrete specimens, at magnifications of 12x and 30x. The specimens represent concretes made using three different air-entraining admixtures, as well as non-air entrained concrete. Air-void parameters calculated from corrected image analysis results for File Size: 7MB. Concrete slab pour 1B was supposed to be routine, occurring early in the construction of a parking garage in the Midwest. However, low compressive strength issues led to lengthy and costly project delays, as well as some interesting theories about the causes.
Because entrained air voids help to protect concrete from damage by frostaction by providing void spaces that reduce the build-up of hydraulic pressure caused by migrating water, we postulated that entrained air may similarly benefit concrete subjected to accelerated steam curing. The loss of potential strength in the steam-cured specimens was Author: J E Gillott, B Czarnecki. the saturation condition of entrained air voids in laboratory tests and in service is discussed. This paper compares the results of steady and non-steady state migration tests on concrete specimens when air voids are saturated and when air voids are primarily empty. The implications of the observed difference are discussed to provide a better.
The specimens represent concretes made using three different airentraining admixtures, as well as non-air entrained concrete. Air-void parameters calculated from corrected image analysis results for the ten specimens are compared to results obtained using the modified point count method and to freeze-thaw results obtained from surface scaling. air voids generally have an irregular shape and are larger than intentionally entrained air voids. All voids reduce the density of the concrete and thus adversely affect some physical properties, such as strength. However, the small entrained air voids provide a very beneficial characteristic: resistance to deterioration from the effects of.
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Concrete Pumping Effects on Entrained Air-Voids Author: William Elkey, Donald J. Janssen, Kenneth C. Hover Subject: Admixtures, Air entraining agents, Air voids, Fly ash, Freeze thaw durability, Lignosulfonate, Mix design, Pressurization, Pumped concrete, Stability \(Mechanics\), Water reducing agents Keywords.
Unfortunately, pumping concrete can affect the air content of a concrete mix. This has caused concern about the possible loss of resistance of the concrete to freezing and thawing.
The actual effect of pumping on the air content measured for the concrete is not consistent; in some cases air content has increased, while in others it has decreased. The effects of entrained air on microstructure and transport properties of concrete with up to % air at different w/c ratios, curing and conditioning regimes were investigated.
It was found that air voids disrupt the packing of cement and increase the heterogeneity of the by: Controlling Air Content in Concrete That is Being Pumped, A Synthesis Study Author: Charles F.
Scholer and Jay Grossman Keywords: air content, air-entrained concrete, entrained air, pumping, air voids, SPR Created Date: 1/30/ PM. The role of these pores in the frost Concrete pumping effects on entrained air-voids book of concrete is believed to be strongly dependent on their degree of saturation at the time of freezing.
The number of air voids smaller than 10 æm in diameter, however, was found to represent less than 10 percent of Cited by: 1. Besides the increase in freeze-thaw and scaling resistances, air-entrained concrete is more workable than non-entrained concrete. The use of air-entraining agents also reduces bleeding and segregation of fresh concrete (Whiting ; ACI Comm.
; Rixom. Air entrainment and concrete Some things every contractor should know about a combination that assures longer-lasting 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 Size: KB.
Entrapped air voids are usually irregular in shape while smaller entrained air bubbles are spherical. Air-entraining admixtures stabilize bubbles at a smaller size. Concrete with an air-void system of mostly smaller bubbles loses very little strength and has much better workability. More air voids in the microstructure of concrete mixture provide more spaces to relieve hydrostatic pressure and prevent deterioration to concrete mixture (H.S.
Wong, et al., ) (Kabashi, et al. 8 The effects of entrained air on microstructure and transport properties of concrete with up to % air at different w/c 9 ratios, curing and conditioning regimes were investigated.
It was found that air voids disrupt the packing of cement and. The effects of entrained air on microstructure and transport properties of concrete with up to % air at different w/c ratios, curing and conditioning regimes were investigated. voids in concrete may vary from about mm.
in normal concrete to less than half that size m air-entrained concrete. The number of voids per unit volume of concrete increased greatly with a small addition of entrained air; and for a given amount of entrained air, concrete with a File Size: 1MB.
Benefits of Air-Entrained Concrete. The main reason for using air-entrained concrete is for the increased resistance of concrete against the alternating freezing and thawing cycles of water, which can occur during those periods when the surrounding temperature drops below 0 ° C.
During such events, the entrained air bubbles in the concrete act. The paper discusses the role of entrained air voids on the transformation from liquid to solid of cement based materials (paste, mortar, concrete). The discussion is based on pore water pressure and volume change measurements.
Air pores seem to contribute to increased rate of autogenous shrinkage in the time before the “knee-point” (i.e. in the few hours before autogenous Cited by: M Richardson, in Durability of Concrete and Cement Composites, Allowance for strength loss.
Air entrainment leads to a loss of concrete strength. Typically the direct strength loss is about % per percentage of air entrainment though this effect can be somewhat offset by the improved workability (reduced water demand) of air entrained concrete (Wright, ).
The American Concrete Institute. Founded in and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete.
Entrained Air Voids. Entrained voids are small spherical voids enfolded by the mixer. Surface-active, air-entraining agents are added to the mixture to stabilize a specified percentage of these voids and thus protect the hardened HCC against the destructive forces of freezing and thawing.
Thus, the entrained air void is a desirable void. And ACI R Guide for Consolidation of Concrete, Section“Over Vibration Effects,” states, “Loss of entrained air in air-entrained concrete—This can reduce the concrete’s resistance to cycles of freezing and thawing.
The problem generally occurs in mixtures with excessive water contents. or to voids within particles of aggregate. Air voids are almost invariably larger than 2 JL in diameter. The term includes both 'entrapped' and 'entrained' air voids " (e) Air Content, A___:The proportional volume of air voids.
in concrete expressed as a percentage of the volume of the hardened con crete. discrete air voids in concrete, termed “entrained air.” Non-air-entrained (left side) and properly air-entrained concretes (right side) are shown in Fig.
Most of the entrained air bubbles are smaller than the head of a pin (shown). The air voids provide empty spaces within the. second type of air voids - "entrained" air voids are retained in the concrete as a result of entrapment among the aggregate, adherence by surface-chemical forces to particles of cement and aggregate, and the Washington Aggregates and Concrete Association, Effects of Pumping Air Entrained Concrete, Ma 3.
Troxell, George Earl File Size: 2MB.Fly Ash -Carbon Effects on Concrete Air Entrainment: Fundamental Studies on the ir Origin and Chemical Mitigation Carmel Jolicoeur 1, Thi Cong To 1, Éric Benoît 1, Russell Hill 2, Zhaozhou Zhang 3 and Monique Pagé 4 1 Department of Chemistry, Université de Sher br ooke, boul Université, Sherbrooke, QC, J1K 2R1; 2 Boral Materials Technologies, Inc., 45 NE LoopSize: KB.The air entrained concrete has a whipped cream effect that allows slump reduction.
Engineers take advantage of this slump reduction to further reduce the water-to-cement ratio in the concrete which can increase the strength of the concrete. Strength of air entrained concrete reduces 5 percent for every 1 percent of entrained air.