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International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

Document: 

SP96-09

Date: 

January 1, 1987

Author(s):

D. Whiting, G. W. Seegebrecht, and S. Tayabji

Publication:

Symposium Papers

Volume:

96

Abstract:

Concretes were prepared at degrees of consolidation varying from 100 to 85 percent. Mixtures were typical of those used for pavement applications with cement factors ranging from 520 to 610 pounds per cubic yard (308 to 360 kg/m3) and air contents ranging from 5 to 9 percent. Additional concretes were intentionally overvibrated to the point of incipient segregation. Test specimens were cast for determination of compressive strength, bond of reinforcing steel to concrete, permeability of concrete to chloride ions, and resistance of concrete to freezing and thawing in water. Results show that compressive strength is reduced by about 30 percent for each 5 percent decrease in degree of consolidation. Bond stress is reduced even more dramatically, suffering a loss of approximately 50 percent for 5 percent reduction in degree of consolidation. Overconsolidation has little apparent effect on compressive strength, and may increase bond strength by virtue of displacement of air in these air-entrained concretes.

DOI:

10.14359/2016

Document: 

SP96-05

Date: 

January 1, 1987

Author(s):

Kuo-Ting Lin, Antonio Nanni, and Wen Chang

Publication:

Symposium Papers

Volume:

96

Abstract:

Industrial and mining wastes, often extremely fine-grained, are being used as fillers and binders in structural concrete and consolidation by compaction, as opposed to high-frequency vibration. Impact and static compaction can be industrially used for the automatic production of such building elements as bricks and blocks, whereas roller-compacted concrete is more suitable for field applications. Compressive strength characteristics under air-dry, sealed, and soaked conditions of portland cement mixtures containing a complete range of combinations of dihydrate phosphogypsum (by-product of the phosphate fertilizer industry) and fine aggregate (crushed lime rock) are presented. Cylindrical specimens were prepared according to the Modified Proctor procedure (impact compaction). Based on these results, strength comparisons are made for selected constituent proportions in the cases of: 1) consolidation by static compaction; 2) consolidation by high-frequency vibration; 3) site consolidation by vibratory roller compactor; and 4) substitution of the dihydrate phosphogypsum with the hemihydrate form (other available by-product). It is shown that consolidation by compaction is advantageous because of the contribution of phosphogypsum to strength development. Laboratory-compacted samples of the by-product alone indicate that strengths of over 1000 psi (6.89 MPa) can be achieved. In addition, low-cement (7.5 percent) mixtures using hemihydrate gypsum waste exceed the 4000 psi (27.56 MPa) mark.

DOI:

10.14359/2002

Document: 

SP96-04

Date: 

January 1, 1987

Author(s):

Mikael P. J. Olsen

Publication:

Symposium Papers

Volume:

96

Abstract:

Current consolidation practices and a recently completed laboratory investigation to determine the effects of coarse aggregate factor, maximum aggregate size, vibrator spacing, and the method of vibrator mounting on the achieved consolidation of CRCP is reviewed. The theory and principles of consolidation by internal vibration are also reviewed. Vibrator spacing, concrete mix design, and acceleration in the concrete are parameters found to be important. A vibratory spacing of 24 in. (610 mm) is required to produce adequate consolidation. The concrete mix should contain coarse aggregate with a top size of 1 « in. (40 mm) and a coarse aggregate factor determined by the Fineness Modulus Method of mix design. The superplasticizers with or without retarders have to be used with great caution due to slump loss, making it difficult to consolidate the stiff concrete mixes used in slipformed paving construction.

DOI:

10.14359/1989

Document: 

SP96-01

Date: 

January 1, 1987

Author(s):

Ken Weden

Publication:

Symposium Papers

Volume:

96

Abstract:

The lower the water content of concrete, the stronger, more durable, and less susceptible to shrinkage will be the finished product. Concrete with a low water content generally means concrete with a thick consistency or low slump. When low slump concrete is placed, it is in a honeycomb condition, consisting of mortar-coated coarse aggregate and entrapped air. The amount of entrapped air will vary with different mixes, size, and shape of forms, amount of congestion (reinforcing steel), and the method by which the concrete is placed.

DOI:

10.14359/3493

Document: 

SP96-07

Date: 

January 1, 1987

Author(s):

T. R. Harrell and G. M. Goswick

Publication:

Symposium Papers

Volume:

96

Abstract:

The permeability of a tunnel concrete lining can be significantly affected by the consolidation techniques and procedures used during a concrete placement. Both the density and the durability of the concrete will have an influence on the ultimate permeability of the concrete. Consolidation techniques and procedures that will include both external and internal vibration can be used to aid in obtaining a concrete lining, which may be characterized as slightly permeable. Techniques and procedures used for consolidation of the tunnel lining concrete for the Rocky Mountain Pumped Storage Project are presented and discussed.

DOI:

10.14359/3512

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