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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP108-02

Date: 

August 1, 1988

Author(s):

S. L. Marusin

Publication:

Symposium Papers

Volume:

108

Abstract:

This paper summarizes the results of permeability studies that have been undertaken since 1979. The research used a test procedure developed during the NCHRP Project 12-19A, "Concrete Sealers for Protection of Bridge Structures", which was reprinted in 1981 as NCHRP Report No. 244. This test method utilizes 10 cm concrete cubes, and chloride ion penetration is determined at 4 depths after 21 days exposure to 15 percent NaCl solution. The test results show that lowering of water-cement ratio in portland cement concrete or presence of superplasticizers, polymer admixtures, and silica fumes are able to significantly reduce concrete permeability.

DOI:

10.14359/2147


Document: 

SP108-01

Date: 

August 1, 1988

Author(s):

J. F. Young

Publication:

Symposium Papers

Volume:

108

Abstract:

The permeability of hardened cement paste is reviewed with particular reference to the influence of pore structure. Permeability is usually modelled by applying D'Arcy's Law, although permeability measurements and pore size distribution determinations reveal the strong influence of large capillary pores (macropores) on flow through cement paste. The macropores form a continuous flow path within the paste. The effects of curing temperature, drying, and admixtures on permeability can be understood in terms of their influence on macropores. Paste containing fly ash shows anomalous behavior, which apparently arises from internal damage occurring during pore structure measurements. It appears that the presence of fly ash promotes the formation of a discontinuous macropore system that inhibits flow.

DOI:

10.14359/2136


Document: 

SP108-07

Date: 

August 1, 1988

Author(s):

B. Mobasher and T. M. Mitchell

Publication:

Symposium Papers

Volume:

108

Abstract:

The new rapid chloride permeability test, in which chloride ions are driven into concrete samples electrically over a 6-hr period, is becoming widely used and has been accepted as an American Association of State and Highway Transportation Officials (AASHTO) standard, T277. This paper summarizes the results of an extensive series of laboratory tests with the new method. Results of an interlaboratory test program provide single-operator and multilaboratory coefficients of variation suitable for use in a precision statement in the standard versions of the method. Several possible revisions to the AASHTO standard procedure are examined, but further study is necessary before any can be accepted. Test results on specimens with diameters other than the standard 3.75 in. (95 mm) called for in T277 are found to be easily adjusted to allow comparisons with standard size specimens. Several fundamental properties of concrete, namely, water-cement ratio, coarse aggregate type and gradation, and air content, are shown to affect chloride permeability.

DOI:

10.14359/3621


Document: 

SP108-05

Date: 

August 1, 1988

Author(s):

G. Vondran and T. Webster

Publication:

Symposium Papers

Volume:

108

Abstract:

Concretes with and without polypropylene fibers were tested to determine their relationship to permeability. This paper focuses on one type of fiber--bundles of fibrillated polypropylene. The bundles open during concrete mixing and separate into millions of multistrand filament fibers. Tests on permeability, cracking, and steel corrosion show reductions in all three when fibrous concretes are compared with conventional concrete at equal water-cement ratios. A new term, "Perm Point," explains the influence of the fibers on permeability. Subsidence cracking over steel reinforcement increases permeability and accelerates corrosion, whereas polypropylene fiber reinforced concrete reduces this phenomenon. Results suggest an interrelationship exists among permeability, cracking, and steel corrosion.

DOI:

10.14359/2175


Document: 

SP108-03

Date: 

August 1, 1988

Author(s):

C. Ozyildirim and W. Halstead

Publication:

Symposium Papers

Volume:

108

Abstract:

The effects of two pozzolanic admixtures, fly ash and silica fume, and a ground-granulated blast furnace slag on the chloride ion intrusion of concretes prepared with low water-to-cementitious material ratios (0.35 to 0.45) were investigated. Results of the rapid permeability test (AASHTO T 277) showed that the resistance of concrete to the penetration of chloride ions increases significantly as the water-to-cementitious material ratio is decreased for the same proportions of solid ingredients. Most concretes with pozzolans or slag exhibited higher resistance to chloride ion penetration than the control concretes containing portland cement as the cementitious material. Results of the 90-day ponding test (similar to AASHTO T 259), which was conducted with 0.40 w/c concretes only, indicated minimal chloride content at depths below 3/4 in. (19 mm) for all the test concretes. Strength values for all concretes made with the pozzolans and slag at 90 days were in excess of 5000 psi (34.5 MPa), which is satisfactory.

DOI:

10.14359/2158


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