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Showing 1-10 of 90 Abstracts search results

Document: 

SP132-89

Date: 

May 1, 1992

Author(s):

C. Alfes

Publication:

Special Publication

Volume:

132

Abstract:

In High-Strength Concrete in general high-quality aggregate is used. This aggregate has a high compressive strength and often a high modulus of elasticity. This high modulus of elasticity of the aggregate strongly influences the deformation behaviour of high-strength concrete. Results show that there is a direct and linear relationship between the shrinkage value and the modulus of elasticity of the concrete. The highest modulus of elasticity of concrete was 85 GPa. The compressive strength at the age of 28 days was in the range from 102 to 182 MPa. A design aid is given to show the interrelation between modulus of elasticity and shrinkage strain of the concrete on one side and modulus of elasticity of the aggregate, modulus of elasticity of the matrix and matrix content on the other side.

10.14359/17148


Document: 

SP132-88

Date: 

May 1, 1992

Author(s):

J. Hrazdira

Publication:

Special Publication

Volume:

132

Abstract:

Gypsumless Portland cements (GPC) are inorganic binders, which may be described aas system of: ground Portland clinker (specific surface of 400-500 m2/kg - Blaine), a surface-active agent with hydroxyl groups and a hydrolyzable alkali metal salt (carbonate, bicarbonate, silicate). New cements, developed in recent years, are able to reach both higher strengths and fracture toughness than ordinary Portland cement (1,2,3). New developments in the making of very strong cements have resulted from modifying cement compositions and manipulating the microstructures (4).

10.14359/17147


Document: 

SP132-87

Date: 

May 1, 1992

Author(s):

M. Tamai and Y. Nishiwaki

Publication:

Special Publication

Volume:

132

Abstract:

Purpose of this study was to search for ecologically acceptable ways to stimulate the natural self-purification activities in water areas. For this purpose, attachment of marine organisms to the surface of no-fines concrete (NFC), which contains continuous voids that may be effective in promoting establishment of a biologically favorable environment, was examined. When this type of concrete is immersed in shallow seawater, not only its rough surface, but also its continuous interior voids, are fully exposed to water and rapidly neutralized. This will then lead to the attachment and growth of marine microbes and eventually to the formation of a layer of biotic membranes. Attachment of organisms seems to occur in a form of multilayered biotic membrane consisting of bacteria, various microbes, unicellular algae, small animals, large seal algae, and shellfish, etc. Results show that decomposition and ineralization of the marine organic matters and the growth of algae, attached animals, and bacteria are accelerated, thereby providing the water area with a better biological environment. Thus, this type of concrete may be useful in the establishment of a well-balanced biological environment and, although there is a limitation due to its thickness, in the construction of gathering places for fish. In addition, assimilation and fixation of carbon dioxide by attached algae and shellfish, respectively, may be also possible.

10.14359/2244


Document: 

SP132-86

Date: 

May 1, 1992

Author(s):

S. Kashima, M. Sakamoto et.

Publication:

Special Publication

Volume:

132

Abstract:

The Akashi Kaikyo Bridge, with a center span of 1990 m, will be the world's longest suspension bridge when it is completed in 1998. The two main tower foundations are being constructed in water. A total volume of about 500,000 m3 of antiwashout underwater concrete has been placed, and about 180,000 m3 of ordinary reinforced concrete is currently being placed. Since this antiwashout underwater concrete had to be placed over a wide area and placed about 10,000 m3 per pour, it was necessary to choose a low-heat, high-flowability concrete. The cement used for this antiwashout underwater concrete was a three-component type containing about 80 percent granulated blast furnace slag and fly ash. Report describes the physical properties and workability of the antiwashout underwater concrete and the results of construction.

10.14359/2234


Document: 

SP132-85

Date: 

May 1, 1992

Author(s):

W. Brylicki, J. Malolepszy, and S. Stryczek

Publication:

Special Publication

Volume:

132

Abstract:

The lining of underground cavities for storage of natural gas requires a proper cementing paste as does the cementing of casing in boreholes placed in salt beds. The following properties of the cementing pastes are required: high corrosion resistance, minimal shrinkage, even some expansion, high leak tightness, good bond to steel and rock, proper rheology and strength. The following blended cements were investigated: cement "Nowa Huta" 25 with 40% blast-furnace slag (bfs), cement "Rejowiec" 45 for bridge construction and cement with 70% bfs. The cements were mixed with NaCl brine at a concentration 310 g NaCl/L at liquid to solid ration 0.45. The properties of pastes, such as density, rheological, sedimentation and filtration characteristics; time of setting; strength development and shrinkage were determined. The phase composition of pastes was studied by XRD and the microstructure was observed under SEM. The best results were obtained for the pastes with the blast-furnace slag.

10.14359/2212


Document: 

SP132-84

Date: 

May 1, 1992

Author(s):

K. Fukudome, K. Miyano, H. Taniguchi, and T. Kita

Publication:

Special Publication

Volume:

132

Abstract:

The resistance to freezing-and-thawing and chloride diffusion of antiwashout underwater concrete was investigated to evaluate the applicability for tidal zone in cold districts or reinforced concrete structures in marine environments. Comparisons were made with ordinary portland cement concrete of similar mix design. Two types of cement (ordinary portland cement and portland blast furnace slag cement) were used. Two types of blast furnace slag (Blaine fineness 500 and 700 m²/kg) were used as a cement replacement (slag content 30 and 50 percent by weight). The results show that antiwashout underwater concrete without blast furnace slag shows poor resistance to freezing-and-thawing compared with normal concrete. But the freezing-and-thawing resistance can be improved with blast furnace slag. This is due to the fact that concrete containing blast furnace slag has dense pore structures. Pore volume in the range of 10 to 10 3 nm in radius decreases significantly with blast furnace slag. Similarly, chloride diffusion depth becomes smaller with blast furnace slag.

10.14359/2220


Document: 

SP132-83

Date: 

May 1, 1992

Author(s):

D. Baweja, H. Roper, S. Guirguis, and V. Sirivivatnanon

Publication:

Special Publication

Volume:

132

Abstract:

The background to a major study into the corrosion characteristics of steel reinforcement within portland and blended cement concretes is presented. The objectives of this work included an investigation into relationships between chloride-ion concentration and the onset and rate of steel corrosion in concrete. Corrosion activity of steel reinforcement within concrete specimens was measured using procedures including half-cell potential, resistivity, and potentiodynamic anodic polarization. A total of four binder types that included a slag-blended cement and a fly ash-blended cement were used. Chlorides were introduced into the concrete specimens subsequent to casting and curing by partial immersion into salt solutions. The development of a procedure to electrochemically measure the corrosion rate of steel in concrete slab specimens partially immersed in chloride solutions is described. Some of the data obtained using this procedure are discussed in relation to measured half-cell potentials for slab specimens. Based on information available to date, assessments were made regarding the relative marine durability performance of the various binder types considered. Obtained half-cell potential data were analyzed with respect to the time taken to reach -350 mV (versus Cu/CuSO 4), a value where there is a 95 percent probability of corrosion activity as defined by ASTM C 876. Using statistically based procedures, it was found that concrete water-binder ratio was the major influence on the time taken for half-cell potentials to reach -350 mV. The binder type also had a significant influence on the time taken for potentials to reach -350 mV. Considering concretes cast at equal water-binder ratios, half-cell potentials for reinforcement with slag-blended cement concretes took longer to reach -350 mV when compared with other binders tested.

10.14359/1238


Document: 

SP132-82

Date: 

May 1, 1992

Author(s):

John P. H. Frearson and Denis D. Higgins

Publication:

Special Publication

Volume:

132

Abstract:

Various researchers have reported that the sulfate resistance of portland blast-furnace slag cements was reduced when the slag contained a high alumina content. Much of this testing has used much higher water-cement ratios for the test specimens than are normally used in construction. In this study, the mixtures have been modified to assess mortars additionally at lower water-cement ratios. The test program used the German "Flat-Prism" test to assess blends of cement and various combinations of two slags: one slag of low alumina content, and the other slag with a higher alumina content. Results of expansion testing up to an age of 4 years are reported and indicate that when used at the replacement levels and water-cement ratios specified in current U.K. standards and codes of practice, both slags can provide resistance to sulfate expansion. At higher water-cement ratios and lower slag replacement levels, expansion does occur. Commercial blends of the two slags, when used to optimize other properties (e.g., strength), would not compromise the sulfate resistance properties. The greatest sulfate resistance, as represented by the lowest expansion, was not provided by the slag with the lowest alumina content, but by a composite slag sample with an alumina level of about 13 percent.

10.14359/1237


Document: 

SP132-81

Date: 

May 1, 1992

Author(s):

Shinobu Ozaki and Noriyuki Sugata

Publication:

Special Publication

Volume:

132

Abstract:

Compressive fatigue strength of concrete in a submerged condition deteriorates drastically compared with concrete in an air-dried condition. One of the reasons for the lowering of fatigue strength in submerged or wet concrete appears to be the influence of the reduction of the bond at the interface between the aggregate and the cement paste. However, this reduction may be mitigated by reducing the calcium hydroxide content and filling the voids at the interface. In this study, compressive fatigue tests were performed in submerged conditions using concrete composed of blast furnace slag or silica fume. The 2-million-cycle fatigue strength of this submerged concrete improved up to 44 percent of its static strength in water compared to 31 percent for ordinary concrete in water. However, this was found to be smaller than 56 percent for ordinary concrete in air. During these tests, the pH of the water in the test tank and the strain of the specimens were measured, and the amounts of calcium hydroxide that oozed out from the specimen and the strain behavior were investigated. The increase in fatigue strength is due to an improvement in the aggregate interface bond and watertightness. However, the expansion of cracks just before failure, which is a distinct characteristic of fatigue in water, was not checked.

10.14359/2282


Document: 

SP132-80

Date: 

May 1, 1992

Author(s):

K. E. Philipose, J. J. Beaudoin, and R. F. Feldman

Publication:

Special Publication

Volume:

132

Abstract:

Corrosion of reinforcement is one of the major degradation mechanisms of reinforced concrete elements. The majority of studies published on concrete-steel corrosion have been conducted on unstressed specimens. Structural concrete, however, is subjected to substantial strain near the steel reinforcing bars that resist tensile loads, which results in a system of microcracks. Report presents the initial results of an investigation to determine the effect of applied load and microcracking on the rate of ingress of chloride on and corrosion of steel in concrete. Simply supported concrete beam specimens were loaded to give a maximum strain of about 600 æî on the tension face. Chloride ion ingress on cores taken from loaded specimens was monitored using energy-dispersive x-ray analysis techniques. Corrosion current and rate measurements using linear polarization electrochemical techniques were also obtained on the same loaded specimens. Variables investigated included two concrete types, two steel cover depths, three applied load levels, bonded and unbonded reinforcing steel, and the exposure to tension and compression beam faces to chloride solution. One concrete mixture was made with Type 10 portland cement, the other with 75 percent blast furnace slag, 22 percent Type 50 cement, and 3 percent silica fume. The rate of chloride ion ingress into reinforced concrete and hence the time for chloride ion to reach the reinforcing steel is shown to be dependent on applied load and the concrete quality. The dependence of corrosion process descriptors--passive layer formation, initiation period, and propagation period--on level of applied load is discussed.

10.14359/2271


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