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Showing 1-5 of 62 Abstracts search results

Document: 

SP179-03

Date: 

June 1, 1998

Author(s):

J. P&a and J. Ambroise

Publication:

Symposium Papers

Volume:

179

Abstract:

Magnesium-phosphate cements, which exhibit fast setting and high early strength, are already used for rapid repairs to damaged concrete. The present paper describes two new applications of them. The first application deals with the development of composites. Magnesium-phosphate cements are typically brittle in nature but their ductility can be significantly improved by addition of fibers. Composites were prepared according to the premix method, the matrix being composed of 50 % of magnesium-phosphate cement and 50 % of sand. Various fibers were used to reinforce the composites, the fiber volume fraction was in the range of 0.69 % to 1.32 %. Very ductile composites were obtained using polypropylene fibers. When subjected to accelerated aging, these composites maintained their initial performances. The second new application of magnesium-phosphate cements concerns the production of durable grouts. Composed of 50 % of magnesium-phosphate cement and 50 % class F fly ash, such grouts behaved well in severe environments like ammonium sulfate, and lactic acid.

DOI:

10.14359/6030


Document: 

SP179-28

Date: 

June 1, 1998

Author(s):

S.I. Pavlenko, A.A. Permyakov and Yu. N. Pronyakin

Publication:

Symposium Papers

Volume:

179

Abstract:

The Siberian State Academy of Mining and Metallurgy together with the joint-stock company of the West-Siberian Metallurgical Works and UralNIIStromproject have developed compositions and technology for fireproof concrete made from local materials and industrial by-products. The concrete is designated for the production of unburnt blocks and bricks to be used for lining heating facilities of metallurgical enterprises (there are four of them in Novokuznetsk). Concrete for producing blocks for soaking pits consists of the following components : quartzite’s of three grading fractions ( 0 to 8 mm - 36 %, 0 to 3 mm - 50 % , powder fraction - 14 % ) and a binder ( technical grade liquid glass ) with a density of 1.42 to 1.44 g/cm' (lo-14 % above 100 % aggregate). The technical grade liquid glass was made by solution of silica fume with the fineness of 60 to 90 m'/g and beyond 90 % free SiOz content in sodium hydroxide. The technical grade liquid glass developed increased the strength of concrete and its heat resistance by 35 to 45 % and 25 to 30 %, respectively, as compared with the commonly used liquid glass. The service life of the blocks manufactured at the pilot plant of the West-Siberian Metallurgical Works in walls of a soaking pit was 18 months while that of the blocks produced by the Pervouralsky plant ranges from 6 to 12 months. The construction of a department for producing blocks and bricks from the above concrete is in the stage of completion at the West-Siberian Steel Works.

DOI:

10.14359/6055


Document: 

SP179-17

Date: 

June 1, 1998

Author(s):

L. Coppola, R. Troli, P. Zaffaroni and M. Collepardi

Publication:

Symposium Papers

Volume:

179

Abstract:

Portland cement contains sulfur compounds from the clinker phase and from added calcium sulfate (e.g. gypsum) which acts as a set regulator. The purpose of this investigation was to study the influence of the sulfate content in the clinker phase on the performance of superplasticized concrete mixtures in terms of initial slump level at a given water-cement ratio (0.49, slump-loss rate, and compressive strength at early and later ages. Two batches (A and B) of clinker from the same kiln source were studied, the main difference being the content of sulfate (SOs) in the clinker (0.72% and 1.40% respectively). Different percentages of natural gypsum, as set regulator, were interground in a laboratory mill to manufacture portland cements: A1 , A2 , A3 from clinker A, and B1 , B2 , B3 from clinker B. Three levels of total sulfate content in terms of SOs were set: 3.0% in portland cements A1 and B1 , 3.5% in portland cements A2 and B2 ; 4.0% in portland cements A3 and B3. At a given sulfate content in portland cement, the lower the clinker sulfate content, the more effective is the slump increase of the concrete caused by the superplasticizer addition. Moreover, the lower is the clinker sulfate content, the lower is the slump-loss rate of the superplasticized concrete mixture. Finally, at a given water-cement ratio, there is a reduction in the compressive strength at early ages (< 3 days) when the low sulfate clinker is used to manufacture portland cements. These results are related to the effect of the clinker sulfate content on the degree of cement hydration: the lower the clinker sulfate content, the lower the early cement hydration in terms of gypsum consumption, ettringite formation, and tricalcium silicate (alite) hydration.

DOI:

10.14359/6044


Document: 

SP179-26

Date: 

June 1, 1998

Author(s):

K.G. Sobolev and S.V. Soboleva

Publication:

Symposium Papers

Volume:

179

Abstract:

The report generalizes the results of wide range investigations of silica fume based superplasticized high- performance concrete. The rules of the strength and rheological behavior of cement silica fume - super-plasticizer systems are discussed. Usage of optimal superplasticizer to silica fume ratio (as 1: 10) allows to obtain ultra-dense packing for super fluid cement paste and provides high-performance properties of concrete. The mathematical models of fresh and hardened high-performance concrete based on processing and computerizing empirical results are created. The models provide a calculation of W/C required for the target compressive strength level up to 130 MPa as well as mixing water quantity for planning slump of 0 - 200 mm. For modelling purpose, concrete slump is considered as a function of aggregates proportioning, and volume and fluidity of cement paste. This approach became a basis of proposed high- performance concrete mixture proportioning method. Further, developing and integration of the mathematical models created a new computer program for high-performance concrete mixture proportioning. The program provides a solution for wide range design and optimization projects. The results of the computer program estimation can be easily transferred to any 3- dimensional plotting or data base program for consequent processing and performing.

DOI:

10.14359/6053


Document: 

SP179-24

Date: 

June 1, 1998

Author(s):

F. Curcio, D. Galeota, A. Gallo and M. M. Giammatteo

Publication:

Symposium Papers

Volume:

179

Abstract:

A comprehensive experimental program was designed in order to investigate the mechanical and durability properties of high performance lightweight concrete. The concrete mixture was prepared in order to obtain a specific value of the compressive strength at 28 days of age (fCz75MPa). Testing was carried out on a large number of lightweight concrete specimens. The following properties were investigated: compressive, flexural and splitting-tensile strength, modulus of elasticity, fracture parameters, concrete-steel bond properties, drying shrinkage and durability properties. The test results show that high-performance lightweight concrete has considerable potential for the precast/prestressed industry.

DOI:

10.14359/6051


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