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Showing 1-5 of 50 Abstracts search results

Document: 

SP173-14

Date: 

September 1, 1997

Author(s):

L ICoppola, C. Pistolesi, P. Zaffaroni and M.Collepardi

Publication:

Symposium Papers

Volume:

173

Abstract:

An acrylic polymer was mixed with fine sand and cementitious binders. The mixtures were studied as rubber-like coating to protect reinforced concrete specimens. Three coatings (all with water-binder ratio of 0.50, polymer-binder ratio of 0.50 and sand-binder ratio of 2) were produced by changing the type of binder: portland cement, pozzolan-portland cement with metakaolin and slag-based cement. The coatings were applied to a porous concrete substrate with a water-cement ratio of 0.80. Preliminary tests on uncoated and coated concrete specimens were carried out to study the penetration of water, carbon dioxide, chloride, and sulphate ions. The resistance to penetration of these aggressive agents was very poor in the uncoated specimens and became as good as that of a watertight and durable concrete in the coated specimens. Coated beam specimens were kept for 24 months in three different environments (laboratory at 20°C and 60% R.H.; outdoors environment exposed to natural changes in temperature and relative humidity; under water) in order to examine the influence of the binder type on the bond strength and the flexibility of the coating in terms of ability to bridge the cracks of the concrete substrate. Bond strength of the coatings was substantially unchanged or improved by the exposure to the three different environments. Initial flexiiity of the coating was improved by the addition of metakaolin or slag. However, at later ages there was some flexibility loss, for coated concrete specimens exposed to water, when portland cement was used specially in the presence of mtakaolin. No flexibility loss was found in the polymer-cement coating in the presence of slag.

DOI:

10.14359/6188


Document: 

SP173-45

Date: 

September 1, 1997

Author(s):

M. C. Santagata, G. Bonora and M. Collepardi

Publication:

Symposium Papers

Volume:

173

Abstract:

The paper examines the rheological and mechanical behavior of super-plasticized microcement grouts to be used for the consolidation of porous systems (e.g. sand deposits, masonry walls of historical buildings). Five microcements were used: they differed in chemical composition of the clinker, type of mineral addition (natural pozzolan or silica fume), and particle size distribution. Three different super-plasticizing chemical admixtures - acrylic, naphtalene, and melamine based - were used, all with an active polymer content of 0.4% by mass of cement. The following properties of the grouts were investigated compressive strength, stability (bleeding test). fluidity (Marsh cone), The acrylic polymer proved to be more effective than the naphtalene and melamine based products in reducing the mixing water to produce a given initial fluidity. Furthermore, the grouts produced with this super-plasticizer displayed a lower fluidity loss with time. The performance of a specific mixture was also strongly dependent on the fineness of the binder and on the type of mineral addition. The compressive strength of the hardened grouts was primarily affected -especially at latter ages - by the water-binder ratio, independently of the type of super-plasticizer. None of the mixtures considered showed any significant bleeding. A limited number of injection tests in columns of dense sand were also performed. For a given water binder ratio, the groutability of a mixture was greatly improved using the acrylic based super-plasticizer in place of the melamine- and naphtalene-based products.

DOI:

10.14359/6219


Document: 

SP173

Date: 

September 1, 1997

Author(s):

Editor: V.M. Malhotra

Publication:

Symposium Papers

Volume:

173

Abstract:

SP173 In October 1997, the Council for the Orginazation of CANMET/ACI Conferences in association with American Concrete Institute and several cement and concrete organizations in Italy sponsored the fifth conference on the subject in Rome, Italy. This conference was aimed at transferring technology in the fastmoving field of chemical admixtures. A total of more than 60 papers from more than 20 countries were received and reviewed by the ACI review panel and 49 were accepted for publication in the proceedings of the conference. The proceedings were published as ACI special publication SP-173.

DOI:

10.14359/14212


Document: 

SP173-34

Date: 

September 1, 1997

Author(s):

M. Collepardi

Publication:

Symposium Papers

Volume:

173

Abstract:

When the historical buildings of the Republic of Venice were erected all the construction materials and the corresponding techniques were always carefully selected. Even at that time architects were aware of the importance of the durability of buildings in a very hostile environment such as that existing in Venice characterized by permanent humid air and capillary rise of salty water from the foundations. In particular cementitious materials were adopted in agreement with the empirical rules of the Romans’ experience and adapted for the particular Venetian environment. The present paper examines two specific cementitious materials which became very popular throughout the world: the stucco plaster and the terrazzo concrete. At the time of the Republic of Venice, chemical admixtures were not available. Therefore, masonry artisans and architects developed a special know-how to manufacture durable materials. This was based on the use of mineral admixtures and natural substances, the invention of innovative binders and the development of special application techniques. After the advent of portland cement and especially of chemical admixtures, modem stucco plaster and terrazzo concrete can be produced with different (not necessarily better) properties and at higher rates of productivity. The present paper examines the microstructural aspect, the composition, the performance, and the manufacturing process of the original and modem materials.

DOI:

10.14359/6208


Document: 

SP173-15

Date: 

September 1, 1997

Author(s):

K. Sakai, H. Watanabe and M. Kinoshita

Publication:

Symposium Papers

Volume:

173

Abstract:

The authors have shown that it is possible to make a concrete with low-heat and high-strength by properly exploiting the potentials of the materials used. The high-range water-reducing air-entraining agent (AE) used played an important role. However, there was a need to reduce the slump loss. A new high-range water-reducing AE agent was developed for this purpose. The agent is a compound of a polycarboxylate type copolymer and a special polymetric surface active agent. This paper describes strength and heat properties of concrete with the developed agent. A moderate heat portland cement and a super-ground granulated blast-furnace slag were used. The test results showed that the newly-developed high-range water-reducing AE agent makes it possible to reduce the slump loss of concrete without losing the properties of low-heat and high-strength. However, it was found that the low-heat property of the developed concrete is lost when the concrete is proportioned to be flowable.

DOI:

10.14359/6189


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