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International Concrete Abstracts Portal

Showing 1-5 of 55 Abstracts search results

Document: 

SP199-50

Date: 

June 1, 2001

Author(s):

V. Corinaldesi and G. Moriconi

Publication:

Symposium Papers

Volume:

199

Abstract:

Concrete specimens were manufactured by completely replacing natural aggregates with recycled aggregates from a crushing plant in which rubble from building demolition was ground. Various concrete was prepared by using silica fume or fly ash as a partial fine aggregate replacement and by using an acrylic polymer based superplasticizer to achieve the prefixed workability. Three types of recycled aggregate concrete were manufactured with the same water/cement (0.40) and the same fresh workability (fluid consistency). A reference concrete was also prepared by using natural aggregates with the same particle size distribution as the recycled aggregate, and having a water/cement of 0.56 and a similar fluid consistency. The results obtained show that because of mineral addition and W/C reduction, recycled aggregates can be used instead of natural aggregates since concretes with similar compressive strength can be obtained. The use of the recycled aggregates with fly ash replacements also has significant cost and environmental advantages over ordinary concrete.

DOI:

10.14359/10553


Document: 

SP199-41

Date: 

June 1, 2001

Author(s):

Takayuki Kojima, Nobuaki Takagi, and Satoshi Horikawa

Publication:

Symposium Papers

Volume:

199

Abstract:

Autogenous shrinkage and drying shrinkage tests were carried out to determine the shrinkage characteristics of high-strength concrete. Three levels of water-cementitious materials ratios [W/(C+SF) : 20, 30 and 50%], and three levels of silica fume replacement ratios [SF/(C+SF) : 0, 7.5 and 15%] were chosen. The drying shrinkage test with specimens of 1 OxlOx4Ocm under the condition of 20+ 1°C and 6O+ 5%RH started at the age of 7 days or 28 days after the measurement of autogenous shrinkage. The autogenous shrinkage strain was also measured in other specimens until the age of about two years. The autogenous shrinkage strain increased both in its amount and its percentage in the total shrinkage strain with the decrease of W/(C+SF). Almost the same total shrinkage strain was observed after about one year in the specimens under the drying condition independent of the mixture proportions of concrete, the curing method or its period.

DOI:

10.14359/10544


Document: 

SP199-16

Date: 

June 1, 2001

Author(s):

K. K. Sideris and A. E. Savva

Publication:

Symposium Papers

Volume:

199

Abstract:

The durability of five mortar and concrete mixtures was investigated in this study. A normal portland cement and four blended cements incorporating different pozzolanic materials, two natural pozzolanas and two lignite fly ashes, were used. The properties measured were compressive strength development, sulfate and chloride resistance as well as the carbonation depth. The results available until the age of 1.5 years show that the replacement of normal portland cement by a pozzolanic material usually has beneficial effects on cement’s durability, especially when the sulfate resistance of mixtures is of primary interest. The carbonation depth of the pozzolanic mixtures was greater than the control’s at all ages up to 1.5 years. Among the four pozzolanic materials examined, the treated lignite fly ash from Ptolemaida gave the best performance in all the tests.

DOI:

10.14359/10499


Document: 

SP199-52

Date: 

June 1, 2001

Author(s):

Ali Akbar Ramezanianpour and Amir Tarighat

Publication:

Symposium Papers

Volume:

199

Abstract:

Corrosion is one of the dominating causes of deterioration of reinforced concrete structures. Carbonation of concrete can initiate the corrosion of reinforcements. Many parameters are affecting the concrete carbonation process. Due to the combination of these parameters, phenomenon of concrete carbonation is very complex. It is therefore necessary to implement numerous experimental works to find the relationship between input and output parameters. These tests are slow and time-consuming. On the other hand t h e great number __ of __ r eq uir ed tests makes the investigations costly. Thus it is worth to use numerical methods as new tools to find the relationships between input and output parameters. Neural Networks are capable of showing the relationships of inputs and outputs even in complex nonlinearity. They can be used even in the cases of little background of the theoretical rules, which govern the phenomenon. Due two these advantages of neural networks, a new model of concrete carbonation (NNCC) have been developed to show the appropriateness of the neural networks in civil engineering fields especially in advanced concrete technology, together with its usage as a new prediction model instead of conventional fitted type models.

DOI:

10.14359/10555


Document: 

SP199-37

Date: 

June 1, 2001

Author(s):

S. Gopalakrishnan, K. Balasubramanian, T. S. Krishnamoorthy, and B. H. Bharatkumar

Publication:

Symposium Papers

Volume:

199

Abstract:

It is now established that the incorporation of industrial byproducts, such as fly ash (FA), ground granulated blast furnace slag (GGBFS) and silica fume (SF), in concrete mixtures as partial cement replacement materials (CRMs) significantly enhances the durability related properties of concrete, besides improving its mechanical properties.. Such concretes are termed as High Performance Concretes (HPCs). In HPC mixtures, it is possible to have low W/C with reduced cement content by judicious choice of mineral and chemical admixtures. The assessment of the flexural behavior of reinforced HPC beams is a subject of ongoing research. Standards and codes of practice differ in the definition of compressive stress block parameters of reinforced HPC beams. Hence, investigations were undertaken at the Structural Engineering Research Centre (SERC), Chennai, to investigate the behavior of reinforced HPC beams under flexural loading. The beam specimens for the test programme were designed as under reinforced, balanced and over reinforced sections as per the guidelines given in the Indian code of practice for reinforced concrete, IS:451 978. The influence of supplementary cementitious materials (SCMs) used as cement replacement materials (CRMs), viz., fly ash (25% as CRM) and GGBFS (40% as CRM), on the flexural behavior of reinforced HPC beams was studied. The paper presents the details of the investigations and discusses the results obtained.

DOI:

10.14359/10540


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