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International Concrete Abstracts Portal

Showing 1-5 of 396 Abstracts search results

Document: 

SP-333_03

Date: 

October 1, 2019

Author(s):

Bruno Dal Lago, Davide Bisi and Liberato Ferrara

Publication:

Symposium Papers

Volume:

333

Abstract:

Basalt-Fiber Reinforced Polymer (BFRP) bars have been recently proposed to be used to prestress precast concrete elements. Mechanical properties, potential low production cost, low carbon footprint, and enhanced durability make the application of BFRP to prestressed concrete promising. Nevertheless, some issues related to anchorage and sustained stress still need to be fully addressed. Applications are so far limited to few laboratory tests. This paper discusses how the Serviceability Limit State (SLS) and Ultimate Limit State (ULS) checks of prestressed elements employing this technology vary with respect to elements pre-stressed with steel tendons. Furthermore, an attempt is made to investigate the potential application into the precast concrete industry, by analyzing several typical roof and floor slab elements with different cross-sections. This investigation highlights which type of element could be more advantageously switched to the use of pre-stressed BFRP bars, and at which cost in terms of structural performance.


Document: 

SP327-34

Date: 

November 1, 2018

Author(s):

Marco Rossini, Eleonora Bruschi, Fabio Matta, Carlo Poggi and Antonio Nanni

Publication:

Symposium Papers

Volume:

327

Abstract:

This paper presents a parametric analysis of the ACI 440 (2015) and AASHTO (2009) algorithms governing the flexural design of a one-way concrete member internally reinforced with glass fiber-reinforced polymer (GFRP) bars. The influence of specific design parameters on the required amount of reinforcement is investigated. The aim is to identify variables and requirements governing the design of a large-section GFRP reinforced concrete (RC) member. The member considered for this case-specific analysis is the reinforced concrete pile cap of the Halls River Bridge (Homosassa, FL), which is deemed representative of large-section GFRP-RC members operating as bent caps in short-span bridges. The influence of four critical parameters on the required amount of reinforcement is assessed. Salient analysis and design implications are discussed with respect to creep and fatigue rupture stress limits, minimum amount of flexural reinforcement, and applicable strength reduction factors. The outcomes of the parametric analysis highlight an untapped potential to reduce the required amount of reinforcement, and prioritize research areas to advance the development of rational design algorithms. Cyclic fatigue and creep rupture are identified as governing mechanisms.


Document: 

SP-329-07

Date: 

September 26, 2018

Author(s):

Manuel Ilg and Johann Plank

Publication:

Symposium Papers

Volume:

329

Abstract:

Concretes formulated at low water-cement ratios exhibit good material properties. Nevertheless, such concretes exhibit a honey-like consistency with a low speed of flow (“creeping behavior”) which is highly undesirable. In this paper it is shown that non-ionic small molecules can help to improve the fluidity at low water-cement ratios significantly and eliminate the “stickiness” when combined with ordinary PCE superplasticizers. For this purpose, different non-ionic glycol derivatives were screened via mini-slump testing. It was found that especially less polar species behave as very powerful co-dispersants. To gain a more profound understanding of the working mechanism, heat flow calorimetry was carried out. Additionally, concrete lab tests were performed to ascertain the impact of the non-ionic molecules on the V-funnel empty time of SCCs. Based on adsorption measurements it is inferred that the co-dispersants act as osmotic spacers which keep the cement particles apart and prevent them from agglomeration.


Document: 

SP326-60

Date: 

August 10, 2018

Author(s):

Simon S. Kaprielov, Andrey V. Sheynfeld, Igor A. Chilin, and Igor M. Bezgodov

Publication:

Symposium Papers

Volume:

326

Abstract:

It is known that characteristics of fiber-reinforced concrete generally depend on the volume and properties of the matrix, the type and dosage of fiber. Studies have been conducted on the influence of these factors on strength and deformation characteristics, including the modulus of elasticity, creep and frost resistance of ultra-high strength self-compacting fiber reinforced concrete (UHSFRC).

Portland cement CEM I 52.5, sand with fineness modulus of 2.5, organic-mineral modifier MB-50 and straight steel fiber were used as components for self-compacting concrete. The fiber dosage was varied in the range from 0 to 2.0% of the volume of concrete mixtures.

The tests have shown that the creep of steel fiber reinforced concrete at different levels of loading (0.3 and 0.6 of Rb) is significantly less than that of the matrix. The ratio of transverse creep deformation is significantly lower than under the short-time loading, as for the matrix and the same as for steel fiber reinforced concrete. Despite almost linear diagram of concrete deformation under compression, the value of creep deformation shows quite higher figures. It is noted that the effectiveness of steel fiber increases with the increase of stress level.

Freeze-thaw resistance was evaluated in the cyclic process of freezing at -50°C [-58°F] and thawing in 5% NaCl solution. The test results show very high frost resistance of concrete, what corresponds to the grade F2800, what is 2.7 times above the concrete requirements for transport structures in Russia.


Document: 

SP326-55

Date: 

August 10, 2018

Author(s):

Arne Spelter, Sergej Rempel, Norbert Will, and Josef Hegger

Publication:

Symposium Papers

Volume:

326

Abstract:

Textile reinforced concrete (TRC) is a high-performance composite material made of impregnated filaments and a concrete matrix with a longer service life compared to steel reinforced concrete. Due to the non-corrosive reinforcement it is possible to reduce the concrete cover and realize slender and architectural attractive concrete structures. In addition, resources and CO2-emissions can be saved.

Despite the non-corrosive reinforcement, a loss of strength occurs over the service life due to environmental impacts. Therefore, a testing concept is required to determine a reduction factor that takes the loss of strength during the service life into account. This enables a safe design of textile reinforced concrete structures.

A testing concept for TRC is derived from existing concepts for fiber reinforced polymers (FRP). Available concepts (e.g. ACI 440.3R-12, ASTM 7337, CSA S806-12, ISO 10406-1) differentiate between creep rupture and alkaline resistance. Therefore, a test setup was derived which combines the existing concepts and enables the determination of the long-term durability of non-metallically reinforced concrete structures. The long-term durability is defined as a constant stress on a reinforcement that can be applied during the service life without a failure of the reinforcement.


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