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International Concrete Abstracts Portal

Showing 1-5 of 797 Abstracts search results

Document: 

SP-349_17

Date: 

April 22, 2021

Author(s):

Hugo Valido Deda, Leandro Francisco Moretti Sanchez, Mayra Tagliaferri de Grazia

Publication:

Symposium Papers

Volume:

349

Abstract:

Although the 28-day concrete compressive strength is often used as a quality control indicator, early-age mechanical properties are becoming more critical to optimize construction scheduling. Numerous advanced techniques have been proposed in this regard and among those, electrical resistivity (ER), a non-destructive and inexpensive technique able to characterize the microstructure development of cementitious materials has been showing promising results. Yet, recent literature data have evidenced that ER might be significantly influenced by a variety of parameters, such as the binder type/amount and aggregates nature used in the mix. These factors can hinder the practical benchmark of concrete mixtures proportioned with distinct raw materials. Thus, six concrete mixtures incorporating two types of aggregates (granite and limestone) and two ground granulated blast furnace slag cement replacements (e.g. 0%, 35%, and 70%) were manufactured for this research. Moreover, three distinct ER techniques (e.g. Bulk, Surface, and Internal) and compressive strength tests were performed at different concrete ages. Results show that the binder replacement may significantly affect ER results over time, whereas the aggregate type presented a less significant impact.


Document: 

SP-349_16

Date: 

April 22, 2021

Author(s):

Hocine Siad, Mohamed Lachemi, and Mustafa Sahmaran

Publication:

Symposium Papers

Volume:

349

Abstract:

This paper studies the use of a new preconditioning process for an accelerated testing of concrete resistance against sulfate attack. For this reason, concrete specimens were subjected to a part by part pre-saturation method using a concentrated sulfate solution drained inside desiccators. This preconditioning technique was applied before exposing the specimens to different immersion conditions in 5% and 10% sulfate solutions, and to storing at high temperature and to wetting/drying cycles. Length change measurements and sulfate penetration profiles were performed on normal and high strength concretes. In addition, SEM-EDS analysis were used to investigate the type and amount of degradation products in the core layer of samples exposed to accelerated testing. The new pre-saturation method highly accelerated the degradation of concrete samples exposed to different immersion conditions. The microstructural observations showed advanced depths and greater amounts of gypsum and ettringite within the degraded specimens subjected to the primary preconditioning stage. However, the real field observations were only achieved when combining the pre-saturation method and the immersion in 5% sulfate solution.


Document: 

SP-349_36

Date: 

April 22, 2021

Author(s):

Emmanuel Guillon and Catherine Bouillon

Publication:

Symposium Papers

Volume:

349

Abstract:

The industrialization of Super Sulphated Slag Cement requires a strict control of the activation of slag. Optimal activator content is a compromise between early age and long term strengths. In particular, an excessive activator dosage leads to a strong decrease of final strength that could lead to non-conformities. Thanks to the coupled use of mechanical testing, SEM and isothermal calorimetry, this paper provides a clearer insight on how SSSC reacts. It is shown that excess of activation impacts mechanical strength twofold. First, it is observed after one or two days of hydration a decrease of hydration kinetics that could be attributed to a denser or thicker hydrate layer around slag particles. Second, overactivated SSSC exhibit heterogeneous porosity including defects that leads to a decrease of strength and lower mechanical efficiency. Finally, this paper highlights that the increase of strength observed when using hemihydrate is mainly due to the improvement of hydration kinetics, more than a gypsum setting effect.


Document: 

SP-348_07

Date: 

March 1, 2021

Author(s):

Pericles C. Stivaros and Pablo A. Bruno

Publication:

Symposium Papers

Volume:

348

Abstract:

This paper presents a case study involving the structural analysis and design of an elevated foundation plinth to support multiple pieces of rotating machines with different operating weights and speeds. The equipment is used to operate a high-speed balancing testing facility for turbines and rotors that are located within an adjacent testing chamber. This project comprised of several layout and design challenges, including vibration and resonance concerns, effects of multiple operating frequencies, plinth shape, and pile foundation effects. Major concern was to maintain the high precision and strict tolerance limitations required by the high-speed balancing operations. Elevated machine foundations integral with other structures possess many natural frequencies, both locally and globally. The traditional design rules-of-thumb are not adequate for analyzing and designing elevated machine foundations. A computer-based finite element analysis method is required to identify the multiple natural frequencies of a complicated foundation structure. The strength design of a machine foundation can become very challenging when trying to implement code requirements that are mostly applicable to building elements and not to massive concrete foundations. This study recognizes the need for the development of a design standard to include special design requirements for mass concrete machine foundations.


Document: 

SP-347_11

Date: 

March 1, 2021

Author(s):

Victor Lopez, Mi G. Chorzepa, and Stephan A. Durham

Publication:

Symposium Papers

Volume:

347

Abstract:

This paper presents the drop-weight impact performance of recycled tire chip and fiber-reinforced cementitious composites. Emphasis is placed on maximizing the energy dissipation capacity of rubberized fiber reinforced concrete (FRC) mixtures subjected to impact forces for the purpose of improving the impact resilience of concrete elements such as concrete traffic barriers and other applications. The first part of this study involved smallscale testing of preliminary mixtures to optimize compressive strength, modulus of rupture, and impact resilience using a fixed percentage of tire chip replacement of the coarse aggregate and varying volume fractions of steel, polypropylene, and polyvinyl alcohol fibers. Rubberized FRC beams were then tested under static loads to maximize the static energy dissipation potential of steel fiber inclusion at varying tensile steel reinforcement ratios. The final part of this study involved performing scaled drop-weight impact tests on reinforced concrete beam. Results confirmed that rubberized and/or fiber reinforced cementitious composite members exhibit significantly improved energy dissipation capacity and impact resilience, particularly with 1.0% steel fiber addition and 20% tire chip replacement. It was observed that more energy was dissipated through the steel fiber addition alone than FRC mixtures with the tire chips.


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