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International Concrete Abstracts Portal

Showing 1-5 of 1022 Abstracts search results

Document: 

SP-350_12

Date: 

November 1, 2021

Author(s):

Iman Mansouri, Chang-Hwan Lee, and Paul O. Awoyera

Publication:

Symposium Papers

Volume:

350

Abstract:

TUBEDECK, a one-way spanning voided composite slab, has been utilized in the construction field over the years to enhance the efficiency, constructability, and environmental performance of structures. TUBEDECK incorporates both cast-in-situ reinforced concrete slabs and profiled steel decks. However, there is a need to clarify the shear resistance capacity in this slab because the shear strength of the member reduces as concrete volume is eliminated to optimize flexural strength. Therefore, this study applied the artificial neural network (ANN) technique to determine the shear strength of TUBEDECK. By varying factors in the ANN features, several ANN models were developed. Out of many models developed, an optimal model was selected, having a maximum/mean relative errors of 5.1% in a dataset.


Document: 

SP-349_04

Date: 

April 22, 2021

Author(s):

Angélique Barneoud-Chapelier, Youssef El Bitouri, Nathalie Azéma, Gwenn Le Saout

Publication:

Symposium Papers

Volume:

349

Abstract:

Belite-Ye’elimite-Ferrite (BYF) cements have been recently developed in order to substitute ordinary Portland cement (OPC), as they release up to 30 % less CO2 and their performances tend to be similar. This work aims to give a first insight and understanding on the influence of a lignosulfonate plasticizer (LS) on the hydration and the properties of a BYF cement paste. For this purpose, hydration of neat cement paste (w/c=0.4) was followed by isothermal calorimetry associated with in situ XRD for the first 4 hours. In addition, plasticizer adsorption was investigated using TOC measurements. Rheological and compressive strength tests were also performed. The results showed that LS changes the hydration kinetics, modifying both induction period (that becomes shorter for low dosage and longer for higher dosage) and rate of ettringite precipitation. For all dosages used, LS decreases the heat of hydration and the compressive strength in the first day. Also, its impact on particle surfaces improves their dispersion and causes a diminution of the shear stress of cement paste, allowing better workability.


Document: 

SP-349_13

Date: 

April 22, 2021

Author(s):

Gonzalo A. Lozano Rengifo, Mayra T. de Grazia, Leandro F. M. Sanchez, and Edward G. Sherwood

Publication:

Symposium Papers

Volume:

349

Abstract:

Reducing Normal Portland Cement (NPC) has been a major concern of concrete industry and research community over the last 2-3 decades. As much as 8% of the global CO2 emissions stem from clinker production. Hence, a wide number of research projects have been focusing on reducing NPC in cementitious materials using numerous strategies such as the use of supplementary cementing materials (SMC’s), limestone fillers (LF) and/or advanced mixproportioning techniques. Yet, the impact of these procedures on the overall behaviour of materials with low NPC content, especially in the fresh state and long-term durability, is still not fully understood. This work aims to understand the influence of the distance between the fine particles, the so-called Inter-Particle Separation (IPS), on the fresh state behaviour of cement-base pastes designed through the use of Particle Packing Models and incorporating LF. Evaluations on the fresh (i.e. rheological behaviour and setting time) and hardened states (compressive strength) were conducted in all mixtures. Results show that IPS directly correlates with the viscosity of cementbase pastes for all shear rates appraised. Moreover, the use of LF increases the hydration rate of NPC pastes. Finally, it is clear that the water-to-cement ratio keeps being the main factor controlling the compressive strength of cement pastes with reduced NPC content and high levels of LF replacement.


Document: 

SP-348_05

Date: 

March 1, 2021

Author(s):

O.S. Ali Ahmed

Publication:

Symposium Papers

Volume:

348

Abstract:

Dynamic pile group effect can either increase or decrease the response of pile-supported structures. This paper presents the results of a three-dimensional finite element model of the pile-to-pile interaction that considers the effect of the surrounding soil to determine the dynamic stiffness and damping for vertical end bearing pile groups subjected to vertical harmonic loading. The results were generated for a wide range of the dimensionless frequency parameter (ao) for a 9x9-pile group with three different spacings: 2-, 4-, and 6-pile diameter. Both the stiffness and the damping showed an oscillatory behavior with the dimensionless frequency parameter ao, as well as with the soil shear modulus. Also, the group efficiency was determined as a function of the pile spacing and the soil shear modulus. The efficiency factor for the stiffness can be as high as 1.15 and as low as 0.7 and for the damping as high as 3.75 and as low as 0.4 as a function of the dimensionless frequency parameter ao.


Document: 

SP-347_06

Date: 

March 1, 2021

Author(s):

Thong M. Pham, Tin V. Do, and Hong Hao

Publication:

Symposium Papers

Volume:

347

Abstract:

This study experimentally and numerically investigated the impact responses of reinforced concrete (RC) beams with a rectangular hollow section (HCB) in comparison with a rectangular solid section (SCB). Experimental tests of the two types of RC beams were firstly conducted under the drop-weight impact of a 203.5-kg-solid-steel projectile. Numerical models of the beams under impact loads were then developed in the commercial software namely LS-DYNA and carefully verified against the experimental results. The numerical models were then used to investigate the stress wave propagation in the two beams. The effect of the top flange depth, contact area, and impact velocity on the impact responses of the beams was also investigated. The experimental and numerical results in this study showed that although the two beams were designed with similar reinforcement ratio, their impact responses were considerably different, especially when the shear failure dominated the structural response. The HCB exhibited a smaller peak impact force but higher lateral displacement than the SCB when these beams were subjected to the same impact condition. Besides, more shear cracks were observed on the HCB while that of SCB has more flexural cracks. Furthermore, the decrease of the top flange depth of the hollow section and the increase of the impact velocity changed the failure modes of the two beams from flexural failure to shear failure with concrete scabbing. The change of the contact area also shifted the failure mode of the beam from global response to direct shear, inclined shear, punching shear and concrete scabbing at the top flange of the section close to the impact location.


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