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International Concrete Abstracts Portal

Showing 1-5 of 133 Abstracts search results

Document: 

20-278

Date: 

May 1, 2021

Author(s):

Dong Li, Liu Jin, and Xiuli Du

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

The concept of global size effect theory from material level to structural level is raised. The material level is described by a Universal Morphological Model (UMM) that accounts for the size effect behaviors introduced by the mixture variables of concrete, whereas the structural level is linked to the size effect theory based on quasi-brittle fracture mechanics. First, the UMM that is eligible for the description of material-level size effect is established and verified. Parametric study on the UMM shows that the mechanical properties of concrete are insensitive to the maximum aggregate size (MAS) at a critical interface crack index ηc. Secondly, by introducing the UMM into the formulation of structural-level size effect, a global size effect model (GSEM) expressed as a variant for the Type-2 size effect model (SEM) is proposed. Parametric study on the GSEM shows that the properties and the scales of mesostructures have significant influences on the size effect behaviors of concrete at the structural level. The critical interface crack index ηc determined by the UMM should receive sufficient attention in large-scale structural concrete design in practice.

DOI:

10.14359/51730425


Document: 

19-435

Date: 

November 1, 2020

Author(s):

Xun Xi, Shangtong Yang, Xiaofei Hu, and Chun-Qing Li

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

The interfacial transition zone (ITZ) between cement mortar and aggregate significantly affects the cracking behavior of concrete. However, the fracture properties including the tensile strength and fracture energy of ITZ are hard to obtain directly from experiments. This paper develops an inverse numerical method for determining the fracture properties of ITZ based on a meso-scale fracture model and artificial neural network. Concrete is considered a multi-phase material, mainly consisting of aggregates, cement mortar, and ITZ. In the fracture model, cohesive elements are inserted in the mesh to achieve arbitrary cracking. The tensile strength and fracture energy of ITZ are the targeted variables to be inversely attained. A neural network is created and trained based on the simulated results, by which the optimized values of the targeted variables are obtained. Experimental results from RILEM tests are used to validate the numerical method.

DOI:

10.14359/51728123


Document: 

19-459

Date: 

November 1, 2020

Author(s):

N. Saklani, B. M. Khaled, G. Banwat, B. Spencer, A. Giorla, G. Sant, S. Rajan, and N. Neithalath

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

Numerical implementation of an isotropic creep-damage model for concrete in multiphysics object-oriented simulation environment (MOOSE) finite element framework is presented in this paper. The constitutive model considers the combined effect of instantaneous and delayed strains on damage propagation. The implementation considers creep using generalized Maxwell or Kelvin-Voigt models. Using strain splitting assumptions, the total mechanical strains are split into elastic and creep components. Damage is considered to evolve as a function of the elastic and creep strains. This work considers damage as a function of fracture energy using the characteristic length of each finite element. This approach preserves the energy release rate of each element and avoids vanishing energy dissipation as the mesh is refined. A creep-damage parameter is used to quantify the effect of creep strain on damage. The model is tested against published results on notched three-point bending specimens involving non-linear creep and predicts that about a third of the creep strain contributes towards damage for the experiments simulated. Results show that the proposed framework has predictive capabilities, and the model can be extended for more complex systems.

DOI:

10.14359/51729312


Document: 

18-217

Date: 

May 1, 2019

Author(s):

Leo Barcley and Mervyn Kowalsky

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

The fracture of longitudinal reinforcing steel causes the loss of load-carrying capacity in reinforced concrete (RC) members. Results of large-scale reverse cyclic column tests have indicated that the fracture of longitudinal reinforcement is influenced by the amount of buckling experienced by the reinforcing steel. Similar behavior was observed in a material test as reinforcing bars fractured in a brittle manner when pulled in tension after buckling. Brittle fracture occurred after the bending strain from buckling exceeded the critical bending strain. A material test was developed to quantify the critical bending strain, called the buckled bar tension test. The rib radius of the reinforcing bar was found to influence the magnitude of the critical bending strain. Additionally, the results of column tests indicated that the critical bending strain of the longitudinal reinforcement affected the column displacement capacity. Finally, a relationship between axial displacement and strain from bending was developed.

DOI:

10.14359/51715583


Document: 

18-139

Date: 

March 1, 2019

Author(s):

Jiaqing Wang, Qingli Dai, Shuaicheng Guo, and Ruizhe Si

Publication:

Materials Journal

Volume:

116

Issue:

2

Abstract:

The reinforcement effects of four types of fibers on rubberized concrete were investigated. The fiber-reinforced rubber concrete specimens were produced with added 0.5% fiber based on the mixture volume, and 10% recycled tire rubber by the fine aggregate volume. The mechanical properties and shrinkage performance were evaluated and compared with the control rubber-only concrete samples. The results showed steel fibers could improve compressive, splitting tensile, and flexural strength, while synthetic fibers reduced the compressive and flexural strength as compared with control samples. However, all fiber-reinforced specimens dramatically improved fracture energy and post-crack extension compared with control specimens, especially the fracture energy, which increased approximately 10 to 50 times. The pullout resistance of different fibers was not influenced by added rubber. At the same time, the fiber-reinforced rubber concrete also showed reduced shrinkage. In summary, the performance of rubberized concrete could be effectively enhanced by fiber reinforcement, which can help to facilitate the applications of rubberized concrete.

DOI:

10.14359/51712266


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