Asymptotic Analysis of Boundary-Induced Size Dependence of Fracture Properties

2006 ◽  
Vol 324-325 ◽  
pp. 1209-1212
Author(s):  
Kai Duan ◽  
Xiao Zhi Hu
Keyword(s):  
High Strength Concrete ◽  
Size Dependence ◽  
Boundary Effect ◽  
Brittle Materials ◽  
High Strength ◽  
Asymptotic Model ◽  
Fracture Properties ◽  
Asymptotic Boundary ◽  
Effect Model ◽  
Fracture Tests

The recently-developed boundary effect concept and associated asymptotic model are used to explain the size effect phenomena in fracture of quasi-brittle materials. It is demonstrated that the size dependence of the fracture toughness and strength of quasi-brittle materials is indeed due to the influences of specimen boundaries on the failure mode and therefore, on the strength of the specimen. To verify the boundary effect concept, fracture tests on a high strength concrete reported by Karihaloo et al are analysed and predicted using the asymptotic model. The results show that the predictions of the asymptotic boundary effect model agree very well with those experimental results.

Sensitivity of shear strength to fracture energy of high-strength concrete slabs

1998 ◽  
Vol 25 (1) ◽  
pp. 40-50 ◽  
Author(s):  
H Marzouk ◽  
M Emam ◽  
M S Hilal
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
High Strength Concrete ◽  
Shear Failure ◽  
High Strength ◽  
Tensile Fracture ◽  
Concrete Slabs ◽  
Square Root ◽  
Fracture Properties ◽  
Strength Concrete

The test results of an earlier experimental investigation conducted at Memorial University of Newfoundland on high-strength concrete slabs indicated that as the concrete slab strength increased from 35 to 75 MPa the shear strength increased by 7-20%, depending on the case of loading, i.e., concentric or eccentric loads. The increasing ratio of shear strength is less than half that prescribed in the Canadian code CSA-A23.3 (1994) or the ACI-318 code (1995). Hence, the significant difference between the experimental results and the predicted strength by existing North American codes tacitly means that the proportionality between the shear strength and the square root of the compressive strength is not accurate enough to predict the shear strength of high-strength concrete slabs. In the present investigation, a fracture mechanics model suitable for concrete was proposed. It was also suggested that this model might be an advantageous aid in the analysis of the shear failure of reinforced concrete slabs. In this research investigation the fracture mechanics approach utilizing finite element aided computer analysis of several reinforced slabs is briefly described, and calculated shear failure loads are given. The recommended model proves that it is necessary to consider not only the tensile strength of concrete, instead of the square root of the compressive strength, but also the tensile fracture properties of high-strength concrete. The tensile fracture properties of concrete are characterized by the parameter called characteristic length and the brittleness of concrete. The brittleness ratio of concrete slabs must be considered in any rational shear design expression to reflect the size effect factor and the aggregate type.Key words: fracture energy, uniaxial direct tension, shear strength, high-strength concrete, punching shear, slab, size effect, finite element analysis.

Evolution from High Strength Concrete to High Performance Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 49-54
Author(s):  
Vlastimil Bílek ◽  
Vladimíra Tomalová ◽  
Petr Hájek ◽  
Ctislav Fiala
Keyword(s):  
High Strength Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Maximum Size ◽  
Point Of View ◽  
Fracture Properties ◽  
Strength Concrete ◽  
Time Period ◽  
Long Term Observation

High strength concrete for the production of concrete railway sleepers was designed more than 20 years ago. The compressive strength of the concrete was very high from the start, but flexure strengths showed some irregular development - a decrease in time. Later, also a significant decrease of fracture properties was recorded. Microcracking was found to be the reason for this; therefore some modifications were performed to avoid this happening (especially the reduction of the maximum size of aggregates from 22 mm to 16 mm or 11 mm). Some problems concerning frost resistance of the concrete with a slag addition were reduced by applying ternary binders. All of the results are discussed from the point of view of a long-term observation of the strengths and fracture properties ́ development during the time period of 5 years or even more.

scholarly journals Fracture properties of high-strength concrete obtained by direct modification of structure

2017 ◽  
Vol 116 ◽  
pp. 01016 ◽  
Author(s):  
Serhiy Solodkyy ◽  
Taras Markiv ◽  
Khrystyna Sobol ◽  
Oleksii Hunyak
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Fracture Properties ◽  
Strength Concrete ◽  
Direct Modification
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