Experimental study of the punching shear behavior of high performance steel fiber reinforced concrete slabs considering casting directions

© 2016 Elsevier Ltd This paper presents the results of an experimental study on the punching shear behavior of high performance steel fiber reinforced concrete (HPFRC) slabs without shear reinforcement, particularly considering the effect of fiber orientation. In recent decades, high performance steel fiber reinforced concrete (HPFRC) has been a new achievement in concrete technology. Due to its superior mechanical properties, civil engineers can address the problem of punching shear of thin slabs that are currently widely used in buildings. By processing some studies, researchers have found that the strength capacity of the material before cracking and the post-cracking resistance strongly depend on the orientation of the fibers, which heavily rely on the casting direction and casting method. While most previous studies focused on the effect on the behavior of beams, this research particularly considers how the casting procedures as well as the volume content of the fiber affect the punching shear behavior of flat slabs

Effects of Fly Ash Composition to Mitigate Conversion of Calcium Aluminate Cement Composites

Calcium aluminate cement (CAC) is one of the alternative cements that is widely used for special applications. However, during the hydration process degradation of CAC microstructure, the so-called hydrate conversion process, hexagonal calcium aluminate hydrate (CAH10) transforms into a cubic (C3AH6) phase, resulting in increased porosity and reduced strengths. It is known that alternative means for stabilizing the CAC conversion are conducted by introducing fly ash (FA) in CAC, where its microstructure is attributed to aluminosilicates. However, no study has yet been conducted on different FA compositions influencing CAC performance. This study aims to evaluate the effects of different compositions of FA on CACs’ fresh and hardened characteristics. Results revealed that the microstructure was denser when CAC was mixed with FA. Regarding reactivity, CAC with calcium-rich FA systems is 13% faster than the silica-rich one. The higher the density and the lower the porosity of calcium-rich FA mixtures were found compared with silica-rich FA in both micro- and macro-structures. As seen in the microscopic structure, this is due to the calcium-rich phase formation

Fire resistance performance of reactive powder concrete columns

© 2018, Chulalongkorn University. All rights reserved. This paper experimentally explores the fire resistance of reactive powder concrete (RPC) columns with varying steel and polypropylene (PP) fiber content. RPC is a concrete composition with the highest developed compressive strength and is incorporated with steel fibers that can improve the tensile strength and ductility of RPC structures. The fire resistance of RPC structures, however, has been disputed by engineers and researchers. Four columns with different weight contents of fiber were tested in fire for 30 and 60 minutes with a load applied afterwards. Then, the performance of RPC columns in elevated temperature was investigated, focusing on spalling depth, failure mechanism in fiber and residual strength. The results showed that increasing the volume fraction of steel fiber or the presence of PP fiber improves the fire resistance of the columns. However, the columns lost significant cross-sectional area and load capacity. With the knowledge that this research would provide, a better understanding for making decisions could be developed

Shear capacity of high performance fiber reinforced concrete I-beams

© 2017 Elsevier Ltd An experimental program was carried out to investigate the shear capacity of High-Performance Fiber-Reinforced Concrete (HPFRC) I-beams. The main parameters were assigned as the fiber content and presence of shear reinforcement. To study the effect of these main parameters on the shear capacity, testing of six I-beams and other control specimens was conducted. It can be observed from the results of the experimental study that the presence of fibers and shear reinforcement significantly improves the ultimate capacity and structural behavior of HPFRC members. Finally, the experimental results are discussed, and the shear capacity of HPFRC can be estimated by extending the code provisions stated in AFGC-Sétra 2013

Optimization of tensile strain-hardening cementhious composites for tensile strain capacity

The synergistic action of a cementitious matrix and fibres can result in strain hardening in tension. The accompanied tensile strain capacity can be an important design parameter for strain-hardening cementitious composites in order to prevent the localization in a single crack and to assure that the stress is at least the tensile strength o f the unreinforced matrix. Such a behaviour is desired for example for bridge decks or joints where the strain-hardening material has to follow the deformations of either the substructure or that of the total structure. An experimental study was executed in order to determine the tensile strain capacity of cementitious composites. As a start of the study, a reference mixture developed at the University of Michigan was chosen. Adjusted mixtures in three different compressive strength classes and straight fibres of two different lengths were applied. The six mixtures were tested on characteristics in the fresh and in the hardened state. This paper discusses experimental results and observed failure pattems. The tensile strain capacity was the highest for the lowest compressive strength and with longer PV A-fibres applied.Structural EngineeringCivil Engineering and Geoscience