Effects of Silane Treatment of Steel Fibres on Mechanical Properties and Durability of SFRC

Fibre reinforced concrete (FRC) has become an alternative for structural applications due its outstanding mechanical properties. The appearance of new types of fibres and the fibre cocktails that can be configured mixing them has created FRC that clearly exceed the minimum mechanical properties required in the standards. Consequently, in order to take full advantage of the contribution of the fibres in construction projects, it is of great interest to have constitutive models that simulate the behaviour of the materials. This study aimed to simulate the fracture behaviour of five types of FRC, three with steel hooked fibres, one with a combination of two types of steel fibres and one with a combination of polyolefin fibres and two types of steel fibres, by means of an inverse analysis based on the cohesive crack approach. The results of the numerical simulations defined the softening functions of each FRC formulation and have pointed out the synergies that are created through use of fibre cocktails. The information obtained might suppose a remarkable advance for designers using high-performance FRC in structural elements.

Download Full-text

Studies on Hemp and Recycled Aggregate Concrete

International Journal of Concrete Structures and Materials ◽

10.1186/s40069-020-00429-6 ◽

2020 ◽

Vol 14 (1) ◽

Author(s):

Samer Ghosn ◽

Nour Cherkawi ◽

Bilal Hamad

Keyword(s):

Mechanical Properties ◽

Fiber Length ◽

Plain Concrete ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Silane Treatment ◽

Hemp Fiber ◽

Fiber Treatment

Abstract This paper reports on the first phase of a multi-phase research program conducted at the American University of Beirut (AUB) on “Hemp and Recycled Aggregates Concrete” (HRAC). HRAC is a new sustainable concrete material where hemp fibers are incorporated in the mix, the coarse aggregate content is reduced by 20% of the concrete volume, and 50% of the natural coarse aggregates (NCA) are replaced by recycled concrete aggregates (RCA), thus saving on natural resources and addressing the problem of waste material disposal. The effect of the new material on concrete consistency and hardened mechanical properties was studied. Also, few durability tests were conducted. Variables included percentage replacement of NCA by RCA (0 or 50%), maximum size aggregate (10 or 20 mm), hemp fiber length (20 or 30 mm), and hemp fiber treatment (alkali or silane or acetyl). Fiber characterization tests were conducted including morphology, crystallinity, and thermal analysis. The tests indicated that alkali and acetyl fiber treatments were better than the silane treatment in removing impurities on the fiber surface. Also, alkali and acetyl treatments have increased the crystallinity of the fibers while silane treatment decreased it. Results of mechanical properties tests showed that while HRAC has considerable lower compressive strength and modulus of elasticity than plain concrete, the flexural strength and splitting tensile strength are not significantly affected. The flexural stress–strain behavior of HRAC is ductile as compared to the brittle behavior of the plain concrete beams indicating positive impact on toughness and energy dissipation. The durability tests indicated that whereas HRAC mixes have higher absorption than plain concrete, they have better thermal properties and their resistance to freeze–thaw cycles is comparable to plain concrete. All test results were not significantly affected by fiber length or fiber treatment.

Download Full-text

Effect of silane treatment on mechanical properties and thermal behavior of bamboo fibers reinforced polypropylene composites

Journal of Engineered Fibers and Fabrics ◽

10.1177/1558925020958195 ◽

2020 ◽

Vol 15 ◽

pp. 155892502095819

Author(s):

Qianting Wang ◽

Yu Zhang ◽

Weikang Liang ◽

Jianjie Wang ◽

Youxin Chen

Keyword(s):

Mechanical Properties ◽

Thermal Behavior ◽

Functional Groups ◽

Mechanical Test ◽

Fiber Composite ◽

Silane Treatment ◽

Silane Coupling Agents ◽

Polypropylene Composites ◽

Bamboo Fibers ◽

Pp Composites

In this work, the surface of the bamboo fibers (BF) was treated with three kinds of silane coupling agents terminated with amino functional groups (KH550), epoxy functional groups (KH560), and methyl functional groups (KH570) to improve fiber–matrix adhesion. The effects of silane treatment on the mechanical properties and thermal behavior of BF/polypropylene (PP) composites were investigated. Mechanical test results showed that the order of modification effectiveness was KH570 > KH550 > KH560. KH570 treated fiber composite exhibited the best mechanical properties. The tensile strength and flexural strength of 5 wt% KH570 treatment reached to 36.1 and 54.7 MPa, which were 15.4% and 23.6% higher than those of UBF/PP composites. Simultaneously, the thermal stability increased from 467.0°C (UBF) to 470.6°C (KH-570 treated BF). An increase in crystallization temperature (1.7°C) and a decrease in crystallinity (5.8%) occurred upon the addition of 5% KH570 silanes treated bamboo fibers.

Download Full-text

Mechanical properties and fibre density of steel fibrereinforced self-compacting concrete slabs by DIA and XCT approaches

Journal of Civil Engineering and Management ◽

10.3846/13923730.2016.1217922 ◽

2017 ◽

Vol 23 (5) ◽

pp. 604-612 ◽

Cited By ~ 5

Author(s):

Tomasz PONIKIEWSKI ◽

Jacek KATZER

Keyword(s):

Mechanical Properties ◽

Fibre Length ◽

Research Programme ◽

Experimental Tests ◽

Flexural Behaviour ◽

Mixture Flow ◽

Steel Fibres ◽

Flexural Tensile Strength ◽

Oriented Parallel ◽

Concrete Casting

The aim of the research programme was to investigate flexural behaviour of steel fibre reinforced self-compacting concrete (SFRSCC). The specimens were in a form of slabs reinforced with steel fibres (of three lengths and two shapes) by volumes of 1.0% and 1.5%. Two methods of casting slabs were examined. The experimental tests performed on 80 specimens cut from slabs (1.2×1.2×0.15 m) involved tests of mechanical properties, digital image analysis (DIA), and X-ray computed tomography (XCT) procedures. Determination of distribution of fibres by DIA and XCT was required to assess relationships between mechanical properties and the casting methods. The tests were conducted according to RILEM TC 162-TDF (2002) and EN 14651:2005+A1:2007(E) recommendations. The study confirmed the technological problems associated with uneven distribution of steel fibres in SCC matrix. Based on the performed analysis, the flexural tensile strength of SFRSCC cannot be described with the formulas used for SFRC. Fibres are generally oriented parallel to the direction of concrete mixture flow in a mould. This phenomenon is influenced by fibre length and the location of concrete casting point (CCP). It was also demonstrated that the flexural behaviour of tested elements is influenced by CCP.

Download Full-text

OPTIMIZATION OF UHPFRC BEAMS SUBJECTED TO BENDING USING GENETIC ALGORITHMS

Journal of Civil Engineering and Management ◽

10.3846/13923730.2013.801908 ◽

2014 ◽

Vol 20 (4) ◽

pp. 527-536 ◽

Cited By ~ 5

Author(s):

Goran Ćirović ◽

Vlastimir Radonjanin ◽

Milan Trivunić ◽

Dragan Nikolić

Keyword(s):

Mechanical Properties ◽

Genetic Algorithms ◽

High Performance ◽

Experimental Studies ◽

High Strength ◽

Steel Fibres ◽

Four Point Bending ◽

Steel Bar ◽

Steel Bars ◽

Prestressed Reinforcement

Ultra high performance fibre reinforced concrete (UHPFRC) is cementitious composite with very high strength, and when compared with ordinary concrete it is a more superior material both in terms of its mechanical properties and its durability. In order to predict the behaviour of UHPFRC beams, first of all, experiments were carried out to investigate the mechanical properties of composites containing 2% and 4% of steel fibres. Following this, four beams of 2 m in length were tested by subjecting to four point bending. Two beams contained only micro steel fibres, while the remaining two contained conventional steel bar reinforcement. On the basis of experimental studies and recommendations by the AFGC for UHPC, the behaviour of the beams was modelled and optimization was carried out using genetic algorithms (GA) according to the criterion of minimum price. In this paper, the prices of individual UHPFRC beams are also shown in comparison with beams, which contain steel bars or prestressed reinforcement.

Download Full-text

EXPERIMENTAL RESULTS ON THE SHEAR BEHAVIOUR OF STEEL FIBRE SELF-COMPACTING CONCRETE (SFSCC) BEAMS

Jurnal Teknologi ◽

10.11113/.v78.7221 ◽

2016 ◽

Vol 78 (11) ◽

Author(s):

Juli Asni Lamide ◽

Roslli Noor Mohamed ◽

Ahmad Baharuddin Abd Rahman

Keyword(s):

Mechanical Properties ◽

Steel Fibre ◽

Mechanical Performance ◽

Load Capacity ◽

Shear Behaviour ◽

Self Compacting Concrete ◽

Steel Fibres ◽

Concrete Mixtures ◽

Shear Performance ◽

Better Than

This paper presents an experimental test program that was carried out to investigate the shear performance of steel fibre self-compacting concrete (SFSCC) beams. In this paper, the mechanical performance of results from all mixtures used to cast normal concrete (NC), self-compacting concrete (SCC) and steel fibre self-compacting concrete (SFSCC) were also investigated. In total, 27 cubes, 9 cylinders, 9 prisms and 9 beams were prepared for the assessment of mechanical properties of three different mixtures. Four beams (125 mm x 250 mm x 2200 mm) were tested and cast using three different concrete mixtures, having two different spacing of stirrups as a result of 50% reduction of the stirrups amount. Three beams with different mixtures having similar stirrups spacing 125mm while the fourth beam with SFSCC mixes having 250mm stirrups spacing. The results show that the mechanical properties were positively affected with steel fibres inclusion. The addition of steel fibres showed an increment up to 40% in the shear load capacity for B-SFSCC125 compared to B-NC125 and B-SCC125. In addition, the crack pattern of B-SFSCC was found better than B-NC and B-SCC.

Download Full-text