Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : steel fibers

Nonlinear Finite Element Analysis of Fiber Reinforced Concrete Slabs

Saad A. Al-Taan; Ayad A. Abdul-Razzak

Engineering and Technology Journal, 2021, Volume 39, Issue 3A, Pages 426-439
DOI: 10.30684/etj.v39i3A.1641

This paper presents a study on the behavior of fiber reinforced concrete slabs using finite element analysis. A previously published finite element program is used for the nonlinear analysis by including the steel fiber concrete properties. Concrete is represented by degenerated quadratic thick shell element, which is the general shear deformable eight node serendipity element, and the thickness is divided into layers. An elastic perfectly plastic and strain hardening plasticity approach are used to model the compression behavior of concrete. The reinforcing bars were smeared within the concrete layers and assumed as either an elastic perfectly plastic material or as an elastic-plastic material with linear strain hardening. Cracks initiation is predicted using a tensile strength criterion. The tension stiffening effect of the steel fibers is simulated using a descending parabolic stress degradation function, which is based on the fracture energy concept. The effect of cracking in reducing the shear modulus and the compressive strength of concrete parallel to the crack direction is considered. The numerical results showed good agreement with published experimental results for two fibrous reinforced concrete slabs.

Effect of Steel Fibers, Polypropylene Fibers and/ or Nanosilica on Mechanical Properties of Self-Consolidating Concrete

Iqbal N. Gorgis; Maan S. Hassan; Rana T. Abdulkareem

Engineering and Technology Journal, 2016, Volume 34, Issue 3, Pages 527-538

This research concerned studying the combined effect of using nano-silica and/ or hybrid fibers on key mechanical properties of self-consolidating concrete SCC. A comprehensive experimental work has been carried out, using steel fiber (SF) with volume fraction (0, 0.5% and 1.5%), polypropylene fiber (PPF) (0%, 0.05% and 0.15%) and SiO2 nanoparticles (0%, 2% and 4%) by weight of powdered material (silica fume- Sf ) with constant w/c ratio (0.48) to produce eleven different mixtures and tested at different ages (7, 28 and 90 days).
Results showed that adding fibers adversely affect SCC workability and thus more dosage of super plasticizer (SP) should be added to stay within the standard limits. comparable to conventional concretes, the presence of steel fibers with SCC provide slight increase in compressive strength at 28 days, (up to 11%), while significant enhancement in tensile properties were observed (up to 24% and 32% for splitting and flexural strength respectively). Polypropylene or hybrid fibers however, provide lower enhancement compared with steel fibers. In contrast, implementation of nanosilica leads to significant improvement in concrete strengths particularly at 4% dosage. Combined effect of 4% nanosilica and 1.5% of steel fibers provide the superior hardening effect on the flexural performance compared with softening effect provided by other added dosages. Scanning Electron Micrograph (SEM) images confirm the matrix densification effect due to nanosilica adding. Flexural strength of SCCs without nanosilica was generally higher than splitting testing results. This fact does not change even with the presence of nanosilica and/ or fibers.

Fresh and Hardened Properties of Steel Fiber-Reinforced Self-Consolidating Concrete

Maan S. Hassan; Iqpal N. Gorgis; Aymn H. Ali

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 1213-1225

The main aim of this research is to study the effect of using hooked end steel fiber on the fresh and hardened properties of self-consolidating concrete. The experimental work includes two stages. First stage involved conducting several trial mixes and then choosing the one that conform tothe international standards in terms of fresh properties. Second stage concerned on the compressive, flexural tensile and splitting tensile strengths evaluationof the selected mixes, at 28 and 90 days.Four concrete mixes were obtained and evaluated. They were similar in mix proportions and differ only in volume fractions of steel fibers incorporated: 0%, 0.5%, 1%, and 1.5%.
Results showed that adding hooked steel fibers adversely affect SCC workability and thus more dosage of SP should be added to stay within the standard limits. Similar to conventional HPC, the presence of steel fibers with SCC provide slight increase in compressive strength at 28 days, (up to 11%), while significant enhancement in tensile properties were observed (up to 68% and 80% for splitting and flexural strength respectively). Flexural strength (i.e. modulus of rapture) was generally still higher than splitting testing results in a decreasing order. This order is still applicable in SCC even with the presence of steel fibers.

Predicting the Strength of Fiber Reinforced High Performance Concrete Based on Push-Off Tests

Maha M.S. Ridha; Nagham T. Hamad; Kaiss F. Sarsam

Engineering and Technology Journal, 2012, Volume 30, Issue 7, Pages 1187-1202

This paper reports the results of an investigation into the strength of fiber reinforced high-performance concrete (FRHPC)based on push-off tests. Both experimental and analytical studies were performed. In the experimental study, eight FRHPC push-off specimens were tested. Two types of fibers, straight and hooked-end, in conjunction with percentage of volume fraction of steel fibers,0.5%, 1.0%, 1.5% and 2.0% were used. In the analytical study, a new proposed expression was derived based on experimental data in this research and available data from the literature. These include high strength concrete (HSC) with
compressive strength of 40 < f'c < 107 MPa. The investigated variables were, fibers factor (F), area of reinforcement perpendicular to shear plane (ρvfy), and concrete compressive strength (f'c). The proposed expression gave good prediction for the direct shear strength of the tested specimens-the proposed expression predicted the direct shear stress resistance of tested/calculated values with a coefficient of
variation (COV) of 12.88 percent.

Effect of Fibers on Some Engineering Properties of Cement and Lime Stabilized Soils

Suhail A. Khattab; Ibrahim M. Al-Kiki; Abderrahmane H. Al-Zubaydi

Engineering and Technology Journal, 2011, Volume 29, Issue 5, Pages 886-905

Recently, many attempts were made to use metal fiber reinforcements to
improve some soil properties. In this research, the effects of fibers on the
compaction and mechanical properties of cement and lime stabilized soils (silty
and clayey soils respectively) were studied. Variables such as stabilizer (cement
and lime) content, amount and type of metal fibers were studied. Results indicated
that the addition of fibers lead to increase in the maximum dry unit weight. On the
other hand, a maximum values of unconfined and tensile strength were obtained
with the addition of 0.5 % short fiber (FS) and 1.5 % long fiber (FL) respectively.
During the flexural test a brittle manner failure was observed for the unreinforced
samples and samples prepared with little amount of fibers 0.5%. Finally, the
addition of fibers increases the fracture energy of cement stabilized silty soil and
lime stabilized clayey soil.

Mechanical Properties of High-Strength Fiber Reinforced Concrete

Zaid Muhammad Kani Al-Azzawi; Kaiss Sarsam

Engineering and Technology Journal, 2010, Volume 28, Issue 12, Pages 2442-2453

Experimental results of this work in addition to a wide range of data from previous work
were analyzed to study the mechanical properties and strength of high-strength concrete with and
without fibers. Different types of steel fibers (straight, hooked, duoform, crimped) with a volume
fraction ranging from 0 to 2 percent were studied. The concrete compressive strength ranged from 41
to 115 MPa. The influence of fiber on the compressive strength, axial strain, modulus of elasticity,
Poisson's ratio, modulus of rupture, and splitting tensile strength, were studied. In addition to that,
size effect of control specimens on high-strength fiber reinforced concrete materials, was observed.
The main conclusion indicates that high-strength concrete (HSC) properties, especially with fibers
are significantly different from normal-strength concrete (NSC).

Effect of Super Plasticizer on the Properties of Pre-cast Concrete Flags Reinforced by Steel Fibers and Including Slag

Qais J. Frieh; Bassam A. Aljabbar

Engineering and Technology Journal, 2007, Volume 25, Issue 10, Pages 337-352
DOI: 10.30684/etj.2007.173033

This research has studied the possibility of optimizing some of the properties of the precast concrete flags by using by-products of steel fragments from the CNC machines and local slag, the combined influence of these materials
with the water reducing agent. The local slag is produced by the blast furnace from the scrap as a raw material, which is called (steel slag). The local slag has a low activity as a cementicious material due to low content of glass since it has not been treated, and contains high ferrous ratio. The study includes the results of compressive and strength as well as transverse loading tests. Also, it includes the measurements of absorption on different curing durations of the reference concrete samples and concrete contains the metal and chemical additives, reinforced by steel fibers. This study has taken place by replacing the slag instead of fine aggregate, using ratios of (0, 10, 20, 30%) by weight of sand with the influence of steel fibers from the CNC by-products, using ratios of (0.5, 1.0, 1.5 %) by volume of the concrete mix with the influence of super plasticizer of (1.5%) ratio by weight of cement. The results had shown that the concrete compressive strength had increased with using (30%) of slag and (1%) of steel fibers of the CNC machine by- product, with (1.5%) of the super plasticizer, compared with the reference mixes. The results had shown also, that the concrete containing super plasticizer with slag (20%) and (1.0%) of the steel fibers had shown better flexural strength compared with the reference mixes at ages (7, 28 days). The results had also shown increasing in the transverse loading test of the pre cast concrete flags, especially when using slag of (30%) and steel fibers of (1%) and super plasticizer, compared with the reference mixes at ages (7, 28 days). The results had shown clear reduction of the absorption at slag ratio (30%) and (1.0%) of steel fibers with the super plasticizer, compared with the reference mixes at age (28 days).