Experimental analysis of steel fiber reinforced concrete beams in shear

Some normative recommendations are conservative in relation to the shear strength of reinforced concrete beams, not directly considering the longitudinal reinforcement rate. An experimental program containing 8 beams of (100 x 250) mm2 and a length of 1,200 mm was carried out. The concrete compression strength was 20 MPa with and without 1.00% of steel fiber addition, without stirrups and varying the longitudinal reinforcement ratio. Comparisons between experimental failure loads and main design codes estimates were assessed. The results showed that the increase of the longitudinal reinforcement ratio from 0.87% to 2.14% in beams without steel fiber led to an improvement of 59% in shear strength caused by the dowel effect, while the corresponding improvement was of only 22% in fibered concrete beams. A maximum gain of 109% in shear strength was observed with the addition of 1% of steel fibers comparing beams with the same longitudinal reinforcement ratio (1.2%). A significant amount of shear strength was provided by the inclusion of the steel fibers and allowed controlling the propagation of cracks by the effect of stress transfer bridges, transforming the brittle shear mechanism into a ductile flexural one. From this, it is clear the shear benefit of the steel fiber addition when associated to the longitudinal reinforcement and optimal values for this relationship would improve results.

Effect of Dietary Fiber and Thermal Conditions on Rice Bran Wax-Based Structured Edible Oils

In this work, extra-virgin olive oil (EVO)- and sunflower oil (SFO)-based oleogels were structured using rice bran wax (RBW) at 10% by weight (w/w). Bamboo fiber milled with 40 (BF40), 90 (BF90) and 150 (BF150) µm of average size was added as a structuring agent. The effect of fiber addition and cooling temperature (0, 4, and 25 °C) on thermal and structural parameters of achieved gels was assessed by rheological (both in rotational and oscillatory mode), texture, and differential scanning calorimetry tests. Oleogelation modified the rheological behavior of EVO and SFO, thus shifting from a Newtonian trend typical of oils to a pseudoplastic non-Newtonian behavior in gels. Moreover, oleogels behaved as solid-like systems with G′ > G″, regardless of the applied condition. All samples exhibit a thermal-reversible behavior, even though the presence of hysteresis suggests a partial reduction in structural properties under stress. Decreasing in cooling temperature negatively contributed to network formation, despite being partially recovered by low-granulometry fiber addition. The latter dramatically improved either textural, rheological, or stability parameters of gels, as compared with only edible oil-based systems. Finally, wax/gel compatibility affected the crystallization enthalpy and final product stability (gel strength) due to different gelator–gelator and gelator–solvent interactions.

Concrete Microstructure Study on the Effect of Sisal Fiber Addition on Sugarcane Bagasse Ash Concrete

Background: Concrete made using sugarcane bagasse ash as a cement replacement is associated with a reduction in split tensile strength and therefore a need to establish the possible causes of tensile strength reduction and explore ways of mitigating that reduction. Objective: The aim of this study is to establish the possible causes of tensile strength reduction in sugarcane bagasse ash concrete and determine the effect of sisal fiber addition on its mechanical properties. Methods: Scanning Electron Microscopy was first done to analyse concrete microstructure in establishing the possible causes of tensile strength reduction in sugarcane bagasse ash concrete. Thereafter, sisal fiber addition was done by varying aspect ratios and percentages. The effect of the addition was determined on the mechanical properties of bagasse ash concrete accompanied by microstructure studies on extracted fibers and split surfaces of concrete. Results: Concrete microstructure studies revealed that wider cracks due to drying shrinkage and poor bonding properties of sugarcane bagasse ash are the possible causes of tensile strength reduction in bagasse ash concrete. Sisal fiber addition improved the mechanical properties of bagasse ash concrete. Microstructure studies portrayed effective bridging of cracks and good adhesive properties of the fibers. Conclusion: Sisal fibers can be used to improve on the mechanical properties of sugarcane bagasse ash concrete with 100 aspect ratio and 1.5% addition being the optimal combination.

Optimization of recycled polyethylene terephthalate plastic bottle fibers in grasscrete

Cement and concrete production account for between 5% to 8% of global CO2. Waste PET plastic and glass waste have also brought about rapid environmental degradation. Glasscrete was developed with glass powder of fewer than 75 microns (has pozzolanic properties) that performed 14% better than concrete at 90 days. So, to further this effort, this experimental research considered the glass create C20 (at 10% cement replacement) and added PET fibers (of aspect ratio 25) at different percentages of 1%, 2%, 3%, and 4% the weight of cement in a bid to optimize the grasscrete performance and its ability to absorb PET waste. Glasscrete being extremely brittle alone, failed by cracking at all percentage PET additions, thus improving its safety factor. A 1% PET fiber addition to grasscrete exhibited the highest strength properties compared to other percentage additions while having a durability of 1.5% better than concrete. It is thus recommended for structural uses as it outperforms concrete. Despite this, a 1% fiber addition decreased grasscrete’s compressive strength by at least 3.5% at 28 days and 6% at 90 days but improved the flexural strength by 5.4% at 28 days and 0.8% at 90 days testing.

Changes in Rheological Properties of Mortars with Steel Slags and Steel Fibers by Magnetic Field

The effect of a magnetic field on the rheology of mortars with steel slags and fibers was evaluated in this study. The rheology of the mortar measured with and without a magnetic field was compared. The effect of steel fiber addition to normal and steel slag mortars, mix ratio and size of steel fibers, and magnetic field formation position on rheology were evaluated. Steel fiber addition increased the yield stress and viscosity of the normal and steel slag mortars. The increased rheology was almost restored because of the magnetic field applied to the normal mortars. However, the increased rheology of the steel slag mortars with steel fibers was restored only upon the application of the magnetic field, whose position was continuously changed by a power relay. It is deduced that the alignment of the steel fibers by the magnetic field contributes to the rheology reduction of the mortars. However, in the case of steel slag mortar, experimental results demonstrated that steel slag, which is a ferromagnetic material, receives constant force by the magnetic field, which increases the rheology. This is evidenced by the decrease in the rheology of steel slag mortars under a continuously changing magnetic field formation position by power relay.

IMPACT STRENGTH TEST ON ADDITION OF AGAVE SISALANA FIBER AND E-GLASS FIBER IN ACRYLIC RESIN DENTAL PLATE REPAIR

Introduction: Acrylic resin is the most common material for the denture base because the acrylic resin has good esthetics, ease of processing, reparability, and inexpensive. A disadvantage of acrylic resin is that it is easy to be cracked. One of the ways to resolve this problem is by adding agave sisalana fiber and E-glass fiber. The purpose of this study was to find out the effect of the addition of agave sisalana fiber and E-glass fiber on the impact strength of an acrylic resin denture plate reparation. Material and Method: The experiment involved twenty-seven plates of heat-cured acrylic with the dimensions of 55x 10 x 10 mm with the 26 x 5 x 4 mm for the cavity to measure, each measurement divided into three groups, with nine samples for each group. The first group was a control group (without fiber), the second group was a group with agave sisalana fiber addition, the third group was a group with e-glass fiber addition. All plates were soaked in distillation water for one day at 37o C. Plates were tested for impact strength using the Charpy method. All data obtained were analyzed with one-way ANOVA followed by LSD (Least Significant Difference) with p<0,05. Result and Discussion: The result showed that the influences of impact strength between without fiber with agave sisalana fiber and E-glass fiber addition on acrylic denture reparation. Acrylic denture reparation in both fibers with concentration 3,3%, agave sisalana fiber has the highest impact strength rather than e-glass fiber. Conclusion: The conclusion of this study is that there is an increase in impact strength with agave sisalana fiber and E-glass fiber addition on acrylic denture reparation and agave sisalana fiber has the highest impact strength.