Enhancement Of Compressive Strength Research Articles

Mechanical Properties of Steel Fiber –Waste Marble Aggregate Concrete

In this research, the enhancement of compressive, tensile and flexural strength of concrete mixtures was explored using both waste white marble instead of aggregate and steel fibers. White marble was mixed with an ordinary Portland cement replacing the mixture of both coarse and fine aggregate by 10%, 50% and 100% of weight. Besides adding the steel fibres to mixture with a total volume of concrete up to 2%. At the age of 28 days of curing, a significant increase of 24.3%, 34.5% and 38.8% was noticed in compressive, tensile and flexural strengths respectively for the replaced aggregate mixtures. Further improvement was gained by adding the steel fiber.

Experimental Investigation on Compressive Strength Enhancement of Geopolymer Paste Fly Ash/ Slag Based Cured at Ambient Condition

Experimental Investigation on Compressive Strength Enhancement of Geopolymer Paste Fly Ash/ Slag Based Cured at Ambient Condition

The impact of slag fineness on the reactivity of blended cements with high-volume non-ferrous metallurgy slag

Non-ferrous metallurgy slags, when highly amorphous, have been shown to behave as supplementary cementitious materials, albeit typically with low reactivity. Due to this feature, high-volume replacement of ordinary Portland cement (OPC) with non-ferrous metallurgy slag is not encouraged. A classical method of increasing slag reactivity is by increasing the fineness of the slag, and this was investigated in the present work. To do so, a non-ferrous metallurgy slag was milled to specific surface areas of 4500 cm2/g and 6500 cm2/g, as determined by the Blaine permeability method. The influence of the fineness on the slag reactivity was investigated using the RILEM R3 isothermal calorimetry procedure. Results demonstrated that the reactivity of these slags was similar to that observed for siliceous fly ashes and increases with slag fineness. Moreover, isothermal calorimetry on blends of OPC with 30, 50 and 70 wt% slag of both finenesses was conducted to investigate the reaction kinetics. A retarding effect of the slag on the Portland clinker hydration was observed, which became more pronounced for higher slag fineness. Finally, mortar compressive strength was tested at 2, 7 and 28 days and compared with the calorimetric results and with thermogravimetric analysis, used to determine the bound water content, at 28 days. At late ages, the increased reactivity for higher slag fineness led to more bound water in hydration products and consequently higher compressive strengths. Moreover, strength gain at later ages due to higher slag fineness might compensate for strength loss due to higher replacement levels. However, at early ages, the strength remained low and increased slag fineness did not yield significant compressive strength enhancement; early strength enhancement likely requires different activation methods.

Enhancing strength and plasticity of Zr-based bulk metallic glasses by Zr partially substituted Fe and isothermal annealing

Zr-based bulk metallic glasses (BMG) Zr65+xCu17.5Fe10-xAl7.5 (x = 0, 2.5, 5, 7.5) with high zirconium content were prepared by an injection copper-mold casting method. The influence of Zr partially substituted Fe and isothermal annealing on the microstructure and mechanical properties of the Zr65+xCu17.5Fe10-xAl7.5 BMGs has been systematically studied. The as-prepared BMG with a Zr content of 70 at.% achieves superior glass forming ability with a large supercooled liquid region width of 82 K and compressive performance. An optimized isothermal annealing (0.5 h) below the glass transition temperature of the as-cast Zr70Cu17.5Fe5Al7.5 BMG contributes significant enhancement in compressive fracture strength and plasticity, from 1845 MPa and 7.4% (as-cast) to 2096 MPa and 12.7% (annealed), respectively. The result of the present study provides a new strategy for designing high-performance BMG-based alloys.

Thermal Exposure of Fly Ash-Metakaolin Blend Geopolymer with Addition of Monoaluminum Phosphate (MAP)

Recent research reveals that formulation of blended geopolymers based on the association of two aluminosilicate precursors had a better performance than one precursor geopolymers. This study presents a facile method to enhance the compressive strength of fly ash-metakaolin blend geopolymer by incorporating monoaluminum phosphate (MAP) during the geopolymerization reaction. The effect of the thermal exposure on the microstructure and compressive strength of the geopolymer are investigated. Results show that the MAP is transformed to granule structures, bonded and surrounded by geopolymer gel. The unique microstructure increases the compressive strength of the room temperature curing geopolymer from 54.7 MPa to 64.21 MPa (14.8%) with an optimum addition of 1.0 wt% MAP. This enhancement in compressive strength was ensured by the formation of an amorphous structure of aluminosilicophosphate (SiO2.Al2O3.P2O5.nH2O) phase. At higher temperatures, the formation of stable crystalline phase of berlinite and nepheline contribute to strength retention of the geopolymer. Hereby, it can be concluded that the addition of 1.0wt% MAP in the geopolymer reinforced the structure.

Mechanical and Microstructural Characteristics of Self-Healing Bacterial Concrete

Concrete is a major part of construction material in the world. The major drawback of concrete is easily cracks by low tensile strength. The innovative technology of introducing bacteria in the concrete to self-remediating of cracks in concrete. Formation of calcium carbonate in the crack surface due to the improvement of crack sealing performance. This current study focus on self-healing development of concrete. An MICCP (Microbiologically Induced Calcium Carbonate Precipitation) technique is an occurrence in managing the concrete cracks. Three different cell concentration of bacillus subtilis bacteria (20×105, 20×106 and 20×107 cells/ml) were introducing in concrete specimen, to find the optimum concentration of bacteria cell. From the optimum cell concentration the crack width measurements are carried out at the age of 7 days, 14 days and 28 days respectively. To calculate the crack width by two (Wet &Dry) different methods of healing agents were used. Microbial concrete have that enhancement of compressive and tensile strength. The formation of calcium carbonate was observed and visualized by scanning electron microscopy (SEM). Chemical composition of sample analyzed by energy dispersive spectrometer (EDS). Identification and quantification of bacterial concrete observed by X-ray diffraction (XRD)

Influence of Calcium Bentonite Addition on the Compressive Strength, Efflorescence Extent and Drying Shrinkage of Fly-Ash Based Geopolymer Mortar

ABSTRACT The influence of calcium bentonite addition on the compressive strength, efflorescence extent and drying shrinkage of fly-ash based geopolymer mortar was investigated. The results showed that appropriate amount (e.g. 15 wt%) of calcium bentonite addition favoured the enhancement of compressive strength mainly because its addition allowed the geopolymer to tolerate more water glass addition and therefore increased the Si/Al ratio of geopolymer. The maximum 28 d compressive strength of the geopolymer mortar with calcium bentonite addition reached 47.8 MPa, which was evidently larger than the maximum value of the specimen without calcium bentonite addition. Calcium bentonite addition was also beneficial for the reduction of drying shrinkage percentage of geopolymer mortar due to water adsorption and volume expansion properties of calcium bentonite. Moreover, calcium bentonite addition could reduce, even eliminate the efflorescence mainly due to Na+ adsorption by calcium bentonite through ion exchange.

Evaluating the performance of rGO/cement composites for SHM applications

Reduced graphene oxide sheets (rGO) have unparalleled physical characteristics that make them effective reinforcing materials. This article explore the effect of rGO on mechanical properties, pore size distribution, micro-structural characteristics and self-sensing properties of the hardened cement paste. The rGO were introduced to net cement paste at different percentages of 0, 0.01, 0.02, 0.03, 0.04 and 0.05 wt% of cement. Compressive strength was measured at 28 days of hydration. The rGO sheets were characterized by high-resolution transmission electron microscope (HRTEM) and Raman spectroscopy. The rGO/cement composites were characterized by Thermo-gravimetric analysis (TGA) pore size distribution and scanning electron microscopy (SEM). Finally; peizoresistive measurements have been performed to study the self-sensing properties of rGO/cement composites. The obtained results revealed that, considerable enhancements in compressive strength by about 27 and 38% were achieved by incorporating 0.04 rGO and 0.05% rGO, into cement matrix respectively. The integration of rGO into cement has significantly reduced the pore size of the rGO–cement composites and led to a considerable improvement in the microstructure. Based on the obtained results, the rGO-cement composites can be efficiently used as piezoresistive sensors.

Compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete reinforced with hybrid fibers

The axial compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete (LWAC) with short carbon fiber and/or polypropylene fiber was investigated. Thirty cylinders with different concrete types (normal weight concrete and LWAC), fiber types (carbon fiber, polypropylene fiber, and mixture of these two fibers), volume faction of fibers (from 0% to 0.4% for each fiber type in single and hybrid form), and spacing between CFPR straps (0 mm, 30 mm, and 50 mm) were experimentally studied. The compressive strengths of CFRP-confined LWAC were improved to 1.01–1.51 times the unconfined strength, and LWAC showed less enhancement in compressive strength provided by confining pressure compared with normal weight concrete. The increase in spacing between CFRP straps declined the confining effect. Addition of carbon fiber in both single and hybrid form positively affected the toughness of CFRP-confined LWAC, while the polypropylene fiber showed few influences on properties of LWAC. Models for the peak stress and corresponding strain were established by collected and present test data. Then theoretical stress-strain model was developed by combining iterative calculation of ascending portion and close-form formula of descending branch. The proposed model showed good match to the test results.

Physical and mechanical properties of sawdust cement mortar treated with hypochlorite

In this study properties of cement mortar containing sawdust have been studied. Different percentages of sawdust have been used as (10%, 20%, 30%, 40%, 50%) of the total volume of dry contents. Sawdust used has been collected as a by-product of carpentry factories and has been used in three ways: first pure sawdust second treated with hypochlorite without washing and the third is treated with hypochlorite and washed with water and dried. Compressive strength test has been performed at 7 days and 28 days, while flexural strength, dry density and absorption have been performed at 28 days. The results showed an enhancement of compressive strength, decrease in dry density and absorption for the mortar containing treated and washed sawdust with the increase of sawdust content in the mixture.

Production of polycarboxylate-ether superplasticizer (PCE) coated sand with modified hardened properties in cement mortar

In this study, the improvement of fine aggregate properties used in cement mortars is presented. Natural river sand was coated with polycarboxylate-ether (PCE) superplasticizer to produce modified coated sand. The addition of PCE superplasticizer was selected to be 7.5%, 15% and 22.5% by weight of sand. In addition, cement mortar mixes were prepared by replacement of natural sand with polycarboxylate-ether superplasticizer (PCE) coated sand at 10%, 30% and 50% by weight. Effects of the various types of coated sand (CS1, CS2 and CS3) on the properties of hardened cement mortar considering the above mentioned replacement percentages were examined. The results indicated that the PCE coated sand contributed in producing mixes with modified properties. For instance, compressive strength enhancement was observed at testing ages of 7 and 28 days. The PCE superplasticizer acted as a coating layer, which was verified through scanning electron microscopy to indicate the superior engineering properties of cement mortar.

Effect of the addition of TiO2 nanoparticles in alkali-activated materials

Nowadays, alkali-activated binders have become one of the most viable options in the reduction of CO2 emissions; receiving considerable attention due to favorable mechanical properties and low energy consumption. Following from that, the effect of addition of TiO2 nanoparticles in alkali-activated binders based on metakaolin and ground granulated blast furnace slag on the mechanical properties, microstructure, formation of new reaction phases, and self-cleaning properties, was analyzed. The results indicated that synthesized materials showed an enhancement in compressive strength obtaining the best results with 0.5% of TiO2, furthermore, self-cleaning properties showed a slight modification in the presence of the nanoparticles.

Hydrophobic modification of ultra-high-performance fiber-reinforced composites with matrices enhanced by aluminum oxide nano-fibers

Aluminum oxide nanoparticles can be used in small quantities to create a high-performance and ultra-high-performance cementitious composites. High volumes, up to 20% of supplementary cementitious materials such as silica fume or metakaolin, are often used to achieve the high strength of up to 150 MPa in high performance and ultra-high performance cementitious composites. This research demonstrates that when aluminum oxide (Al2O3) nano-fibers are used in cement-based composites, compressive strength of up to 175 MPa can be achieved at very low dosages of silica fume and metakaolin. This effect is achieved by using low water to cementitious materials ratio, selection of cement, and utilizing the seeding and reinforcing effects of by the nano-fibers. Furthermore, the ultra-high performance cement-based composite (UHPC) can include polyethylene fibers which provide enhanced strain hardening and multi-cracking behavior. The UHPC was tested to evaluate the effects of superhydrophobic modification. Superhydrophobic modification utilizes siloxane-based admixtures to form a well-dispersed air void system whose voids have hydrophobic properties. The experimental results demonstrate that a superhydrophobic modification may reduce the performance of advanced composites with Al2O3 nano-fibers. High-performance cementitious materials are critical for the next generation of infrastructure. This research evaluates the effects of superhydrophobic admixtures in ultra-high-strength fiber-reinforced composites with Al2O3 nano-fibers. The incorporation of small quantities of aluminum oxide nano-fibers in UHPC may prove to be a viable option for compressive strength enhancement; however, incorporating a superhydrophobic air void structure was not effective for enhancement of ductility.

Study on the Interaction between Low-Viscosity High-Permeability Pregrouting Sealing Material and Coal and Its Application

In order to ensure the intactness of pressure-measuring boreholes and the accuracy of gas pressure determination, pregrouting treatment with polymer materials is frequently applied to bedding drilling in coal mines. However, the existing polyurethane materials are of high viscosity, low permeability, and poor safety, bringing great difficulties to their field promotion and application. In view of this problem, after optimization and experiments, polylactide polyol/polyether polyol 4110/isocyanate was determined as the target system. Bio-based benzoxazine (Boz-F), red phosphorus, and melamine with a mass ratio of 2 : 1 : 2 were used as the flame retardant, which then underwent mechanical modification by hollow glass bubbles. Finally, the pregrouting material with low viscosity and high permeability was compounded, and its interaction with coal was experimentally studied. The results show that compared with traditional polyurethane, the new material increases the effective consolidation distance in the coal seam by 40% on average. Its permeation radius is also larger than the calculated radius of the plastic softening zone of a borehole. In addition, the strengths of coal-new material consolidated products with different ratios fully surpass those of coal-polyurethane material consolidated products. The enhancement of compressive strength and bending strength is up to 153% and 161%, respectively. The field application indicates that after pregrouting treatment of boreholes in the coal seam with the new material, the borehole formation rate reaches 100%. Therefore, the new material is safe and practical for gas pressure measurement through bedding drilling on site.

Physicochemical and biological assessment of flowable resin composites incorporated with farnesol loaded halloysite nanotubes for dental applications

The aim of this study was to fabricate flowable resin composites, by incorporating Farnesol loaded Halloysite Nanotubes (Fa-HNT) as a filler and evaluate their physicochemical as well as biological properties. Chemical and morphological characterization of antibacterial filler, Fa-HNT were performed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM). The antibacterial filler was mixed into composite material consisting of methacrylate monomers and dental glass fillers at concentrations of 1–20% (wt./wt.). It was observed that addition of mass fractions of Fa-HNT causes enhancement of compressive strength as well as flexural modulus of the composite. However, it significantly decreases flexural strength and degree of conversion. A significant antibacterial activity of dental composite was observed with increase in the area of zone of inhibition against the strains of Streptococcus mutans (S. mutans). There was no cytotoxicity observed by Fa-HNT resin composites on NIH-3T3 (mouse embryonic fibroblast cells) cell lines. A favourable integration of antibacterial filler with significant mechanical properties was achieved at concentrations from 7 to 13 wt% of Fa-HNT in dental composites, which is desirable in dentistry.

Structural, Microscopy Analysis and Compressive Strength of ZnO–CuO Nanocomposites

Currently, researches on nanocomposites become an active research area due its unique properties. Earlier, many researches are done for synthesizing the multidimensional structures for developing efficient and new Nano devices. In this present work, we synthesized ZnO–CuO nanocomposites using sol–gel method. The obtained nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) analysis and Compressive strength analysis using compressive testing machine (CTM). Herein, the structure and size of the ZnO–CuO nanocomposites were studied using XRD. And the average particle size was found to be 34 nm. The TEM analysis has the evidence of the XRD result. The enhancement in compressive strength of the ZnO–CuO nanocomposites was determined using CTM machine up to 4 wt.%.

Interactive buckling in prestressed stayed beam-columns

The instability of beam-columns with crossarms and externally prestressed cable stays is studied analytically, where the combination of bending and compression is assumed to be derived from the system self-weight acting orthogonally to the applied axial load. A nonlinear analytical model for prestressed stayed beam-columns with doubly-symmetric and mono-symmetric configurations, based on the Rayleigh–Ritz method, is presented that captures modal interactions for perfect geometries explicitly for the first time. It is demonstrated that the theoretical compressive strength enhancements under certain configurations can only be obtained at the expense of triggering a sequence of destabilizing bifurcations. This can give rise to severely unstable interactive post-buckling behaviour including the so-called ‘mode jumping’ phenomenon. Moreover, for mono-symmetric stayed beam-columns, it is shown that the varying levels of prestress within the stays can lead to different buckling modes which all have their own characteristic post-buckling responses. The analytical model is verified using a nonlinear finite element model formulated within the commercial code ABAQUS and excellent comparisons are obtained.

Mechanical and tribological characterization of nanostructured graphene sheets/A6061 composites fabricated by induction sintering and hot extrusion

An aluminum alloy (A6061) reinforced with graphene nanosheets (GNSs) was successfully fabricated by ultrasonic processing, high-frequency induction heat sintering (HFIHS), and hot extrusion. Harmful aluminum carbide (Al4C3) was not formed during HFIHS process as well as GNS particles were found to be able to stimulate recrystallization, restrict grain growth, and disturb the preferential texture in the present work. Enhancements in compressive strength of up to 50.4%, Vickers hardness of 13.3% as well as a 21.7% reduction in the friction coefficient along with a 17.2% reduction in the wear rate compared with those of as-extruded A6061 were measured. These improvements were due to the homogeneous dispersion of 0.25 wt% GNSs in the matrix. In addition, the yield strength predicted using modified model was in good agreement with the experimental results reported in this study. However, deterioration of the mechanical properties of the composites and a discrepancy between the theoretical prediction and experimental values occurred with the addition of 0.5 wt% GNSs owing to GNS agglomeration. This study demonstrated that the incorporation of an appropriate amount of GNSs can enhance the overall properties of a metal matrix, opening up an innovative design concept for fabricating bulk metal matrix composites (MMCs).

Effect of Graphene Oxide/Graphene Hybrid on Mechanical Properties of Cement Mortar and Mechanism Investigation

This paper evaluated the effect of graphene oxide/graphene (GO/GR) hybrid on mechanical properties of cement mortar. The underlying mechanism was also investigated. In the GO/GR hybrid, GO was expected to act as a dispersant for GR while GR was used as reinforcement in mortar due to its excellent mechanical properties. For the mortar specimen, flexural and compressive strength were measured at varied GO to GR ratios of 1:0, 3:1, 1:1, 1:3, and 0:1 by keeping the total amount of GO and GR constant. The underlying mechanism was investigated through the dispersibility of GR, heat releasing characteristics during hydration, and porosity of mortar. The results showed that GO/GR hybrid significantly enhanced the flexural and compressive strength of cement mortars. The flexural strength reached maximum at GO:GR = 1:1, where the enhancement level was up to 23.04% (28 days) when compared to mortar prepared with only GO, and up to 15.63% (7 days) when compared to mortar prepared with only GR. In terms of compressive strength, the enhancement level for GO:GR = 3:1 was up to 21.10% (3 days) when compared with that of mortar incorporating GO only. The enhancement in compressive strength with mortar at GO:GR = 1:1 was up to 14.69% (7-day) when compared with mortar incorporating GR only. In addition to dispersibility, the compressive strength was also influenced by other factors, such as the degree of hydration, porosity, and pore size distribution of mortar, which made the mortars perform best at different ages.

Investigation on Mechanical Properties and Microstructure of B4C/Graphene Binary Particles Reinforced Aluminum Hybrid Composites

In the present study, boron carbide and graphene-reinforced aluminum hybrid composites with various boron carbide (1, 3, 6, 9, 12, 15, 30 wt%) and graphene nanoplatelets (GNPs) content (0.15, 0.30, 0.45 wt%) were produced by the powder metallurgy method. The method consists of mixing, ultrasonic dispersing, mixing, filtering, drying, pressing, and sintering processes. The apparent density, compressive strength, and Vickers hardness of the fabricated composites were determined by density meter, universal test machine, and micro Vickers hardness measurement device, respectively. The phase and microstructural analysis of the fabricated composites were analyzed using an X-ray diffraction device and scanning electron microscope, respectively. The maximum apparent density (2.54 ± 0.005 g/cm3), the highest Vickers hardness (109.8 ± 1.5 HV), the best compressive strength (244 ± 5 MPa), and minimum porosity (4.0%) were obtained at Al-30%B4C-0.15%GNPs composite. The enhancement in Vickers hardness and compressive strength of Al-30%B4C-0.15%GNPs composite was detected as + 293% and + 190% compared with pure aluminum. In conclusion, it was detected that the mechanical strength of Al-30B4C-GNPs composites improved up to 0.15 wt%GNPs content. After 0.15 wt%graphene content, the mechanical strength of Al-30B4C-GNPs composites decreased due to the agglomerated graphene nanoparticles.