Poor Compressive Strength Research Articles

The preparation of a difunctional porous β-tricalcium phosphate scaffold with excellent compressive strength and antibacterial properties.

Porous β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP) scaffolds are widely applied in the field of bone tissue engineering due to their nontoxicity, degradability, biocompatibility, and osteoinductivity. However, poor compressive strength and a lack of antibacterial properties have hindered their clinical application. In order to address these disadvantages, graphene (G) and silver nanoparticles were introduced into β-TCP through a two-step method. In the synthesis process, G-β-TCP was prepared via an in situ synthesis method, and then silver nanoparticles and HAp particles were coated on the surface of the G-β-TCP scaffold in an orderly fashion using dopamine as a binder. From the results of characterization, when the content of graphene was 1 wt% of β-TCP, the G-β-TCP scaffold had the highest compression strength (127.25 MPa). And core–shell G-β-TCP-Ag-HAp not only had reduced cytotoxicity via the continuous release of Ag+, but it also achieved long-term antibacterial properties. Besides, the material still showed good cell activity and proliferation.

Mechanical Properties of Recycled Tire Wires and Glass Fibers Reinforced Concrete

Concrete is a versatile construction material with various uses. It is has poor tensile strength and good compressive strength mechanical properties. In past, an effort has been made to improve concrete mechanical properties by mixing with various foreign materials such as synthetic and natural fibers, steel wires and plastics. However, there is research gap in literature to study comparative use of recycled and new materials for improving concrete mechanical properties. This research work experimentally investigates use of new glass fibers and recycled tire fibers in 0.5%, 1% and 1.5% in weight mixes with concrete to study concrete mechanical properties performance gains such as compressive, flexural and split tensile strength properties. Experimental results indicated as compared to control plain concrete specimen, use of recycled steel fiber and glass fibers in concrete mix increased flexural property of concrete by 19.64% and 24.56% whereas split tensile strength of concrete is enhanced by 8.15% and 12.02%, respectively. Similarly, compressive strength of concrete is improved by 5.34% and 7.87% respectively. Also, optimum blend percentage of recycled tire fiber and glass fiber for enhanced performance gains in concrete mechanical properties is one percent. Finally, use of recycled steel fibers and glass fibers in concrete exhibited similar concrete mechanical property performance gains however, recycled steel fibers has 78% direct cost reduction as compared to glass fibers.

A Low‐Cost and Low‐Density Cement Slurry System Suitable for a Shallow Unconsolidated Stratum

The shallow unconsolidated stratum in the offshore oilfield is characterized by large porosity, low temperature, and weak formation and often faces problems such as low density and poor compressive strength of a cement slurry, among others, which pose serious challenges to construction. A high‐performance low‐density cement slurry system must be used for cementing to ensure the safety of subsequent drilling and mining on‐site and to reduce the cost of cement slurry for the efficient development of oil and gas fields. Based on these problems, according to the principle of particle gradation, a mixture with a high accumulation rate and low density composed of five types of mineral materials, i.e., artificial microbeads, floating beads, microsilicon, fly ash, and slag, has been developed through a large number of indoor experiments, and a set of low‐cost and low‐density cement slurry systems has been developed; these systems are suitable for the shallow loose formations of offshore oil fields. The cement slurry system meets the requirements of the cementing operation conducted under different temperatures and pressures. The density range is 1.4–1.7 g/cm3, which can be adjusted. The cement slurry is stable and exhibits good fluidity. The thickening time meets the requirements of cementing construction. Moreover, the compressive strength of the cement paste is high, and the compressive strength of cement paste is greater than 12 MPa for 24 h and 14 MPa for 48 h of curing at 50°C, which maximizes the economic benefits. The research results provide technical support for the safe and efficient development of offshore oil and gas fields.

IoT System for Pellet Proportioning Based on BAS Intelligent Recommendation Model

In the future, pellet is gradually replacing sinter as the main charge structure of blast furnace ironmaking. In the process of pellet production, the linear regulate and control method is often used in the operation of proportioning scheme, roasting regime, and parameter setting. There are some problems such as low pelletizing rate and poor compressive strength. It is urgent to realize the intelligent pellet manufacturing. In order to realize an intelligent pellet material matching system, the general regression neural network is applied to construct the prediction model of mature pellets compressive strength under the technical framework of industrial Internet of Things (IoT), using beetle antennae search (BAS) algorithm to construct an intelligent recommendation model of pellets with optimal proportioning. The prediction model and the intelligent recommendation model are coupled within the technical framework of IoT. An IoT system of pellet material proportion is implemented, which is dominated by the compressive strength of mature pellet. The system can realize automatic detection of raw materials, automatic quantification processing of index data, automatic start of prediction model, visualization of proportioning results, and “one-click” operation of proportioning scheme. Recommended system simulation and experimental results show that the prediction model of the compressive strength of cooked balls has the strong interpolation ability and the excellent generalization performance; in the range where the changes of various pellet proportioning are no more than 20%, the intelligent recommended best proportioning scheme can increase the compressive strength of cooked pellets by over 16% on average, and the system runs stably and the simulation results are effective.

Preparation of one‐part geopolymeric precursors using vanadium tailing by thermal activation

AbstractThe main purpose of this study is to develop a user‐friendly one‐part geopolymer using vanadium tailing (VT). Geopolymeric precursor consists of activated VT and metakaolin that can react directly with water to form geopolymers. The roasting temperature plays an important role in the VT activation, which affects the compressive strength of the final geopolymer. The geopolymer with accepted compressive strength, that is 29.0 MPa after 7 days curing in ambient condition, can be prepared using VT after thermal activation at appropriate temperature (400‐600°C). As the roasting temperature is increased to 700°C, the VT is molten and sintered and the ability of providing alkaline and Si4+ is drastically weakened, which results in a poor compressive strength geopolymer.

Properties of sulfoaluminate cement-based grouting materials modified with LiAl-layered double hydroxides in the presence of PCE superplasticizer

Sulfoaluminate (CSA) cement-based grouting materials (CBGM), due to their fast hydration rate and high early strength, can be used in repair and reinforcement projects. To obtain a high workability, CBGM has often been modified by a polycarboxylate ether (PCE) superplasticizer with a high water to binder ratio (>0.5), which results in a poor compressive strength. Nano LiAl-LDH has been reported to have excellent properties for improving the mechanical behavior of sulfoaluminate (CSA) cement clinkers. In addition to the physicochemical characteristics of the nanomaterials, the admixtures used in CBGM paste can also affect the properties of the nanomaterials. In this paper, the effect of the PCE superplasticizer concentration on the properties of CBGM modified with LiAl-LDH was investigated, and a possible reason is provided. The results show that low PCE superplasticizer concentrations (0.9 wt% and 1.15 wt%) increased and high PCE superplasticizer concentrations (1.38 wt%, 1.76 wt% and 2.13 wt%) decreased the compressive strength of a CBGM paste modified with LiAl-LDH in comparison with that of the control paste. The PCE superplasticizer did not intercalate into the interlayers of the LiAl-LDH, and the interaction between the PCE superplasticizer and LiAl-LDH was limited to surface adsorption. A small quantity of lithium ions was released from the precipitation-dissolution equilibrium of LiAl-LDH in the slurry. Lithium atoms can enter the vacant octahedral sites of montmorillonite, which is one component of the CBGM, via isomorphous substitution, and the interaction decreased the adsorption quantity of the PCE superplasticizer on the bentonite surface, resulting in the high fluidity of the CBGM paste in the presence of a high PCE superplasticizer concentration.

Characteristics and controlling factors of the Lower–Middle Jurassic sandstone reservoirs in Amu Darya right bank area, Turkmenistan

Based on laboratory analysis and core description, characteristics and the controlling factors of the Lower–Middle Jurassic reservoirs in Amu Darya right bank area are examined in this article. The study reveals that fine-grained lithic sandstones, feldspar–lithic sandstones, and siltstones are the main types of reservoir rocks in the central area, while fine-grained lithic–quartzose sandstones are predominant in the eastern area. The major pore types are intergranular and intragranular dissolved pores; the predominant pore throats are lamellar throats. Fractures develop poorly in the study region, but relatively well in the eastern area. The reservoirs are pore-dominated sandstone reservoirs with limited fractures, characterized by very low porosity and permeability. Reservoir evolution is jointly controlled by sedimentation, diagenesis, and tectonic movements. Sedimentation laid the foundation to porosity evolution. Subaqueous distributary channels and mouth bars are the beneficial lithofacies for reservoir development. Poor compressive strength of sandstones, deep paleoburial depth, and destructive subsidence style of the strata led to strong compaction. Primary pores are almost entirely destroyed by compaction and eogenetic calcite cementation. Ferroan dolomite cements and quartz overgrowths occupied the remaining intergranular pores furtherly. However, dissolution played an effective role on the generation of secondary pores, and the influences of authigenic clay minerals are minor on reservoirs. The Neogene–Quaternary tectonic movements caused intensive lateral compressional stress thus made further damage to reservoir pore structure. Nevertheless, fractures generated by tectonic movements increased reservoir permeability and provided valid migration pathways for the late dissolution fluids, therefore improved reservoir physical properties obviously.

Effect of basicity on the structure characteristics of chromium-nickel bearing iron ore pellets

High MgO content and the dehydroxylation of laterite ore particles lead to poor compressive strength of fired chromium-nickel bearing iron ore pellets at natural basicity. For improving the compressive strength of the fired chromium‑nickel bearing iron ore pellets, burnt lime was applied as the additive to improve the pellet structure. Results showed that with an increase in quaternary basicity, the compressive strength of fired pellets was enhanced obviously. The optimum basicity of fired chromium-nickel bearing iron ore pellets is suggested at 1.15. Under the optimal test conditions, the compressive strength of fired pellets with natural basicity is only 607 N/pellet, but the compressive strength of fired pellets reaches 1991 N/pellet at basicity of 1.15. The structure of fired chromium-nickel pellets at 1.15 basicity greatly depends on the liquid bonding phases among chromite, hematite and enstatite particles, which are composed of kirschsteinite, SFCA and glass, and amount to 19.27% in fired pellets. The liquid bonding phases fill in the voids among mineral particles and interconnect them to form the intertwined structure, which increases the shrinkage and significantly improves the compression strength of fired pellets.

Use of KEVLAR ® 49 in Aircraft Components

Aircraft industry is also finding its way to adapt on the increasing demand not only considering aircraft safety and customer requirements, but also on the increasing legislative requirements in terms of resource efficiency and gas emissions. This document explores Kevlar 49’s application on aircraft components and why this material is specifically selected for such applications above any other Kevlar type of materials. Its functions, properties, advantages and disadvantages are discussed together with some alternative materials in lieu of Kevlar 49. In order to provide credible information, literature search was conducted using significant keywords in Google Scholar and journal repository Deepdyve. Kevalr ® 49 is considered an exceptional material for reinforcement to produce aircraft components. It has high tensile strength, lightweight, inert on some conditions, stiff, and resilient. However, Kevlar’s has poor compressive strength, workability and is overly stiff for some applications. Another disadvantage is its cost, though it was shown to belong to a middle ranged material relative to carbon fiber and Boron. But overall, there are extensive applications in aircraft components that are now continuously using this material as reinforcement with other materials like carbon and boron to arrive on an ideal blend of product.

A novel rammed earthen material stabilized with steel slags

Though earthen construction materials are locally available and ecologically friendly, they have some deficiencies, such as the poor compressive strength, water resistance and durability in comparison with the mainstream wall materials. To overcome the drawbacks, a novel rammed earthen material stabilized with slags from a steelwork is prepared in this paper. The mechanical, durability and thermal performance are investigated experimentally. Besides, the mechanism of stabilization is analyzed. The results show that the introduction of the steel slags improves the compressive strength and durability of the earthen materials greatly, but decreases their thermal resistance.

A novel form-stable phase change composite with excellent thermal and electrical conductivities

Electro-to-heat energy conversion/storage provides a new direction for the development of phase change materials (PCMs). However, conversion rate and energy storage density of the existing PCMs are limited by their low intrinsic electrical and thermal conductivities and poor compressive strength. In this work, a novel form-stable phase change material (FSPCM) has been prepared via ligand replacement followed by the embedment of acetylene black conductive network. The addition of 20 wt% acetylene black reduces the resistivity of the polyethylene glycol-based PCM from 107−1012 Ω·m to 0.3 Ω·m, while its thermal conductivity is increased by 300%. The resulting conductive composite possesses the ability to store heat at voltage as low as 1.8 V and high electro-to-heat conversion efficiency. The composite compressive strength reaches 105 Pa at an ambient temperature of 110 °C, while the temperature is 60 °C more than that of phase transition temperature of PCM. Further, the magnitude of the temperature change in the electrothermal conversion curves recorded after 50 solid-liquid phase transition cycles does not exceed 2.0%. The excellent electrical and thermal conductivities as well as good mechanical properties of the synthesized composite suggest a promising route for manufacturing novel materials with high power capacity for thermal storage applications.

Compressive Strength of Concrete from Lightweight Bubbles Aggregate

Compressive strength of concrete is the major mechanical properties of concrete that need to be focused on. Poor compressive strength will lead to low susceptibility of concrete structure towards designated actions. Many researches have been conducted to enhance the compressive strength of concrete by incorporating new materials in the concrete mixture. The dependencies towards natural resources can be reduced. Therefore, this paper presents the results of an experimental study concerning the incorporation of artificial lightweight bubbles aggregate (LBA) into cementations mixture in order to produce comparable compressive strength but at a lower densities. Three concrete mixtures containing various percentages of LBA, (10% - 50% of LBA) and one mixture used normal aggregate (NA) were prepared and characterized. The compressive strength of LBA in concrete was identified to be ranged between 39 MPa and 54 MPa. Meanwhile, the densities vary between 2000 kg/m3 to 2300 kg/m3.

Preparation of complex porous scaffolds via selective laser sintering of poly(vinyl alcohol)/calcium silicate

Biodegradable polymer/bioceramic composite scaffolds can overcome the limitations of polymer scaffolds such as poor compressive strength and bioactivity. In this study, poly(vinyl alcohol)/calcium silicate (CaSiO3) composite scaffolds with fully interconnected porous structures and customized shapes were successfully fabricated via selective laser sintering. The microstructure, porosity, and mechanical properties of the scaffolds were characterized. Based on the results, CaSiO3 particles were well dispersed and embedded in the poly(vinyl alcohol) matrix after sintering. The compressive strength increased with increasing the content of CaSiO3 up to 15 wt%, and then decreased with further increasing CaSiO3 content to 20 wt%. Our study also revealed that the scaffolds could not be fabricated successfully as fewer poly(vinyl alcohol) particles fused together when CaSiO3 was higher than 20 wt%. Based on the in vitro data, the poly(vinyl alcohol)/CaSiO3 composite scaffolds possess good bioactivity and cytocompatibility.

Polymerizable nanoparticulate silica‐reinforced calcium phosphate bone cement

Bone cements based on calcium phosphate powder and different concentrations of colloidal silica suspensions were developed. Setting time and washout behavior of the cements were recorded and compared with those of a control group prepared by the same powder phase and distilled water as liquid. The phase composition, compressive strength, and morphology of the cements were determined after incubation and soaking in simulated body fluid. Proliferation of osteoblasts seeded on samples was also determined as a function of time. The results showed that the long setting time, poor compressive strength, and undesirable washout behavior of the cement made with distilled water were considerably improved by adding colloidal silica in a dose-dependent manner. On the basis of XRD and SEM results, both control group and nanosilica-added cements composed of nanosized apatite flakes after 7 days soaking, in addition to tetracalcium phosphate residual for the latter. It was found that the rate of hydraulic reactions that are responsible for conversion of the cement reactants to nanostructured apatite was increased by the presence of colloidal silica. Furthermore, the osteoblasts exhibited better proliferation on nanosilica added cements compared to control one. This study suggests better applied properties for nanosilica-added calcium phosphate cement compared to traditional cements.

Modification of styrene-divinyl benzene copolymers using monoacrylates as ter-monomer

Porous styrene-divinyl benzene (St-DVB) copolymers were synthesized by incorporation of cyclohexanol during copolymerization. It led to copolymers of high porosity, high surface area and high % swelling. However these copolymers exhibit very poor compressive strength. Therefore they have been modified by terpolymerization in order to achieve styrene-DVB copolymers of adequate compressive strength with high surface area and % swelling. These terpolymers were synthesized by suspension copolymerization of styrene, DVB and variable amount of monoacrylates in presence of cyclohexanol as a diluent. Methylacrylate, ethyl acrylate, butyl acrylate, methylmethacrylate and glycidyl methacrylate were taken as ter-monomers for the present study and influence of these ter-monomers on formation of porous structure of the copolymer was investigated by % swelling, surface area, bulk density, compressive strength measurement and surface morphology. Incorporation of ter-monomers resulted into increased compressive strength and bulk density with adequate surface area and % swelling with the increased content of monoacrylates. Further at constant ter-monomer concentration, physical properties and thermal stability of the ter-polymers were found to be in the order: MMA > MA > EA > BA > GMA.

Mineralogy of plain Portland and blended cement pastes

The compressive strength and microstructure of blended cement was investigated in this study. The hydration products of cements were identified by means of scanning electron microscopy (SEM) and polarising microscopy (thin section). Results indicated that the blended cement required pozzolanic activity in addition to its cementing property with the addition of 30% material. Aggregations of belite grains were observed which were surrounded by alite. Blended cement exhibited high early-term strength. However, its 3d-age strength is lower than ordinary Portland cement. On the other hand, all blended cement mortars fulfil the compressive strength requirements of TS 24. Hence, it can be said that blended cement can achieve adequate early compressive strength. A reduction in the amount of CSH gel and the porosity of the matrix in mortars were found to be responsible for the poor compressive strength of the cement paste in early the age.

Enhancement of mechanical and hydrophobic properties of Adobes for Building Industry by the addition of polymeric agents

Availability, cheapness and thermal insulation properties give adobe an advantage over other building materials in dry regions. On the contrary, its poor compressive strength and high water adsorption are important disadvantages. We report the enhancement on compressive strength and water absorption resistance obtained in this material by the addition of dodecylamine and emulsified asphalt to the clay used for its manufacture. We characterized the adobes by X-ray diffraction, infrared spectrometry, ζ-potential measurements and scanning electronic microscopy. Ultra violet accelerated test, compressive strength test and water absorption tests were also carried out. The results show that adobes with cationic amine and emulsified asphalt improve their compressive strength and lower their water absorption at the time that they preserve their properties under weathering conditions.

Characterisation and treatment of roads covered with zinc ashes, muffle furnace fragments and lead slags from former non-ferrous metal industries in Belgium.

Zinc ashes, muffle furnace fragments and lead slags from non-ferrous industries were applied to pave roads in the North of Belgium. From an inventory it appeared that there are at least 490 km of such roads. In our survey the materials on these roads were characterised. The total metal concentration, the availability and the leaching as a function of time were determined. It appeared that these materials contain high concentrations of heavy metals, some of which are readily available. The high leaching of some metals makes them as such unsuitable as secondary construction material. Methods for the application of these materials for road construction were examined where the materials replaced part of the sand and gravel fraction in lean concrete and in bituminous mixtures, or where they replaced the sand in sand-cement mixtures, all these to be used for road foundations, cycle tracks, etc. When lead slags were applied in lean concrete, a material was obtained complying with the standards for secondary construction materials and with sufficient compressive strength for road foundations. When zinc ashes or muffle fragments were used to replace sand in sand-cement mixtures, again a suitable construction material was obtained. The other combinations tried out were rather unsuccessful, because of high metal leaching and/or poor compressive strength.

A metal-faced casting resin mold for facial prostheses

I mproved stone, epoxy resin, polyurethane, silicones, and linotype metal molds have advantages and disadvantages in the fabrication of facial prostheses.’ Improved stone molds may chip, break, or crack; lose their high surface reproducibility; have poor compressive strength; and are less ductile than metal molds. Silicone and polyurethane molds have low yield strength and easily tear.’ Epoxy molds do not readily adapt to other systems and require overnight cure.3,4 Linotype metal molds seem to be the most popular, but they are the most difficult and time consuming to make, require numerous materials in their manufacture, and are heavy.5 Choy et al.” have detailed the advantages and disadvantages of different metal mold preparation techniques. This article describes a technique for production of highly accurate metal molds in a relatively short time. The technique uses hot air to spray molten metal onto a prosthesis pattern, thus creating an excellent metal reproduction of its surface. The sprayed metal layer is then reinforced with an autopolymerizing casting resin. The metal spray process was developed over 50 years ago. The process used two electrically insulated wires with an arc completed across their ends. As the arc melted the wire, the molten alloy was blown away from the arc with a large volume of compressed air. The process is still used for manufacturing large molds and for spraying high melting-point metals. The metal chamber spray gun, developed about 20 years ago, has been refined continually. It has a gas or electrically heated chamber in which alloys are melted and atomized with a small volume of compressed air in the same manner as paint is sprayed. Another spray process includes a high temperature plasma flame into which metals are introduced as wire or’ powder. This process is not customarily used for making molds, because the temperature of the target material is raised excessively. It is mainly used for metallizing or repairing worn machinery. The M-80 metal spray gun (Arconium Corp. of America, Providence, RI.) used in the present technique contains an alloy melting chamber heated by a propane