جستجوی مقالات مرتبط با کلیدواژه « durability » در نشریات گروه « مواد و متالورژی »

Cement mortar is used as a bonding agent between building materials in the construction of stone masonry and brick masonry. The focus on reducing the environmental burden caused by the high emission of carbon with the consumption of cement has gained interest. In this study, experimental investigations are conducted using two slag-based materials, i.e., Portland Slag Cement (PSC) and Processed Granulated Blast Furnace Slag Sand (PGBFS, iron slag), as a replacement for Ordinary Portland Cement (OPC) and River Sand (RS). The paper aims to investigate the influence of PSC with slag sand on the strength, durability, and microstructure of cement mortar. The present work specifically investigates the strength improvement of cement mortar with slag cement and slag sand by varying the curing period, comparing the results at 7, 14, and 28 days of curing. OPC is replaced fully with PSC, and River sand is replaced partially or fully with slag sand in different percentages, i.e., 0%, 20%, 40%, 60%, 80% and 100% for different types of mixes. Results showed the highest increase in compressive strength and high resistance to acid attack in cement mortar with 100% PSC and 60% Slag Sand replacement. The consumption of proposed materials will benefit the construction industry to achieve the net zero target.

In this work, the addition of a combination of Graphene Oxide Nanoplatelets (GONPs) and Ground Granulated Blast Furnace Slag (GGBFS) was studied as admixture in concrete. Tests on physical and mechanical properties and chloride permeability were conducted. GGBFS was replaced with Ordinary Portland Cement (OPC) and it was determined that GGBFS Up to 50% by weight improves the physical and mechanical properties of concrete. GONPs with an optimal amount of 50% by weight of GGBFS were added to the concrete and the physical and mechanical properties of the samples were determined. It was observed that the addition of GONPs was effective in improving the mechanical strength and physical properties of specimens. The results indicated that addition of 0.1 wt.% GO and 50 wt.% GGBFS would increase the compressive strength of the concrete sample up to 42.7% during 28 days and 46% during 90 days compared to OPC. Concrete with a combination of 0.1 wt.% GONPs and 50 wt.% GGBFS witnessed an increase in its flexural strength up to 58.5% during 28 days and 59.2% during 90 days. The results indicated that by adding 0.1 wt.% GO and 50 wt.%, concrete chloride permeability decreased substantially 72% for 90 day cured samples compared to OPC. GONPs as an alternative to cement up to 0.1% by weight can accelerate the formation of C-S-H gel, thereby increasing the strength and improving the resistance of water absorption and chloride permeability. The effects of pozolanic reaction in the concrete leading to the filling of the pores were significant factors in the proposed curtailment mechanism

In this paper, the mechanical as well as workability and durability properties of Self-Compacting Mortars (SCMs) made of different contents of Waste Ceramic Powder (WCP) and class F Fly Ash (FA) were experimentally assessed. To this end, the fresh properties of the SCM mixtures were evaluated through detailed examination of both mini slump flow and mini V-funnel tests. Ternary SCM mixtures are characterized by more flowability and passing ability than the control mix. The compressive and flexural strength, water absorption, and electrical resistivity tests were also carried out at different curing ages. The obtained results revealed that the compressive and flexural strength of the ternary SCM samples were lower than those of the control mix, especially at the ages of 7 and 28 days. However, there was a strength gain between 28 and 90 days due to the pozzolanic reactivity of both FA and WCP. Water absorption of the ternary SCM specimens containing FA and WCP followed a decreasing trend, thus highlighting the filling effect of the used pozzolans. Ternary SCM samples had considerably higher electrical resistivity (up to 144 % at 90 days) than the binary blends and control mix. Scanning Electron Microscopy (SEM) images confirmed that application of FA and WCP would fill in the pores and micro-cracks. Based on the obtained results, it can be concluded that both FA and WCP act more as a filler rather than a reactive pozzolanic material. Finally, the environmental analysis results revealed that replacement of 50 % of the Portland cement with 30 % FA and 20 % WCP would result in a reduction in the carbon footprint and energy demand by 47 % and 29 %, respectively.

Concrete is a material that can easily absorb nuclear radiation, and in this process, the density of concrete is an essential factor in absorbing the rays. Therefore, due to performance limitations and thickness, heavyweight concrete is used. In this study, serpentine coarse aggregates (SCAg) and serpentine fine aggregates (SFAg) were used as a substitute for sand and gravel in heavyweight concrete containing lead slag to protect against gamma rays. Determination of mechanical properties (compressive strength, tensile strength, and ultrasonic pulse velocity), physical properties (water absorption and electrical resistivity), and shielding properties (shielding against gamma rays) were among the main objectives. The results indicated the positive effect of SFAg and SCAg on the shielding properties of concretes against gamma rays. The replacement of SFAg and SCAg with natural aggregates increased the density of the samples, which resulted in an increase in 3.8 to 42.9% in the linear attenuation coefficient against gamma rays. SFAg has a significant effect on gamma-ray attenuation, especially when these materials are made of high-density minerals, due to their property of reducing the pores in concrete.

With the industrial revolution, many inventions have been introduced with many solid waste materials in returns. This study investigates the potential recycling of waste plastic sheets, made from low-density polyethylene, as asphalt modifier in the paving mixture. The shredded plastic sheet was used in the asphalt mixture via the wet process. The dosage rate was set up to 9 % by weight of asphalt binder (0, 3, 6, and 9)%. The experimental program was designed to assess the mechanical properties (Marshall stability and flow, and volumetric properties), durability, and short-term aging of asphalt mixtures, in addition to economical assessment. The test results revealed the applicability of using this solid waste material in paving construction as a surface layer, since its usage enhances the pavement performance by increasing stability, index of retained strength, and volumetric characteristics before and after aging as well as saving in cost. The best enhancement can be achieved with 6% of recycled low-density polyethylene.

Ultra-High Performance Concrete (UHPC) is a cementitious composite with fine aggregates and a homogeneous matrix with high compressive strength and excellent durability against aggressive agents. It is common to use short steel fibers in the UHPC. Besides, using steel fibers considerably increases the flexural ductility, durability and energy absorption. Using glass fibers in UHPC is a novel technique which improves its mechanical properties and it has the benefit of being lighter, and cheaper than steel fibers. Furthermore, glass fibers can be used for thin concrete plates for aesthetic purposes. However, glass fibers reinforced concrete is incompatible with the hydration reaction in the alkaline environment of concrete as it can damage glass fibers, so the mechanical properties of the concrete are decreased over long periods. The mechanical properties of UHPC containing glass fibers (GF-UHPC) was investigated under three regimes of normal curing, autoclave curing, and autoclave curing plus being in hot water for 50 days (accelerated aging). Besides, the substitution of silica fume by Metakaolin in GF-UHPC was studied to understand its mechanical properties after thermal curing. The results showed that after accelerated aging, the behavior of specimens become more brittle and the modulus of rupture and toughness indices of all prismatic specimens decreased, the modulus of rupture for samples containing glass fibers was 40% lower than autoclave curing results. However, the compressive strength under accelerated aging increased at least 4% in comparison to the normal curing. Replacement of silica fume with Metakaolin slightly increased the toughness with regard to flexural strength.

This study investigates the bond strength behaviour of plain surface wave type configuration (PSWC) rebars in comparison to mild steel (MS) and high yield strength deformed (HYSD)  rebars of varied rib configuration as per BIS and ASTM standards. The variables in the rebar include plain surface, curved surface, parallel rib, diamond rib and Nano modified cement polymer anticorrosive coating (CPAC). Total of 30 pull-out specimens and 12 beam-end specimens were put to a pull-out test following BIS and ASTM standard respectively. The load corresponding to 0.025mm free end (FE) slip and 0.25mm loaded end (LE) slip were carefully observed. The load-deflection behaviour, appearance of the first crack in the specimens and ultimate failure load was recorded. The experimental results showed that as compared to MS rebars, HYSD rebars offer an approximately threefold increase in ultimate bond strength and 1.5 times increase in usable bond strength irrespective of varied rib configuration. PSWC rebars with 4mm offset and 80mm pitch offered 2.4 times increase in ultimate strength and 76.2% increase in usable bond strength as compared to MS rebars. The ultimate pull-out load of PSWC rebars was around 25% and the usable bond strength was only 8.6% lesser than HYSD rebars with parallel ribs. The adopted coating enhanced the corrosion resistance and the reduction in bond strength with any surface configuration was less than the permissible maximum reduction of 20% as specified in IS 13620-1993. Hence it can be concluded that PSWC rebars offered promising bond strength results and upon further optimization and study in other aspects,  PSWC rebars can be a way to replace HYSD rebars in future for enhancing concrete durability at zero added cost.

This experimental work is about the study of drying shrinkage followed by strength testing of lightweight foamed concrete (LFC) specimens with the confinement of woven fiberglass mesh (FGM) at three different densities. The LFC specimens were wrapped with 1-layer to 3-layer(s) of FGM for cube and cylinder specimens and in beam specimen, it was centrally spread along the longitudinal axis. The specimens were cured under air storage conditions and the drying shrinkage test was carried following ASTM C157/C 157M specification on three prism-shaped ‘75mmx75mmx285mm’ specimens. NORAITE PA-1 foaming agent was used to produce the desired density of LFC. All of 324 specimens were tested for mechanical properties of LFC. The cast specimens were put to test at 7days, 28days and 56 days. In compression strength test, cube dimensions of 100mm side following BS EN 12390-3:2009 were adopted. The flexural strength was conducted on  ‘100mmx100mmx500mm’ beam specimens following BS ISO 1920-8:2009. The specimens ‘100mm in diameter and 200mm in height’ were tested for split tensile strength considering ASTM C496/ C496M-04e1 specifications. The result showed that confinement with 160g/m2 (GSM) of FGM significantly restricts the drying shrinkage of LFC specimens compared to control specimens and it decreases with the increases in layer(s) from l-layer to 3-layer(s) and density of LFC. The testing of the mechanical properties of LFC showed a direct proportionality between strength and LFC density and confinement layer(s). The failure pattern observed in all specimens was either by debonding or splitting of fibers of  FGM. Thus,  LFC at 1600kg/m3 density confined/reinforced with 3-layers of  FGM conquers the good performance in drying shrinkage and strength properties while the poor performance was shown by the unconfined LFC at 600kg/m3 density.

In recent years, fiber-reinforced polymer-polyvinyl chloride (FRP-PVC) tubular columns have been used increas-ingly in civil engineering applications. Concrete-filled RP-PVC tubes possess high durability, high strengthening performance, satisfactory bond strength, and compressive behavior. It has been observed that these cost-effec-tive tubular columns are promising materials for enhancing strain capacities, strength, and stiffness of structures containing reinforced concrete (RC). These composite tubular columns are composed of FRP and PVC and are used for strengthening concrete. FRP enhances strength capacity while PVC improves the corrosion resistance of concrete piles in harsh environments. This review focuses on the properties of FRP-PVC tubular columns, their application in civil engineering, and the recent advancements in this field.©2020 jourcc. All rights reserved.

This research paper describes the study of combined effect of Fly Ash (FA) and Rice Husk Ash (RHA) on properties of concrete as partial replacement of Ordinary Portland Cement (OPC). These by-products are having high pozzolanic reactivity. In this research, the composition of mix was used with 10% RHA along with 10, 20 and 30% FA as partial replacement of cement. In this study, the compressive strength, workability, durability performance, and microstructure of concrete were examined. The microstructures of the concrete sample were analyzed by Scanning Electron Microscope (SEM) and elemental contents by Energy Dispersive X-ray (EDX). The test results showed that the highest compressive strength was achieved by 10%RHA and 20%FA used and beyond that, the strength was shown similar to control concrete mix (CM). The Ultrasonic Pulse Velocity (UPV) test result values were above the 4.5km/s; hence it may be considered as excellent concrete as per IS code for all mix. Response Surface Methodology (RSM) was adopted for optimizing experimental data. Regression equation was yielded by the application of RSM relating response variables to input parameters. This method aids in predicting the experimental results accurately with an acceptable range of error. This type of concrete mix is very effective in enhancing the mechanical and durability properties of concrete by saving cement and cost. It also makes concrete sustainable as it reduces environmental problems.

This project is engineering the properties of concrete containing natural nano zeolite as supplementary cementitious material in the blended Portland-cement based binder in amounts of 5, 7 and 10% by mass. Crashing of clinoptilolite zeolite is performed by means of planetary ball mill. Two types of concrete along with water to cementitious material ratio (W/(C P)) in 0.45 and 0.4 at the ages of 7, 28 and 90 days and were compared with each other. The effect of these additives on mechanical properties (compressive and tensile strength) and durability has been investigated by Electrical Resistivity (ER) and Rapid Chloride Penetration Test (RCPT) at the ages 28 and 90 days. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) revealed that nano particles of natural clinoptilolite could improve quality of concrete. As a result of the tests, decrease in penetration of chloride ion and increase electrical resistivity significantly that are appropriate option for controlling of corrosion in reinforced concrete structures but increase of mechanical characteristics is not considerable.

Polymer concrete (PC) is a composite material prepared by resin and aggregates. Advantages of polymer concretes include rapid curing, high flexural and compressive strengths, suitable chemical resistance and low permeability. In this research, a comparative study was performed on degradation of polyester resin concrete in different chemical solutions. Polymer concrete specimens were examined for flexural strength and flexural toughness after two and four months of exposure to the chemicals (i.e. sulfuric acid, sodium hydroxide, sodium sulfate, nitric acid, hydrochloric acid, citric acid, demineralized water, potable water, potassium hydroxide, gas oil). Results showed that the highest decrease in flexural strength occurred in sodium hydroxide solution after two months of exposure. Comparing acid attack to the specimens it was found that citric acid as an organic acid, despite of higher pH, had the highest impact on flexural strength. The flexural strength of PC specimens decreased considerablly in all chemicals (except in gas oil). There was not significant difference between two and four months of exposuring, therefore, the main degrading processes start during the first 60 days of exposuring.

The effect of storage time on some properties of groundnut shell briquette with 5, 10, 15 and 20% binder (cassava gel) was studied. The briquettes were prepared using a motorized briquetting machine. The moisture content, durability rating, water penetration, calorific value and the ash content were determined after every 30 days for 6 months. The results reveals that the moisture content of briquettes decreases during storage during the hot season, the result also reveals a decrease in the durability rating. However, there is an increase in the water penetration with storage time. There is also an increase in the ash content with storage, and this is believed to be responsible for the decrease in the calorific value of the briquettes with storage. However, briquettes with 15 and 20% binder remained relatively stable after 6 months of storage.

Structural concrete exposed to marine environment deserves special attention as the diffused sea salts chemically react with harden cement matrix and forms various expansive/leachable compounds leading to loss of material, strength, cracking, spalling etc. This study cover the effect of sea water on the specimens cast from two grades of concrete exposed to simulated marine environment over a year. Enhanced salt concentration i.e. 1N, 3N, 6N, 12N of the curing solution was used to get the accelerated effect. Several destructive and non destructive tests including XRD study were performed to assess the state of deterioration. From test results, it is observed that concrete exposed to sea water of different concentration suffers a loss of compression strength of around 19% and 33% respectively as compared to 28 days and 365 days of plain water cured concrete.