Effect Of Different Curing Conditions Research Articles

Multiaxial and Multiscale Implications of Dissipative Behavior of Composites

A brief description of the progress on mechatronic multi-degree of freedom material testers developed at the US Naval Research Laboratory (US-NRL) is given to describe the enabling technology for acquiring data that encapsulate both the recoverable and the dissipative behaviors of various composite material systems under quasi-static multiaxial loading conditions. The notion of material equivalence is then explored from the perspective of the data-driven dissipative behavior of multiaxially tested composite laminates. Emphasis is given by considering the same fiber within the same resins and vice versa. The effect of different curing conditions is also examined. As a follow-up, an overview of a multiscale computational framework is also outlined for the purpose of introducing multiscale implications of how macroscale behavior in terms of experimental data can yield information about the behavior of materials at lower length scales.

Effect of different curing conditions on the mechanical properties of reactive powder concrete

Reactive Powder Concrete (RPC) is an ultra-high performance concrete which has superior mechanical and physical properties, and composed of cement and very fine powders such as quartz sand and silica fume with very low water/ binder ratio and Superplasticizer. Heat treatment is a well-known method that can further improve the performance of (RPC). The current research including an experimental study of the effect of different curing conditions on mechanical properties of reactive powder concrete (compressive strength, modulus of rupture and splitting tensile strength), the curing conditions includes three type of curing; immersion in water at temperature of 35 OC (which is considered as the reference-curing situation), immersion in water at temperature of 90 OC for 5 hours daily and curing with hot steam for 5 hours daily) until 28 days according to ASTM C684-99 [8]. This research includes also the study of effect of adding silica fume as percentage of cement weight on mechanical properties of reactive powder concrete for different percentage ratios (5%,10% and 15%). Super plasticizer is also used with ratio of (1.8%) by weight of cementitious material; constant water cement ratio (0.24) was used for all mixes. For each reactive concrete mix, it has been cast into a cubes of (150*150*150) (to conduct the compression test), a cylinders of 150mm diameter with 300mm height (to conduct split test) and prisms of (500*100*100)mm to conduct the modulus of rupture test. The results showed that the best method of curing (according to its enhancing the RPC mechanical properties) is the method of immersion in hot water at temperature 90 OC for the all silica fume percentages, and the best used silica fume percentage was (10%) for the all used curing methods.

Influence of Drying on the Stiffness and Strength of Cement-Stabilized Soils

Nowadays, improving the strength and deformation properties of soft soils by deep soil mixing is a commonly used technique. There is also an increasing interest in the use of this technique for foundation/structural elements and excavation retaining walls applications. The compressive strength and elastic modulus of the soil mix material are key parameters in the design of these structures. However, there is very limited information available on the impact of exposure to air drying (in the case of retaining wall) on the strength and stiffness of cement stabilized soils. The aim of this study is to investigate the effects of different curing conditions (immersion in water, cycles of wetting and drying, continuous air drying) on the mechanical properties of soils treated with cement in the laboratory. Free–free resonance tests and unconfined compression tests were performed on specimens of silt and sand treated with blastfurnace slag cement. Strength increases more rapidly than stiffness between 7 and 30 days. The strength of stabilized soils submitted to cyclic wetting and drying before the cement hydration process is complete continues to increase. As long as the periods of drying do not induce microcracks, the stiffness of the treated soil specimens also increases with time. However, the stiffness is lower than for the specimens cured in water indicating a disruptive effect of the imposed wetting–drying cycles on stiffness. Continuous exposure to air drying inhibits strength development due to insufficient water for hydration. Significant stiffness decreases were observed on specimens of stabilized silt and are attributed to microcracking.

The Effect of Different Curing Conditions on Compressive Strength of Concrete

The focus of this research work was to analyse the effect of different types of curing oncompressive strength of concrete structures. For this purpose, 54 test specimens of cylindrical shape wereprepared. These specimens were cured with different methods and were tested on different age days toanalyse the effect of curing on compressive strength. Test specimens cured with conventional water curingmethod gives the highest results as compared to the other adopted methods.

The effect of different curing conditions on hardness, thickness, and residual stress of carbon fiber reinforced epoxy composites

In this study, an attempt has been made to optimize the curing process of carbon fiber reinforced epoxy laminates. The effect of four factors: curing temperature, cooling method, wetting method, and resin-to-hardener ratio was studied. Custom non-regular fractional factorial design was utilized to choose the combination of these factors levels. Vickers micro-hardness test was conducted to study hardness in all the specimens. Thickness measurements were taken. The residual stresses along fiber direction were measured using Timoshenko bending beam method. Box plots were drawn to understand data variability. ANOVA was used to analyze results. It was shown that curing at 180℃ or lower, applying furnace cooling, raising resin-to-hardener ratio, and avoiding wetting the bottom side have reduced data variability, lowered thickness, and residual stress.

Durability Characteristics of Polyvinyl Alcohol–Treated Oil Palm Shell Concrete

This paper presents the results of an experimental study on the durability characteristics of lightweight concrete produced from agricultural waste oil palm shell (OPS) pretreated with polyvinyl alcohol (PVA) as full replacement material for conventional coarse aggregates. The tests conducted to assess the durability characteristics of PVA-treated OPS concrete are water absorption, volume of permeable voids, sorptivity, and 90-day salt ponding test in which the chloride diffusion coefficient and time to corrosion initiation are determined. The effects of different curing conditions on the durability characteristics of PVA treated OPS concrete are discussed and the results obtained are compared with raw (untreated) OPS concrete. Results show improvements in terms of water absorption, volume of permeable voids, and resistance to chloride penetration of PVA-treated OPS concrete compared with raw OPS concrete under all types of curing conditions used.

The Effect of Different Curing Methods on the Compressive Strength of Eggshell Concrete

The work assesses the effect of different curing conditions on the compressive strength of the eggshell concrete. Two different qualities of the eggshell powder were used to make concrete with 0.45 water/cement ratio. The eggshell powders were treated as partial cement replacement of 5%, 10%, 15% and 20%. The concrete cube specimens (100 x 100 x 100) mm were exposed to two different environments (full water curing and open-air curing) for 1, 7 and 28 days. The results exhibit that the initial strength growth for the compressive strength with increases with the percentage of the replacement up to 15%, being this behaviour more evident for the full water curing environment up to 67.53%. The 28- days compressive strength of the eggshell concrete for full water curing and open air curing were found at 49.23 MPa and 46.34 MPa respectively. However, the concrete specimens lost 24.7% and 34.83% when the eggshell powder replace up to 20% of the partial cement replacement for full water curing and open air curing. Thus, water curing is found to be more suitable compared to to open air curing.

Effect of Prewetted Pumice Aggregate Addition on Concrete Properties under Different Curing Conditions

This study researches the effects of different curing conditions on the properties of high strength concrete containing presoaked pumice aggregate (PA). Fine normal weight aggregate is substituted by an equal volume of 1h and 24h presoaked PA at 50% and 100% fractions and a total of five concrete mixtures were prepared. After kept in water, air and hot weather, the performance of concretes were evaluated by determining their physical and mechanical properties at 28 days. Hot weather was found to be the most detrimental condition where the highest strength drops were observed. Frost resistance of concretes was improved with the use of presoaked PA at 50% replacement ratio. The use of presoaked PA also decreased the shrinkage values of concrete specimens. The results showed that the use of presoaked PA in high strength concrete at 50% replacement ratio could contribute to concrete properties when exposed to inadequate curing conditions.

Effect of different curing conditions on flexural and compressive strength of fly ash mortars

Effect of different curing conditions on flexural and compressive strength of fly ash mortars

Influence of Slag on Water Resistance of Magnesia Phosphate Cement

Effect of different curing conditions on the mechanical properties of magnesium phosphate cement (MPC), and the water resistance of MPC was improved by adding slag, the influence of slag on component and microstructure of the hydrated product were studied in this paper. The additive amount of slag was 0% ,10% , 20%, 30% and 40% separately in the ratio of total amount of MPC. It indicates that the compressive strength and flexural strength increase by about 30%,40% when the amount of slag reaches 10% of phosphate cement, respectively , and the dissolution of some phosphate which has not reacted can be prevented when cured in water for days, it improves the pH value of the solution, so the main hydration product-MgKPO4·6H2O hard to be dissolved under alkaline environment resulting in the decreasing of porosity ,and the decrease of strength would be controlled.

Effect of Different Curing Conditions on the Mechanical Properties of UHPFC

Ultra-High Performance Fiber Concrete (UHPFC) is a new class of concrete. Because of its distinguished mechanical properties, UHPFC is considered as an ideal alternative material for use in developing new structural solutions. This paper discusses on influence of different curing conditions on mechanical properties of UHPFC. An experimental program was performed to study the mechanical properties of UHPFC which were cured under six different curing conditions. Test results indicated that steam and boil curing methods showed a promising performance particularly at early age of curing compared to other type of curing.

Study on the Effect of Curing Condition on the Performance of FBC Ash

The cementitious system containing FBC ash is usually associated with volume expansion when cured in the normal temperature, due to its relatively high SO3 content. This paper presents a further study on the effect of different curing conditions on the flexural and compressive strength of FBC ash-Portland cement clinker mortar and linear expansion ratio of FBC ash-Portland cement clinker paste. The results show that autoclaved curing is more beneficial to increasing mortar strength in early days than standard curing, but with slow strength development in later period. Moreover, autoclaved curing could decrease the expansion of FBC ash greatly. This study confirms that the expansion of FBC ash can be significantly inhibited by autoclaved curing.

Effect of Cure Conditions on the Generated Morphology and Viscoelastic Properties of a Poly(acrylonitrile–butadiene–styrene) Modified Epoxy–Amine System

The curing behavior, phase morphology, and dynamic mechanical characteristics of an epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenylsulfone (DDS), modified with different amounts of poly(acrylonitrile–butadiene–styrene) (ABS), were investigated by employing differential scanning calorimetry (DSC), field-emission scanning electron microscopy (FESEM), and dynamic mechanical thermal analysis (DMTA). The effects of different curing conditions on the generated morphologies and viscoelastic properties were evaluated. The amounts of ABS in the epoxy blends were 3.6, 6.9, 10, and 12.9 wt %. The rate of the curing reaction decreased with increasing thermoplastic content and with decreasing curing temperature. Morphological analysis revealed a phase-separated morphology for the blend systems. The storage modulus (E′), loss modulus (E″), and tan δ values of the systems were measured as functions of temperature and are discussed based on the morphological behavior of the epoxy blends with different amount of ABS.

The Sintering Behavior of Electrically Conductive Adhesives Filled with Surface Modified Silver Nanowires

Electrically conductive adhesives (ECAs) filled with sintered silver nanowires were prepared and the effect of different curing conditions on the electrical property of the ECAs was discussed. Silver nanowires with a diameter of 50–60 nm and a length of 2–3 μm were successfully synthesized through a polyol process and surface functionalized with dicarboxylic acid. Morphology studies showed that surface modified silver nanowires began to sinter at 200°C and became shorter and thicker, and eventually formed large chunks at higher temperatures. The conductive adhesives filled with 75 wt% of silver flakes and nanowires (3:2 weight ratio) were cured at different temperatures using two kinds of catalysts. The volume resistivity of the conductive adhesives cured at 300°C without a catalyst reached 5.8 × 10 –6 Ω cm. The dramatic improvement in the conductivity of the ECA is due to the sintering of silver nanowires and the high solid content resulting from the partial evaporation of polymer components.

Effect of curing mode on the polymerization characteristics of dual-cured resin cement systems

Objectives To evaluate the effects of different curing conditions on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] using infrared spectroscopy. Methods Four fourth generation products [Scotchbond Multipurpose Plus/RelyX (3M ESPE), Optibond/Nexus 2 (Kerr), All Bond2/Duolink (Bisco), and Bond-It!/Lute-It! (Pentron)], and three fifth generation materials [Bond1/Lute-It! (Pentron), Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Optibond Solo Dual Cure/Nexus 2 (Kerr)] were applied to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), direct light exposure through glass slide (DLE, XL3000/3M ESPE) or through pre-cured resin discs (shades A2;A4/2 mm thick/Z250/3M ESPE). Infrared spectra of the uncured cementing systems were recorded immediately after application to the ATR, after the system was light-cured or left to self-cure, and spectra were obtained 5 and 10 min later. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data ( n = 5) were analyzed by two-way repeated measures ANOVA and Tukey's test ( p = 0.05). Results Changes in aliphatic-to-aromatic peak ratios before and after placing RC onto the BA demonstrated that a combined layer was created. All groups exhibited higher DC after 10 min than after 5 min, except the DLE group of Bond-it!/Lute-it!. No significant differences in DC were observed among light-activated groups regardless of the resin disc shade in three of the four fourth generation cementing systems. The SC groups exhibited lower DC than the DLE groups for both fourth and fifth generation products either after 5 or 10 min. Conclusion The chemistry of the bonding interface changed when RCs were applied to uncured BAs. The presence of an indirect restoration can decrease the DC of some cementing systems and the self-curing mode leads to lower DC than the light-activating one.

Multiplexing frequency mode study of packaging epoxy molding compounds using dynamic mechanical analysis

Dynamic mechanical analysis (DMA) measures mechanical properties (modulus and damping) of viscoelastic materials over a spectrum of time (or frequency) and temperature. This paper reports its use to study four epoxy molding compounds (EMC1A, 1B, 2 and 3) for electronic packaging industry using multiplexing frequency (or multiple frequency) mode DMA. The raw epoxy molding compounds were processed under 1 min transfer mold curing (TMC) but different post-mold curing (PMC) conditions. Viscoelastic properties over temperature at fixed oscillatory frequency of the compounds were studied. Specimen EMC1B with longer PMC (4 h) resulted in higher glass transition temperature ( T g) compared to EMC1A (0 h PMC) of the same brand of material. The other two brands of epoxy molding compounds EMC2 and EMC3 behave differently from EMC1 as shown from their T g variations. It was observed that T g’s of all compounds studied were generally increasing with higher oscillatory frequency DMA temperature sweep. Activation energies ( E a) at T g relaxation process of compounds were calculated from Arrhenius plots, log f versus 1/ T g. Effects of different curing conditions of compounds on E a were also discussed. It was noticed that EMC1B after 4 h PMC resulted in E a of about 3.4 times higher than EMC1A (0 h PMC). Application of time–temperature superposition (TTS) technique to the multiplexing frequency mode analysis of the cured epoxy molding compounds was illustrated. Master curves, of modulus as a function of oscillatory frequency of the compounds, were therefore constructed and generated at temperature interval of 20° of each compound. Performance of specimens at specific operating conditions can be predicted and compared.

Investigation on soaking and formation of lead/acid battery plates with different mass structure

The influence of paste density and curing temperature on soaking and formation was investigated by different analytical methods including X-ray, porosimetry, BET and SEM. The soaking was carried out in sulfuric acid with different gravity and the time was varied between 0.5 and 24 h. Plates cured at high temperature resulting in mainly tetrabasic lead sulfate (4BS) behave markedly different to those cured at low temperature having only tribasic lead sulfate (3BS). The behaviour of plates cured at medium temperature resulting in a mix of both 4BS and 3BS was between the two extremes. There was also some influence of the paste density but smaller than the effect of different curing conditions. The results can be explained by considering the different mass structure and pore size distribution of the respective plate version.

Thermal Properties and Transient Thermal Analysis of Structural Members During Hydration

This paper presents an experimental study on the thermal properties of concretes with different strengths at very early ages (during hydration). The heat of hydration, thermal conductivity, specific heat, and coefficient of thermal expansion were investigated for 30 MPa, 70 MPa, and 100 MPa concretes. Subroutines were developed for a finite element thermal analysis program DETECT to predict the variation of temperatures during hydration as a function of maturity, based on Arrhenius' approach. An experimental study was performed to observe the effects of different curing conditions and early form stripping on the temperature development in structural concrete members. Comparisons are made between the measured and predicted temperatures in slabs and large concrete columns.

Effects of different curing conditions on slow crack growth in cement paste

Portland cement paste was prepared in the following five ways: (1) cured in fresh water, (2) made with fresh water, cured in sea water, (3) made and cured in sea water, (4) low-pressure steam cured, (5) high-pressure steam cured. The water-cement ratio was 0.4 in all cases. Slow crack growth was studied by the double torsion method, and plots were made of crack velocity versus stress intensity. Fracture toughness and the modulus of elasticity were also measured by flexural beam methods. The steam cured specimens had lower fracture toughness and were somewhat more sensitive to static fatigue than the room-temperature cured specimens. There was evidence that crack growth is aided by the presence of water in the environment or by increased water-cement ratio.

The effect of curing conditions on the physical properties of concrete

Summary An investigation has been carried out to study the effect of different curing conditions on certain physical properties of concrete. The conditions ranged from a temperature a little above freezing to that of high-pressure steam, and included normal and tropical temperatures. The properties measured included crushing strength, dynamic and static moduli, ultrasonic pulse velocity and modulus of rupture.