Effect Of Curing Conditions Research Articles

Effect of Curing Condition and Solvent Content on Mechanical Properties of Zein-Biopolymer-Treated Soil

The curing condition and solvent composition of biopolymer binders may impact their efficacy for soil stabilization. This study introduces a novel hydrophobic biopolymer, zein, and investigates the effects of solvent and curing conditions on the mechanical properties of zein-treated soils. The zein biopolymer is used to prepare cohesionless soil with various ethanol contents. Unconfined compressive strength and microscopic tests are used to investigate the treated specimens under two different curing conditions. The mechanical properties of the treated specimens are evaluated in terms of compressive strength and the secant elastic modulus. The experimental results show that the compressive strength and elastic modulus increase with the curing period under both curing conditions. Higher curing temperature improves the compressive strength of biopolymer-treated specimens. The linear relationship between compressive strength and the elastic modulus of zein-treated soils shows higher strength and a lower elastic modulus compared to rock. Furthermore, the zein biopolymer shows significant strength improvement compared to the existing biopolymers, including casein and lignin. Thus, the effects of solvent and curing conditions on the mechanical properties of zein-treated soil should be considered for its application to soil stabilization.

Post-Cure Development of the Degree of Conversion and Mechanical Properties of Dual-Curing Resin Cements.

This study investigated the effect of different curing conditions on the degree of conversion and mechanical properties of contemporary dual-curing resin cements. The material specimens were either light-cured directly, light-cured through a 1-mm lithium disilicate glass-ceramic layer, or self-cured. The degree of conversion was measured in 0.1-mm films using Fourier-transform infrared spectroscopy 1 day, 7 days, and 28 days post-cure. Specimens used to study the flexural strength and modulus were prepared according to the ISO 4049 protocol, stored for 28 days post-cure, and subjected to accelerated aging by absolute ethanol immersion. The degree of conversion values ranged between 44.3–77.8%. Flexural strength varied between 11.4–111.1 MPa, while flexural modulus amounted to 0.7–5.5 GPa. The degree of conversion was significantly affected by material type, curing conditions, and post-cure time; however, variations in curing conditions were the least influential factor. A statistically significant effect of curing conditions on the degree of conversion was identified for only one of the five materials tested, whereas the flexural strength and modulus of all tested materials were significantly reduced in the experimental groups that were light-cured through a ceramic layer or self-cured. The effect size analysis showed that mechanical properties were most affected by the material type, while the differences in curing conditions were less influential. A comparison of the degree of conversion and mechanical properties indicated that different curing conditions may lead to significantly different flexural strength and modulus, which are not necessarily accompanied by identifiable variations in the degree of conversion.

Effect of curing condition on mechanical properties of scarf-repaired composite laminates

Composite structures are generally pressurized at both sides when repaired by the scarf repair method. But single-face vacuum bag curing (SVC) may be used in some practical scarf repair of penetration damage due to the low accessibility of composite structures, which can decrease bonding quality and may reduce structural mechanical properties. In this paper, experimental investigations were conducted on tensile and compressive properties of scarf-repaired composite laminates using SVC and double-face vacuum bag curing (DVC) in four hygrothermal environments. Finite element models of composite scarf joints with voids were established to further explore the failure mechanism of scarf-repaired laminates. Results show that the curing condition hardly affects tensile and compressive properties of the repaired laminates though it significantly affects the bonding quality with adhesive inner voids. Failure loads of scarf joints almost keep unchanged with adhesive voids increasing.

Curing Time and Temperature Effect on the Resistance to Wet-Dry Cycles of Fly Ash Added Pumice Based Geopolymer

The effects of curing regimes varying combinations of temperatures (ambient, 60 °C, 75 °C, 90 °C, 105 °C) and durations (4h, 8h, 24h, 48h, 96h, 168h) on the performance of fly ash added pumice based geopolymer pastes were investigated in this study. The precursor raw material consists of 70% pumice dust and 30% fly ash (FA). Alkali activator was prepared by mixing 10M sodium hydroxide (SH) solution and liquid sodium silicate (SS) in the ratio of SS/SH=2. Activator to precursor ratio was fixed as 0.45. Compressive strengths were determined at the 28 days of age as well as after exposure 5 wetting-drying (w-d) cycles. In addition, Fourier Transform Infrared Spectroscopy (FTIR) tests were conducted on the fresh and hardened geopolymer pastes in order to examine the effect of curing conditions to the structural changes and reaction products. The results show that in the case of 60 °C and 75 °C, the strength of the w-d conditioned samples increased steadily as the curing time increased. However, longer curing times of more than 24 hours are not beneficial for high curing temperatures (90 °C and 105 °C). The maximum strength after the w-d cycles is obtained for the curing conditions of 60°C/168h (74.4 MPa). Also, FTIR analysis confirmed that the hardened geopolymer paste transformed into a more coordinated structure and soluble carbonate compounds were reduced at 60 °C and 168 hours curing condition.

Effect of curing conditions during the first 24 hours after casting on the properties of mortar mixtures

As it is well known, the curing method directly affects many properties of cementitious composites. In previous studies, the effect of different curing conditions on the properties of the cementitious systems has been generally investigated in the period after first 24 hours after casting. However, there are not many studies in the literature related to the effects of curing conditions on the specimens kept in mold during 24 hours after casting. In this study, strength development, ultrasonic pulse velocity (UPV) and water absorption capacity of mortar specimens subjected to steam-curing at different temperatures during keeping in mold for the first 24 hours after production were compared. In this regard, all mortar specimens were exposed to curing in a steam-curing cabin at 95% constant relative humidity (RH) under 5 different temperatures such as 20, 35, 50, 65 and 80˚C for the first 24 hours after the specimens were placed into the molds. Afterwards, the specimens were removed from the molds and cured in water conformed to the standard until the testing day. In this context, the water-cement ratio, sand-binder and slump-flow value of all mortar mixtures were kept constant as 0.485, 2.75, 25±2 cm, respectively. As a result, the application of steam-curing at high temperature for the first 24 hours positively affected the 1-day compressive strength and UPV values of the mixtures, while the 3,7 and 28-day compressive strength, UPV values and the 28-day water absorption capacity of mixtures were adversely affected.

Effect of Curing conditions on the Compressive Strength of Spent Fluid Catalytic Cracking Catalyst (SFCCC)-based Geopolymers

This research evaluates the effect of the curing conditions on the mechanical properties of geopolymers containing spent fluid catalytic cracking catalyst (SFCCC) generated as a waste by the Peruvian oil-refinery industry. For this purpose, two curing conditions were evaluated: i) sample sealing during oven curing to avoid water loss, and ii) the time before curing (pre-curing time or delay time, before heating). The curing temperature was varied from 25°C up to 100°C. The performance of samples was assessed measuring the compressive strengths and the bulk densities. The results reveal that there are optimal curing conditions associated with the higher compressive strength of the SFCCC-based geopolymers. This optimal condition occurred when water loss was reduced by sealing, and samples were allowed to rest before curing (pre-curing). These two conditions assured not only a higher compressive strength but also a denser and more homogeneous product. The results indicate that the higher compressive strengths (up to 34.5 MPa) and bulk densities (up to 1.6 g/cm3) were obtained when the specimens were sealed with plastic bags during the curing process to avoid moisture loss and when they were subjected to a pre-curing period of 24 hours before heating in an oven at 50°C for 1 day followed by curing at room temperature for 6 days.

Evaluation of effects of multi-varied atmospheric curing conditions on compressive strength of bacterial (bacillus subtilis) cement mortar

Addition of calcite-producing bacteria is a relatively new technique used globally to produce self-healing concrete/cement mortar as well as to increase compressive strength and durability. Due to different atmospheric conditions around the world, the performance of these bacteria will vary due to different curing conditions. In this study, the effects of different atmospheric curing conditions on the compressive strength of bio cement mortar (BCM) are examined. The atmospheric conditions (curing) are varied by combining different temperature and relative humidity, and wind speed and sunlight exposure time. The microorganism used is Bacillus subtilis, and it is added to concrete mortar through direct mixing. The concentration of the bacteria solution is 109 cells/ml and two volumes of 30 ml and 50 ml are applied. Two control specimens - water-cured bio cement mortar (BC) and water-cured cement mortar (NC), are made to serve as baselines for comparison and evaluation of the effects of the curing conditions. The results showed that increased temperature, relative humidity and wind speed increased the compressive strength of BCM. However, increased sunlight exposure time decreased the compressive strength. The results indicated that atmospheric conditions influence the performance of bacteria in BCM. The BCMs had higher 7 and 28 days compressive strength than the control sample (water-cured cement mortar). The minimum and maximum 7 day increments were 53.7% and 120.6% respectively, while the 44.9% and 130.6% respectively were the 28 day. The results show that calcite-producing bacteria improves the compressive strength of cement mortar, however, the environmental curing conditions of the produced BCM will influence the calcite-producing ability of the bacteria.

Effect of vacuum mixing and curing conditions on mechanical properties and porosity of reactive powder concretes

Abstract The paper contains quantitative characteristics of changes in the porosity and mechanical properties of RPCs caused by applying different pressures during concrete mixing, i.e. atmospheric pressure and pressure reduced to 500 and 40 mbar. The effect of curing conditions was determined as well: the impact of curing in water (Tmax = 20 °C), steaming (Tmax = 90 °C) and autoclaving (Tmax = 250 °C) on the porosity, compressive strength and flexural tensile strength of the materials tested. In addition, the maximum volumetric proportion of 6 and 14 mm steel micro-fibres which can be introduced in a standard manner, i.e. during the production of the RPC mix, was determined depending on their length. Besides the basic mechanical characteristics, tests of mechanical properties of RPCs containing fibres included the determination of the following parameters: σLOP (limit of proportionality), σMOR (modulus of rapture), Wf (work of fracture) and the toughness indices. Test results clearly confirm the considerable impact of pressure during RPC mixing and curing conditions on the durability and mechanical properties of the hardened composites. The maximum volumetric proportion of micro-fibres introduced during mixing was 8%. Steel fibre reinforcement was found to be more effective when longer fibres were used.

양생조건이 고로슬래그 미분말을 혼입한 시멘트 콘크리트의 염화물이온 확산계수에 미치는 영향

양생조건이 GGBFS를 사용한 시멘트 콘크리트의 염화물이온 확산계수에 미치는 영향에 대한 연구를 진행하였다. 양생조건은 기중양생 (20±2℃, RH 60±5%)과 수중양생 (20±2℃)으로 구분하였으며, GGBFS 치환율은 0%(대조군), 30%, 60%로 구분하여 3가지 배합의 콘크리트를W/B 40%, 50%, 60%로 구분하여 제작하였다. 시험은 콘크리트 압축강도평가, 염화물이온확산계수 평가를 실시하였다. 콘크리트의 압축강도는 GGBFS 치환율이 증가할수록 수중양생 대비 기중양생 시험체의 압축강도의 발현율이감소하였다. 염화물이온확산계수 측정결과 GGBFS치환율이 증가할수록 염화물이온 확산계수가 감소하였지만, 수중양생대비 기중양생 시험체의 콘크리트 염화물이온 확산계수는 증가하여 최대 111%까지 증가하는 것을 확인하였다.

Thiol-ene microfluidic devices for microchip electrophoresis: Effects of curing conditions and monomer composition on surface properties

Thiol-ene polymer formulations are raising growing interest as new low-cost fabrication materials for microfluidic devices. This study addresses their feasibility for microchip electrophoresis (MCE) via characterization of the effects of UV curing conditions and aging on the surface charge and wetting properties. A detailed comparison is made between stoichiometric thiol-ene (1:1) and thiol-ene formulations bearing 50% molar excess of allyls (“enes”), both prepared without photoinitiator or other polymer modifiers. Our results show that the surface charge of thiol-ene 1:1 increases along with increasing UV exposure dose until a threshold (here, about 200J/cm2), whereas the surface charge of thiol-ene 2:3 decreases as a function of increasing UV dose. However, no significant change in the surface charge upon storage in ambient air was observed over a period of 14 days (independent of the curing conditions). The water contact angles of thiol-ene 2:3 (typically 70–75°) were found to be less dependent on the UV dose and storing time. Instead, water contact angles of thiol-ene 1:1 slightly decrease (from initial 90 to 95° to about 70°) as a function of UV increasing exposure dose and storing time. Most importantly, both thiol-ene formulations remain relatively hydrophilic over extended periods of time, which favors their use in MCE applications. Here, MCE separation of biologically active peptides and selected fluorescent dyes is demonstrated in combination with laser-induced fluorescence detection showing high separation efficiency (theoretical plates 8200 per 4cm for peptides and 1500–2700 per 4cm for fluorescent dyes) and lower limits of detection in the sub-μM (visible range) or low-μM (near-UV range) level.

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 Effect of Cure Conditions on the Strength of Ebonite Rubber Network

Abstract Although ebonite has been discovered for a long time, its applications were still limited to some household products. Recently, ebonite rubber has become of interest, especially for structural applications due to its high and adjustable strength and rigidity. The rigidity can be enhanced by several folds by utilizing appropriate curing conditions. In this study, we investigate the effect of curing conditions on the mechanical properties of ebonite at various cure time. Here, the crosslink densities were determined qualitatively both before and after compression cycles to investigate the change in crosslink networks. After the pre-molding stage, the curing process was either continued in the compression mold, in the air-oven, or under nitrogen atmosphere. For the compression-mold and nitrogen-atmosphere curing, crosslink densities and the compressive moduli increased significantly with cure time, whereas, for air-oven curing, only slight increases in the afro-mentioned properties were observed. After completing four compression cycles, the crosslink density and mechanical properties remain high only when curing was done in the compression mold. Therefore, curing under pressure as in the compression mold for a prolonged time could be a mean in boosting the mechanical properties of ebonite.

The Effect of Cure Conditions on the Performance of Styrene Butadiene Rubber for Industrial Conveying Applications

AbstractA range of samples were prepared from a commercial styrene butadiene rubber (SBR), over a range of cure temperatures (140d̀C‐170d̀C) and cure times (30–120 min), using a high temperature moulding press held at a constant pressure of 5000 psi. Mechanical analysis of the various samples showed considerable increase in modulus, shore hardness and break strength with progressive increase in cure temperature, especially at lower cure times. Dynamic frictional analysis under different loadings, of the SBR samples with High Molecular Weight Polyethylene (HMWPE) and 90 Shore A Polyurethane (PU), showed a progressive decrease in frictional force with increase in SBR cure temperature and time. Some reversion of the SBR was shown to occur at higher temperatures and longer cure time

Effect of curing conditions and Lactobacillus casei CRL705 on the hydrolysis of meat proteins.

The effect of the common curing conditions used during the manufacture of dry fermented sausage on the proteolytic activity of Lactobacillus casei CRL705 against meat proteins was investigated. Hydrolysis of pork muscle sarcoplasmic and myofibrillar proteins was evaluated by SDS-PAGE and reverse phase-HPLC analysis. Ascorbic acid exerted a stimulatory effect on both sarcoplasmic and myofibrillar protein breakdown by Lact. casei CRL705 with the release of hydrophilic peptides and free amino acids, while NaCl and NaNO2 mainly stimulated myofibrillar degradation. Even when processing temperature (25 degrees C) did not positively affect bacterial protein hydrolysis, the presence of curing salts accounted for a remarkable increase in the non-volatile components that constitute taste-active compounds that strongly influence the final flavour of the product. To predict the suitability of Lact. casei CRL705 and its proteolytic enzymes as a starter culture for the dry processing of dry fermented sausages.

Effects of curing conditions on properties of concrete using slag replacement

The effects of curing conditions on properties of slag cement concrete were studied. Autoclaving (175°C, 0.5 MPa) and steam curing (80°C) were compared to normal curing (28 days, 20°C, and 100% RH). Four different concrete mix designs with the same mix proportions and different cement replacements were used: 0% slag (control), 25% slag, 50% slag, and 75% slag. The effects of slag replacement and curing conditions upon concrete properties were examined. The properties examined included mechanical properties (compressive and tensile strength), transport properties (chloride permeability and chloride penetration), and microstructural properties (pore structure and phase composition). There is little effect of slag replacement up to 50% upon strength, whereas higher replacement results in a drop in compressive strength. Steam curing reduces the compressive strength compared to the other curing types considered in this study. Chloride permeability and penetrability significantly decrease with increasing slag replacement except for autoclave curing, which is the least sensitive with respect to slag replacement compared to the other curing types considered in this study. The addition of slag reduces the continuous pore diameter, which correlates well with the initial current (IC) measured by the rapid chloride permeability test (RCPT).

The Effects of Cure Conditions on the Relaxation Behavior of Thermosetting Adhesives

Abstract The ability to dissipate mechanical energy by plastic (viscous) deformation is an important strength consideration for structural adhesives. The bulk solid viscosity parameter, μ, used in spring-dashpot mechanical-model characterization of polymeric materials, provides a convenient measure of this capability. The viscosity parameter, in turn, can be related to the relaxation time for the material with the use of the elastic modulus. This paper presents a study of the effects of cure temperature and time on the stress relaxation behavior of Metlbond 1113 modified-epoxy adhesive with carrier cloth. Short term (t=1/2 minute) relaxation data are successfully fitted with the modified Bingham mechanical model to obtain relaxation time and bulk solid viscosity parameter values corresponding to different cure conditions. Experimental results indicate that both the relaxation time and the bulk viscosity values behave in a bell-shaped increasing-decreasing manner with respect to the cure temperature for al...

Effect of curing conditions on the total water content of hardened portland cement paste

AbstractThe effect of various curing conditions on the amount of water held by pastes with low water/cement ratios was investigated. It was concluded from the results that factors significantly influencing the total water content of a cement paste made with ordinary Portland cement and cured at room temperature are: water/cement ratio, curing medium, curing period and curing history.

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.