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The pre-bored grouted planted (PGP) pile shaft consists of a core PHC pile and the surrounding cemented soil column. The shaft capacity of PGP pile is controlled by the PHC pile–cemented soil–soil interface. In this paper, the effect of curing time on the frictional capacity of smooth concrete pipe pile–cemented soil interface was investigated through pile–soil interface shear tests. The test results show that the peak skin friction of pipe pile–cemented soil interface increased with the curing time. Nevertheless, the normalized peak skin friction (peak skin friction/cemented soil strength) of interface decreased with the curing time. The thickness of the cemented soil layer had a large effect on the residual skin friction of pipe pile–cemented soil interface. The scale effect also existed in the smooth concrete pipe pile–cemented soil interface shear tests, as the stiffness and shear strength of interface would decrease with the pipe pile diameter, which would eventually induce the decrease of radial confining pressure of the interface. [ABSTRACT FROM AUTHOR]

In this paper, magnesium oxide (MgO) and potassium dihydrogen phosphate (KH2PO4) were used as the solid phase components of magnesium phosphate bone cement, and different content of phytic acid modified hydroxyapatite (IP6-HA) powder was introduced to prepare various magnesium phosphate composite bone cement with different magnesium and phosphorus ratio (M: P). By adjusting the ratio of MgO and KH2PO4 in magnesium phosphate powder and the content of IP6-HA, the mechanical properties and curing time of bone cement were improved, and the curing mechanism of bone cement was studied. The results show that when the ratio of magnesium to phosphorus is 4 and the content of IP6-HA in the solid phase is 5% (mass fraction), the growth effect of struvite crystals (MgKPO4 · 6H2O) is the best, the curing time is 7. 5 min, the compressive strength can reach 49 MPa, and the strength can reach 69. 3 MPa after curing for four weeks. The IP6-HA modified magnesium phosphate composite bone cement obtained from the experiment has good mechanical properties and suitable curing time, which has potential biomedical application prospects. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water retention is an important soil property affecting the hydro-mechanical behavior of unsaturated soils. This study investigated the water retention property and the microstructure of lime-treated Ili loess from Xinjiang in China. Such material is a typical central Asian loess characterized by high salt content and strong collapsibility. The matric suction and total suction were measured by the filter paper method and saturated salt solution method. The microstructure characteristics of untreated and lime-treated loess were analyzed by scanning electron microscopy and mercury intrusion porosimetry, and the influence of the microstructure variation on the macroscopic water retention property was analyzed by introducing the parameter of fractal dimension, which is commonly used to describe the characteristic of pore shape and size. Results showed that, along the curing time, the lime treatment induced a change of the soil microstructure in terms of pore distribution with a consequent increase of the matric suction and overall water retention capacity. However, the osmotic suction decreased during curing. During curing, the lime treatment reduced the percentage of macro-pores and increased the nano-pores. Then, the soil microstructure was characterized by the fractal dimension, which increased with the curing times. Finally, the proposed fitting model of water retention consisting in introducing the fractal dimension into the Van-Genuchten model appeared adequate with good accuracy. [ABSTRACT FROM AUTHOR]

Fine-grained soils cause problems for forest road construction and often require improvements of their mechanical properties. One of the methods of improving mechanical properties of clay soils is soil stabilization. In this study, the effect of a conventional (lime) and a non-conventional (sodium nanoalginate) stabilizer on improving the characteristics of a high plasticity forest soil was compared. Atterberg limits including liquid limit, plastic limit and plasticity index, standard Proctor, UCS (Unconfined Compression Strength) and CBR (California Bearing Ratio) tests were performed on control (untreated) and soil samples treated with different doses (3%, 5% and 7%) of lime and sodium nanoalginate, according to the standard procedures. Moreover, to evaluate the effect of curing time, additional tests were performed on the soil samples treated with 3% lime and 3% sodium nanoalginate at 7, 14 and 28 days after the treatment. The results indicated that adding sodium nanoalginate and lime to the forest soil improves the Atterberg limits. Additionally, adding sodium nanoalginate to the forest soil increases the maximum dry density (γdmax) and decreases the optimum moisture content (OMC), whereas adding lime to the forest soil reduces the maximum dry density and increases the optimum moisture content. Adding sodium nanoalginate and lime in different doses (3%, 5% and 7%) increased UCS and CBR as the main indices of soil strength. The increment range of UCS for the soil stabilized with sodium nanoalginate and lime was 42.59%–160.14% and 31.34%–56.65%, respectively, and the range of CBR improvement for soil stabilized with sodium nanoalginate and lime was 28.72%–122.97% and 13.83%–45.59%, respectively. Increasing the curing time improved the mechanical properties of the forest soil in the samples treated with both stabilizers, but sodium nanoalginate performed better in soil stabilization. [ABSTRACT FROM AUTHOR]

In this paper, a time-dependent key parameter is proposed to estimate the unconfined compressive strength (UCS) of a typical sand treated with cement and zeolite. To this end, the data of a series of unconfined compression tests were collected from previous works on the sand specimens treated with the addition of stabilizers, including either only cement or cement and percentages of cement replacement with natural zeolite, in multiple curing times. Afterward, a state-of-the-art time-dependent active composition (ACnew) parameter was defined to predict the UCS characteristics of the treated soils. In the definition of the ACnew parameter, a hyperbolic function was employed to correlate the development of pozzolanic reaction triggered by active components (CaO and SiO2 + Al2O3) with time. Through the proposition of the ACnew parameter, the impact of the time-dependency of the zeolite treatment on the behavior of the stabilized specimens and the development of the pozzolanic reaction as well as the variation of UCS with increasing curing time are adequately justified. Finally, it is indicated that incorporating porosity (η) and ACnew in the form of power functions represents a considerable estimation of the UCSs of the studied treated sand in comparison to previous empirical correlations. [ABSTRACT FROM AUTHOR]

Abstract The cement paste is subjected to various loads throughout a well’s life, which may compromise some of its essential characteristics and impair its performance. When the cement paste is first being formed and the cement’s characteristics have not yet fully matured, these loadings take on greater importance. In this study, the early properties of cement used in oil wells that contains polypropylene fiber are assessed. Five different curing times were used to prepare ten cement samples (6, 12, 24, 48, and 72 h). Five samples contained polypropylene fiber, while the remaining five samples were without polypropylene fibers. After the samples were prepared, the examination of several early cement properties took place. Nuclear magnetic resonance (NMR) was used to describe each sample in order to determine how the curing times affected the cement’s porosity. The findings demonstrated that both cement systems’ compressive and tensile strengths increased with curing time, and that adding polypropylene fiber enhanced the cement’s strength. The porosity and permeability of the cement specimens were significantly reduced with the incorporation of polypropylene fibers, as well as with time during the curing process for both cement samples. The reduction of Young’s modulus and the increase in Poisson’s ratio show that the addition of polypropylene fibers also makes the cement more elastic. To express variations in porosity as well as compressive and tensile strengths, logarithmic relationships were constructed. While the Poisson’s ratio, Young’s modulus, density variations, and permeability were precisely modeled by power-law equations.

The conventional covalent crosslinking has been commonly utilized in rubber/clay nanocomposite, but stronger crosslinking bonds such as coordination crosslinking should be introduced to further improve the mechanical properties. Herein, we first prepared the nitrile butadiene rubber (NBR)/clay nanocompound via gel compounding method, and then copper sulfate pentahydrate (CSP) was introduced to prepare NBR/clay/CSP nanocomposites via the coordination crosslinking. The nanocomposites with higher CSP content and more curing time exhibited higher crosslinking density and glass transition temperature, because more rubber chains were immobilized by the CSP particles. Similar effect on mechanical properties was found by increasing the CSP content and by prolonging the curing time. By optimizing the curing time, the best mechanical properties was achieved for the NBR/clay10/CSP20 nanocomposite cured for 70 min with tensile strength of 37.4 MPa and elongation at break of 354%, which was far beyond the ordinary rubber/clay nanocomposites.

The existence of silty sand in the infrastructure under concrete constructions, hydraulic structures, and irrigation systems has always caused challenges. Improving this kind of soil is always a challenging approach to increase compressive strength and shear stress. There is a conception that adding some extra material such as concrete can increase the stability of this soil against contributed forces. The present study investigated the effects of curing time (3, 7, 14, 21, and 28 days) and different percentages of various additives (3%, 5%, and 7%) on the strength of the silty sand soils. A series of laboratory tests were carried out to measure the Uniaxial Compressive Strength (UCS) and California Bearing Ratio (CBR) by evaluating the effect of additives on the strength parameters of silty sand soil. In total, 299 experimental tests have been conducted in the soil mechanics laboratory of SRBIAU. Results indicated that adding additives such as concrete to silty sand soil improved significantly the compressive strength and shear strength. The comparisons among the experimental test illustrate that due to increasing the curing time, the aforementioned parameters were increased significantly; however, Confix and Bentonite aggregates did not have a marginal effect on the compressive strength and shear strength. Also, after the 21st day of the curing time, the rate of increment of the UCS and CBR reached slightly and then attained a constant value. Also, after this duration, the curing time is an independent factor in the variation of the UCS and CBR tests. Furthermore, the addition of 5% Pozzolana cement and 7% Portland cement with 28 days of curing had the highest CBR number and UCS resistance of 176.26 and 17.58 kg/cm2, respectively. Also, the sketch of the different failure patterns was shown during the curing time. Finally, by increasing the curing time, the behavior of specimens from semi-brittle to brittle made them harder.

Copyright of Journal of Shenzhen University Science & Engineering is the property of Editorial Department of Journal of Shenzhen University Science & Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article explores the effectiveness of the Pull-off Tensile Strength (POTS) test as a tool for evaluating the moisture damage resistance of asphalt mixtures. Currently, indirect tensile strength (ITS) and the Hamburg Wheel Tracking (HWT) test are used, but they have limitations such as expensive equipment and being heavy. The POTS test is a low-cost and portable alternative. This study investigated the effect of curing time and resting time on the POTS of asphalt-aggregate systems by subjecting samples to different curing times and resting times before testing their tensile strength under dry and wet conditions. The results show that the tensile strength decreases with increasing curing time or exposure to water, indicating that the debonding process between asphalt and aggregates occurs more rapidly with aging. The tensile strength ratio (TSR) of the POTS test for all three asphalt binder types increases with resting time and curing time, with the highest values observed at a curing time of 2 h and a resting time of 5–15 min. Additionally, this study found a strong linear relationship between the tensile strength ratios of ITS and POTS tests, regardless of curing time and resting time. Overall, the POTS test is a promising alternative for evaluating moisture damage resistance in asphalt mixtures. [ABSTRACT FROM AUTHOR]

Biodegradable polymers have been widely used in tissue engineering for their good biocompatibility, controlled mechanical properties and processability. Among them, poly(glycerol sebacate) (PGS) is a promising biodegradable polymer that has been used in diverse tissue engineering applications such as skin, muscle, cornea, nerve, vessel, cartilage, and so on. However, one of the synthesis parameters, curing time on PGS properties is still a confusing problem waiting to be resolved. In this article, PGS was cured for 0, 24, 36, 48, 60, 72, 84, and 96 h at 130°C and their properties were characterized by a series of techniques. Differential scanning calorimetry results indicated that the melting point, crystallization temperature, melting enthalpy and crystallization enthalpy of PGS decreased with the increase of curing time. Curing time was positively correlated to the degree of crosslinking. Longer curing time not only enhanced Young's modulus of PGS but also reduced its hydrophilicity. The Young's modulus of PGS curing for 96 h was about 5 times higher than that of PGS curing for 36 h. This study suggests that the effect of curing time on PGS properties provides detailed reference for potential applications. [ABSTRACT FROM AUTHOR]

The cement paste is subjected to various loads throughout a well's life, which may compromise some of its essential characteristics and impair its performance. When the cement paste is first being formed and the cement's characteristics have not yet fully matured, these loadings take on greater importance. In this study, the early properties of cement used in oil wells that contains polypropylene fiber are assessed. Five different curing times were used to prepare ten cement samples (6, 12, 24, 48, and 72 h). Five samples contained polypropylene fiber, while the remaining five samples were without polypropylene fibers. After the samples were prepared, the examination of several early cement properties took place. Nuclear magnetic resonance (NMR) was used to describe each sample in order to determine how the curing times affected the cement's porosity. The findings demonstrated that both cement systems' compressive and tensile strengths increased with curing time, and that adding polypropylene fiber enhanced the cement's strength. The porosity and permeability of the cement specimens were significantly reduced with the incorporation of polypropylene fibers, as well as with time during the curing process for both cement samples. The reduction of Young's modulus and the increase in Poisson's ratio show that the addition of polypropylene fibers also makes the cement more elastic. To express variations in porosity as well as compressive and tensile strengths, logarithmic relationships were constructed. While the Poisson's ratio, Young's modulus, density variations, and permeability were precisely modeled by power-law equations. [ABSTRACT FROM AUTHOR]

Soil stabilization techniques have been widely used to improve the mechanical and engineering properties of soft ground, such as strength, compressibility, and permeability. Recently, dredged soils that have high water content, high compressibility, and low strength have been mixed with cement and used as filling and landfill materials. The water and cement contents and soil types (clay or silt) in these soil–cement mixtures can be determined according to the purpose of use. To this end, the design of these mixtures requires the accurate prediction of the unconfined compressive strength (qu). Therefore, this paper proposes a predictive model for qu of cement-treated fine-grained soils (CTFSs) for ground improvement and stabilization of dredged soils. Ordinary Portland cement and two types of fine-grained soils (clay and silt) were used as the basic materials in the experiment. Unconfined compression tests were performed in a wide range of experiment conditions: water content (wt: 40–170 %), cement content (c: 5–25 %), and curing time (t: 3–90 d), and the results were correlated by two key parameters, wt/c (total water content/cement ratio) and s/c (soil/cement ratio). The results demonstrated that wt/c and s/c were strongly correlated with the qu development of CTFSs depending on the curing period. Therefore, we established a predictive model for qu by combining the power and exponential functions for (s/c)X and (wt/c)Y. The X and Y values of proposed model could equally be applied for different curing periods for soils of different types with different characteristics. In addition, the proposed model could predict long-term qu by using the time coefficient (ct) normalized by the curing period of 7 d. The mean absolute percentage error and coefficient of determination of the proposed model were lower and higher, respectively, than those of the reported data. Overall, the proposed predictive model is a promising tool for predicting the qu of CTFSs, for instance, for ground improvement and cement-treated dredged soils.

In the present study, experimental investigations on the influence of mixing water content used for the preparation of mortar mix using factory-made dry-mix mortar dedicated to bricklaying with clinker masonry units are presented, as well as the curing time on flexural bond strength of masonry made of these two materials. The flexural bond strength was tested using the "wrench test" method. The masonry tests specimens were prepared using three volumes of mixing water as follows: 4.0 L (the value recommended by the mortar manufacturer); 4.5 L; and 5 L of tap water per one 25 kg bag of dry pre-mixed mortar. The influence of the mixing water content was analyzed in relation to curing time. All masonry specimens were tested in four series after 9, 14, 21, and 28 days of sample curing. The results showed that the use of 6 and 18% more mixing water than recommended by the manufacturer (4.5 and 5 L per bag) adversely affected flexural bond strength. Moreover, for all three mixing water amounts, it was found that the maximum values of bonding strength were reached after 9 days of curing, which decreased over time. The largest decreases (30–40%) were recorded after 14 days. After 21 days, these values continued to decrease, but more slowly. The final value of the ratio of bond strength to flexural strength of the mortar was similar for all amounts of mixing water and for the 28-day curing time, it oscillated around 0.2. [ABSTRACT FROM AUTHOR]

In this work novel thermosetting resins with high bio‐based content have been developed derived from chia seed oil (CO). Epoxidized chia seed oil (ECO) was used as bio‐based epoxy matrix with different mixtures of crosslinker agents, that is, methyl nadic anhydride (MNA) as petroleum‐derived and maleinized chia seed oil (MCO) as bio‐based crosslinker. The chemically modified oils from CO, that is, ECO and MCO, and MNA were analyzed by titration and FT‐IR. Additional 1H NMR analysis was performed to characterize MCO structure. Two different behaviors were observed using the mixtures of crosslinkers. On one hand, MNA increases the rigidity with bio‐based content of 54.2%. On the other hand, the addition of MCO provides higher ductility with bio‐based content up to 98%. The same trend was observed by DMTA analysis. The novel cured resins were successfully crosslinked as demonstrated by the mechanical properties, FT‐IR analyses, and gel content. Based on the results, it is concluded that MCO presents higher reactivity than MNA, decreasing curing time with possible energy saving at industrial level. In general, the results showed that adding the appropriate amount of MCO, green thermosetting resins with the desired thermal and mechanical properties can be manufactured with high bio‐based content. [ABSTRACT FROM AUTHOR]

The improvement effect of epoxy resin on the mechanical properties of metakaolin geopolymer was investigated for the problem of strong brittleness of metakaolin geopolymer. According to the findings, the metakaolin geopolymer’s 7 d compressive strength, tensile strength, and flexural strength were all raised by 40%, 36%, and 28%, respectively, when epoxy resin concentration was 2% of the mass fraction of metakaolin. XRD, FTIR, MIP and SEM/EDS tests were performed on epoxy/metakaolin geopolymer. The results show that the epoxy resin can be uniformly dispersed in the metakaolin geopolymer to fill the pore space and optimize the pore structure. The hydrogen bonding between the epoxy resin and the metakaolin geopolymer enhances the obstruction and deflection ability of the epoxy resin to the matrix cracks. The above effects make the brittleness of metakaolin geopolymers improved. Epoxy resins can significantly improve the mechanical properties of metakaolin geopolymers, which can help broaden the application areas of metakaolin geopolymers. [ABSTRACT FROM AUTHOR]

Vulcanization is an important step in the manufacture of solid tires in which the crosslinking process occurs. In vulcanization, the materials commonly used as activators and coactivators are ZnO and stearic acid, respectively. In this research, ZnO and stearic acid were replaced with zinc stearate to improve the characteristics of vulcanized rubber. Zinc stearate was applied in four formulas with a composition of 5 to 9 phr. A formula that is often used in the rubber industry was used as a comparison, and ZnO and stearic acid of 5 phr and 2.5 phr, respectively, were applied. The rubber compound for solid tire production was developed using an open mill at a compounding temperature of 45 °C ± 5 °C. The vulcanization process of developing the rubber compound into vulcanized rubber was carried out at 150 °C for 20 min. Rubber compound test results showed that the use of zinc stearate at a ratio of 8 phr accelerated the curing time (t90) between 58.3% and 69%, the scorch time (ts2) between 22.4% and 95.5%, and the torque delta (Δs) between 17.67 and 24.21 kg-cm. In addition, the vulcanized rubber mechanical properties test results for the compression set parameter increased between 28.6% and 57.1%. Scan results with SEM–EDS showed that using ZS could improve the homogeneous distribution of the material in the vulcanized matrix of solid tire rubber. [ABSTRACT FROM AUTHOR]

Cemented paste backfill (CPB) that contains alkali-activated slag (AAS) produces more desirable properties and performance (enhanced fluidity, higher strength, lower cost, and limited carbon emission) as compared with CPB made with cement. Significant efforts have been devoted to the study of the effect of the individual factor on the rheology of AAS-CPB. However, the synergistic effect of curing temperature, time, and activator nature is still unclear. Therefore, the current research aims to investigate the time-dependent rheology of AAS-CPB under the combined influence of curing temperature, silica modulus (Ms), and activator concentration (AC). The findings revealed that a higher curing temperature results in a reduction in fluidity and an increase in the thixotropy of CPB. The evolution of rheological parameters of AAS-CPB is more insensitive to the curing temperature as compared to that of OPC-CPB. During the initial 2 h, higher AC can weaken the rheological parameter. However, a more rapid growth rate of rheological properties was observed after 2 h. The rheological parameters of AAS-CPB with higher Ms are always lower than those of AAS-CPB with lower Ms at all temperatures studied. In addition, the discrepancy in the linear correlation between thixotropy and plastic viscosity for OPC-CPBs and AAS-CPBs indicates the different hydration rates of slag and Portland cement. These findings are beneficial in guiding the mix proportion design of AAS-CPB in mines with various underground temperatures. [ABSTRACT FROM AUTHOR]

Nowadays, geotechnical specialists are focused on reinforcing soil engineering parameters using innovative and environmentally friendly methods. Microbial-Induced Calcite Precipitation is a ground improvement method for modifying soil strength, permeability, and stiffness; therefore, it can be vital to study the effective factors on the technique's efficiency and cost reduction. This study examined how biologically treated sands subjected to undrained triaxial loading responded to simultaneous changes in cementation solution molarity, optical density (OD600), and curing time. The triaxial experiments showed that the strength increased with the rise in the mentioned parameters. While the solution molarity and optical density had the highest and lowest effect on the soil improvement process, respectively, the optical density role was considerably low when the molarity was high. Increasing the molarity of the cementation solution resulted in a 45% increase in the peak stress ratio, while the optical density and curing time were constant. On the other hand, similar behaviour of dense sand and change in the response of cemented soil from strain-hardening to strain-softening were other notable observations of this study. In addition, the peak stress ratio at low strains increased with increasing the cementation level and then decreased to close to the amount of untreated sand with increasing strain. [ABSTRACT FROM AUTHOR]

Background. This study aimed to measure the shear bond strength and compressive strength of orthodontic adhesives at different curing times and intensities. Methods. Ninety extracted human premolars were used. Orthodontic brackets were bonded on the buccal surface of the teeth with orthodontic adhesive light-cured using VRN-VAFU LED curing light at different curing times (1, 3 and 5 seconds) and intensities (1000, 1600 and 2300 mW/cm2). A universal testing machine was used to measure the shear bond strength. The ratio of the adhesive remnant and compressive strength of the orthodontic adhesive, at each curing time at the different intensities, were also evaluated. The results were statistically analyzed using one-way analysis of variance followed by Tukey's test. Results. The lowest bond strength values (6.4, 9.9 and 12.6 MPa) were recorded with 1000 mW/cm2 intensity (at all curing times) in comparison with the other intensities (P < 0.05). Increasing the curing time significantly increased the bond strength of the orthodontic brackets (P < 0.05), except when the curing time was increased from 3 sec to 5 sec at 1600 mW/cm2 intensity. The highest compressive strength values (130.3, 147.1 and 174 MPa) were recorded at 2300 mW/cm2 intensity (at all curing times) compared to the other intensities (P < 0.05). The highest values of the ratio of the adhesive remnants were recorded at 1000 mW/cm2 intensity (at all curing times) compared to the other intensities (P < 0.05). Conclusion. Although, increasing the curing time and\or the curing intensity has a positive effect on the bond strength and compressive strength of the orthodontic adhesive, it might be possible to suggest reducing the curing time of orthodontic adhesive to 1 sec at curing intensity of 2300 mW/cm2. [ABSTRACT FROM AUTHOR]

Thin spray-on liners (TSL) is increasingly popular in underground mine support operations. In this study, a new type of TSL material is proposed, and its macro-micro physical and mechanical properties are characterized. A systematic investigation on the deformability behaviour of six rocks (i.e., coal rock, soft red sandstone, marble, hard sandstone, granite, and limestone) covered TSL materials with different curing ages (i.e., 0-day, 3-day, 7-day, 14-day, 21-day, and 28-day) under uniaxial compression circumstance is performed using acoustic emission (AE) and digital image correlation (DIC) methods. The results show that TSL improves the peak strain of each rock sample, except hard sandstone. The impact of TSL on the peak compressive strength of coal rock, soft red sandstone, and marble is nearly negligible, while it diminishes the strength of hard sandstone, granite, and limestone. As the TSL ages, the peak strength and elastic modulus of limestone initially increase and then decrease, reaching the minimum at 14-day of age, with values 89.81 MPa and 23.13 GPa respectively. However, for other rock samples, the effect of TSL age is not significant. The AE signal produced inside the rock diminishes during the elastic-plastic stage, while the ratio of shear cracks increases upon failure of each rock specimen. The macroscopic failure modes of coal rock and limestone exhibit prominent axial splitting characteristics, whereas marble and hard sandstone undergo mixed failure processes involving shear, tension, and shear-tension. The test data highly correspond to the macroscopic fracture characteristics. The research findings can serve as guidance for TSL support in both soft and hard rock scenarios. • A new type of Thin spray-on liners (TSL) material is proposed. • Basic macro and micro properties of TSLs are characterized using XRD and SEM. • Failure behaviour of six rocks covered TSL materials with different curing ages is investigated using AE and DIC methods. [ABSTRACT FROM AUTHOR]

The adhesion bonding strength between bridge deck and asphalt pavement is tested with three waterproof materials, namely SBS modified emulsified asphalt, SBR modified emulsified asphalt and waterborne epoxy emulsified asphalt. The influence of curing temperature, besmear brush times, asphalt curing time, binder type and curing time on test results was analyzed. The test results show that: to improve test efficiency, adhesion bonding strength specimen forming method can be taken to brush 1 time: SBS and SBR modified emulsified asphalt were cured at room temperature for 3 d, waterborne epoxy asphalt was cured for 7 d: the pullout block was bonded with α-cyanoacrylate glue and cured at room temperature for 2 h. Compared with the standard test method GB/T 16777-2008 "Test methods for building waterproofing coatings", the test results are credible. [ABSTRACT FROM AUTHOR]

Concern regarding global climate change and its detrimental effects on society demands the building sector, one of the major contributors to global warming. Reducing cement usage is a significant challenge for the concrete industry; achieving this objective can help reduce global carbon dioxide emissions. Replacing the cement in concrete with by-product ashes is a promising approach for reducing the embodied carbon in concrete and improving some of its properties. Among different by-product ashes, ground granulated blast furnace slag (GGBFS) is a viable option to produce sustainable self-compacting concrete (SCC). Compressive strength (CS), on the other hand, is an essential characteristic among other evaluated properties. As a result, establishing trustworthy models to forecast the CS of SCC is critical to saving cost, time, and energy. Furthermore, it provides helpful instruction for planning building projects and determining the best time to remove the formwork. In this study, four alternative models were suggested to predict the CS of SCC mixes produced by GGBFS: the artificial neural network (ANN), nonlinear model (NLR), linear relationship model (LR), and multi-logistic model (MLR). To do so, an extensive set of data consisting of about 200 mixtures were extracted and analyzed to develop the models, and various mixture proportions and curing times were considered input variables. To test the effectiveness of the suggested models, several statistical evaluations including determination coefficient (R2), mean absolute error (MAE), scatter index (SI), root mean squared error (RMSE), and objective (OBJ) value were utilized. In comparison to other models, the ANN model performed better to forecast the CS of SCC mixes incorporating GGBFS. The RMSE, MAE, OBJ, and R2 values for this model were 4.73 MPa, 2.3 MPa, 3.4 MPa, and 0.955, respectively. [ABSTRACT FROM AUTHOR]

The existence of silty sand in the infrastructure under concrete constructions, hydraulic structures, and irrigation systems has always caused challenges. Improving this kind of soil is always a challenging approach to increase compressive strength and shear stress. There is a conception that adding some extra material such as concrete can increase the stability of this soil against contributed forces. The present study investigated the effects of curing time (3, 7, 14, 21, and 28 days) and different percentages of various additives (3%, 5%, and 7%) on the strength of the silty sand soils. A series of laboratory tests were carried out to measure the Uniaxial Compressive Strength (UCS) and California Bearing Ratio (CBR) by evaluating the effect of additives on the strength parameters of silty sand soil. In total, 299 experimental tests have been conducted in the soil mechanics laboratory of SRBIAU. Results indicated that adding additives such as concrete to silty sand soil improved significantly the compressive strength and shear strength. The comparisons among the experimental test illustrate that due to increasing the curing time, the aforementioned parameters were increased significantly; however, Confix and Bentonite aggregates did not have a marginal effect on the compressive strength and shear strength. Also, after the 21st day of the curing time, the rate of increment of the UCS and CBR reached slightly and then attained a constant value. Also, after this duration, the curing time is an independent factor in the variation of the UCS and CBR tests. Furthermore, the addition of 5% Pozzolana cement and 7% Portland cement with 28 days of curing had the highest CBR number and UCS resistance of 176.26 and 17.58 kg/cm2, respectively. Also, the sketch of the different failure patterns was shown during the curing time. Finally, by increasing the curing time, the behavior of specimens from semi-brittle to brittle made them harder. [ABSTRACT FROM AUTHOR]

n unsaturated polyester resin is one of the principal matrices used in fibres reinforced plastics (FRP) products. Being a pre-polymer the cure kinetics plays an important role in making successful FRPproducts. Hence, this study deals with the cure kinetics of unsaturated polyester resin. It includes the optimization of gel time, curing time and temperature of it. The gel time, which indicates the formation of cross-linking structure, was studied by varying the weight percentage of the Methyl Ethyl Ketone Peroxide (MEKP) catalyst and Cobalt Octane accelerator. The optimum gel time of 15-16 minutes was found at the 1:1 wt% level of MEKP and Cobalt Octane concentration. A differential scanning calorimetry was used to obtain conversion profiles of the resin at different temperature ranges from 25--45°C. From the DSC study, the suitable curing temperature ofunsaturatedpolyester resin was identified as 45°C. Fourier transform infrared spectroscopy was used to study the effect of time on the curing of unsaturated polyester resin. From FTIR analysis, the major conversion ofresin was found at 35 minutes. [ABSTRACT FROM AUTHOR]

Currently, a soil stabilization approach using fly ash as an effective choice for increasing soil stiffness and strength has emerged. With the presence of water, the lime in the fly ash would be separated, generating cementitious materials binding the grains of sand. In the present study, the influence of curing time and saturation during specimen preparation on the behavior of fly ash-modified sand was observed by performing a series of splitting tensile strength tests. It was found that the splitting tensile strength increases with fly ash content and curing time and decreases with saturation. The splitting tensile strength produced at 30% saturation was approximately two-fold higher than 100%, particularly at one month of curing time. However, the splitting tensile strength at higher saturations approaches lower, especially at longer curing times. Porewater evaporation accelerates the self-hardening occurring over time during curing. By increasing the fly ash percentage from 5% to 20% in the mixture, the splitting tensile strength increased by up to twenty-fold in the present study. An equation has been proposed as a function of porosity/volumetric fly ash content, curing time, and saturation during the preparation of the specimen. [ABSTRACT FROM AUTHOR]

The effects of carbon dioxide (CO2) curing conditions (temperature, relative humidity and CO2 curing time) on the physical properties of recycled coarse aggregate (RCA) with varying attached mortar (AM) contents were studied. Before and after CO2 curing, the physical properties in terms of the apparent density, water absorption and crushing value of RCA were tested and the quality of RCA was determined. Besides, scanning electron microscope was used to observe the microstructure of RCA. Results show that the physical properties variation of RCA with higher AM content are more significant, and the quality of RCA with lower AM content is easier to be upgraded during CO2 curing. The physical properties of RCA with 40.8% AM content are earlier stable than that with no less than 44.5% AM content during CO2 curing. The optimal temperature and relative humidity are 50 °C and 55% for CO2 curing, respectively. CO2 curing is incapable of upgrading the quality of RCA with AM no less than 50.6%. The quality of RCA with 44.5% AM content can be upgraded only under the optimum CO2 curing conditions. Under relative humidity higher than 40% and the CO2 curing time more than 12 h, CO2 curing upgrades the quality of RCA with 40.8% AM content. [ABSTRACT FROM AUTHOR]

Concrete has relatively high compressive strength (resists breaking when squeezed) but significantly lower tensile strength (vulnerable to breaking when pulled apart). The compressive strength is typically controlled by the ratio of water-to-cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words, we can say concrete is made up of sand (which is a fine aggregate), ballast (which is a coarse aggregate), cement (which can be referred to as a binder), and water (which is an additive). Highly ductile material engineered cementitious composites (ECC) were developed to address these issues by spreading short polymer fibers randomly throughout a cement-based matrix. It has a high tensile strain capacity of more than 3%, hundreds of times more than conventional concrete. On the other hand, among the other examined qualities, compressive strength (CS) is a critical property. Consequently, developing reliable models to predict an ECC's compressive strength is crucial for cost, time, and energy savings. It also includes instructions for planning construction projects and calculating the optimal time to remove the formwork. The artificial neural network (ANN), nonlinear model (NLR), linear relationship model (LR), multi-logistic model (MLR), and M5P-tree model were all proposed as alternative models to estimate the CS of ECC mixtures created by fly ash in this research (M5P). To create the models, a large amount of data were gathered and evaluated, totaling roughly 205 mixes. Various mixture proportions, fiber length, diameter, and curing durations were explored as input variables. To test the effectiveness of the suggested models, several statistical evaluations, including determination coefficient (R2), Mean Absolute Error (MAE), Scatter Index (SI), Root Mean Squared Error (RMSE), and Objective (OBJ) value, were utilized. Based on the statistical evaluations, the ANN model performed better in forecasting the CS of ECC mixes incorporating fly ash than other models. This model's RMSE, MAE, OBJ, and R2 values were 4.55 MPa, 3.46 MPa, 4.39 MPa, and 0.98, respectively. A large database presented in this investigation can be used as the bench mark for future mixture proportions of the ECC. Moreover, the sensitivity analysis showed the contribution of each mixture ingredient on the CS of ECC. [ABSTRACT FROM AUTHOR]

High price of land and importance of modern construction has imposed the need to strengthen weak clay soils. The stabilization of these soils has been conducted using various additives. Due to its low cost, availability, and positive impact on resistance, lime has traditionally been applied for stabilisation of poor and sensitive types of soils. In this research, lime powder, added in the percentages of 0, 2, 4, 8 and 16 of the dry soil weight, was mixed with kaolinite clay soil and its various engineering parameters were investigated during the curing time of 90 days. PH change, Atterberg Limits, optimum water content, and the modified clay maximum dry unit weight, were determined at different percentages of lime during the curing time. In the scope of determination of an optimum lime powder content, the Unconfined Compressive Strength tests (UCS) and CBR tests were conducted. The Young’s modulus was determined based on UCS testing and definition of stress-strain curve. The results showed a significant increase in the effective, responsive performance of lime in the soil and a remarkable increase in the maximum compressive strength (qu), cohesion, and Young’s modulus.

In laboratory conditions, neglecting time and temperature as two effective parameters on the mechanical properties of asphalt mixtures may affect the results of experimental tests and mislead researchers in analyzing the results. Therefore, it seems necessary that some of the less considered laboratory conditions in past studies need to be perceived more to minimize the error of results obtained by laboratory tests. Hence, in this study, after examining the research on warm mix asphalt and factors affecting laboratory test results, three parameters of short-term aging (asphalt binder storage in oven), curing time (from construction to placement in the test chamber), and thermal equilibrium time (from placement in the test chamber to test onset) were selected to combine different levels for evaluating their effect on the rutting potential by performing dynamic creep test. Based on the results, by increasing the time of aging, the viscosity of asphalt binder increased, thus increasing the mixture’s stiffness and reducing the slippage of materials over each other and decreasing the final strain. Also, increasing the curing time improved the adhesion between the asphalt binder and aggregate and reduced the rutting potential of the sample. However, by increasing the thermal equilibrium time, the viscosity and power of the asphalt binder’s cohesion were reduced, thus loosening the asphalt binder and aggregates, creating shear strain, and increasing the rutting potential of the warm mix asphalt (WMA). Based on the results of statistical analyses, the parameters considered in laboratory conditions affected the rutting potential of WMAs at a 95% confidence level. [ABSTRACT FROM AUTHOR]

In this paper, variable temperature (VT) curing was used on ultra-high-performance concrete (UHPC) specimens to determine the effects of early-age temperature histories on UHPC mechanical property development. A systematic test plan evaluated 16 programmed VT profiles with different target temperatures as well as VT start and end times. VT curing profiles were intentionally exaggerated from typical time-temperature curves of hydrating concrete to expose the effects of timing on mechanical property development. Specimens that were placed into VT curing immediately after molding produced higher maximum temperatures compared with specimens that were exposed to VT curing 1 day after molding. However, specimens that were cured at room temperature for 1 day prior to VT curing had significantly higher compressive strength and elastic modulus. These findings show the importance of predicting in-place temperatures that develop in UHPC structures as mechanical properties can be drastically altered based on when high temperatures occur. [ABSTRACT FROM AUTHOR]

To achieve the efficient, rapid construction of prestressed anchor cables, in this study, through an indoor pull-out test and field basic test, we investigated the mechanical behavior, expansion, drawing performance and bond properties of a new type of high-strength, fast anchorage agent. We analyzed the influence of the water material ratio and curing time on its performance and determined the corresponding construction. It was found that the new anchoring agent could be effectively applied in field construction and achieved a compressive strength of 30 MPa within 30 h. Moreover, during the solidification process, the hydration reaction node could be reached within 5–6 h when the material expansion was and the feedback to the water–material ratio were the strongest. In addition, in the drawing process, the anchorage agent exhibited a strong bond with the reinforcement and the rock layer, and the bonding of the anchorage agent to the rock layer was greater than that of the steel bar. Therefore, in order to provide anchorage, it is necessary to increase the contact area between the steel strand and the anchorage agent. [ABSTRACT FROM AUTHOR]

This study has attempted to enhance and characterise the shear strength of sandy clay soil mixed with 50% gypsum through an integrated treatment combining petrochemical and freezing techniques. The soil specimens used in this paper have been taken from a 0.5-1.0 m depth. The disturbed soil samples have been packed in bags weighing 60-70 kg and then transported to the lab. First, the petrochemical technique has been applied separately using polypropylene with various weight percentages (dry weight) of the gypseous soil and different aspect ratios of liquid polymer to represent composite materials in two phases (drying and immersion) for a specified period. Then, the freezing approach has been implemented at -3 °C, -7 °C and -10 °C. Finally, the proposed integrated method has been performed based on a combination of the petrochemical approach and freezing for all three methods. The shear stress of unsaturated soil has been measured using direct shear tests and compared with the treated samples. The integrated approach had the best results, in particular the 15% polymer under freezing at -7 °C for gypseous soil. These results indicate that this composite material is useful for the improvement of shear behaviours due to its curing time and petrochemical content. [ABSTRACT FROM AUTHOR]

Rapid urbanization and industrialization with corresponding economic growth have increased concrete production, leading to resource depletion and environmental pollution. The mentioned problems can be resolved by using recycled aggregates and industrial waste ashes as natural aggregate and cement replacement in concrete production. Incorporating different by-product ashes and recycled plastic (RP) aggregates are viable options to produce sustainable self-compacting concrete (SCC). On the other hand, compressive strength is an essential characteristic among other evaluated properties. As a result, establishing trustworthy models to forecast the compressive strength of SCC is critical to saving cost, time, and energy. Furthermore, it provides valuable instruction for planning building projects and determining the best time to remove the formwork. In this study, four alternative models were suggested to predict the compressive strength of SCC mixes produced by RP aggregates: the artificial neural network (ANN), nonlinear model, linear relationship model, and multi-logistic model. To do so, an extensive set of data consisting of 400 mixtures were extracted and analyzed to develop the models, various mixture proportions and curing times were considered as input variables. To test the effectiveness of the suggested models, several statistical evaluations, including coefficient of determination (R2), scatter index, root mean squared error (RMSE), mean absolute error (MAE), and Objective (OBJ) value were utilized. Compared to other models, the ANN model performed better to forecast the compressive strength of SCC mixes incorporating RP aggregates. The RMSE, MAE, OBJ, and R2 values for this model were 5.46 MPa, 2.31 MPa, 4.26 MPa, and 0.973, respectively. [ABSTRACT FROM AUTHOR]

This study was made in order to develop a statistical model for predicting the unconfined compressive strength (UCS) of lime-stabilized clayey soils. The obtained results showed that the developed model (UCS-Model) is very efficient and can be used as a reliable tool for predicting the UCS of lime-stabilized clayey soils. Indeed, both the (F-test) and (t-test) showed that the significance value of UCS-Model was found to be less than 0.05 which indicates that the lime content and curing time significantly contribute to the constructed model and lead to a better prediction of UCS. In addition, the comparison study between predicted values and experimental data indicated that the UCS model can be reasonably applied to explain the effect of lime content below 10%, and curing time between 0 and 90 days on UCS of clayey soils and to design new mixtures without making an experimental study. [ABSTRACT FROM AUTHOR]

Rubber is one of the most used materials in the world; however, raw rubber shows a relatively very low mechanical strength. Therefore, it needs to be cured before its ultimate applicatios. Curing process specifications, such as the curing time and temperature, influence the material properties of the final cured product. The transient radar method (TRM) is introduced as an alternative for vulcanization monitoring in this study. Three polyurethane-rubber samples with different curing times of 2, 4, and 5.5 min were studied by TRM to investigate the feasibility and robustness of the TRM in curing time monitoring. Additionally, the mechanical stiffness of the samples was investigated by using a unidirectional tensile test to investigate the potential correlations between curing time, dielectric permittivity, and stiffness. According to the results, the complex permittivity and stiffness of the samples with 2, 4, and 5.5 min of curing time was 17.33 ± 0.07 − (2.41 ± 0.04)j; 17.09 ± 0.05 − (4.90 ± 0.03)j; 23.60 ± 0.05 − (14.06 ± 0.06)j; and 0.29, 0.35, and 0.38 kPa, respectively. Further statistical analyses showed a correlation coefficient of 0.99 (p = 0.06), 0.80 (p = 0.40), and 0.92 (p = 0.25) between curing time–stiffness, curing time–permittivity (real part), and curing time–permittivity (imaginary part), respectively. The correlation coefficient between curing time and permittivity can show the potential of the TRM system in contact-free vulcanization monitoring, as the impact of vulcanization can be tracked by means of TRM. [ABSTRACT FROM AUTHOR]

Chalk breaks easily when subjected to human action such as mechanical handling, earthworks operations or pile installation. These actions break the cemented structure of chalk, which turns into a degraded material known as putty, with lower strength and stiffness than the intact chalk. The addition of Portland cement can improve the behaviour of chalk putties. Yet, there are no studies determining the tensile strength of chalk putty–cement blends, the initial stiffness evolution during the curing time and other design parameters such as friction angle and cohesion of this material. This paper addresses this knowledge gap and provides an interpretation of new experimental results based on the dimensionless index expressed as the ratio between porosity and volumetric content of cement (η/Civ) or its exponential modification (η/Civa). This index aids the selection of the amount of cement and density for key design parameters of compacted chalk putty–cement blends required in geotechnical engineering projects such as road foundations and pavements, embankments, and also bored concrete pile foundations. [ABSTRACT FROM AUTHOR]

The influence of microstructure of silica-enhanced cement on the mechanical performance of cement is difficult to describe. In this study, we used the scanning electron microscope and image processing method to investigate the relationship between the complicity of cement microstructure and compressive strength under various temperatures and curing times. Fractal dimension was applied to describe the complicity of silica-enhanced cement. The relationships among compressive strength, fractal dimension, temperature, curing time and pore structure of cement were identified. The results show that curing time directly controls the complicity of microstructure of silica-enhanced cement and compressive strength by altering the pore orientation and macropore ratio in silica-enhanced cement. The curing temperature affects the complicity of cement microstructure and compressive strength indirectly by changing the ratio of micropore and small pore. The fractal dimension of silica-enhanced cement shows good correlation with compressive strength. Pore size distribution is the most important factor that influences the complicity of cement matrix and compressive strength of silica-enhanced cement. When building up the macroscopic mechanical performance model of silica-enhanced cement, we should consider the influence of pore size distribution in cement under different curing temperatures and times on the complicity of cement microstructure.

The research presents the strength characteristics and theoretical mix design of full-depth reclamation (FDR) with cement for road maintenance and rehabilitation. The reclaimed aggregates used in the study were pulverized and blended on the investigation site by the recycler machine. The FDR mix design covered the reclaimed asphalt pavement (RAP), reclaimed base, and reclaimed subbase courses. The unconfined compressive strength (UCS) was tested on the FDR with cement under different mix proportions, cement content, moisture content, and curing time. Two factors that affect the UCS of FDR, viz., moisture-induced packing density and moisture for cement hydration, were observed. The mix proportion with 40 % RAP required at least 6 % cement to stabilize the FDR for use as a bound base course as per the standard, while the effective limit of cement content for FDR was 9 %. The strength prediction model of FDR with cement was presented theoretically based on the modified soil-moisture/cement ratio concept. The verification of the proposed strength model was performed using 7 and 28-day UCS from another investigation site. The design recommendations for FDR with cement were summarized. This discovery could offer a cost-effective and precise method for the mix design of FDR with cement. • Reclaimed materials in FDR were blended and stabilized with cement. • Strength of FDR with cement can be normalized by a modified soil-moisture/cement ratio. • Strength prediction model was adopted for FDR with cement. • Case study for verification of the strength prediction model was conducted. • Step-by-step mix design of FDR with cement was summarized. [ABSTRACT FROM AUTHOR]

Success of long orthodontic treatment using orthodontic brackets depends mainly on the efficiency of the adhesive system used and it's degree of resistance in the face of stresses and foresees applied during treatment. The aim of this study was to evaluate the shear bond strength of orthodontic brackets bonded with three adhesive systems using different light curing times. The 126 human extracted premolars were randomly divided into three equal groups (n = 42) depending on the type of adhesive system used; total-etch (Transbond XT), self-etch (Transbond Plus), and self-adhesive (GC-Ortho Connect) system. Then each group was randomly subdivided into three subgroups (n = 14) based on the curing time; 1-s, 3-s, and 20-s. The shear bond strength (SBS) and adhesive remnant index (ARI) were evaluated in each subgroup using universal testing machine and stereomicroscope respectively. The data were analyzed statistically by a two-way ANOVA for SBS, and Scheirer Ray Hare Test for ARI. The significance level was set at P ≤ 0.05. The results showed a statistically significant difference in shear bond strength at the three-time points for each adhesive system (p < 0.001) with the highest SBS value in 20-sec groups followed by 3-sec groups while 1-sec groups was the lowest. However, there was no statistically significant difference in Shear bond strength between the three adhesive systems except 20-sec groups (p < 0.001). ARI showed a statistically significant difference between all adhesive systems with the highest scores in TE groups, while the lowest in SE groups. All adhesive systems provided acceptable values of SBS at all curing times except the 1-sec group in SE and SA adhesive systems where the SBS values were the lowest and below the acceptable range. [ABSTRACT FROM AUTHOR]

Unconfined compression tests are usually used to assess strength in improved soils. However, split tensile strength is the most significant increase. Split tensile strength tests are important in rural, urban, and aviation pavement mechanics studies. Tensile stresses are produced by traffic movement, soil contraction, seasonal temperature variations, and, in some situations, by directly applying distributed loads on the soil. This study aims to analyze the influence of lime addition on the split tensile strength of clayey sedimentary soil at different curing times. Control parameters such as moisture, matric suction, lime content, porosity, volumetric lime content, and curing periods were evaluated. The sample results show that the split tensile strength increased as the lime content increased, and soil porosity decreased. Finally, the porosity/volumetric lime content ratio was chosen as a unique parameter to access split tensile strength. [ABSTRACT FROM AUTHOR]

In this study, the effect of magnesia (MgO) on the stabilization of a clay soil contaminated with glycerol was investigated through a series of experiments. The tests were performed in two groups. In the first group, the natural soil was mixed with 5, 8, and 12% MgO. A set of tests, including unconfined compressive strength (UCS) tests, were conducted on samples prepared at curing times of 7, 14, and 28 days. In addition, a number of samples prepared with different percentages of MgO were subjected to CO2 under a pressure of 0.5 bar for periods of 4, 8, and 24 hours. In the second group, the soil was contaminated with 4, 8, and 12% glycerol and was then mixed with 5, 8, and 12% MgO. A group of tests, similar to the first group, were conducted on the contaminated samples. The results showed that adding MgO to the natural soil and the contaminated soil increases the strength of the soil, and the amount of increase in strength depends on the percentage of MgO and the curing time. During stabilization, the contaminated soil with 8 and 12% glycerol gained more strength than the natural soil. The results also indicated that forced carbonation can facilitate the stabilization of MgO-stabilized natural and contaminated soils in a few hours compared with conventional methods that take several days. Scanning electron microscopy (SEM) results showed that the gained strength for both groups resulted from the interaction between the soil and MgO. [ABSTRACT FROM AUTHOR]

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This work presents the manufacture of polymer composites using 3D woven structures (orthogonal, angle interlock and warp interlock) with glass multifilament tows and epoxy as the resin. The mechanical properties were analyzed by varying the processing parameters, namely, add-on percentage, amount of hardener, curing time, curing temperature and molding pressure, at four different levels during the composite fabrication for three different 3D woven structures. The mechanical properties of composites are affected by resin infusion or resin impregnation. Resin infusion depends on many processing conditions (temperature, pressure, viscosity and molding time), the structure of the reinforcement and the compatibility of the resin with the reinforcement. The samples were tested for tensile strength, tensile modulus, impact resistance and flexural strength. Optimal process parameters were identified for different 3D-woven-structure-based composites for obtaining optimal results for tensile strength, tensile modulus, impact resistance and flexural strength. The tensile strength, elongation at break and tensile modulus were found to be at a maximum for the angle interlock structure among the various 3D woven composites. A composition of 55% matrix (including 12% of hardener added) and 45% fiber were found to be optimal for the tensile and impact performance of 3D woven glass–epoxy composites. A curing temperature of about 140 °C seemed to be optimal for glass–epoxy composites. Increasing the molding pressure up to 12 bar helped with better penetration of the resin, resulting in higher tensile strength, modulus and impact performance. The optimal conditions for the best flexural performance in 3D woven glass–epoxy composites were 12% hardener, 140 °C curing temperature, 900 s curing time and 12 bar molding pressure. [ABSTRACT FROM AUTHOR]

Stability of sandy silt soils is important to increase the resistance of the foundations of the buildings and hydraulic structures in civil engineering projects. It seems that adding some materials with different percentages of addition can raise the values of the compressive strength. Present study carried out a series of experimental tests by using the unconfined compressive strength (UCS) and California bearing ratio (CBR) in low plasticity sandy silt soils due to different additive materials such as cement, pozzolan cement, Confix Pr50, cement + one percent of the polypropylene fibers, Confix Pr50+25 percent of bentonite, Emaco S45, Galena, Galena+1 percent of lime, Galena+3 percent of lime. In total, 299 experiments have been performed in the soil mechanics laboratory of Science and Research Branch, Islamic Azad University (SRBIAU (. In order to investigate the effects of different additive percentages on compressive strength and strain variation, three values of additive materials were considered as 3, 5 and 7 percent. Furthermore, the UCS values and CBR numbers were measured during the time steps as 3, 7, 14, 21 and 28 days from the start point of the tests. Also, the values of the specific weight, porosity, humidity percent and unconfined compressive strength were measured over the considered time steps. In order to measure the mentioned values, the scaled volumes of experimental soils were dried in the oven and the values of specific weight, and humidity percent were calculated. Furthermore, the values of the unconfined compressive strength were measured by the related apparatus. The results indicate that the mixed soils with cement enhance the higher value of unconfined compressive strength and California bearing ratio such as solo cement, pozzolan cement and cement with one percent of the polypropylene; however, adding the Confix Pr50+25 percent of bentonite decreases the values of CBR marginally. Experimental sample soils with 3, 5 and 7 percent of the confix attained less values of UCS and CBR which can be deduced that confix material is not appropriate to raise the stability of the foundations in sandy silt soils. Finally, by employing the soil properties over the time, an equation has been proposed to estimate the unconfined compressive strength by using the non-regression technique. The accuracy of the proposed equation was calculated and the results indicated that the predicted values had a good agreement with observed data. [ABSTRACT FROM AUTHOR]

This study aims at investigating the lime treatment effect on the changes in microstructure and water retention property of compacted saline soil, with consideration of the aggregate size effect. Two soil powders with different maximum aggregate sizes (Dmax = 0.4 and 5 mm) were prepared and stabilized by 2% lime. The microstructure, total suction and matric suction were determined at various curing times. Results showed that the lime treatment caused a rapid decrease in micro-pores and an increase in macro-pores due to the flocculation of soil particles. During curing, the percentage of micro-pores decreased and that of nano-pores increased slightly. Due to the modification of microstructure, the matric suction increased significantly at 90-day curing. However, the curing time effect on the total suction was insignificant. This was due to the fact that the Ca2+ and Mg2+ in soil pore water and the Ca2+ from hydrated lime were consumed in the precipitations of CaCO3 and Mg(OH)2, cation exchanges and pozzolanic reaction, resulting in a reduction in osmotic suction. Therefore, the increase in total suction was slight, as the increase in matric suction was balanced by the decrease in osmotic suction. The treated specimens with larger aggregates exhibited a larger modal size and thus had a smaller air entry value. The aggregate size effect on the water retention property of total suction and matric suction was found to be insignificant, which could be explained by the similar pore size distribution at micro-pore range and the same soil mineralogy for specimens with different aggregates. [ABSTRACT FROM AUTHOR]

The non-isothermal reaction kinetics of cyanate ester system was investigated by dynamic differential scanning calorimetry (DSC). The analysis of non-isothermal data was carried out by using the model-fitting Kissinger, Flynn-Wall-Ozawa, and Crane methods. The results indicate that the apparent activation energy of the curing reaction is 101.3 kJ·mol-1 and 99.4 kJ·mol-1calculated from Kissinger and Flynn-Wall-Ozawa models, respectively. The reaction sequence of the adhesive is 0.92 calculated from Crane model. In addition, the relationship of the curing degree with the curing temperature and the curing time is established. The curing parameters are obtained by adopting "T-β" and "t-β" extrapolation, and the strength test proves the validity of the curing parameters designed in this paper. These results constitute a theoretical basis for the curing and application of the cyanate ester adhesives.