Reduction In Dynamic Modulus Research Articles

Thermal and mechanical variations of cementitious composites with phase change materials using a contactless ultrasonic method

Recently, research on reducing building energy by applying phase change materials (PCMs), such as n-octadecane, to cementitious materials, is being actively conducted. PCMs were modified as a type of lightweight aggregate (LWA) to prevent leakage in concrete. In this study, a fully contactless ultrasonic system was applied to monitor thermal and mechanical variations of concrete plates including PCM-LWAs subjected to temperatures up to 48 °C. Because surface preparation and direct coupling processes were not required, this method collected reliable information without thermal interference. The measurements were conducted during the melting and free cooling process of PCM-LWAs, where the methods monitored the variation of leaky Rayleigh waves for dynamic modulus changes of the solid material. The experimental results illustrated that the contactless ultrasonic system enabled a 5.5 % reduction in dynamic modulus for a concrete plate mixed with 160 kg/m3 PCM-LWAs, and showed the time lag effect of heat transfer and surface temperature reduction through heat storage performance. Further comparison studies of the dynamic modulus variation among different mix proportions of PCM-LWA concrete plates were conducted using temperature cycles. Based on the experimental study, the unique thermal and mechanical behaviors of PCM-LWA mixed concrete plates were discussed.

Feasibility and Sustainable Performance of RAP Mixtures with Low-Viscosity Binder and Castor Wax–Corn Oil Rejuvenators

The utilization of Recycled Asphalt Pavement (RAP) mixtures in pavement construction is an environmentally friendly approach that promotes sustainable development by reducing energy consumption and material waste. However, the high cost of conventional rejuvenators limits the widespread use of RAP mixtures. In this study, a novel approach is proposed to enhance the performance of RAP mixtures by incorporating a combination of high-penetration asphalt binder and rejuvenators, namely Castor wax and Corn oil. The newly developed rejuvenator consists of 8.5% Castor wax oil, 3% Corn oil, 3% fatty acid amine surfactant, 0.2% additive, and 79.8% water. The test results demonstrate that the modified mixture exhibits superior properties compared with conventional RAP mixtures. The Multiple Stress Creep Recovery test results showed a 20% reduction in cumulative strain rate for the RAP mixture with the new rejuvenators compared with that for the conventional ones. Furthermore, the Tensile Strength Ratio test indicated a notable 9.47% improvement in the rejuvenated RAP mixture’s resistance to moisture-induced damage compared with the conventional mixture. Evaluation of viscoelastic behaviors revealed a slight reduction in dynamic modulus for the rejuvenated binder, but a significant improvement in elastic behavior. In terms of rutting resistance, the Hamburg wheel tracking rut depths of the rejuvenated binder were significantly lower, representing reductions of 21.83% for specific binder compositions. Additionally, the absence of the stripping phenomenon further confirmed the superior moisture resistance of the modified mixture. The rejuvenated binder exhibited a remarkable 28.55% increase in fatigue load cycles to failure compared with the reference RAP binder, demonstrating substantial resistance to fatigue cracking. These quantitative comparisons not only confirm the superior performance of the modified mixture over conventional RAP mixtures, but also highlight the potential cost savings achieved through the utilization of Castor wax and Corn oil rejuvenators.

Initial freeze–thaw damage detection in concrete using two-dimensional non-contact ultrasonic sensors

Freezing and thawing cause concrete deterioration such as micro-cracking and surface scaling. An effective method for initial damage detection in concrete is required to prevent further deterioration of structures. In this study, initial freeze–thaw damage (small-size damage) was detected on a concrete surface using developed two-dimensional non-contact ultrasonic sensors based on a micro-electromechanical system (MEMS). The wavefield of ultrasonic waves passed through damaged concrete surfaces contain propagating and scattered waves, caused by refraction and reflection. To measure the wavefield, multi-channel non-contact ultrasonic sensors was developed including 128 MEMS array. Then, the amplitude of scattered waves was extracted in the frequency-wavenumber domain. The proposed method was experimentally validated through freeze–thaw cycle testing and compared to the conventional dynamic modulus reduction. The results demonstrated that the proposed method was at least 15 times more sensitive than the conventional method toward initial freeze–thaw damage on concrete surfaces.

Behavior of the Dynamic Modulus and Fatigue in Asphalt Mixtures with Blast Oxygen Furnace Slag and Blast Furnace Dust

Slag from a Blast Oxygen Furnace (BOF) is produced during the transformation of cast iron, coming from the blast furnace, into steel during the integrated steelmaking process, just as blast furnace dust (BFD) is produced during the transformation of the iron mineral into cast iron. These residues have generated environmental problems due to the accumulation and inadequate disposal thereof. Consequently, this study aims to analyze the use and behavior of the dynamic modulus and the fatigue in asphalt mixtures with partial (50 %) and total (100 %) substitution of the coarse aggregate for BOF slag and the fine aggregate for BFD. The results are compared with the behavior of a mixture elaborated with conventional aggregates. To achieve this objective, the chemical and physical properties of BOF and BFD were determined along with the optimum asphalt cement content, determined using the Ramcodes methodology. Tests were carried out to evaluate the physical characteristics, the dynamic modulus, and the fatigue of each type of mixture. The results of this study demonstrate adequate fatigue behavior and a slight reduction in dynamic modulus in mixtures with BOF and BFD. This allows us to deduce that the use of these residues is feasible and thereby to contribute to sustainable development and the protection of the environment.

Durability properties of non-air entrained roller compacted concrete pavement containing coal waste ash in presence of de-icing salts

The aim of this study was to evaluate the durability properties of non-air entrained roller compacted concrete pavement (RCCP) containing coal waste ash (CWA) as partial replacement of cement in presence of de-icing salts. Four different mix combinations were used to prepare RCCP specimens. In control mix with no CWA, the cement content was fixed to 14% by mass of dry aggregates. In other mixes, cement was replaced with 2, 3 and 4% CWA (by mass of dry aggregates) named as C2, C3 and C4, respectively. Durability characteristics such as permeable void content, chloride ion penetration, de-icing salt surface scaling resistance and freeze-thaw resistance exposed to salt solution were evaluated. According to results, all studied RCCPs showed acceptable chloride ion penetration. By increasing CWA content up to 3%, surface scaling exposed to salt solution delayed approximately 5cycles. In presence of salt solution, up to 180freeze-thawcycles, ultrasonic pulse velocity in control mix was slightly more than C2 and C3 mixes while at higher cycles than 180 the reverse was true. C4 mix revealed excellent resistance during initial 180freeze-thawcycles while its resistance drastically reduced in continue and showed critical behavior up to 300cycles. Relative dynamic modulus of elasticity during 300freeze-thawcycles was almost the same for the control, C2 and C3 mixes. Conversely, C4 mix experienced more than 40% dynamic modulus reduction at the end of freeze-thaw test. The durability factor at the end of freeze-thaw test was satisfactory for the control, C2 and C3 mixes. Based on the results of durability tests, the optimum CWA content was determined as equal to 3%.

Evaluation of Moisture Susceptibility of High-Porosity ATPB Drainage Layer Materials Using Modified Dynamic Modulus Test

AbstractAsphalt-treated permeable base (ATPB) mixtures have been widely applied for drainage layers in pavements to avoid moisture-induced problems in the United States. However, with frequent exposure to water, the ATPB drainage layer itself is at high risk of moisture damage. In this study, the dynamic modulus and phase angle are used as the indicators to evaluate the potential moisture-induced deterioration of typical ATPB materials adopted in Virginia and Oklahoma. The modified dynamic modulus test appropriate for testing drainage layer materials with moisture deterioration were determined and adopted. Comparisons between the dynamic modulus of the conditioned and unconditioned specimens primarily show that the moisture-induced dynamic modulus reduction tend to be larger as the voids in total mixture (VTM) increases, and the drainage layer materials may become more sensitive to VTM but less sensitive to temperature after being conditioned in moist environment. The investigation of phase angle ratio an...

Analysis of rigidity loss and deterioration from exposure in a decay test field of thermorectificated Eucalyptus grandis wood

The objective was to evaluate the elasticity dynamic modulus reduction (MOEd) and deterioration of E. grandis thermorectificated wood by exposure to environmental weathering. Six trees were used to obtain 14 logs of 2,4m, with seven from external (sapwood) and the others from internal (heartwood) part of the trunk. A total of 84 wood samples of 2,5x 5x 50cm were made, with half from the inner and the other from the external trunk portion. 14 treatments were evaluated with six replicates composed of thermorectificated wood submitted two differents times (2 and 4 hours) and three temperatures (200, 215 and 230°C). An ultrasound Stress Wave Timer device was used to evaluate MOEd and the mass measured by weighing. Samples remained in the decay test field for ten months, and monthly inspected and recorded to xylophogous organism�s occurrence. At the end of this period MOEd and mass were revaluated. The central portion of wood samples were more deteriorated, with mass losses and stiffness losses ranging from (8-56%) and (18-91%), respectively. Lower values ??were observed in the wood coming from the external portion, with mass losses and stiffness ranging from (3-10%) and (8-20%), respectively. The thermorectificated wood samples were more damaged by action the termites and less by the action of fungi, compared to controls.

Evaluating Adhesion Properties and Moisture Damage Susceptibility of Warm-Mix Asphalts

Through development and evaluation of the warm-mix asphalt (WMA) mixture design process, increased moisture susceptibility has been cited as one of the potential critical failure modes for WMA. Reduced production temperatures can affect the drying of the aggregate before mixing, the development of adhesion at the asphalt–aggregate interface, and binder stiffness. The objective of this research is to identify the significance of these factors and to define their relative contribution to mixture resistance to moisture damage. To evaluate the contribution of asphalt binder–aggregate adhesion, the bitumen bond strength (BBS) test was implemented on dry and moisture-conditioned samples. The effect of production temperature was simulated by heating aggregate substrates to hot-mix asphalt (HMA) and WMA temperatures before applying the asphalt binder. Furthermore, the effect of reduced binder stiffness resulting from lower production temperatures was considered through establishing two controls for mixture performance testing: a conventional HMA and a mixture prepared at WMA temperatures without WMA additives. The relevance of these factors was established through comparison with mixture performance as measured by the reduction in dynamic modulus, as a function of conditioning cycles. Mixture sample preparation allowed for consideration of residual moisture in aggregate that might have been associated with WMA and provided a control HMA sample prepared under standard conditions to establish a performance benchmark. Recommendations were made for incorporation of these new test methods into current WMA mixture design specifications. In summary, both BBS and dynamic modulus testing indicated that specific WMA additives could improve the mixture's moisture resistance and could offset any negative effects from the reduced production temperatures on moisture susceptibility. Therefore, selecting appropriate warmmix additives during the mix design process can help mitigate potential moisture damage associated with WMA.

Effect of hydrated lime on dynamic modulus of asphalt-aggregate mixtures in the state of North Carolina

A comprehensive experimental study has been conducted primarily to characterize the effect of hydrated lime on a dynamic modulus of Hot Mix Asphalt (HMA). In this paper, five Superpave HMAs typically used in the State of North Carolina were modified with hydrated lime and evaluated with a series of uniaxial compressive complex modulus tests. And a new design method was proposed for lime modified HMAs based on their volumetric optimums. For a 9.5 mm surface mixture, three levels of lime addition methods were tested and their impacts on a dynamic modulus and phase angle were statistically analyzed. Finally, a resistance of lime modified HMA to moisture damage was demonstrated by comparing with unmodified HMA. Findings suggested that the inclusion of hydrated lime should make HMAs stiff especially at high frequencies and lower temperatures. The reduction of dynamic modulus due to moisture was smaller in lime modified HMAs than in un-modified HMA.

Particle Dispersibility and Giant Reduction in Dynamic Modulus of Magnetic Gels Containing Barium Ferrite and Iron Oxide Particles

The particle dispersibility of barium ferrite and iron oxide magnetic particles in carrageenan gels was investigated, and the influence of the dispersibility on the giant reduction in the dynamic modulus of the gels was discussed. The gels containing barium ferrite demonstrated giant reductions in the storage Young's modulus on the order of 10 (5) Pa due to magnetization; however, small reductions in the storage modulus of less than 10 (4) Pa were observed for the gels containing iron oxide. The storage modulus of gels with barium ferrite did not follow the Krieger-Dougherty equation above volume fractions of 0.06, indicating the heterogeneous dispersion of the magnetic particles; however, the modulus of the gels with iron oxide satisfied the equation at all volume fractions, suggesting the random dispersion of the particles. It was noted that the gels with barium ferrite demonstrated enhanced nonlinear viscoelasticity and a large value of the loss tangent, while the gels with iron oxide exhibited weak nonlinear viscoelasticity and a small value of the loss tangent. Magnetic measurements indicated high values of remanent magnetization for barium ferrite and low values for iron oxide. After magnetization at 1 T, the magnetic gels with barium ferrite became elongated parallel to the magnetic field and shrunk perpendicular to the field. In contrast, the magnetic gels with iron oxide did not undergo a marked deformation. These results strongly indicate that the giant reduction in the storage modulus requires both enhanced nonlinear viscoelasticity and magnetostriction which originate from the particle dispersibility. The relationship between the dispersibility of magnetic particles and the giant reduction in the storage modulus is discussed using rheological and morphological data.

Magnetization-Induced Reduction in Dynamic Modulus of Polyurethane Elastomers Loaded with Ferrite

Magnetization effects on the dynamic modulus of a magnetic elastomer consisting of polyurethane and barium ferrite have been investigated. The complex modulus was measured before and after magnetization by dynamic viscoelastic measurements with a compressional strain. Giant reductions in storage modulus of ∼105 Pa and in loss modulus of ∼104 Pa were observed after magnetizing the elastomer at 1 T. The magnetic elastomer also showed a deformation with a strain of ∼10-4 caused by the magnetization. The observed giant reduction in dynamic modulus can be ascribed to the large nonlinear viscoelastic response of the magnetic elastomer and the magnetization-induced deformation. Nonlinear viscoelastic responses, morphologies of magnetic particles, and deformation for the magnetic elastomer are discussed.

Determination of kinetic changes of aggrecan-hyaluronan interactions in solution from its rheological properties

The kinetics of interactions between aggregating cartilage proteoglycan (aggrecan) and hyaluronan was examined through their rheological flow behavior using a cone on plate viscometer. The mixing of the two types of molecules was carried out directly on the plate of the viscometer, and aggregation process was monitored through the changes of the sample's steady-shear viscosity and/or dynamic shear modulus as a function of time. The effect of flow conditions on the aggrecan-hyaluronan interaction rates was examined by subjecting samples to steady-shearing motions at specified shear rates, and to oscillatory shear motions of specified frequencies and amplitudes. The characteristics of the kinetics of interaction between aggrecan and hyaluronan molecules depended not only on the flow conditions under which proteoglycan aggregation took place, but also on the concentration of the components in the solution. At high shear rates (> 10 s −1), viscosity of the mixture solution increased monotonically, starting near the viscosity of the aggrecan solution, and reaching the viscosity of the aggregate solution in approximately 35 min. Surprisingly, under slow shearing motions (< 10 s −1), the viscosities of the mixture solutions exceeded those of control aggregate solutions at identical hyaluronan: aggrecan ratios and concentrations. In addition, the aggregation under oscillatory motions took place near physiologic frequency (10 rad s −1) although the rate of aggregation process was much slower than under steady-shearing motion (> 100 min). However, the high-frequency oscillatory shearing (62.8 rad s −1) tended to impede aggregation resulting in a reduction of dynamic modulus over time. The influence of loading conditions on the rate of aggregation and aggregate size observed in this study seems to suggest a close relationship between proteoglycan structure and content, and degree of physiological stress throughout the joint and frequency of the joint motion.

Dynamic modulus of Portland cement paste and mortar as affected by ambient relative humidity

Results are given of an investigation into the influence of drying and wetting on changes in weight and dynamic modulus of paste and mortar specimens dried at different relative humidities at room temperature. Drying causes a significant drop in the dynamic modulus probably due to moisture stress gradients and removal of interlayer water which is recovered from subsequent wetting of the specimens. This suggests that drying-induced microcracking is unlikely to occur. The percentage reduction in dynamic modulus of prisms (2·5 mm × 10 mm × 75 mm) increases with increasing aggregate concentration and decreases with increasing water/cement ratio.

短繊維強化アイオノマー複合材料の引張および疲労特性

A study has been made on the tensile and fatigue properties of discontinuous carbon fiber reinforced ionomer composites oriented unidirectionally by hand-alignment technique.The fiber-matrix interfacial shearing strength calculated from the rule of mixture showed considerably lower value than that expected from the good adhesive ionomer matrix. The interfacial shearing strength decreased remarkably with increasing fiber length. It is considered that the fiber-matrix interfacial debonding can arise from the stress concentration at the fiber end, since the fiber overlaps are not perfectly in discontinuous fiber composites, and consequently, the interfacial shearing strength takes a very low value. It seems that the fiber-matrix contacts and the fiber overlaps decrease with increasing fiber length in discontinuous fiber composites oriented unidirectionally by hand-alignment technique.The low frequency fatigue tests on the unidirectionally oriented composites showed an excellent fatigue strength without braking for N=4×103 at 65% of ultimate tensile strength.The dynamic modulus of the fatigued Zn-type ionomer composite showed a 50% decrease against the virgin dynamic modulus at room temperature. The reduction of dynamic modulus may be related to the fiber-matrix debonding. On the other hand, the residual strength retained 90% of the virgin ultimate tensile strength. Even if the interfacial debonding occurs, the fiber could still carry load by the interfacial friction.

Wave Propagation and Dynamic Modulus in Continuous-Filament Twisted Yarns1

An analytical and experimental study of dynamic modulus in continuous-filament twisted yarns is performed to establish how small amplitude strain waves are propagated in this type of assembly and to determine if the dynamic and static moduli, as affected by geometric twist, are related. The dynamic modul us of nylon, dacron, viscose, and acetate yarns are measured as a function of twist angle at low stress levels, using the sonic velocity pulse-propagation technique. Excellent agreement between measured and predicted results indicate that, under these test conditions, strain waves propagate as longitudinal plane waves in a linear elastic medium, and the reduction in dynamic modulus with twist is principally a geometric effect which can be predicted by using the static extension theory.

The effect of compressive stress on the dynamic modulus of concrete

Summary Tests have been carried out to determine the effect of compressive stress on the dynamic modulus of concrete. These have indicated that a small reduction of modulus occurs when concrete is loaded but that no subsequent reductions occur while the load is maintained for periods up to six months. A similar reduction also occurs on releasing the load and with subsequent loading cycles. This effect, which is independent of the age of the concrete after fourteen days, is approximately proportional to the applied stress and becomes successively smaller for subsequent loading cycles. The reduction in dynamic modulus is always small, being about 5% or less.