The post-crack flexural performance of fiber-reinforced concrete (FRC) is commonly assessed using simple beam specimens such as the ASTM C1609/C1609M, Standard Test Method for Flexural Toughness of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading), third-point-loaded beam test. Like most beam-based test methods for FRC, the performance revealed by this test method exhibits high variability. An investigation based on variance-covariance analysis has been undertaken to examine the sources of variability in this test method and identify the true variability in FRC once extraneous test-related sources of variability have been isolated. This analysis has determined that friction in the supporting rollers and the location of the crack relative to the center of the beam are the main test-related sources of variability in FRC performance assessment using the ASTM C1609/C1609M test method. Given that the apparent magnitude of flexural strength also increases with friction, it is advisable to place limits on the maximum acceptable magnitude and variance in roller friction during a beam test so that the apparent variability in the output can be moderated. Control of the location of the crack in a third-point-loaded beam is more difficult and may not be desirable when seeking a representative estimate of mean flexural performance.
An integrated multiscale framework combining hydration kinetics and lattice modeling was established to investigate the microstructural evolution of cement paste. To overcome the inherent overestimation of pore connectivity in traditional models, a nucleation-and-growth mechanism coupled with a small capillary pore redistribution algorithm was incorporated into the generation of representative volume elements featuring polydisperse particles. This approach ensures that the simulated pore network characteristics, such as pore size distribution and percolation threshold, closely align with authentic microstructures. Experimental validation using nuclear magnetic resonance confirms the accuracy of the simulated porosity development. Quantitative structural analysis revealed that, in systems with low water-to-cement (w/c) ratios, connectivity reduction accelerates and tortuosity increases rapidly as hydration progresses, whereas high w/c ratio systems exhibit significantly more gradual variations. Furthermore, both connectivity and tortuosity demonstrated strong correlations with capillary porosity but negligible direct dependence on initial w/c ratios. The derived fitting curves for these structural parameters provide a robust mechanistic basis for durability assessment and service-life prediction of cementitious materials.
In this study, calcium sulfoaluminate cement (CSAC) was used as a more sustainable material to stabilize high plastic clayey soil compared to ordinary Portland cement (OPC). Both CSAC and OPC were used and studied as soil stabilizers. The percentages of both cements used were 2.5%, 5.0%, and 7.5 % by dry weight of soil and cured for 0, 7, 14, and 28 days in a water bath. The clayey soil was characterized by using the Atterberg limit, specific gravity, and miniature Proctor test. Samples for the unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were prepared at optimum moisture content and maximum dry density. The stabilized clay samples were tested for UCS and UPV tests as per American Society of Testing and Materials guidelines. Results showed that both types of cement improved the strength of the clayey soil with curing periods. The UCS test showed that samples prepared with CSAC were stronger without curing, but OPC-treated samples showed higher strength after a curing period. The UCS value reached a maximum of 1,758.16 kN/m2 for 7.5 % CSAC-treated samples at 28 days of curing, whereas the UCS value reached up to 3,261.22 kN/m2 for OPC-treated samples. The UPV test also showed that the addition of both types of cement to clayey soil samples increased its strength. The UPV value for untreated soil was 990.5 m/s, whereas CSAC-treated samples showed an increase between 1,275.13 and 1,647.8 m/s. The OPC-treated samples had an increase between 1,355.25 and 2,043.63 m/s. All OPC-treated samples had higher UPV values than CSAC-treated samples.
The accelerating deterioration of road infrastructure, exacerbated by increasing traffic loads and climate variability, necessitates sustainable and intelligent rehabilitation strategies. Simultaneously, the environmental footprint of conventional bitumen underscores the need for eco-friendly alternatives. This study explores an integrated approach to sustainable pavement rehabilitation by combining waste-modified asphalt mixtures with an artificial intelligence (AI)-driven road defect management system. VG-30 bitumen was modified using lignin and waste engine oil (WEO), both individually and in hybrid formulations, to evaluate their effects on physical, thermal, and mechanical properties. Lignin improved stiffness, softening point, and rutting resistance, whereas WEO enhanced ductility and low-temperature flexibility. Hybrid mixes such as L20EO6 and L30EO9 demonstrated a balanced response, mitigating the brittleness of lignin and the excessive softening from WEO. All modified binders satisfied storage stability and thermal safety requirements. The study also developed a threetier AI framework for automated pavement inspection and maintenance prioritization. Using a curated data set of manually annotated images, a YOLOv7 model was employed for real-time detection of potholes, cracks, and rutting, whereas U-Net segmentation quantified defect severity based on area and geometry. The models achieved high accuracy, with YOLOv7 reaching 96.8 % mAPat0.5 and U-Net providing an average Intersection over Union of 0.85. The results demonstrate that hybrid lignin-WEO-modified asphalt mixtures can offer both environmental advantages and improved mechanical performance, whereas the AI-based framework enhances efficiency in defect detection, classification, and maintenance planning. The integration of sustainable materials with intelligent defect prioritization presents a feasible solution for cost-effective and environmentally conscious pavement management in resource-constrained regions.
The alteration in microstructure or phase composition of concrete subjected to aggressive surroundings results in the reduced working life of concrete structure. The diffusion of ions in concrete subjected to aggressive surrounding mainly chloride and sulfate are not uniform and depends on various parameters that make complex variations in the microstructure or phase composition along the depth of concrete, which may affect the further ingress behavior of ions and reaction mechanism. This study reported the change in microstructure or phase composition along the depth of concrete subjected to aggressive solutions containing chloride and sulfate. For this purpose, chloride diffusion and microstructure analyses were performed on various concrete mixes along the depth and exposed to chloride (3% NaCl: 3NC) and chloride with sulfate (3% NaCl with 4% Na2SO4: 3NC with 4NS) solutions. From the result of chloride ingress test, the existence of NS in surrounding solution retards ingress/diffusion of chloride ions into the concrete. The microstructure analysis revealed non-uniform distributions of key phases, including calcium hydroxide (CH), ettringite (E), and calcium chloroaluminate (CCA), within the concrete matrix. The distribution patterns, which varied with the depth of concrete and type of exposure solutions and binder used, are described comprehensively. CH content decreased closer to the exposure surface and increased with greater depth intervals, while E was more prominent at intermediate depths compared to lower and higher levels. CCA content was slightly higher at lower depth intervals. Notably, CCA was more prevalent in ordinary portland cement with 20 % fly ash concrete (O20FAC) at lower depths, while E content exhibited differences between binder types and exposure solutions, with implications for concrete performance.
The global trend of increased sewage sludge (SS) generation, driven by population growth, economic development, and the expansion of sewage collection and treatment services, has heightened environmental and public health concerns, particularly after the detection of the COVID-19 virus in SS. These factors underscore the importance of developing safe, rational, and efficient methods for the utilization or recycling of SS. Incineration has been evaluated as an alternative to landfilling. Although it is not waste-free, it generates SS dry solids amounts, which can be used as supplementary cementitious materials. This study evaluated the effect of incineration temperature on the chemical properties of sewage sludge ash (SSA) and assessed their reactivity in cement pastes. To this end, loss of ignition, X-ray diffraction, energy-dispersive X-ray fluorescence, and pozzolanicity were performed on the obtained SSA. Based on these results, SSA incinerated at 650 degrees C and 800 degrees C were selected for producing cement pastes. These SSA were used to replace 10 % of the portland cement by mass and compared with cement-based pastes containing the same amount of fly ash. The SSA produced in this study were classified as nonpozzolanic, and the incineration temperature influenced their chemical characteristics. Reactivity of the SSA was observed with the portlandite released during cement hydration, and the mechanical behavior of SSA pastes was comparable to that of the pastes made with fly ash.
High early strength concrete (HESC) has many applications, particularly in the repair and restoration of concrete pavements. These mixtures are designed for rapid strength development using a low water-to-cement ratio (w/cm), specialized cement types (often in higher dosages), and specialized admixtures. Although HESC effectively achieves the required strength, it poses durability challenges. Several studies have explored the effect of these HESC design parameters on strength gain and have provided recommendations to improve it. However, there is limited documentation regarding its durability properties. To better understand HESC's durability properties, a set of mixtures was analyzed for strength, freeze-thaw durability, and both autogenous and drying shrinkage. These HESC mixtures were composed of low cement content 334.6 kg/m(3) (564 lbs./yd(3)) using ordinary portland cement type III, w/cm of 0.35, three different admixture types, and internal curing (IC) using presaturated lightweight aggregates. It was observed that all HESC mixtures, despite their low cement content, met the criteria established by KDOT Section 833, attaining a minimum compressive strength of 12.41 MPa (1800 psi) and a flexural strength of 2.62 MPa (380 psi) within 6 h of mixing. Furthermore, admixture compatibility and usage of IC for HESC significantly affected their durability properties. HESC with IC demonstrated superior freeze-thaw performance and minimal shrinkage, likely due to their ability to regulate heat during hydration. Although three different admixture types were evaluated for the same mix design and fresh property range, their varying performances emphasize the need to verify admixture compatibility and durability properties before employing them on-field.
An experimental study was conducted to assess the effect of proteins as air-entraining agents in different binary cementitious systems. More specifically, air-entraining performance, mechanical properties and transport characteristics of cement pastes blended with up to 30 % fly ash and slag and air entrained with different proteins were evaluated. The experimental program included measuring the hydrophobization of the cement matrix, microstructure, compressive strength, water absorption, and electrical resistivity. It was found that the air-entraining performance of proteins in blended cement binders is affected, and the degree of this effect depends primarily on the properties of each protein. There appeared to be a general reduction in air-entrained porosity in the blended systems containing fly ash in most protein cases. Although the overall water absorption did not show a correlation with air-entrained porosity, a softening of the transition point between initial and secondary absorption was observed and attributed to a wider distribution in void sizes in the pastes air entrained with proteins. In addition, the electrical resistivity of the pastes air-entrained with proteins did not demonstrate a strong correlation with air-entrained porosity indicating a complex influence of proteins on pore structure and pore solution chemistry.
The use of lightweight concrete is gaining prominence in civil engineering because of its effectiveness in minimizing dead loads. However, the increased reliance on concrete has accelerated the depletion of natural resources, raising environmental concerns. This challenge has led to a growing interest in finding sustainable alternatives within the field of civil engineering. This study focuses on the enhancement of bottom ash (BA) to develop a well-graded version (BAW). It examines the impact of replacing fine aggregates with BAW on the mechanical and thermal characteristics of lightweight concrete. The research experimented with different BAW incorporation levels, ranging from 5 % to 35 % by volume. The results showed a consistent decrease in concrete density with increasing BAW replacement, as well as varying changes in mechanical and thermal performance across the tested range of 0-35 % by volume. Mechanical and thermal properties peaked at 15% before falling. Compressive strength peaked at 36.7 MPa at 15% and dropped to 26.9 MPa at 35%. Flexural strength increased to 2.85 MPa at 15% and 2.57 MPa at 35%. Split tensile strength increased to 0.76 MPa at 15% and decreased to 0.63 MPa at 35%. Ultrasonic pulse velocity reached a maximum speed of 3.86 km/s at 15% and 3.18 km/s at 35 %. Thermal conductivity increased to 1.67 W/mK at 15 % and dropped to 1.06 W/mK at 35 %. The 15 % BAW level optimizes performance, whereas higher replacement rates increase porosity. These findings indicate that well-graded BA enhances the properties of concrete, offering reliable and sustainable material for use in modern construction.
Adding fiber segments to a concrete mix design could influence the rheological properties of the mortar. In this study, the filling performance of steel fiber-reinforced self-compacted mortar (SFRSCM) into granular packs is investigated to produce steel fiber-reinforced rock-filled concrete. This investigation considers using steel fiber segments with different fiber aspect ratios and fiber volume fractions using the OpenFOAM computational fluid dynamics program. For this purpose, the Interfoam solver, which can simulate SCM flow, had to be upgraded to accurately characterize the motion of the fiber segments and calibrate it with experimental and numerical data from the literature. This study demonstrated that the SCM flow without fiber reinforcement has a better filling performance than the SFRSCM flow. In addition, new relations are proposed to describe the effects of the addition of fiber segments on the rheological properties of SCM. The results demonstrated a strong correlation between the proposed equations and their practical application. Furthermore, a general equation was proposed and validated by using cases from the literature, indicating its efficacy in predicting yield stress for various mixture designs with diverse fiber diameters and volume fractions. This implies that these equations may be used in future research and within the construction industry. Specifically, they could be used in mix design to adjust the amount of steel fiber segments while preserving the flowability characteristics of the SCM.
The increasing demand for sustainable construction materials has led to significant advancements in asphalt pavement technology. This study explores the incorporation of three types of microplastics-recycled polypropylene, recycled high-density polyethylene (HDPE), and re-purposed low-density polyethylene (LDPE)-at dosages of 0.3 %, 0.6 %, and 0.8 % into 100 % reclaimed asphalt pavement (RAP) with the addition of the warm mix asphalt additive, Evotherm P25. A comprehensive evaluation was conducted through laboratory tests, including the indirect tensile cracking test (IDEAL-CT), ideal shear rutting test (IDEAL RT), Cantabro loss test, and moisture susceptibility test, to assess the mechanical and durability performance of the modified asphalt mixtures. The results demonstrated that microplastics enhanced the cracking tolerance index but reduced the workability, particularly in HDPE-modified mixtures. Similarly, LDPE showed improved volumetric properties due to its melting behavior during mixing but resulted in higher mass loss in the Cantabro loss test. Although HDPE improved rutting resistance, increasing plastic dosages adversely affected rutting performance. The moisture susceptibility test revealed tensile strength ratio values below the standard threshold of 80 % for all samples, indicating low resistance to stripping. These findings provided insight into modifying 100 % RAP with microplastic as a potential pothole-repairing material or other low-risk asphalt applications.
Arkansas is the leading supplier of long-grain rice in the United States. Rice husk is an agricultural waste that is burned under controlled conditions. The ash produced in the milling process of rice has a high percentage of silicate, which is a pozzolanic material and can potentially improve the properties of poor-quality soils. The main objective of this study is to evaluate the optimum amounts of rice husk ash (RHA), hydrated lime (HL), or RHA plus HL by investigating two local subgrade soils from Arkansas. The treated soils were subjected to different tests such as Atterberg limits, modified proctor, unconfined compressive strength, California bearing ratio, pH, and free swell (FS). Test results show that both RHA and HL reduce the plasticity and the maximum dry density of the soil. In contrast, the strength properties of the tested soils increased with the incorporation of either RHA or HL. The FS results showed both RHA and HL mitigated the swelling of the soils. However, HL was found to be more effective in reducing soils' FS than RHA. The HL dramatically increases the pH of the soil, but RHA does not have a notable effect on it. Six percent RHA and 3 % HL were found to be the optimum dosages in treating clayey and silty soils. The combination of RHA and HL was capable of reducing the swelling potential as well as improving the strength properties. Considering laboratory test results and economic analysis, 4 % RHA+1 % HL is recommended for stabilizing poor clayey and silty subgrade soils.
Shrinkage reducing admixture (SRA), shrinkage compensating admixture (SCA), and superabsorbent polymer (SAP) have been commonly used to reduce shrinkage of high-performance concrete (HPC); however, their comparative effectiveness is still not clear. In this article, the effects of SRA, SCA, and SAP on strength, autogenous/drying shrinkage, restrained ring shrinkage, and pore structure of HPC were studied. The dosages of SRA, SCA, and SAP were varied within 2.5–7.5 L/m3, 2.5–7.5 %, 0.4–1.4 g/kg, respectively. The results indicated that SRA and SCA decreased the shrinkage with their dosages increasing. However, the presence of SAP in HPC mitigated the autogenous shrinkage weakly and raised the free drying shrinkage. SRA, SCA, and SAP all reduced restrained ring shrinkage. SCA was the best admixture to increase compressive strength and reduce shrinkage in HPC. Additionally, the micromechanisms of SRA, SCA, and SAP on shrinkage reduction were addressed based on pore structures. The reduction of mesopore percentage was a primary reason to restrain the shrinkage behavior with the addition of SRA, SCA, and SAP. Moreover, linear fitting models of shrinkages in function of mesopores percentage were proposed. The shrinkage property of HPC could be explained by the mesopores percentage.
This study demonstrates the successful use of eco-friendly recycled glass powders (RGPs) in mortar and concrete as pozzolanic substitute for portland cement. As part of the evaluation, two RGPs were produced by steel and ceramic ball mills, namely, RGP (SB) and RGP (CB), respectively. Also included in the experiment as a reference was a commercial ceramic ball-milled RGP. All three evaluated RGPs were found to be reactive pozzolans based on a series of reactivity test results, including a strength activity index of greater than 80 % on all ages of 7, 28, and 56 days in mortar and concrete. Multiple indicators, such as higher generated heat in pozzolanic reactivity testing by isothermal calorimetry and portlandite consumption, indicated ceramic milling could produce a more reactive glass pozzolan, perhaps from the alumina residue from ceramics milling media. However, the higher reactivity of RGP (CB) did not lead to a greater compressive strength when used in concrete. Furthermore, a color difference was not detected between RGP (SB) and RGP (CB) concrete specimens. This study shows that both steel and ceramic media are viable for RGP production based on pozzolanic reactivity, strength, electrical resistivity, and concrete color. Other factors, such as productivity and cost, should be considered when choosing the proper production method for RGP at the industrial scale.
To explore the rheological properties and the modification mechanism of graphene/rubber composite-modified asphalt, a dynamic shear rheometer and low-temperature bending rheometer were used to study the high and low-temperature rheological properties of graphene/ rubber composite-modified asphalt. Second, the microstructure and chemical structure of the asphalt were characterized by using Fourier transform infrared spectroscopy and optical microscopy, and the component model of asphalt was constructed with molecular dynamics simulation technology to explore the modification mechanism of graphene/rubber composite- modified asphalt. The results show that compared with rubber-modified asphalt, graphene/ rubber composite-modified asphalt effectively improves the high-temperature deformation resistance and low-temperature crack resistance of asphalt, but the ability of graphene to improve the low-temperature performance of asphalt is limited at -24 degrees C or even lower temperatures. The addition of graphene promotes the swelling development of rubber, improves the bonding stability between rubber and resin, and enhances the compatibility between rubber and asphalt systems. Graphene can weaken the aggregation behavior of rubber and asphaltene, and the distribution of rubber and asphaltene in asphalt is more uniform, further improving the overall stability of the asphalt system. Graphene promotes the adsorption of lightweight components by rubber, leading to a decrease in the diffusion coefficients of saturated and aromatic components in asphalt systems. This is also an important reason for the improved high-temperature performance of graphene/rubber-modified asphalt.
Fly ash has traditionally served as a supplementary cementitious material in the production of concrete, enhancing its mechanical and durability properties through pozzolanic activity. However, with the ongoing decommissioning of coal-fired power plants due to environmental concerns and the shift toward renewable energy sources, the anticipated shortage of fly ash has materialized, prompting the exploration of alternatives for producing durable and sustainable concretes. One promising substitute for fly ash is limestone powder (LP), which garnered attention in recent years for its cost-effectiveness and widespread availability, primarily as a partial replacement for cement in cement-based materials. This study investigated the feasibility of using LP as a substitute for fly ash, aiming to assess its potential impact on concrete properties by formulating seven concrete mixtures, including a control mixture with 70 % cement and 30 % fly ash out of total cementitious materials. Various levels of fly ash replacement with LP, ranging from 5 to 100 %, were explored in the LP modified mixtures. Fresh and hardened properties of the concrete were evaluated to assess the impact of LP substitution for fly ash. The findings revealed that reducing the fly ash content led to increased air content and porosity, consequently lowering mechanical strength. Nonetheless, replacing fly ash up to 30 % with LP resulted in reduced drying shrinkage by 47 % compared with that of the control mixture. Furthermore, the susceptibility to chloride ion ingress was assessed using the rapid chloride permeability test, with charge passed values ranging between 2,000 and 4,000 coulombs, indicating a moderate level of susceptibility. Moreover, LP modified mixtures exhibited superior resistance to freeze-thaw cycles compared with the control mixture. These results underscore the potential of LP as a viable alternative to fly ash in concrete production, offering enhanced durability and sustainability.
This paper studied saline soil's water and salt migration behavior under evaporation conditions by a self-designed experimental device, and the evolution law of the water content, conductivity, and temperature in different heights of saline soil roadbeds was analyzed. The test results show that at an ambient temperature of 18 degrees C, the water-salt migration of saline roadbed is mainly concentrated in the early stage of hydration (<= 48 h), which shows a typical phenomenon in which salt in the soil follows the water and the conductivity of soils increases synchronously with the water content. Under the evaporation condition, the decreased rate of water content was accelerated in the sample area near the heat source, resulting in a constant increase in the rate of conductivity and a wider salt aggregation area. Further, a critical sub- grade height prediction model is established based on the maximum salt and water migration height in saline soil roadbeds with the help of Hydrus numerical simulation software. The model analysis results show that the migration rate of salts gradually lags behind that of water because the burial depth of groundwater increases under evaporation conditions. When the burial depth of groundwater is <1.5 m, the change of water-salt migration of the roadbed is gradually stabilized, and the height of salt erosion area on saline soil roadbed no longer rises. The research conclusions can guide the design level of the structure of saline soil roadbeds under evaporation conditions.
The retro-reflectiveness of the vertical signaling films allows drivers to drive more assertively, directly impacting safety. By collecting retroreflectance (RR) data for 24 months on federal highway BR-381 (Brazilian federal highway – Number 381), in Minas Gerais, Brazil, it was possible to evaluate the RR performance over time of films and the influence of high temperatures from forest fires on the loss of retroreflective capacity. Once the performance equations of the films were determined, the minimum residual RR was verified, certifying the durability foreseen by the standard. Films subjected to burning showed partial or total loss of retroreflective capacity. The films were analyzed in the laboratory, and the degradation was evaluated through accelerated tests at high temperatures. The films were subjected to temperatures of 70°C for 736 h and 100°C for 4 h. It was possible to identify a behavior equation for the films at 70°Cand correlate them to the field study, thus defining a degradation acceleration factor that accurately reflects the natural behavior of the films. Exposure to 100°C was very severe, and verifying a behavioral equation for the process was impossible. Optical microscopy allowed the degradation of the films to be observed as a function of degradation time and temperature. Therefore, degradation at 70°C has the potential to be used as a parameter for accelerated durability testing.
This study investigates the effect of aluminum hydroxide (1 and 7 %), cement/silica ratio (30 and 60 %), autoclave temperature (175°C and 184°C), and curing time (8 and 16 h) on the modulus of rupture (MOR) of fibercement composites using a factorial design of experiments. The cellulose fibers, the water, and the plasticizer were fixed in the experiment. All the components were mixed and stirred until a homogeneous, moldable, and compacted paste was obtained. The samples were cured in an autoclave chamber. Physical properties such as morphology, structure, density, and water absorption were tested. The results show that the cement exhibits crystallinity. Excessive crystallization of its constituents occurs when the autoclave conditions are increased. Changes in composition and curing conditions have a slight effect on the density, a moderate effect on the water absorption capacity, and a strong effect on the MOR with variations of 5, 12, and 42.7 %, respectively. The cement/silica ratio and temperature were shown to be the most important variables in the experimental design. The factors that did not influence MOR were aluminum hydroxide concentration and autoclaving time. The MOR of the boards was improved by increasing the cement/silica ratio and reducing the temperature.
The pressure aging vessel (PAV) protocol is adopted worldwide for quality control on any bitumen available. However, crumb rubber-modified binders (CRMB) produced by wet technology are nonhomogeneous materials in which rubber particles are dispersed into the bituminous matrix, and the interaction between the two constituents can be triggered at any time by increasing temperature. It is assumed that the PAV temperature is insufficient to trigger such interaction. This assumption has never been verified. If proven otherwise, any rheological measurement performed on the PAV-aged rubberized bitumen could be questionable because the material undergoes unrealistic physicochemical changes. This research aims to take the first step toward understanding the validity of this assumption and the need for the current PAV aging protocol to be modified for CRMBs. Rubber particles from end-of-life tires were embedded in the bitumen and subjected to five subsequent PAV aging cycles at 110°C, which is suitable for the climate in the Gulf region, including the United Arab Emirates. After each cycle, micro-computed tomography (CT) scans were used to evaluate the swelling of the rubber particles as a measure of interaction between rubber and bitumen. The PAV temperature was then reduced to 90°C and 70°C, and samples were subjected to the same micro-CT scan evaluation. Results showed that the temperature of the current PAV protocol (110°C) initiates the interaction at every aging cycle. Lower aging temperatures help reduce the magnitude of the interaction effects. A draft modification of the current PAV aging protocol is proposed by modifying the aging temperature to 70°C and extending the aging period to eight days. This change in the long-term laboratory aging procedure can better reflect the effects of aging (oxidation) by minimizing the influence of rubber swelling.
