Journal of Materials in Civil Engineering

Modeling the spatial variability that exists in pavement systems can be conveniently represented by means of random fields; in this study, a probabilistic analysis that considers the spatial variability, including the anisotropic nature of the pavement layer properties, is presented. The integration of the spatially varying log-normal random fields into a linear-elastic finite difference analysis has been achieved through the expansion optimal linear estimation method. For the estimation of the critical pavement responses, metamodels based on polynomial chaos expansion (PCE) are developed to replace the computationally expensive finite-difference model. The sparse polynomial chaos expansion based on an adaptive regression-based algorithm, and enhanced by the combined use of the global sensitivity analysis (GSA) is used, with significant savings in computational effort. The effect of anisotropy in each layer on the pavement responses was studied separately, and an effort is made to identify the pavement layer wherein the introduction of anisotropic characteristics results in the most significant impact on the critical strains. It is observed that the anisotropy in the base layer has a significant but diverse effect on both critical strains. While the compressive strain tends to be considerably higher than that observed for the isotropic section, the tensile strains show a decrease in the mean value with the introduction of base-layer anisotropy. Furthermore, asphalt-layer anisotropy also tends to decrease the critical tensile strain while having little effect on the critical compressive strain.

Geopolymers are used for several applications due to their sustainability, low density, low cost, excellent thermal properties, and fire resistance. Geopolymer concrete (GC) may possess superior fire resistance compared to conventional concretes with ordinary portland cement (OPC). The proper understanding of the effects of elevated temperatures on the properties of GC is essential. In the research reported in this paper, relationships are proven for normal and high-strength GCs at elevated temperatures to establish efficient modeling and specify the fire-performance criteria for concrete structures. They are developed for unconfined GC specimens that consist of compressive strength, modulus of elasticity, flexural strength, thermal strain, prestressed thermal strain, and the compressive stress–strain relationships at elevated temperatures. The proposed relationships at elevated temperature are compared with experimental results and available OPC relationships. These results are used to establish more accurate and general compressive stress–strain relationships.

In this work, the effects of rice husk ash and metakaolin additions on magnesium sulfate and corrosion resistance properties of self-compacting concrete are reported. Comparisons are made to unblended self-compacting concrete to show the influence of the additions and replacements. Cement is replaced on a binary and ternary basis by 5–30% and 10–40%, respectively, of rice husk ash and metakaolin. Magnesium sulfate and corrosion resistance are analyzed after magnesium sulfate immersion for one year and with an accelerated corrosion test. The observational results showed that specimens exposed to a 5% magnesium sulfate solution exhibited the lowest weight loss for 10% rice husk ash, 20% metakaolin, and 20% rice husk ash in combination with metakaolin-blended self-compacting concrete. Likewise, it was noted that the tricalcium aluminate content of the binder influences the sulfate and the corrosion properties of self-compacting concrete.

Using carbonate-producing bacteria is a promising novel technique to improvement of concrete characteristics. Durability of concrete in harsh environments such as sulfate exposure has been constantly an important issue. The intention of the current study is evaluation of durability improvement of concrete containing bacteria exposed to sulfate environment. To do so, seven groups of 70-mm concrete prisms were made using two different bacterial strains accompanied with mixing water; the effects of sulfate solution exposure on durability properties of tested specimens including mass variation, volume variation, water absorption, and compressive strength were then determined. Furthermore, seven groups of concrete discs with 100 mm diameter and thickness of 50 mm were prepared from the aforementioned batches to investigate the chloride permeability of bacterial concrete by rapid chloride permeability test (RCPT). The results indicated that bacteria incorporation in concrete reduces mass variation, volume variation (in higher ages), and water absorption; it also increases the compressive strength of the specimens. The results also showed that the 28-day compressive strength of the bacteria-containing concretes is about 20% more than that of the control specimens. Moreover, bacterial concrete have lower chloride penetration in comparison with the control specimens.

Energy dispersive X-ray spectroscopy (EDS) is a microanalysis technique for material characterization that can provide accurate quantification of elemental composition while maintaining high spatial resolution. EDS microanalysis studies on cementitious materials can face several challenges essentially due to the complex chemical and mineralogical characteristics of cement hydration products. Furthermore, EDS microanalysis is widely carried out in “standardless analysis” mode, which relies on the internal standards of the microanalysis software. This can lead to highly erroneous analysis results because standardless analysis typically normalizes total to 100% without taking chemically bound water into account. In the case of quantifying chlorine content of a cement paste, such normalization is unacceptable because it can lead to overestimation. For accurate determination of elemental concentrations, X-ray spectra collected from minerals or glasses with known chemical compositions are necessary as references. This paper examines the performance of six different minerals containing a wide range of chlorine concentrations as standards for quantitative EDS microanalysis. Also, the influence of experimental conditions such as beam current, accelerating voltage, dwell time, and scanning mode on the obtained results is discussed. It was found that among the minerals investigated, scapolite [(Na,Ca)4(Al3Si9O24)Cl] stands out as the most favorable microanalysis standard for quantifying chlorine content in cement paste.

The introduction and use of chemical admixtures like polycarboxylate-based high-range water reducers (HRWR) and commercially ternary blended cements has allowed the successful production of self-consolidating concrete (SCC) for casting heavily reinforced sections, with poor access for vibrators and complex shapes of formwork. However, very little information is available on the influence of these chemicals and ternary blended cements on the time-dependent behavior of SCCs and particularly for those used in repairs. A laboratory investigation was undertaken to evaluate the potential of flexural creep behavior of several SCC mixtures by comparing their time-dependent behavior, which was monitored during the first two months. From the results, it became clear that the flexural creep potential of SCC varies widely depending on the nature of the high-range water reducer (HRWR) in use. It is also shown that even when belonging to the same polycarboxylic family as per the ASTM classification, the magnitude of flexural creep also varies widely depending on the properties of the polycarboxylic chemicals admixture in use. The paper summarizes the results of the experimental study that involved the comparison of data obtained from 10 SCC mixtures.

Segregation is a common problem in self-consolidating concrete (SCC), which is sensitive to mix proportions such as superplasticizer dosage, as well as the size, volume, and gradation of the aggregate. Dynamic segregation, when coarse aggregate lags behind during the flowing process, is distinguishable from static segregation, when coarse aggregate settles in concrete at rest. In the research reported in this paper, a flow trough and a concrete rheometer were used to study the effects of various aggregate properties and concrete rheology on dynamic segregation of SCC. An equation for the drag force was found useful to understand how various mix proportions and concrete rheology affecting dynamic segregation. Higher paste volume, lower superplasticizer percent by weight of cement, lower slump flow, smaller coarse aggregate, and better gradation may increase dynamic stability. Smaller aggregate size has more significant effect than other aggregate properties. Mixtures with dynamic yield stress less than 50 Pa exhibited severe segregation from both flow trough and visual stability index (VSI) tests. Mixtures with static yield stress of 250 Pa or higher had satisfactory dynamic stability, while mixtures with static yield stress of 100 Pa or lower showed severe dynamic segregation. No clear correlation was observed between concrete plastic viscosity and dynamic segregation.

The influence of $\mathrm{nanolimestone}/\mathrm{nano}{\mathrm{CaCo}}_3$ (NC) on the properties of ultrahigh-performance concrete (UHPC) cured at standard and heat conditions was experimentally investigated. The NC was used at ratios of 1, 2, and 3% as partial mass replacement for cement. Incorporating NC accelerated the hydration reactions of UHPC because of the nucleation effect. On the mechanical properties aspect, a threshold value of the NC content was found so that the compressive, flexural strengths, and flexural to compressive strength ratio of the UHPC were found to increase as the NC content increased towards the threshold content, and then to decrease with the increase of NC contents when the threshold was surpassed. Conversely, replacing cement with NC decreased flowability and increased the amount of autogenous shrinkage of the UHPC. While the NC accelerated the cement hydration process, it also acted as an effective filling material, resulting in enhanced mechanical properties and denser microstructure compared with the control UHPC mixture. Thus, through the use of NC, more environmentally friendly UHPC can be produced by reducing its cement factor and achieving enhanced engineering properties.

Reclaimed asphalt pavement (RAP) is widely used to construct new asphalt pavement layers, but its use is often limited in surface courses because of concerns about frictional performance, especially in areas where polish-resistant aggregates are scarce or not available. The goal of the research reported in this paper was to determine the maximum amount of RAP that can be blended with high-friction aggregates and used in surface mixes without significantly impacting frictional properties. The properties of RAP from six different sources were evaluated to determine typical RAP characteristics and used to fabricate a mixture simulating a worst-case scenario RAP with a low-friction aggregate. That RAP mixture was used to evaluate the frictional characteristics of two types of hot-mix asphalts with various amounts and types of high-friction aggregates. Specimens were subjected to laboratory polishing to simulate the effects of traffic. Results suggest that the threshold level of RAP in surface mixes that will not have detrimental effect on their frictional properties was about 30%, even when the RAP contained a highly polishable aggregate.

The effect of treating limestone quarry fines (LQFs) with a commercially available liquid polymeric soil stabilizer, and a combination of the polymeric soil stabilizer and a small quantity (4%) of portland cement was evaluated. The research reported in this paper, which consisted of tests on both treated and untreated mixes, with the aim of evaluating the use of LQF in pavement construction was comprised of the following tests: (1) compaction, (2) unconfined compressive strength, (3) static flexural strength, and (4) durability. Test results showed marked improvements in the optimum moisture content, unconfined compressive strength, and static flexural strength, and no improvement in maximum dry density when polymer or both polymer and cement were added. Improvements in unconfined compressive strength were above the U.S. national requirements for admixtures for soil stabilization. Polymer-treated specimens were more susceptible to moisture than specimens treated with portland cement (PC) alone, and polymer plus PC. The latter showed the best durability when submerged in water. The LQF can be treated for low-volume road pavement applications with the stabilizers.

In common engineering practice, data plots, such as the stress versus strain relationship of materials, are averaged among a series of samples using the mean ordinate (MO) method. This method is reliable as long as the sample performance does not vary significantly. If the stress versus strain curve of individual samples differs significantly in terms of shape, peak stress, and corresponding strain, the MO method may result in misleading average curves that do not adequately represent the material behavior. In this paper, an equal arc segment (EAS) method for averaging data plots is presented. Based on experimentally obtained compressive stress versus strain curves for pervious concrete, a comparison has been conducted between the proposed EAS method and the MO method. The results show that the EAS method outperforms the MO method, especially where there are high variations in the data pool. The EAS method is not limited to pervious concrete as showcased here, but can be applied to other data plots as well.

In this study, the usability of raw rice husk (RRH) instead of polypropylene fibers (PP) in high-strength concrete was investigated to prevent spalling, improve mechanical, physical, and thermophysical properties of concrete after high temperature treatment. Carbon dioxide (${\mathrm{CO}}_2$) and carbon monoxide (CO) emissions of concrete mixes were also measured at different temperatures. The test results show that when RRH is used at 3% of cement by weight it can prevent explosive spalling and can be a suitable alternative to PP. Due to the lower thermal conductivity of RRH, the RRH mixes had lower thermal conductivity values at all temperatures compared with the PP mixes. The addition of RRH slightly decreased the mechanical properties of the concrete and modified its thermophysical properties by decreasing thermal conductivity and the vapor diffusion resistance factor. Up to 300°C, the CO and ${\mathrm{CO}}_2$ emissions of the RRH mixes were similar or in some cases lower than those of the PP mixes. At 600°C, the ${\mathrm{CO}}_2$ and CO emissions of the RRH mixes were higher than those of the PP mixes.

This work focuses on improving the linear viscoelastic characterization of asphalt concrete materials with a standard indirect tension setup. Three main aspects distinguish this investigation from typical efforts. First, the applied diametral force history consisted of load–unload–rest sequences; this was done to enable separation between recoverable and irrecoverable deformation components. Second, viscoelastic properties were essentially calibrated against the recoverable deformation part to guarantee agreement with the sought constitutive theory; response during rest intervals was modeled for this purpose, assuming inactivity of the irrecoverable deformation part. Third, diametral forces were alternated between tension and compression; this was done to restrain the accumulation of irrecoverable deformation and to widen the calibration domain. Detailed step-by-step guidelines are included and applied to clarify the approach. For pavement engineering purposes, the overall scheme is deemed an improvement over common or existing methods.

Lightly cementitiously stabilized granular materials are generally characterized by their tensile properties and this paper examines the use of monotonic and cyclic load flexural testing to determine the tensile characteristics of these materials. The research reported in this paper included the determination of modulus of rupture as well as static and dynamic stiffness moduli from monotonic and cyclic load flexural testing for two typical freshly quarried granular base materials stabilized by the addition of 1–3% cement–fly ash slow-setting binder. A flexural testing setup with improved deformation measurement was developed and the tests were conducted on 28-day cured samples prepared by static compaction. Details of improved flexural testing arrangement with on-sample midspan deflection measurement for performing monotonic and cyclic load testing to obtain reliable data are also discussed. The research reported in this paper indicates that cyclic load flexural testing could be used reliably for determining the dynamic stiffness modulus of a lightly stabilized granular material. Correlations among the mechanical properties obtained from flexural testing are also presented.

An experimental investigation was conducted to study the development of self-consolidating rubberized concrete (SCRC) with improved flowability, passing ability, stability, and strength for multiple structural applications. The investigation particularly aimed to maximize the percentage of used crumb rubber (CR) in SCRC while minimizing the reduction in strength and stability of the developed mixtures. The experimental test parameters included CR percentage (0–50% by volume of sand), binder content ($500–550\mathrm{kg}/{\mathrm{m}}^3$), coarse aggregate size (10–20 mm), air entrainment, and supplementary cementing material (SCM) (fly ash, ground granulated blast-furnace slag, and metakaolin). The performance of the developed SCRC was evaluated based on the results for compressive strength, flowability, passing ability, high-range water-reducer admixture (HRWRA) demand, coarse aggregate segregation, and CR distribution. The results indicated that mixtures with $500\mathrm{kg}/{\mathrm{m}}^3$ binder content had acceptable strength, fresh properties, and stability with up to 15% CR replacement. Using $550\text{-}\mathrm{kg}/{\mathrm{m}}^3$ binder content improved SCRC mixture stability and allowed up to 20% CR to be used safely. Compared with the other tested SCMs, metakaolin (MK) significantly improved mixture viscosity and particle suspension/distribution, which allowed the use of up to 30% CR in SCRC mixtures. The results also showed that, despite the reduction in compressive strength in mixtures with entrained air, using air entrainment in SCRC with MK further improved the fresh properties of these mixtures and allowed up to 40% CR to be used with acceptable compressive strength (25.7 MPa) and with no sign of segregation.

This research focused on the study of the flexural load-deflection behavior of steel fiber reinforced rubberized concrete (SFRRC) up to the first-crack load. Specifically, this study used an experimental method to examine simultaneous flexural load-deflection response measurements on normal portland cement concrete (PCC), rubberized concrete (RC), steel fiber reinforced concrete (SFRC), SFRRC, and others. Other basic tests were utilized to characterize fresh mix and constituent material properties. Regression models were developed to predict the following: (1) first-net deflection; (2) net deflection at any applied load; and (3) first-crack load at different mix combinations of crumb rubber and steel fiber. Results from this investigation showed that the incorporation of crumb rubber imparts its elastic property to concrete; however, the additional gain in elasticity from the increased strength due to the incorporation of steel fiber as a second constituent played a more dominate role in improving this property.

This study investigates the effect of time-dependent mineralogical changes on the unconfined compressive strength (UCS) behavior of lime–ground granulated blast furnace slag (GGBS) treated naturally occurring acid sulfate soils (ASS) containing various proportions of pyrite. Pyrite (0, 2, 4% by weight), GGBS (5, 10, 15, 20% by weight), a fixed lime content of 15% by weight and curing periods up to 365 days were investigated. Mineralogical control on the strength of treated ASS samples was investigated using UCS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Quantitative phase analysis using XRD data and the Rietveld method was carried out to quantify mineralogical changes. Results show a decrease of UCS values after 180 days curing for ASS containing 4% by weight additional pyrite and treated with 20% by weight GGBS. XRD and SEM analyses suggest that a decline in the abundance of cementitious mineral phases coincides with possible formation of thaumasite-ettringite and the degradation of strength in treated ASS.

The viability of using two waste materials, water treatment sludge (WTS) and fly ash (FA), for developing sustainable masonry units has been previously investigated in terms of strength but the important aspect of durability against wetting–drying (w–d) cycles has yet to be studied. A study on durability against w–d cycles, an important parameter for service life design of the sustainable masonry units, is investigated in this paper. The liquid alkaline activator (L) was a mixture of sodium silicate (${\mathrm{Na}}_2{\mathrm{SiO}}_3$) and sodium hydroxide (NaOH), and a high calcium fly ash (FA) was used as a precursor. The results of cyclic w–d test indicate that the WTS–FA geopolymer manufactured with an optimum ingredient ($\mathrm{L}:\mathrm{FA}=1.6$, ${\mathrm{Na}}_2{\mathrm{SiO}}_3:\mathrm{NaOH}=90:10$) and at an optimum heat condition of 85°C for 72 h can be used as durable bearing masonry units; i.e., the compressive strength is greater than 12 MPa after 12 w–d cycles. For this optimum ingredient, the w–d cycle strength, $q_{u(w-d)}$ at heat temperatures between 65 and 95°C and durations between 24 and 120 h was found to be mainly dependent upon the initial soaked (without w–d cycle) strength $q_{u0}$, and the normalized strength $q_{u(w-d)}/q_{u0}$ versus number of w–d cycles relationship expresses as a logarithm function. This relationship facilitates a mix design to attain the required strength at a target service life, which is very useful for civil engineering practitioners and researchers alike. It is evident from this research that portland cement is not a suitable cementing agent to manufacture WTS masonry units because alum in WTS retards the cement hydration, unlike a geopolymer binder, which was proven to be suitable. Compared with a traditional clay–cement sample at the same initial soaked strength, the WTS–FA geopolymer sample exhibits higher durability. This indicates that the WTS–FA geopolymer masonry units have a longer service life than clay–cement masonry units, which is typically used in many countries. This research enables WTS traditionally destined for landfill to be used in a sustainable manner as an aggregate in geopolymer masonry units, which is significant from engineering, economical, and environmental perspectives.

The indoor and outdoor aging behaviors of a heat-reflective coating were studied regarding the problems derived from aging and reduced cooling effects. A one-year natural exposure test of the coating on a roof and on concrete samples was conducted, and a 28-day xenon lamp aging test on concrete and cylindrical samples was carried out. Surface appearance, infrared spectrum, cooling value, and reflectivity changes in different aging periods were analyzed. The results show that the amount of solar radiation is a key factor in aging. Aging can cause a gradual increase in carbonyl content and thus lead to a decrease in resin light transmittance, given that the carbonyl group absorbs visible light and infrared rays easily. This results in a reduction in reflectivity and cooling value. Reflectivity and cooling value show a linear relationship in the indoor and outdoor aging process. With respect to reflectivity and cooling value, solar radiation has a downward quadratic parabolic tendency whereas xenon lamp radiation maintains a linear relationship. By comparing the results of the indoor and outdoor aging tests, it can be concluded that aging for 32.0 days under accelerated conditions is equivalent to aging for one year under natural exposure conditions in the Chongqing area.

The Young’s modulus of concrete is an important mechanical parameter for assessing the stiffness of concrete structures. The objective of this paper is to present an analytical method for evaluating the Young’s modulus of concrete with spheroidal aggregates. In this method, the interfacial transition zone (ITZ) between aggregates and the bulk cement paste is treated as an independent phase. To reduce mathematical complexity, the three-phase concrete is decomposed into two two-phase composite materials and modeled through a two-step procedure. After the validity of the analytical method is verified with three sets of experimental data, a sensitivity analysis is conducted to quantify various factors that affect the Young’s modulus of concrete. The numerical results show that the Young’s modulus of concrete increases with the increase of the maximum size and aspect ratio of aggregate but decreases by increasing the ITZ thickness. It is also shown that the aggregate gradation influences the Young’s modulus of concrete to a certain extent.

Dilatancy behavior plays a key role in the rutting of asphalt mixtures; therefore, it is important to study its behavior to better predict and mitigate rutting of asphalt pavements. In this study, a partial triaxial compression test (PTCT) was developed and employed to characterize the dilatancy of asphalt mixtures. On the basis of the analysis of the principles and the testing method of the PTCT, the parameters of the specimen and the pedestals were determined using the finite-element method to ensure that the specimen could provide a similar confining pressure to that in an actual asphalt pavement. The diameters and heights of the pedestal and specimen were determined to be $50\times 30\mathrm{mm}$ and $100\times 80\mathrm{mm}$, respectively, by considering the aspect ratio of the specimen, actual pavement thickness, and numerical results. The test results were analyzed using the strain ratio and stress-dilatancy theories, considering the coupled effects of dilation gradient, distortional strain, and volumetric strain of the asphalt mixtures. It is shown that the degree of dilatancy changed with the strain ratio, which is sensitive to the air void content and loading rate. The stress-strain relationships of the asphalt mixtures indicate that dilation is related to the air void content and testing time. The asphalt mixtures contracted at the beginning of testing and then dilated after the peak stress, and the dilation increased continuously with increase of the axial strain. The specimen contracted when the dilation parameter $d$ ($d=1-\text{volumetric}\text{strain}\text{increment}/\text{axial}\text{strain}\text{increment}$) was less than 1.0 and dilated if $d$ was greater than 1.0. The dilation gradation was strongly correlated with the factors, including the stress-strain relationship, air void content, loading rate, and testing time. This study demonstrated that PTCT is a good and accurate test method to evaluate the dilation of asphalt mixtures.

Durability and recycling are two major concerns in the construction industry. Concrete carbonation may impair reinforced concrete durability as it favors the onset of reinforcement corrosion. The use of recycled aggregates, as a replacement for natural aggregates, in construction applications is a feasible way of recycling given materials from construction and demolition waste. The aim of this study is to quantify the contribution of potential conditioning factors to the carbonation rate of concrete incorporating recycled aggregates. For this purpose, a multiple linear regression technique was used, considering the mix design characteristics, environmental conditions, and recycled aggregates’ properties as explanatory variables, capable of predicting the coefficient of carbonation. The investigation was founded on ample experimental data, collated from several studies. This study proposes a general model, in which the carbonation in concrete depends on the 28-day compressive strength, clinker content, environment’s ${\mathrm{CO}}_2$ content, and aggregates’ equivalent water absorption. The models are statistically significant, with determination coefficients suggesting high correlation between the coefficients of accelerated carbonation of concrete in the experimental data and values predicted by the proposed models.

Fatigue phenomenon is one of the main distresses observed in pavements. It is therefore quite complex to characterize in the laboratory using traditional fatigue tests. This paper presents the results of an experimental fatigue campaign led on a cement treated mixture containing reclaimed asphalt material, which gives it viscous properties. Classical cyclic fatigue tension/compression tests on cylindrical samples are considered. Damage is characterized all over the test duration using complex modulus measurements in the axial loading direction (quasistatic method) and analysis of compression wave propagation in the radial direction (dynamic method). The results show that fatigue phenomenon is clearly observable using compression wave propagation. Moreover, correlations can be found between measurements that are performed by the two methods and for various axial stress levels.

To be able to accurately predict the static resistance function of laminated glass subjected to blast loads using engineering analysis methods, it is critical to evaluate the static behavior of the polymer interlayer before and after breakage of the glass layers. Therefore, the main objective of this research is to experimentally evaluate the constitutive behavior of polymeric glass interlayers under quasi-static loading. Constitutive relation of virgin and extracted polyvinyl butyral (PVB) and UVEKOL-S extracted from laminated glass panels were evaluated, including the energy absorption capabilities for each material. Also, the postbreakage behavior of laminated glass was investigated. The experimental results of scored tensile samples carried out on UVEKOL-S glass laminates using different numbers of scores are presented, discussed, and compared with the results of the PVB glass laminates. The energy absorption of the PVB glass interlayer was found to be larger than that of the UVEKOL-S interlayer. From the scored tensile tests, it was concluded that the adhesion of PVB to glass panes is stronger compared with the adhesion of UVEKOL-S to glass panes. Conversely, it was found that this stronger bond led to premature tearing of the PVB interlayer when compared with UVEKOL-S, which allowed relative slip, leading to reduced tearing initiation.

Earthen plastering mortars are becoming recognized as highly eco-efficient. The assessment of their technical properties needs to be standardized, but only a German standard exists for the moment. An extended experimental campaign was developed in order to assess multiple properties of a ready-mixed earth plastering mortar and also to increase scientific knowledge of the influence of test procedures on those properties. The experimental campaign showed that some aspects related to the equipment, type of samples, and sample preparation can be very important; although others seemed to have less influence on the results and the classification of mortars. It also showed that some complementary tests can easily be performed and considered together with the standardized ones, whereas others may need to be improved. The plaster satisfied the requirements of the existing German standard but, most importantly, it seemed adequate for application as rehabilitation plaster on historic and modern masonry buildings. Apart from their aesthetic aspect, the contribution of earthen plasters to eco-efficiency and, particularly, to hygrometric indoor comfort should be highlighted.

Autogenous healing is an already-present feature in strain-hardening cementitious materials, but it is an inferior mechanism because it can only heal small cracks in the presence of water. A cementitious material with synthetic microfibers and superabsorbent polymers (SAPs) could provide a solution. In this study, the ability of repeatable promoted autogenous healing in fiber-reinforced, strain-hardening cementitious materials with and without SAPs is investigated by comparing their mechanical properties after they are subjected to two cycles of loading under a four-point-bending test. The results indicate that SAP particles promote self-healing. The main mechanisms of the autogenous healing are the hydration of unhydrated cementitious materials in cracks and the precipitation of calcium carbonate on the crack faces. The healed specimens are able to regain some of their mechanical properties (up to 75%). Even second reloading of those healed samples leads to partial additional regain in mechanical properties (up to 66%).

This paper presents an experimental investigation on the performance of RC columns with corroded reinforcing steel bars. The corrosion of steel bars was induced by using a combined electrochemical process and wet-dry cycles. The corroded-RC columns were tested under eccentric-compressive loading, from which the residual strength of the columns was obtained. Relationships between the average cross-sectional area loss of the steel bar, the average and maximum crack widths of concrete cover, and the strength loss of the RC column were examined. Finally, a load-carrying capacity model is proposed to quantitatively estimate the residual compressive strength of the corroded-RC column.

Due to the increasing cost of asphalt binder and also due to environmental considerations, recycled asphalt shingles (RAS) are now allowed to be added into hot mix asphalt (HMA). RAS have been incorporated into HMA with the intent to achieve the potential benefits of cost-effectiveness and environmental sustainability without compromising the performance of the HMA. This study investigates the performance of HMA with and without RAS based on the evaluation of field cores drilled from four experimental pavement sections that were constructed in 2009 in King County of Washington State. The performance of the asphalt mixtures and the recovered asphalt binders are evaluated with respect to rutting, fatigue, and thermal cracking resistance via laboratory experiments. The test results show that the rutting resistance of the mixtures as well as the recovered binders is improved by the addition of RAS. However, the fatigue and thermal cracking resistance of the mixtures is not significantly affected by the addition of RAS. The field performance survey indicates excellent conditions for all test sections after three years of service.

This paper is devoted to the experimental study of chemical degradation effects on the mechanical behavior of sandstone. The sandstone samples were immersed in acid solutions with different pH values to undergo chemical degradation. Conventional triaxial compression tests with different confining pressures were performed on chemically degraded samples. It is found that the chemical degradation induced the diminution of elastic modulus and compression failure strength. Triaxial compression creep tests were then carried out with different stress levels. The experimental data showed that the creep deformation rate is enhanced by the chemical degradation.

Asphalt surface features revealed in the tapping-mode atomic force microscope (AFM) have been extensively studied. Most of the existing studies focus on the so-called bee-shaped surface feature, believed to be made of paraffin wax crystals. In the research reported in this paper, five asphalts of widely different aging states and asphaltenes obtained from two of these asphalts were examined by using an AFM in tapping mode. Two types of surface features were identified in all the specimens, as follows: (1) disk-shaped feature rising from the specimen surface, and (2) elliptical (and sometimes irregular) feature slightly recessed from the surface. In addition, a Strategic Highway Research Program (SHRP) asphalt (AAD) was used to study the morphology of asphaltenes in wax-free asphalt. The analysis of the topography and phase images of the microstructures revealed by AFM suggests that the disk-shaped and elliptical microstructures may contain asphaltenes. The morphology of asphaltenes from the asphalt extracted from a 36-year-old pavement appears to match the hypothetical so-called island molecular structure.

Coal combustion products (CCPs) are by-products created when coal is burned for energy production. These products include predominantly fly ash, bottom ash, and flue gas desulfurization (FGD) by-products. These materials can be a viable alternative to natural resources for the construction of engineered fills. Because of the variability in the chemical composition, CCPs require mineralogical, chemical, and mechanical characterization to ensure its applicability as a construction material. Furthermore, CCP characterization should also address the material’s changing properties with time. To date, only limited standards have been proposed to characterize these materials to determine the viability of their use as structural fill. The purpose of this study is to apply a minimal set of practical mechanical and chemical tests that will characterize and predict CCP time-based performance intended for large-volume civil engineering applications such as embankments and mine reclamation. Unconfined compressive strength tests, hydraulic conductivity measurements, and X-ray diffraction (XRD) analysis were performed at curing times from 1 to 180 days on three materials: fluidized bed combustion (FBC) ash, flue gas desulfurization (FGD) ash, and pulverized coal (PC) class F fly ash. Results show that the unconfined compressive strength varied between each of the materials and over time for both the FBC and PC fly ashes, whereas the strength of the FGD ash did not appear to change over time. The FBC ash experienced a significant strength gain with increased curing time. The XRD characterization shows that the strength gain in the FBC ash is likely caused by the formation of ettringite. The FBC ash also showed significant changes in hydraulic conductivity with curing time.

Computed tomography (CT) is a promising technique that is suitable to analyze core samples of already built structures or test the quality of geomaterials before use. The CT creates an image series of the examined object’s cross sections using an X-ray; hence, materials of different density could be separated on the slices. To analyze the images, corrections, e.g., for beam hardening or noise reduction, need to be implemented. This paper presents a method that can determine the presence of dense objects inside a composite material on the CT slices using fast Fourier transformation. The method was performed with good results on several samples from asphalt core samples taken from road pavements and concrete core samples.

This work investigates the mechanical behavior of cementitious composites (mortar) when quartz inclusions are totally or partially replaced with polyethylene terephthalate (PET) particles. A full factorial design is performed to identify the effect of the water/cement ratio and the range of quartz particles size used in the replacement on the different mechanical and physical parameters (bulk density, apparent porosity, water absorption, oxygen permeability, compressive strength, and modulus of elasticity). The results show a general reduction of the mechanical properties when the replacement with quartz particles is put in place. The composites made by replacing the coarse quartz particles showed acceptable mechanical properties for nonstructural civil engineering applications, with a significant amount of PET recycling to be used as aggregates for some specific end-user cases.