Journal of Materials in Civil Engineering

The recent increased interest in “fingerprinting” or identifying commonly used construction materials such as asphalt binders is expected to continue in years to come. To capture the basic fingerprint of asphalt binders, spectroscopy devices can be handy and useful. In particular, this study evaluated the effects of two warm-mix asphalt (WMA) additives, Sasobit and aspha-min, on the chemical compositions of a performance grade binder (PG 64-22). Spectroscopy techniques including Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and X-ray photo electron spectroscopy (XPS) were used in this study. Mass precipitated asphaltenes and maltenes and straight-run asphalt binder samples were analyzed using these techniques, and test results were compared with the rheological data. The effectiveness of an antistripping agent (ASA), AD-here HP Plus, on a WMA-modified binder was also evaluated. Furthermore, the effects of aging on chemical compositions of the ASA-modified binder were evaluated. Spectroscopy analysis data from this study were in agreement with high-temperature performance data of the tested binders. The findings of this study are expected to help in fingerprinting WMA mixes.

This study evaluated the effect of postcompaction moisture variations on the resilient modulus ($M_R$), unconfined compressive strength (UCS), and modulus of elasticity ($E$) of cementitiously stabilized subgrade soils. Class C fly ash (CFA) and hydrated lime were used as the stabilizing agents. Specimens were compacted at optimum moisture content ($w_{\mathrm{opt}}$) with different percentages of stabilizers (i.e., 10% CFA and 6% lime) and then either dried or wetted to different moisture contents prior to testing for $M_R$, UCS, and $E$. Results showed that $M_R$, UCS, and $E$ values increased due to drying and decreased due to wetting. $M_R$-moisture, UCS-moisture, and E-moisture models were developed and proved to be useful in predicting the variations of $M_R$, UCS, and $E$ values of stabilized subgrade soils with moisture changes. These models can be used, in the new mechanistic-empirical pavement design approach (M-E PDG), to predict $M_R$, UCS, and $E$ values of stabilized subgrade soils with moisture variations.

A numerical method, with which experimental results were processed, was adopted to measure the total emissivity of mild steel specimens at high temperatures. This method is derived from considering the transient thermal energy equilibrium between a steel specimen and its surrounding heating environment. As a first step to validate this method, the results obtained at a low temperature were compared with those using infrared thermographic techniques, and a good correlation of 87% was achieved. The numerical model was then extended to high temperatures to investigate the variation of emissivity of steel with temperatures. The convective heat transfer coefficient used in the numerical model was examined in great detail using results obtained from transient high temperature tests. The emissivity of steel obtained from this study shows that steel emissivity varies over a range of temperatures and the variation becomes more abrupt between 400 and 500°C. Formulation for the emissivity of steel at rising temperatures is recommended for steel design in fire.

This paper presents the effect of temperature on the mechanical properties of high-strength alloy structural Q460 steel. The strength and stiffness properties of steel degrade with temperature and this deterioration has to be properly accounted for in the fire resistant design of steel structures. The strength and stiffness degradation is also influenced by the composition of steel. Because of a lack of data specific to high-strength Q460 steel, design standards assume the high temperature strength variation of Q460 steel to be same as that of conventional mild steel. To overcome this drawback, strength and stiffness properties of Q460 steel were measured at various temperatures in the range of 20–800°C. A relative comparison of measured data indicates that high-strength steel experiences a slower loss of strength and stiffness with temperature than conventional steel. Data generated from the experiments, namely, load-displacement relationships and vibration frequency, were utilized to develop relations for yield strength, tensile strength, and elastic modulus of Q460 steel as a function of temperature. The proposed relations developed specifically for high-strength Q460 steel can lead to better fire resistance prediction of steel structure systems.

One of the main obstacles to a wider use of self-compacting concrete (SCC) is its sensitivity to small variations of the constituent materials, mix proportions, and other external factors. The main objective of this paper is to illustrate how to evaluate and compare the robustness of SCC mixtures optimized according to various economic criteria while maintaining the water/cement ratio and fresh state target properties. The optimization is derived from numerical models, and a central composite design is developed to mathematically model the influence of mixture parameters and their coupled effects on deformability, passing and filling abilities, and compressive strength. The strategies to increase the robustness of SCC mixtures and the existing methodologies to assess it are presented and discussed. By applying these methodologies, it is shown that robustness can be enhanced by changing only the proportions of materials in mixtures. Minimizing the superplasticizer dosage and, consequently, increasing the paste volume (by means of a higher limestone filler content) to keep adequate fresh properties is found to be the most effective optimization criteria to enhance the robustness of SCC mixtures.

A controlled-strain repeated direction tension (RDT) test is useful for characterizing asphalt mixtures and assessing fatigue cracking accompanied by plastic deformation. The strain curve in a loading cycle of the controlled-strain RDT test is a standard haversine wave with only a tensile portion, whereas the stress curve has a tensile portion and a compressive portion (quasi-compression) because of the viscoelastoplastic nature of the asphalt mixture. Usually the material properties in the tensile stress portion (the tensile properties) are used, while those in the compressive stress portion (the quasi-compressive properties) are neglected. This leads to nonnegligible errors in estimating the dissipated strain energy (DSE) and characterizing the damage (such as cracking and permanent deformation) generated in the material. The objective of this paper is to obtain complete material properties and accurate amounts of dissipation and storage of energy of this test method as the foundation of damage characterization. This paper provides methods to simulate the stress and strain for the tensile and compressive stress portions separately so as to determine the tensile and quasi-compressive properties, respectively. The difference between the tensile and quasi-compressive properties is investigated using statistical analysis. It is found that the tensile properties of an asphalt mixture are different from the quasi-compressive properties due to the crack opening and closure within each loading cycle. The DSE calculated using both the tensile and quasi-compressive properties is larger compared to the traditional method using only the tensile properties, indicating an underestimation of the damage by the traditional method. In addition, the recoverable strain energy (RSE) is investigated to examine the ability of an asphalt mixture to store and recover energy. A new perspective in terms of the integration method is provided to determine the actual amount of the RSE in a loading cycle.

Fatigue cracking and permanent deformation develop simultaneously in asphalt mixtures under repeated destructive loading regardless of temperature. Because these two distinctively different damage mechanisms always occur together, it is not possible to obtain pure cracking damage or pure permanent deformation damage in any asphalt mixture by varying the temperature or loading level. This paper develops an energy-based method to separate fatigue cracking from permanent deformation in terms of energy consumption. Specifically, the dissipated pseudostrain energy (DPSE) expended on cracking is separated from that expended on permanent deformation. Controlled-strain repeated direct tension (RDT) tests are performed on asphalt mixture specimens to determine their nondestructive properties, critical nonlinear viscoelastic properties, and destructive properties. The total DPSE, which is the amount of energy dissipated for the fatigue damage, including both fatigue cracking and permanent deformation, is calculated based on the critical nonlinear viscoelastic properties in order to separate both linear and nonlinear viscoelastic effects from the strain energy that is available to cause damage. The energy distribution in an asphalt mixture under destructive loading is investigated at the microscopic level. Balance equations are established between the true stress/strain/energy of the intact material and the apparent stress/strain/energy of the bulk specimen. These balance equations are utilized to completely formulate the DPSE for cracking and the DPSE for permanent deformation, respectively. As a result, the DPSE for cracking is separated from the DPSE for permanent deformation. The formulations of the two types of DPSE and the RDT data will be used to calculate the amount of each type of DPSE. The DPSE for cracking will be used to predict the crack growth, average crack size, and number of cracks in the asphalt mixture under repeated destructive loading. The DPSE for permanent deformation will also be used to predict the growth of permanent deformation. This will be introduced in following papers. This paper is one of a series of companion papers that characterize nondestructive and destructive behaviors of an asphalt mixture under tensile loading.

It has been found that aggregates used in paving asphalt mixtures absorb the asphalt binder into the porous structure of the aggregates. National test methods are available to measure the aggregate absorption. However, most research and measurements on aggregate absorption are limited to the accessible voids at the aggregate surface. This paper presents recent findings on the selective absorption of asphalt binder by aggregate particles in asphalt mixtures. The selective absorption of the binder is visualized on the aggregate surface under natural light and ultraviolet light. Rings with different colors are identified on the cross sections of the aggregates in both hot-mix asphalt and warm-mix asphalt, which indicates different asphalt components at different radial distances from the center of the aggregates. The asphalt components penetrating into aggregates are verified using the laser desorption ionization–ion mobility–mass spectrometer. A significantly higher concentration of asphalt components is identified at the edge of the limestone sample than in its center after it is soaked in a PG 58-28 asphalt binder (labeled AAD) for 32 h. Creep tests are also conducted on fresh limestone samples and limestone samples soaked in the AAD binder. The fresh limestone sample behaves elastically and is approximately twice as stiff as the sample soaked in the binder, which exhibits nonnegligible viscoelastic properties in the creep test.

Environmental factors directly affect a building’s performance and durability. They are particularly detrimental in the case of building envelope materials and systems because these tend to exhibit a large exposed area and relatively narrow thickness. Therefore, tools are needed to model degradation and provide an insight into its occurrence and its relationship with the environmental factors that have the worst effect. In this paper, the degradation of stone wall cladding directly adhered to the substrate is estimated based on the evaluation of the characteristics of 140 wall cladding systems inspected in Lisbon, Portugal. Because it is a complex phenomenon, a probabilistic analysis is developed using multinomial logistic regression. The analysis focuses on the environmental factors that most influence the overall degradation of the façades (condition level). Probabilistic patterns are thus obtained for the evolution over time of each condition level according to their exposure level to outdoor environmental conditions.

The aim of this paper is to present a proposal for the recycling of construction and demolition waste (CDW) at construction sites and the use of recycled sand in bedding mortar. Three samples of CDW were collected at construction sites from the city of Recife, Brazil and milled in a hammer mill. The following properties of the recycled sands were analyzed: water absorption, material finer than 75 μm, bulk density, fineness modulus, and the presence of contaminants. Mortars were produced with different amounts of cement and replaced the natural material by recycled aggregate in proportions of 50, 75 and 100%. These mortars were characterized for compressive strength, fresh mortar density, and consistence. Masonry prisms with three ceramic blocks were produced for analyzing the bending and shear strength. Several correlations between the properties of aggregates, mortar, and prisms were obtained, leading the authors to propose a recycling process, dosage, and quality control methodology for bedding mortars prepared with recycled sand at construction sites.

This paper investigates the effects of fineness and replacement of fly ash on the fresh and hardened properties of recycled aggregate concrete. Two groups of recycled aggregate concretes were studied and compared with that of conventional concrete (CON) in which crushed limestone and local river sand were used as aggregates. The first group was prepared using 100% coarse recycled concrete aggregate and local river sand. For the second group, crushed limestone and local river sand were fully replaced by both coarse and fine recycled concrete aggregates. The results indicate that the slump loss of the recycled aggregate concrete with fly ash was reduced to lower than that of the recycled aggregate concrete without fly ash when the fineness of the fly ash was increased, which increased the slump loss of the fresh concrete. Fly ash can be used to increase the compressive strength of recycled aggregate concrete, depending on its fineness and the degree of fly ash replacement. The addition of fly ash with different fineness in recycled aggregate concrete had no significant effect on the splitting tensile strength and the modulus of elasticity of the recycled aggregate concrete, which are related to its compressive strength.

A method has been developed using gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), for examining extracted material from fine aggregate to identify asphalt contamination within the fine aggregate. This method development was initiated after the authors’ research group was contacted by a major contractor who voiced concern regarding potential asphalt contamination of fine aggregates. The problem with fine aggregate contamination concerns alteration of optimum asphalt content and the resulting change in asphalt performance grade. Contamination is brought about because of the presence of small amounts of asphalt cement that are undetectable by the unaided eye. This study evaluated two sands of known origin that were contaminated with PG64-22 asphalt and one additionally contaminated with PG82-22 asphalt, all at very low percentages. A traditional method of asphalt content testing, the AASHTO ignition oven method, was compared with the newly developed method. For GPC sampling, Soxhlet extraction was performed on fine aggregates using the asphalt solvent tetrahydrofuran (THF). The recovered material was then injected in solution into the GPC for evaluation. The GPC method yields convincing evidence of asphalt contamination and a more accurate estimation of percent asphalt contamination within fine aggregates.

In this study, the performances of bitumen and asphalt mixtures modified by crumb rubber (CR) were compared with those modified by styrene-butadiene-styrene (SBS). The resultant mixtures were evaluated for their rheological and mechanical performances by different experimental techniques such as rheological bitumen tests, i.e., dynamic shear rheometer (DSR), bending beam rheometer (BBR), and hot mixture performance tests, that is, indirect tensile stiffness modulus, fatigue, semicircular bending, and toughness index. Experimental studies show that it is necessary to use twice as much CR as SBS to reach the same performance attained by SBS. CR modification at high additive content exhibits higher elastic response, i.e., recoverable strain, than the SBS-modified mixture. While the resistance to crack initiation of CR-modified mixtures increases with increasing additive content, the resistance to crack propagation decreases dramatically according to fatigue and semicircular bending tests.

For construction of roads and highways, a large amount of aggregate usage is needed. Because the natural aggregate resources are limited, the demand for the use of alternative aggregates has increased. For this reason, borogypsum in Turkey was used as a mineral filler aggregate in hot-mix asphalt concrete. When this is directly released to nature as boron waste, it may cause various environmental problems. In order to prevent this waste’s harmful effects to the environment, the use of borogypsum as an alternative aggregate in highway engineering may be effective. For this purpose, the physical properties of borogypsum were investigated by thermogravimetry differential thermal analysis (TG-DTA), x-ray diffraction (XRD), and scanning electron microscope energy dispersion analysis of x-ray (SEM-EDAX). Also, the surface properties of borogypsum were identified by polarized optical microscope (POM). In this study, two groups of hot-mix asphalt concrete were obtained. For the first group, asphalt concrete was produced with limestone aggregate, and for the second one, borogypsum was used as mineral filler in asphalt concrete. In both groups, limestone was used as fine and coarse aggregate. Marshall stability and other mechanical properties were determined. It is believed that the evaluated borogypsum has a similar crystal structure with tincalconite and its usage for hot-mix climate regions may be effective to reduce problems. Also, another crucial finding is that using borogypsum as a mineral filler aggregate in asphalt concrete can be convenient for the binder course of pavements exposed to heavy traffic potential.

An innovative experimental procedure is described that is used as a preliminary design stage for the pre-qualification of strengthening mortars applied to historical masonry buildings. In the analysis of the behavior of masonry structures and their constituent materials, increasing importance has been assumed by the study of the long-term evolution of deformation and mechanical characteristics, which may be affected by both loading and environmental conditions. Through static and fatigue tests conducted in the laboratory on different dimensional reinforced masonry specimens, it has been possible to investigate the durability of strengthening materials. This methodology is useful to select, from a range of alternatives, the most suitable strengthening mortar for historical masonry, and to avoid the errors associated with materials that are not mechanically compatible. Special attention was devoted to fatigue and thermo-hygrometric aspects, the effects of which on masonry are often significant enough to hinder the validity of repair works. The experimental procedure has been effectively used in the biggest restoration building site in Europe, the Royal Palace of Venaria.

This research investigated the effect of aggregate gradation on the performance of porous asphalt mixtures. Ten aggregate gradations, which represent typical gradations used by 20 different United States highway agencies for open graded friction courses, were compared by evaluating draindown, permeability, Cantabro abrasion loss, indirect tensile strength, and rutting resistance. The results indicated that gradation does influence the performance of porous asphalt mixtures. An increase in the void ratio of the aggregate structure contributes to significant increases in porosity and permeability. Consequently, the indirect tensile strength and durability (as measured by the Cantabro abrasion test) generally decreased as the mixture porosity increased. The 10 mixes showed good moisture resistance characteristics and most of the mixes had no significant difference in tensile strength after the moisture-conditioning procedure. Furthermore, the effects of rutting did not correlate with mixture or aggregate porosity. Based on these results, it is evident that an aggregate gradation for a porous asphalt mixture can be optimized depending upon the performance requirements (permeability or strength) based on the void ratio of the gradation.

This paper presents a novel procedure to determine the apparent activation energy ($E_a$) of concrete by temperature-matched curing (TMC) and a mathematical approach in which a TMC system is designed and finite-element software is used. The mathematical approach is adopted to analyze $E_a$ energy by minimizing the difference between the predicted values and measured data from testing samples cured under TMC conditions. Two methods are proposed to select the best-fit value of $E_a$ ($E_a-1$ for specified age $i$ and $E_a-2$ for testing ages ranging from the first testing age to age $i$). The results show that the value of $E_a$ is strongly age-dependent and nonlinear. $E_a-1$ decreases remarkably after a critical age, whereas $E_a-2$ varies smoothly with age. The value of $E_a$ is related to the temperature history. The procedure to determine $E_a$ presented in this paper fully takes into account the temperature effects on cementitious materials, and practicality and accuracy are greatly improved.

A survey of current literature has revealed that the testing protocol for determining the time of setting of fly ash–soil mixtures is not available. Although the current ASTM standard recommends using the Vicat needle method with a water-to-fly ash weight ratio of 0.35, it was originally proposed for testing the time of setting of cement. The current study showed that the Vicat needle method yielded poor test results for some common fly ashes. Moreover, the water-to-fly ash weight ratio of 0.35 may not be appropriate for some fly ashes because the chemical components are varied in different fly ashes. Therefore, a British fall cone was adopted to determine the time of setting of fly ash paste and fly ash–soil mixtures. It suggests that the best starting water-to-fly ash weight ratio should be at its liquid limit. As the water content increases, the initial and final times of setting of fly ash paste increase accordingly. For the fly ash–soil mixture, the initial and final times of setting decrease as the ash-to-soil weight ratio increases. Finally, a linear correlation was established based upon the water content, ash-to-soil weight ratio, and the ratio of calcium oxide to silicon dioxide present in the fly ash.