Journal of Materials in Civil Engineering

Material properties at elevated temperatures are important factors in the fire safety design and numerical analysis of cold-formed steel structures. Most of the previous research on material properties at high temperatures has adopted the steady-state test method. However, the transient-state test method is more realistic for actual fire conditions. This paper presents a detailed experimental investigation of Q345 cold-formed steel with a nominal yield strength of 345 MPa and a thickness of 1.5 mm under transient- and steady-state conditions. Both the flat and corner parts of Q345 cold-formed steel sections are considered. The results showed that the steady-state method was not equivalent to the transient-state method for Q345 steel; in addition, current standards provided overestimations for the mechanical properties of Q345 steel under elevated temperatures. An empirical equation was proposed to estimate the reduction factors for the yield and ultimate strength and the elastic modulus of Q345 steel under elevated temperatures, where the essential parameters were determined through fitting. The stress-strain relationship of Q345 steel under elevated temperatures was further developed based on the Ramberg-Osgood model, which compared well with the experimental results.

A two-stage viscoelastic-viscoplastic damage constitutive model is developed for describing different mechanical deformation response of asphalt mixtures under various loading conditions. The model decomposes total strain into viscoelastic and viscoplastic components with damage considered. The model is calibrated using the creep-recovery test for viscoelastic parameters and using the static triaxial creep test for viscoplastic parameters, respectively. The calibrated constitutive model is then validated using triaxial constant strain rate compression tests. The calculated volumetric deformation exhibits initial contraction caused by viscoelastic component of the model, followed by dilation caused by the viscoplastic damage component, which is consistent with the experimental phenomena. Results show that the model can reasonably represent the three-stage deformation of creep test as well as the hardening and softening stages of constant strain rate compression test.

This paper examines the use of ladle furnace steelmaking slag (LFS) as a material for the construction of embankments in civil works. It reports the chemical, mineralogical, and geotechnical properties of two soils, two LFS, and various mixtures thereof, in addition to their volumetric stability. The findings show that lengthy periods of time are required to achieve the potential expansion of LFS because of the hydration of certain aluminates and calcium oxide in addition to the slow hydrocarbonation reactions of magnesium oxide. The expansion test on the soil-LFS mixtures revealed slight swelling, attributable to the pozzolanic reactions of clay minerals with portlandite and brucite in addition to accommodation within the soil-slag pore structure. The cation exchange capacity of clay minerals affects the interaction between soil and LFS; minerals such as montmorillonite, with a high cation exchange capacity, improve the California bearing ratio and reduce the potential expansion. Not all soils are suitable for improvement with LFS because of the mineral compounds of their clay fraction.

This paper presents a simplified method of analysis and design for repair using bonded rigid plates of timber beams with localized damage. This method assesses the load-bearing capacity of the connection between plate and timber and proposes two failure modes: shear stresses at the bonding interface and in the timber piece. An experimental campaign was developed to verify the theoretical model, which in this paper is limited to the problem of bending moment transfer. Ten specimens of Pinus radiata D. Don were joined with bonded-in plates and 10 with laterally bonded ones, after which they were tested for bending. Two epoxy formulations were used as adhesive and glass fiber–reinforced plastic (GFRP) plates for reinforcements. Tests with different anchorage lengths were developed to establish a relationship with load-carrying capacity. For an anchorage length approximately longer than twice the depth of the plate, failure was not located at the connection. There was reasonable agreement between the theoretical and experimental results. The former were always on the safe side, and there was better agreement in the case of laterally bonded plates.

Ultrahigh performance concrete (UHPC) is increasingly making its way into the construction field. Characterization of UHPC has therefore received much-needed attention in the research arena. One effective application of UHPC is in combination with high-strength steel (HSS) reinforcing rebar in shallow beams or slabs. However, bond and development characteristics of HSS rebar in UHPC have not yet been investigated. This paper presents the experimental results of the pullout and flexure tests conducted with HSS rebar in UHPC. This work was a part of a larger project to develop a new light-weight UHPC-HSS bridge deck system for a moveable bridge. Because the bridge deck was designed with #10 and #22 rebar as the main reinforcement, only these two rebar sizes were used in the experiments. First, pullout specimens were tested with three different embedment lengths of 8, 10, and 12 times the rebar diameter. Then, from the results of pullout specimens, beam specimens were tested with embedment lengths of 10, 12, 14, and 48 times the rebar diameter for #10 rebar and 14, 16, 18, and 21 times the rebar diameter for #22 rebar. The size of the T-section beam specimens was derived from the size of the rib in the proposed deck system to simulate the actual conditions. The study showed that #10 and #22 rebar develop at embedment lengths of 12 and 18 times the rebar diameter, respectively. The paper also presents a comparison between experimental results and the development length recommendations of ACI 318-08, ACI 408R-03, and AASHTO, demonstrating that the ACI 408R-03 compares more favorably with the test data.

Phosphogypsum is added to building materials to accelerate fly ash pozzolanic reaction and contributes to early strength development of concrete. The release of unacceptable fluoride levels by phoshogypsum on contact with water is a major impediment in its usage to manufacture building products because excess fluoride consumption causes dental and skeletal fluorosis. This paper examines the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. Fly ash (FA), sand (S), lime (L), and phosphogypsum (G) (FA-S-L-G) slurries are cured for various periods, and the fluoride released by the mix is monitored as a function of time. A substantial reduction in fluoride release was observed and is attributed to entrapment of phosphogypsum particles in a cementious matrix formed by fly ash-lime pozzolanic reactions coupled with consumption of fluoride in formation of insoluble compounds. The compressive strength developed by compacted FA-S-L-G specimens with time was observed to be a three-stage process; maximum strength mobilization occurred during 14 and 28 days of curing at room temperature. Exposure of the compacted FA-S-L-G specimens to acidic and alkaline environments for 9 days did not impact their compressive strengths.

Bottom-up fatigue cracking is one of the major distresses for asphalt pavements. Accurate prediction of fatigue cracking for asphalt pavement is of paramount importance for a cost-effective pavement design. A fatigue model based on mechanistic-empirical pavement design is modified from an Asphalt Institute model. However, there are some controversies about the effectiveness of the mechanistic-empirical pavement design fatigue model. The major concern exists on the use of dynamic modulus as a key parameter and there is no damage property of asphaltic mix to predict fatigue, which is induced by damage to the material. This study developed a damage-based phenomenological fatigue model. The pavements at the Federal Highway Administration’s Accelerated Loading Facility (ALF) were used to test the effectiveness of existing models, including the mechanistic-empirical pavement design fatigue model, and validity of the damage-based fatigue model. The data used in this study included dynamic modulus, critical strain-energy density of hot-mix asphalt (HMA), tensile strain at the bottom of HMA layer, and the fatigue life of ALF pavements. It was found that the damage-based model significantly improved the accuracy of the prediction, when compared with the mechanistic-empirical pavement design fatigue model and other conventional models.

Geogrid (uniaxial or biaxial) is one type of geosynthetics that has been successfully used in slopes, walls, roads, and other applications. The main application of biaxial geogrid is to stabilize soft subgrade and reinforce weak base courses by providing lateral confinement. The confinement due to the interaction between aggregates and the ribs of biaxial geogrid depends on the geometry properties of the geogrid, such as rib shape and apertures size, the stiffness of the ribs, and the properties of aggregates. Research has shown that biaxial geogrid cannot provide uniform tensile resistance in all directions. To overcome this problem, a geogrid product with triangular apertures was developed and introduced into the market. Recent studies showed that the triangular aperture geogrid can provide nearly uniform tensile resistance in all directions and is more efficient in improving the performance of reinforced bases as compared with biaxial geogrid. However, the performance of triangular aperture geogrid-reinforced bases under dynamic loading and the influence of base course thickness on the confinement effect of triangular aperture geogrids have not been well evaluated. In this study, unreinforced and triangular aperture geogrid-reinforced bases at different thicknesses over a weak subgrade were constructed in a large geotechnical testing box ($2\times 2.2\times 2\mathrm{m}$) at the University of Kansas and tested under cyclic loading. During the tests, surface deformations and vertical stresses at the interface between the base and the subgrade were monitored. The test results indicated that triangular aperture geogrids reduced permanent deformation and maximum vertical stress at the interface as compared with the unreinforced bases. The geogrids improved the performance of the aggregate bases at different thicknesses. The benefit became more pronounced when a heavier-duty geogrid was used. The back-calculations from the test data showed that the stress distribution angle and the modulus ratio of base course to subgrade decreased with an increase of the load cycles. The stress distribution angle increased with the increase of the base thickness. The vertical stress distributions were compared with the computed distribution by the layered linear elastic theory. These test data provide the basis for the development of a design method for triangular aperture geogrid-reinforced bases over weak subgrade in the future.

The development of techniques capable of evaluating the deterioration of reinforced concrete structures is instrumental to the advancement of structural health monitoring (SHM) techniques and service life estimate methodologies for constructed facilities. One of the main causes of degradation is the corrosion of steel reinforcement. This process can be modeled phenomenologically, whereas laboratory tests aimed at studying durability responses are typically accelerated to provide usable results within a realistic period of time. Numerous nondestructive methods have been recently studied. Acoustic emission (AE) is emerging as a nondestructive tool to detect the onset and progression of deterioration mechanisms associated with concrete cracking. In this paper, an accelerated corrosion and continuous AE monitoring test setup is presented, providing relevant information on the characteristics of the corrosion circuit, continuous measurement procedure, selection of AE sensors, and AE parameter setting for data acquisition. The effectiveness of AE in detecting and characterizing the initiation of the corrosion process is discussed on the basis of results from small-scale, precracked RC specimens that are representative of areas near the clear cover in typical RC members. The main outcome is a new approach of AE data interpretation based on time-driven parameters.

The research considered here harmonized specifications for asphalt concrete and stone mastic asphalt of 21 central, northern, and southern European countries which adopted the wheel tracking test using a small device in air. An objective of the research was to reconsider these requirements by identifying a potential relationship with climatic conditions and traffic load. The empirical requirements predominantly included the proportional rut depth and, to a lesser extent, the wheel tracing slope. The southern European countries mostly did not adopt these requirements. On the other hand, the fundamental, performance-based, requirements considered stiffness, creep rate, and resistance to fatigue, but with a greater variety in terms of the test methods and conditions. There was a certain relationship between the requirements and the air temperature conditions as well as the traffic load identified. Furthermore, the strictness of the requirements regarding the resistance to permanent deformation decreases from south to north. However, conclusions regarding the fundamental requirements can be drawn only when more countries have adopted these specifications. Besides the need to adopt the performance-related requirements by the remaining countries considered, the test methods and conditions of the performance-based requirements need further harmonization to take a step toward the removal of technical barriers in the field of pavement construction across Europe.

In this research, a new type of phosphogypsum–sulfur polymer cement (PG-SPC) for use in the manufacture of building materials was obtained. Physicochemical, radiological characterization, and modeling of exhalation rates were carried out in phosphogypsum (PG) and PG-SPC samples. Because the PG is enriched in several natural radionucleides, a leaching study in PG-SPC was performed. The optimized ratio of elemental $\text{sulfur}/\text{phosphogypsum}=1:1.0$ and phosphogypsum dosage = 10–40% by weight was obtained. The result showed that the solidified materials present a highest strength (54–62 MPa) and low total porosity (2.8–6.8%). The activity concentration index ($I$) in the PG-SPC is lower than the reference values in most international regulations; therefore these new sulfur polymer cements can be used without radiological restrictions in the manufacture of building materials inside a standard room ($5\times 5\times 2{\mathrm{m}}^3$) with good ventilation. The leaching experiment demonstrated that the environmental impacts of the PG-SPC cements are negligible.

In this paper, a cost-benefit analysis is reported for selecting the most economical alternative among various pavement preservation choices using life-cycle cost analysis analytical technology. The impact of pavement conditions on the performance of the specific treatment was investigated in terms of pavement performance curves, which were developed for the treatments under varying pavement condition levels at each traffic network based on Pennsylvania Department of Transportation overall pavement index (OPI) data. A relationship between pavement life extension and pavement condition prior to the treatment was established. Finally, life-cycle cost analysis was conducted to quantify the impact of the pavement condition on the performance of the preservative treatments in terms of the benefit-to-cost ratio and net equivalent uniform annual cost. There is an optimum pavement condition and associated age (or a range of conditions or ages) in which the benefit-to-cost ratio that is associated with a treatment is maximized.

Low-temperature cracking is a significant distress in asphalt pavements built in the northern United States and Canada. As temperature decreases, thermal stresses develop in the restrained asphalt surface layer; and when the temperature reaches a critical temperature, cracking occurs. The current guides use thermal stress as a critical input parameter in the low-temperature performance model. In this paper, statistical and graphical analyses are performed to compare thermal stresses that develop in an idealized asphalt pavement calculated from mixture creep data obtained using indirect tensile test (IDT) and bending beam rheometer (BBR) test. In addition, the idea of obtaining thermal stresses from binder BBR creep data is further investigated. Thermal stresses calculated using IDT and BBR mixture creep data, respectively, are similar. Thermal stresses calculated from binder creep data are significantly different than thermal stresses calculated from mixture creep data. The effect of physical hardening is investigated for a limited number of materials, and the effect on thermal stresses is significant.

Resilient moduli of pavement layers are the basic input parameters for the design of pavements with multiple layers in the current mechanistic empirical pavement design guides. Field measurements are generally believed to provide accurate values to back-calculate pavement layer moduli, but the tests to measure the relevant parameters are expensive, difficult to perform, and cause disturbances to the public. Therefore, the back-calculation of pavement layer moduli from laboratory scale model testing has been a focus of recent pavement research. This paper presents a back-calculation analysis to evaluate pavement layer moduli by using a three-dimensional numerical model developed using the FLAC3D finite difference software. The pertinent measurements that are required for the back-calculation analysis were collected from a cyclic load testing facility under traffic type cyclic loading conditions, with a typical pavement structure consisting of a granular road base lightly stabilized with cement–fly ash over an expansive soft clay subgrade. This study indicates that the stabilized base material had cross-anisotropic resilient properties, with an average vertical resilient modulus of 2,875 MPa and an average horizontal resilient modulus of 1,598 MPa. From this investigation, the resilient moduli of the stabilized granular base layer and subgrade clay were reliably back-calculated from the analysis by using the FLAC3D numerical model.

A comprehensive laboratory evaluation of the geotechnical and geoenvironmental properties of five predominant types of construction and demolition (C&D) waste materials was undertaken in this research study. The C&D materials tested were recycled concrete aggregate (RCA), crushed brick (CB), waste rock (WR), reclaimed asphalt pavement (RAP), and fine recycled glass (FRG). The geotechnical assessment included particle size distribution, particle density, water absorption, compaction, Los Angeles abrasion, postcompaction sieve analysis, flakiness index, hydraulic conductivity and California bearing ratio (CBR) tests. Shear strength properties of the materials were studied through a series of triaxial tests. Consolidated drained triaxial tests undertaken on the recycled materials indicated that the recycled materials had a drained cohesion ranging from 41 kPa to 46 kPa and a drained friction angle ranging from 49° to 51°, with the exception of FRG and RAP. The response of the materials under repeated load was investigated using repeated load triaxial (RLT) tests. The RLT testing results indicated that RCA, WR, and CB performed satisfactorily at 98% maximum dry density and at a target moisture content of 70% of the optimum moisture content under modified compaction. The geoenvironmental assessment included pH value, organic content, total and leachate concentration of the material for a range of contaminant constituents. In terms of usage in pavement subbases, RCA and WR were found to have geotechnical engineering properties equivalent or superior to that of typical quarry granular subbase materials. CB at the lower target moisture contents of 70% of the OMC was also found to meet the requirements of typical quarry granular subbase materials. The properties of CB, RAP, and FRG, however, may be further enhanced with additives or mixed in blends with high quality aggregates to enable their usage in pavement subbases.

This paper presents an experimental study on the mechanical behavior of the argillite that was considered as a possible host rock for a high-level radioactive nuclear waste repository in France. A specific mechanical setup with optical observation was used to investigate the behavior of the material at both the macroscopic scale (cm) and the microscopic scale (100 μm). The full-field strain of the material during mechanical loading was obtained by use of the digital image correlation (DIC) technique. A series of uniaxial compression tests under monotonic and cyclic loading were performed on the Callovo-Oxfordian argillite samples to characterize the corresponding elastic and plastic properties. The results showed that the mechanical behavior (elastic modulus, Poisson’s ratio, and plasticity) depended on water content. The obtained strain-stress curve was nonlinear, and this nonlinearity was mainly related to plasticity and time-dependent effects of the material. The heterogeneous behavior related to the mineralogical composition and the damage induced by mechanical loading are also discussed.

Electrical properties are frequently measured in the concrete construction industry as a part of mixture qualification and quality-control testing. Whereas there are several factors that influence the electrical response of concrete, one of the most important factors is its degree of saturation. Although current standard tests rely on the concrete’s being saturated, this can be difficult to accomplish, is time-consuming, and can artificially increase the degree of hydration of the test sample in comparison with that of concrete in field structures (when the test samples are stored in water). Although some studies have measured the electrical response of concrete for samples with different moisture content (i.e., stored at different relative humidities), a single expression has not been proposed that predicts how drying changes the electrical response. This paper suggests that a saturation function should be considered as a possible method to account and to correct for less than complete saturation in concrete. This function would provide one term that accounts for changes in pore fluid volume, pore solution concentration, and pore fluid connectivity. Although preliminary, this approach has several potential benefits: (1) it could enable testing of partially saturated concrete, thus saving time; (2) it could be used to predict properties under different exposure conditions; (3) it may facilitate more comprehensive service-life models; and (4) it may enable a wider use of embedded sensor technology.

Since 2008, the Department of Infrastructure on the Isle of Man, located within the British Isles, has been investigating the use of polymer curb units in order to minimize workforce injury. With little current work detailing the experiences of early adopters of these new curb units, this work presents the findings from seven case studies on the Isle of Man. In addition, experimental testing is undertaken in order to determine the suitability of polymer curbs in a variety of real-world situations.

The cement industry is the major contributor of ${\mathrm{CO}}_2$ emission, which could be curtailed by the use of supplementary cementitious materials. Rice husk ash (RHA), one of the supplementary cementitious materials, exhibits high pozzolanic characteristics when properly produced under controlled conditions. In this paper, four concrete mixtures were considered to identify the effect of RHA (produced under controlled conditions) on performance characteristics of the concrete. RHA was added as partial replacement of ordinary portland cement from 10 to 30%. The properties investigated include compressive strength, chloride permeability, water absorption, and sorptivity of RHA-blended concrete. Based on the results, it was found that RHA addition up to 20% in partial replacement of ordinary portland cement lead to increased compressive strength of concrete compared with that of reference mixtures. However, the durability of RHA concrete was on the higher side for all doses compared with the reference mixtures. The compressive strength is well correlated with chloride permeability of RHA-blended concrete mixtures. Rice husk ash proves to be highly reactive pozzolan, which contributes to higher strength and improved performance characteristics.

One of the convenient approaches to decreasing moisture sensitivity in hot-mix asphalt (HMA) is coating the aggregate surface with a suitable agent. Hydrate lime (HL) is the most common antistrip additive used to treat aggregate properties in hot-mix asphalt. In this study, the effect of HL-treated aggregate on moisture sensitivity of HMA was evaluated by applying thermodynamic concepts and surface free energy (SFE) method. The SFE components of aggregates and asphalt binders were evaluated by using a universal sorption device (USD) and dynamic Wilhelmy plate method (DWPM), respectively. The results showed that the use of HL reduced the acid SFE and increased the base SFE of the two types of aggregates used in this study. These changes promote adhesion between asphalt binder and aggregate with and without water, particularly in the mixtures containing acidic aggregates prone to moisture damage. Covering the aggregate with HL decreased the total SFE of aggregate, leading to the increase in wetability of asphalt binder over the aggregate. Moreover, HL decreased the difference between surface free energies of asphalt-aggregate and water-aggregate, decreasing the detachment tendency of asphalt binder over the aggregates. Finally, the treatment of aggregate surface with HL reduced the difference between the free energy of adhesion of aggregate-asphalt binder in dry and wet conditions, decreasing the rate of moisture damage.

The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as an alternative to natural aggregates. It conserves natural resources and reduces the space required for landfill disposal. In this paper, strength characteristics of high-volume fly ash (FA)–based concrete with recycled aggregate of M50 grade were studied. The recycled aggregates were collected from a demolished structure 20 years of age. Natural aggregate (NA) was replaced with recycled aggregate (RA) in different percentages of 25, 50, and 100% to study the effect of recycled-aggregate concrete (RAC) on compressive and tensile strength characteristics. Similarly, the amount of cement was also replaced with fly ash in different percentages such as 40, 50, and 60% to study the effect of fly ash on compressive and tensile strength of concrete. The experiments were conducted for different ages of concrete such as 7, 14, 28, and 56 days. From the detailed investigations with 16 mix combinations, 50% replacement of cement with FA and 50% replacement of NA with RA give satisfactory results by compromising strength 40 to 50% with a major reduction in cost. Depending on the field requirements, a construction engineer can go for designing M50-grade concrete where M30-grade concrete is to be deployed for structural purpose with the previously said combination.

Cement-soil mixing is an effective ground improvement technique. The introduction of cement to soils can effectively increase their shear strength, but at the same time the mixture becomes brittle. To increase the ductility of the mixture, fiber can be added to the mixture. The current design criterion only requires the measurement of unconfined compressive strength without considering the effects of curing time and curing stress and the simplified design criterion does not reflect the field behavior of cement soil mixtures. A series of unconfined compression tests on cement- and cement-fiber-improved soft soils were conducted with special attention being paid to the combined effects of curing time and curing stress. It is found that the introduction of cement to soft soils can increase the unconfined compressive strength, which also increases with curing time and curing stress. The existence of fiber in the cement-soil mixture can significantly improve its ductility without changing the unconfined compressive strength too much. The stiffness of the mixture can be significantly increased when the mixture is cured under curing stress when compared with the mixture without curing stress.