Journal of Materials in Civil Engineering

This study deals with the analysis of hole damage in the drilling of reactive powder concrete (RPC). Attention was first focused on the definition of an original approach on the basis of digital image processing (DIP) to quantify the extent of the damage. Then, an experimental approach, on the basis of the design of experiments (DoE), was performed to evaluate the influence of drilling operational parameters (namely, cutting speed, feed, and hole diameter) on the thrust force, torque, and RPC hole accuracy. The extent of hole damage was found to be influenced by the settings of feed and hole diameter, with cutting speed playing a minor role. Tool vibrations and troublesome centering procedures of the tools during drilling further complicated the interpretation of the hole damage.

Tests reported in this paper show that alkali-activated slag paste (AASP) can totally disintegrate when exposed to oven drying at 40–50°C with circulating air. This phenomenon has not been previously reported in the literature. Further tests eliminated two possible reasons for the disintegration: (1) carbonation of calcium-silicate-hydrate (C-S-H) gel leading to loss of strength and (2) differential shrinkage and cracking leading to disintegration of the samples. Thermal gravimetric analysis (TGA) confirmed that maximum mass loss of about 18% occurred at approximately 40°C. It is postulated that the mass loss is attributed to the loss of chemically-bound water resulting from the disintegration of C-S-H gel and strength loss. This conclusion is arrived in this paper by the process of elimination. Disintegration of AASP at this relatively low temperature is a serious issue and warrants further research on exact cause and possible remedies.

The extent of modification of the hydration process in a cementitious material by external agents depends on its mix components. In this study, the effect of D-galacturonic acid on the hydration of fiber-reinforced engineered cementitious composites (ECC) and ordinary mortar was investigated. The final setting time was monitored as well as the flexural or compressive strengths during and after 28 days of curing. It was observed that D-galacturonic acid retarded the setting of both materials, and the presence of D-galacturonic acid in the curing water slightly modified their strength attainment. However, in both cases, the extent of the retardation or modification was more severe for the ordinary mortar than the ECC. Moreover, the acid had an insignificant effect on the strength of either hardened ECC or mortar after 28 days of water curing. Therefore, the hydration and resulting modification of ECC by D-galacturonic acid was more tenacious than that of ordinary mortar

There is increasing interest in developing relatively quick test procedures to evaluate the effectiveness of composite coatings to reduce the infiltration of water and salt solutions into concrete structures to rapidly rehabilitate and extend the service life of reinforced concrete structures. In this study, concrete was first treated with two different types of silanes and then coated with a latex-based coating to investigate the sensitivity of the test procedure to resist the diffusion of water and 15% NaCl salt solution into concrete at room temperature. The concrete used in this study had a compressive strength of 36.5 MPa, with about 1.6% water absorption capacity in 21 days. The performance of concrete with composite coatings was investigated by using the immersion test, followed by the drying test. On the basis of 21 days of immersion test in water, the weight increase in specimens coated with one type of silane and latex coating was 1.21%, which was half of what was observed with the other silane and latex coating. Similar trends were observed with 15% salt solution, and hence, the test method adopted in this study was sensitive in selecting the composite coating. A new thin-film model was developed to predict the weight change of coated concrete cylinders during the drying phase. Finite-element (FE) modeling of the weight-change phenomenon showed that the initial rate and total weight change after 21 days of immersion testing was governed by the effective mass transfer coefficient, thickness, and a saturation parameter of the composite coating.

Owing to its importance to the structural analysis and design of cement-based materials, it is essential to determine Young’s modulus of concrete. This paper presents a numerical method for predicting Young’s modulus of concrete with aggregate shape effect. In the numerical method, aggregate particles are assumed to be elliptical and distributed within a rectangular concrete element with periodic boundary conditions by introducing an overlap criterion for two elliptical aggregate particles. The method modifies the lattice model to take account of the mechanical properties of each phase constituent of concrete in the analysis of stress. After the validity of the developed numerical method is verified with three independent sets of experimental results, the effects of the maximum aggregate diameter, aggregate gradation, interfacial transition zone (ITZ) thickness, and aggregate shape on Young’s modulus of concrete are evaluated in a quantitative manner. It is found that Young’s modulus of concrete increases with the increase of the maximum aggregate diameter and aggregate aspect ratio but decreases by increasing the ITZ thickness. It is also found that the aggregate gradation has a significant influence on Young’s modulus of concrete. The paper concludes that the numerical method developed in the paper can predict Young’s modulus of concrete with an average relative error smaller than 7%.

The present study examined the potential of pumice waste of the Isparta-Gelincik region, which has been categorized under the lightweight aggregate class as a stabilizing additive to problematic clayey subgrade of pavements. The physical properties of lightweight aggregate material were analyzed. In earlier research, few experiments have been carried out by using experimental samples to test for properties such as stability when frozen, solidity, strength, Atterberg limits, California bearing ratio (CBR), and dynamic repeated load triaxial (RLT) tests. The utilization of Gelincik pumice waste as a stabilizer was determined for the clayey subgrade. Pumice waste of the Isparta-Gelincik region and high plasticity clay were mixed in varying proportions to improve the engineering properties of the clayey soil. The CBR experiment was also performed to observe the change of strength through the use of waste material. In addition, RLT testing was performed by using mixed materials to observe the changes in the resilient moduli values of the mixtures. The results of the experimental research showed that Gelincik pumice waste can be used as a stabilizer for problematic clayey subgrades when constructing roads. This research is the first example of a stabilization approach for problematic clayey subgrade of pavements by using pumice waste.

This paper reports on the development of a dosage methodology based of compressive strength for artificially cemented fiber-reinforced soils. The controlling parameters evaluated were the fiber content ($F$), volumetric cement content ($C_{\mathrm{iv}}$), porosity ($\eta$), and cement/porosity ratio ($C_{\mathrm{iv}}/\eta$). To evaluate the influence of each parameter on the soil response, a number of unconfined compression tests were carried out. The results show that fiber insertion in the cemented soil, for all dry unit weights and for the whole range of cement dosages studied, causes an increase in unconfined compressive strength. The unconfined compressive strength ($q_u$) increased linearly with the amount of cement ($C_{\mathrm{iv}}$) for both the fiber-reinforced and nonreinforced specimens. It was also shown that the cement/porosity ratio, in which volumetric cementitious material content is adjusted by an exponent (0.28 for all the fiber-reinforced and nonreinforced cemented soil mixtures) to give unique correlations for each mixture, is a good parameter for the evaluation of the unconfined compressive strength of the fiber-reinforced and nonreinforced cemented soil studied. Finally, a unique dosage relationship can be achieved linking the unconfined compressive strength of the sandy soil studied with fiber content ($F$) and adjusted cement/porosity ratio ($C_{\mathrm{iv}}/\eta$).

The use of externally bonded fiber-reinforced polymer (FRP) laminates is an effective solution to increase the strength and deformability of reinforced concrete columns. A critical parameter in predicting the ultimate strength of FRP-confined concrete is the ultimate circumferential (i.e., hoop) strain. This paper presents the development of a novel test method aimed at providing reliable experimental measurements of the ultimate hoop strain in FRP circular jackets with different laminate thickness and diameter. The proposed approach simulates the lateral expansion of concrete columns subjected to axial loads by enlisting the property of water (which expands when it changes state of matter from liquid to solid) as a medium to apply an internal hydrostatic pressure on cylindrical glass FRP (GFRP) jacket specimens. The average ultimate hoop strain results from 54 cylindrical GFRP-jacket specimens with different diameter and laminate thickness clearly indicate a lower level of strain than those found in similar flat coupon specimens. These results indicate that the test method is safe, user-friendly, and generates reliable measurements of the hoop strain in GFRP circular laminates in a more representative fashion than direct tensile tests.

The primary purposes of this paper are to develop a method of quantifying the precision and bias in repeated simple shear test at constant height (RSST-CH) laboratory test results for different-sized specimens and to determine the effects of this precision and bias on predicted rutting performance. The effect of RSST-CH variability was quantified by using a statistical sampling method called bootstrapping. The contribution of test variability to variability in predicted in situ rutting performance was determined by performing Monte Carlo simulations that used a shear-based incremental-recursive rutting analysis model. Results indicated that significant bias exists between the predicted rut depths of different specimen sizes. Increasing the specimen size decreased the test variability. Specimen size requirements for two different mix types are proposed on the basis of the analysis. The effect of test temperature on test results variability was also determined. In addition, analyzing various rutting performance parameters was used to determine the parameter that contained minimum size-related bias. Permanent shear strain at 5,000 repetitions appears to be an unbiased rutting performance evaluation parameter, when compared with other parameters, because it is not significantly affected by specimen size-related bias when three or more replicate tests are conducted. Analyses were performed by using RSST-CH results and a specific rutting model; however, the general procedure can be used to identify specimen size-related bias and precision for any type of laboratory test and distress model.

The Arrhenius equation is often used to characterize the progress of portland cement hydration for predicting in-place concrete temperature, strength, and other properties. To apply the Arrhenius equation, an activation energy ($E_a$) value representing the temperature sensitivity of the hydration reactions must be determined. The effects of concrete mixture variables on activation energy, including the effects of chemical admixtures, have not been well researched. This paper examines the effects of set-accelerating, water-reducing/set-retarding, and air-entraining admixtures on apparent (i.e., experimentally determined) activation energy for mixtures with and without supplementary cementitious materials. It was found that a glucose-based water-reducing retarder and two high-range water-reducing admixtures slightly lowered $E_a$, a lignosulfonate-based water-reducing retarder and a calcium nitrate–based set-accelerating admixture significantly lowered $E_a$, and a vinsol resin air-entraining agent had no effect.

Infrastructure materials are essential components of the nation’s infrastructure and transportation systems. Deteriorating infrastructures require the development of computational tools to predict fracture behavior. The extended-finite-element method (XFEM) has been recently developed to eliminate remesh efforts by allowing crack propagation within continuous elements. The object of this study is to employ XFEM and image analysis techniques to numerically investigate fracture behavior within infrastructure materials. The XFEM was addressed with a discontinuous crack and inclusion enrichment function with the level-set method. The crack growth and stress intensity factors were also formulated. An extended-finite-element fracture model (XFE-FM) was developed with the MATLAB program for predicting fracture behavior with single-edge-notched beam (SEB) and split tensile (ST) tests. The developed XFE-FM was first validated with SEB testing on a homogeneous sample. In order to capture the real material microstructure, the digital samples of asphalt concrete and concrete specimens were generated with imaging processing and ellipse-fitting techniques. The predicted crack propagation with XFE-FM simulation on digital samples was compared with the fracture pattern of lab-tested specimens. The comparison results on open-mode middle-notched and mixed-mode offset-notched SEB and ST tests indicate that the developed XFE-FM has the ability to accurately predict fracture behavior within heterogeneous infrastructure materials.

There has been an increasing awareness of the role of zero shear viscosity (ZSV) of bituminous binders as performance indicators of resistance to permanent deformation of asphalt mixtures because in some cases the conventional criteria for binders do not get reflected in asphalt pavement rutting performance. The aim of this paper is to analyze the zero shear viscosities of bitumen and bitumen-filler mastics with three different levels of limestone filler concentrations on the basis of two viscosity measurement techniques by using a dynamic shear rheometer (DSR). The empirical Cox-Merz rule is used to examine the viscosity correlation between dynamic oscillatory and rotational viscometry measurements. The straight-run $40/60$ penetration grade bitumen and limestone bitumen-filler mastics containing low (15%) and intermediate (35%) filler content by mass obey the Cox-Merz rule, whereas the high filler content (65%) mastic shows a divergence in two types of viscosity measurements. The ZSVs of the bitumen and bitumen-filler mastics at 40°C and 60°C are determined by estimating from the two types of viscosity measurements at zero shear conditions on the basis of the Cross model calculation. In the ZSV stiffening ratios, the 65% limestone bitumen-filler mastic shows a considerable increase in stiffening effect compared with both the base bitumen and the other two mastics. With regard to the comparison with the rutting indicators, a significantly greater ZSV stiffening ratio shows that the two conventional rutting criteria $G^{*}$ at 0.4 Hz and $G^{*}/\sin \delta$ at 1.6 Hz are underestimated.

Asphalt binder has thixotropic characteristics that significantly affect its overall performance, but specifically fatigue performance, healing performance, and high temperature performance. Therefore, a clear understanding of the thixotropy of asphalt binder, together with proper modeling, is useful in researching the performance of the material. However, research in this area is still in the early stages of investigation. For the study reported in this paper, the thixotropy of four types of asphalt binder is examined by using various methods to establish corresponding thixotropy models. The results show that the exponential thixotropy model, the extended exponential function, and the structural kinetic model can be established by using different methods, and they all reflect the thixotropy of asphalt binder to some extent.

The dynamic modulus test is conducted based on the assumption that no damage is induced during the testing process and that measurements are conducted within the linear viscoelastic region. In addition, the level of damage that occurs in the flow number test has not been quantified. The objectives of this study are to quantify the levels of damage in the dynamic complex modulus and flow number tests by using X-ray computed tomography (CT) and to characterize the microstructural properties of asphalt mixtures under loading. Four Superpave mixtures, including one conventional hot-mix asphalt (HMA) and three warm-mix asphalt (WMA) mixes, were evaluated. Two WMA processes (i.e., water foaming and Rediset additive) were used in the preparation of the WMA mixes. In addition, reclaimed asphalt pavement (RAP) was used in the preparation of the mixes at a content ranging from 15–30%. Results of the experimental program indicated that the damage incurred in the dynamic modulus test is minimal and homogeneous, but the damage incurred in the flow number test is significant and heterogeneous. In addition, specimen preparation may significantly influence the three-dimensional air voids distribution in HMA.

The inclusion of elastomeric substances into concrete aimed at improving performance properties may pose a serious threat, particularly at high temperatures. This paper presents experimental findings regarding the elastomeric influence of natural rubber latex on compressive strength of concrete at elevated temperatures. Normal and modified concrete specimens were prepared, heated, and subsequently tested for compressive strength. Five temperatures—ambient temperature (27°C), 150, 300, 500, and 800°C—were applied. Microstructural samples were observed through scanning electron microscopy (SEM), and the role of poly(1,4-isoprene) particles in the modified system was evaluated using thermogravimetric analysis (TGA) conducted on hardened cement paste, latex film, and cement-latex blend. Finally, compressive strength of the modified concrete was observed to depreciate at the softening point temperature of the latex films in the comatrix, eventually with more strength loss. At 800°C, the strength loss was 50.5% in the modified concrete versus 37.8% in the normal concrete. Thus, special precautionary design measures may be necessary for latex-modified concrete, particularly in situations where the concrete is likely to face temperatures above the softening point temperature of the modifier.

An artificial neural network (ANN) model was developed to predict the rheological properties of oil well cement slurries. The slurries were prepared by using Class G oil well cement with a water-cement ratio ($w/c$) of 0.44 and incorporating three different chemical admixtures, including a new-generation polycarboxylate-based high-range water-reducing admixture (PCH), polycarboxylate-based midrange water-reducing admixture (PCM), and lingosulphonate-based midrange water-reducing admixture (LSM). The rheological properties were investigated at different temperatures in the range of 23 to 60°C by using an advanced shear-stress/shear-strain controlled rheometer. A back-propagation neural network was designed and trained by using the experimental flow curves. The shear rate, dosage of admixture, and test temperature were considered as input parameters, and the measured shear stress was the output parameter. The trained ANN was not only capable of accurately predicting the shear flow used for its training, but could also effectively predict the rheological properties of new slurries designed within the range of input parameters of the experimental database with an absolute error of 3.43, 3.17, and 2.82% for slurries incorporating PCH, PCM, and LSM, respectively. The flow curves developed by using the ANN model allowed the prediction of the Bingham parameters (yield stress and plastic viscosity) of the slurries with adequate accuracy.

Expanded polystyrene (EPS) geofoam panels of low stiffness installed vertically against the rigid nonyielding retaining structure provide additional deformations in the backfill. This behavior will lead to the mobilization of a greater portion of the soil strength, thus decreasing the lateral earth thrust acting on the rigid retaining wall. This study addresses the effect of geofoam compressible inclusion on lateral earth thrust acting on a rigid nonyielding retaining wall by small-scale model tests and numerical analyses. The finite-element code used in the numerical modeling is validated against the stress measurements on a 0.7-m-high wall model. Significant reduction is observed in the lateral earth pressures attributable to deformations concentrated at the lower half of retained soil mass. The effects of compressible inclusion thickness, relative stiffness of the EPS geofoam, and strength parameters of the backfill on lateral earth thrust acting on rigid nonyielding walls are investigated by a series of numerical analyses performed by using the verified finite-element model. Relative thickness and stiffness of the inclusion have the major roles in the reduction of the lateral earth thrust. Increase in soil strength (i.e., internal friction angle of the cohesionless backfill) has a positive effect on the isolation efficiency that becomes more pronounced for a thicker geofoam inclusion. The presence of a less-stiff layer of geofoam within the upper midheight of the retaining wall provides improvement in load isolation performance because deformations associated with the lateral compression of the softer inclusion within this zone lead to mobilization of additional shear resistance in the retained soil mass.

Surfacing the deck of a steel bridge is costly and technically challenging and an improvement on the life of the surfacing would be of economic benefit to the bridge industry. The objective of this work was to improve both the durability and stiffness of the Gussasphalt mixture, one of the preferred surfacing materials for steel deck bridges around the world, by varying the binder types and binder and filler content to obtain the optimum mix. A three-stage characterization process was proposed for the Gussasphalt mix in this study. Fundamental characterization started with evaluation of the viscoelastic properties of binders, extended to the rheological behavior of asphalt-mineral filler mastics, and ended with investigation of the engineering properties of Gussasphalt mixture. The degree of stiffening was found to vary significantly with different types of mineral filler and bitumen. The addition of Trinidad Lake asphalt (TLA) to bitumen caused an increase in stiffness, and the stiffening effect was more pronounced at lower temperatures than at higher temperatures. The suitable concentration of TLA was found to be in the range of 20–30% by weight of the binder. The optimum filler content was determined according to the rheological properties and the formation of the critical network. The increase in moduli resulting from the addition of mineral fillers had the potential benefit of improving the resistance to rutting of the Gussasphalt mixture. This indicated the possible presence of physicochemical reinforcement between the binder and filler. Fillers that produced very significant stiffening effects, however, could result in brittle mixtures and difficulty in construction. The engineering properties of a Gussasphalt mix could be characterized by Lueer fluidity, indentation, bending, and wheel-tracking tests.

Over a decade of studies have demonstrated the benefits of ultra high performance concrete (UHPC) in terms of damage tolerance, energy absorption, crack distribution, and deformation capacity. However, little information is available on the confinement behavior of UHPC, especially when confined with fiber-reinforced polymers (FRP). Sixteen UHPC-filled FRP tubes with different fiber type and tube thickness were tested under monotonic uniaxial compression. All specimens failed by rupture of the tube at or near the midheight. Similar to conventional concrete, test results showed significant enhancements in the ultimate strength and strain of UHPC—up to 98% and 195%, respectively, compared with its unconfined counterpart. The experimental results were compared with a number of available confinement models. Although one of the models provided a reasonable fit for the stress-strain response in most cases, all models generally underestimated the effectiveness of FRP confinement at higher confinement ratios. The study demonstrated the need for confinement models that could accurately predict the behavior of FRP-confined UHPC in terms of the stress-strain relationship and the respective ultimate strengths and strains.

This paper discusses the influence of high volumes of fly ash and micro polyvinyl alcohol (PVA) fibers on the fire resistance and microstructure of engineered cementitious composites (ECC). Composites containing two different contents of fly ash as a replacement for cement (55 and 70% by weight of total cementitious materials) are examined. To determine the effects of microfibers and ultrahigh ductility of ECC, ECC matrix mixtures of similar composition except PVA fiber are also produced and tested for the fire resistance. The mixtures are exposed to temperatures up to 800°C for one hour. Fire resistances of the mixtures are then quantified in terms of the residual mechanical properties (strength, stress-strain curve, deflection, and stiffness) and mass loss. The role of PVA fibers and fly ash is discussed through the analysis of microstructure and fiber-matrix interactions as a function of heat treatment. The microstructural characterization is examined before and after exposure to fire deterioration by using scanning electron microscopy and the pore size distribution is obtained by mercury intrusion porosimetry. Results indicate that adding micro PVA fiber to the ECC matrix substantially improves the fire resistance and eliminates the explosive spalling behaviors of the ECC matrix. Fire resistance of ECC mixtures is further improved with the increase of fly ash content.

It is not surprising that there has been a considerable increase in recent years in the number of research activities on the scientific and applicative level devoted to analyses of accelerated aging, determination of service life, and life-cycle assessment of constructional complexes. The primary objective of the research was to define the theoretical base supporting measurements of accelerated testing and the connection between aging and the service life of bituminous sheets. The Arrhenius law of accelerated testing as a theoretical support to experimental testing of bituminous sheets at high temperature and different exposure times was used. The current procedure of accelerated aging of bituminous sheets in accordance with European Norms (EN) takes 24 weeks at a testing temperature of $+70°\mathrm{C}$. The test procedure is fairly long and takes place at a relatively low temperature, which does not represent a significant thermal load in the aging of the majority of bituminous products. According to our measurements and calculations, a shortened testing time of accelerated aging of 12 weeks requires an equivalent aging temperature of $+82.0°\mathrm{C}$ for oxidized bituminous products, $+79.2°\mathrm{C}$ for atactic polypropylene (APP)-modified bitumen and $+76.5°\mathrm{C}$ for styrene-butadiene-styrene (SBS)-modified bitumen products, to achieve the same impact of accelerated aging on bituminous sheets, because it provides testing procedures according to the standard. These results are useful to control quality, test resistance to aging, and determine the life expectancy of bituminous products, the characteristics of which are determined in a significantly shorter time.

The application of fiber-reinforced polymer (FRP) composites in civil engineering has advanced drastically in recent years, especially in the retrofit of concrete bridge columns. However, composite’s typical nonductile behavior and low-energy absorption are some of the concerns that have yet to be fully addressed. The objective of this research is to investigate a new mechanism-based bistable composite structure as the wrapping system for concrete columns to improve the energy absorption and damage tolerance. The bistable structure consists of energy-absorbing main links (primary load carrier) and waiting links (secondary load carrier to be activated after main link fails). A series of uniaxial compression tests on cylindrical concrete members wrapped with hybrid carbon-glass FRP bistable structure were conducted to demonstrate the concept and study the effect caused by link geometry. The results showed that a controlled failure with signs of failure (warning) was achieved in the system and both the ductility and energy absorption were enhanced. The effectiveness of the confinement depended on the number of links and the energy absorption relied on the size of the links.

Many factors of mix proportion affect the chloride permeability and freeze-thaw resistance of high-performance concrete containing nanoparticles, including the dosages of cement, nanomaterials, mineral fine admixture, and chemical admixture and the water-binder and sand ratios. The aim of this study was to evaluate the effects of these factors on the chloride permeability and freeze-thaw resistance of high-performance concrete containing nanoparticles and determine which factors yield the greatest influence. The gray relational analysis method was used to calculate relational grades between the effect factors and the diffusion coefficient of ${\mathrm{Cl}}^{-}$ and between the effect factors and the antifreezing durability coefficient. In addition, sequences showing degree of influence on chloride permeability and freeze-thaw resistance were obtained. The results indicate that among the seven selected parameters of mix proportion design, water-binder ratio, dosage of cement, and dosage of nanoparticles had the greatest influence on the chloride permeability and freeze-thaw resistance of high-performance concrete containing nanoparticles. To improve the antipermeability of ${\mathrm{Cl}}^{-}$ and the freeze-thaw resistance of high-performance concrete containing nanoparticles, the water-binder ratio and dosages of cement and nanomaterials must be strictly controlled (i.e., the water-binder ratio decreased and the dosages of cement and nanomaterials increased).