Journal of Materials in Civil Engineering

During the last decade, synthetic fibers have been used widely in the structure application; however, the strength models of synthetic fiber-reinforced concrete are not available, as most of the models have been proposed for steel fiber–reinforced concrete only. Extensive experimental investigation has been conducted on poly-vinyl alcohol (PVA) fiber-reinforced high-strength concrete to develop the strength model based on multiple linear regressions analysis through least square error. Regression models have been obtained for the different responses of concrete as a function of process variables, i.e., compressive strength of concrete, fiber matrix interface, and fraction of metakaolin (MK) as cement-replacing material. A total of 50 mixes of concrete have been examined using metakaolin of 0, 5, 10, 15, and 20% by weight of cement and PVA fibers of aspect ratio 45, 60, 90, and 120 with volume fraction of 0, 1, 2, and 3%. Five mixes without PVA fiber have been used as control mixes. For each mix, the compressive strength, splitting tensile strength, modulus of rupture, and modulus of elasticity have been determined at the age of 7, 28, 56, and 90 days. Moreover, models have been compared with the artificial neural network and existing predictive models of steel fiber–reinforced concrete. The existing models of steel fiber–reinforced concrete have not been found to be applicable to synthetic fiber–reinforced concrete. However, the proposed models are closely fit to the experimental results, and the results are comparative with the artificial neural network approach.

The objective of this study is to evaluate a new generation of self-healing materials that hold promise for better durability and performance. The in situ polymerization method was used to develop double-walled microcapsules. The microcapsules were prepared in a single batch process containing sodium silicate as the healing agent encapsulated in double-walled polyurethane/urea-formaldehyde (PU/UF) microcapsules. Double-walled microcapsules provide enhanced durability at high temperatures compared with single-walled microcapsules while preserving adequate interfacial bonding of microcapsules. A parametric study was carried out to investigate the effect of different parameters such as agitation rate, pH, and temperature on the performance of the microcapsules and to determine the optimum microencapsulation procedure. The prepared microcapsules were then incorporated into self-healing concrete beams. To monitor the healing process of the cracks, microcracks were created by imposing a certain magnitude of displacement in the middle of the beams. The healing process of concrete specimens was monitored and quantified using portable ultrasonic nondestructive digital indicating tester (PUNDIT). Results showed that lower pH and higher agitation rate and curing temperature improve the formation of microcapsule shells. Measurements of ultrasonic wave transmission time through the concrete specimens containing different contents of microcapsules were analyzed to quantify the healing rate. It was found that the healing rate in concrete beams with 5% microcapsules was higher in the first week in comparison with specimen containing 2.5% of microcapsules.

To clarify the mechanism of chloride penetration into concrete subjected to drying–wetting cycles, two kinds of concrete, ordinary portland cement concrete and fly ash (FA) concrete, were tested in a cyclic NaCl solution to show the influence of mix proportion, period ratio of drying to wetting, and exposure time. Based on the experimental profiles of free chloride concentration obtained after 30 and 60 weeks, it was found that the depth of convection zone varied from 6 to 15 mm and increased in duration when the air-drying period in one cycle was prolonged or the exposure time increased. Through a regression analysis of chloride profiles located in the inner part of the concrete beyond the advection zone, it was verified that diffusion was the dominant mechanism of chloride transport and could be well fitted with the proposed modified diffusion model taking into account the influence of convection depth. Finally, the time-dependent chloride diffusion coefficient $D_{\mathrm{Cl}}$ was calculated on the basis of the apparent chloride diffusion coefficient $D_{\text{app}}$ and the obtained time exponent $m$. The effect of FA content on $D_{Cl}$ was also examined.

To date, internal curing (IC) has been widely accepted as a promising way to mitigate the autogenous shrinkage of high-performance concretes (HPCs). While extensive studies have confirmed the benefits of internal curing to HPCs cured under sufficient moisture, the durability implications of early-age drying remain unclear for internally cured cement-based materials. As such, this work investigates the influence of early-age drying on the properties of internally cured cement mortars containing saturated fine lightweight aggregate (LWA). The tests conducted on cement mortars with or without internal curing include: drying shrinkage, moisture loss, compressive strength, splitting tensile strength, water absorption, and gas permeability. Additionally, two surface sealers were individually applied to mortars and evaluated for their effectiveness in reducing the risk of early-age drying. The results reveal that early-age drying significantly offsets the advantages of internal curing of LWA with respect to shrinkage reduction and microstructure densification. In this case, the presence of surface treatments can preserve and enhance the benefits of internal curing of cement mortar. Observations made using a scanning electron microscope suggest that coverage and integrity of the sealer film define its effectiveness in retaining moisture. Further studies on concrete specimens with larger cross sections and with various curing conditions are recommended in order to practically evaluate the effect of early-age drying on internally cured concrete.

This paper presents a study on the effectiveness of two forms of reinforced grout confining systems for hollow concrete block masonry. The systems considered are: (1) a layer of grout directly confining the unreinforced masonry, and (2) a layer of grout indirectly confining the unreinforced masonry through block shells. The study involves experimental testing and finite-element (FE) modeling of six diagonally loaded masonry panels containing the two confining systems. The failure mode, the ultimate load, and the load-deformation behaviors of the diagonally loaded panels were successfully simulated using the finite-element model. In-plane shear strength and stiffness of the masonry thus determined are used to evaluate some selected models of the confined masonry shear including the strut-and-tie model reported in the literature. The evaluated strut width is compared with the prediction of the FE model and then extended for rational prediction of the strength of confined masonry shear walls.

Exposing concrete to high temperature causes progressive breakdown of the cement gel structure and consequently severe deterioration and loss in the structure’s load bearing capacity. This paper presents an experimental study on the mechanical and physicochemical properties of lightweight self-consolidating concrete (LWSCC) subjected to high temperatures. Four LWSCC mixes and one normal-weight self-consolidating concrete (NWSCC) were tested. The specimens underwent two different tests: a fire test and a thermal characterization test. The first is the ISO fire test, which consists of heating the prismatic specimens according to the standard fire curve up to 600°C. The second test is the thermal characterization test, which consists of heating the specimens at a rate of $1°\mathrm{C}/\min$ up to 400°C. Ultimate and residual compressive strength, loss of mass, density, water porosity, spalling characteristics, and other physicochemical properties before and after the fire tests were recorded. The LWSCC performed differently from the NWSCC with respect to mechanical properties and spalling resistance. Scanning electron microscopy and backscatter electron images analysis were performed to study the microstructure of both heated and unheated specimens.

Combustion of switchgrass, a low-carbon fuel, generates energy and ash that can be recycled as a pozzolan in cement. This study aimed to optimize switchgrass combustion to achieve high-energy conversion and ash recycling value for cement. Combustion factors under investigation included temperature (350°C, 450°C, 550°C, or 650°C) and retention time (1 h or 4 h). Energy release was quantified by thermogravimetric analysis-differential scanning calorimetry, and ash pozzolanic activity was assessed with the concrete strength test. A numeric simulation model of the pozzolanic reaction, based on unbiased experimental data from $\mathrm{Ca}(\mathrm{OH}{)}_2$-ash suspensions, provided insight into how combustion conditions affected the pozzolanic properties of switchgrass ash. Consequently, combustion at 550°C for 4 h was recommended for concurrently optimizing the ash pozzolanic activity (114%) and energy output ($4.21\mathrm{kJ}/\mathrm{g}$) from switchgrass.

Damage due to soil shrinkage is a serious problem in many parts of the world. Lime can significantly improve the performance of soils, both in terms of increase in strength and reduced swelling. However, its efficacy in reducing shrinkage of soils has not been studied much. A series of experiments were conducted to develop an understanding of the shrinkage behavior of lime-treated soils. Six different soils covering wide range of plasticity were treated with varied percentage of lime and curing period. Lime increases the shrinkage limit of soils irrespective of their plasticity characteristics; however, it is more in case of high plastic soils than the low plastic ones. Volumetric shrinkage continued to reduce until about 5% of lime content beyond which further reduction was marginal. Hence 5% of lime can be considered as the optimum lime content giving maximum shrinkage reduction. With lime the shrinkage responses of soils were found to have grown flatter indicating that lime can effectively reduce the rate of shrinkage leading to reduced cracking of soils.

This paper presents the results from a laboratory study in which the influence of waste engine oil on the performance of hot-mix asphalt (HMA) containing reclaimed asphalt pavement (RAP) was evaluated. The lab test consists of binder test and mixture test. For binder test, the extracted RAP binder was blended with virgin binder and waste oil to investigate the rheological properties as well as fatigue properties. The waste engine oil was collected from a local auto repair shop. Performance Grade 64-22 was selected as virgin binder. For mixture test, the HMA containing RAP was evaluated at three RAP contents [(1) 0%, (2) 25%, and (3) 40%] and three waste oil contents [(1) 0%, (2) 2%, and (3) 5%]. Binder master curves, linear amplitude sweep, Superpave indirect tension, beam fatigue, and asphalt pavement analyzer rutting tests were conducted to evaluate the engineering properties of asphalt and asphalt mixtures. The results from the research reported in this paper indicated that the incorporation of waste engine oil into HMA with RAP may offset the increase of stiffness caused by aged binder in RAP. The inclusion of waste engine oil decreased optimum asphalt content, and reduced rut resistance. Meanwhile, it may also have limited improvements on fatigue resistance of the mixtures.

The temperature profile within the asphalt layer of a flexible pavement plays an important role in the design of hot-mix asphalt and in the performance models of asphalt concrete materials such as low-temperature cracking and asphalt binder oxidation. In this paper, the time-dependent temperature profile within an asphalt concrete layer is modeled as the heat conduction problem in a one-layer pavement system, where the surface boundary condition is simply the pavement surface-temperature history during the time period of interest. An infinite series solution for asphalt layer temperature prediction was derived using measured pavement surface temperatures. The main mathematical tools employed in deriving the analytical solution are separation of variables and Duhamel’s principle. Mathematically, the infinite series are proven to converge uniformly over the finite physical domain at a fixed time $t$. Field validation based on measured in situ temperature data demonstrated that the proposed closed-form solution generated reasonable transient temperature profiles in the asphalt layer for a two-layer pavement system. The proposed algorithm is easy to be applied in assisting field engineers to rapidly estimate asphalt pavement temperature profiles based on measured pavement surface-temperature data.

This paper documents successful use of portland-limestone cement (PLC) with 50% replacement of cement using supplementary cementitious materials (SCMs) during expansion and renovation of a college football stadium. Concrete becomes more sustainable as clinker content is reduced, and use of PLC in place of ordinary portland cement (OPC), e.g., such as per a common U.S. national standard, has considerable appeal, especially if performance tradeoffs that are often associated with more sustainable concrete can be addressed. Higher replacement of cement in concrete with SCMs may also be possible by incorporating PLC, further adding value to projects from performance and sustainability perspectives. Concrete containing PLC was successfully used in approximately $\mathrm{1,900}{\mathrm{m}}^3$ of on-grade and structural concrete flatwork. The cementitious system contained 50% PLC, 30% slag cement, and 20% Class C fly ash. This paper provides information related to properties of the PLC supplied to the stadium project as they are not necessarily typical of PLCs used worldwide over the past several years. One especially beneficial performance trend was that early-age strength gain of concrete containing 50% PLC, 30% slag cement, and 20% Class C fly ash was noticeably better than that of otherwise comparable concrete containing OPC. Additionally, use of PLC did not result in finishing problems, reduced slump by approximately 20 mm, reduced set time by approximately 1 h, and improved chloride ion resistance.

This paper intends to develop and validate an innovative method to determine the effective thermal conductivity of asphalt concrete considering thermal properties of individual components and volumetric compositions. Three-phase microstructure models (asphalt binder, aggregate, and air void) of asphalt concrete were randomly generated based on aggregate sizes and gradations. A finite-element (FE) model was developed to calculate the effective thermal conductivity of asphalt concrete by applying a steady heat transfer process. A multiscale simulation approach was used to consider the effect of different-sized aggregates at various length scales using a hierarchical framework that reduces computational cost. The prediction results were validated with experiment data and showed better accuracy than the results predicted from other analytical models. The influences of air void content and distribution, coarse aggregate content, aspect ratio of aggregate, asphalt binder with conductive and insulation additives, and lightweight aggregate on the effective thermal conductivity of asphalt concrete were analyzed. In general, the effective thermal conductivity decreases with the increase of air voids or the decrease of coarse aggregate content. However, when the distribution of air voids is nonuniform in asphalt concrete, the effective thermal conductivity may deviate from the normal range. On the other hand, the effective thermal properties of asphalt concrete could be equally affected by thermal modification of asphalt binder or replacement of lightweight aggregate.

The steelmaking industry in the United States generates 9–16 million metric tons of steel slag every year. The excess steel slag ($\sim 15$ to 40%) that is not reutilized is stockpiled in steel plants and eventually landfilled at slag disposal sites. Use of steel slag in civil engineering applications can help alleviate the steel slag disposal problem and help preserve natural resources. Understanding the in-service performance of steel slag is essential for its proper use as a geomaterial by the construction industry. In this paper, the results of a series of tests (grain-size analysis, X-ray diffraction, specific gravity, compaction, maximum and minimum dry unit weight, direct shear, consolidated-drained triaxial compression, and long-term swelling tests) performed on samples of both fresh and aged basic oxygen furnace (BOF) steel slag from a steel plant in Indiana are presented and analyzed. The test results indicated that both fresh and aged BOF steel slag exhibit superior strength and stiffness characteristics to conventional frictional materials. Based on toxicity characteristic leaching procedure (TCLP) test results, the BOF slag tested in this study was classified according to the Indiana Administrative Code (IAC). Long-term swelling test results showed that both fresh and aged BOF steel slag increase in volume when exposed to water due to the presence of free lime and magnesia in their chemical composition. Replacing 10% by weight of fresh or aged BOF steel slag with Class C fly ash was effective in suppressing the swelling behavior.

Mechanical grinding was used to increase the specific surface area of cement in order to increase the dosage of phosphorus slag (PS) in Type $\mathrm{P}·\mathrm{O}42.5$ cement. X-ray diffraction, hydration heat, and scanning electron microscopy were used to analyze the hydration process of cement containing PS. The results show that the increase of fineness of cement can obviously improve the mechanical property of PS cement pastes. When specific surface area increased to $460{\mathrm{m}}^2/\mathrm{kg}$, the flexural strength and compressive strength of cement mortars mixed with 40% PS for 3 and 28 days are 3.77, 17.6, 9.89, and 52.0 MPa, respectively, still meeting the strength requirements of Type $\mathrm{P}·\mathrm{O}42.5$ cement. The PS admixture can effectively lower the hydration heat of cement. Phosphorus slag delayed the hydration process of cement, inhibited the formation of ettringite and contributed a low strength of mortars for 3 days curing. The degree of hydration of PS at the early ages was low, leading to a poor interface between PS particle and cement matrix.

A new one-dimensional (1D) viscoelastic creep formulation is proposed for modeling the recoverable deformation component in asphalt concrete (AC). The formulation is designed to accommodate different tensile and compressive properties in analogy with bimodular elasticity. It is structured as a Volterra equation of the second kind with a kernel that alternates between tensile and compressive compliances based on the sign of the viscoelastic (VE) strain. If the response is only in one direction, or if the viscoelastic properties are identical in both directions, the model degenerates to the linear Boltzmann superposition. As a demonstrative application, the theory was utilized to match the response of an asphalt specimen exposed to several load–unload–rest sequences in uniaxial tension–compression. It was found that two dissimilar creep functions were needed to achieve excellent reproducibility. At short times the two were almost overlapping while for longer times they departed such that the compliance associated with compression was lower than the tension-related compliance; this finding is in tune with previously reported experimental evidence. The new theory is deemed capable of correctly simulating viscoelastic tension–compression nonlinear behavior.

The research reported in this paper evaluates a novel bitumen modification through the use of different inorganic nanoparticles, such as nanozinc oxide, nanosilica, and nanotitanium dioxide. In order to improve the dispersion of inorganic nanoparticles in bitumen, inorganic nanoparticles were surface-modified by 3-aminopropyltriethoxysilane. The effect of surface modified inorganic nanoparticles on physical and ultraviolet (UV) aging properties of bitumen was investigated. The UV aging mechanism of the inorganic-nanoparticle-modified bitumen was characterized by using Fourier-transform infrared spectroscopy (FTIR). The results show that 3-aminopropyltriethoxysilane is successfully bound on the surface of the three inorganic nanoparticles in the form of a covalent bond according to the FTIR result. Surface-modified inorganic nanoparticles show good compatibility with bitumen on the basis of high-temperature storage stability. Compared with nanosilica and nanotitanium dioxide, nanozinc oxide shows better dispersion in bitumen. The physical properties of bitumen are slightly influenced by the addition of inorganic nanoparticles. In addition, the changes of physical properties of bitumen depend on the nature of inorganic nanoparticles. The UV aging of bitumen is a process that causes bitumen to harden as indicated by FTIR, penetration, viscosity, and softening point values. However, the viscosity aging index and softening point increment of bitumen can be effectively reduced with the introduction of inorganic nanoparticles, indicating good UV aging resistance of inorganic-nanoparticle-modified bitumen. Three inorganic nanoparticles show different influence on the UV aging resistance of bitumen. Compared with nanosilica and nanotitanium dioxide, nanozinc oxide shows the better improvement in UV aging resistance of bitumen by displaying lower viscosity aging index and softening point increment values as well as the carbonyl index.

Although coating masonry walls with polymeric elastomers can mitigate the effects of a projectile strike in a blast or explosion, it may also increase the fire hazard to the structure and the occupants. Although a rigorous assessment of this problem would require full-scale fire tests, considerable insights can be gained by performing bench-scale tests in conjunction with computer simulations. A joint experimental/numerical methodology is presented in this paper to evaluate the extent to which blast-resistant coatings, applied on masonry walls, may contribute to the spread of existing fire. The experimental data are obtained by performing cone calorimeter heat release rate (HRR) measurements. Flammability characterization and the heat flux generated for structural systems and components that are coated with blast-resistant and fire-retardant polymeric coatings are performed using the NIST fire dynamic simulator (FDS). In these simulations, structural concrete columns and masonry walls are exposed to an assumed fire. The results presented in this paper could be employed in coupled thermal/structural finite element analysis to assess the performance of concrete members coated with polymeric materials and subjected to fire loading.

In this paper the impact resonance (IR) test method is used as a nondestructive tool to examine the curing progression, freeze/thaw ($\mathrm{f}/\mathrm{t}$) resistance, and healing potential of cement-stabilized soils. Resonant frequency (RF) measurements on specimens moist cured for up to 241 days indicate that the main portion of the hydration process is completed after about 60 days. Results of RF measurements on immature (i.e., cured for 16 days) and mature (i.e., cured for over 110 days) specimens exposed to 12 cycles of $\mathrm{f}/\mathrm{t}$ indicate that the initial $\mathrm{f}/\mathrm{t}$ exposure had a significant effect on the degradation of the structure. After the initial $\mathrm{f}/\mathrm{t}$ cycle, some specimens exhibited continued reductions in RF values to as low as 10% of the initial measurements, while several specimens showed signs of recovery leading to minor increases in the RF values. Changes in RF values are compared with the hydraulic conductivity changes measured on the same specimens reported in a previous publication by the authors. Based on the results, a prescreening scheme is proposed that can significantly reduce the time required for $\mathrm{f}/\mathrm{t}$ studies of cement-stabilized soils. Also, RF measurements after 120 days of a post-exposure healing period show a significant potential for recovery in RF values for $\mathrm{f}/\mathrm{t}$ exposed specimens. However, the recoveries in RF values are not proportional to the hydraulic conductivity recovery of the specimens.

The use of foamed asphalt binder to produce warm-mix asphalt has increased significantly during the past few years. It is recognized that (1) foaming characteristics of the binder influence the workability of the asphalt mix, and (2) different asphalt binders tend to foam differently with all other factors being the same. The causes for the latter are relatively less explored and is the focus of this paper. The research reproted in this paper investigated the influence of the properties of asphalt binder on its foaming characteristics. A physical model for expansion of asphalt binder foam based on foam physics was used to quantify the effect of water content, temperature, surface tension, and liquid additive (through its effect on surface tension) on the expansion ratio of asphalt binder foam. Analysis of results demonstrates that the bubble size distribution (up to a certain limit) does not directly dictate the maximum expansion ratio of the asphalt binder foam. The analysis also shows that only a fraction of the water added to the binder is effective in creating the foam. The effective water content was strongly correlated with the surface tension of the binder, which was also substantiated by the solubility theory. Surface tension of the asphalt binder was also found to be strongly correlated to the stability of the foam. Foam characteristics of binders modified with additives also demonstrated that stability and expansion of foams can be significantly improved using carefully selected liquid additives.

The effect of discrete cracks on the Wenner probe measurements for surface resistivity of plain and reinforced concrete elements is investigated. A numerical modeling approach is utilized to study the effect of a wide range of parameters that are related to discrete cracks (type, depth, width, location, and orientation with respect to the probe), reinforcement (cover thickness, bar spacing, and bar orientation with respect to the crack), and the Wenner probe (electrode spacing). Depending on the type of the crack and its location, the results indicate that measurements might have errors as much as $\sim 200\%$ higher or $\sim 50\%$ lower than the actual resistivity of concrete. Rebar mesh reduces measured resistivity and causes additional error in measurements—the denser the reinforcement, the higher the error. Whereas in most scenarios, crack and rebar mesh affect the accuracy of measurements independently, the effect of deep cracks that surpass the depth of rebars is limited by the presence of rebar mesh. A decrease in electrode spacing would reduce the errors associated with rebar mesh while it increases the impact from the crack; therefore, the common perception of using smaller electrode spacing for error minimization is not valid for reinforced concrete elements with cracks.

This study focuses on the tensile behavior of fiber-reinforced polymer (FRP) composites in a concrete-based alkaline environment. Because basalt/glass FRP (BFRP/GFRP) composites exhibit relatively poor alkaline resistance compared with carbon FRP (CFRP) composites, a rubber toughening modification method has been proposed to mitigate microcracking and decrease the diffusion of the alkaline solution in the resin matrix. Different proportions of liquid rubber toughening agents were added into the epoxy resin, on the basis of which different FRP composites were made and then subjected to tensile tests after alkaline exposure. Test results indicated that the rubber toughening modification approach can significantly reduce the tensile strength degradation of the BFRP and GFRP composites in the alkaline solution. Moreover, no degradation of the elastic modulus for the FRP composites was observed. The weight gain and microstructure of the FRP composites were also investigated before and after the alkaline exposure to determine the corrosion mechanisms of the FRP composites in the alkaline environment and interpret the mechanical test results.

This paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45–0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the accuracy of the models was experimentally confirmed using random grout compositions. The predicted-to-measured ratio ranged from 0.97 to 1.08, indicating a good agreement between the confirmation results and the expected results from the statistical models.

The use of industrial by-products and wastes as raw materials for the construction industry has increased in recent years. This paper seeks to assess the effect of waste latex paint (WLP) constituents on variations in flow and rheological properties of cement pastes, including their compatibility with commonly used water reducers (WRs) and timing addition during batching. The tested WLPs were not randomly collected from waste collection sites, but rather produced and stored without biocides for approximately 6 months to expire. Test results have shown that flowability is highly affected by the WLP latex content, pigment-to-extender ratio, and percentage used for the substitution of mixing water. Mixtures prepared with WLPs added before WRs led to reduced flowability, given the competitive adsorption of the latex polymers onto cement particles. Remarkable incompatibility reflected by increased cohesiveness rates over time was noticed between WLPs and polycarboxylate-based WRs.

This paper reports on the accuracy of new test methods developed to measure the air and water permeability of high-performance concretes (HPCs). Five representative HPC and one normal concrete (NC) mixtures were tested to estimate both repeatability and reliability of the proposed methods. Repeatability acceptance was adjudged using values of signal-noise ratio (SNR) and discrimination ratio (DR), and reliability was investigated by comparing against standard laboratory-based test methods (i.e., the RILEM gas permeability test and BS EN water penetration test). With SNR and DR values satisfying recommended criteria, it was concluded that test repeatability error has no significant influence on results. In addition, the research confirmed strong positive relationships between the proposed test methods and existing standard permeability assessment techniques. Based on these findings, the proposed test methods show strong potential to become recognized as international methods for determining the permeability of HPCs.

The performance of alkaline activated ground slag/ultrafine palm oil fuel ash (AAGU) mortars upon their exposure to 6% of ${\mathrm{H}}_2{\mathrm{SO}}_{4aq}$ (acid) for 60 days was investigated. The mortars were prepared with ${\mathrm{NaOH}}_{aq}$ of varied concentrations and ${\mathrm{Na}}_2{\mathrm{SiO}}_{3aq}$ (${\mathrm{Ms}\text{-}\mathrm{SiO}}_2{/\mathrm{Na}}_2\mathrm{O}=3.3$) activators and then cured at a temperature of 60°C for 24 h. The findings through strength, microstructural examination, and product characterization revealed that sulfuric acid attack could cause the disintegration of microstructure through the removal of the key elements—Ca, Mg, Na and Al—which resulted in the formation of gypsum, expansive shrinkage cracks, and a reduction in strength retention. Maintaining the slag content, concentration of ${\mathrm{NaOH}}_{aq}$, ${\mathrm{Na}}_2{\mathrm{SO}}_{3aq}{/\mathrm{NaOH}}_{aq}$ ratio, and the mixing water content in the range of 20–40 wt.%, 8–10 M, 1.0–2.5, 5–10 wt.% of the pozzolanic materials (PMs), respectively could enhance the resistance of AAGU mortar subjected to sulfuric acid attack.

The heat transfer process in soil depends on its thermal conductivity property and is affected by soil compositional and environmental factors, such as soil gradation, mineralogy components, compaction moisture content, and dry unit weight conditions. In this research, thermal conductivities of three quartz sands were studied using a newly developed thermo–time domain reflectometry (TDR) probe. The test results revealed that thermal conductivity of quartz sands increased with compaction moisture content and dry unit weight. Higher quartz content also led to higher thermal conductivity. The new thermo-TDR probe provided measurements of thermal properties similar to those of the standard KD2 probe. The deviation of the two methods was within 5%. An improved thermal conductivity model was also proposed on the basis of the normalized thermal conductivity concept and present experimental data. This improved model exhibited the highest accuracy in thermal conductivity predictions of quartz sands (within 15% deviation at all soil moisture conditions). The $R^2$ value, lowest standard error from linear regression analysis, and relatively low root-mean square error (RMSE) analysis value was compared with those of five other thermal conductivity models. The results indicated that the proposed model provided very good predictions.

In this study, the ratio of dissipated-energy change (RDEC), developed based on the fundamental concept of energy, was used to investigate the healing potential of dense-graded asphalt mixtures having different types of asphalt binder. For this purpose, cylindrical asphalt mixture specimens were prepared using the calcareous-type crushed-stone aggregates. In addition, $60/70$ and $85/100$ penetration asphalt binders and $85/100$ penetration asphalt binder modified with styrene–butadiene–styrene (SBS) polymer modifier were used for the specimen fabrication. Subsequently, displacement/strain-controlled uniaxial fatigue tests were carried out on the specimens at various rest times, different strain amplitudes, and a single temperature, with three replicate specimens for each experimental combination. The healing index obtained by the RDEC approach was used to study the effects of different variables on the healing potential of asphalt mixtures. To evaluate the healing potential of asphalt mixes during the rest periods (RPs) having nonzero tensile strains, a special loading pattern was designed. Based on the test results, it was found that the microcracks may also be healed even under the prescribed condition. However, this healing potential, which is less than that obtained for the case of RPs having zero strain, has a decreasing rate with the increase of strain value during the rest times. Moreover, it was found that the effect of SBS polymer modifier on healing potential of asphalt mixes depends on the selected loading pattern.