Journal of Materials in Civil Engineering

This paper presents the results from a laboratory investigation on the effects of aging on the properties of two binders recovered from two different sources of Reclaimed Asphalt (RA) and additivated with a biorejuvenator derived from pine trees. It has been already proven that the rejuvenators are able to restore some of the properties of the aged binder present in the RA, but nowadays their effects into the long-term period are not well known. In this regard, the rejuvenated asphalt binders and a virgin binder, defined as a target, have been aged artificially to simulate short- and long-term aging. All binders have been studied conducting physical, chemical, rheological, and performance-related tests at three different aging levels. Results show that physical and rheological properties can be fully restored by the addition of the proper dose of rejuvenator, while the chemical composition should be investigated in more detail. Rejuvenated binders exhibit great long-term performance especially at high and low temperatures, but also show significant resistance against fatigue at intermediate temperatures.

A simplified mathematical model for concrete carbonation has been developed and compared with data from accelerated and real exposures. A chamber for an accelerated carbonation test has been built, and the results derived from the test have been used to propose the simplified mathematical model. Two different concrete specimens, denoted $S_1$ and $S_2$, were exposed. For $S_1$ concrete, the proposed mathematical model is a mass balance among ${\mathrm{CO}}_2$, $\mathrm{Ca}(\mathrm{OH}{)}_2$, and C-S-H and takes into account the change of the porosity with time. Two different simulation software programs were employed to solve the set of differential equations. The model fits well experimental results reported in other works allowing prediction of service life in concrete structures. On the other hand, $S_2$ concrete did not suffer carbonation. A comparative analysis of behavior of both specimens was made.

Shrinkage cracking of concrete at an early age has notable and adverse effects on the durability and long-term performance of the material because it damages surface integrity or undermines overall uniformity of concrete. In order to mitigate early-age concrete shrinkage cracking, a new gel-type superabsorbent polymer (SAP) has been developed as an internal curing agent (ICA). This paper investigates the effects of the introduced gel-type ICA dosage and curing conditions on early-age cracking mitigation of concrete. It is found that the cracking area of concrete is greatly reduced when up to $41\mathrm{kg}/{\mathrm{m}}^3$ gel ICA is used in concrete with water:cement ratio ($w:c$) of 0.5, and the internal relative humidity (IRH) of concrete at 7 days can be maintained at 92% or above. The gel-type ICA also is more effective in delaying initial cracking time and lowering the decreasing rate of IRH. It is believed that the superiority of this newly introduced ICA lies not only in its uniform dispersion in concrete but also in its molecular network structures, which contribute to maintaining moisture balance in the near-surface layer of concrete. This new gel-type ICA provides a new alternative way to control early-age cracking of modern concrete and it has a promising future in concrete construction, especially in windy, drying, and high-temperature areas.

One of the effective ways to prevent the brittle behavior of high-strength concrete is to use fibers. Therefore knowing the stress-strain behavior of high-strength fiber-reinforced concrete is essential for nonlinear analysis and design purposes. In order to investigate the compressive stress-strain behavior of concrete reinforced with Forta-Ferro and steel fibers with and without the inclusion of silica-fume and nanosilica pozzolans, this paper experimentally investigates the effect of fibers and pozzolans on the mechanical properties of fiber-reinforced high-strength concrete including compressive strength, strain at peak stress, ultimate strain, and toughness index. Based on the experimental results, empirical equations are proposed for the compressive stress-strain parameters affecting the behavior of fiber-reinforced concrete. Finally, to predict the stress-strain relationship of high-strength fiber-reinforced concrete, two different models are presented which are capable of properly predicting the experimental curves. Because using silica fume and nanosilica leads to a change in the gradient of the stress-strain curve of fiber-reinforced concrete, the necessity of modifying the proposed models in order to improve accuracy is explored.

The complex modulus ($E^{*}$) is a fundamental material property extensively used for characterizing the viscoelastic behavior of asphalt concrete. In recent years, numerous micromechanics-based models have been proposed for predicting the asphalt concrete $E^{*}$. Unfortunately, few of them are capable of rationally considering the aggregate interlocking effect that plays a vital role in the reinforcement mechanisms of asphalt concrete. To address this issue, this study presents a new approach, in which the asphalt mastic matrix phase in the traditional models is substituted with a new equivalent matrix phase that incorporates both the viscoelastic properties of asphalt mastic and the effect of aggregate interlock reinforcement. Two interlock factor functions, which were initially proposed for characterizing the confinement dependency of the triaxial $E^{*}$ of asphalt concrete, are introduced into the two springs, two parabolic elements and one dashpot (2S2P1D) model representing the complex shear modulus ($G^{*}$) of the original asphalt mastic matrix phase. The feasibility and effectiveness of the approach is demonstrated by means of the traditional two-layer built-in (TLB) and generalized self-consistent (GSC) micromechanics models. The results show that the proposed method overcomes the shortcomings of underpredicting the storage and loss moduli of asphalt concrete over the intermediate- and low-frequency range in the traditional micromechanics methods. Also, without changing any original geometries, the advantages of simplicity and practicability of the traditional models remain. Finally, recommendations for future research are discussed in brief.

Concrete corrosion caused by sulfuric acid attack is a known phenomenon in sewer systems, resulting in significant economic losses and environmental problems. However, there is a scarcity of reported laboratory simulations and experimental work investigating the contributing factors controlling the corrosion. In this investigation, funded by the U.K.’s Engineering and Physical Sciences Research Council (EPSRC), the effect of temperature and the acidity of sulfuric acid solution on concrete specimens extracted from brand-new concrete sewers has been investigated. In this investigation, the concrete samples are submerged in three sulfuric acid solutions ($\mathrm{pH}=0.5$, 1, and 2) for 91 days under different temperatures (10, 20, and 30°C). Mass loss and compressive strength of the concrete specimens were tested and recorded at 7, 14, 28, 42, 56, and 91 days, providing interesting data for visualizing the changes taking place in the concrete samples (change in properties) during the time of immersion. The results revealed that samples overall mass increased at the early stages of the corrosion process. It also was observed that the overall mass of the samples decreased significantly at the later stages of the testing process with respect to the acidity of the solutions used. Although the change in temperature did not have a significant effect on the compressive strength of the tested samples, the rise in temperature, however, had a considerable effect on the mass loss of the concrete samples that were immersed in the most aggressive solution (i.e., $\mathrm{pH}=0.5$ and $\mathrm{temperature}=30°\mathrm{C}$) at 91 days. This research clearly demonstrated a high correlation between the acidity of the solution and the rate of corrosion with respect to time.

Warm-mix asphalt (WMA) has gained lot of interest among researchers and highway engineers in recent years because of the environmental and financial benefits associated with lower production temperatures. However, there are some characteristics of warm-mix asphalt that have not been investigated in detail. Several studies have been conducted to analyze the performance of warm asphalt mixtures, but there is a need to investigate the physical and rheological properties of warm-mix binders. This paper presents results of a study carried out to investigate the aging characteristics of warm-mix asphalt binders. WMA binders prepared with three different warm-mix additives were aged in a rolling thin-film oven (RTFO) at lower temperatures to simulate warm-mix asphalt aging while control binders were aged at 163°C only. Short-term aged binders were then aged in a pressure-aging vessel (PAV) to simulate long-term aging. Several parameters like aging index, $G^{*}/\sin \delta$, $G^{*}\sin \delta$, $m$-values, and stiffness of the aged binders were evaluated and results of warm-mix binders were compared with hot-mix asphalt binders. Fourier transform infrared (FTIR) spectroscopy tests were also carried out on these binders to quantify aging of the binders with and without warm-mix asphalt additives.

This paper studies the bond stress–slip curve of recycled concretes and the influence of recycled coarse aggregate, which leads to the determination of bond behavior at serviceability. In order to perform this analysis, a study of the compressive strength of the recycled aggregate concretes is required, due to the relationship between the bond strength and the mean compressive strength. Two series of concretes are designed with different water to cement ratios (0.50 and 0.65) and four different replacement percentages (0, 20, 50, and 100%). The experimental program tests cubic specimens through 144 compressive strength tests and 160 pull-out tests at different ages, from 3 to 365 days. The results show that replacement ratio significantly influences concrete properties related to the compressive strength and bond behavior. Two functions are developed to predict time-dependent compressive strength and bond stress–slip curve of recycled concrete, both based on the International Federation for Structural Concrete Model Code expressions for conventional concrete.

Sand pluviation is a method used to prepare a model sand specimen to carry out some particular laboratory tests such as static and dynamic tests on footings, retaining walls, piles, as well as calibration of static and dynamic penetrometers. Preparation of uniform reconstituted sand specimens of required density is a prerequisite for obtaining reliable results. In this paper, two rainer systems, which are capable to prepare homogeneous sand specimens, are introduced. The first is a rainer system with a perforated plate and the second is a portable curtain rainer system. The portable curtain rainer system essentially consisting of a sand storage, flexible hose, a hopper, rigid tubes, and curtain with different opening widths. This study aims to reach a better understanding of the effects of deposition intensity (DI) and height of fall (HF) on the relative density (RD) of reconstituted sand specimens. The uniformity of the sand bed is verified by measuring the relative densities of 20 samples at different locations of the tank. By using a portable curtain rainer system, large uniform sand specimens with a wide range of $\mathrm{RD}=23–96\%$ can be achieved. The results demonstrate that at a lower value of HF, the variation of RD is significant, while it has an insignificant effect on RD for values of $\mathrm{HF}\ge 600\mathrm{mm}$. Furthermore, in order to achieve a dense to very dense sand bed, the DI should be controlled. It was also observed that both systems significantly improve the horizontal and vertical homogeneities of the sand specimens. With an increase in the RD of reconstituted sand specimens, higher repeatability of uniform pluviation was achieved.

Aluminum has become a structural material widely used not only in mechanical and aerospace engineering, but also, more recently, in civil engineering. Because of its structural properties—such as strength, lightness, durability, and fire safety—aluminum, in recent decades, has been increasingly applied to the mechanical and civil engineering industry, including automotive components and large structural constructions. The main objective of the research presented here is to assess aluminum elastic parameters through simple ultrasonic measurements that can be used for in situ civil engineering applications. Experiments were conducted to measure second- and third-order elastic parameters in 6061-T6 aluminum alloy specimens. All measurements were made with the application of simple through-transmission ultrasonic transverse and longitudinal waves in prismatic samples while uniform load was vertically applied. Measurements were taken with all waves transmitted perpendicularly to the applied load direction, shear pulses were polarized in the direction of the load and also perpendicularly to it. Even though the stresses due to the applied loading were relatively low (up to 140 MPa) consistent and continuous variation of the measured ultrasonic velocities with increasing stress was observed. Classical third-order acoustoelastic Murnaghan coefficients $l$, $m$, and $n$ were then calculated using the velocity measurements. In the experiments wave velocities were directly calculated from inquiring ultrasonic pulses transmitted and received using pairs of 500-kHz broadband transducers. The experiments showed the feasibility of applying simple ultrasonic apparatuses to assess third-order acoustoelastic parameters for field applications and can be applied in an axially loaded member of any structural material.

This paper presents the chemical, physical, and mechanical characteristics of carbon fiber–reinforced polymer (CFRP) composite sheets subjected to sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$). Test coupons are submerged in a 5% ${\mathrm{H}}_2{\mathrm{SO}}_4$ solution for up to 6 weeks, and their responses are measured by Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis, and destructive mechanical loading. Also examined are the pH variation of the solution and the microscopic surface textures of the specimens with an increase in exposure time. The aliphatic amine and alkane functional groups of the CFRP are activated by sulfuric acid, including chain scission reactions that cause interfacial deterioration between the carbon fibers and resin. The acid exposure decreases the energy storage and dissipation capacities of the CFRP, as well as its glass transition temperature. The chemically induced damage in the fiber-resin interface is responsible for lowering the load-carrying capacity of the CFRP, along with strain softening. An analytical model is developed based on a Weibull distribution, which quantifies the degree of reliability and hazard associated with acid-damaged CFRP. An environmental reduction factor is calibrated and proposed to replace the standard factor for CFRP strengthening in chemical plants and wastewater treatment plants.

Magnesium sulfate (${\mathrm{MgSO}}_4$) attack is a major problem in geotechnical engineering projects, as exposure to sulfate can affect soil integrity. Lightweight recycled materials such as used vehicle tires can be used to improve the geotechnical properties of soil, while also eliminating landfill. This study investigated the effects of addition of powdered recycled tire (PRT) on the sulfate resistance of cemented clay specimens cured for 7, 14, and 28 days. A total of 74 unconfined compressive strength (UCS) tests were conducted on benchmark (unexposed) and ${\mathrm{MgSO}}_4$-exposed specimens. Addition of PRT improved the peak UCS values ($q_u$) in both conditions. Microstructural analysis by X-ray powder diffraction and scanning electron microscopy was performed on selected benchmark and ${\mathrm{MgSO}}_4$-exposed specimens. Exposure to ${\mathrm{MgSO}}_4$ reduced the generation of hydration products such as calcium silicate hydrate (CSH), resulting in poor connections between PRT and soil particles.

This investigation focuses on studying the effect of using metakaolin (MK) and/or different curing conditions on service life of reinforced concrete exposed to chloride-induced corrosion. Three main stages of service life are studied: corrosion initiation, propagation, and damage periods. The initiation and propagation periods were studied experimentally using small reinforced concrete samples and were also calculated using some available empirical models in the literature for comparison. The experimental variables were the use of MK (0–20%), cover thicknesses (20, 30, and 40 mm), and curing conditions (10 different curing temperatures and durations). The experimental results showed that curing conditions had a clear effect on the initiation and propagation periods but showed a nonsignificant effect (verified by statistical analysis) on the length of the damage period in all tested samples. The incorporation of MK significantly increased both the initiation and propagation periods with little increase in the damage period. The results also indicated that similar trends were found, irrespective of curing condition and cover thickness, from comparing both the initiation and propagation periods using the experimental data and theoretical models.

This study investigated the microstructural evolution of two binders, Pen $60/70$ and PG 76-22, modified with two warm mix asphalt (WMA) additives, Advera (PQ Corporation, Malvern, Pennsylvania) and Sasobit (Sasol Wax, Sasolburg, South Africa), due to aging performed with an accelerated weathering tester. A new long-term aging protocol was utilized, which applies direct aging on the exposed surface of the binders. The aging protocol considers the effects of ultraviolet (UV) radiation (with alternation of UV and dark cycles), presence of oxygen, and temperature. After varying aging durations, different surface morphologies were detected using both optical photos and atomic force microscopy (AFM). New microstructures in the shape of rods, squares, spheres, ellipsoids, and beans and flower or leaf structures were observed on the aged surfaces. The observed microstructures are probably composed of the product of the oxidation and polymerization reactions occurring on the binder surface due to direct aging. The evolution of the microstructure due to direct aging in Advera modified binders was similar to that of the original binders, displaying flower or leaf structures after the longest aging durations. The microstructural evolution observed on the Sasobit modified binders differed from that of the original and Advera modified binders. The discrepancy is attributed to the dissimilar microstructure and chemical composition of the unaged surface, which reacts and forms compounds having different compositions and metastable configurations.

This paper investigates the influence of fuel-resistant polymer on the consistency and performance properties of asphalt binder and hot mix asphalt (HMA) mixtures. The study uses wearing course gradation (nominal maximum size of 19 mm), penetration grade 60/70 bitumen, and Elvaloy reactive elastomeric terpolymers (RET) 4170 as a fuel-resistant polymer. Laboratory tests conducted on unmodified and modified (1–4% Elvaloy) mixtures include an indirect tensile (IDT) strength test and a resilient modulus ($M_R$) test for evaluating cracking potential and stiffness parameters, respectively; a Hamburg wheel tracker (HWT) test for quantifying the rut propensity; and a solubility test to determine the fuel-resistance capacity. The two-level factorial design of the experiment is conducted on the rheological properties of the binder including elastic recovery/complex modulus and creep stiffness values, which suggest that 1% polymer-modified binder (PMB) is least susceptible to high-temperature and low-temperature variations. Performance evaluation reveals that 1% PMB is an optimal proportion of Elvaloy in asphalt concrete mixtures, yielding maximum $M_R$ values (both before and after conditioning in fuel), the lowest rut susceptibility, and high fuel resistance. This research is useful for public aviation/highway agencies and private contractors to minimize the deterioration caused by fuel slippage and to control foreign object debris damage to aircraft.

A new chemical grouting formed by sodium silicate–boric acid mixtures was introduced. Initially, suitable sodium silicate and boric acid contents in the grout mixtures were studied. Gel time, initial viscosity, and syneresis properties of adopted grouts were determined. Strength and permeability of grouted sand specimens having different gradation, relative density, curing time, and condition were investigated. Gel time decreased but viscosity increased as the sodium silicate and boric acid contents increased. Syneresis of grouts increased with the increase in sodium silicate and boric acid contents. As the silicate content of the grout solutions increased, the unconfined compressive strengths of the wet-cured and air-dried specimens increased, but decreased with time as a result of syneresis. The permeability of the wet-cured sand specimens decreased by two to three orders of magnitude after grouting; it increased with increasing silicate content but decreased with increasing in boric acid content.

This paper presents the results of experimental investigations on sand–rubber tire shred mixtures. The sand and rubber tire shreds considered were of uniform fine size ($<2\mathrm{mm}$). Static and dynamic characterization was carried out for pure sand, pure rubber, and sand–rubber tire shred mixtures with rubber content varying 10, 30, and 50% by weight. First, strain-controlled consolidated undrained triaxial tests were carried out to determine static shear strength. Strain-controlled cyclic triaxial tests were then conducted to evaluate shear moduli and damping ratios in the medium to large strain range. Undrained moduli obtained from both experiments were compared. It was found that the mixture with 10% rubber content had the satisfactory static and dynamic properties required for seismic isolation of low-rise buildings.

The objective of this research is to characterize the reduction of volatile organic compounds (VOCs) from bituminous materials resulted from activated carbon. A gas chromatography-mass spectrometer (GC-MS) was used to separate VOC components, and ultraviolet-visible spectrophotometry (UV-Vis) was conducted to quantify the amount of VOCs. Results indicated that activated carbon had an excellent suppression effect on VOCs’ emission process. Adding activated carbon to the bitumen binder did not change its chemical compounds, but did result in a significant reduction of VOCs. The weight of VOCs from the bitumen binder reduced by around 30% when it was modified with activated carbon. Half of VOC emissions can be reduced by introducing activated carbon into styrene-butadiene-styrene (SBS)-modified bitumen. A scanning electron microscope (SEM) showed the high porosity and large internal surface area in the active carbon, resulting in lower VOC emissions when it was introduced into bituminous materials.

This paper puts forward a new hydrophobic silica fume and assesses its contribution to the performance improvement of grouts for stone masonry consolidation. The experiments were conducted using different dosages of hydrophobic silica fume with natural hydraulic lime grouts in the presence of a polycarboxylate-based high-range water reducer. Results revealed that the effects of hydrophobic silica fume on properties of natural hydraulic lime grouts optimize the use of ordinary silica fume. Remarkable rheological performance was obtained in the presence of hydrophobic silica fume: the plastic viscosity and yield stress were reduced compared with the ordinary silica fume. For mechanical strength aspects, it was found that hydrophobic silica fume slightly affected the flexural and compressive strength; however, the values obtained are suitable for the old stone masonry consolidation purposes. It was also observed that water capillarity was substantially reduced as a result of the water-repellent behavior of hardened grouts. This study suggests that the promising effectiveness of this new silica fume for injection grouts opens the way for it to be used in many other applications.

There is a growing need to replace natural aggregates in road construction with new, alternative materials owing to the scarcity of natural resources. On the other hand, generation of huge quantities of waste from industries like iron, steel, copper, and thermal power is resulting in shortages of disposal areas and causing serious environmental pollution. In this paper, important engineering properties—unconfined compressive strength, triaxial shear strength, elastic modulus, resilient modulus, and permanent strain characteristics—of copper slag, fine and coarse steel slag, and blast furnace slag stabilized with fly ash and dolime are investigated for their effective utilization in the base course of flexible pavements, and compared with those of conventional wet-mix macadam (WMM). Deviator stress at failure and elastic modulus of the slag/fly ash/dolime mixes obtained in the present study are much greater than those of the WMM. These mixes also exhibit higher resilient modulus and lower permanent strain than the WMM. The performance of various stress-dependent models for the prediction of resilient modulus is compared, and the model constants of these mixes for a three-parameter model are presented.

The mechanical performance of a typical surface course mixture, modified with two different plastic wastes, both via the wet and dry processes, was evaluated in this study. Water sensitivity, rutting resistance, stiffness modulus, and fatigue cracking resistance tests were used. The results obtained indicated that the polymer-modified mixtures showed similar or improved performance when compared with that of a conventional control mixture produced with a harder virgin grade bitumen, not always available, or available at higher costs, in several countries. Thus, modifying asphalt mixtures with these plastic wastes can be an economical and ecological alternative for paving works. Moreover, the mixtures produced via the dry process showed increased water sensitivity and stiffness modulus properties. This holds out new possibilities for use of polymer-modified mixtures, especially in developing countries, because it widens the possibility of using locally available bitumen, of variable quality, for producing mixtures with higher performance. This can be achieved at real scale with no major extra costs because the dry process does not require modification of typical asphalt plants.

This article presents a method of geopolymerizing black cotton soil (BCS), a type of highly expansive soil, to ascertain its potential use in subgrades. The BCS is stabilized by alkalis of calcium hydroxide [$\mathrm{Ca}{(\mathrm{OH})}_2$] or potassium hydroxide (KOH), and cementitious geopolymers are produced. Parameters of Atterberg limits, maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS), and swelling percentages are measured. The combination of volcanic ash and alkalis reduces the plasticity index greatly ($34.8\%\to 14.2\%$). Potassium hydroxide is found to be more efficient in solidifying the BCS than $\mathrm{Ca}{(\mathrm{OH})}_2$. The swelling percentage of BCS can be decreased from 15.7% to 2.3–4.2%. The mechanical strength has an increasing trend, and the UCS reaches 16.55 MPa after 90 days. Characterizations including X-ray diffraction, scanning electron microscopy, transmission electron microscope, and Fourier-transform infrared spectroscopy are used to reveal the mechanism. In the first stage the soil is fully swelled in the presence of alkaline solutions. Polycondensation occurs in the subsequent stage, and the volume shrinkage is irreversible after geopolymerizaiton. The solidification is found to be related not only to the physical interactions but to chemical bonds as Si-O-Si(Al) or Al-O-Al(Si) constructed by the free species of Si- and Al-, which are verified to be leached from clays. The phase transformation is confirmed by the formation of zeolitic frameworks and the K-illitization observed in the KOH activated specimens.

Microwave technology has been used in asphalt pavement for years, but microwave heating efficiency of asphalt mixtures needs to be improved. In this paper, steel slag particles were modified by a coprecipitation method for improving the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ content on its surface, and then used to completely replace fine aggregates. The electromagnetic properties and microwave heating rates were tested to evaluate the microwave absorption efficiency of the modified steel slag asphalt mixture (MSAM). Also, temperature sensors were used to measure the temperatures of each layer in the mixture slab, for comparing with the data obtained in a numerical model. The results show that the surface temperatures of MSAM increase to 74°C, and the internal temperatures are 10–20°C higher than the surface ones after microwave heating for 120 s, which is 74.4% higher than the basalt asphalt mixture (BAM). The tested temperature distributions are in good agreement with those of simulation, suggesting that the study is very promising and is expected to promote the microwave heating technology in asphalt pavements.

The preferable way to monitor structural behavior is to measure the actual stress in the structural members. Unfortunately, stress relieving by cutting holes or slots has been the only method applicable to date for measuring the in situ stress in concrete members. Other methods such as strain gauges can only measure the change of stresses and are time consuming. Investigations have been made to find nondestructive methods for stress measurement in concrete. The progress made on stress evaluation through acoustic-wave analyses is reviewed in this paper. While the traditional elastic–acoustic waves are able to detect stress changes in concrete, it is only applicable in the elastic range and is not suitable to most field conditions. Alternatively, the coda-wave interferometry and nonlinear acoustic waves are sensitive to the microstructural changes in concrete and provide potential field applicability for in situ measurements. These coda-wave and nonlinear parameters may be used as a qualitative/quantitative indicator to microscale-damage diagnostics and stress changes.

This paper presents the development of nanomodified fiber-reinforced cementitious composite (FRCC) mixtures. A total of seven mixtures were prepared using general use cement and a constant dosage of slag (40% replacement by mass of the base binder). Also, nanosilica was incorporated in six mixtures at a dosage of 6% by mass of the base binder, whereas one mixture was without nanosilica as a reference. Basalt fiber (BF) pellets (made of basalt fibers encapsulated by polyamide resin) were used to produce BFRCC. Three mixtures had BF pellets with different lengths (25 mm, 36 mm, or both), whereas two mixtures incorporated BF pellets and polypropylene fibers. The performance of the cementitious composites was evaluated in terms of compressive and flexural strengths and toughness. In addition, the bond strength of glass fiber-reinforced polymer (GFRP) bars embedded in either the cementitious composites or normal-strength concrete was determined. Test results revealed that adding 2.5% by volume of 36-mm-long BF pellets to the mixture achieved the best performance. This BFRCC favorably showed high residual flexural strength and ductility compared to those of other mixtures. Furthermore, it achieved better bond strength to GFRP bars compared to both the nanomodified mixture without fibers and normal strength concrete.

This paper uses information collected over several years to determine where the Cantabro test usefully characterizes dense graded asphalt (DGA). The Cantabro mass loss (CML) procedure is simple, expedient, and has been used for open graded materials for years. A database of approximately 1,200 measurements was analyzed alongside information from the literature to assess the usefulness of the CML procedure for DGA because this is not nearly as common as for open graded materials. Findings showed that several of the factors leading to durable mixes have been cited in the literature for some time but that a mix test to routinely assess all factors simultaneously has not found its way into routine practice. A mix test of this nature is needed now more than ever given that one of the main challenges is to produce mixes better balanced between rutting and cracking. Analysis showed that the Cantabro test detected the following items known to affect performance: binder grade, presence of polymer, difference between ground tire rubber and SBS modification, aggregate type, reclaimed asphalt pavement (RAP) content, density (air voids), volume of effective binder, and aging.

This paper presents a new type of discrete reinforcing element for concrete produced from either waste or new pultruded fiber-reinforced polymer (FRP) composite materials. These elements, referred to as FRP-Needles, are rigid, long, and low in aspect ratio, and have distinct physical and mechanical differences from macrofibers used in concrete. The FRP-Needles used in this study were produced by cutting FRP reinforcing bar (rebar) production scrap with nominal diameter of 6 mm into rod-shape elements with length of 100 mm (aspect ratio of 17). FRP-Needles were incorporated in concrete to replace 5 and 10% of coarse natural aggregate (NA) by volume. The needles did not reduce the workability or stability of concrete. The dispersion and orientation of FRP-Needles in concrete were relatively uniform. The 5 and 10% replacement of NA with FRP-Needles increased the splitting tensile strength of concrete by 22 and 33%, respectively, while reducing the compressive strength by only 5 and 9%. The incorporation of FRP-Needles in concrete resulted in significant increases in postfailure toughness of concrete in both compression and tension. In a parallel study, FRP recycled aggregate (FRP-RA) was produced by cutting scrap rebars into cylindrical pieces with aspect ratio of 1. FRP-RA was incorporated in concrete with the aforementioned dosages to observe the effect of geometrical characteristics of FRP elements on the studied mechanical properties of concrete. The improvements achieved by using FRP-Needles were not observed when FRP-RA was incorporated in concrete.

Concrete is well known for its capacity to sequester carbon dioxide (${\mathrm{CO}}_2$) through carbonation curing. If carbonation mixing can be used to introduce ${\mathrm{CO}}_2$ during concrete mixing, the process is able to enhance the carbon capture and storage capacity of concrete and makes the technology available to both precast and cast-in-place concretes. This paper studies the effect of carbonation mixing on ${\mathrm{CO}}_2$ uptake and strength gain of cement paste, which is the key carbon-reactive ingredient in concrete. Three mixing methods were investigated: (1) normal air mixing, (2) carbonation mixing, and (3) hybrid mixing with carbonation mixing first, followed by normal air mixing. Two curing methods, air curing and carbonation curing, were also studied to examine the effect of carbonation mixing on curing. It was found that carbonation mixing could increase the ${\mathrm{CO}}_2$ uptake but decrease the strength gain. The reduction in strength by carbonation mixing was caused by the formation of carbonate coating on cement particles. The property can be improved if air mixing is introduced right after carbonation mixing.

This paper presents a laboratory study on the engineering properties of marine clay admixed with siliceous fly-ash-blended cement and ordinary portland cement (OPC) through an unconfined compression test, split tensile test, bender element test, and isotropic compression test. Specimens with 20–100% of cement by weight of dry soil and 100–133% of water by weight of soil and cement solid-cured for 7–150 days were investigated for both fly-ash–cement-admixed clay and OPC-admixed clay. The results showed that the short-term strength gain of marine clay admixed with fly-ash-blended cement (FAC) is significantly lower than that of OPC-admixed clay. However, the long-term strength gains are similar, with the fly-ash–cement-admixed clay manifesting more sustained gains for curing periods beyond 28 days. The difference in the rate of strength gain between FAC-admixed clay and OPC-admixed clay is attributed to the greater prominence of the pozzolanic reaction in the fly-ash-blended cement. In order to reflect the slower initial rate of strength gain arising from the pozzolanic reaction, a generalized hyperbolic strength-gain-time function was postulated for fly ash. By superimposing the individual strength contributions of the OPC and fly ash, a semiempirical relationship for the gain in strength with time for marine clay treated by fly-ash-blended cement is obtained, which gives good agreement with the measured data. Other properties studied herein include isotropic yield strength, tensile strength, and small-strain modulus. The results show that all these properties are well-correlated to the unconfined compressive strength by linear function regardless of whether OPC or fly-ash-blended cement is used.

The present paper thoroughly investigates the effects of mix design with various water-to-binder (W/B) ratios, types of mineral admixture and types and sizes of local sands on the tensile ductility of engineered cementitious composites (ECC). White and red dune sands—denoted W and D, whereas their sieved forms are denoted SW and SD, respectively—were collected from the Arabian Desert, the second largest on the earth. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were separately used as mineral admixtures in the production of ECC. The development of ductility in ECC mixtures incorporating FA was found to reduce with curing time, whereas it was found to increase with GGBFS. An ECC mixture containing 62% GGBFS with W/B ratio of 0.35 has delivered the best fresh and hardened properties with strain capacity of 4.2% and tensile strength of 5.2 MPa at 28 days. Water sorptivity of fully cracked dune sand–based ECC mixtures was lower than that given by normal concrete. It is concluded that dune sand–based ECC mixtures have provided comparable results to the reference silica sand–based ECC mixtures.

This paper presents a novel extended digital image correlation (EDIC) method for mapping multiscale damage in concrete. The EDIC method is developed based on the distance transformation algorithm, which extends the capability of current digital image correlation (DIC) in detecting microdamage. Applications of the EDIC in mapping multiscale damage in concrete specimens are given in this paper, which proves the capability of the EDIC in detecting such damage. This novel EDIC technology can be used for further research on material damages and for improving safety assessment through detection of microdamage in industrial applications.

Rubberized asphalt has been widely used for extending the service life of pavement. Understanding the weathering mechanism of rubberized asphalt is useful for selecting appropriate rubberized asphalt. This paper examines the weathering process of two typical rubberized asphalts composed of crumb rubber modified asphalt (CRMA) and terminal blend rubber asphalt (TB) by characterizing the rheological and structural evolution of the aged asphalt. Dynamic shear rheometer analysis, infrared spectroscopy, and gel permeation chromatography are used to analyze this evolution. The results show that significant changes occur in the chemical structures and rheological properties of the two rubberized asphalts throughout the weathering process. Although the stiffness of CRMA and TB obviously increases during weathering, their increasing trends are distinct from each other. The chemical evolutions of CRMA and TB during the weathering process differ significantly in terms of variations in molecular weight and carbonyl index.

This study evaluated the results of preparation conditions for the production of an alkali-activated binder (AAB) based on a binary mixture of tailings from tungsten mine waste (TMW), and waste glass (WG) activated with a mixture of sodium silicate (SS) and sodium hydroxide (SH). A 40% by weight WG increased the amorphous nature of the binary blend by 21% without initiating the alkali-silica reaction. The SS-SH activator solution was subjected to a variation of mixing times, and its sensitivity was measured using temperature monitoring and Fourier transform infrared spectroscopy (FTIR). After 20 min of mixing, the SS-SH activator solution showed a 3.13°C reduction in temperature and a 21.4% increase in unbound water content, and as a result imparted a 26% drop in the mechanical strength of TMW-WG AAB at 28 days. The TMW-WG AAB was also determined to develop the highest compressive strength when cured at 80°C for 24 h in sealed conditions. The following conditions, supported by X-ray diffraction (XRD) and FTIR, are responsible for the most significant dissolution of the aluminosilicate oxides.

Concrete porosity and its interconnection are crucial aspects that influence durability. Taking into account that moisture is required for many concrete deterioration processes, water absorption is a measure that can essentially evaluate concrete quality and its resistance. Standardized laboratory methods exist to measure water absorption. It is also potentially possible to perform simple and rapid nondestructive water absorption tests on placed concrete; however, it is impossible to provide standard conditions for in situ measurements. Because water absorption is strongly affected by temperature as well as relative humidity (RH), on-site water absorption measurements require cautious interpretation. This study addresses the issue by investigating water absorption in different thermal and moisture conditions. Concrete water absorption tests were performed using a commercial test device over a range of RH and temperature levels. It was observed that water absorption increases significantly with decreasing moisture content and increasing environmental temperature. Surface RH was found as an accurate and practical indicator of concrete moisture content. Most notably, outdoor exposure measurements confirmed that using a temperature correction, field results correlated very well to laboratory predictions making the test reliable for quality control purposes.

The degradation of synthetic fibers derived from postconsumer wastes and used in fiber-reinforced cement mortars was studied. Polyethylene terephthalate (PET) and high-density polyethylene postconsumer bottles were immersed in an alkaline medium of a 1-M solution of sodium hydroxide and portland cement paste. Then, the fibers’ surfaces were analyzed by scanning electron microscopy (SEM). This study showed that the fibers have a progressive surface deterioration over time when immersed in either of the two media. Degradation of fibers immersed in pozzolan-portland cement pastes was also observed. The results from the degradation process of these fibers show that it was stronger when they were immersed in the portland cement system ($\mathrm{pH}=12.9$), although the pH value was lower than that of the NaOH solution ($\mathrm{pH}=13.8$), suggesting that the degradation process in portland cement also depends on the formation of solid hydration products. The preliminary results of this study show overall good behavior of the studied fibers. This behavior generally improves when using pozzolans. Considering that fibers and pozzolans are obtained from wastes, and therefore have low economic and environmental costs, the possibility of using these materials in developing countries should be considered. The use of these wastes would, on the one hand, improve the properties of construction materials, and on the other, enable proper management of waste that could otherwise eventually pollute the environment.

This work aims to optimize the transport properties of high-volume fly ash (HVFA) mortars that replace Portland cement with a Class C fly ash at 60% by weight. Ten chemical admixtures (five nonpolymers and five polymers) previously reported to improve the early-age strength or water resistance of concrete were investigated for their effects on the HVFA mortars. A total of 26 mortar mixtures were designed and tested, based on a statistical design to explore the potential synergistic effects among the polymeric admixtures and the nonpolymeric admixtures, respectively. At the age of 28 days, the compressive strength, splitting tensile strength, and water sorptivity of all mortar mixtures and the gas permeability of six selected mixtures from each group were tested. In addition, the surface free energy and pore size distribution of the selected mortars were obtained in the effort to correlate with water sorptivity and gas permeability, respectively. The predictive models built on the results of designed experiments suggest that if used individually, tributyl phosphate, hydroxypropyl methyl cellulose, and hydroxyl terminated polysiloxane are the three admixtures that can effectively reduce the water sorptivity of HVFA mortars. For the six selected HVFA mortars, those containing polymeric admixtures exhibited a significantly lower gas permeability coefficient than those containing nonpolymeric admixtures. The water sorptivity of HVFA mortars was mainly affected by the microstructure of mixtures rather than their surface free energy. The nonpolymeric admixtures worked better in refining the pore structure in the HVFA mortars and reducing the critical radius than the polymeric admixtures.

The nonuniform distribution of reclaimed asphalt pavement (RAP) in asphalt mixtures can affect stiffness values of RAP mixtures and their field performance in asphalt overlays. This study develops a method that uses finite-element (FE) analysis of the quasi-microstructure of RAP mixtures to predict their stiffness values and evaluate the performance of the asphalt overlays that contain RAP mixtures. Laboratory experiments are conducted to determine the dynamic modulus values of the corresponding RAP mixtures, which are compared with the predicted stiffness values. The results show that the proposed quasi-microstructure analysis is a reliable approach to predict stiffness values of RAP mixtures and can investigate the direct correlation between RAP distributions and the stiffness values under indirect tensile (IDT) test quantitatively. The quasi-microstructure analysis of RAP mixtures’ overlays shows that the addition of RAP in asphalt mixtures can improve the rutting resistance but significantly increases the cracking potential. The proposed methodology offers a promising and cost-efficient approach to analyze and design RAP mixtures.

Internally cured concrete made with prewetted lightweight aggregates (LWAs) has a risk of segregation because of floating LWAs in the process of vibration. Such risk can be reduced by applying internal curing in self-compacting concrete, because it can avoid vibration or rodding processes. In this study, internally cured self-compacting concretes with fine or coarse LWAs were prepared with a replacement level of 20 and 40% by volume of normal-weight aggregates. A segregation resistance test was performed to quantitatively evaluate the floating of LWAs in self-compacting concrete. The effectiveness of internal curing was evaluated in terms of workability, compressive strength, autogenous shrinkage, and transport properties (i.e., water absorption, water desorption, and chloride resistance). Transport properties were also examined for internally cured mortar, which has identical ingredient proportions to the corresponding concretes used for comparison. The results showed that internal curing is useful in reducing the autogenous shrinkage of self-compacting concrete, and no segregation was observed for the fresh concretes. It was also found that the fine LWAs exhibited a better performance in reducing autogenous shrinkage and improving the transport properties compared with the coarse LWAs. The comparison of water absorption test results between a mortar and its corresponding concrete reveals that an increase in the volume fraction of normal-weight aggregates may decrease the effectiveness of internal curing.

An accelerated leaching experiment, using 6M ${\mathrm{NH}}_4\mathrm{Cl}$ solution, on specimens of pure cement paste, binary cement paste with different fly ash contents (20, 30, and 50%), and ternary cement paste with the replacement of 10, 20, and 30% fly ash by slag was conducted to investigate the influence of fly ash and its partial replacement by slag on the leaching behavior of blended cement pastes. The leaching depth, porosity, calcium-silicon mass ratio ($\mathrm{Ca}/\mathrm{Si}$), phase composition, and microstructure morphology of the specimens were characterized by using the phenolphthalein indicator, saturation-drying weighing, scanning electron microscopy with energy dispersive spectrometer (SEM/EDS), and X-ray diffraction (XRD). Results show that higher fly ash content mixed in pure cement paste causes a greater leaching depth, with slower microstructure deterioration, lower porosity increment, and reduction of $\mathrm{Ca}/\mathrm{Si}$ and calcium hydroxide content. Higher replacement of fly ash by slag in binary cement paste leads to a more compact microstructure and higher $\mathrm{Ca}/\mathrm{Si}$ after complete leaching of calcium hydroxide. The fly ash can reduce the leaching degree of pure cement paste but accelerate its leaching process; however, the partial replacement of fly ash by slag in blended cement paste not only improves its compactness and the stability of its microstructure, but also slows down its leaching process. The ternary cement paste with a water-binder ratio of 0.45, 20% fly ash, and 30% slag has the optimum leaching resistance.

The mechanical property characterization of dam concrete is a challenging task mainly due to the use of large aggregate sizes. The properties of dam concrete are often evaluated from wet-screened concrete tests using standard specimen sizes. A physically based relationship between dam concrete and wet-screened concrete strength properties is currently unavailable. A prediction methodology is proposed that can be used to obtain the compressive and the splitting tensile strength of dam concrete by taking into account the wet-screened strength results, the effect of the specimen dimensions, and the effect of the maximum size of aggregate. The predicted results are compared with test results available in the literature and with test results recently obtained during the construction of the Baixo Sabor dam. It is shown that the proposed prediction tool can be used to obtain accurate estimates of dam concrete strength.

Sugarcane bagasse ash (SCBA) is an industrial by-product generated in large quantities from sugar industries employing the cogeneration process. It is commonly disposed of in landfills. The use of cogeneration plants, and subsequently the quantity of ash generated and disposed, has increased significantly in India and other developing economies. Moreover, disposal of sugarcane bagasse ash causes environmental pollution and reduction of useful land area. A number of earlier research studies have reported on the excellent pozzolanic characteristics of sugarcane bagasse ash in concrete. The present study is focused on the performance evaluation of sugarcane bagasse ash as an ingredient in construction materials such as alkali-activated concrete, paver blocks, and unburnt bricks. Results from the study showed significant improvement in the characteristics, specifically strength and durability of bagasse ash blended specimens. Sugarcane bagasse ash and slag-based ambient-cured geopolymer specimens showed enhancement in compressive strength and workability in comparison with slag-based geopolymer. No efflorescence was observed in SCBA-based unburnt bricks, but water absorption in SCBA unburnt bricks was higher compared with fly ash bricks. Sugarcane bagasse ash blended paver block specimens exhibited significant resistance against water penetration and sorption compared with control specimens.

To improve the cracking resistance of asphalt mixtures with high recycled asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) contents, one approach is to use a recycling agent (RA) (i.e., rejuvenator) to potentially restore the performance properties of the aged binder. This project was conducted to evaluate the effect of recycling agents on the laboratory test results and field performance of mixes with high recycled contents. The field study consisted of three mixtures: A control mix containing 20% RAP and no RA, and two experimental mixes with different rejuvenators containing 25% RAP and 5% RAS. The control mix was produced at a typical hot-mix asphalt (HMA) production temperature [149°C (300°F)], while the experimental mixes were produced as warm-mix asphalt (WMA) [129°C (265°F)]. Two rejuvenators were used in the study. This paper presents data collected during the construction of the test sections, laboratory test results, and early field performance (approximately two years). Compared to the control mix, both the experimental mixes with 25% RAP plus 5% RAS showed similar rutting resistance but significantly lower resistance to cracking based on lab test results and field performance data. The lab test results, especially for overlay test (OT) and Illinois flexibility index test (I-FIT), are in agreement with the field cracking performance of these mixes—the experimental mixes with OT cycles below 125 and flexibility indexes below three cracked within two years in the field. Thus, further research can be conducted to refine these criteria for use in mix design and/or quality control (QC)/quality assurance (QA) to avoid premature mixture cracking in the future.

In recent years, the use of recycled plastic aggregate (RPA) as an alternative aggregate material has been considered to lower the environmental impact of both concrete and waste plastics. Recycled plastic aggregate concrete (RPAC) is now recognized as a highly promising technology that can contribute to resource efficiency in the construction industry. In this paper, the first experimental study on the properties of concretes manufactured using recycled polypropylene (PP) coarse aggregates is presented. Eight batches of concretes were manufactured with different RPA contents. The effect of RPA content on the compressive strength, elastic modulus, flexural strength, splitting tensile strength, workability, and fresh and hardened density of each batch is studied. Although the results illustrate that the mechanical properties of RPACs are lower than those of concretes produced with natural aggregates, when RPA content is below a certain threshold, this difference is not excessive. These results suggest that the method investigated in this study can offer an environmentally sustainable avenue for the use of waste PP. This study is also the first to investigate the compressive behavior of RPACs subjected to temperatures around the melting point of RPAs. The compressive strength of RPACs decreases significantly when exposed to elevated temperatures, with specimens having higher RPA contents experiencing greater reductions.

The new generation of fiber-reinforced cementitious composites made with polyvinyl alcohol fibers and high amounts of fly ash shows advantageous mechanical properties in terms of very high tensile strain capacity and ductility. The challenge that remains is to establish pertinent new design rules and analysis procedures and to adapt existing ones specifically tailored to structures made of these materials. In this direction, four-point bending tests were conducted on scaled beam specimens considering several values of shear span aspect ratio in order to determine the behavior of this novel ductile concrete in shear. Tests were conducted on mixes with and without longitudinal and shear reinforcement. It was found that the fiber content had a significant effect on all aspects of mechanical behavior, in terms of strength and ductility. The strength of fiber-reinforced composite beams with longitudinal reinforcement in shear and flexure was interpreted using mechanistic models that rely on the classical beam theory and the strut-and-tie approach. The independent contributions to shear resistance of the fiber-reinforced web, longitudinal reinforcement anchored beyond the critical shear crack, and transverse reinforcement were calibrated to the experimental results in order to establish procedures for evaluating the structural performance of this innovative cementitious material.

Cold-mix asphalt (CMA) is considered a convenient and rapid solution for pavement pothole repair projects. Despite the wide use of CMAs, reliable procedures for quality control and screening of different types of these mixes are still not available. This paper studies and compares the engineering properties, permanent deformation, and moisture resistance of nine types of CMAs. For this purpose, three different well-known experiments, namely Marshall stability, indirect tensile strength (ITS), and Hamburg wheel-tracker (HWT) tests, were performed on each oven-cured and ambient-cured CMA sample. The results mainly showed that the rutting resistance of densely-graded CMA samples is considerably higher than that of the open-graded samples. The dust-to-binder ratio seems to have a high correlation with the moisture susceptibility of dense-graded CMAs, whereas the percentage of coarse aggregates plays an important role in that of open-graded CMAs.

This paper experimentally investigates the mechanical properties of rotary veneers peeled from small-diameter hardwood plantation logs, recovered from early to midrotation subtropical hardwood plantations. The study aims at providing essential probabilistic data needed to ultimately predict the capacity and reliability of veneer-based composites structural products [such as laminated veneer lumber (LVL) and plywood] from characteristics that can be measured in line during manufacturing. Two species planted for solid timber end-products (Gympie messmate, Eucalyptus cloeziana, and spotted gum, Corymbia citriodora) and one species traditionally grown for pulpwood (southern blue gum, Eucalyptus globulus) were studied. The compressive and tensile modulus of rupture (MOR) of the veneers, parallel to the grain and for veneer-based composite applications, were experimentally investigated. Results show that the compressive MOR for all species typically ranges from 30 to 50 MPa [for modulus of elasticity $(\mathrm{MOE})<\mathrm{12,000}\mathrm{MPa}$] to 60 to 90 MPa (for $\mathrm{MOE}>\mathrm{22,000}\mathrm{MPa}$). The tensile MOR is typically lower than or in the range of the compressive MOR for MOE less than 12,000 MPa, while for larger MOE ($\mathrm{MOE}>\mathrm{22,000}\mathrm{MPa}$) tensile MOR greater than 140 MPa were observed. The total knot area ratio (tKAR) of the veneers is also analyzed and Weibull distributions were found to provide a good characterization of the statistical repartition of the tKAR value along the length of a veneer sheet. For each species, equations to best predict a veneer MOR from its measured MOE and tKAR value are derived and fit the experimental results with a coefficient of determination between 0.63 and 0.74. The variability of the MOR of each species was accurately modeled by Weibull distributions, with the distribution parameters determined based on the experimental data. Results shown that southern blue gum and Gympie messmate are the most and least sensitive species to size effects, respectively.

This paper presents an experimental study on geopolymer synthesized with class F fly ash (FA) and low-calcium slag (SG). Geopolymer specimens were produced using FA and SG at different relative amounts ($\mathrm{FA}/\mathrm{SG}=0/100$, 25/75, 50/50, 75/25, and 100/0), NaOH solution at different concentrations (7.5, 10, and 15 M), various curing times (1, 2, 4, 7, 14, and 28 days) and curing temperatures [25 (ambient), 45, 60, 75, and 90°C]. The unit weight and uniaxial compressive strength (UCS) of the geopolymer specimens were measured. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) were also performed to characterize the microstructure and phase composition of the geopolymer specimens. The results indicate that the incorporation of SG not only increases the UCS of the geopolymer specimens but also decreases the initial water content and, thus, the NaOH consumption at the same NaOH concentration required for geopolymer production. In addition, the inclusion of SG increases the unit weight of the geopolymer specimens, simply because SG has a much greater specific gravity than FA. The results also show that the strength of the FA/SG-based geopolymer develops rapidly, with a major portion of the UCS (approximately 70%) gained within only 2 days and no obvious strength gain after 7 days. The optimum curing temperature (the curing temperature at which the maximum UCS is obtained) at a FA/SG ratio of 50/50 is around 75°C. This research contributes to the knowledge of geopolymers produced from a combination of source materials and promotes the reuse of wastes through geopolymerization.

The aim of this study is to investigate the durability of geopolymer mortars based on waste-glass powder (WGP) and calcium aluminate cement (CAC) exposed to acid attack. Geopolymer specimens were prepared by a combination of WGP and CAC activated by an aqueous solution of sodium hydroxide and sodium silicate and were cured under hydrothermal conditions. The prepared specimens were immersed in sulfuric and hydrochloric acid solutions ($\mathrm{pH}=1$) for 6 months, and their residual compressive strength and several key durability parameters were assessed and compared to those of portland cement and high alumina cement mortars as control specimens. Microstructural and compositional changes in the geopolymer samples were studied using scanning electron microscopy, X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy. The results showed that the acid resistance of geopolymer mortar against both acid solutions was comparable to the control mortars, as indicated by the relatively lower strength loss and lower mass change. The microstructure of the geopolymer after acid exposure, however, possessed significant microcracks in the near-surface region, leading to a higher porosity and a lower strength. XRD results revealed the formation of gypsum crystals due to the reaction between sulfuric acid and calcium from the geopolymer gel.

The performance of grouts made using oilwell cement is markedly different above 90°C than at lower temperatures, and the rapidity with which grouts thicken can cause failures in well cementing. One grouting application in which such temperatures are encountered is deep borehole disposal (DBD). DBD is a concept for disposing of high-level radioactive wastes where the temperature and pressure will be 90–140°C and 30–50 MPa, respectively. In developing DBD grouts, a number of issues have been identified that will be of interest to well-cementing organizations. (1) The type of retarder used to delay grout thickening above 90°C is of extreme importance, and should be selected based on local temperature, pressure, and geochemical environment. Addition level might vary considerably depending on the retarder used. (2) Temperature and pressure will shorten the time for grouts to thicken, particularly the former. Water content will also affect grout properties such as consistency, viscosity, and flow. (3) The retarder may not influence hardened grout composition, which suggests that only the time at which the cement hydration reactions occur is influenced.

Certain chloride-based deicing salts can react with calcium hydroxide in cement paste to form calcium oxychloride. Calcium oxychloride formation results in expansive pressures that damage concrete. This study examines the use of undensified silica fume as a potential method to mitigate calcium oxychloride formation in cement paste. Cement pastes were prepared with four different volume replacement levels of silica fume and three different water–to–cementitious material ratios. Thermogravimetric analysis and low-temperature differential scanning calorimetry were performed at various ages to quantify the amounts of calcium hydroxide and calcium oxychloride. Thermodynamic modeling was used to compute the phase distribution of products formed. In pastes containing silica fume, the amounts of calcium hydroxide and calcium oxychloride generally decrease as the amount of silica fume increases and as the sample ages. However, even when 10% of the cement volume was replaced with silica fume, calcium oxychloride formed in relatively large amounts. Therefore, the use of undensified silica fume to mitigate calcium oxychloride damage appears to require greater silica fume replacement levels than those that are currently used (3–10%). This conclusion is valid in spite of calculations from thermodynamic modeling based on calcium hydroxide amounts showing that the silica fume degree of reaction is moderate to high (30–85%).

Properties of raw dredged material (RDM) stabilized with self-cementing Class C fly ash (FA) were evaluated for beneficial use in geotechnical construction applications. Emphasis was placed on evaluating effects of curing time and fly ash content on index and engineering properties relevant to pavement construction. RDM samples were blended with 10, 20, and 30% FA and cured for 2 h, 7 days, and 28 days. Fly ash stabilization reduced plasticity and improved the engineering properties of the stabilized dredged material (SDM). Increasing FA content increased maximum dry unit weight and reduced optimum water content for compaction. Unconfined compressive strength ($q_u$) increased with FA content and curing time. The effect of curing time on $q_u$ was more significant at higher FA content. Freeze-thaw cycles only reduced the strength of SDM specimens by 5% on average, indicating that SDM was durable to freeze-thaw. Analytical relationships were developed to predict Atterberg limits and $q_u$ of SDM at different fly ash contents and curing times. The California bearing ratio (CBR) for the SDM ranged from 10 to 20, which is comparable to compacted silty sand or sand and rates as fair to good for pavement subgrade. The resilient modulus ($M_R$) increased significantly with FA content and varied between 35 and 83 MPa, which is comparable to gravel or crushed stone and rates as good to excellent for subgrade. Results indicate that low-strength dredged materials stabilized with Class C fly ash are viable for beneficial use as pavement subgrade material.

This paper presents the results of an experimental study on the durability characteristics of lightweight concrete produced from agricultural waste oil palm shell (OPS) pretreated with polyvinyl alcohol (PVA) as full replacement material for conventional coarse aggregates. The tests conducted to assess the durability characteristics of PVA-treated OPS concrete are water absorption, volume of permeable voids, sorptivity, and 90-day salt ponding test in which the chloride diffusion coefficient and time to corrosion initiation are determined. The effects of different curing conditions on the durability characteristics of PVA treated OPS concrete are discussed and the results obtained are compared with raw (untreated) OPS concrete. Results show improvements in terms of water absorption, volume of permeable voids, and resistance to chloride penetration of PVA-treated OPS concrete compared with raw OPS concrete under all types of curing conditions used.

The paper deals with the improvement of adhesion, abrasion resistance, and aging of polyurethane coatings made with polycarbonate diol (PCD) intended for internal pipelines. The influence of the polyol nature on the properties and aging resistance of polyurethane coatings synthesized at laboratory scale using polyether glycol and PCD is determined. The use of PCD or mixtures of 50% by weight polyether glycol (PTMEG) and 50% by weight PCD in the synthesis of the polyurethane coatings strongly reduces the amount of material removed by abrasion. On the other hand, the use of 40% by weight PTMEG and 60% by weight PCD increases the mechanical properties of the polyurethanes and their pull-off strength values in joints made with steel substrate. After aging by immersion in water at 70°C for two weeks, the reduction of pull-off strength in the joint made with the polyurethane made with PTMEG and with a PCD and PTMEG mixture is similar but the loci of failure are different. Only the polyurethane coating prepared with 40% by weight PTMEG and 60% by weight PCD mixture shows a cohesive failure in the coating.

The susceptible characteristics of gypseous soil with variations in water content pose several engineering problems due to volume change behavior. A series of oedometer tests have been performed to understand the swell strains and compressibility of soil containing varying gypsum content after curing for different periods. The swell strains of both uncured and cured samples increase with an increase in gypsum content up to 2% and decrease with a further increase in gypsum content. However, the swell strain of soil with any gypsum content decreases with an increase in the curing period. The compressibility of the soil increases with an increase in gypsum content but decreases after curing for longer periods. However, the effect of curing is minimal on the compressibility of soil containing a higher gypsum content. The permeability of gypseous soil increases along with an increase in the total change in void ratio upon loading. Detailed microanalyses have revealed that an increase in the swell strains and compression in soil with lower gypsum is due to the formation of zeolite and a weaker cemented matrix. However, the presence of unreacted gypsum particles in the soil matrix and the suppression of zeolite with the formation of cementitious compounds reduce the swell strains and compression with higher gypsum after curing for longer periods.

Tensile properties of different sizes of dovetail connections made from Larix kaempferi and Pinus koraiensis are evaluated using three different methods. Dovetail connections are prepared at different sizes ($120\times 120\mathrm{m}\mathrm{m}$, $180\times 180\mathrm{m}\mathrm{m}$, $180\times 240\mathrm{m}\mathrm{m}$, and $240\times 240\mathrm{mm}$) and three specimens of each size are tested for their tensile properties. Initial stiffness, yield load, yield displacement, and ductility ratio values determined according to the three methods are different. However, the trends of those values with an increase in size are similar. The slope of the initial load-displacement curve is highly affected by the gap of the dovetail connection. Yield load and yield displacement values of dovetail connections are highly subject to the initial slope depending on the method used.

This paper aims to investigate the effect of fine aggregates on properties of magnesium potassium phosphate cement (MKPC) mortar. River sand (RS), limestone sand (LS), and mixed aggregates (RS/LS mixture) were used to prepare MKPC mortar, respectively. Then, the fluidity, mechanical strength, shrinkage deformation, and hydration temperature of different MKPC mortars were tested. Compared with MKPC mortar prepared using RS, MKPC mortar prepared using LS has significantly higher 60-day flexural strength, slightly higher 60-day compressive strength and 60-day shrinkage strain, and lower 60-day flexural strength residual ratio under water curing condition. Compared with MKPC prepared using LS, MKPC mortar prepared using mixed aggregates has higher 60-day compressive strength, higher strength residual ratio under water curing condition, and lower 60-day shrinkage strain. Also, the effect of the ratio of aggregates to a binder (MKPC) on properties of MKPC mortar is investigated. Results show that the optimal aggregates to binder ratio for MKPC mortar prepared using mixed aggregates ($W_{\mathrm{LS}}$ to $W_{\mathrm{RS}}$ ratio is $2:1$) is $1.5:1$, resulting in high strength and low binder content of MKPC mortar. When $W_{\mathrm{LS}}$ to $W_{\mathrm{RS}}$ ratio is $2:1$ and aggregates to binder ratio is $1.5:1$, 60-day flexural and compressive strengths of MKPC mortar are greater than 40% higher than that of MKPC mortar prepared using RS; 60-day flexural and compressive strength residual ratios of it are above 80%, and its shrinkage deformation is close to that of MKPC mortar prepared using RS.

In order to minimize the binder content in composite lunar “cement,” this paper uses JSC-1A lunar soil simulant and unsaturated polyester resin (UPR) to produce low-binder-content composite. Important system parameters such as compression pressure, compression duration, vibration, loading rate, loading number, and initial grain size distribution are analyzed. The most critical control variable is the compression pressure: at $\sim 350\mathrm{MPa}$, the binder content is reduced to 6.5–8.7% by weight and the flexural strength is approximately 30–40 MPa. This research is important for in situ resource utilization for future lunar base construction and expansion.

An acrylamide-based chemical grouting system has been developed that allows users to initiate the curing process on demand. After heating a localized area, the curing reaction propagates through the grout via a process called frontal polymerization. The system was engineered so that the grout would eventually cure without user input, as with current systems. This cure-on-demand technology enables users to work with systems that have a long pot life, but gives them the flexibility to be able to cure sections of grout at different times. By adjusting the amounts of several components, pot lives ranging from a few minutes to 6 h have been achieved. The speed of propagation of the curing front can also be varied, with $2\mathrm{cm}/\min$ as an average rate. The compressive strength of sand grouted with the cure-on-demand system was determined to be four times higher than that of samples prepared using a typical commercially available grout formula.