Journal of Materials in Civil Engineering

Some researchers suggest the use of residual rice-husk ash (RHA) finely divided as a mineral addition to cement, despite the reduced content of amorphous silica compared to RHA produced by controlled burning. This article presents an investigation of the pozzolanic activity of residual RHA A and residual RHA B, with high and low contents of amorphous silica, respectively, showing different particle size distributions. Scanning electron microscopy (SEM), ${}^{29}\mathrm{Si}$ magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and determination of amorphous silica through the rapid analytical method were used for the microstructural characterization of the RHA samples. The RHA B with low content of amorphous silica increases the consumption of calcium hydroxide when its particle size decreases.

Parallel strand lumber (PSL) is a composite made of oriented wood strands that have been glued and compressed together. Its market share in the residential construction industry is considerable, being used primarily as main load bearing members such as beams and columns. Unlike the fast-paced market growth of these products, computational development has been slow. The highly heterogeneous mesostructure of this material must be known and quantified in order to develop advanced computational tools for limit state analysis of PSL. Void heterogeneities play an important role in determining the failure modes and strength of PSL, in addition to material phase aberrations such as grain angle variations and defects. In this study, two-dimensional (2D) and three-dimensional (3D) void characteristics were investigated. An experimental program along with a statistical survey was conducted to quantify the following 2D and 3D void characteristics in two $133\times 133\times 610\mathrm{mm}$ PSL billets: volume fraction, volume, alignment, and moments of inertia of voids, as well as second moment properties, lineal path function, and chord length functions of the two phase mesostructure. As expected, most of the voids lie on the longitudinal direction of the specimen and have approximately an ellipsoidal shape. Based on this shape data, the characteristics of the ellipsoids that best fit the voids were calculated. Using the statistical data of the fitted ellipsoids, a random field of virtual ellipsoidal voids to simulate the mesostructure of PSL was generated.

To investigate the properties of antifreeze asphalt mixtures (AFAC), the dense-graded and gap-graded asphalt mixtures, AC-13 and SMA-13, containing 2, 4, 5, 6, and 4 % by weight and 5, 6, 7, and 8 % by weight antifreeze filler, respectively, were used in this paper. In the experiments, Marshall, rutting, bending beam, and immersion Marshall tests were used to study the engineering performances of AFAC. In addition, a conductivity test was carried out to evaluate the salt releasing law under static state condition. Results show that the properties of AFAC are affected by the gradation composition and content of antifreeze filler. It is suggested that the content of antifreeze filler is $3\sim 6\%$ by weight according to the Marshall test. The composition type of asphalt mixture is an important factor in AFAC because the durability of SMA-13 is worse than that of AC-13. Moreover, the salt releasing process is divided into three steps based on the conductivity test.

The dynamic modulus of asphalt concrete mixtures is a key property in assessing asphalt pavement performance based on its role in the mechanistic-empirical design method. The dynamic modulus is also considered to be used as one of the major characteristics in performance-related specifications for quality assurance. However, no feasible method to estimate the mean and variance of the in-place dynamic modulus for the as-built asphalt pavement has been suggested. This paper presents a methodology of stochastically evaluating the in-place dynamic modulus of the as-built asphalt pavement using a relationship of in-place air voids and a set of single dynamic modulus values measured in the laboratory. The methodology was validated with asphalt mix collected from a construction site. The comparison plot between the estimated in-place dynamic modulus and as-designed asphalt mix demonstrated a simple way to evaluate the as-built mix quality. This methodology provides several practical advantages to determine the quality of as-built mix compared with that of as-designed mix in terms of the dynamic modulus. In addition, the methodology envisions the possibility of incorporating the dynamic modulus into performance-related specifications.

In the last decades, a number of technical solutions for the improvement of structural connections using new materials between masonry wall panels have been the subject of several studies. In this context, the increasing interest in titanium could be attributed to its high specific resistances and chemical stability. The emphasis of this study is therefore the understanding of the bond behavior between lime-based mortars and titanium-based reinforcing rods. Experimental results showed that the titanium-lime bond is characterized by low bond strength. With the aim of increasing bond stresses, different surface treatments were investigated based on chemical and mechanical interlocking. The effect of these treatments and the general problems related to masonry reinforcing techniques have been discussed.

The lightweight deflectometer (LWD) is a portable device that measures surface deflections and applied force, from which dynamic stiffness and elastic modulus can be estimated. The inclusion of radial offset sensors with LWD testing, referred to here as multiple sensor LWD testing, stemmed from the well-established falling weight deflectometer (FWD) testing method. However, little research exists in the literature addressing LWD use on stabilized or lightly bound layers with multiple sensors, or exploring the applicability of backcalculating/isolating layer moduli from multiple sensor LWD tests. To this end, over 200 multiple sensor LWD tests on stabilized base materials were performed at five sites and rigorously analyzed to determine if the test could capture growth in stabilized base stiffness while the underlying subgrade layer remained unchanged. Deflection results demonstrate that the LWD test is capable of detecting changes in the stiffness of the stabilized base material during curing as illustrated by the decreasing magnitude in center deflections. Furthermore, radial offset deflections measuring 60 cm from the plate center remained constant during curing, providing valuable information about the subgrade support. The findings made directly from the deflections were confirmed via an analytical backcalculation using Boussinesq’s equations and Odemark’s method of equivalent thickness. The use of multiple sensor LWD testing allows for a richer interpretation of earthwork behavior than the traditional center deflection LWD results.

In this study, phenol was replaced by a powdery bisphenol A to produce aminosulfonate -phenol-formaldehyde (ASPF) superplasticizer (SP); ASPF SP and aminosulfonate-bisphenol A- formaldehyde (ASBF) SP were prepared. ASPF and ASBF SPs have $─{\mathrm{NH}}_2$, ─OH, $─{\mathrm{CH}}_2$, $─{\mathrm{C}}_6{\mathrm{H}}_5$, $─{\mathrm{SO}}_3$ functional groups, the weight-average molecular weight of 17.22 and 18.61 kDa, respectively, and the average polydispersity index of 1.08 and 1.53, respectively. The cement particle surface with ASPF SP has a higher initial zeta potential than that with ASBF SP. Along with time, the zeta potential of the cement particle surface with ASPF and ASBF SPs of $10\mathrm{g}/\mathrm{L}$ change from $-15.42$ and $-15.30\mathrm{mV}$, respectively, in initial time, to $-15.62$ and $-15.72\mathrm{mV}$, respectively, after 120 min. ASPF SP exhibits a higher water reduction percentage than ASBF SP. The concrete with ASPF SP has a higher slump loss rate and mechanical properties than that with ASBF SP. The air content, wet density, and setting times of cement pastes with ASPF and ASBF SPs have no differences. It is an effective method to produce ASPF SP in a cleaner process.

Warm mix asphalt (WMA) describes various technologies that allow asphalt mixtures to be produced at lower temperatures as compared to hot mix asphalt (HMA). WMA technologies also offer improvements in workability, cost, and environmental sustainability such as reduced fuel usage, greenhouse gas emissions, and wear and tear at plants, while enhancing worker health and safety conditions. These benefits, as well as the mechanical properties of WMA mixtures, need to be quantified and compared to that of HMA. The primary objective of this study was to evaluate the laboratory performance of plant-produced lab-compacted mixtures utilizing various WMA technologies. The secondary objective of this study was to compare WMA energy consumption cost and emission data to conventional HMA mixtures in terms of fuel/energy savings at the plant and in terms of CO and ${\mathrm{CO}}_2$ emissions. Three projects in Louisiana utilizing four different WMA technologies were considered in this study, yielding 11 mixtures total. Each project included a companion HMA mixture section to allow for direct comparison. Loose mixtures were obtained from trucks at the plant and compacted on-site in a mobile asphalt laboratory. Laboratory tests included dynamic modulus ($|E^{*}|$), flow number (FN), loaded wheel tracking (LWT) test, indirect tensile (IDT) test, semicircular bend (SCB) test, thermal stress restrained specimen test (TSRST), and the Lottman moisture susceptibility test. Results indicated that WMA mixtures exhibit similar high and intermediate temperature performances in the laboratory as compared to HMA. On average, $1.61 of energy savings per ton of produced asphalt mixture was observed, along with a considerable reduction in air pollutants at the plant. However, the cost of additives and royalty fees would reduce the total cost savings from using WMA. These benefits were observed without reduction in the mechanistic performance of the mix.

Construction and demolition (C&D) materials constitute a major proportion of waste materials present in landfills worldwide. With the scarcity of high-quality quarry aggregates, alternative materials, such as C&D materials, are increasingly being considered as a replacement for traditional road-construction materials, particularly as the sustainable usage of these C&D materials has significant environmental benefits. In this research, an extensive laboratory evaluation was carried out to determine the engineering properties of cement-treated C&D materials. The C&D materials investigated were reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The geotechnical properties of cement-treated C&D materials were evaluated to assess their performance in pavement base/subbase applications. The effect of curing duration on the strength of the C&D materials was analyzed by conducting unconfined compression strength and repeated load triaxial tests. The RAP required 2% cement (by weight) and either 7 or 28 days of curing to meet the local road-authority requirements, whereas RCA and CB required 4% cement and 28 days of curing. The RAP exhibited the highest strength in all cases, with the same cement content and for the same curing duration, followed by RCA and CB. The resilient moduli of C&D materials increased with an increase in cement content, curing duration, and confining pressure. Humidity curing was found to play an important role in the strength development of cement-treated C&D materials. This study indicates that cement-treated C&D materials are viable construction materials for pavement base/subbase applications.

This paper comprehensively studies the influence of hydrated lime usage on the repeatability and pervasiveness of the self-healing mechanism in engineered cementitious composites (ECC) incorporating high-volume fly ash (HVFA). Repeatability of self-healing was evaluated by repeatedly preloading the specimens up to 70% of their original deformation capacities at the end of each specified cyclic wet/dry exposure. Resonant frequency (RF) and rapid chloride permeability tests (RCPT) were used to assess the extent of deterioration. Crack characteristics were also presented to account for the changes observed in cracks throughout the RF tests. To monitor the pervasiveness of self-healing, RF measurements were recorded from both the top and middle portions of the specimens. Experimental results strongly suggest that the self-healing mechanism in cementitious composites can be made far more repeatable and pervasive with the addition of hydrated lime to the HVFA-ECC mixtures; this can have a significant impact on the development of smart sustainable infrastructures with highly robust self-healing capabilities.

This study aims at developing an accurate and efficient methodology to estimate the resilient modulus of unbound aggregates. First, a new resilient modulus model is proposed to incorporate the moisture dependence of the resilient modulus in addition to the stress dependence in existing models. Second, prediction models are developed to conveniently and accurately determine the coefficients in the proposed model. In order to characterize the moisture dependence of unbound aggregates, the degree of saturation and the matric suction parameter are added into the proposed model. The soil-water characteristic curve (SWCC) is used to determine the matric suction value at any given moisture content. The moisture dependence of the model is validated for selected materials with different moisture contents. In order to develop prediction models for the coefficients in the proposed model, laboratory experiments and multiple regression analysis are conducted on 20 different base course materials. The laboratory experiments include the improved repeated load triaxial test and tests to measure performance-related base course properties. A new test protocol is developed for the improved repeated load triaxial test, which is better adapted to the stress state of the base course under the actual traffic load than the current test protocols. A series of repeatable and performance-related base course properties are measured and used to develop the prediction models based on multiple regression analysis. These newly proposed properties include methylene blue value (MBV), percent fines content (pfc), gradation of particle sizes, and shape, angularity, and texture of aggregates. The developed prediction models have higher $R$-squared values than those using other base course properties.

Cross laminated timber (CLT) is an engineered wood plate product suitable for the construction of shear walls in low-rise and medium-rise residential and commercial buildings. CLT shear walls are attached to foundations by using metal connectors arranged to prevent the horizontal sliding and uplift of entire superstructures. It is critical that individual CLT panels remain properly anchored, even during events such as design level wind storms and earthquakes, and that overloaded connectors attaching walls to foundations are capable of deforming plastically. This paper presents an experimental investigation of the mechanical behaviors of a range of commercially manufactured and specially designed steel angle bracket connectors intended to resist horizontal shear force flow at CLT wall and foundation interfaces. Both monotonic loading and fully reversed displacement controlled loading protocols were employed so that results apply to wind and seismic design scenarios. The broad conclusion is that the behavior of CLT panel-to-foundation angle bracket connections is too complex to be predicted by using simplified analytical methods. Therefore, test based studies are the only reliable means of determining design capacities for particular types of angle bracket connections.

Finely ground glass has the potential for pozzolanic reactivity and can serve as a supplementary cementitious material (SCM). Uniform composition, amorphous nature, and high silica content make ground glass ideal for studying the effects of glass type and particle size on glassy material reactivity at different temperatures. This study focuses on how the combination of glass types and particle sizes affects the microstructure and performance properties of cementitious systems containing glass cullet as a SCM. In this study, the reaction rate, pozzolanicity, and hydration degree quantification of four sets of combined glass types and sizes were investigated using isothermal calorimetry, chemical shrinkage, thermogravimetric analysis (TGA), and analysis of scanning electron microscope (SEM) images. Moreover, compressive strength and water sorptivity were performed on mortar samples to correlate reactivity of cementitious materials containing glass to the performance of cementitious mixtures. Results showed that combined glass can increase reaction rate and exhibit pozzolanic properties, especially when particles of clear and green glass below 25 μm were used at a curing teperature of 50°C. The simultaneous effect of sizes and types of glass cullet (surface area) on reaction rate of glass powder also can be accounted for through a linear addition, reflecting that the surface area would significantly affect glass cullet reactivity. However, performance properties of cementitious systems containing combined glass types and sizes behaved differently, as they followed the weaker portion of the two particles.

During the past decade, attention has been drawn to a relatively new composite material, polymer concrete (PC). The idea started as a possible replacement of portland cement in concrete by a polymerized monomer, which resulted in polymer modified concrete (PMC). PC is considered to be a relatively new high-performance material. It is essentially a cementless concrete in which ordinary portland cement has been entirely replaced by polymer resins that bind together the aggregates, forming a rocklike solid material. This paper aims at identifying the suitability of using volcanic tuff as filler in polymer concrete. Based on the experimental results, it can be said that the volcanic tuff influences the microstructure of polymer concrete, leading to a more homogeneous and compact structure. This results in improved mechanical and elastic properties, provided a threshold value is not exceeded.

Cold in-place recycling is considered as a pavement rehabilitation technique that is more environmentally friendly than the common practice of simply constructing a new hot-mix asphalt (HMA) overlay on the existing wearing surface. This paper describes a laboratory experimental study for the formulation and mechanical characterization of cement-treated reclaimed asphalt pavement (RAP) material to be used as a base layer during the rehabilitation of pavements. RAP content was varied between 0 and 100% in order to study the effects of this parameter on the mechanical properties. Portland cement content was kept constant at 6% by weight of dry constituents. Results have shown that an increase in RAP content results in a decrease in compressive strength, flexural strength, indirect tensile strength, and elastic modulus. However, for any RAP content of 60% or less, acceptable mechanical properties for a pavement base layer were achieved. Unrestrained shrinkage testing showed statistically insignificant change in shrinkage strain with RAP content.

This paper studies alkali activation of copper mine tailings (MT) and low-calcium flash-furnace copper smelter slag (SG), two major types of wastes from the mining industry. The effect of SG content, curing temperature, and curing time on the unconfined compressive strength (UCS) of the MT/SG-based geopolymer is investigated systematically. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy are also used to investigate the microstructure and elemental and phase composition of the MT/SG-based geopolymer. The results show that the addition of SG significantly improves the UCS and microstructure of the geopolymer. The improvement is mainly attributed to the high solubility of silica in the SG and the fine particle size of the SG. The inclusion of SG also leads to decrease of the optimum curing temperature (i.e., the temperature at the highest UCS) because of its higher reactivity than MT. In addition, the MT/SG-based geopolymer sets fast and gains a major portion of its ultimate strength within only 7 days. Based on the results, it can be concluded that the MT/SG-based geopolymer is a promising sustainable construction material for civil engineering applications.

The strategy of blending a low-utility waste stream (glass) into a well-recyclable stream [recycled concrete aggregate (RCA)] was applied that entailed evaluating porous asphalt mixture (PAM) made of RCA and glass. Two hybrid PAM designs containing 78% RCA, together with 16% glass particles as smallest-sized or as medium-sized aggregate component, were evaluated against two control groups comprising full-granite and full-RCA aggregates, respectively. An experiment designed to assess the bonding effect between asphalt and aggregates showed that glass particles possessed the weakest bonding effect with asphalt as compared with granite and RCA. Optimal asphalt content (OAC) was determined based on Cantabro test, draindown test, and Marshall test. For the two hybrid PAMs, mixture containing fine glass was more resistant against abrasion but weaker in dynamic creep test than the mixture containing medium-sized glass. On the whole, PAM material made with waste materials can meet the relevant requirements in performance tests and are considered suitable for direct applications in low-strength pavements such as pedestrian and cyclist pathways.

Coir waste, as, its name indicates, is a waste by product of the coir manufacturing industry. Past records show that for every ton of fiber extracted, about two tons of coir waste is produced. Thus handling of coir waste has become an immediate concern due to its massive accumulation and lack of dumping yards. The present work aims to study the use of coir waste to control the volume change behavior of marine clay keeping sustainable development in focus. Consolidation tests, swelling pressure tests, and three-dimensional (3D) shrinkage strain tests were conducted to analyze the effect of addition of coir waste on volume change behavior. Coir waste consists of pith along with some short fibers which were separated to study their independent effects on volume change behavior. Volumetric swelling of optimum soil-pith-fiber mix was also studied by conducting three-dimensional free swell tests. Mixing of coir waste with expansive soil helps to mitigate the volume change behavior of expansive soil. Thus the material which was considered as a curse to the environment and the society has turned out to be a boon to the civil engineering community.

In this paper, the authors report a case study of synthesis, fabrication, programming, installation, and performance monitoring of a shape memory polymer (SMP) based smart sealant for compression sealed joint in a concrete pavement. Two types of SMPs were synthesized and SMP panels were fabricated. Panels made of one type of SMP were programmed by one-dimensional (1D) stress condition, and panels from the other type of SMP were programmed either by two-dimensional (2D) stress condition or by 1D stress condition, leading to a total of three types of programmed SMP panels. The programmed panels were then installed in two compression sealed joints on a service concrete pavement. The two joints have been monitored for over two years. No evidence of failure has been found.

This study investigates the effect of the strand-to-duct area ratio on the shrinkage cracking behavior of posttensioning grout. The free shrinkage behavior of grout was evaluated using various duct diameters. Test results indicated that the expansion and shrinkage strains of grout increased with the duct diameter. The strain of a restrained strand was barely affected by the number of strands but was significantly affected by the strand-to-duct area ratio. The specimen with a strand-to-duct area ratio greater than 0.3 showed shrinkage cracks in fewer than 30 days. Increasing the strand-to-duct area ratio shortened the cracking time. All the test specimens showed bleeding immediately after pumping, along with air void pockets in the grout.