Journal of Materials in Civil Engineering

Reactive MgO has recently emerged as a potential activator for ground-granulated blast-furnace slag (GGBS), which is one of the most widely used by-products in the cement industry. However, it is known that the characteristics of reactive MgO vary significantly, which may affect the activation process and hence the performance of MgO-GGBS blends. In this study, seven commercially available reactive MgOs, whose characteristics vary widely, were chosen to activate GGBS. The unconfined compressive strength (UCS) of MgO-GGBS pastes up to 90 days was measured, and the hydration products were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The primary hydration products were identified as calcium silicate hydrate (C-S-H) and hydrotalcitelike phases (Ht). Minor hydration products included magnesium silicate hydrate (M-S-H) and ettringite. The reactivity and calcium oxide content of the MgO samples were found to be the two major factors affecting the hydration process of the MgO-GGBS blend. Higher reactivity did not change the hydration products, but resulted in more hydration products in the same time. Sufficient CaO content increased the pH of the system, which enhanced the slag dissolution degree and was beneficial to the strength development.

This research concerns the uniaxial compressive basic creep of high-performance concretes (HPC) in the temperature interval 20–80°C. A basic creep experimental program was performed on HPC envisioned for future storage structures of intermediate-level long-life nuclear wastes. The study determines the long-term evolution of delayed strains and estimates the long-term behavior of HPC under conditions characterized by temperature increases that could reach 70°C attributable to heating by these exothermic wastes. The analysis of strains contributes to the understanding of basic creep at moderate temperatures and clarifies the effect of temperature. A campaign of uniaxial compressive basic creep tests was carried out on four formulations of HPC, two of which incorporated silica fume and stainless steel fibers, subjected to three different temperatures: 20, 50, and 80°C. The comparative analysis of delayed strains assessed the effect of temperature on basic creep kinetics and magnitudes and on Young’s modulus of HPC. Damage was observed at 80°C, revealed by a decrease in the modulus of elasticity and a strong increase in creep capacity. From these results, the fitting of a nonlinear viscoelastic model, considering the effect of temperature using an Arrhenius law affecting the viscosities from 20°C, a parameter linked to the intrinsic creep potential at temperatures between 50–80°C, and a thermal damage, is proposed. The improved knowledge of the temperature effect on delayed behavior and its better integration in mechanical models are useful for the design of special structures (e.g., massive structures and specific serviceability conditions in nuclear or hydroelectric power plants) sensitive to delayed strains and subjected to moderate temperatures.

The two-part research study presented herein evaluates fresh and hardened properties of vibratory-placed noncement/partial-cement concretes, as well as impact-compacted noncement concretes, containing various dosages of pulverized coal combustion fly ash and fluidized bed combustion spent bed. The results of Part I of this study on vibratory-placed noncement/partial-cement concretes revealed lower early strengths than those of reference concrete, whereas their late strengths (90 and 180 days) were similar to or higher than those of reference concrete. The selected noncement/partial-cement concretes produced higher expansion and lower drying shrinkage than those of the reference concrete. Abrasion resistance of noncement and partial-cement mixtures under dry conditions were better than that of the reference concrete, whereas opposite results were obtained under wet conditions. Laboratory results of Part II on impact-compacted noncement concretes revealed higher compressive strength and resistance to internal sulfate attack with increasing coarse aggregate content. The strength, stiffness, and resistance to abrasion and freezing/thawing of impact-compacted concretes improved with decreases in fluidized bed combustion (FBC) spent bed to pulverized coal combustion (PCC) fly ash ratios, whereas opposite results were obtained for sulfate-induced expansions.

According to the report of the World Meteorological Organization (WMO), more than half of the world’s population will not have enough drinking water by 2025. To save drinking water, use of seawater in the concrete industry seems imperative. In the present study, the possibilities of seawater as a material of concrete are discussed as a result of the literature-based and experimental investigations. From the results of the literature-based study, more than half of the papers collected in this study had positive opinions about concrete mixed with seawater by adding the mineral admixture such as blast furnace slag (BFS). In addition, some results of long-term exposure tests indicated the high possibility of using seawater as a material of concrete. The experimental data obtained in this study indicated that the addition of BFS might contribute significantly to the corrosion resistance of steel bar, because of the low oxygen environment around steel bar and chloride immobilization.

An extensive investigation was carried out for recycling of demolished brick aggregate concrete as coarse aggregate. For this, demolished concrete blocks were collected from 33 different building sites of different ages and broken into pieces as coarse aggregate. Owing to the lack of availability of stone aggregate in Bangladesh, most of the old structures are constructed with brick chips as coarse aggregate, therefore the recycled aggregate investigated in this study is different from the recycled aggregate investigated in other countries which are mostly made of stone chips. The properties of recycled aggregate, such as specific gravity, absorption capacity, and abrasion were tested. More than 700 cylinder concrete specimens of diameter 150 mm and height 300 mm were made with water-to-cement ratios of 0.45 and 0.55. Concrete specimens were tested at 7, 14, and 28 days for compressive strength, tensile strength, and Young’s modulus. The results are compared with virgin brick aggregate. Extended study was also conducted on partial replacement (10–50%) of virgin brick aggregate with recycled brick aggregate. Also, in-situ strength of an old structure has been compared with the compressive strength of recycled aggregate concrete made with the recycled aggregate collected from the same structure. Based on this investigation, it is revealed that recycled brick aggregate can be used as coarse aggregate for making concrete of strength 20.7 to 31.0 MPa. For the same mix design, the recycled aggregate concrete produces almost similar strength compared with the virgin first class brick aggregate concrete commonly used in Bangladesh. However, relatively better performance of recycled aggregate concrete is found for W/C = 0.45. No significant change in compressive strength of concrete is found for up to 50% replacement of virgin aggregate by recycled aggregate. By recycling, it is possible to make concrete with more strength compared with the in-situ strength of concrete of old structures.

As part of a study into the controls on the deterioration of concrete due to sulfate attack, mortars (50-mm cubes and $40\times 40\times 160\mathrm{mm}$ prisms) made with portland cement CEMI, and 90% CEMI + 10% limestone blend were exposed to BRE DS4 sulfate solution based on magnesium sulfate (${\mathrm{MgSO}}_4•7{\mathrm{H}}_2\mathrm{O}$) under wetting and drying cycles for 18 months at 5°C. The effect of these cycles on thaumasite formation was studied and compared with samples immersed continuously in the same solutions. Visual observations and mass and length changes were used to assess the mortar deterioration, along with X-ray diffraction and infrared spectroscopy, which were used to determine the mineralogy of deterioration products. It was found that at 5°C, wetting and drying cycles significantly delayed thaumasite formation compared with control specimens.

Recent interest in creating green construction materials has sparked the development of portland cement–free binders. Alkali-activated slag (AAS) concrete has a low embodied energy and comparable or superior strengths to ordinary portland cement (OPC) concrete. However, one factor limiting AAS usage is its durability performance, specifically its susceptibility to shrinkage. Before declaring AAS a marketable product, the mechanisms behind its volumetric instability need to be understood. This paper presents a preliminary study of the shrinkage deformations of various AAS mixtures, wherein four unique AAS mortars were designed and tested for autogenous, chemical, and drying shrinkage; time of setting; and compressive strength. All results were compared to those obtained for a control OPC mortar. Alkali-activated slag mixtures with comparable strength to OPC show a higher autogenous and drying shrinkage. A lower elastic stiffness, higher degree of saturation, and potentially higher chemical shrinkage contribute to the high autogenous shrinkage of AAS. A lower elastic stiffness also leads to a large drying shrinkage, although other mechanisms, such as reduced pore size and carbonation shrinkage, are likely to also contribute to the high drying shrinkage measured for AAS.

Continuous fiber rope (CF rope) made of aramid fiber or vinylon fiber has been developed to apply for the reinforcement of concrete members and structures. It is characterized by a light weight, high tensile strength, and excellent durability compared with reinforcing steel bar. It has also good transportability, and it is flexible to be easily arranged at the construction site. The purpose of this study is to investigate the shear-reinforcing effect of CF rope. First, the reinforced concrete (RC) beams without shear reinforcement were tested. Then, the RC beams wound with CF rope at shear span were tested. Moreover, the shear-reinforcing effect of CF rope on the RC beams that were predamaged in shear assuming seismic retrofitting was also investigated. Through the test results, we confirmed that CF rope was effective for the RC beams without shear reinforcement and the predamaged RC beams in shear.

While there have been various research activities to develop the green vehicles which reduce the energy consumption such as high-speed train, tilting train, light rail transit, wireless tram, and so on, researches on the eco-friendly railway infrastructure have been very limited to deal with the important social issue of reducing ${\mathrm{CO}}_2$ emissions. In this background, eco-friendly prestressed concrete (PSC) sleeper, using ground granulated blast furnace slag and rapid-cooling electric arc furnace oxidizing slag, has been recently developed to reduce the usage of cement and natural fine aggregate as main ingredients of the concrete. It was already found that eco-friendly PSC sleeper satisfied its static and dynamic performances required by international standards. In this paper, the field performance of eco-friendly PSC sleeper was evaluated in the operating line of conventional railway and its durability against extreme environmental conditions was performed in the laboratory as well. Steel slags (ground granulated blast furnace and rapid-cooling electric arc furnace oxidizing slag) are suitable alternative concrete ingredients to cement and natural fine aggregate for railway infrastructure applications, and the eco-friendly PSC sleeper can be an environmental as well as mechanical alternative to conventional PSC sleeper in railway.

In this paper, setting time, strength and bond of high-calcium fly ash geopolymer concrete were investigated. The high-calcium fly ash was from Mae Moh power plant in northern Thailand. Both sodium silicate solution and sodium hydroxide solution were used as alkali activators in every mix. Sodium hydroxide solution with 10 M, 15 M, and 20 M concentrations, sodium silicate to sodium hydroxide ratios of 1.0 and 2.0, alkaline liquid to fly ash ratio of 0.5 and two curing regimes viz., heat curing at $60\pm 2°\mathrm{C}$ for 24 h and room temperature curing at $23\pm 2°\mathrm{C}$ were used. The results indicated that fresh geopolymer concrete had short setting time of 28–58 min due to the presence of high calcium content of fly ash. In general, strengths and modulus of elasticity increased with the increase in NaOH concentration. For compressive strength, the optimum ${\mathrm{Na}}_2\mathrm{O}$ content was around 12% of fly ash. The high-strength geopolymer concrete with 28-day compressive strength of 54.4 MPa was obtained for mix with 15M NaOH. The modulii of elasticity of geopolymer concrete were related to the compressive strengths and comparable to those of portland cement concrete. The tensile splitting strength and bond strength were also related to the compressive strength and the values were higher than those of portland cement concrete. In particular, the bond strengths were significantly higher than those given by the current design code.

Soft clays are widely distributed in Missouri, United States. Due to their relatively low strength and high compressibility, subgrade construction in soft clays has encountered many difficulties. In recent practice, the use of fly ash (FA) along with lime to tackle soft subgrade problems has shown promising results. The effectiveness of Class C FA and lime kiln dust (LKD) in clay subgrade stabilization is examined in this research. Scanning electron microscopic (SEM) analysis, proctor compaction tests, unconfined compression tests, and resilient modulus tests were carried out on the FA and LKD modified soil mixtures. Test specimens were prepared at optimum water content and tested at various curing periods. The test specimens were reconstituted by static compression. Test results revealed that the addition of Class C FA could increase the dry unit weight of the FA treated soil, enhance the unconfined compressive strength, and improve the resilient modulus. Regression equations were developed to correlate the resilient modulus with curing time. The mechanism of FA stabilization was discussed based on the SEM results and the measurement of the electrical conductivity of the FA-soil-water system. Correlations between the unconfined compressive strength and resilient modulus were developed. It is concluded that subgrade stabilization with Class C FA and LKD are cost-effective for road-base construction.

Very high moisture content fine grained soils (abbreviated as VHMS for very high moisture soils) have been studied from many perspectives, yet their role in disaster recovery has not been heavily investigated. This paper’s primary objective is to present material properties of portland cement stabilized VHMS and discuss its immediate reuse for disaster recovery. The paper focuses on laboratory properties that can be achieved by combinations of three soils with differing plasticity, seven portland cements at varying dosages, and two very high moisture levels. Approximately 1,200 unconfined compression tests were performed. Laboratory test results indicated shear strengths of ${0.1–3.8\mathrm{kg}/\mathrm{cm}}^2$ could be achieved after 1–7 days of room temperature curing. Literature and practice review indicated chemically stabilized VHMS (i.e., emergency construction material) could be mixed with pugmills or concrete ready-mix trucks, pumped 1–3.2 km, and placed without mechanical compaction. Beneficial reuse after disaster recovery ceases is also likely in many applications. The overall assessment of the paper is that portland cement stabilized VHMS can be a viable solution for disaster recovery.

The main objective of this study was to develop comprehensive criteria to evaluate the remaining service life of existing roads as regards their field fatigue cracking characteristics using fracture mechanics principles and associated laboratory performance tests. Two base course layers were investigated for their residual fatigue lives: reference and modified stone mastic asphalt mixes. The two pavement systems’ material characteristics using the actual field cores were estimated in the laboratory, including moduli, fatigue relationships, and crack propagation parameters. Additionally, field measurements encompassed collection of falling weight deflectometer deflections, temperature variations, and traffic counts. Fatigue lives of the two base course layers were predicted using the developed laboratory-based fatigue and crack propagation parametric relationships during one climatic period. The modified structure presented significantly longer fatigue life than the reference mix. This was indicative of the findings that the laboratory procedure(s) based on asphalt mixture properties’ fracture and fatigue mechanics such as crack initiation, and propagation modeling and relationships are useful for evaluating the pavement mix’s performance in the field as well. Overall, laboratory tests provided reliable information regarding residual life predictions in case it is difficult to actually perform field measurements and estimate the residual life of a pavement system. The criteria developed in this study should serve as guidelines for agencies to comprehend and understand a substantial amount of information regarding asphalt materials’ fatigue characterization so that it can be implemented as one of the quality control tests to assess the pavement design life.

The use of self-consolidating concrete (SCC) has become more prevalent due to its economic and technological advantages over other types of concrete. Nevertheless, issues relating to casting and placement hinder its widespread use. One of the primary concerns of using SCC is related to its high formwork pressure, which affects any type of structural element, whether it is precast or cast on site. This study aimed to make correlations between different parameters obtained through slump flow and shear rheological tests in order to determine what the implication would be on the evolution of formwork pressure for five typical precast SCC mixes. The parameters were slump flow diameter, spreading rate, yield stress, plastic viscosity, and rate of structural rebuilding (stress relaxation). In addition, the advantages, from the point of view of cost and safety, of incorporating nanoclays and viscosity-modifying admixtures in SCC to reduce initial pressure and increase rate of pressure drop to optimize the formwork design were demonstrated.

This paper highlights the results of an experimental investigation on the tensile strength behavior of plastic-fiber-reinforced soil performed to study the possibility of utilization of waste plastics in soil masonry blocks. Cylindrical specimens of raw soil and modified soil compacted at different pressure by varying the molding pressure from 1.25 to 7.5 MPa corresponding to a molding load from 10 to 60 kN are tested for split tensile strength and compressive strength. Raw soil is modified by adding a varying the amount of stabilizer (cement: 7.5, 10, and 15%), fiber types (made out of mineral water bottles and carry bags), fiber length (1 and 2 cm), and fiber percentage (0.1 and 0.2%). The results show that compared with raw specimens, a compacted reinforced cement stabilized specimen shows an increase of 4.5 times in its tensile strength. This is one of the major advantages of adding fibers to the compressed stabilized specimens. From the observations of failure pattern it can be concluded that the benefit of fiber reinforcement is the improved ductility.

In the current trend of sustainability, the concrete community has been aggressively looking into adopting green construction material practices and at the same time improving concrete quality and performance for extensive service life and adaptive reuse. Concrete is the construction material most used in the world, with an estimated yearly production of 2.35 billion tons worldwide. In the United States, it is estimated that on average approximately 5% of the ready-mix concrete produced is unused and returned to the plant with only a small portion reused. Such a material when further processed, identified as crushed returned concrete aggregate (CCA), has a significant residual value because among other things it is free of contaminants and has better quality than recycled concrete aggregate (RCA). The objective of this study was to assess the shrinkage behavior of CCA concrete mixtures produced with aggregate from returned concrete. The aggregate was prepared from concrete of different strength. The virgin aggregate (stone) was replaced either partially or at 100% level in the concrete mixtures. The response of the hyperbolic shrinkage prediction model was examined, and based on the experimental results an alternative model is proposed. The proposed model and methodology can be used to estimate the drying shrinkage of CCA mixtures, and eventually can be adopted for assessing the shrinkage behavior of these concrete mixtures in other regions.

Results are presented for a series of laboratory tests that were undertaken to characterize the tensile properties of an engineered cementitious composite (ECC) mix, which is a mortar-based composite reinforced with synthetic fibers to provide tensile strain–hardening characteristics. Dogbone-, rectangular-, and circular-bar-shaped specimens were developed to determine the most suitable specimen geometry for uniaxial tensile testing (UTT), with the circular-bar specimens that were constructed by coring through sprayed ECC panels showing the best geometrical consistency, both within each specimen and between individual specimens. Fifty circular-bar specimens with a diameter of 16 mm and a length of 200 mm were tested under uniaxial tension to determine the characteristic tensile properties. Statistical distributions were used to define a 5% characteristic tensile yield strength of 1.82 MPa and a 10% tensile total strain of 0.08%. A material ductility factor of 4.0 was determined, and $k$ factors are proposed to convert quality assurance test mean values to characteristic values.

This paper presents the results of an experimental program undertaken for evaluating the effectiveness of ultrahigh performance fiber-reinforced concrete (UHPFRC) for strengthening deficient tension lap splices. A total of 18 full-scale beam specimens were tested. Tension reinforcement consisted of two deformed bars spliced at midspan. The strengthening technique consists of replacing normal concrete in the splice region with UHPFRC. One type of fiber concrete was used in this experimental program. It is characterized by a compressive strength of 130 MPa, a high tensile strength of 10 MPa, and ductile strain hardening characteristics in direct tension. The parameters considered were: splice length, bar diameter, repair depth, and bar relative position. To isolate the contribution of UHPFRC, no stirrups were used. The results clearly show the effectiveness of UHPFRC for strengthening deficient lap splices. Failure by splitting in the lap splice region was completely eliminated due to the high tensile strength and energy absorption capabilities of the UHPFRC used. Bond stresses that were more than twice those of normal concrete were observed. The UHPFRC ductility allows for the development of quasi-plastic tensile stresses around the reinforcing bars to resist the splitting forces. For the selected UHPFRC, this stress was evaluated at approximately 7.3 MPa, which is applicable to tensile strains of up to 0.2% before the formation of discrete cracks. Although the paper focuses on rehabilitation, the results are also applicable to new constructions. Suggestions for further research and better classification of UHPFRC for structural applications are identified.

The building construction industry is in need of sustainable materials and solutions. A novel building material, such as textile-reinforced concrete (TRC), could be used to meet this demand. Textile-reinforced concrete is a combination of fine-grained concrete and multiaxial textile fabrics that has been fundamentally researched over the past decade. TRC-based research has explored various facets of this composite material, such as its structural functionality, production, applicability, and design. One key aspect that is still missing, however, is a comprehensive review of the sustainable potential of this material in terms of its input–output and durability that suitably answers to requirement No. 7 of EU’s Construction Products Regulation. This article provides qualitative and quantitative evaluation of the sustainable potential and prospective development of TRC particularly reinforced by alkali-resistant (AR) glass, carbon, or basalt fibers. Based on the outcome of this evaluation, carbon textile fibers were observed to hold the optimal potential mechanical behavior; additionally, it was revealed through the conducted life-cycle assessment (LCA) that basalt had the least cumulative energy demand, whereas carbon had the least environmental impact.

The low degree of hydration of fly ash (FA) and slag (BFS) particles in high-volume FA and BFS concrete offers the possibility to activate the unreacted particles upon crack formation to close the crack. In this paper, a preliminary study is performed to evaluate the use of alkaline activators to stimulate the formation of reaction products in the crack. First, the reaction rates of crushed pastes mixed with alkaline solutions or water were monitored by calorimetry. These tests showed that alkaline activators stimulate the reactions more than water. Secondly, cracked mortar beams were stored in different alkaline solutions or water and the crack self-closing ratio was calculated after microscopic investigation at different time intervals. The results indicated that reference mixes, containing only ordinary portland cement as binder, heal very well autogenously, while a solution of ${\mathrm{Ca}(\mathrm{OH})}_2{+\mathrm{Na}}_2{\mathrm{CO}}_3$ seems to be the most suitable activator to stimulate crack closing of BFS concrete. Thirdly, the regain in strength due to healing of the cracks was determined. Compared to other self-healing techniques, strength regain is limited (about 10–40%).

In this paper, the hydromechanical behavior of unsaturated soils is explored. A constitutive model is proposed to describe the coupled hydraulic and mechanical behavior of unsaturated soils. The compression stiffness parameters, such as $\lambda (s)$, $\kappa (s)$, ${\lambda }_s$, and ${\kappa }_s$, are analyzed, taking into account the influences of suction, degree of saturation, and net mean stress. Based on the volume change behavior under constant suction and the water retention properties, the relationship between the degree of saturation and volume change has been investigated under both net mean stress and suction. The proposed model is capable of describing the mechanical behavior of unsaturated soils for either isotropic compression or triaxial compression. Indeed, the simulation results of three cases of suction-controlled laboratory tests show good agreement with experimental data.

Perlite is a volcanic aluminosilicate abundant in several countries that are major producers of portland cement. The amorphous nature and silica-to-alumina ratio of ground perlite indicate that it can be activated with alkaline solutions. This study presents the strength development of mixtures containing only ground perlite as their powder binder, activated with sodium hydroxide and/or sodium silicate solutions, at room temperature or using oven curing. The structure of the formed geopolymers is investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The thermal stability and acid resistance of the mixtures are evaluated. Sodium silicate-activated mixtures slowly reach moderate strengths at room temperature but sodium hydroxide-activated ones do not develop strength regardless of activator concentration. Both activators produce geopolymers with high strengths with 100°C dry oven curing. Sodium silicate-activated specimens are more resistant to high temperatures but less resistant to a sulfuric acid solution than are sodium hydroxide solution-activated specimens. Being natural and having a more consistent chemical composition compared with most artificial pozzolans make perlite an attractive geopolymer raw material.

Maintenance and reconstruction of road pavements involve the production of huge amount of discarded material, such as reclaimed asphalt (RA), every year. As a consequence, issues related to RA stockpiles and disposals are dramatically increasing. At the same time, the growing importance of environmental and economic matters has led researchers and engineers to promote reusing milled materials rather than using valuable and nonrenewable natural resources (bitumen and aggregates). Road pavement maintenance and construction usually involve the use of porous asphalt (PA) mixtures, in particular in the case of motorways and highways. In fact, PA mixtures are widely employed as pavement surface layer thanks to their ability in reducing traffic noise and enhancing safety in wet conditions. In this sense, the reuse of RA into PA should be strongly encouraged. Unfortunately, technical specifications adopted in many countries do not allow any recycled materials in porous asphalt surface layers yet. Thus, reliable techniques allowing the use of RA in new PA mixtures are needed. In this research study, the use of coarse RA from old PA as aggregate in new PA mixtures was evaluated. Because a previous laboratory study demonstrated that the use of 15% of RA aggregates in PA mixtures seems possible (or even recommendable) as long as an accurate mix design with adequate binder contents is performed, new laboratory and field evaluations on recycled PA mixtures with15% of RA aggregates were carried out. On one hand, cyclic coaxial shear tests (CASTs) were performed under both dry and water-submerged conditions in order to evaluate the simultaneous effect of traffic and water exposure. On the other hand, a comprehensive laboratory experimental program for assessing acceptability, durability, fracture resistance, and water sensitivity was carried out on materials taken from the field during the construction of a full-scale trial section. Moreover, drainage properties of surface layers were measured along such a trial section. Overall test results demonstrated that including 15% of selected coarse recycled aggregates into porous asphalt mixtures does not compromise performances and durability of both asphalt-plant and laboratory produced mixtures. It was demonstrated that recycled mixture with 5.25% of total binder content and prepared by accurate mix design can perform as well as (or even better than) standard PA mixture in terms of workability, acceptability, abrasion resistance, repeated loading resistance, fracture propagation resistance, moisture sensitivity, and water drainability.

Aggregate shape properties, such as form, angularity, and surface texture, highly influence the performance of hot-mix asphalt (HMA). Rutting is related to aggregate angularity and form, which affects the interlock among particles. Fatigue cracking can be decreased by an aggregate rough surface texture, which improves the aggregate-binder interaction. Several researchers have been studying new automated and more precise techniques, such as the aggregate image measurement system (AIMS), to improve the determination of aggregate shape parameters. This paper presents an analysis of aggregates from three different mineralogical sources, investigating the influence of shape properties on HMA design and mechanical properties. The results indicated that the aggregates had similar shape properties, despite differences in the mineralogical composition. This might be a direct effect of similar quarrying procedures. Surface texture resulted in different values, which can be explained by results from the petrographic analyses. In general, the aggregates’ shape properties resulted in HMA samples with similar mechanical behavior. The HMA specimens were also analyzed in terms of their internal structure, which included the investigation of a number of contact points, and aggregate particles’ segregation and orientation characteristics.

This study mixed ground granulated blast-furnace slag (S) and circulating fluidized bed combustion (CFBC) fly ash (CA) without any portland cement or alkaline activator to produce an eco-binder, abbreviated as SCA binder. The hydration process, microstructure, and compressive strength of hydrated SCA materials were investigated. Although both the slag and CA had poor hydration with water, the SCA binder produced satisfactory hydration products with sufficient cementitious properties. These hydration products detected by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were ettringite (AFt), calcium silicate hydrate (C-S-H), and calcium aluminosilicate hydrate (C-A-S-H). The scanning electron microscope (SEM) micrograph showed these hydration products formed dense microstructure for SCA pastes. As a result, the SCA materials had sufficient compressive strength for practical applications in building materials and civil engineering structures. The compressive strengths of the SCA paste and mortar reached 75 MPa at 28 days. Moreover, the SCA concretes met the requirements for structural concrete. An equation to predict the compressive strengths of the SCA concrete was proposed and agreed well with the experimental results.

The paper presents an effort to study the properties of locally available soil and its suitability as a construction material. The properties of cement-stabilized and unstabilized rammed earth blocks were studied in terms of density, strength, compaction energy, and durability in both cured and uncured condition. All the test samples were produced using steel rammer and wooden mold, with an attempt to select and validate the block-making equipment and technique that can be used for construction of rammed earth structures. The detailed test results and analysis show that the cement-stabilized rammed earth (CSRE) blocks are consistent in terms of density with respect to standard Proctor value under the accurate control of parameters such as cement content, optimum moisture content (OMC), and compaction energy. The CSRE blocks meet the design criteria outlined in various standards.

Existing test methods to assess alkali-silica reactivity of aggregates such as the accelerated mortar bar test (AMBT) has been shown to be less than satisfactory due to excessive false-positive and false-negative test results. While the concrete prism test (CPT) test is considered to be a more reliable alternative, the unusually long test duration (1 or 2 years, depending on the purpose) renders it unsuitable for routine evaluation of materials. This paper presents a new test method—the miniature concrete prism test (MCPT) that addresses the shortcomings of both the AMBT and the CPT test methods. The aggregates studied in this project were selected based on their established field performance. Results from this investigation indicate that the MCPT test method can reliably identify aggregate reactivity within a short duration of 56 days for the majority of aggregates, whereas it may take up to 84 days for some slowly reactive aggregates.

Based on Johansen yield theory (European yield model) and experimental observations, mechanical models and capacity equations for nail connectors used in wood-frame shear walls with cross-prefabricated ply-bamboo sheathing panels were studied. Embedment strength of ply-bamboo panel was obtained in accordance with a British Standards Institution (BSI) standard. Monotonic and cyclic tests of nails applied in timber-bamboo shear walls were performed to validate the capacity equations. The adopted capacity equation based on European yield model meets the test results well, in the average and with a reduced scatter. The theoretical and experimental results obtained from the research suggested a capacity model and equations to predict the bearing capacity of timber-bamboo nail connections, indicating that ply-bamboo panels can be used as sheathings for light-weight timber structures, as well as included in existing timber design code.

The objective of this research study was to conduct a laboratory investigation of reclaimed asphalt pavement (RAP), containing a high percentage of natural sand mixtures, in terms of moisture susceptibility, permanent deformation, and fracture energy with respect to the use of both hydrated lime and liquid antistripping additives (ASAs). The experimental design included one base binder, one natural sand, three ASAs, two aggregate sources, two RAP contents, and two surface mix types (Types B and C). A total of 12 mixtures were investigated and a total of 160 specimens were made and tested in this study. The test results indicated that the indirect tensile strength (ITS) and tensile strength ratio values of RAP with 20% natural sand showed that hydrated lime and liquid ASAs could be used to resist moisture damage, regardless of the aggregate source. In addition, the rut depths of Surface C mixtures were generally less than 5 mm, irrespective of aggregate source and ASA type. Moreover, various ASAs, aggregate sources, and surface types slightly affect the dissipated energy of wet samples. Furthermore, there are some general correlations between dissipated energy and its corresponded ITS values, in terms of aggregate source and surface type used in this study.

This paper presents a study evaluating the use of sludge ash as a stabilizing additive to soil-cement mixtures for use in base and subbase road pavements by investigating the mechanical behavior of these mixtures. The methodology consisted of materials testing, including the geotechnical characterization of the soil and the mechanics of the soil-cement and the soil-cement-sludge ash mixtures. An unconfined compression test evaluated the mechanical behavior of soil-cement mixtures with cement contents of 3, 6, and 9% compressed with normal, intermediate, and modified pressures. The sludge ash contents added were of 5, 10, 20, and 30%. The results indicate increasing strength for all ash levels studied. The largest gain in strength was for a mixture with 20% sludge ash, which increased the strength by 26% compared with the mixture without sludge ash.

The present investigation examines the efficiency of an in situ lime precipitation technique in stabilizing expansive soil through laboratory-scale model tests. Expansive soil was compacted in a cylindrical mold and sequentially permeated with ${\mathrm{CaCl}}_2$ and NaOH solutions into the expansive soil through a central hole filled with coarse sand. Successive permeation of ${\mathrm{CaCl}}_2$ and NaOH solutions into the compacted expansive soil resulted in precipitation of lime in the expansive soil mass. The precipitated lime reduced the plasticity index, controlled the swell–shrink potentials, and increased the unconfined compressive strength of the expansive soil by both strong lime modification reactions and soil–lime pozzolanic reactions. The results are corroborated with microfabric studies on lime precipitation treated specimens, which showed the formation of cementation bonds.