Journal of Materials in Civil Engineering

The objective of this study was to employ an artificial neural network (ANN) to predict asphalt-rubber (AR) rutting performance characteristics using binder properties, crumb rubber (CR) gradations, and mechanical test parameters. The scope included advanced asphalt binder rheological characterization using a dynamic shear rheometer (DSR), encompassing preparation of a total of 18 laboratory-blended AR binders with two base binders and nine CR gradations, totaling over 2,200 data points. Principles of ANNs were used to predict the three AR binder performance parameters: $\eta$, $G^{*}/\sin \delta$, and $\tan \delta$. Eight input parameters constituting test temperature and frequency, five CR gradation components, and base binder viscosity were employed to develop the ANN model. A back-propagation learning algorithm with scaled conjugate gradient (SCG) as the training algorithm in a feed-forward, two-hidden-layer neural network with seven and three neurons, respectively, was chosen as the best ANN architecture. The statistical goodness of fit measures $R$ for the total data set were, respectively, 0.994, 0.997, and 0.977 for $\eta ,G^{*}/\sin \delta$, and $\tan \delta$. ANN modeling conceptualized as part of the study indicated that rubber inclusions in asphalt binders would aid in the improvement of the materials’ rutting resistance. The magnitudes of weights and biases provided in this study for the eight chosen AR binder material input parameters could be well utilized in predicting the three binder material performance parameters. Overall, it is envisaged that the algorithm developed in this research pertinent to asphalt binders’ advanced rheological characterization would further the state of the art in designing rut-resistant rubber modified asphalts.

To reduce the dust pollution caused by the construction industry, calcium magnesium acetate (CMC), and glycerin as the primary raw materials, sodium dodecyl benzene sulfonate (SDBS) as the surfactant, and sodium hydroxide (NaOH) as the initiator were used to produce construction-site dust suppressant. This study focused on the preparation conditions of this dust suppressant and the dust-suppression effects of different dust-suppressant spraying methods. Tests of dust suppression derived from 1 h of reaction time, 70°C of reaction temperature, and 0.3 g of initiator dosage showed superior performance. The dust suppressant viscosity, hardness, antiwind erosion, and water retention capacity of the consolidated soil were improved greatly under this condition. Moreover, in experiments using different spraying methods, the method of spraying the dust suppressant instantly after water spraying worked best; the water-saving efficiency was increased by up to 92.62%, and the economic cost was reduced by 55.1% compared to the water-spraying method. This research can provide effective technical support for dust-suppression operations at construction sites.

Increased awareness of sustainability has resulted in the use of alternative supplementary cementitious materials in concrete construction. Volcanic ash (VA) is a prospective material available in the Gulf region that can be used to produce green and economical concrete. This paper reports the results of an elaborate study on the effect of incorporation of different percentages of VA on various mechanical and microstructural properties of hydrated cement paste with an objective to determine the optimal percentage of VA that can replace the ordinary portland cement (OPC) to obtain the maximum benefit. It is concluded from the studied mechanical and microstructural properties that an OPC replacement of 10–30% by VA brought out the maximum benefit. Further to this, the study confirmed that even though the incorporation of VA did not contribute positively towards strength development, a continuous and compact microstructure could be produced with an optimal percentage of VA.

The infiltration characteristics of two different hydrophobic materials were investigated in this study. The materials used in this study were fine and coarse recycled concrete aggregates (RCA). One-dimensional (1D) vertical infiltration column tests were carried out on fine RCA over coarse RCA, fine RCA over coarse RCA with oil, and fine RCA over coarse RCA with wax. The column apparatus were instrumented with a tensiometer-transducer system, data acquisition system, soil moisture sensor, and electronic weighing balance. The comprehensive instruments were used to measure pore-water pressure, water content, and outflow rate of water instantaneously and automatically. The experimental results indicated that the water flowed faster within the layer of coarse RCA with oil and wax as compared to that within the layer of coarse RCA without oil and wax. This could be attributed to the hydrophobicity of each solid particle of coarse RCA that was coated with oil and wax.

Recent studies have revealed that zyco-soil and nanosilica are among the nanomaterials that can help improve the moisture-damage resistance of asphalt mixtures. However, these also affect the properties of asphalt mixtures in different ways. For the first time, this study aims to compare their effects on some engineering properties of a typical asphalt concrete, the environmental impact, and the cost. The 60/70 penetration-grade asphalt cement was modified by adding different percentages of nanosilica (1, 3, and 5%, by the weight) and zyco-soil (0.1, 0.3, and 0.5%) content and evaluated using experiments. The results showed that nanosilica modification leads to higher resistance to permanent deformation, resilient modulus, and indirect tensile strength compared with zyco-soil modification. Beyond an optimum zyco-soil content of 0.1%, resistance to permanent deformation and resilient modulus of the mixtures decreases with increasing zyco-soil content. The results also showed that zyco-soil-modified asphalt mixtures are more resistant to moisture damage compared with the nanosilica-modified mixtures. However, the optimum zyco-soil content to achieve the highest resistance to moisture damage is different from that used to achieve stiffness and stability. For nanosilica, the optimum content to achieve the highest resistance to moisture damage and stability is the same.

The main cause of the deterioration of concrete structures is the corrosion of their reinforcement. The use of galvanized steel rebars is a competitive solution to increase the service life of structures. The bond of galvanized rebars with concrete has been studied in recent years, but some of the results of different research on bond capacity are slightly contradictory. In this paper, a study of the surface geometry of traditional and galvanized rebars has been carried out to discover the influence of galvanizing on the bond capacity of reinforcement. Furthermore, the bond behavior of four reinforced concretes combining black and galvanized rebars along with ordinary portland cement (OPC) concrete and concrete containing blast furnace slag (BFS) has been assessed through pullout tests at different ages and limit states. The surface geometry of the rebars changed slightly because of galvanization. The bond tests at 7 days showed lower stresses when galvanized rebars and BFS were employed. At 28 days, similar anchorage lengths could be used for the design regardless of the type of reinforcement and concrete employed. However, slight differences were noticed depending on the limit states analyzed.

Burnt clay bricks are commonly used in construction across the globe. The objective of this study is to explore the potential of using waste glass sludge (WGS) as a secondary material in clay brick manufacturing. WGS was collected during industrial-scale cutting and polishing of glass. Brick specimens were manufactured using various dosages (i.e., 5, 10, 15, 20, and 25% by clay weight) of WGS at an industrial brick kiln plant. A range of mechanical and durability tests were performed on the bricks thus produced to quantify their performance. Clay bricks incorporating WGS exhibited higher compressive and flexural strength as compared with that of control traditional clay bricks. The unit weight of bricks was reduced owing to WGS addition, which can lead to lighter and economical structures. Furthermore, the resistance against efflorescence, sulfate attack, and freeze-thaw was enhanced for all the clay bricks incorporating WGS. Scanning electron microscopy indicated a well-bonded and fused structure of brick specimens incorporating WGS. The findings demonstrate that WGS can enhance the physical and mechanical properties of clay bricks, leading toward more economical and sustainable construction.

Marine dredged clay may contain various types of organic matter that affect the properties of cement-treated clay. Organic matter in soils can be classified into two categories: nonhumic and humic. This work aims to evaluate the effects of humic acid on the strength development and microstructure of cement-treated marine clay with various curing times ranging from 5 h to 90 days. Strength development was investigated through a vane shear and unconfined compression tests with different water, cement, and humic acid contents. The microstructure was examined by X-ray diffraction and scanning electron microscopy. The results indicate that the strength development was governed by the cement and humic contents. Further, a threshold cement content, at which the adverse effects of humic acid on strength development are overcome, existed for a given humic acid content. Finally, a new compound was observed to form when humic acid was added to cement-treated clay.

The use of reclaimed asphalt pavement (RAP) in bituminous mixtures is considerably increasing due to the environmental and economic benefits of recycled materials. However, stiffer mixes, usually resulting from RAP addition, have raised concern about long-term properties of the pavement; a mechanical characterization of these mixes is thus needed. In this study, the effect of mixing condition on bituminous mixtures containing RAP was evaluated. Volumetric and mechanical properties were analyzed. An experimental program, with the aim of measuring stiffness modulus, water sensitivity, and cracking resistance, was conducted. Cracking resistance was evaluated according to the Fénix test because it has proved to be a convenient and effective method for characterizing cracking behavior of bituminous mixtures at different temperatures. Mixtures containing 20 or 40% of RAP material were tested; virgin aggregates and RAP mixing temperatures as well as mixing time were varied and comparisons with a reference mix were conducted to characterize fracture energy and mechanical performance.

Rutting or permanent deformation is one of the severe distresses manifested in flexible pavements caused by the various mechanisms such as densification, lateral plastic flow, and/or loss of materials under wheel path due to repeated heavy traffic loads. Various laboratory tests have been devised to determine the rutting propensity and to optimize the field performance of hot mix asphalt (HMA) mixtures as a part of the HMA mix and structural design processes. Although various approaches exist to predict the permanent deformation of HMA, this study develops a relationship of flow number (FN), dynamic modulus (DM), and uniaxial repeated-load permanent deformation (RLPD) to enable the trade-off analysis among them. Also, a novel parameter, FN index, is explored and used to determine the rutting potential of HMA mixtures. Twelve globally practiced HMA mixtures are investigated with three different performance grade binders and single limestone aggregate source. Superpave gyratory compacted specimens are subjected to performance testing (FN, DM, and RLPD) and results indicate a strong correlation of FN index with DM and exhibit better correspondence than the traditional FN (cycles) parameter.

An ordinary portland cement and two portland limestone cements [15 and 35% weight-to-weight ratio (w/w) limestone content] were used for concrete and reinforced mortar specimens preparation. The specimens were exposed to two corrosive solutions (chloride sulfate and chloride) at 5°C. Total (acid-soluble) and free (water-soluble) chloride contents, and apparent chloride diffusion coefficients, were determined in concrete specimens. Reinforcement corrosion half-potential and current density, mass loss of steel rebars, and carbonation depth were measured in mortar specimens. Limestone cements showed very good behavior, although the environments were very corrosive. Total and free chloride ions concentration increased with exposure time and limestone content. Limestone cements showed less capability of binding chlorides than pure portland cement. The cement with low limestone content was the most effective in preventing reinforcement corrosion during mortar exposure to the combined chloride-sulfate solution, although it allowed the most intensive corrosion in the case of the chloride-bearing solution. The presence of sulfates led to higher chloride ion concentrations, less chloride binding and, generally, higher values of chloride diffusion coefficient, and also promoted reinforcement corrosion to a greater extent. Low temperature conditions retained a relatively low corrosion rate.

Fly ash from fluidized bed combustion differs greatly from that of pulverized coal firing. The most noticeable differences are in morphology, reactivity, and chemical composition. The use of biomass fly ash from fluidized bed combustion as a cement replacement material could be a promising method for both minimizing the amount of landfilled fly ash and reducing ${\mathrm{CO}}_2$ emissions in the concrete and cement industry. In this study, fly ash from fluidized bed combustion of peat and forest industry residue was used as a supplementary cementitious material for portland-composite cement (CEM II) containing clinker, blast furnace slag, and limestone. Even with a 40% cement replacement ratio, the compressive strengths of the mortar samples were still as high as 88% of the control sample’s strength. Comparison with unreactive replacement material revealed that moderate hydraulic properties of the studied fly ash explained the positive effects on strength rather than filler or nucleation effects.

Dynamic loading may severely compromise the functional performance of concrete. The present study examined the effects of the partial replacement of fine aggregates with rubber ash (0, 5, 10, 15, and 20%) and hybrid rubber waste (0, 5, 10, 15, 20, and 25% of rubber fiber with 10% constant rubber ash) on the response of concrete to impact and fatigue loading. Impact performance of the resulting concrete was examined using a drop weight test, flexural loading test, and rebound test. Fatigue performance was assessed using a servo-hydraulic fatigue machine. Regression analysis to establish a relationship between different impact tests was carried out. A two-parameter Weibull distribution was used to analyze the results of the drop weight and fatigue tests to facilitate ease of analysis. Scanning electron microscopy (SEM) and optical microscopy were deployed to investigate the microstructural attributes of the rubberized concrete. It was found that the incorporation of rubber ash and rubber fiber in concrete led to enhanced resilience toward impact and fatigue loading.

This paper presents the effects of $\mathrm{nano}\text{-}{\mathrm{SiO}}_2$ and $\mathrm{nano}\text{-}{\mathrm{CaCO}}_3$ on the microstructure of high-volume fly ash (HVFA) cement paste. The microstructures of HVFA cement pastes containing 40 and 60% Class F fly ash were evaluated at 28 days using nanoindentation, X-ray diffraction (XRD), thermogravimetric (DTA/TGA), and mercury intrusion porosimetry (MIP) analyses. A reduction of calcium hydroxide (CH) was seen in XRD analysis of HVFA pastes containing nanoparticles. This observation was also confirmed in the DTA/TGA analysis. The nanoindentation results also showed the evidence of pozzolanic reaction in the HVFA pastes, where the addition of 2% $\mathrm{nano}\text{-}{\mathrm{SiO}}_2$ and 1% $\mathrm{nano}\text{-}{\mathrm{CaCO}}_3$ increased the volume fractions of high-density and low-density calcium silicate hydrate (C─ S─ H) gels and confirmed the ability of nanoparticles to reduce the porosity of HVFA pastes, which was consistent with the MIP analysis. The improved nanostructure and microstructure of HVFA pastes due to the addition of $\mathrm{nano}\text{-}{\mathrm{SiO}}_2$ and $\mathrm{nano}\text{-}{\mathrm{CaCO}}_3$ in this study show that high-strength and highly durable sustainable concrete can be produced with lower repair and maintenance requirements for the concrete structures.

Modification of asphalt binder with Elvaloy (Elv) and polyphosphoric acid (PPA) has been reported to have better performance. However, such modification may increase mixing and compaction temperatures of asphalt binder. Furthermore, the positive effect of PPA may get neutralized with the addition of lime, which can lead to inferior performance of asphalt binders. Recently, different types of warm mix additives (WMA) are being introduced to reduce production and construction temperatures of asphalt binder. However, the effects of WMA additives with and without lime on various rheological response of PPA + Elv modified asphalt binder is not well understood so far. Therefore, the present study was undertaken to evaluate the rutting and fatigue performance of PPA + Elv modified asphalt binder (referred as Control binder) containing three WMA additives (water, chemical, and wax-based) with and without lime. The multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests were conducted to capture the rutting and fatigue performance of asphalt binders, respectively. The results show that rutting and fatigue performance of Control asphalt binder decreased with the addition of chemical and water-based WMA additives. The performance of Control asphalt binder further deteriorated when these WMA additives (chemical and water) were used with lime. Interestingly, the addition of wax showed higher rutting resistance and similar fatigue life as that of Control asphalt binder. The addition of lime with wax additive showed improved rutting resistance and reduced fatigue life compared with Control asphalt binder. Regardless of the type of WMA additives, the addition of lime decreased the fatigue life of Control asphalt binder. The adverse effect of lime was prominent when used with wax compared with water and chemical-based WMA additives. Furthermore, the addition of WMA additives increased the stress sensitivity of Control asphalt binder. The stress sensitivity of asphalt binder further increased when wax and chemical-based WMA additives were used with lime. However, use of water-based WMA additive and lime reduced the stress sensitivity of Control asphalt binder. Overall, it can be concluded that the performance of Elv + PPA modified asphalt binder depends largely on the type of WMA additives and their combination with lime.

The mixture of activated paper sludge and fly ash can successfully be used as pozzolans for the manufacture of a more ecological portland cement. The saturation indexes and the mineral stability fields of a pozzolanic reaction are studied at 1, 3, 7, 28, 90, and 360 days into the reaction. The system is formed of a pozzolanic mix (activated clay waste and fly ash) and a saturated solution of $\mathrm{Ca}{(\mathrm{OH})}_2$ at 40°C. The behavior of the reactions is predicted in this study by means of a thermodynamic model running on a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. The concentration of soluble species in the aqueous solution is determined by inductively coupled plasma mass spectrometry. The evolution of the hydrated phases formed in this study and the mineral stability fields are evaluated with the geochemical programs PHREEQC and SUPCRT92. The hydrated phases produced during the pozzolanic reactions were C─ S─ H gels, ${\mathrm{C}}_{\mathrm{4}}\mathrm{A}{\mathrm{H}}_{\mathrm{13}}$ (calcium aluminate hydrate), ${\mathrm{C}}_{\mathrm{4}}\mathrm{A}\mathrm{c}{\mathrm{H}}_{\mathrm{12}}$ (calcium monosulfoaluminate), and layered double hydroxide (LDH)–type structures or hydrotalcite are anionic clays. The saturation index values indicate that the LDH-type structures (phyllosilicate/carbonate) are the most thermodynamically stable phase in the activated clay/fly ash–$\mathrm{C}\mathrm{a}\mathrm{(}\mathrm{O}\mathrm{H}{\mathrm{)}}_{\mathrm{2}}$ system after 7 days of reaction. Mineral stability fields situate all the samples among the LDH-type structures (phyllosilicate/carbonate).

The effect of cement tricalcium aluminate (${\mathrm{C}}_3\mathrm{A}$) content on the properties of cement paste, mortar, and concrete mixtures containing high-range water-reducing (HRWR) admixture was investigated. Three commercial Type I cements prepared with the same raw material and same gypsum rock interground with clinker, but with different ${\mathrm{C}}_3\mathrm{A}$ contents (by changing mixture proportions), were used. The fresh state, rheological properties, and compressive strength of the mixtures were studied. Moreover, X-ray diffraction (XRD) patterns of 6-h-age paste mixtures from each cement were obtained. By reducing the ${\mathrm{C}}_3\mathrm{A}$ content of the cements, the fresh state, rheological, and consistency retention properties of the mixtures improved; however, the strength of the mixtures at early ages decreased. The difference between strength of the mixtures closed at later ages. The XRD analysis of the pastes revealed the formation of more ettringite in the paste prepared from high ${\mathrm{C}}_3\mathrm{A}$ content cement.

Some researchers have used the fine aggregates matrix (FAM) as a means to evaluate the influence of material properties on the expected changes in the performance of hot mix asphalt (HMA). Based on the most commonly used definition, the FAM is composed of part of the fine aggregates (smaller than 1.18 mm), mineral filler, and asphalt binder. Different studies have used different methods to design such FAM mixes. In this study, the fatigue characteristics of different FAM designs (by varying their maximum aggregate size and binder content) were evaluated and compared to the fatigue characteristics of a corresponding full asphalt mixture. The goal of this exercise was to identify a FAM design that was most similar to the full asphalt mixtures in terms of its damage characteristics. The viscoelastic continuum damage approach was used to make such comparisons. Results show that FAM mixes with a maximum nominal aggregate size (MNS) of 2.00 mm have similar damage evolution trends as that of the full hot mix asphalt with a maximum aggregate size of 12.50 mm. Also, through the results and using a failure criterion based on energy, cyclic tests can be simulated at different loading conditions in order to construct Wöhler curves. The results showed that smaller MNS mixtures present better damage performance for strain levels lower than 500 microstrain.

Accurate determination of adhesion between asphalt binders and aggregates is essential to pavement performance. In this study, particle-probe scanning force microscopes were used to measure the adhesion between mineral microspheres representing the primary aggregate constituents and various control (PG 64-22 and PG 58-22) and modified binders. Unit surface energies were collected to differentiate the adhesion between various aggregate-binder pairs. Results showed that the alumina-binder pair exhibited the highest adhesion among various combinations. No monotonic trends were detected for adhesion between silica-binder or calcium carbonate-binder pairs. Height and amplitude scans were also performed to characterize microstructural variations between different modified binders.

This study investigates the effect of alumina nanoparticles (ANPs) on tension and fracture characteristics of polymer concrete (PC). ANPs with a maximum particle size of 50 nm were used at 0.5, 1.0, 2.0, and 3.0 wt.% of epoxy resin. Tensile strength, tensile failure strain, and fracture toughness ($K_{IC}$, $G_{IC}$, and $J_{IC}$) were determined experimentally. A PC with superior ductility showing a tensile failure strain of 4.89% (compared with 2.56% for neat PC) was observed at ANP content of 3.0 wt.%. Using ANPs in producing epoxy PC can significantly improve ductility ($+60.6\%$) and fracture toughness ($+131.8\%$) compared with neat PC. Scanning electron microscope (SEM), dynamic mechanical analyzer (DMA), and Fourier transform infrared (FTIR) observations were conducted to understand the role ANPs play to manifest the observed improvements in tension and fracture characteristics of PC.

This study investigated the effects of carbon nanotubes (CNT) as a binder modifier on the performance properties of asphalt binders and storage stability of polymer modified binders. Performance characteristics of CNT modified binders were investigated through physical and rheological tests such as penetration index (PI), viscosity temperature susceptibility (VTS), temperature susceptibility (TS), and frequency sweep tests. Furthermore, the influence of CNT on storage stability of styrene-butadiene-styrene (SBS) modified binders was investigated by measuring rheological properties like separation index (SI), separation ratio ($R_s$), degradation ratio ($R_d$), and softening point difference (SPD) of the triple nanocomposite. The results indicated that the addition of CNT decreased PI, TS, and VTS and improved physical and rheological properties of the asphalt binder. Also, the results showed a significant relationship between the CNT content and PI, TS, and VTS in CNT modified binders. Regarding storage stability, adding CNT to the SBS modified binder resulted in improved stability, indicating a strong interaction between the asphalt binder and SBS polymer.

Fracture behavior is an important parameter in evaluating mechanical properties, and it is related to crack risk and propagation in concrete. Freeze-thaw damage aggravates the degradation of mechanical properties and durability of concrete in a freeze-thaw environment, which is adverse to the safety of concrete structures. Although researchers have studied compressive, tensile, and bending strengths, the fracture behavior of concrete exposed to freeze-thaw cycles is frequently neglected. Additionally, fracture behavior is more sensitive to crack development caused by freeze-thaw damage. This paper was developed to investigate the influence of freeze-thaw damage on fracture behavior of concrete. Freeze-thaw cycles, compressive strength, and fracture energy tests were carried out. The results show that the toughness and fracture behavior both decrease with increases in freeze-thaw cycles, and this decrease becomes more obvious for concrete after a large number of freeze-thaw cycles, which should be considered seriously in the design of concrete in freeze-thaw environments. Air-entrained and mineral admixture concretes have better fracture behavior than fresh concrete after suffering the same freeze-thaw cycles. In particular, there exists good linear correlation between the fracture behavior and imposed freeze-thaw damage for various concretes.

Thermal power stations in most countries are burdened with the problem of fly ash disposal, and unless suitable uses are found for fly ash, it will pose a gigantic problem for the power sector. The disposal of huge quantities of fly ash without proper care significantly impacts the environment, particularly by creating soil and groundwater contamination. However, it is essential to note that fly ashes have many desirable properties that can find application in civil engineering in general and in geotechnical engineering in particular. This article reviews the literature dealing with the generation of fly ashes and briefly describes their desirable properties with respect to geotechnical and geoenvironmental applications. Desirable properties include pozzolanic reactivity along with mineralogical and morphological physiognomies that enhance surface adsorption of toxic heavy-metal ions. These properties are delineated further in this review article. The stabilizer effect on the geotechnical behavior of fly ashes is addressed with emphasis on morphological and mineralogical aspects. One of the limiting factors of stabilization, lime leachability and its effect on durability and long-term performance, is discussed. Various environmental concerns associated with the use of fly ashes are also addressed.

The water absorption properties of concretes measured by sorptivity test were investigated by using natural pozzolanic cements—CEM II/A and CEM II/B—and compared with those of ordinary portland cement (CEM I) concrete under varying water-curing periods. The mix design of concretes was made with an equal strength base at an age of 28 days under standard curing. The curing regimes include initial water curing periods of 3, 7, 14, and 28 days between continuous in-air and continuous in-water, and also 7-day delayed curing. Sorptivity and compressive strength tests were conducted at the age of 90 days. Although the difference between the sorptivities of air-cured concrete specimens for all cement types used is slight, under the water curing conditions, the differences between that of the CEM II/B concrete and those of the CEM I and CEM II/A concretes become significant. Also, considerable differences were obtained for the sorptivities of the CEM II/B concrete between the air-cured and continuous water-cured specimens when compared with those of the CEM I and CEM II/A concretes.

For decades the construction industry has been focused on developing new materials for minimizing environmental impact and improving the building insulation envelope. The use of certain wastes as additives for construction materials have been shown to be the best alternative. In particular, the fired clay brick industry has been highlighted as an optimal sector for incorporating such residues due to the large amount of mass flow and high temperatures involved in the manufacturing process. This paper assesses the feasibility of using wood chips from a pruned grapevine shoot as an additive for manufacturing fired clay bricks. Samples with different percentages of the additive were formed and tested. It is concluded that a maximum of 10% of wood chips can be added, which produces compressive strength values above $5\mathrm{N}/{\mathrm{mm}}^2$. In spite of thermal conductivity being reduced up to 50%, water absorption is raised up to 30%. Thus, bricks must be coated to prevent masonry damage.

This study carried out laboratory investigations of fatigue damage development of hot mix asphalt (HMA) by semicircular bending (SCB) test. Strength of the HMA specimen was first investigated at different loading rates, the results of which indicate an exponential relationship between strength and loading rate. The SCB fatigue test at stress-control mode was then performed at six levels of stress-strength ratio (SSR). Two fatigue life prediction models have been established accordingly based on the concepts of the nominal SSR and the authentic SSR. The latter model can better predict fatigue behaviors. As follows, another round of SCB fatigue test was continued to investigate the relationship between residual strength and fatigue damage evolution. Analysis of test results indicate that fatigue damage evolution is nonlinear and consists of two components: the accumulative damage development and last-cycle damage jump. A fatigue damage evolution model has been finally built based on the residual strength, which can capture the “sudden death” phenomenon of the fatigue damage process at stress-control mode.

In this comprehensive experimental study, the effects of recycled glass fiber on the drying shrinkage and mechanical properties of the self-compacting mortar and fly ash–slag geopolymer mortar were investigated. An experimental/analytical approach was adopted to characterize the mechanical properties (compressive and flexural strength) and the drying shrinkage rate of the reinforced self-compacting mortars and fly ash–slag geopolymer mortars with inclusion of different recycled glass fiber volume fractions and lengths. To this end, a total of 207 specimens were experimentally tested. Scanning electron microscope (SEM) images were used to detect the failure mechanism of recycled glass fibers. Moreover, based on the collected data, some empirical equations were developed to correlate recycled glass fiber volume fractions to the mechanical properties of the reinforced fly ash–slag geopolymer mortars and self-compacting mortars, considering high values of coefficient of determination. The experimental results showed that adding recycled glass fiber has much greater effects on increasing the flexural strength and decreasing the drying shrinkage rate in fly ash–slag geopolymer mortars when compared to self-compacting mortars.

This laboratory study evaluated the influence of interface characteristics on the bonding properties between open-graded friction courses (OGFC) and the underlying layer. One gravel OGFC and two commonly used underlying layers [one base material (BM) and one thin-layer D mixture (TLD)] were used in this study. The BM is a regular asphalt binder course mixture with 19-mm nominal maximum aggregate size, whereas the TLD is a thin asphalt surface-wearing course mixture with 12.5-mm nominal maximum aggregate size. A direct shear test was performed to obtain the shear strength and shear stiffness at different tack-coat application rates. Adhesive and cohesive failure types on the interfaces were identified. Noncontact area between OGFC and underlying was obtained. Results showed that there were no significant differences in adhesive failure area between OGFC-TLD and OGFC-BM. The cohesive failure area of OGFC-TLD was larger than that of OGFC-BM. The noncontact area between OGFC and BM was larger in contrast with the area between OGFC and TLD at the same tack-coat application rate. With an increase in tack-coat application rate, the adhesive failure area and noncontact area decreased and cohesive failure area increased. The shear force to overcome the adhesive bonding between OGFC and BM was larger than that of OGFC and TLD at the same tack-coat application rate because of the larger interface roughness caused by BM’s coarser aggregate gradation. At the optimal tack-coat application rates for OGFC-TLD and OGFC-BM, the difference in shear force to overcome the cohesive bonding between OGFC-BM and OGFC-TLD was very slight. The shear force to overcome the adhesive bonding is the factor that made the shear strength and shear stiffness of OGFC-BM larger than those of OGFC-TLD.

In situ attenuated total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to investigate the gel formation of a natural pozzolan-based geopolymer and its relation to mechanical strength. For this purpose, geopolymer samples were prepared with different concentrations of ${\mathrm{SiO}}_2/{\mathrm{Na}}_2\mathrm{O}$ (Si/Na) and ${\mathrm{Na}}_2\mathrm{O}/{\mathrm{Al}}_2{\mathrm{O}}_3$ (Na/Al) molar ratios in an alkali activator. The in situ ATR-FTIR showed that Si─O─T (T=Si, Al) stretching bond shifted to lower wave numbers with any increase in Si/Na molar ratio because of an increase in the geopolymerization reaction rate. The key finding of the present work is the relation between changes in gel molecular structure and the strength results demonstrated in different Si/Na and Na/Al molar ratios. Results showed that in high Na/Al and Si/Na molar ratios, Si─O─T bonds are formed at a lower wave number due to the presence of more Si─O species and increasing Al substitution in the silicate network of the geopolymer, which led to higher compressive strength.

The potential for self-healing of concrete via biomineralization processes in which microorganisms influence mineral precipitation is promising. To embed microorganisms within a cement-based material, key challenges are to find a microorganism that can tolerate the highly alkaline conditions, survive the mixing process, and remain viable with limited access to nutrients. The focus of this work is to determine the metabolic state of unencapsulated Sporosarcina pasteurii, inoculated vegetatively, in a cement-based matrix over time and to examine its ability to remediate internal cracks and reduce porosity. Viable S. pasteurii was found in hardened mortar samples that were as old as 330 days, and 48% of the viable cells detected were vegetative. A greater fraction of the inoculated cells remained viable in mortar as compared to cement paste, which is promising because mortar is a better representation of the composite nature of concrete than cement paste. Furthermore, as compared to neat paste and neat mortar, addition of the vegetative cell culture to bacterial paste and bacterial mortar resulted in reduced porosity. Bacterial mortar also demonstrated increased strength recovery as compared to neat mortar. The reduction in porosity and increase in mechanical regains demonstrated by the bacterial mortar suggest improved durability and service life for bioconcrete as compared to traditional concrete.

In this paper, the effects of key mix parameters, including asphalt–cement ratio (A/C), water–cement ratio (W/C), and sand–cement ratio (S/C), on the dynamic mechanical properties of the cement asphalt (CA) mortar used in the ballastless slab track of high-speed rail were investigated by dynamic mechanical thermal analysis (DMTA). Results showed that storage modulus ($E^{\prime }$) increased with increased S/C ratio and decreased A/C and W/C ratios. The damping ability of CA mortar, which is characterized by $\tan \delta$, increased with increased A/C and W/C ratios. In comparison with Type-II CA mortar which has a lower A/C ratio, $\tan \delta$ of Type-I CA mortar with a higher A/C ratio presented a different dependency on the S/C ratio. Relationships between dynamic mechanical properties ($E^{\prime }$ and $\tan \delta$) and volume fraction of phases in CA mortar were quantitatively established.

In this study, a shape memory alloy (SMA) and general rubber bearing are used to develop a novel SMA–rubber bearing combination. This bearing is then used to develop a smart isolation system that can achieve vibration control in a bridge structure during earthquakes. The system design is based on a martensitic NiTi SMA (atom fraction of $\mathrm{Ni}=51\%$) with a production diameter of 1.0 mm. The damping provided by the NiTi alloy is frequency dependent and increases with prestrain and amplitude. To investigate the basic mechanical behavior of the designed SMA-rubber bearing, three-dimensional finite-element models were constructed and the optimized parameters of the bearing were analyzed to investigate their effects on mechanical behavior. To assess the isolation effectiveness of the bearing, a simply supported beam bridge with different bearings was investigated under various earthquake excitations to compare the effects of vibration isolation. Through optimization analysis, design parameters for prestrain (3.0–4.0%), $\alpha$ value (18–25°), and Shore hardness were obtained. An application analysis showed that the proposed bearings limit the relative displacement of a bridge deck effectively under strong ground motions and that they almost completely recover their original shape.

Scaling, erosion, and cracking are some manifestations of deterioration of concrete surfaces due to chemical attack, exposure to cyclic freezing and thawing, and so forth. Though a rating of the surface can be done visually using some standard method, such an evaluation still remains largely qualitative and subjective. For laying down specifications and maintenance of structures, quantitative and objective methods are required to assist objective decision-making. This paper reports the results of the application of a modified version of a test procedure that is used to determine the surface texture of pavements using concrete specimens subjected to accelerated deterioration due to cyclic freezing and thawing. It is found that the test can be used in conjunction with others to maintain an objective and quantitative record of deterioration of surface characteristics. The fact that the test is nondestructive, noninvasive, and requires only minimum training of workers and simple tools, makes the proposition of using this test more attractive. A possible classification that can be used for specification writing and maintenance of structures is also suggested.