Journal of Materials in Civil Engineering

Two-stage concrete (TSC), also known as preplaced aggregate concrete, is produced through placing coarse aggregate particles in the formwork and subsequently injecting grout to fill the interparticle voids. The ability of the used grout to flow around the preplaced aggregate particles and effectively fill voids has a predominant effect on the TSC properties. Due to the unique formulation of TSC grouts, rheological studies on other common cementitious grouts do not readily apply to TSC grouts. In particular, the effects of different supplementary cementitious materials (SCMs) on the properties of TSC grout mixtures remain largely unexplored. Therefore, in the present study fresh and hardened properties of grout mixtures incorporating various SCMs, including fly ash (FA), silica fume (SF), and metakaolin (MK), were investigated. Results indicate that a water-to-binder ratio $(\mathrm{w}/\mathrm{b})=0.45$ was suitable to achieve the recommended grout flowability for successful TSC production. Moreover, TSC grout properties highly depended on the type and dosage of SCM used. The findings of this study should stimulate further research and novel applications of TSC, considering that the TSC technology has remained so far basic and needs to accommodate recent advancements in cement-based materials.

The thermal energy storage (TES) capacity of building materials can be enhanced by using phase change materials (PCM). In this work, the building composite PCM was prepared by impregnation of n-heneicosane (HE) as an organic PCM into bentonite (BNT) clay. The chemical, morphological, and thermal characterizations of the developed BNT/HE composite PCM was performed by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis techniques. The SEM and FT-IR results showed that the HE was well incorporated into the pores of the BNT and had good compatibility with the components of the composites. The DSC analysis results showed that the composite including 36% HE by mass had a melting temperature of 38.32°C and solidification temperature of 38.34°C; in addition, the composite also can store latent heat of $96.23\mathrm{J}/\mathrm{g}$ and release latent heat of $94.16\mathrm{J}/\mathrm{g}$. The TG analysis demonstrated that the developed composite PCM had good thermal durability. The thermal cycling test confirmed that the composite had good long-term thermal reliability and chemical stability. The laboratory-scale thermoregulation performance test revealed that the BNT/HE composite PCM wallboard had the effect of decreasing the indoor temperature of the building cell for a considerable period. Use of the developed BNT/HE composite PCM as a wallboard in the construction of energy-efficient buildings will open new practice opportunities in the building industry for passive solar heating, ventilating, and air conditioning (HVAC) purposes.

In this study, the role of the dewetting mechanism in moisture damage of asphalt pavements was investigated. Three main asphalts, and mainly two antistrip additives, were utilized. A unique dewetting-based moisture damage test procedure was developed consisting of a moisture conditioning procedure and quantitative analysis of the dewetting with the use of a microscope and an application software. The dewetting analysis procedure includes measurements of the total dewetted area and number of dewetted holes. It was observed that the dewetting phenomenon occurs primarily under a trapped air bubble in the asphalt film submerged in water. Polymer (styrene butadiene styrene) in PG 76-22M (modified) asphalt did aid in reducing dewetting. At high pH, 10, the Adhere LOF 6500 additive increased dewetting for all three asphalts. The critical film thickness for all three asphalts was estimated experimentally and found to be 300 μm. The findings of this study on understanding the role of dewetting on moisture damage in asphalt pavements will assist in the implementation of a unique dewetting-based moisture damage test procedure and analysis.

The production of rice-husk ash without controlled burning results in pozzolans with different physicochemical characteristics. The amorphous content of residual rice-husk ash (RRHA) is related to the temperature and exposure time during burning, whereas the BET specific surface area depends on the siliceous structure formed during plant growth, in addition to burning and grinding methods. In this study, amorphous content was quantified by X-ray diffraction (Rietveld refinement) in three RRHA samples randomly collected from rice mills located in southern Brazil, in which the burning process was not controlled. Pozzolanic activity evolution of RRHA samples in lime paste was monitored by thermogravimetry for 182 days in order to determine the influence of the lime:pozzolan ratio, BET specific surface area, and average particle size. The results show that lime consumption is not significantly affected by the BET specific surface area or average particle size of RRHA samples with a high amorphous content ($>66\%$). The reaction rate of RRHA depends on the lime:pozzolan ratio. Lime consumption per unit surface area of RRHA declines with an increase in the BET specific surface area. Because the proposed shape factor connects the BET specific surface area and average particle size of RRHA and indirectly includes the amorphous content of RRHA samples, it can therefore be used as an indicator of RRHA reactivity.

This study investigated the purifying effect of tourmaline-modified asphalt on automobile exhaust. Six types of tourmaline-modified asphalt concrete were prepared, aiming to achieving excellent exhaust-purifying performance. The purifying effect of tourmaline-modified asphalt slabs on automobile exhaust was emulated indoors through using an exhaust-gas analyzer and a self-made air purifier chamber in the cooling process of the specimens. Then, the influence of laws of the cooling rate of the slabs, dosage of tourmaline, types of tourmaline, and method of tourmaline being added upon the purifying performance were studied systematically. The mechanism of purifying performance of tourmaline-modified asphalt concrete was analyzed through a thermoelectric property test. Finally, the road performance of tourmaline-modified asphalt concrete was evaluated through a relative performance test. The results show that tourmaline-modified asphalt concrete has a good purifying effect on automobile exhaust, especially on ${\mathrm{NO}}_{\mathrm{x}}$ (nitrogen oxide compounds), where the maximum purifying rate can reach 93.1%. The purifying effect of tourmaline-modified asphalt concrete on automobile exhaust is improved by the increase of cooling amplitude and dosage of tourmaline. Purification effects of asphalt concrete with tourmaline anion powder on exhaust was improved with an increase in anion emissions; however, the purifying effect of tourmaline-modified asphalt on ${\mathrm{NO}}_{\mathrm{x}}$ tends to decline with the increasing fineness of tourmaline. Thermoelectric test results show that the thermoelectric property of tourmaline can still perform well when it is added to asphalt. The high-temperature performance, low-temperature performance, and water-resistance performance of asphalt concrete could be improved clearly by using a tourmaline additive.

Corrosion of reinforcing steel is the primary degradation mechanism by which the long-term durability of RC structures can be seriously impaired. In order to mitigate reinforcement corrosion, impressed current cathodic protection (ICCP) is becoming an interesting option to be used in practice on real structures. In this study, the electrical field distribution of ICCP systems for RC structures with complicated geometry and multiple corrosion boundaries is investigated by using a finite-element method (FEM) numerical simulation method. The numerical optimization scheme for ICCP to control corrosion of RC structures is developed by tuning the amplitude of the impressed voltage, as well as the location and area size of the anode layer. Two prototypes of ICCP systems for RC structures are built to verify the effectiveness of the optimization algorithm under laboratory conditions. The testing results indicate that this optimization design scheme of ICCP systems can effectively control the corrosion of RC structures with multiple boundary conditions.

Making use of low-cost alkali activators to produce suitable binders can play a key role in replacing portland cement by alkali-activated binders. The most effective and common activators are often based on sodium hydroxide and/or sodium silicate, which are relatively high in cost. In this study, attempts were made to develop suitable activators incorporating low-cost alkali and alkali earth metal-bearing salts for phosphorus slag. To fulfill this purpose, plain NaOH as a control activator as well as combinations of the control activator with ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and also a combination of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and $\mathrm{Ca}{(\mathrm{OH})}_2$ at different proportions were used to activate ground phosphorus slag. To evaluate the cementing property and soundness of the resulting mixes, compressive strength and efflorescence severity data were employed, respectively. Two suitable cement mixes were then selected and their chemical bond structure and the rate of adiabatic heat release were characterized by means of Fourier transform infrared spectroscopy (FTIR) and adiabatic calorimetry data, respectively. Finally, cost assessment done on the corresponding low-cost activators of the selected cement mixes revealed significantly lower cost-to-compressive strength ratios compared to the conventional control activators.

Asphalt concrete is a typical self-healing material, and its self-healing rate is influenced by the temperature. Since microwave irradiation is an efficient way of heating, its use could be a novel approach to heating asphalt pavement. In this study, ferrite particles were mixed into asphalt-based composites to upgrade the microwave absorbing efficiency and then further accelerate the self-healing rate of the composites. The microwave-absorbing capability of three kinds of aggregate and three kinds of filler were studied first. It was found that NiZn ferrite has an excellent microwave-absorbing capability under 2.45 GHz compared to other tested materials. Then the heating rate of asphalt mastic, asphalt matrix, and asphaltic concrete mixture with and without NiZn ferrite fillers were tested. The microwave heating rates of these composites all increase significantly with an increase in NiZn ferrite content. Third, the temperature uniformity of asphalt composites was investigated using an infrared thermal imager and a statistical analysis method. It was found that adding adequate amounts of ferrite fillers could notably improve temperature uniformity. Then, through electromagnetic measurement, it was confirmed that the addition of NiZn ferrite particles to mastic confers an excellent microwave-absorbing capability in a frequency range of 1–2.5 GHz compared to plain asphalt mastic. Finally, a fatigue–rest–fatigue test was used to investigate the effect of microwave heating on the self-healing behavior of ferrite-filled asphaltic concrete mixtures. It can be concluded that the healing capability of asphalt concrete can be significantly increased by ferrite particles’ superior microwave absorption properties, leading to the extension of fatigue life.

Reflecting the need to protect concrete structures from deicing salt and freeze-thaw loading, the study introduced in this paper springs from the uncertainty that exists in the benefit of in situ performance of isobutyl silane as a protection material. It is likely that environmental loading and internal moisture at the time of application are the main contributory factors for underperformance. This paper deals with alternative materials—a high-solids silane and an aqueous crystallization solution—operating by a moisture-driven crystallization mechanism rather than demanding a dry application regime. The results demonstrated similar substantial performance reduction of both materials at 0–5% moisture on medium-strength (C25: $25\mathrm{N}/{\mathrm{mm}}^2$) and high-strength (C40: $40\mathrm{N}/{\mathrm{mm}}^2$) concrete. There is greater take-up of protection materials by C25 concrete than by C40 concrete, together with greater chloride reduction, indicating that the level of achieved dosing is a significant factor. The similarity between the absorption of water and of the two protection materials relative to initial water content points to a possible basis for predicting achievable dosing of surface-applied protection materials. The crystallization material achieved greater application volume and chloride reduction than the silane material.

A number of completed or ongoing studies on warm mix asphalt (WMA) and steel slag (SS) asphalt mixtures have been conducted all over the world. This paper presents the results of a laboratory study aimed at verifying the damage behavior of WMA mixtures containing electric arc furnace (EAF) steel slag. The SS was used as the fine and coarse portions of aggregate gradation in hot mix asphalt (HMA) mixtures and as the coarse portion of aggregate gradation in a WMA mixture. The physical, chemical, and mechanical properties of aggregates and binders were evaluated to identify their effects on the moisture susceptibility, fatigue, and rutting behavior of asphalt mixtures. The moisture susceptibility of the asphalt mixtures was also evaluated using four different methods, including Marshall stability ratio, resilient modulus ratio, tensile strength ratio, and fracture energy ratio, and the fatigue and rutting behavior of the mixtures was evaluated using four point beam fatigue and dynamic creep tests, respectively. The results generally indicated that the use of coarse SS aggregate in WMA mixtures enhances the resistance of asphalt mixtures to moisture damage and permanent deformation. Also, WMA mixtures containing SS aggregates as the coarse portion of aggregates has better fatigue performance than HMA mixtures. Hence, the WMA mixture containing EAF steel slag aggregates is recommended as an eco-friendly, economical, and suitable mixture for pavement industries.

The coefficient of thermal contraction or expansion (CTE) of asphalt mixtures is a property that describes how asphalt mixtures respond to thermal loading during cooling or heating. The CTE is an important mixture property used as an input parameter in the thermal cracking model of the AASHTO Mechanistic Empirical Pavement Design Guide software. CTE measurement has proven quite a challenging task; however, many researchers have developed various methods for measurement using linear variable differential transducers (LDVTs), which have proven robust and suitable for routine tests. In this paper, a laboratory test method was devised using LVDTs to measure the CTE and determine the asphalt mixture properties affecting the CTE. The mixture properties investigated in this study included binder grade, binder content, the presence of recycled asphalt pavement (RAP) and recycled asphalt shingles (RASs), compaction effort, aggregate CTE, and size and aging. Mixture properties such as binder grade, binder content, aging, and the inclusion of recycled materials (RAP and RAS) resulted in a significant change in the CTE and the glass transition temperature ($T_g$) of mixtures.

Crack growth data are among the key parameters needed to characterize the materials used in asphalt concrete fatigue and fracture tests. The purpose of this study is to investigate the use of the digital image correlation (DIC) technique in monitoring the progression of damage and quantifying the length of cracks in asphalt concrete fatigue and fracture tests. To this end, cyclic interlayer shear tests and four-point bending notched beam fatigue tests were performed on double-layer fiberglass grid-reinforced asphalt concrete specimens. The tests were performed at 20°C and at frequencies of 5 and 10 Hz for the cyclic shear and bending beam fatigue tests, respectively. The full-field displacement and strain contours derived from DIC analysis of the specimens’ surface images proved to be powerful tools for monitoring the damage progression in the asphalt specimens under fatigue loading and for developing crack tip detection methods. Crack length measurement methods were developed based on DIC analysis displacement and strain results and were used successfully to determine interfacial crack lengths in the shear tests and vertical and interfacial crack lengths in the four-point bending notched beam fatigue tests.

This paper presents the results of extensive experimental tests on the fresh and hardened properties of self-compacting concrete reinforced with hybrid polypropylene (PP) fiber and recycled steel fiber (RSF) in different fiber volume fractions. In the present paper, RSFs were recovered from waste tires. The mix compositions were reinforced with different combinations of hybrid recycled-steel fiber (0.35, 0.7, and 1.05%) and PP fiber (0.35 and 0.7%). The fresh state of the mix compositions were assessed by using slump flow diameter, T500, and Tv. Moreover, the hardened properties of specimens were characterized by using compressive strength, flexural strength, and impact resistance. Regression analysis was executed on the relatively large amount of gathered experimental data to correlate properties of fresh and hardened states of self-compacting concrete reinforced with hybrid recycled steel–PP fibers. The results showed that adding hybrid recycled steel–PP fiber improves the impact resistance and mechanical properties. Adding recycled steel fiber led to higher improvement in the compressive strength compared to PP fiber. Moreover, increasing the content of PP fiber reduces the effect of recycled steel fiber in improvement of flexural strength.

Adhesively bonding fiber-reinforced polymer (FRP) composites to reinforced concrete members is a simple and highly effective method to restore strength, increase loading capacities, and extend the service life of structures. With growing demand and wider applications of these strengthening systems, it is their durability that has recently received significant attention from the research community, largely in the form of laboratory testing of deteriorated FRP-to-concrete joints. To develop generalized deterioration factors, a database of shear tests has been collected to quantitatively assess the change in bond characteristics across a number of environmental conditions. It has been identified that a major shortcoming of existing test data is that reporting of the full-range load-displacement behavior is very limited. To supplement existing data, an experimental study is devised to further assess the deterioration of carbon FRP bonded systems under three aqueous conditions. The investigation consists of continually immersing specimens in water, a 5% salt solution, and, for the first time, a sulfuric acid solution of pH 4.0 to simulate the pooling of acid rain. Results show that sulfuric acid attack is most detrimental to the durability of the bond. Then, using a mechanics-based numerical model, bond properties are extracted from the present results as well those in published literature, to determine conservative deterioration factors for the change in bond characteristics with environmental exposure.

This paper evaluates the effectiveness of stabilizing expansive soil with two different types of fibers, fiber mesh (FM) and fiber cast (FC), in conjunction with chemical stabilization. The intention of this study is to evaluate the effect of these fibers and lime in stabilizing expansive soil by improving its unconfined compressive strength (UCS) behavior. The effect of varying lengths (6 and 12 mm) and amounts (0.2, 0.4, and 0.6% dosage by weight of soil) of FC and FM fibers and varying curing periods (0, 7, 28, 60, 120, 180, and 360 days) on the UCS and on secant modulus of a semiarid expansive soil, in the presence of lime, was investigated. The main focus of this paper is on the determination of optimum fiber reinforcement parameters (in terms of fiber type, length, and dosage) for the stabilization of expansive soil in terms of UCS, which is of a prime importance in soil stabilization projects for practicing engineers. In deterministic optimization, the uncertainties associated with pavement system subgrade soil are not explicitly taken into account. Hence, resulting optimal solutions may lead to reduced pavement reliability levels. Therefore, this paper also focuses on determining the optimum amounts of reinforcement for desired UCS performance of lime-blended expansive soil using the target reliability approach (TRA). Experimental data were used to develop a parabolic model including factors such as length and dosage of fiber types to predict UCS as a response variable. In addition, it was concluded that TRA can be successfully employed in expansive soil stabilization applications to determine the optimum length and dosage of fiber reinforcements.

A comprehensive research was conducted to study the performance of a variety of stabilized geomaterials against the freeze–thaw (F–T) cycling process. Also included were unstabilized recycled materials, i.e., recycled asphalt pavements (RAP) and recycled concrete aggregates (RCA). Stabilized geomaterials used in this study included natural coarse-grained and fine-grained soils and reclaimed pavement materials (RPM). The stabilizers (binders) included self-cementitious fly ashes (i.e., class C and off-specification fly ashes). Resilient modulus ($M_r$) performances of geomaterials and geomaterials stabilized by binders were evaluated under a number of F–T cycles. This article also compares the F–T performances of different geomaterials including, stabilized coarse-grained versus fine-grained geomaterials, stabilized natural soils versus stabilized RPMs versus unstabilized RAP versus RCA. Additionally, the impact of fly ash type and fly ash content on F–T performance of stabilized geomaterials was also investigated. Moreover, correlations between the physicochemical properties [CaO, $\mathrm{CaO}/{\mathrm{SiO}}_2$, $\mathrm{CaO}/{\mathrm{Al}}_2{\mathrm{O}}_3$, $\mathrm{CaO}/({\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{SiO}}_2)$, $D_{60}$, $D_{30}$, gravel-to-sand (G/S) ratio and fines content] of these stabilized and unstabilized geomaterials and their resilient modulus were explored under F–T cycling. $M_r$ decreases (7–50%) in response to F–T cycling and then levels off in approximately 1–5 cycles. Fly ash stabilized coarse-grained geomaterials provided 5% less drop in initial $M_r$ compared to the fly ash stabilized fine-grained soils. RPMs stabilized with fly ash performed better (average reduction of 25%) against F–T cycling than the unstabilized RAP materials (average reduction of 33%) and natural fine-grained soils (average reduction of 29.5%) stabilized with fly ash. No correlations were found between the fly ash types/fly ash contents and $M_r$ performance of fly ash stabilized geomaterials under F–T cycling process. Fly ash stabilized coarse-grained geomaterials with higher $D_{60}$, $D_{30}$, G/S ratio, and fines content tend to lose more stiffness at higher number of F–T cycles. Such correlations could also be determined for RCA and RAP except G/S ratio. Stabilized fine-grained and coarse-grained geomaterials with fly ashes having higher $\mathrm{CaO}/{\mathrm{SiO}}_2$, $\mathrm{CaO}/{\mathrm{Al}}_2{\mathrm{O}}_3$, and $\mathrm{CaO}/({\mathrm{SiO}}_2+{\mathrm{Al}}_2{\mathrm{O}}_3)$ ratios experienced lower loss in $M_r$ during F–T.

This paper presents a detailed study on the use of glass powder (GP) as a binder in engineered cementitious composites (ECC). It investigates the effect of different levels of GP on the mechanical, physical, and self-healing efficiency of ECC. To assess recovery in GP-ECCs, multiple beams were preloaded up to 60% of their original flexure deformations at the age of 28 days and left to heal under moist curing. Compressive and flexural strengths, midspan beam deflection capacity, rapid chloride penetration, and resistivity tests were used to assess the performance of different ECC mixtures. To better understand the effect of GP content on the self-healing quality of ECCs, microstructural analysis was also performed via scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) in the surface and core regions of healed cracks. The results of this study show that production of ECCs with GP is possible, even at 100% GP replacement level with fly ash (FA). Acceptable physicomechanical behaviors can be achieved with 50, 75, and 100% GP replacement, with better performance at 25%. This study also confirms the good self-healing capability of GP-ECCs, especially at a 25% replacement level.

The granite processing industry, due to its sawing and polishing activities, is responsible for producing an enormous quantity of granite powder waste, herein referred to as granite industry by-product (GIB). GIB is a hazardous pollutant that poses a threat to ecosystems, thus emphasizing the urgent need to find a sustainable and technologically viable way of utilizing GIB and thereby minimizing its risks. The paper aims to assess the feasibility of GIB as a possible sand replacement in the manufacturing of concrete. At a 0.50 water-to-cement ratio (w/c), feasibility studies were performed and analyses were done for 10, 25, 40, 55, and 70% sand replacement by GIB in the manufacturing of concrete. Strength and durability of concrete with different percentages of GIB particles were ascertained by comparing the results of compressive strength, flexural strength, abrasion, shrinkage, permeability, carbonation, acid attack, chloride penetration, and corrosion tests with the results from a control concrete. Test results were ably explained by using auxiliary analyses such as scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The encouraging results proved the suitability of GIB concrete as a sustainable construction material. Optimal replacement level of river sand by GIB was found to be 25%.

This study aimed to evaluate the effect of the accelerated carbonation curing process as an alternative to preserve sugarcane particles and the physical–mechanical properties of cement–bagasse panels after accelerated aging tests consisting of 200 wetting and drying cycles. The cement–bagasse panels were produced with a nominal density of $1.25\mathrm{g}/{\mathrm{cm}}^3$ and subjected to two curing processes: (1) an initial 48-h cure in a controlled environment (temperature 60°C; 90% relative humidity) for 25 days, then in a saturated environment; and (2) an initial 48-h cure in a controlled environment (60°C; 90% relative humidity), followed by a carbonated cure (15% ${\mathrm{CO}}_2$ concentration) for 24 h and a further 24 days in a saturated environment. After 28 days of curing, the panels were subjected to accelerated aging tests. The results indicate that the accelerated carbonation preserved sugarcane bagasse, and carbonated panels had inferior physical properties and superior mechanical properties when compared to the noncarbonated version after accelerated aging tests, proving the efficiency of curing by accelerated carbonation as an alternative to the preservation of the physical–mechanical properties of cement–bagasse panels.

This paper shows that besides the particle size reduction, prolonged high-energy ball milling of portland cement leads to mechanically induced phase transformation from the crystalline to the amorphous state. This research has also investigated the improvement of the mechanical and microstructural properties of cement pastes incorporating mechanically activated cement milled for various durations as partial replacement of the unprocessed cement. Results have shown that compressive strength increases with prolonging mill duration as well as the amorphization degree of the processed cement. The setting times and porosity are significantly reduced, and the degree of hydration is improved by increasing the mill duration and the amorphization degree of the modified cement. The most significant results were observed when 10% by weight of amorphous cement was added to the unprocessed cement. In this experimental condition, the compressive strength was increased by 107% (at 28 curing days), the initial and final setting times were reduced approximately threefold, the porosity was reduced by 52%, and the early degree of hydration was improved by 162%.

This paper investigates the normal hardness, the compressive strength, and the modulus (parallel to the grain) of Pinus caribaea var. hondurensis wood in pristine condition and impregnated with methyl methacrylate (MMA) in autoclave at 0.22 and 0.66 MPa. An artificial weathering over a period of 2,400 h was used to better assess its effect upon the mechanical properties of impregnated wood. The analysis of variance identified that MMA impregnation significantly affected the responses; in contrast, no effect was verified by the artificial aging factor. Treated Pinus wood at 0.66 MPa achieved superior mechanical properties compared with the pristine condition, revealing percent increases in compressive strength, stiffness, and hardness of 84, 36, and 347%, respectively. The scanning electron microscopy (SEM) analysis revealed the MMA polymer was able to fill the wood pores completely. Possibly, impregnated Pinus wood can be used in structural applications in civil construction, in addition to being a low-cost specie in comparison to the typical high-density wood commonly used.

The Spanish Fortress of Bizerte in Tunisia shows differential erosion patterns on the rock ashlars used in the construction of its main façade (sixteenth century) exposed to marine aerosol action and several restoration works. In order to determine the origin of this erosion and the degree of stone decay, a combination of microdestructive and nondestructive techniques have been used on-site and in the laboratory. Moisture measurements, ultrasonic velocity propagation, and water absorption by a Karsten pipe test, together with polarized light and fluorescence optical microscopy, mercury intrusion porosimetry, and ion chromatography analyses, were carried out to perform petrophysical characterization of stone samples and determination of soluble salts. Results show that the differential stone weathering is caused by small variations in the petrographic characteristics of the construction’s geomaterials, such as the type and degree of cementation, porous network configuration, and presence or absence of soluble salts. These variations are also detected by the portable nondestructive techniques, showing their analytical sensitivity to small petrophysical changes even in the same type of rock and their performance in predicting future degradations not currently visible on the surface of the rocks.

Bleeding occurs when a freshly mixed cement-based material starts to settle. Severe bleeding can have a significant impact on the durability of concrete. The present study examines the effects of four materials—superplasticizer, viscosity-modifying agent, silica fume, and limestone filler—on the bleeding behavior of self-compacting concrete and the effects of bleeding on the quality of concrete. In the study, slump flow, L-box, V-funnel, and sieve segregation of 29 self-compacting concrete mixtures were evaluated. The entrained air of the concrete mixtures was assessed using an aerometer. The yield stress and the plastic viscosity of the concrete mixtures were measured using a rheometer. The results show that the rheological properties of self-compacting concrete mixtures are closely related to their bleeding index.

Bacterially induced mineral precipitation is a general phenomenon in nature. Ureolytic bacteria have been used in many studies as an environmentally friendly method for the protection and improvement of strength of cementitious materials. However, the ammonia produced by ureolytic bacteria during this biomineralization is harmful for the health. This paper incorporates a nonureolytic bacteria of the genus Bacillus, and investigates its effect on various mechanical properties of cement mortar such as compressive strength, setting time, soundness, sorptivity, and microstructural morphology. Outcomes from this study revealed that the nonureolytic bacteria performs better than ureolytic bacteria, as reported by previous studies with regard to compressive strength. The other engineering properties have also been improved by the addition of nonureolytic bacteria. This novel biological precipitation shows promising prospects for increasing the strength and durability of concrete constructions without hazard associated with generation of ammonia.

Cement pastes and mortars were prepared incorporating carbon nanotubes (CNTs) and nanofibers (CNFs) synthesized directly on ground clinker and silica fume. Setting times of the cement pastes were not significantly influenced by the presence of nanotubes and nanofibers. Mortar mechanical behavior (compressive and flexural tensile strength) was evaluated and compared with reference mortars having the same composition but without nanotubes and nanofibers. The mortars incorporating nanostructured clinker showed 5.4–14.1% higher compressive and flexural tensile strengths, respectively. The same values for the mortars prepared with nanostructured silica fume were 39.6 and 9.4%, respectively. Gas adsorption porosimetry and helium pycnometer analysis showed modification of the pore structure as an effect of nanostructured material addition: pore diameter decreased, specific surface area increased, yet density of the mortars remained unchanged.

This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and compositional changes were evaluated using microscopic, spectroscopic, and diffraction techniques. Results demonstrate the advantages of using olivine in the presence of NaOH and the associated increases in soil shear strength of up to 40% over 90 days. Samples subjected to carbonation for a further 7 days led to additional increases in soil strength of up to 60%. Microstructural investigations before and after carbonation attributed the strength development to the formation of $\mathrm{Mg}(\mathrm{OH}{)}_2$, hydrated magnesium carbonates, and M─S─H, A─S─H gel phases. The impact of this work is far reaching and provides a new soil stabilization approach. Key advantages include significant improvements in soil strength with a lower carbon footprint compared with lime or cement stabilization.

Tire particles in the form of shreds, chips, or crumbs, are normally mixed with sand to make suitable alternative backfill or embankment materials. This mixture of soft (tire) and rigid (sand) particles in their optimum ratio has been shown to provide reasonable engineering performance in terms of strength, permeability, durability, and compressibility. In this study, mixtures of fine recycled glass (FRG) and tire crumbs (TC) were evaluated through isotropic compression tests, as well as consolidated drained triaxial tests under five confinement levels. Four proportions of mixtures with gravimetric TC contents of 10–40% were evaluated in terms of shear and compression response. Results show that, increasing the TC content decreases the shear strength parameters and Young’s modulus, and increases the compressibility of the mixture. Gravimetric TC content corresponding to the transition mixture in high and low confinements were between 10 and 20%, and 20 to 30%, respectively. In mixtures with a TC content less or greater than that of a transition mixture, a FRG or TC skeleton was found to govern the behavior of the mixture. The outcomes of this research study were compared with results of investigations carried out on sand-rubber mixtures, and possible applications of this fully recycled product are discussed.

Based on a large database of unconfined compressive strength ($q_u$) and splitting tensile strength ($q_t$) results of cement-bonded clean granular soils with varying characteristics, distinct porosities, cement types and contents, and curing time periods, this paper advances the understanding of key strength controlling parameters. The $q_u$ and $q_t$ values were normalized, and a broad-spectrum empirical relationship (a general model) for cement-bonded clean granular soils controlling both tensile and compressive strength for an entire range of porosities and cement contents was proposed and successfully checked against literature data, contributing to the establishment of the blends’ strength behavior. From a practical perspective, it means that, at limit, carrying out one unconfined compression/splitting tensile test for one specimen (molded with a specific cement amount, at a specific porosity, and cured for a given time period) allows the determination of the curve that controls the strength for an entire range of porosities and cement contents. This also contributes to minimizing the number of specimens that need to be molded and tested, thus also reducing project development cost and time.

In modern waste-management systems, an advantage is given to waste recycling and reuse, rather than to disposal. In the perspective of various initiatives taken worldwide in an attempt to convert waste materials into new products, the objective of this paper is to quantify contribution of unsorted recycled steel fibers from waste tires (RTSF) for use in the concrete industry. An environmentally and financially sustainable hybrid fiber–reinforced concrete (SHFRC), obtained by combining traditional components [manufactured steel fibers (M)] and unsorted RTSF is developed. This paper for the first time, demonstrates that by determining the optimal amount and ratio of fibers (M and RTSF), sustainable hybrid fiber–reinforced concrete (SHFRC) with equal or better properties compared to ordinary fiber-reinforced concrete with only M fibers can be prepared. At the same time, it is also shown that in the optimum quantity and correct ratio, synergy between RTSF and M fibers can be used even for preparation of SHFRC with deflection-hardening behavior. A crack width–deflection model for SHFRC with unsorted RTSF under four-point loading is proposed.

Sandstone is a popular type of natural stone and is made up of collective grains of quartz. India is one of the countries blessed with various types of sandstones with appealing colors. Demand for Indian sandstones has increased in the international market and they are being exported to many countries like United States, United Kingdom, and New Zealand. Since Indian sandstones possess impressive qualities to durability, strength, and resistance to abrasion, they are being used in roofing, paving, flooring, aesthetic pillars, and stone carving. Quartz sandstone is a type where the elemental framework of sandstone is dominated by quartz and may contain a small amount of clay in the form of muscovite. Since the clay content in a quartz sandstone is much lower, they can be used as an effective replacement for conventional coarse aggregates in the production of cement concrete. In this paper, quartz sandstones coarse aggregates have been utilized as a substitute of conventional coarse aggregates and its response to sulfuric acid has been studied. It can be concluded that concrete with quartz sandstone aggregates up to 40% replacement showed better resistance to sulfuric acid exposure.