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Corrosion is one of the most severe threats to the stability of steel bridges and regular rust removal techniques is needed for the maintenance of steel bridges. Currently the correlation between rust development/removal process and the structural/environmental performance of the steel bridges has not been fully understood. This study intends to fill this knowledge gap through critically reviewing. The characteristic analysis of the rust on the corroded steel bridges was first introduced, which provided information that was needed to understand the corrosion mechanisms and classify the rust type. Then the related rust removal techniques (chemical and physical methods) are analyzed by considering the environmental impact and cleaning efficiency. Based on the discussion, the laser cleaning method is proposed due to its cleaning efficiency and environmentally friendliness. After that, the influence of developed rust (uniform and pitting) on the structural performance (static and dynamic) of steel members were summarized. Through the discussion, the potential environmental impact of the corroded steel bridges was identified, including runoff of heavy metal and bacteria growth caused by iron rust. Besides that, an improved kinetic model was proposed by considering the influence of rust removal on the corrosion rate. Furthermore, the structural impact of laser cleaning was simulated with the finite element analysis. This study will serve as solid base for the future studies of corrosion development and rust removal on steel bridges, and the proposed technical routes can be proceeded during future studies to better understand the environmental and structural performance of the steel bridges. [ABSTRACT FROM AUTHOR]

The effects of calcium on the atomic structure of alkali‐activated binder materials were investigated. The alkali‐activated binder samples with varied Ca/Si ratios were first statically examined with both the X‐ray diffraction (XRD) and total scattering function analysis. The added calcium can reorder the atomic structure of the alkali‐activated materials and enhance its crystallization based on the X‐ray pair distribution function (PDF) and XRD analysis. In situ PDF experiments were undertaken to examine the evolution of the atomic structure of calcium‐contained geopolymer. The increase in calcium content accelerated the dissolution of precursor and the formation of the binder. It was shown that the additional Ca(OH)2 could serve as nucleation sites for the precipitation of sodium aluminosilicate hydrate gel to accelerate the reaction. PDF analysis and XRD characterization enable the examination of the phase development of alkali‐activated materials at the atomic scale. [ABSTRACT FROM AUTHOR]

This study investigated the transport properties of cement mortar using microscale X-ray computed tomography (μCT) characterization techniques, the Permeability Solver computational program, and laboratory experiments. Lightweight aggregates (LWAs) were used as the internal curing agent in this study. Mortar samples with and without internal curing were prepared with a water-cement ratio of 0.45. The μCT techniques were applied to obtain digital data of the microstructure of the mortar samples at the resolution of 1 μm. The acquired images were processed to identify the pore structure. Three-dimensional (3D) digital pore structure samples were reconstructed, and the data were read by the Permeability Solver to analyze the porosity, pore conductivity, and permeability of the mortar mixtures. Pore connectivity was evaluated by the burning algorithm. Water transport was simulated by the finite-difference method combined with the compressibility relaxation algorithm. Darcy's Law was then applied to calculate the permeability of the mixture. The transport properties of mortar with and without internal curing were simulated at 60 and 84 h. The results showed that the internally cured samples had lower permeability than the samples without internal curing. The permeability of the samples with internal curing decreased from 60 to 84 h. The results indicated that autogenous shrinkage cracks could be mitigated using internal curing. [ABSTRACT FROM AUTHOR]

In this study, nano- SiO2 was synthesized using the sol-gel method to modify the properties of fly ash-slag geopolymers (FASGs). FASGs with six contents of sol-type nano- SiO2 (0, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%) and two alkali dosages (5% and 7% of Na2O) were prepared. The influences of sol-type nano- SiO2 and alkali content on the compressive strength, flexural strength, drying shrinkage, and microstructure of FASG were studied. The results demonstrated that the early-age compressive and flexure strength of FASG can be enhanced by sol-type nano- SiO2 due to the improved microstructure and the reaction products. The improvement effect of sol-type nano- SiO2 on mechanical properties was more significant for FASGs with lower alkali dosages. The optimized content of sol-type nano- SiO2 in FASG was 0.2% for the mechanical properties. The addition of the sol-type nano- SiO2 can mitigate the drying shrinkage of the FASG when the content is lower than 0.4%. The sol-type nano- SiO2 can promote the formation of reaction products in FASG and result in a denser microstructure of FASG. [ABSTRACT FROM AUTHOR]

This study investigated the performance of early-aged and hardened self-consolidating concrete (SCC). Rubber-modified SCC mixtures were prepared with 15% as-received crumb rubber and 15% and 25% NaOH-treated crumb rubber based on volume of fine aggregates. The SCC sampled without rubber aggregates were cast as the control groups. The slump test, V-flannel flow test, and U-box test were conducted to evaluate the fresh properties of different types of rubber modified SCC. The fresh properties showed slightly reduced flowability with replaced rubber particles. The measured compressive and splitting tensile strength of rubber-modified SCC concrete were reduced in comparison with the control mixture. However, the surface-treated rubberized concrete had higher mechanical strength than as-received rubberized concrete due to better bonding at the interface. The measured ultrasonic transmission speed decreased with the increasing rubber content in concrete and these results also indicated the reduced dynamic modulus. The transport property evaluated from the electrical resistivity measurement indicated the decreased permeability with added rubber content. The durability performances (including alkali-silica reaction and drying shrinkage) of SCC mortar samples were generally improved with rubber-modified samples. Overall study showed that the rubber-modified SCC can maintain good workability and mechanical properties and enhance durability with reduced environmental impacts. [ABSTRACT FROM AUTHOR]

This study experimentally investigated the durability of rubberized mortar and concrete samples with NaOH-solution treated rubber particles. The concrete samples without rubber particles were cast as control samples. The rubberized mortar or concrete samples were prepared with 15% as-received rubber and different contents of NaOH treated rubber (15%, 25%, 35% and 50% by volume of fine aggregate). The electrical resistivity, air-void measurement, and absorption tests were first conducted to evaluate the transport properties of rubberized concrete samples. The freeze-thaw durability tests on different concrete samples showed that the added rubber particles improved the freeze-thaw resistance of concrete. The effect was more significant for NaOH treated rubber particles than that of as-received rubber particles. The results of the alkali-silicate reaction (ASR) expansion test suggested that the ASR expansion was decreased in rubberized mortar compared to plain mortar. The 15% NaOH treated rubber replacement was most effective on reducing the ASR expansion among all of the rubberized mortar samples. The drying shrinkage increased with the content of rubber particles in mortar; however, the increased shrinkage in rubberized mortar appeared to be reduced when the additional rubber was treated with NaOH solution. These test results indicated that the rubberized concrete or mortar (with 15% or 25% NaOH-treated rubber replacement) samples have improved durability. [ABSTRACT FROM AUTHOR]

• The flowability of the geopolymer increases with the glass replacement level. • The added glass powder prolongs the setting time of the geopolymer binder. • The glass powder replacement facilitates the formation of a denser microstructure. • Mechanical properties are improved with appropriate glass powder replacement level. This objective of this study is to utilize recycled glass powder as a partial replacement precursor of the metakaolin-based geopolymer to develop a sustainable geopolymer material. Four glass powder replacement ratios were selected for the metakaolin-based geopolymer preparation (0%, 5%, 10%, and 20% by the total precursor weight). The pair distribution function (PDF) analysis indicated that a higher amount of the four-membered ring structures in the formed gel with the added glass powder. Both PDF and EDX analysis showed that the Si/Al ratio of the binder phase increased with glass powder content in the mixtures. The added glass powder can improve the workability of the geopolymer binder and prolong the setting time of the synthesized geopolymer samples. The nanoindentation test results showed that the elastic modulus of the formed gel increased with replaced 10% and 20% glass powder. In addition, the samples with 5% of glass powder achieved the highest compressive strength among tested samples. The test results indicated that the appropriate glass powder replacement can affect the geopolymerization process and modify the formed gels in the metakaolin-based geopolymer to improve the mechanical properties of the mixture. The information obtained in this study can promote the utilization of waste glass powder as a partial replacement of the precursor for the production of sustainable alkali-activated materials. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical properties, nanopore structure and drying shrinkage behavior of the metakaolin-based geopolymer mixtures containing 0%–20% waste glass powder. The prepared samples were cured under ambient temperature and high temperature (60 °C), respectively. The mechanical properties of the samples can be improved by introducing the low content of glass powder (5%–10%). Microstructure and nanopore structure analysis indicated that a denser gel phase was formed in the glass powder modified geopolymer samples. The added glass powder reduced the water loss rate of the samples under drying condition, leading to a reduction of drying shrinkage at early ages. The capillary stress in the prepared geopolymer samples was analyzed based on the pore size distribution of the mixtures. The magnitude of capillary stress generated in glass powder containing samples was similar to that of geopolymers without glass powder. The improved creep modulus with added glass powder facilitated the reduction of the shrinkage of the samples at later ages. This study can facilitate the recycling of waste glass into geopolymer for sustainable construction applications. [ABSTRACT FROM AUTHOR]

Concrete is known as the most globally used construction material, but it releases a huge amount of greenhouse gases due to cement production. Recently, Supplementary Cementitious Materials (SCMs) such as fly ash and Ground Granulated Blast Furnace Slag (GGBFS) have been widely used in concrete to reduce the cement content. However, SCMs can alter the mechanical properties and time-dependent behaviors of concrete and the early age mechanical properties of concrete significantly affect the concrete cracking in the engineering field. Therefore, evaluation of the development of the mechanical properties of SCMs-based concrete is vital. In this paper, the time development of mechanical properties of concrete mixes with various fly ash and GGBFS was experimentally investigated. Four different cement replacement levels including 0%, 20%, 30%, and 40% by fly ash and GGBFS as well as ternary binders were considered. Compressive strength, splitting tensile strength, flexural strength, and elastic modulus of concrete were measured until 28 days. Three additional concrete mixes with ternary binders were also cast to investigate the early-age autogenous shrinkage development until 28 days. In addition, prediction models in existing standards were used and compared to experimental results. The comparison results showed that the prediction models overestimated the compressive strength but underestimated the splitting tensile strength development and autogenous shrinkage. As a result, a model capturing the effect of fly ash and GGBFS on the development of compressive and splitting tensile strength is proposed to improve the prediction accuracy for current standards and empirical models. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and numerical studies of flexural-fracture behaviors of steel fiber–reinforced rubber self-compacting concrete (SRSCC) materials. The scrap-tires rubber aggregate was used to partially (10%, 15%, and 25%) replace the fine aggregate based on its volume for SRSCC samples, and the microsteel fiber was introduced with an addition ratio of 0.2% based on the entire mixture volume. The plain self-compacting concrete (SCC) and the rubberized SCC specimens were produced for comparison. The three-point bending test on the single-edge notched beam showed the increased flexural strength and total fracture energy of SRSCC samples by adding steel fiber and rubber. The critical fracture parameters including initial fracture energy (Gf) and fracture toughness (KІc) were determined based on the Load-CMOD curves and two parameters fracture model. With these properties, the bilinear tension-softening model (aggregate interlock effect) and trilinear tension-softening model (aggregate interlock and fiber-bridging effects) were calibrated for normal SCC and SRSCC, respectively. The tension-softening functions were utilized in the FEM model to predict the flexural-fracture behaviors of corresponding specimens, and the numerical simulation results showed reasonable agreement with experiments. Overall, the experimental testing data and numerical simulation model can reveal the detailed fracture behavior of SRSCC for future improved material design. [ABSTRACT FROM AUTHOR]

Supplementary cementitious materials (SCMs) are eco-friendly cementitious materials that can partially replace ordinary Portland cement (OPC). The occurrence of early-age cracking in OPC-SCM blended cement is a significant factor impacting the mechanical properties and durability of the concrete. This article presents a comprehensive review of the existing research on cracking in OPC-SCM concrete mix at early ages. To assess the effects of SCMs on the early-age cracking of concrete, the properties of blended cement-based concrete, in terms of its viscoelastic behavior, evolution of mechanical performance, and factors that affect the risk of cracking in concrete at early ages, are reviewed. The use of SCMs in OPC-SCM concrete mix can be an effective method for mitigating early-age cracking while improving the properties and durability of concrete structures. Previous research showed that the shrinkage and creep of OPC-SCM concrete mix are lower than those of conventional concrete. Moreover, the lower cement content of OPC-SCM concrete mix resulted in a better resistance to thermal cracking. Proper selection, proportioning, and implementation of SCMs in concrete can help to optimize the performance and reduce the environmental impact of OPC-SCM concrete mix. [ABSTRACT FROM AUTHOR]

In this study, the synergistic effect of combining macro polypropylene (PP) fiber and rubberized concrete was evaluated based on mechanical and durability performance, as well as microstructure. The specimens were prepared with two different rubber volume contents at 10% and 15%, incorporating with a consistent fiber volume fraction of 0.5%. The plain concrete specimens and specimens with only PP fiber were also produced for comparison. The mechanical test results indicated that the fracture energy of plain concrete could be enhanced with both macro PP fiber and rubber aggregates. Besides, all specimens achieved compressive strength higher than 40 Mpa, and the ultrasonic pulse velocity demonstrated the good quality of concrete specimens. The fracture morphology and ESEM imaging showed the positive function of rubber aggregates and PP fibers on the post-crack propagation. The durability performance, including drying shrinkage, ASR expansion, and frost resistance were also strengthened in macro PP fiber-reinforced rubber concrete compared with plain concrete. The macro PP fiber-reinforced rubber concrete will enlarge the post-failure flexural residual load capacity and deformation and distribute stress for multiple crack propagation, thus increasing overall fracture toughness and reducing brittleness. The sustainable applications can be further explored with the combination of macro PP fiber and recycled rubber aggregate. [ABSTRACT FROM AUTHOR]

Abstract This study aims to investigate the influence of lithium and calcium content on the alkali-silica reaction kinetics and phase formation processes at atomic scales. The atomic structure of the reacted ASR gels was analyzed with the Pair Distribution Function (PDF) measurement. The analysis results can explain the expansion potential difference of gels with different chemical composition. The in situ PDF characterizations of the samples containing lithium compounds identified the formation of the Li Si phase, and thus both the alkali-silica reaction and the reaction between dissolved silica and Ca(OH) 2 were suppressed. The alkali-silica reaction kinetics was further indicated with the changes of Si O peak intensity. The amorphous structure of the generated Li Si phase was confirmed with in situ XRD tests. The results strongly support the formed amorphous Li Si phase can act as a surface barrier for silica dissolution, and thus prohibit both the alkali-silica reaction and pozzolanic reaction in hardened concrete. [ABSTRACT FROM AUTHOR]

Highlights • The PVA-fiber was innovatively introduced to the rubberized concrete. • Fracture energy and post-failure performance were largely increased by PVA-fiber reinforcement. • Durability including freeze-thaw, ASR and drying shrinkage of fiber rubberized concrete were improved from control one. • Rubberized concrete could be largely applied by adding PVA-fiber as reinforcement. Abstract In this study, the Polyvinyl Alcohol (PVA) fiber was introduced to improve the performance of the rubberized concrete. This study experimentally investigated the mechanical performance and durability of Polyvinyl Alcohol (PVA) fiber-reinforced rubber concrete. The waste rubber particles (mesh size #10–#30) were selected to partially replace fine aggregates in the plain concrete. In addition, the rubber particles were pre-treated with an alkali solution to enhance the interface bond with cement paste. The fiber-reinforced rubber concrete samples were prepared with different fine aggregate replacement ratios based on the volume of fine aggregate (15%, 20%, and 25%) and a selected fiber content (0.5% based on the total volume of the mixture). For those samples, the mechanical properties, including compressive strength, flexural behavior, and fracture energy were evaluated to compare with control samples. The results showed that fiber-reinforced samples can largely improve the post-cracking extension and fracture energy. The results of electrical resistivity test indicated the reduced permeability in the fiber-reinforced rubber concrete. The durability performance including Alkali-Silica reaction (ASR) expansion, drying shrinkage and freeze-thaw resistance were also investigated and compared with the control samples. All the durability performances were enhanced through rubber stress release and fiber crack bridging. Therefore, the PVA-fiber reinforced rubber concrete can improve durability and ductility of cementitious materials for structure construction and also can facilitate the recycling of waste rubber into cementitious materials. [ABSTRACT FROM AUTHOR]

• Geopolymers are prepared by thermal-mechanical activated aluminum sulfate residue. • The effects of design factors on the performance of TMASR geopolymer are evaluated. • The main products of efflorescence in TMASR geopolymer are sodium sulfate crystals. In this study, geopolymer prepared from thermal-mechanical activated aluminum sulfate residue (TMASR) and alkali activator was studied. This work aims to investigate the effects of different design factors on the workability, compressive strength, and efflorescence of TMASR-based geopolymer. The reaction products and structures of the geopolymer binders made from TMASR were tested by FTIR, XRD, and SEM. The results showed that the type, dosage, silicate modulus of the activator, and the water to binder ratio can significantly affect the fresh and hardened properties of TMASR-based geopolymer. A mixture with optimal compressive strength, workability, and efflorescence characteristics can be obtained by using Na 2 SiO 3 solid content of 30%, the water to binder ratios of 0.6–0.65, and the modules of sodium silicate of 1.2–1.6. The main hydration products of TMASR-based geopolymer were amorphous geopolymeric materials. The efflorescence product compositions in TMASR-based geopolymer were Na 2 SO 4 , Na 2 SO 4 ·10H 2 O, Na 2 CO 3 , and Na 2 CO 3 ·nH 2 O. The results obtained in this study can promote the utilization of waste acidic aluminum sulfate residue for the production of sustainable construction materials. [ABSTRACT FROM AUTHOR]

Using rubber particles as concrete aggregates can reduce the environmental impacts caused by the large accumulation of scrap tires. However, the added rubber particles can decrease concrete strength due to their low stiffness and surface bonding with cement paste. This study aims to improve the rubber concrete performance by employing different surface treatment and coating methods. Particularly, two surface treatment methods (NaOH, and Silane Coupling Agent) and three coating techniques (coated with normal cement, blended cement with silica fume, and blended cement plus sodium silicate) were used to improve rubber-cement bonding. Totally, ten groups of rubber concrete samples were prepared by using difference treatment or rubber replacement ratio. In addition, the control concrete samples without rubber particles or with as-received rubber particles were prepared for the comparison. The compressive strength tests demonstrated the NaOH-solution treatment can significantly improve the rubber concrete strength by comparing with normal and as-received rubber concrete. Further tests indicated that the samples with 25% replacement can still fulfil the strength requirements for rigid pavement construction. The measured electrical resistivity of rubber concrete were higher than the normal concrete, which indicates lower permeability and better durability. The decreased thermal conductivity and sound transmission attenuation can increase building energy efficiency and reduce noise, respectively. Overall, this study demonstrated NaOH-treated methods can improve the mechanical performance of rubber concrete and enhance its long-term durability. This modified rubber concrete can be potentially applied to the pavement and structure construction applications. [ABSTRACT FROM AUTHOR]

Value-added utilization of waste tires in cementitious materials has been studied for decades, whereas the synergy between rubber and alkali-activated cements deserves more investigations. To this end, we compared physico-mechanical and durability properties of alkali-activated slag (AAS) and OPC-based composites containing NaOH-pretreated/as-received crumb rubber (CR). It was found that the incorporation of CR had both positive and negative effects on specimens due to its special attributes. CR reduced electrical conductivity which was associated with the ion transport ability, since it worked as an electrical insulator and increased hydrophobicity of pore walls. The sulfate expansion decreased with CR content because the flow of sulfate ions was demobilized, and the flexibility of CR relieved the internal stress. CR also improved the freeze-thaw durability of composites if the total CR content was less than 30% in specimens. However, the low Young's modulus of CR impaired the compressive strength and failed to effectively control the total shrinkage upon drying. The composites with CR must avoid high temperature exposure which resulted in the pyrolysis of rubber. In addition, the NaOH pretreatment enhanced adhesion between CR and hydrated cement and improved overall performances of composites. The FTIR spectra confirmed the NaOH-induced accelerated oxidation of CR surface and the generation of polar functional groups including carbonyl and carboxyl groups, increasing the total surface energy of rubber. More importantly, the alkali-activation process for AAS could treat the CR aggregate in the meantime, which means the use of CR in alkali-activated cements does not require the pretreatment of CR before blending. [Display omitted] • CR worked as an electrical insulator and contributed to the increased hydrophobicity of pore walls. • The total shrinkage of both AAS and OPC composites increased with CR content. • Sulfate expansion decreased with CR content since the sulfate was demobilized and the internal stress was relieved by CR. • The high temperature exposure resulted in the pyrolysis of rubber aggregate, severely impairing the mechanical properties. • NaOH pretreatment oxidized the surface of rubber particles and generated more polar groups. [ABSTRACT FROM AUTHOR]

• Flexural properties of CLT panels made with low-value sugar maple has been studied. • Melamine provided better bonding than Resorcinol but not much on flexural properties. • Stronger outer layers strengthen the overall major direction flexural performance of CLT. • Studied layups provided better bending and shear performance than standard layup E1. • The finite element model provided satisfactory estimation based on lamination data. The objective of this study is to examine the mechanical performance of cross laminated timber (CLT) panels made of low-value sugar maple under out of plane loads through mechanical tests and numerical simulation. The laminations were sorted into High and Low classes based on the measured modulus of elasticity (MOE). Two 3-layer sugar maple CLT layups as High-Low-High and Low-High-Low glued with resorcinol-based adhesive and one CLT layup of High-Low-High glued with melamine-based adhesive were prepared. Block shear, long-span bending (span-to-depth ratio of 33:1) and short-span bending (5.5:1) tests were conducted to evaluate the bonding, flexural and shear behavior of these low-value sugar maple CLTs. With a limited sample size, the lab-manufactured low-value sugar maple CLT provided a 50% to 80% higher MOE and at least two times higher MOR than CLT type E1 from APA/PRG 320. Similar MOE and MOR improvements were found by comparing CLT made with other species from literatures. The finite element simulation of bending tests was conducted with the orthogonal constitutive law and the progressive damage model based on the calibrated material properties parameters from lumber rating and references. The simulation results on each CLT panel type have a reasonable comparison with experimental test data. Therefore, these integrated experiment and simulation methods can provide detailed mechanical behaviors of the low-value sugar maple CLT, which can also be applied to other CLT species and layup. [ABSTRACT FROM AUTHOR]

The self-compacting concrete (SCC) with the replacement of recycled rubber aggregates is limited for the field application due to high-performance requirements. The steel fiber was introduced to the rubberized SCC (RSCC) to enhance its performance and promote its application. The fresh and mechanical properties and durability performance of steel fiber-reinforced rubber self-compacting concrete (SRSCC) were evaluated. The SRSCC samples were prepared with replaced rubber aggregate based on fine aggregate volume percentages of 10%, 15%, and 25% and a consistent steel fiber ratio of 0.2%. The plain SCC and rubberized SCC samples were also produced for comparison. The fresh performance was evaluated with slump flow, J-ring flow, V-funnel, and U-box tests. The results showed that both filling and passing ability could be affected by the added steel fiber and rubber aggregate. However, the SRSCC could still meet most of the recommended criteria for passing and filling abilities when the rubber content is lower than 25%. Regarding the hardened properties, the compressive strength was reduced in rubber SCC samples with increased rubber contents by comparing with the control SCC samples. Nevertheless, SRSCC samples with 10% rubbers have higher splitting tensile strength than RSCC and plain SCC. Also, the SRSCC specimens showed excellent freeze-thaw resistance after 600 F-T cycles. The relative dynamic modulus of elasticity slightly increased without any dimensional expansion in SRSCC samples. In summary, the proposed SRSCC can meet required flowability, filling and passing abilities along with good mechanical and freeze-thaw performance. This study will provide lab test data for the applications of recycling waste tire aggregates in steel fiber-reinforced SCC. • The recycled tire rubber aggregate was used as an alternative for fine aggregates in SRSCC. • The fresh mixtures of SRSCC represent good flowability, filling and passing abilities. • SRSCC showed good mechanical properties for infrastructure field applications. • Excellent freeze-thaw durability of SRSCC were found during 600 F-T cycles. [ABSTRACT FROM AUTHOR]

Using the crushed waste Cathode Ray Tube (CRT) glass as fine aggregate to produce concrete can be an efficient method to resolve the recycling issue. However, the mediocre mechanical properties of CRT concrete obstructed its wide application. This study aims to resolve this issue based on the study on concrete/mortar specimen incorporating with an innovated surface treatment method. Specifically, a two-step surface treatment method was proposed to improve the performance of CRT concrete by modifying the surface layer of CRT glass sands with NaOH solution and Al(NO 3) 3 solution. About 30% of the portland cement was replaced with class-F fly ash to mitigate possible ASR damage by the reactive CRT aggregate. The mechanical performance (Compressive/flexural strength, dynamic modulus of elasticity, and flexural fracture energy) and the durability performance (Drying shrinkage and ASR expansion) was examined and compared among different specimens. In addition, the leaching levels of lead in different concrete specimens was evaluated by toxicity characteristic leaching procedure (TCLP). The results showed that the surface treatment method of CRT glass sands could obviously improve both the mechanical properties and durability performance. Particularly, the leaching of lead (Pb) level in all concrete specimens was much lower than the TCLP heavy metals limit of 5 mg/L. This experimental study will facilitate the production of CRT glass concrete for secondary structural applications. • The newly developed surface treatment method was applied on crushed CRT glass sands. • Treated CRT glass concrete showed better mechanical properties and durability performance. • The ASR expansion of specimens with 25% CRT glass sands was lower than 0.1% limit. • The leaching of lead for CRT glass concrete was lower than the standard limit (0.5 mg/L). [ABSTRACT FROM AUTHOR]

Highlights • Recycled crumb rubber particles were applied into polymer concrete for improved performance. • Both mechanical properties and thermal-related durability performance were increased. • Rubber epoxy concrete can better protect concrete bridge decks with increased ductility. Abstract The epoxy-based polymer concrete has been widely used for concrete repairing and overlays due to good mechanical properties and durability. To reduce environmental landfill problems with the accumulation of tire rubbers, scrap tire rubbers were added to epoxy polymer concrete in this investigation. The crumb rubber (with mesh size #50, 0.279 mm) were introduced into epoxy concrete with two different contents of 5% and 10% based on the epoxy monomer weight. The mechanical properties including direct tensile strength, compressive strength, splitting tensile strength and interface bond strength. Thermal- and moisture-related durability performance of rubberized epoxy concrete were measured and compared with the control samples. The compressive strength and splitting tensile strength were improved with the added 5% solid rubbers, and slightly reduced with 10% content. With a specially-designed testing method, the interface tensile bonding strength between the epoxy concrete overlay and concrete slab were measured as higher than 250 psi for both control and rubberized samples. The thermal conductivity of polymer concrete was reduced with the increase of rubber contents. In addition, very low water absorption rates (<0.5%) were measured with all types of epoxy concrete samples. The interface microstructure with SEM also indicated the good bonds between rubber particles and epoxy resins. The overall test results showed the enhanced performance of rubber-modified epoxy concrete which can facilitate the tire rubber recycling into epoxy polymer concrete for protecting the exist concrete pavement structures. [ABSTRACT FROM AUTHOR]

This work aims to study the alkali‐silica reaction (ASR) with incorporated kinetic‐thermodynamic analysis. The model reactant tests were first conducted to study the silica dissolution in the simulated pore solution under different temperatures. Then, the kinetic model for silica dissolution was further improved by considering the influence of effective surface area. The improved kinetic model was also incorporated into the GEMS thermodynamic simulation. The model analysis demonstrated the silica dissolution rate is decreased mainly caused by reduced hydroxyl activity with increased saturation degree. The dissolved silica first reacted with the portlandite phase and formed the Calcium–Silicate–Hydrate (CSH) gel. The ASR gel can only be generated under high silicate ion concentration after the consumption of portlandite. [ABSTRACT FROM AUTHOR]

Recycling waste glass aggregate into concrete can reduce environmental impacts but also may lead to serious alkali silica reaction (ASR) damage. This study aims to characterize ASR damage development in the mortar samples containing reactive glass aggregates and investigate the damage reduction effect of the waste supplementary cementitious materials (SCMs), including recycled glass powders and fly ash. The recycled glass aggregate mortar samples with/without SCMs were prepared in this study. The length change tests were first conducted with the prepared mortar samples based on the ASTM C1260 standard. The results demonstrated the added SCMs can largely decrease early-age ASR expansion rate. The optical microscope and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) were further conducted to characterize the ASR damage in mortar samples and investigate the damage mitigation mechanism with added SCMs. The combined SEM imaging and chemical analysis indicated added SCMs can decrease both the alkali and calcium content of the generated ASR gel. In addition, the ASR damage development inside mortar samples were monitored with dynamic micron X-ray CT (μCT) over a reaction period of 63 h at the temperature of 80 °C. The scanning patterns demonstrated the ASR damage can be easily developed from the area with initial cracks and sharp corners. The images of glass power and fly ash samples showed significantly reduced ASR damage. This study showed that adding of SCMs can largely reduce ASR deterioration and thus facilitate the recycling glass particles into concrete. [ABSTRACT FROM AUTHOR]

The crack development is considered to be one of the most severe threats to the durability of concrete infrastructure. This study aims to enhance the durability performance of cementitious material with the pH-responsive Superabsorbent Polymer (SAP). The SAP was synthesized with acrylic acid (AA)-methyl acrylate (MA) precursors, and three type samples with different crosslinking levels were prepared. The examination on the pH sensitivity indicated that the swelling capacity of the prepared SAP would first increase and then decrease with solution alkalinity, and the peak swelling potential was achieved around pH value of 12 for all the three type SAP with solution/gel mass ratio of 500. Further examination indicated the alkalinity of the buffer solution was reduced during the adsorption test, which can be caused by the hydrolysis of the amide groups and the crosslinker. Besides that, it was also found the solution/gel ratio and the Ca(OH) 2 content could affect the swelling potential of the SAP. After that, the performance tests were conducted for the evaluation of concrete with SAP. A wax-coating protocol for the SAP was designed by using the hot-water method to prevent its swelling during mixing process. It was found that the strength reduction for samples with wax-coated SAP was insignificant compared to that of the control samples. Furthermore, durability tests supported the wax-shell could be broken by the crack propagation in concrete. And further experimental studies are needed to optimize the wax-size and shell thickness for enhanced self-sealing efficiency. [ABSTRACT FROM AUTHOR]