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Wood wool cement board is made of Portland cement as a cross-linking agent, wood fiber as a fiber reinforcement material, and some additives. The precast WWCB-filled concrete floor slabs are a new type of hollow slab. This structure formed by pouring the bottom layer of concrete, laying the WWCB, then pouring the top layer of concrete, and finally curing. And this type of floor slabs is composed of double-layer reinforcement mesh, including top and bottom reinforcement which connected by triangular contact bars. In order to study the mechanical properties of the precast WWCB-filled concrete slabs themselves, this paper conducted four-point bending loading tests on 9 precast WWCB-filled concrete slabs of different sizes to analyze the effect of penetration type and cavity size on the flexural performance of the slabs. The results of the experimental study show that: the ultimate load-bearing capacity of precast WWCB-filled concrete slabs is higher than 100-mm-thick solid slabs, and their deflection of them is similar to that of ordinary solid slabs, with good plasticity and flexibility; the overall flexural resistance of the precast WWCB-filled concrete slabs is good, the crack distribution is uniform, and the damage pattern is better than that of cast-in-situ slabs.

Steel slag, as an industrial byproduct obtained from the steel manufacturing industry, may cause land occupation, resource waste, and environmental pollution. The application of steel slag as a material for soil reinforcement in road engineering is very popular due to its potential hydration activity. The unconfined compression strength, microstructure, and transport properties of loess soil with cement, lime and steel slag were investigated. The results show that the loess soil can be reinforced by cement, lime, and steel slag to varying degrees. The reinforcement mechanism of cement for loess soil is realized by pore filling by cement hydration products such as CH, C-S-H and AFt, and their unconfined compression strength is improved by reducing the porosity. The reinforcement mechanism of lime for loess soil is achieved by pore filling by hydration products such as CH and CaCO3, and their strength is improved by a refined pore structure where the porosity has not been significantly reduced. The reinforcement mechanism of steel slag for loess soil is a combined mechanism of cement and lime, including pore filling and refined pores. The pore structure of reinforced soil can be studied at different scales by the MIP, LF NMR, and X-CT test methods. The transport properties including diffusivity and permeability of reinforcing soil can be well explored by Avizo software based on the microstructure obtained from X-CT.

The pavement industry has been increasingly encouraged to adopt a more circular approach, associating economic development with a more responsible use of natural resources, due to the significant impacts that its activities impose, particularly on the environment and financial resources. One practice aligned with the circular economy trend is the use of Reclaimed Asphalt Pavement (RAP) in asphalt mixtures. Several methods have been adopted to increase the amount of RAP without compromising the mechanical performance of recycled asphalt mixtures, with particular emphasis on warm mix additives and animal and vegetable oils. In this study, the incorporation of zeolite and cottonseed oil in different proportions in these mixtures was evaluated. Blending charts were used to establish the maximum recycling rates based on the critical temperatures of bio-binders formulated with cottonseed oil. For this research, two sets of recycled asphalt mixtures were analyzed: one with 15 %, 25 %, and 33 % RAP, containing 4 %, 6 %, and 10 % cottonseed oil, respectively, and another with 15 %, 25 %, and 33 % RAP, containing 0.3 % zeolite. The mixtures were evaluated for both mechanical performance and circularity aspects through an integrated analysis of mechanical properties (tensile strength, resilient modulus, moisture damage, Cantabro abrasion, flow number, fatigue life) and the Mixture Circularity Index (MCIRAM). All recycled mixtures, regardless of the type of additive, demonstrated satisfactory mechanical performance in all tests conducted. The integrated analysis of mechanical and circularity dimensions identified that the recycled asphalt mixture containing 0.3 % zeolite and 25 % RAP is the most advantageous, as it met the mechanical criteria and exhibited good environmental performance. Among the mixtures with bio-binder, the combination containing 33 % RAP and 10 % cottonseed oil exhibited superior mechanical performance and demonstrated greater circularity.

In the town of Fereshteh, Tabriz, Iran, there is a growing concern regarding the tilting of recently constructed buildings. This uneven settlement issue can be primarily attributed to variations in loose fill material thickness, elevated groundwater levels, and the presence of loose sandy layers intermixed with clayey layers. The challenges posed by these tilted structures are further compounded when dealing with historically significant buildings, making demolition an undesirable and wasteful solution. Therefore, alternative restoration methods must be explored. This study focuses on the application of the jacking technique to rectify the tilt observed in reinforced concrete buildings ranging from four to eight stories in height. To simulate the rectification process, numerical modeling using the finite element method was employed. The strategic placement of jacks was critical, as they applied force until the foundation achieved equal vertical displacement on both sides or until the uneven settlement was reduced to an acceptable level. Ensuring the structural integrity of the building during this rectification process was of paramount importance to prevent cracking or collapse due to the forces exerted by the jacks. Elements on the first floor experienced significantly higher internal forces compared to their counterparts on upper floors. Stress concentration was notably observed at the intersection point of the columns and the foundation surface. This highlights the critical importance of positioning the jacks directly beneath the axis of the columns or bearing elements to ensure effective rectification. Based on the results obtained for the studied structures, it becomes evident that employing the jacking method becomes unfeasible when a section of the raft experiences a settlement exceeding 10 cm. This is due to the drastic change in stress distribution conditions within the structural components under such circumstances. However, the jacking method remains a viable and effective solution for settlements below this threshold, rectifying uneven structural settlements without causing harm to the structural elements.

The prevailing practices of geopolymer concrete (GC) preparation use a high concentration of alkali activators, which is uneconomical. It is imperative to develop GC of low-concentration activators with enhanced durability for field implementation. Mechanochemical activation of geopolymer increases the reactivity of its raw materials by converting the crystalline phase to an amorphous phase. It has been illustrated in the present study that mechanochemical activation aids in achieving GC of desired properties at low concentrations of alkali activators. The mechanochemical activation of ground granulated blast furnace slag (GGBS) with sodium metasilicate was carried out to prepare GC of low (2 M) and high (12 M) alkali concentrations. The Portland slag cement-based concrete (PC) was cast to compare the durability performance of GC. The durability of the three concrete mixes was examined in terms of water absorption, the volume of permeable voids (VPV), water and chloride permeability, homogeneity, and acid resistance. The microstructural characterization of concrete samples exposed to acid were carried out by X-ray diffraction, field emission scanning electron microscope, and energy dispersive X-ray spectrometer. The results indicated that GC with a low concentration of activator exhibited lesser water absorption, VPV, and permeability, whereas it offered higher resistance to acids and chloride ion penetrability. Low-concentration GC had a dense and compact structure due to the coexistence of geopolymeric and hydration products, leading to better performance than high-concentration GC and PC. The evaluation of cost and carbon emission of PC, and GC mixes suggests GC as a sustainable alternative to traditional concrete. Although PC is economically viable, the study suggest use of GC with low alkali concentration due to its environmental benefits with a minor increase in cost.

The strength of lime-cemented soils has received significant attention in previous studies. However, limited research has focused on studying soil mixtures for extended durations beyond 365 days, which is essential for understanding shear strength, microstructure, unconfined compressive, and matric suction. Consequently, there is a need to explore the long-term behavior and unsaturated properties of soil specimens cured for up to 500 days using appropriately hydrated lime, considering the semi-empirical porosity/lime index. By investigating various curing times ranging from 15 to 500 days, as well as employing different compaction energies (standard, intermediate, and modified) and lime content ranging from 3% to 9% by weight, this study aims to characterize the evolution of resistance and unsaturated properties of lime-cemented soils. The semi-empirical porosity/lime index is employed to guide the characterization and analysis of the mixtures' resistance properties. By developing equations to estimate the resistance of these mixtures, the study contributes to reducing lime consumption (and reducing CO2 emissions during its production) and optimizing curing time, leading to environmentally friendly geotechnical projects. Due to the utilization of the porosity/lime ratio, lime consumption can be minimized, and curing time can be fixed, resulting in a significant reduction in energy requirements, which is beneficial for the environment. The outcomes of this research have profound implications for the design and construction of sustainable structures such as dams, pavements, and slope protection systems, ensuring their long-term stability, resilience, and ecological balance.

Recycled aggregate (RA) and recycled concrete powder (RCP) hold significant potential as environmentally sustainable raw materials for asphalt mixtures. In this study, a comprehensive investigation was conducted on the bonding properties between RA and RCP-filled asphalt mastic (RCPAM). This investigation utilized an image processing-assisted modified water boiling test, binder bond strength (BBS) tests, and the surface free energy (SFE) method. The results indicate that the boiling water test method, even with the assistance of 2D image processing analysis, cannot adequately evaluate the adhesive characteristics of the RA-RCPAM interface. This limitation could be attributed to the relatively small number of samples tested and the significant variation in surface properties of RA. Increasing both the filler-to-asphalt (F/A) ratio and RCP replacement ratio adversely affected the interfacial bond strength of the RA-RCPAM interface. On the other hand, an increase in RA surface roughness contributed to a higher bond strength. Based on the experimental results, a best-fit multivariate mixed model was proposed to predict the interfacial bond strength between RCP-filled asphalt mastic and recycled aggregate within a given range of RCP replacement ratio, surface roughness, and filler-to-asphalt (F/A) ratios. The analysis of SFE suggested that moisture damage to RCPAM was caused by both cohesive and adhesive failure. Additionally, the minimal impact of adhesion work in wet condition with increasing RCP content suggested that adhesion failure energy was only marginally affected by the inclusion of RCP, even in the presence of moisture. These findings are expected to enhance the understanding of interfacial adhesion characteristics and moisture susceptibility of the RA-RCPAM interface.

Engineered cementitious composites (ECC), which are a kind of novel composite building material with high ductility and high toughness, can be utilized in areas susceptible to salt-freezing damage, such as that caused by snowmelt agents, seawater, and saline soils. In this paper, engineered cementitious composites reinforced with polyethylene fibers (PE) are analyzed to study the changes in the flexural static load properties, and flexural fatigue life of PE-ECC specimens after four different freeze-thaw cycles (0, 50, 100 and 150) in fresh water and a 3.5 % mass fraction NaCl solution. The results show that upon reaching 150 freeze-thaw cycles, there was a notable disparity in the relative equivalent flexural strength between specimens subjected to chloride salt freeze-thaw and freshwater freeze-thaw environments, with the former exhibiting a 1.07-fold increase in damage compared to the latter specimens. Using the relative dynamic elastic modulus as the damage variable, a relationship model was made between the relative equivalent flexural strength and the freeze-thaw damage degree of PE-ECC in two freeze-thaw environments. The flexural fatigue life of PE-ECC after freeze-thaw obeyed a two-parameter Weibull distribution, and the P-S-N curves at various reliability probabilities correlated well with the test results. The safety coefficient of PE-ECC varied with changes in freeze-thaw conditions, necessitating an increase in the safety coefficient to assure structural safety in locations with more severe freeze-thaw damage. The results of this study can serve as a reference for the development of freeze-thaw-resistant designs for PE-ECC structures in future applications.

This study presents the shaking table test results of two-dimensional reinforced concrete (RC) frames retrofitted with a simplified friction damped brace. An easy-to-manufacture and install friction damper with economical design, was proposed and tested under reversed cyclic loading and used to retrofit RC frames. The splice of a conventional steel brace was converted into a friction damper, which not only dissipated seismic energy but also helped avoid the buckling of the steel brace. The test scheme consisted of four RC frames, and the behaviors of the three retrofitted frames were compared with that of a non-retrofitted (bare) frame. The shaking table tests were conducted using an artificial seismic wave that reflected the short-period response characteristics of the Korean earthquake. The test results of the bare and retrofitted frames were analyzed by considering several important performance indicators, such as the cracking and fracture mechanism in the RC frames, base share, and story drift ratios. The results of the shaking table tests demonstrated that the proposed damped brace effectively reduced earthquake-induced drift demands and successfully shifted the fracture and damage concentration from the columns to the beams.

This study assessed concrete durability in pig farm environments, focusing on resistance to organic acid corrosion and physical abrasion. It used supplementary cementitious materials like silica fume (SF), coal fly ash (CFA), and bagasse fly ash (BFA) to improve concrete resilience. The research involved casting and testing concrete samples for compressive strength, acid corrosion resistance, abrasion resistance, and their combined effects. A custom apparatus simulated corrosion and abrasion cycles typical in pig farm flooring. Results showed that a combination of SF, CFA, and BFA significantly enhanced compressive strength, especially with extended curing. Additionally, these materials improved concrete's resistance to acid corrosion, physical abrasion, and their combined effects. The replacement of 30 wt% of cement with CFA and BFA in concrete significantly reduced mass loss due to acid corrosion to less than 10%, whereas the control mix exhibited a mass loss exceeding 24%. Additionally, concrete with 30 wt% CFA or BFA replacement exhibited a minimal combined mass loss, decreasing to less than 2.5% due to acid corrosion and physical abrasion, as opposed to the 16% observed in the control mixture.

Melamine-coated medium density fibreboard (MDF-LAM) is widely used in the construction industry, furniture industry and other structural applications due to its easy processing, low cost, high strength and high dimensional stability. In this study, the effects of MDF on the environment throughout its life cycle were determined by the Life Cycle Assessment (LCA) method. For this purpose, it presents the results of a research conducted to evaluate the environmental impacts and identify hot spots of MDF-LAM production in Türkiye using the LCA method, considering a cradle-to-gate system. The MDF-LAM production process is studied in four subsystems: fibre preparation, board forming, finishing and lamination (LAM). In the analysis of the environmental effects of MDF-LAM, detailed data were obtained from a company producing in Türkiye. In this study, the functional unit is “1 m3 MDF-LAM production in Türkiye”. The environmental impacts of MDF-LAM were estimated in SimaPro 9.1 software using the Ecoinvent database v3.5 with CML-IA impact assessment and Cumulative Energy Demand (CED) methods. Various impact categories were considered in the analysis, such as global warming, acidification, eutrophication, water use, fossil fuels, human toxicity and cumulative energy demand. The analysis results show that the fiber preparation stage is the main hotspot in terms of environmental impacts and emissions. And shows that this is followed by the lamination step. It has been determined that urea formaldehyde (UF) resin, which is used as a synthetic adhesive, has the largest share in the environmental effects of MDF-LAM production. In this study, CED was evaluated as another impact category. This evaluation result showed that the fiber preparation subsystem had a higher CED than the other stages. In addition, it was determined that renewable biomass and non-renewable fossil were the most affected categories, while UF resin use and electricity consumption were the most important hot spots in terms of non-renewable and renewable resources.

The reason for conducting this research was to examine asphalt mixtures and the influence of additives obtained from recycled Polyethylene Terephthalate (PET) on their mechanical properties. Due to this, after the chemical recycling of PET, the substance resulting from the chemical reaction was added to the asphalt binder in different contents. In order to evaluate the mechanical performance of mixtures containing additives, a variety of different mechanical tests were carried out. In order to accomplish this goal, tests including dynamic creep, indirect tensile strength (ITS), and indirect tensile modulus (IDTM) were carried out to determine rutting, moisture susceptibility, and resilient modulus, respectively. The SCB test is used to determine how well a material resists cracking when subjected to low temperatures. The results showed that the addition of an additive derived from recycled PET could increase the rutting resistance, significantly improve resistance against moisture damage and increase cracking resistance at low temperatures. In accordance with the findings of the indirect tensile strength tests, indirect tensile modulus and SCB was the best performance related to the asphalt mixture containing 2% recycled PET. However, this result was different in the dynamic creep test, and the asphalt mixture containing 1% additive showed the best performance. The results of data analysis with one-way analysis of variance showed that all the data obtained in this study are statistically significant considering the confidence factor of 95%, so it can be said that the addition of recycled PET additive has a significant effect on the mechanical properties of the asphalt mixture.

Design standards necessitate the use of a sufficient lap splice length when dealing with longer spans of Reinforced Concrete (RC) members. An inadequate lap splice length results in a reduction of both the flexural strength and ductility of reinforced concrete beams. The failure risk of these beams is considered a potential threat which is experimentally identified, numerically analyzed, and carefully mitigated in this research to increase building safety and sustainability to avoid risk of construction failure. The ongoing experimental and numerical research focuses on examining the structural performance of RC beams with insufficient lap splice length, which have been fortified through various applications of Engineered Cementitious Composite (ECC) ferrocement layers. A total of eleven beams, divided into four groups, were purposefully designed and tested under bending loads until they reached the point of collapse. The investigated parameters included the casting technique, installation strategy, and anchorage length (La) for such layers. Cast in situation and pre-casting scenarios were utilized in order to cast the strengthening ECC layers. The La for all layers was designed to be the main studied variable beside type of casting and installation technique. Three La values were studied: 30D, 40D, and 50D where D is the bar diameter of main reinforcement steel in tension side. It was found that, the application of chemical anchor bolts in cast in situation ECC ferrocement layers credited the higher enhancement in both cracking and ultimate stages by about 92–137% and 114–164% for cracking and ultimate levels, respectively. Then, the experimentally measured outcomes were employed for developing nonlinear Finite Element Models (FEMs) to simulate the performance of such ECC ferrocement layers that employed. The variance between numerical results and experimental counterparts ranged in between 6% and 9%, achieving an acceptable variance.

In this study, foam concretes (FCs) were developed, and their tension, shear, and bond properties were investigated for potential repair applications. Seven FC mixtures with varying combinations of ground granulated blast furnace slag (GGBS) and fly ash (FA) were prepared, along with one M25-grade conventional concrete mixture. The tension properties of both types of concrete were assessed through split tensile strength, flexural strength, and a pull-off test while the shear and bond strength (with reinforcing bars) were determined using the slant shear test and pull-out test, respectively. The results indicated that the compressive strength of the FC mixtures at 28 days ranged from 21.98 to 40.08 MPa, satisfying the requirements of IS 456: 2000 for M15 to M30-grade concrete. Furthermore, the split tensile strength of FC was in the range of 2.21 MPa to 2.83 MPa, while M25-grade concrete showed a strength of 2.24 MPa. Shear strength for FCs ranged between 6.67 MPa and 8.08 MPa while that of the M25-grade concrete was 5.49 MPa. Additionally, the tensile bond strength of FCs fell within the range of 0.67 MPa to 1.46 MPa while that of the M25-grade concrete was 1.12 MPa. The bond strength obtained from the pull-out test for FCs was observed to vary within the range of 11.87 MPa to 23.26 MPa while that of the M25-grade concrete was 14.14 MPa. FCs exhibited superior bond strength compared to M25-grade concrete with both the concrete substrate and reinforcing bars. It was also noted that the tension and bond strength of FC were linearly correlated with its compressive strength. Microstructure analysis indicated that macropores were isolated and discontinuous in all FC mixtures. The improvement in mechanical and bond properties was attributed to enhancements in the microstructure, and the ability of GGBS and FA particles to fill pores in the cementitious paste regions. In conclusion, FC developed using the GGBS and FA as substitutes for cement and sand, respectively showed promise as an alternative concrete repair material, with comparable or superior tensile and bonding properties compared to M25-grade concrete.

The uniaxial compressive strength (UCS) of the backfilling body plays a crucial role in backfilling safety. To study the feasibility of preparing new cementitious materials by Ti tailings, 90 sets of backfilling ratio tests and UCS tests with different Ti tailings replacement ratios were carried out. The test results showed that the UCS tended to decrease as the ratio of Ti tailings replacing cement increased, and the UCS decreased sharply after the ratio of Ti tailings replacing cement exceeded 80%; however, the UCS increased at 28 days when the ratio of Ti tailings replacing cement did not exceed 10%. Meanwhile, to accurately predict the UCS, the whale optimization algorithm and random forest (WOA-RF), particle swarm optimization and random forest (PSO-RF), and sparrow search algorithm and random forest (SSA-RF) hybrid models were constructed. Moreover, the input parameters of the models include the ratio of Ti tailings, concentration, curing age, ratio of P.O42.5 cement and cement-sand ratio. In addition, a single RF model was constructed for comparative analysis, the four models (RF, WOA-RF, PSO-RF, and SSA-RF) were trained and tested, and the root mean square error (RMSE), coefficient of determination (R2), and mean absolute error (MAE) of the four models were obtained: (0.532, 0.922, 0.416), (0.254, 0.975, 0.209), (0.367, 0.961, 0.300) and (0.318, 0.965, 0.258), respectively. The research showed that the WOA-RF model achieves better performance (R2 = 0.975), which proves that it is a better prediction model for predicting the USC of new cementitious filler with Ti tailings replacement.

This paper presents a different way using crumb rubber and fine sand totally replaced for silica sand within ECC mixtures to make rubberized engineered cementitious composites (R-ECC) to solve the issues of high construction cost of the road-bridge link slab for fully jointless bridges (FJBs). The crumb rubber with a size of 80 CR was replaced with fine sand from a volume rate of 5–20% in multiples of 5% to prepare the R-ECC material. Five different R-ECC mixtures (CR0-CR20) with different mix designs were prepared and tested, then an optimum mix proportion for the R-ECC mixtures was found. An R-ECC road-bridge link slab made of the optimum mix proportion which replace with fine sand in a volume rate of 15% was constructed, and its absorptive deformation capacity, tensile performance, and crack distribution under the most unfavourable load (temperature drop load) were studied. It is found that the R-ECC slab has good absorptive deformation capacity, crack control capacity and better internal force distribution. Therefore, R-ECC mixtures can be utilized for road-bridge link slab construction. Then, a sensitivity finite element comparative analysis was carried out considering the content of crumb rubbers, the friction coefficient and the slab length. It is found that the design length has a greater influence on the tensile performance of the R-ECC slab than other factors. Finally, a preliminary design theory of road-bridge link slab for FJBs has been established.

Composite slabs, consisting of a precast plank and a cast-in-situ concrete topping, are the most commonly used horizontal structural components in prefabricated buildings. In order to solve the problem that the precast plank of composite slab is easy to crack and a lot of vertical supports are needed in its construction, this study proposes a new type of composite slab with a joint. The precast plank of this novel composite slab is fully prefabricated in the midspan area, and concrete is poured on-site only at the surrounding joints. In this paper, the bending performance of three composite slabs with a joint in different shapes of concrete topping and one cast-in-situ slab was investigated. The test results showed that the novel composite slabs with a joint in T-shape and trapezoidal concrete topping had similar properties as the cast-in-situ slab, including bearing capacity and cracking load, which can meet practical requirement. The use of bent-up steel bars and roughening of the interface between the precast plank and topping concrete can ensure effective transmission of internal forces at joint. The bearing capacity of the composite slabs with a joint in T-shape and trapezoidal concrete topping was evaluated using the formula in GB50010–2010, and the experimental values were 1.06 and 1.1 times the theoretical values, respectively, which provides a foundation for the design of two types of composite slabs with a joint. Meanwhile, based on the FEA software ABAQUS, numerical simulation was conducted on the composite slab with a joint in T-shaped concrete topping. The numerical finding exhibit close agreement with experimental results in terms of load-midspan deflection curve and the crack distribution.

Compared to traditional soil improvement methods such as preloading, vertical drains, or grouting injection, et al., pile-supported reinforced embankments are increasing widely employed in the construction of highways on soft soils. A series of three-dimensional model tests on pile-reinforced embankments, utilizing a square arrangement for pile caps, were conducted to investigate the effects of pile-subsoil relative displacement, embankment height, tensile strength of geotextiles, and clear spacing of pile caps on the stress concentration ratio and the height of the equal settlement plane. The results indicate a close relationship between the soil arching effect and pile-subsoil relative displacement. The stress concentration ratio, from the results of this study, reaches its maximum value when the pile-subsoil relative displacement is approximately 6–8 mm. A larger embankment height to pile-cap clear spacing ratio, h/s, as well as the of pile-cap width to its clear spacing ratio, b/s, will result in a larger stress concentration ratio and a smaller differential settlement on the embankment surface. The inclusion of geotextiles can effectively enhance the soil arching effect, i.e., increasing the stress concentration ratio and lessening the fill differential settlement, especially for those low embankments. The model test results also shown that the height of the equal settlement plane in 3D soil arch is approximately 3.5 times the pile-cap clear spacing regardless of the inclusion of the geotextiles or not. In addition, by comparing the measured stress concentration ratio with the calculated values from various design methods, valuable conclusions have been derived.

In this study, the effect of steel rolling technique, temperature, yield strength and welding heat input on the impact toughness of high-strength steels is studied. The impact toughness of five kinds of high strength steels with yield strength of 550 MPa, 690 MPa and 890 MPa are experimentally studied. The standard Charpy V-notch test is carried out and the absorbed energy AKV of the test specimens is obtained. The test results show that the impact toughness of QT550 high-strength steel is not sensitive to temperature and it also has good impact performance at low temperature. For other high strength steels, with increase of steel strength, the impact toughness is severely degraded with decreasing temperature. For the effect of rolling technique on impact toughness, the QT type high-strength steel generally follows the law that the impact toughness deteriorates with the increase of the yield strength. QT process can produce better impact resistance than TMCP process for 690 grade steel. The effect of temperature on the impact toughness of WM is intensified at high heat input. The impact toughness of the base material (BM), heat-affected zone (HAZ) and weld metal (WM) deteriorates with the rise of the yield strength. QT550 and QT690 show different impact characteristics for HAZ and WM. The former HAZ has better impact performance under high heat input while WM is better under low heat input; both HAZ and WM of QT690 show higher impact toughness under low heat input.

Fiber reinforced polymer (FRP) is evaluated as an excellent material to replace rebar in reinforced concrete due to its advantages such as high tensile strength-to-weight ratio and high corrosion resistance. Many studies have been conducted to use FRP as substitutes for steel rebar. However, most of these studies were conducted using FRP bars, and research on using FRP grids in the construction field is focused on the field of repair and strengthening. Therefore, this study reports the results of an experimental study to evaluate the flexural behavior of concrete beam with Carbon FRP (CFRP) grid tensile reinforcements as a basic study to evaluate the feasibility of using FRP grid as a as substitutes for steel reinforcement. Thirteen test specimens were prepared for the experiments. The CFRP grids were applied to the specimens as tensile reinforcement. The concrete cover thickness, layers of the CFRP grid and the spacing between the CFRP grids were considered as test variables. The experiment results showed that the specimens without spacing between the CFRP grids were destroyed by side CFRP grid fracture. Also, as the CFRP grid layer increased, the ultimate load increased by 53% to 94%, and when the cover thickness decreased by 10 mm, the ultimate load decreased about 10%. The ratios of the nominal flexural strengths calculated according to the CSA S806–12 and ACI 440.1R-15 standards were 1.004 and 1.09, respectively. Thus, the use of the CSA S806–12 standard enables a relatively accurate prediction of the nominal flexural strength of concrete beams reinforced with CFRP grids.

This study investigates the feasibility of using mudstone to enhance poorly graded gravel in certain arid regions of the S21 Altay-Urumqi Highway project in Xinjiang. Despite mudstone typically being considered a poor-quality rock, its combination with higher-performance materials like cement, lime, and fly ash can stabilize expansive soils for use as roadbed fill. In the experiments, 30% and 40% mudstone were added to the gravel mixture. The experiments were compared with unmodified K80 and 35% crushed rock mixes. The findings reveal that adding 30% mudstone substantially increased the California Bearing Ratio (CBR) of the gravel mix by over 20%. However, excessive mudstone inclusion could weaken load-bearing capacity. Moreover, mudstone-modified specimens exhibited superior unconfined compressive strength (UCS), splitting strength, compressive resilience modulus (CRM), drying shrinkage resistance, and temperature shrinkage resistance. Under optimum cement dosage, the UCS of mudstone-modified specimens outperformed unmodified specimens, consistently surpassing fly ash-altered groups. Although mixed fly ash initially exhibited lower strength, it gradually approached cement-stabilized strength with an extended curing time. Incorporating crushed stone into the grading curve significantly increased splitting strength due to its high strength and hardness. In contrast, adding mudstone introduced a notable proportion of fine aggregates, resulting in a looser grading skeleton prone to early cracking. This research demonstrates that mudstone enhancement significantly improves roadbed performance, including increased CBR, splitting strength, and crack resistance. The use of mudstone in arid desert areas enhances overall performance while reducing shrinkage coefficients. The suggested approach for semi-rigid pavements in arid deserts recommends specific mineral proportions, various aggregate sizes, an appropriate amount of cement, and 30% mudstone to create dense structures with a higher quantity of coarse aggregate.

Masonry structures primarily rely on their walls as the principal load-bearing components. The walls are brittle materials such as natural stone, sandstone and brick. The walls of masonry structures have lack of the deformation capacity and to resist the tensile stresses caused by earthquake forces, settlement of foundation, and so on. To avoid loss in bearing capacity or to have more strength against lateral loads, during the production or after some precautions can be taken. The aim of this study is to investigate the behavior of strengthened aerated concrete walls by clamps. Six samples were tested under diagonal compression. All tested samples were knitted with mortar advised by the aerated concrete producer. The left five samples were knitted using different orientation of clamps and anchors made out of Ø12 deformed bars and welded plates. According to the experimental test results, it was observed that the interconnection of aerated concrete blocks with different combinations had increased stiffness, energy consumption capacity, and load bearing capacity of the walls. In addition to the brittle behavior of the reference specimen, the strengthened wall specimens have exhibited more ductile behavior.

In order to facilitate the effective implementation of the MEPDG, researchers concentrate on quantifying local material properties, with a particular emphasis on pavement layer moduli. The layer modulus is a critical parameter necessary for calculating pavement responses (stress, strain, and deflections) resulting from traffic loading. Accurately determining the layer modulus is crucial for enhancing pavement design as it directly impacts the required pavement layer thicknesses and associated costs. Backcalculation is a commonly used method for analyzing Falling Weight Deflectometer (FWD) data to determine pavement layer moduli, with Artificial Neural Networks (ANNs) being the traditional choice. However, ANNs have limitations in terms of convergence accuracy and generalization capability. The aim of this study is to improve the backcalculation of layer moduli to enhance pavement design. By utilizing FWD data, Recurrent Neural Network (RNN) was employed to address the limitations of conventional ANN. Both ANN and RNN networks were developed and trained using identical properties. The findings demonstrate that RNN achieved faster convergence and higher convergence accuracy compared to ANN. The RNN network generated reasonable and precise layer moduli values, exhibiting a determination coefficient (R) of 0.95 in comparison to the measured values, while the ANN network had an R-value of 0.79. The results indicate that the RNN network can learn the continuity pattern between deflection basin points, thereby enhancing the accuracy of FWD backcalculation.

This investigation delves into the mechanical characteristics of Basalt Fiber Reinforced Concrete (BFRC), with a specific focus on compressive, flexural, and splitting tensile strengths. Employing a Multi-Output approach, six Machine Learning (ML) algorithms, namely Adaptive Boosting (AdaBoost), Light Gradient-Boosting Machine (LightGBM), Gradient Boosting, Extreme Gradient Boosting (XGBoost), K-Nearest Neighbors (KNN), and Random Forest, were used to predict the three output variables concurrently. The SHapley Additive exPlanations method facilitated sensitivity analysis, identifying influential factors, while Partial Dependence Plots (PDP) enhanced the comprehension of input impacts on the output values. The study revealed that the XGBoost algorithm exhibited superior performance, achieving an impressive R-squared value of 0.94 in predicting BFRC mechanical properties. Key parameters affecting compressive, flexural, and tensile strengths were pinpointed, emphasizing the critical roles of the water-to-cement ratio and coarse aggregates. PDP diagrams further unveiled optimal parameter ranges. The innovation of this research lies in its simultaneous prediction of multiple outputs, an approach that enhances the comprehensive assessment of BFRC mechanical properties. Furthermore, the utilization of SHapley Additive Explanations offers a robust method for interpreting results, enhancing transparency in model predictions. Lastly, the identification of critical parameters using PDP contributes valuable insights into the nuanced relationships governing BFRC behavior. Together, these innovations propel the field towards more accurate, interpretable, and insightful predictions in the realm of concrete technology.

Asphalt surface layer as one of the significant pavement layers is directly withstanding traffic loading and external service conditions, and its performance highly determines the life cycle cost of asphalt pavements. Bitumen ageing is an unavoidable process for asphalt surface layer, and it shortens the service life and increases the risk of distress of asphalt pavements. A large number of studies have been conducted on the consequences of asphalt surface layer ageing under ambient environmental conditions. However, the development of asphalt mixture performance under Norwegian conditions and ageing model for the in-service bitumen have not been extensively investigated. Therefore, this work aims to investigate asphalt surface layer performance over service time and establish ageing model for the in-service bitumen. To achieve this goal, core samples acquired from the field and bitumen extracted from in-service field cores were analysed by comparing them with reference bitumen and asphalt mixtures. The physical, chemical, viscoelastic and performance grade variables of the bitumen were characterised, as well as the dynamic modulus and density of asphalt mixtures. The ageing models for bitumen property parameters were established using bitumen type, service time and average annual temperature as independent variables after statistical data processing. As a result, a good agreement between predicted values and measured values of property parameters was achieved because of the high accuracy of prediction of the ageing model. The proposed ageing model for bitumen under Norwegian conditions is beneficial for predicting bitumen properties at specific service time.

High content Styrene-butadiene-styrene (SBS) modified asphalt binder is commonly used for permeable pavements attribute to reasonable adhesion ability, deformation resistance and toughness. However, due to the large difference in molecular weight between styrene-butadiene-styrene block copolymer and asphalt, the compatibility between SBS and asphalt has always been a key issue restricting its development. To improve the compatibility of high content SBS modified asphalt, the preparation process of high content SBS modified asphalt (shear time, temperature, rate, modifier content) was investigated by orthogonal experimental design method. The effects of modifiers (polyphosphoric acid, montmorillonite, and sulfur) on the physical properties and compatibility of high content SBS modified asphalt were investigated by physical property tests, storage stability tests and dynamic shear rheology tests. The results shows that all three additives have improved the storage stability of high content SBS-modified asphalt, among which, nano montmorillonite has the best comprehensive improvement effect. In addition, the preparation process of high content SBS modified asphalt will also affect its physical properties and compatibility. When the content of MMT and SBS is 2% and 8% respectively, the shear temperature is 170 °C, the shear rate is 4000 rpm, and the shear time is 150 min, the high and low temperature performance of high content SBS modified asphalt is good and the compatibility is the best.

Cement tailings storage (CTS) in goaf may experience static and dynamic loading, such as rock stress, mine earthquake and blasting stress. When subject to dynamic loading, the risk for liquefaction of CTS may cause goaf barricade instability. To better understand the effect of cement content on CTS liquefaction resistance. Static and cyclic triaxial tests were conducted to determine the parameters required for the dynamic response analysis of CTS storage. A finite element analysis using LS-DYNA carried out to study the blasting response of CTS storage. The results indicated that the liquefaction resistance of CTS significantly improved with the cement content increased. The CTS exhibited near-static liquefaction when cement content was less than 2.42%. However, CTS cement content greater than 2.93% exhibited strain hardening or weak strain softening with low liquefaction index. The CTS with cement content 0–2.93% initial liquefaction less than 38 cyclic loading. Dynamic response analyzed showed liquefaction risk decreases as blasting distance and cement content increased. For blasting distances greater than 30 m, the CTS cement content of 3% is sufficient to resist liquefaction under blasting. The findings are conducive to the design of appropriate CTS underground storage parameters.

In order to reduce the CO2 associated with cement production, this study explored the potential of rice husk ash (RHA) and fly ash (FA) as supplementary cementitios materials for partially replacing cement in concrete production. The study aimed to analyze the synergistic effects of a cement-based mixture consisting of RHA and FA in different proportions on concrete's fresh, hardened, non-destructive and microscopic properties. In addition to the experimental work, this study successfully applied machine learning to predict the compressive strength of RHA-FA concrete using three types of algorithms: ANN (Analytical Neural Network), XGB (Extreme Gradient Boosting), and GBM (Gradient Boosting Model). A total of 138 data points were used for this prediction, and statistical and parametric analyses were performed to define the impact of input parameters on the outcome. Furthermore, both destructive and non-destructive tests were conducted on hardened concrete, including compressive strength, split tensile strength, ultrasonic pulse velocity (UPV), and rebound hammer. The scanning electron microscope (SEM) was operated to analyze the microstructural characteristics of concrete. The compressive and split-tensile strength test results showed that the mixture with a higher percentage of fly ash and a lower percentage of rice husk ash achieved maximum strength. The X-ray Fluorescence (XRF) analysis revealed that both ashes contained a significant amount of silica, which gave them excellent pozzolanic properties. After 28 days, both the UPV and the rebound hammer strength align with the destructive compressive strength results. The study also employed SHAP (SHapley Additive exPlanations) and PDP (Partial Dependence Plot) analyses to identify the optimal range for each parameter's contribution to strength improvement. The machine learning models exhibited a strong correlation with the test results, achieving an R2 value of 0.84 for the XGBoost model.

The innovative utilization of sugarcane bagasse ash (SCBA) in producing lightweight concrete (LWC) needs to be explored experimentally and quantification with machine learning approaches. Therefore, this study aims to investigate fresh, mechanical and microstructural characteristics and machine learning modeling of incorporating SCBA as a partial substitute of cement. In this investigation, OPC was replaced partially by the weight of SCBA in the proportion of 0 %, 5 %, 10 %, 15 %, and 20 %. The influences of SCBA on the fresh characteristics of concrete were investigated through tests of the slump, compacting factor, Kelly ball, k-slump, density, and air content. In addition, for hardened properties compressive, splitting tensile, flexural strength, and static modulus of elasticity were tested at 7 and 28 days. Furthermore, a microstructural characteristic was carried out for varying content of SCBA. Different machine learning (ML) predictive models were performed utilizing artificial neural network (ANN) and random forest (RF), to predict the fresh and mechanical attributes of the LWC. It was noticed that the workability value of fresh concrete was enhanced almost by 40 % to 50 % with the incorporation of SCBA content. The hardened test results revealed that a mixture having SCBA up to 10 % content SCBA resulted in nearly 10 % to 30 % better performance to satisfy the requirement of LWC. Regarding the sustainability assessment, the less embodied CO2 (eCO2) is produced in SCBA mixes, whereas it is also economically beneficial to produce SCBA mixes. Models' efficacy was evaluated including mean absolute error (MAE), root mean squared error (RMSE), and coefficient of determination (R2). The maximum R2 and minimum RMSE came across for RF (0.989 and 1.393, respectively) which provides the well estimation of the model.

Desert Sand Autoclaved Brick(DSAB) represents a novel type of building wall material. To investigate the performance of this wall material in the high-intensity cold regions of Xinjiang, this study, based on the(GB/T 11945–2019) ''Autoclaved sand-lime solid brick and solid block'' standard, explores the impact of varying lime content, forming pressure, autoclaving time, and autoclaving temperature on compressive strength. The aim was to determine an appropriate preparation process for DSAB that meets meets MU15-grade requirements. Additionally, experimental research was conducted on the micro-pore structure, freeze-thaw durability, and carbonation performance of the manufactured MU15-grade DSAB. Furthermore, microscopic analysis methods were employed to analyze the mechanisms behind the changes in the strength of the DSAB throughout the various experiments. The research findings are as follows: The optimal preparation parameters for producing MU15-grade DSAB are a forming pressure of 20 MPa, an autoclaving time of 8 h, and an autoclaving temperature of 180 ℃. Mercury intrusion porosimetry(MIP) revealed that DSAB has a total porosity of 38.19%, an average pore diameter of 55.86 nm, total pore volume of 0.175 mL/g, and total pore area of 12.56 m2/g. The majority of pore spaces consist of harmful and more harmful pores. DSAB exhibits favorable freeze-thaw durability. After 30 freeze-thaw cycles, the strength loss rate is only 7.0%, and the mass loss remains within 1%. After carbonation, the newly formed CaCO3 and SiO2 fill the brick's pores, transforming pre-existing harmful large pores into harmless tiny pores. After complete carbonation, the carbonation coefficient reaches 1.17.

This study proposed the novel idea of anaolian sand-red mud-fly ash cemented paste backfill (ARFCPB) to realize low-carbon backfill mining. This idea realizes large-scale disposal and resource utilization of red mud (RM) and fly ash (FA) solid wastes. The influence of the FA/RM mass ratio and mass concentration on the mechanism of action of ARFCPB was explored through comprehensive rheological performance, mechanical property, microscopic, and leaching toxicity tests. The results showed that the fresh ARFCPB slurry could be described by the Herschel–Bulkley model (R2 ≥ 0.964). As the FA/RM mass ratio increased, the ARFCPB slurry yield stress decreased, the thixotropy decreased, and the slump increased. This is because RM has a large specific surface area and an unsmooth surface, resulting in greater water absorption by RM than by FA. In addition, the uniaxial compressive strength (UCS) of ARFCPB can meet the needs of backfill mining with higher strength requirements. UCS first increases and then decreases with increasing FA/RM mass ratio, which is optimal when the mass ratio of FA to RM is 4. When the FA/RM mass ratio was 4, the UCSs of specimens A4 and B4 with mass concentrations of 78% and 80%, respectively, were 5.6 MPa and 6.4 MPa after 28 days of curing. The leaching results of heavy metal ions in group B4 meet the Class III groundwater standards and can be used for centralized drinking water sources and industrial and agricultural water. Considering the fluidity characteristics, mechanical properties, and leaching results, B4 was identified as the optimal formulation. Finally, the microstructure of the ARFCPB was studied using ultrasonic pulse velocity (UPV) and SEM. The results can contribute to clean production in the aluminum production industry, coal-fired power plants, and coal mines.

The article substantiates the possibility of obtaining composite materials with improved functional properties to strengthen the subgrade, containing technogenic soil stabilized by an additive based on a gelling polymer. The introduction of technogenic soils into composites will not only reduce the consumption of expensive materials, but also solve a complex of acute environmental problems. Composite materials can be used in the construction of structural layers of road pavements, foundations of buildings and structures, sites for various purposes, for the prevention and elimination of defects in the foundations of engineering structures during their construction, reconstruction and repair, including in permafrost areas. Stabilized technogenic soils are more durable, frost-resistant and waterproof, which makes them applicable for creating impervious curtains in hydraulic structures and sealing storage facilities for hazardous substances. The cryogenic effect on a composite material allows one to vary its properties within a wide range and modify its macroporous structure. Studying the process of structure formation of the resulting organic-inorganic materials, consisting of macromolecules of high-molecular substances and inorganic inclusions that have undergone cryogenic treatment, will make it possible to specifically regulate their performance characteristics. The best values of strength characteristics were obtained for samples with a stabilizing additive concentration of 100 g/l. The resulting composite materials are hydrophobic, frost-resistant, characterized by a compressive strength of 2.3–6.5 MPa and a thermal conductivity of 0.19–0.20 W/(m·K). Data from differential scanning calorimetry and thermogravimetry and IR spectroscopy revealed that the binding of mineral particles by a stabilizing additive occurs due to the formation of organomineral complexes with the participation of clay minerals and the restructuring of hydration shells. SEM data indicate that crystallinity zones formed due to hydrogen bonds of hydroxyl groups of neighboring polymer chains can participate in the formation of the composite structure. An increase in the number of cryogenic treatment cycles promotes additional structuring and strengthening of the polymer phase due to the formation of additional nodes of the supramolecular network, ordering of crystallinity zones and the appearance of compacted areas in the structure. Computed X-ray tomography revealed an increase in the density of the composite upon drying, which helps to increase its strength characteristics. The structure of the sample is characterized by heterogeneity of the pore space, which is characterized by the presence of both fine-porous and large-porous regions, which determines its thermophysical properties.

Natural loess has poor engineering properties because of its own loose and porous nature. To meet the needs of engineering construction, this study attempted to add silica micro powder mixed with cement into loess to improve its mechanical properties. The direct shear test, triaxial shear test, and scanning electron microscope (SEM) test were used to evaluate the strength characteristics and micropore structure modifications of silica micro powder and cement stabilized loess. The results showed that the addition of silica micro powder alone increased the shear strength of loess, while when silica micro powder was mixed with cement, the improvement in strength increased significantly. 3% cement with 10% silica micro powder is the optimum content to stabilize loess. The shear strength of the stabilized loess for 28 days under 200 kPa confining pressure was 2255 kPa, which was 34.9% higher than that of plain loess. Under the same cement content, the cohesion of loess increased with the increase of silica micro powder content, and the internal friction angle increased first and then decreased. The increase in curing age and the decrease in water content were positively correlated with shear strength, and the prediction formula of shear strength parameters of stabilized loess is established. In the SEM test, through qualitative analysis, it is found that the unreacted silica powder mainly physically filled the pores of loess, while the reacted silica micro powder and cement mainly combine with hydration products, which together enhanced the compactness of loess. From the quantitative analysis, it can be seen that with the addition of silica micro powder and cement, the macropores and mesopores between loess particles are transformed into small pores and micropores, the orientation of pores is enhanced, and the loess structure becomes more compact, which further revealed the mechanism of silica micro powder combined with cement to stabilize loess. The results of this study demonstrate that silica micro powder mixed with cement can effectively improve the mechanical properties of natural loess, providing a promising approach for reinforcing loess in engineering applications.

Shotcrete finds extensive applications in civil engineering, from repair and rehabilitation to new constructions. Nevertheless, shotcrete construction frequently suffers from placement issues, such as rebound and overshooting. These challenges can result in reduced operational efficiency, increased material wastage, diminished construction quality, and potential workplace hazards. It is worth noting that these placement issues are intrinsically linked to the spray characteristics of shotcrete. These characteristics are contingent upon various factors, including the material's flowability and viscosity, as well as the nozzle geometry. This research experimentally characterized the spray behavior of wet-mix shotcrete. High-speed cameras and image analysis techniques were utilized to capture and characterize wet-mix shotcrete on a full-scale spraying setup. The study experimentally determined the key placement performance parameters such as placement, rebound, and final build-up thickness and correlates the placement performance of shotcrete with the spray characteristics. The findings reveal that wider spray opening angles, smaller droplet sizes, and higher velocities contribute to improved material deposition, reduced rebound, and increased build-up thickness. The study also assesses the impact of nozzle geometry and rheology of the shotcrete mixture. Increased flowability led to slightly better spray behavior and placement. Higher material viscosity produced a more consistent spray which enhanced shotcrete performance. Multi-air jet guns, where compressed air directly contacts droplets, can enhance shotcrete spray efficiency.

In order to realize resourceful utilization of red mud in environmentally friendly building materials, variation and mechanism of the reactivity with activated temperature were studied. Moreover, red mud geopolymer repair mortars were produced with activated red mud as main precursor, and the effect mechanism of water glass modulus and slag replacement ratio on their mechanical properties were clarified. Results show that dicalcium silicate is formed at 700 °C, the Si-O and Al-O bonds of aluminosilicate were broken and reduces in polymerization during thermal activation of red mud, resulting in an increase in activity index from 0.69 to 0.85. With water glass module increasing, mechanical properties of red mud geopolymer repair mortar ascends first and then decline, reaching the best when the module is 1.6, and further optimizes by the participation of slag. When replacement ratio of slag is 30 wt%, the compressive strength, flexural strength and interfacial bonding strength of red mud geopolymer repair mortar curing for 28 days are 58.5 MPa, 10.5 MPa, and 6.26 MPa, increase 77%, 114% and 58% comparing with the reference, respectively. After that, there is no discernible growth in the aforementioned properties. The incorporation of slag increases the integrity and denseness of the hardened red mud geopolymer at various curing ages, and thus improved its mechanical properties.

The utilisation of biochar in concrete has attracted considerable attention due to its potential in enhancing the properties and sustainability of this construction material. This in-depth review delves into various aspects of biochar-concrete composites. It commences by defining biochar and exploring its production methods, physical and chemical properties. Additionally, the review provides an overview of concrete, emphasising its composition, properties and the challenges associated with traditional production methods. The incorporation of biochar in concrete brings forth several benefits, such as improved strength and durability, enhanced thermal properties and the potential for carbon sequestration. The paper examines the production process of biochar-concrete composites, covering aspects like incorporation methods, biochar selection, mixing techniques and quality control measures. Furthermore, the sustainability aspects of biochar-concrete are evaluated, considering its environmental impact, life cycle assessment, carbon footprint reduction and economic feasibility. The review also addresses the challenges and future perspectives of biochar-concrete composites, along with opportunities for research and development. This comprehensive review presents valuable insights into the properties, production and sustainability of biochar-concrete composites. It serves as a guide for further advancements in the realm of sustainable construction.

The alum industry is increasing rapidly worldwide, which leads to an increase in waste resulting from this industry, which was named dealuminated kaolin (DK). Recycling this waste into building materials presents the best solution for its disposal. In this article, for the first time, a study was conducted to investigate the possibility of recycling DK before and after suitable activation (FDK) into alkali-activated slag (AAS) cement. A new method was used to activate DK, which was exposed to 1000 °C for 2 h in the presence of 20 wt% sodium hydroxide (NaOH) to produce an amorphous material (FDK). The slag was partially replaced by different ratios (10–30 wt%) of this waste before (DK) and after activation (FDK). The setting time, compressive strength, and total porosity were monitored. Different methods were used to detect the effect of DK and FDK on the hydration products and microstructures. The results showed that the incorporation of DK into AAS cement prolonged setting time, decreased compressive strength, and increased total porosity due to its crystalline phase, low reactivity, and the increase in silica at the expense of calcium. Contrarily, the inclusion of 10 % FDK shortened setting time, increased compressive strength, and decreased total porosity due to its amorphous phase, higher calcium silicate hydrate/calcium aluminate hydrate (CSH/CASH) gel formed, and higher dissolution of slag particles due to the formation of Na2O. The other ratios of FDK showed an adverse effect due to the excessive Na2O which delayed the condensation process and hindered slag dissolution, as well as the excessive silica amount at the expense of calcium.

Titanium extraction slag (TES) is the residual tailings of high titanium blast furnace slag after secondary titanium extraction, mainly composed of silicoaluminate glass body and crystal impurities such as FeO and TiC. The special chemical composition makes the activity of TES lower than that of granulated blast furnace slag (GBFS), resulting in a large amount of accumulation and causing serious resource waste and environmental pollution. This article preliminarily explores the feasibility of using TES in oil and gas well cementing engineering with reference to underground temperature curing TES. The optimal compressive strength was obtained at a curing temperature of 70 ℃, with a 3 d strength of 15.78 MPa, which not only meets the requirements of cementing engineering but also exceeds the strength of GBFS under the same conditions. At the same time, based on the composition and structural changes of hydration products cured at 70 ℃ for 3 and 28 d, and analyzes the hydration mechanism of TES at high temperatures. The results showed that under the influence of strong alkali activation and CaCO3 nucleation, TES rapidly hydrated and almost completely hydrated at 3 d. As hydration progresses, C-A-S-H crosslinks with each other and gradually transforms into a more dense and thermally stable crystal form (Foshagite), allowing for continuous improvement in compressive strength within 28 d. In summary, TES has high activity at high temperatures, and the strength of the solidified body meets the requirements of cementing, making it suitable as a cementing material for well cementing.

Steel structures in long-term service are difficult to avoid corrosion and can be reinforced by carbon fiber reinforced polymer (CFRP) bonding method. To investigate the corrosion effect on the bond behavior between CFRP and steel, a modified cohesive zone model was proposed and verified by experiment. Then, a series of random corrosion morphologies controlled by the size and the shape of corrosion pit were generated. Finally, by importing the random corrosion morphologies and the corresponding cohesive parameters distributions into the model, a parametric analysis was executed. Results showed that the ultimate load of CFRP-corroded steel bonding system was sensitive to the size of corrosion pit, while the stiffness had identical sensitivities to the pit size and pit shape. The ultimate load would reach the peak value when the average pit width Wp,avg was 1.0 mm and the average pit depth-to-width ratio (Dp/Wp)avg was between 0.12 and 0.14, whereas the stiffness would reach a high level when the Wp,avg was between 1.0 mm and 1.2 mm and the (Dp/Wp)avg was between 0.12 and 0.14. Moreover, the effective bond length would reach a high level when the Wp,avg was between 1.0 mm and 1.2 mm and the (Dp/Wp)avg was about 0.10.

Mortar stands as one of the fundamental components in masonry construction, significantly enriching the global cultural heritage, particularly evident in ancient masonry structures. In this paper, the improvements of shear strength of mortar were studied, based on the original formulation material of sticky-rice lime mortar. The study considered the effect of different aggregates and additives on the shear strength of mortar, the shear tests and scanning electron microscopy were employed to analyze the shear strength index and microscopic shear basis of the mortar. The results showed that 2 wt% Na-SiO2 significantly enhanced the shear strength of the mortar. Furthermore, the adhesion and frictional resistance between fiber and lime played a crucial role in enhancing the mortar's shear resistance. Incorporating a 0.5 wt% fiber additive not only effectively improved the mortar's brittleness but also acted as a deterrent to crack formation. Compared to pure lime mortar, the mixture of sand and clay aggregate exhibited a larger capacity at the same volume. This mortar also showcased better plasticity and ductility, making it more suitable for structures with significant shear deformation. These analytical findings provide valuable insights for modifying mortars in the restoration of historical buildings.

This study examined the impact of various combinations of metakaolin and 15% fly ash mix (M) on the mechanical properties and durability of recycled fine aggregate concrete (RFAC), aiming to enhance the properties, cost-effectiveness, and sustainability of concrete, while also determining the optimal metakaolin admixture. And the effect of 0%, 30%, 60%, and 90% recycled fine aggregate replaced natural fine aggregate on the compressive strength, splitting tensile strength, flexural strength, and carbonation resistance of RFAC was investigated, and the functional relationship equation of the compressive strength and the model of carbonation depth were established. The results showed that the change rule in mechanical strength and carbonation depth of the recycled concrete with metakaolin were the same as those of the concrete with metakaolin natural aggregate. When metakaolin is mixed in amounts less than 15%, it has a positive effect on the mechanical properties of RFAC, particularly its compressive strength. And the increase in the dosage of metakaolin is obviously advantageous for the improvement of the carbonation resistance of RFAC. Recycled fine aggregates acted negatively on the various properties of concrete and the extent of effect increased with the increase in substitution rate. When 15% fly ash is used as cementitious material, it can be compounded with 15% metakaolin to formulate RFAC with excellent performance, and the recycled fine aggregate can be replaced by 60%.

The structure of an FRP-confined square lightweight aggregate concrete (LWAC) column was investigated, and it was found to significantly decrease the self-weight while improving the deformation capacity and bearing capacity. Twelve FRP-confined LWAC columns and three unconfined LWAC columns underwent monotonic axial compression tests. The influences of the FRP thickness and type on the compressive performance, stressstrain relationship and strain cloud maps were investigated based on digital image correlation (DIC) technology. Both types of FRP materials demonstrated a noticeable enhancement in both the strength and deformation capacity of LWAC, with CFRP having the greatest effect on strength and BFRP having the greatest effect on ductility. Compared to LWAC columns without confinement, the compressive strength of LWAC confined by BFRP or CFRP increased by 9.4∼21.9% and 24.9∼53.3%, respectively, and the ultimate strain increased by 10.6–14.2 times and 8.0–10.9 times, respectively, with increasing the thickness of FRP. DIC technology was used to accurately measure changes in the strain and the crack development of the specimens, thereby obtaining an accurate rupture strain of the FRP material. The existing models were evaluated using test data, and new models were proposed for FRP-confined square LWAC.

This paper presents research concerning the thermal firebrand reaction due to its accumulation in specimens of current construction materials commonly applied to the exterior of dwellings in southern Europe. An extensive fire experimental campaign is undertaken, in which firebrands are deposited on the plane surfaces of the material specimens and the temperature is measured on the top and bottom construction specimen surfaces. The materials chosen for this work are currently applied to either the roof, exterior walls and windows, and were recommended as either fire resistance or good behaviour for high temperatures. It will be possible to verify their firebrand reaction, more precisely, the type of ignition, the smoke, droplet production, and even their insulation capabilities. It is also tested for the efficiency of a metal mesh to prevent the entrance of firebrands into the air vents of façades and chimneys in dwellings. A thermal numerical model is also used to study the efficiency of the insulation properties of some construction materials for firebrand deposition by measuring the level of heat flux circulation during the full time analysis.

The micro-mechanical properties of asphalt surfaces are significantly impacted by short-term aging during construction and long-term aging in service. This, in turn, affects macroscopic characteristics such as asphalt-aggregate adhesion and water stability of asphalt mixtures. The study investigated different aging processes had different impacts on the micromechanical properties of the asphalt on the surface. The short-term aging process had the most significant effects, while the subsequent long-term aging had similar but less important effects. The adhesion, surface energy, and Young's modulus of five different types of asphalt using atomic force microscopy (AFM) in their original state, after short-term aging through the Rolling Thin Film Oven Test (RTFOT), and after long-term aging through the RTFOT+Pressure Aging Vessel (PAV). The results showed that ZH and SK asphalts had a distinct ''bee structure'', and aging had varying effects on adhesion, surface energy, and Young's modulus in different areas (peak, valley, and other region). Before and after asphalt aging, the adhesion and surface energy approximately followed the order other region > peak > valley, while Young's modulus approximately followed the peak>valley> other region. This indicates that the bumpy ''bee structure'' does not always correspond to higher modulus or lower adhesion. It was also found that ZH asphalt and SK asphalt with a ''bee structure'' exhibited better aging resistance compared to KL asphalt without a ''bee structure''. The study also revealed that aging led to decreased adhesion and surface energy, while increasing Young's modulus. This finding indicates that as asphalt ages, adhesion decreases and asphalt elasticity increases. Additionally, it was observed that the modified asphalt showed less change in adhesion, surface energy, and Young's modulus after aging compared to the matrix asphalt, indicating that SBS modifiers contribute to improving the aging resistance of asphalt. These results will provide a good reference for understanding the microscopic changes in asphalt aging properties.