Replacement Rate Research Articles

Effects of Partially Replacing the Commercial Soybean Meal, With A Soaked and Boiled Raw Full-Fat Soybean in Broiler Diets

The aim of this study was to investigate the effects of partially replacing the commercial soybean meal (SBM) with a home-treated, locally produced raw-full fat soybean (RFFSB) in the diets of broilers. A 3×2×2+1 factorial arrangement was used to conduct this feeding trial. A test ingredient (RFFSB) was differently soaked (0, 6 or 12 hrs), drained, boiled (25 or 35 min) and sundried. Following this, it was hammered to pass through a 0.2-mm sieve, then 12 experimental diets were formulated, replacing the SBM by such a home-treated-RFFSB at 50 or 75%. The control diet didn’t contain any RFFSBN. Totally 13 experimental diets were prepared and every treatment was replicated 3 times and 10 chicks per replicate. The results revealed that replacing the commercial SBM by a treated RFFSB had no significant interaction effects on any measured parameter. However, soaking and then boiling it (RFFSB) had significant (P<0.05) interaction effect on the BWTG (1-13d and 14-28d). When increasing the soaking time, the FI (feed intake), BWTG (body weight gain) and feed efficiency were significantly (P<0.05) decreased. When increasing the boiling duration, both FI and feed efficiency (14-28d) were improved. But, when increasing the replacement rate of RFFSB, the feed efficiency was deteriorated. Broilers fed on both control and diets, containing a non-soaked RFFSB had higher (P<0.05) BWTG (1-13d). Birds fed on diets containing RFFSB that was soaked for the longest period (12 hrs) had significantly lower BWTG. Birds fed on diets, containing prolonged boiling duration had significantly (P<0.05) higher BWTG and feed efficiency. There was no interaction (P> 0.05) effect on both carcass yield and cut-products. Neither increasing a boiling time nor a replacement rate had (P<0.05) any influence on the WT (weight) of the carcass. Birds on both control and on non-soaked RFFSB diets had better WT of carcass products. There was no interaction (P>0.05) effect on organ developments. However, increasing the soaking-duration significantly (P<0.05) reduced the organ developments. Therefore, it is concluded that commercial SBM can be replaced by a non-soaked, but boiled raw soybean in diets of broilers.

Mechanical properties of steel fiber reinforced recycled concrete under compression-shear stress state

The continuous urbanization of construction has led to an increasing demand for concrete, resulting in large-scale gravel and river sand mining, which seriously affect the sustainable development of the environment. The waste concrete produced by the demolition of old buildings is processed into recycled aggregate to replace natural aggregate, and then the preparation of recycled concrete can effectively alleviate this problem. This paper investigates the mechanical properties of steel fiber reinforced recycled concrete (SFRRAC) under compression shear conditions, a compression shear test with 99 cubic specimens was designed, with the variation parameters being recycled aggregate concrete replacement rate, compressive stress, and steel fiber content. The failure mode of SFRRAC under compression-shear stress was observed, and the shear force-displacement curve was calculated. Furthermore, a thorough examination was performed to assess the mechanical characteristics of SFRRAC specimens under compression-shear stress. The findings of this study suggest that as the compressive stress increases, the failure characteristics of the specimens shift from exhibiting brittle failure to displaying ductile failure. The shear strength is most sensitive to the change in compressive stress. When the compressive stress reaches 6 MPa, the shear strength can reach 3.41 times that of the direct shear specimen. The shear strength of SFRRAC specimens is composed of the bond strength of concrete, shear expansion strength, and friction shear strength. The incorporation of steel fibers can modify the distribution of shear strength among the individual components. The adverse effect of the recycled aggregate replacement rate on the toughness index of the specimen is mainly concentrated after the peak point. Nevertheless, an elevation in compressive stress and the inclusion of steel fibers can counterbalance this detrimental influence. The shear strength calculation formula of SFRRAC in shear state is put forward, which has a reference value. This study provides an experimental reference and a theoretical basis for further examination of SFRRAC.

Axial Compressive Behaviours of Coal Gangue Concrete-Filled Circular Steel Tubular Stub Columns after Chloride Salt Corrosion.

The axial compressive behaviours of coal gangue concrete-filled steel tube (GCFST) columns after chloride salt corrosion were investigated numerically. Numerical modelling was conducted through the static analysis method by finite element (FE) analysis. The failure mechanism, residual strength, and axial load-displacement curves were validated against tests of the coal gangue aggregate concrete-filled steel tube (GCFST) columns at room and natural aggregate concrete-filled steel tube (NCFST) columns after salt corrosion circumstance. According to the analysis on the stress distribution of the steel tube, the stress value of the steel tube decreased as the corrosion rate increased at the same characteristic point. A parametric analysis was carried out to determine the effect of crucial variation on residual strength. It indicated that material strength, the steel ratio, and the corrosion rate made a profound impact on the residual strength from the FE. The residual strength of the columns exposed to chloride salt was in negative correlation with the corrosion rate. The impact on the residual strength of the column was little, obvious by the replacement rate of the coal gangue. A simplified design formula for predicting the ultimate strength of GCFST columns after chloride salt corrosion exposure was proposed.

Why Are Unemployment Insurance Claims So Low?

The authors investigate reasons unemployment insurance (UI) claims have declined dramatically over the past 3 decades. The fall is concerning because it suggests a reduced countercyclical effectiveness of the UI program. Additionally, weekly initial UI claims are an important leading indicator of aggregate economic activity, so their meaning has changed. The authors identify the main factors that changed with the decline in claims. Their procedure suggests what the level of claims would have been later in the period, had values of variables or parameters of the system been at levels observed earlier in the period. The analysis of state-year data suggests that the decline in UI claims stems largely from changes in the industrial and occupational mix of employment interacting with changes in UI program features set by individual states. This decline could be offset by federal rules for states to improve benefit access, replacement rates, and potential UI durations.

Compression and Splitting Tensile Strength Model of Recycled Seawater and Sea Sand Concrete after Seawater Freeze–Thaw Cycles

Using seawater, sea sand, and recycled bricks to make concrete for nearshore and marine engineering can save resources and protect the environment. Therefore, this article studies the mechanical degradation law and failure mechanism of recycled seawater and sea sand concrete (SSC) after seawater freeze–thaw (SFT) cycles. Using the replacement rate of recycled brick coarse aggregate as a variable, the mass loss rate, relative dynamic elastic modulus, compression and splitting tensile strength, and microstructure changes of specimens under different SFT cycles were tested, and a mechanical performance degradation model was established. The results indicate that the SFT failure of recycled brick coarse aggregate SSC results from the action of physical SFT and chemical crystallization. Friedel’s salts without cementitious properties and ettringite with expansive properties are generated inside the concrete due to the chloride and sulfate ions in the internal concrete and external seawater reacting with cement hydration products. The formation of harmful crystals leads to the loosening of the concrete, especially in the interface area between brick aggregates and cement. The calculated results of the mechanical model established in this article agree with the test results. The compression and splitting tensile strength decrease linearly with the increase in SFT cycles.

Behavior of steel fiber-reinforced coal gangue concrete beams under impact load

In order to promote the use of new sustainable steel fibers (SF) reinforced coal gangue aggregates (CGA) concrete, impact tests were performed in this paper. The impact resistance of steel fiber-reinforced coal gangue concrete was investigated using a self-developed drop-weight facility. The test variables were the CGA replacement rate (0 %, 50 %, and 100 %), the SF volume content (0 %, 0.75 %, and 1.5 %), and the drop height of the drop-weight (0.5 m and 1.0 m). Using 15 kg of hard steel as a drop-weight, the drop-weight impact test was performed on steel fiber-reinforced coal gangue concrete beams with a span of 300 mm; the damage pattern, impact reaction force-time, displacement-time relationships, and energy absorbed by steel fiber-reinforced coal gangue concrete beams were studied. The test shows that, compared with natural aggregate, CGA reduces concrete's static mechanical properties and impact resistance, and adding SF improves the static mechanical properties and impact resistance of coal gangue concrete. As the CGA replacement rate increased from 0 % to 50 % and 100 %, the reaction force of impact of the specimens decreased by 2.54 %− 6.06 % and 3.69 %− 12.33 %. The SF volume content was increased from 0 % to 0.75 % and 1.5 %, and the reaction force of impact of the specimens was increased by 23.05 %− 32.34 % and 72.27 %− 81.84 %, respectively. The impact resistance of steel fiber-reinforced concrete beams under impact loading was investigated numerically using a nonlinear explicit finite element model in LS-DYNA. The Finite Element results were validated with experimental results. Based on the validated finite element model, a parametric study was carried out to investigate the effects of coal gangue replacement rate, steel fiber volume content, and drop height of the drop weight on the behavior of the beams. This study might provide a basis for the future engineering project applications of steel fiber-reinforced coal gangue concrete under impact conditions.

Research on uniaxial compression performance and constitutive relationship of RBP-UHPC after high temperature

Abstract This study examines the impact of the recycled brick powder (RBP) replacement rate, especially at elevated temperatures on RBP-ultra-high-performance concrete (UHPC) properties such as the stress–strain curve, Poisson’s ratio, elastic modulus, and axial compressive strength through uniaxial compression experiments. The results show that with the increase of heating temperature, the axial compressive strength of the specimen increases first and then decreases under natural cooling (NC). In contrast, Poisson’s ratio shows opposite values. The peak strain continues to increase, and the initial elastic modulus and peak secant modulus continue to decrease. Compared with NC, the axial compressive strength of the specimens under water cooling has been reduced, the peak strain is generally larger, the initial elastic modulus and the peak secant modulus are smaller, and the incorporation of RBP also has a certain effect on the mechanical properties. Through regression analysis, an equation is established to calculate the axial compressive strength of RBP-UHPC with temperature, accounting for variables such as temperature, RBP replacement rate, and cooling method. Furthermore, based on the results of axial compression experiments, a constitutive equation for axial compression in RBP-UHPC after exposure to high temperatures is proposed. Overall, the theoretical curve closely aligns with the experimental curve, verifying its accuracy.

THE SURVIVAL OF TOTAL ANKLE ARTHROPLASTIES: A DATA LINKAGE STUDY FROM THE NATIONAL JOINT REGISTRY

IntroductionDespite the increasing numbers of ankle replacements that are being performed there are still limited studies on the survival of ankle replacements and comparisons between different implants. The primary aim of this study is to link NJR data with NHS digital data to determine the true failure rates of ankle replacements. Secondary outcomes include analysis risk factors for failure, patient demographics and outcomes of individual prosthesis.MethodsA data linkage study combined National Joint Registry Data and NHS Digital data. The primary outcome of failure is defined as the removal or exchange of any components of the implanted device inserted during ankle replacement surgery. Life tables and Kaplan Meier survival charts demonstrated survivorship. Cox proportional hazards regression models with the Breslow method used for ties were fitted to compare failure rates.Results5,562 primary ankle replacement were recorded on the NJR. The 1-year survivorship was 98.8% (95% CI 98.4%–99.0%), 5-year survival in 2725 patients was 90.2% (95% CI 89.2%–91.1%), and 10-year survival in 199 patients was 86.2% (95% CI 84.6%–87.6%).When using a Cox regression model for all implants with over 100 implantations using the Infinity as the reference, only the Star (Hazard ratio 1.60 95% CI 0.87–2.96) and Inbone (HR 0.38 95% CI 0.05–2.84) did not produce significantly worse survivorship.ConclusionAnkle replacements have increased in numbers over the past decade, and the currently used implants have lower failure rates than older prosthesis. It is expected that in the future the outcomes of ankle replacements will continue to improve.

Influence of molybdenum tailings replacing river sand on mechanical properties and concrete microstructure

Many tailings are piled up, occupying land and polluting the environment. Tailings replace river sand to prepare concrete. It can reduce the tailings stockpile and slow the consumption of non-renewable resources. This study discussed the feasibility of molybdenum tailings (MTs) replacing river sand in preparing concrete. Firstly, the influence of the MTs addition amount on concrete strength was analyzed. Secondly, nuclear magnetic resonance (NMR), x-ray diffraction (XRD), thermogravimetric (TG-DTG), and scanning electron microscope (SEM) were used to characterize the microscopic characteristics of concrete with different MTs contents. The results showed that good gradation of fine aggregate could improve the strength of concrete. The optimum replacement rate of MTs was 20 %, and the 28-day compressive strength and tensile strength of concrete increased by 10.9 % and 14.9 %, respectively, compared with the control group. It cannot be considered that the greater the total porosity, the greater the strength of concrete, which was mainly determined by the proportion of pores with different pore sizes in the total pores. When the amount of MTs added was 20 %, the MTs played a role in dilution, promoting cement hydration. The hydration products can not only effectively fill the internal pores of the concrete but also improve the bond strength between the tailings and the hardened slurry, thus improving the strength of the concrete. When the content of tailings added was 50 % and 100 %, cement hydration was blocked, increasing concrete porosity, and the interfacial transition zone (ITZ) became looser, thus weakening the strength of concrete.

Effect of Composition Characteristics on Mechanical Properties of UHPMC Based on Response Surface Methodology and Acoustic Emission Monitoring.

Manufactured sand (MS) is a promising alternative aggregate to quartz sand (QS) in ultra-high-performance concrete (UHPC) in the preparation of ultra-high-performance manufactured sand concrete (UHPMC), which possesses the characteristics of high strength, low cost, and environmental friendliness. In this study, the effects of variable compositional characteristics including the water-binder ratio, the stone powder (SP) content, and the MS replacement ratio on the mechanical and flexural strength of UHPMC were compared and analyzed based on response surface methodology (RSM). Meanwhile, the damage characteristics of UHPMC during compressive and flexural stress were monitored and evaluated using acoustic emission (AE) technology. The results reveal that the compressive and flexural strengths of UHPMC are both negatively correlated with the water-binder ratio, while they are positively correlated with the MS replacement rate. They tend to firstly increase and subsequently decrease with the increase in the stone powder content. In the load-displacement curve of concrete with a high MS replacement ratio and a low water-binder ratio, the slope in the elastic stage is steeper, the stiffness is higher, and the bending toughness and ductility are also better. The specimens with a 10% to 0% stone powder content present a steeper elastic phase slope, a slightly higher stiffness, and superior ductility. The specimens with a low MS replacement ratio and a high water-binder ratio display earlier cracking and weaker resistance, and the destruction process is complex and very unstable. The damage mode analysis based on RA-AF shows that an increase in the MS replacement ratio and a decrease in the water-binder ratio can both reduce the tensile cracking of UHPMC specimens under a four-point bending test. Although 10% stone powder can marginally slow down crack growth, the failure mode is not significantly affected.

A blind validation of a deep-learning solution providing HER2, ER, and PR results from H&E-stained breast cancer specimens.

562 Background: Newly diagnosed breast cancer specimens are routinely tested for oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) status. This requires additional immunohistochemistry (IHC) +/- in situ hybridisation (ISH) assessment. This can increase laboratory/pathologist workloads and turnaround times. A computer-based approach could help to alleviate these issues. PANProfiler Breast is a deep-learning solution designed to predict ER/PR status and detect HER2 negative cases from whole slide images (WSIs) of haematoxylin and eosin (H&E)-stained breast cancer tissue. Here we present a blind validation of PANProfiler Breast. Methods: Three cohorts of H&E-stained archival breast cancers (400 cases, 692 WSIs) from St James’s University Hospital, Leeds, UK, were assigned for calibration (200 cases, 344 WSIs) and blind validation (200 cases, 348 WSIs). Slides were scanned at 40x magnification on an Aperio GT450 (Leica, Illinois, USA) scanner. PANProfiler returned “Positive”, “Negative” or “Indeterminate” for ER and PR, and “Negative” or “Indeterminate” for HER2. Results were compared to the ER/PR/HER2 status given in the corresponding pathology report. For calibration and blind validation, the WSI(s) corresponding to the IHC/ISH testing block was used for analysis. One case with missing HER2 status was excluded from HER2 analyses. Confusion matrices enabled analysis of concordance. While a conventional Positive/Negative confusion matrix was used for ER/PR, “Negative” results were used as the reference Positive event for HER2. Results: Case concordance for ER and PR status across the three cohorts ranged from 89.74-92.86% and 85.71-90.91% respectively. Additionally, sensitivity for ER ranged from 89.19-100%, with specificity ranging between 62.50-100%. For PR, sensitivity was between 87.50% and 93.48% and specificity between 75.00% and 83.33%. False negative rates for both ER and PR were between 0-10.81% and 6.52-12.50% respectively. Regarding HER2, sensitivity was relatively low, ranging between 30.77% and 37.04%. However, over 90% concordance was seen across all cohorts for cases PANProfiler predicted as HER2 “Negative”. Specificity and positive predictive value were also over 90% throughout the three cohorts. Additionally, false positive rates were 0.00%, 4.35% and 9.52% for HER2 across these same three cohorts. Test replacement rates varied amongst the cohorts with 70-84% for ER, 55-84% for PR and 22-27% for HER2. Conclusions: This blind validation of PANProfiler Breast shows impressive levels of performance for predicting ER and PR status in breast cancer WSIs. For HER2, the technology demonstrated a striking level of confidence for cases predicted as HER2 “Negative”. Further development and analysis are warranted to increase the number of HER2 negative BC WSIs that PANProfiler is able to identify.

Zinc and selenium biofortification of sourdough breads with agronomically biofortified whole wheat flour

In this study, the possibility of enriching sourdough breads with agronomically biofortified whole wheat flour (BWWF) to remedy zinc and selenium deficiencies was investigated. For this purpose, two local sourdough breads were substituted with 25, 50, and 75% of BWWF and obtained with two yeast combinations. The zinc and selenium, physicochemical, nutritional, and product properties of breads have been determined. As replacement rates increased, the zinc content in the breads increased from 11.65 to 48.66 mg/kg and 8.56–45.98 mg/kg, and the selenium content increased from 48.5 to 266.8 μg/kg and 44.9–257.3 μg/kg. The zinc and selenium concentrations of breads that met the Recommended Daily Allowances (RDA) were roughly 25–40% at the 75 and 50% substitutes. Total phenolic content (TPC) and antioxidant activity increased in both breads. The SOG breads with the A-yeast combination had a substantially higher TPC. The hardness and volume of the breads decreased with the incorporation of BWWF bran, therefore lowering their sensory properties. However, at 25% and 50% substitution rates, this was limited. In general, the B-yeast combination of both breads had a higher content of amino acids. Biofortified sourdough breads could have a significant effect on eliminating zinc and selenium.

Weight Saliency search with Semantic Constraint for Neural Machine Translation attacks

Text adversarial attack is an effective way to improve the robustness of Neural Machine Translation (NMT) models. Existing NMT attack tasks are often completed by replacing words. However, most of previous works pursue a high attack success rate but produce semantic inconsistency sentences, leading to wrong translations even for humans. In this paper, we propose a Weight Saliency search with Semantic Constraint (WSSC) algorithm to make semantic consistency word modifications to the input sentence for black-box NMT attacks. Specifically, our WSSC has two major merits. First, it optimizes the word substitution with a word saliency method, which is helpful to reduce word replacement rate. Second, it constrains the objective function with a semantic similarity loss, ensuring every modification does not lead to significant semantic changes. We evaluate the effectiveness of the proposed WSSC by attacking three popular NMT models, i.e., T5, Marian, and BART, on three widely used datasets, i.e., WMT14, WMT16, and TED. Experimental results validate that our WSSC improves Attack Success Rate (ASR) by 4.02% and Semantic Similarity score (USE) by 1.28% on average. Besides, our WSSC also shows good properties in keeping grammar correctness and transfer attack.

Investigation of sustainable pervious concrete pavement performance using waste travertine aggregate and powder

Travertine cutting generates rubble and waste powder, prompting the need for effective waste utilization. This study aims to develop travertine permeable concrete (TPC) using travertine aggregate and waste powder. An orthogonal test method assessed TPC variations in travertine powder replacement rates, aggregate grading, and void content for porosity, permeability, mechanical strength, and heavy metal adsorption ability. The void content greatly influences the amount of cementitious material and is crucial for TPC performance. To guarantee compliance with the engineering performance for fully pervious pavement, the recommended void content of TPC should not exceed 20 % to have satisfactory compressive strength and permeability. Cement replacement with 5–10 % travertine powder can satisfy engineering requirements, heavy metal adsorption, waste utilization, and CO2 emission reduction. TPC demonstrates much lower removal rates under the rapid method than the immersion method for Cd2+, Cu2+ and Pb2+, mainly due to the difference in contact time. After 25 cycles, the optimized TPC shows less mass and strength loss, demonstrating excellent freeze-thaw resistance. Furthermore, a novel lab-scale rainfall simulation system for travertine permeable concrete pavement (TPCP) was built to assess the water infiltration of TPCP. TPCP can effectively reduce runoff, reaching over 96 % within 1 h for various inflow intensities. After half an hour, the removal rates of Cd2+ and Cu2+ by TPCP were only 41.5 and 79.1 %, respectively, but TPCP achieves exceptional Pb2+ adsorption with a removal rate of over 97 % under the ternary competitive mechanism.

Green Manuring with Oilseed Rape (Brassica napus L.) Mitigates Methane (CH4) and Nitrous Oxide (N2O) Emissions in a Rice-Ratooning System in Central China

The use of oilseed rape (OS, Brassica napus L.) as a winter green manure is crucial for enhancing soil fertility and reducing chemical N application in paddy fields. However, the impacts of replacing varying amounts of chemical N with OS on CH4 and N2O emissions in paddy soils have not been well evaluated. In this study, GHG emissions, soil properties and OS decomposition in a rice-ratooning system with different OS-urea N replacement rates (0%, 25%, 50%, 75% and 100%) were investigated. Our results indicate that 84.7–90.7% of the initial C and 97.5–98.4% of the N were released during the 192-day decomposition process, and that the mineralization patterns of net C and net N in the OS residue were consistent with a single exponential decay model. The lowest CH4 emissions (9.97 g m−2) were observed at 0% OS, while the highest N2O emissions (0.40 g m−2) were observed at this level of substitution. Conversely, the highest CH4 emissions (20.71 g m−2) and lowest N2O emissions (0.07 g m−2) were observed at 100% OS. Compared to 0% substitution, 25% substitution significantly decreased GWP and GHGI without reducing rice grain yield. Environmental parameters such as soil redox, NH4+-N and residual N and C were shown to be significantly associated with CH4 emissions, whereas soil redox, NH4+-N and residual C were the main drivers of N2O emissions. In conclusion, 25% substitution of OS was the most cost-effective measure for balancing greenhouse gas emission and rice yield.

Potential of Reusing 3D Printed Concrete (3DPC) Fine Recycled Aggregates as a Strategy towards Decreasing Cement Content in 3DPC.

This paper explores the new potential strategy of using fine recycled aggregates (fRA) derived from waste 3D printed concrete (3DPC) as a substitute for cement in additive manufacturing. This study hypothesizes that fRA can optimize mixture design, reduce cement content, and contribute to sustainable construction practices. Experimental programs were conducted to evaluate the fresh and hardened properties, printability window, and buildability of 3DPC mixes containing fRA. Mixes with replacement rates of cement with fRA by 10 vol%, 20 vol%, 30 vol%, 40 vol%, and 50 vol% were produced. A comprehensive experimental protocol consisting of rheological studies (static and dynamic yield stress), dynamic elastic modulus determination (first 24 h of hydration), flexural and compressive strengths (2 d and 28 d), and an open porosity test was performed. The obtained results were verified by printing tests. In addition, an economic and environmental life cycle assessment (LCA) of the mixes was performed. The results indicate that up to 50 vol% cement replacement with fRA is feasible, albeit with some technical drawbacks. While fRA incorporation enhances sustainability by reducing CO2 emissions and material costs, it adversely affects the printability window, green strength, setting time, and mechanical properties, particularly in the initial curing stages. Therefore, with higher replacement rates (above 20 vol%), potential optimization efforts are needed to mitigate drawbacks such as reduced green strength and buildability. Notably, replacement rates of up to 20 vol% can be successfully used without compromising the overall material properties or altering the mixture design. The LCA analysis shows that reducing the cement content and increasing the fRA addition results in a significant reduction in mix cost (up to 24%) and a substantial decrease in equivalent CO2 emissions (up to 48%). In conclusion, this study underscores the potential of fRA as a sustainable alternative to cement in 3D printed concrete.

Enhancing of damping capacity in crumb rubber concrete at various damage levels: Effects of fly ash and ground granulated blast furnace slag

Crumb rubber (CR) incorporated as damping units in concrete, partially replacing natural aggregates, enhances the material's damping capacity. However, the filler type and replacement rate will usually influence the crack development of crumb rubber concrete (CRC) elements under repeated loading, which in turn influences their damping capacity at different damage levels. Thus, the damping characteristics of CRC cantilever beams at different damage levels, influenced by filler type and substitution rate, are investigated in the present paper through low-cycle repeated damage and free vibration tests. The results reveal that partial cement replacement with fly ash (FA) significantly enhances the energy dissipation capacity, especially at a 30 % FA replacement rate. Positive effects on the damping ratio are observed only when the ground granulated blast furnace slag (GGBFS) substitution rate is 30 %. For the CRC cantilever beams both with and without filler, the damping ratio shows an increasing and then decreasing trend with increasing displacement angle. The maximum damping ratio is exhibited when the displacement angle is 0.02. With increasing displacement angle, FA and GGBFS doping accelerated the degradation rate of the bending dynamic stiffness and the damage index rose faster. A model is formulated to describe the correlation between the damping ratio and the damage index in CRC cantilever beams both with and without filler. The effect of filler incorporation on the pores and microcracks may be the main reason for the damping ratio increase as observed by micro-morphology.

Research on Macroscopic Mechanical Behavior of Recycled Aggregate Concrete Based on Mesoscale.

Recycled concrete is a heterogeneous composite material, and the composition and volume fraction of each phase affect its macroscopic properties. In this paper, ANSYS APDL was used to construct a two-dimensional numerical model of recycled aggregate concrete with different replacement rates of recycled aggregate (0%, 25%, 50%, 75% and 100%), and a uniaxial compression test was carried out to explore the relationship between recycled aggregate content and its macroscopic mechanical behavior. On this basis, the numerical simulation of different strain rates (0.1 s-1, 0.05 s-1, 0.01 s-1, 0.005 s-1 and 0.001 s-1) was carried out. It was found that with the increase in the recycled aggregate replacement rate, the peak stress decreases first and then increases, and the peak strain increases continuously. When the replacement rate of recycled aggregate exceeds 50%, the overall damage area of the material increases rapidly. The strain rate will change the path of the micro-crack initiation and expansion of recycled concrete, as well as the process of damage accumulation and evolution. As a result, the unit area and shape of recycled concrete are different at different strain rates, and the damage degree of each phase material is also different.

Effect of high temperature on mechanical properties of lithium slag concrete

As the main gel material of concrete, cement is used in an astonishing amount every year in the construction industry. However, a large amount of CO2 is emitted into the atmosphere while producing cement. Therefore, it is the general trend to look for substitutes for cement and develop new green concrete. Lithium slag (LS) is the industrial waste discharged from lithium salt plants. Through testing, it is found that the chemical composition of LS has a high degree of coincidence with ordinary Portland cement (OPC) Therefore, LS can be incorporated into concrete as supplementary cementations material (SCM) to prepare lithium slag concrete (LSC). The pollution of the natural environment caused by a large number of piled-up and landfilled LS is immeasurable. Consuming and using LS in large quantities and with high efficiency not only eliminates the pollution of lithium slag to the natural environment, but also helps to reduce the amount of cement used in green concrete and truly reuse waste resources. In order to study the mechanical properties of post-heated LSC, the test were carried out for LSC specimens after high-temperature. The main influence factors were considered, including the temperatures of 20℃, 100 ℃, 300 ℃, 500 ℃ and 700 ℃, the contents of lithium slag in LSC of 0%, 10%, 20% and 30%, cooling method of LSC after exposure high temperature. The results showed that the mechanical properties of LS concrete specimens were slightly improved at 100 ℃, and when the temperature was 300 ℃ or higher, the damage to the specimens was huge and irreversible. An appropriate amount of LS (20% lithium slag content) could improve the strength of LSC. This paper also studied the relationship between lithium slag content and strengths of LS concrete. The research results show that adding an appropriate amount of LS to concrete improves the mechanical properties of concrete. When the LS replacement rate is 20%, the mass loss rate of LSC after different high temperature treatments was the minimum. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature.

Development of sustainable geopolymer with excavation soil powder as precursor: Cementitious properties and thermal-activated modification

One of the focal and challenging issues in the research on sustainable building materials pertains to the recycling of construction excavation soil. This paper developed the sustainable geopolymer containing waste soil powder (WSP) from the construction excavation soil as a precursor. The WSP contains a large number of inert components, while more active components were generated in 600–1200 °C thermoactivated WSP. Substituting WSP for metakaolin (MK) negatively impacts the alkali-activated polymerization reaction of MK-based geopolymer paste, but the geopolymer paste containing thermal-activated WSP has better micro-properties than the geopolymer paste containing un-treated WSP. Mixing WSP raises the drying shrinkage of geopolymer mortar, while the drying shrinkage is reduced with the addition of 600–800 °C thermal-activated WSP. The maximum drying shrinkage of geopolymer mortar with 75 % 800°C-activated WSP is 36.6 % lower than that of plain geopolymer mortar. Substituting WSP for MK causes a reduction in the strength and permeability resistance of geopolymer mortar. At the constant replacement rate of WSP, the geopolymer mortar containing thermal-activated WSP has better strength and permeability resistance than the geopolymer mortar containing un-treated WSP. At 100 % replacement rate of WSP, the sustainable geopolymer mortar made with 1200 °C thermal-activated WSP still has good compressive strength (36.38 MPa). The waste soil-concrete powder (WSPC) also serves as an alternative precursor for sustainable geopolymer materials. Substituting WSPC for 100 % MK in geopolymer is feasible, and the geopolymer made with 800 °C thermal-activated WSPC is much greater than the geopolymer made with un-treated WSPC. Optimizing WSP/WSPC substitution rate and thermal activation temperature can achieve the sustainable geopolymer materials with good performance.