This study develops recycled aggregate-based sandwich permeable bricks, which adopt a three-layer functional design consisting of high-strength permeable surface layer, ceramsite core layer and recycled aggregate base layer. Through structural design, performance experiments, and Life Cycle Assessment (LCA), the sponge effect enhancement mechanism and carbon emission reduction potential of the bricks were systematically explored. The results show that while ensuring engineering performance with a 28-day flexural strength of 3.12 MPa, compared with traditional permeable bricks, the recycled aggregate-based sandwich permeable brick exhibits significant performance improvements, which demonstrates a balanced integration of infiltration, storage, retention, and drainage functions and mechanical stability. LCA quantification indicates that with the functional unit defined as 1 m2 of permeable brick over a 20-year service life, the total carbon emission reduction reaches 10.13 kgCO2. A sensitivity analysis varying the ceramsite factor by +/- 20% yields a net reduction ranging from 1.97 to 18.29 kgCO2, confirming a positive carbon reduction potential. Functional emission reduction driven by the sponge effect is the primary contributor, and the carbon emissions from ceramsite core layer production are effectively compensated by the functional emission reduction. Scenario analysis based on Hangzhou's road network planning, under low, medium, and high replacement rates, the total carbon emission reductions over 20 years are 0.16, 0.75, and 1.92 million tons respectively, with the annual average emission reduction accounting for 0.01%-0.13% of Hangzhou's total carbon emissions in 2022. This study realizes the high-value utilization of solid wastes such as recycled aggregates, provides a technical path for material innovation and large-scale application in the low-carbonization of municipal pavement engineering, and supports the coordinated development of Sponge Cities and low-carbon cities.

The shrinkage deformation is a significant risk to self-compacting concrete (SCC)-filled steel tube structures. It was essential to understand the concrete autogenous shrinkage strain before being regulated in order to determine compensation shrinkage measures. In this study, A PSO-BPNN model was constructed, which is based on the Particle Swarm Optimization-Back Propagation Neural Networks (PSO-BPNN), and the autogenous shrinkage strain of SCC was predicted based on PSO-BPNN before being regulated. Moreover, some experiments about compensating for shrinkage by expansion and by a combination of expansion and contraction were investigated. Based on this prediction, a series of experiments was conducted on the regulation of the shrinkage deformation of SCC for an actual bridge project. The results indicated that a good consistency of PSO-BPNN between predicted and measured values, demonstrating that PSO-BPNN is a model with high accuracy in predicting concrete autogenous shrinkage strain before regulation, and as a guidance for regulation to compensate for shrinkage. The prediction error was less than 10% for 28-day self-shrinkage, and the experimental workload was reduced. The PSO-BPNN is a convenient tool for predicting the shrinkage of SCC, enabling the determination of dosages of expansion agent and reducing shrinkage agent to achieve SCC's shrinkage regulation.

The rheological properties of concrete paste significantly influence its tensile creep behavior. In this study, the tensile creep behavior of high-volume fly ash concrete (HVFAC) employing the same cementitious pastes was experimentally investigated, and the rheological properties of the paste containing a high volume of fly ash using the nanoindentation (NI) technique was investigated in order to explore the influence of the paste’s rheological properties (such as micro-mechanical properties and microscopic creep) on the early-age tensile creep of HVFAC. The results demonstrated that the micro-strain of paste containing a high volume of fly ash (HVFA) showed a larger value than that without fly ash. As the test age extends, a decreasing trend in microscopic creep was observed which could be attributed to the growth of the content of HD C–S–H (high density C–S–H) gel. Moreover, within the same age period, the experimental data revealed that the incorporation of fly ash resulted in the reduction of the values of the creep modulus C and characteristic time τ. The effects of fly ash dosages and loading age on the creep properties of concrete was consistent with the micro-creep properties of the cementitious paste. The tensile specific creep values derived from the ZC (“ZC” are initials for the word ‘‘self-developed” in Chinese) model based on nanoindentation data closely match those obtained from experiments.

Noise reduction is a key process in digital image detection technology for concrete cracks and bug-holes. In this study, the threshold range of the flood-filling noise reduction algorithm was investigated experimentally. Surface cracks and bug-holes in RC bridge concrete were detected using mobile terminal images based on the flood-filling noise reduction algorithm. The results showed that the error range was within 10% when threshold range Θ was confined in [60, 80] as the crack width was from 0.1 mm to 2 mm. It is suitable that the threshold range Θ was selected as 70 while the measured crack width range was 0.2 mm to 2 mm. However, by reducing the values of the threshold range Θ to 50, the miscalculation was obviously eliminated. The influences of reducing values of the threshold range on bug-holes of the equivalent diameter and area were not significant. It is suitable that the threshold range Θ was elected on 50 to detect bug-holes in the concrete surface. The threshold range can be selected as a suitable value for the detection of cracks and bug-holes in order to reduce noise.

The rheological properties of concrete paste significantly influence its tensile creep behavior. The micromechanical properties, microscopic creep, and other rheological characteristics of high-volume fly ash cementitious pastes (60% and 30%) were investigated using nanoindentation techniques in this study. Concurrently, the time-dependent tensile creep behavior of high-volume fly ash concrete (HVFAC) employing the same cementitious pastes was investigated through experimental studies, culminating in the formulation of a predictive ZC model expression that incorporates the paste's rheological properties. The results showed that the paste rheological property plays a decisive role during the tensile creep development of HVFAC at early ages. And the fly ash enhances the evolution of microscopic creep within cementitious pastes at consistent test ages. Moreover, when fly ash substitutes an equivalent mass of the original material, the convergence rate of microscopic creep accelerates as the test age progresses. The influence of fly ash and loading age on the development of HVFAC creep is consistent with the influence law of cementitious paste’s micro creep without aggregate. Base on the correlation analysis on the parameters of Et,28d/(EV+EH), Et,28d/χφ, φ and relative compressive strengthfc(t0)/fc,28d, the parameters of C, τ and test ages, it showed that these parameters are in good agreement with the function y = A+Bx. The tensile creep prediction expression of ZC model considering the rheological properties of cement paste can reflect the structure of the model unit cell.

The digital image method of monitoring structural displacement is receiving more attention today, especially in non-contact structure health monitoring. Some obvious advantages of this method, such as economy and convenience, were shown while it was used to monitor the deformation of the bridge structure during the service period. The image processing technology was used to extract structural deformation feature information from surveillance video images containing structural displacement in order to realize a new non-contact online monitoring method in this paper. The influence of different imaging distances and angles on the conversion coefficient (η) that converts the pixel coordinates to the actual displacement was first studied experimentally. Then, the measuring and tracking of bridge structural displacement based on surveillance video images was investigated by laboratory-scale experiments under idealized conditions. The results showed that the video imaging accuracy can be affected by changes in the relative position of the imaging device and measured structure, which is embodied in the change in η (actual size of individual pixel) on the structured image. The increase in distance between the measured structure and the monitoring equipment will have a significant effect on the change in the η value. The value of η varies linearly with the change in shooting distance. The value of η will be affected by the changes in shooting angle. The millimeter-level online monitoring of the structure displacement can be realized using images based on surveillance video images. The feasibility of measuring and tracking structural displacement based on surveillance video images was confirmed by a laboratory-scale experiment.

In order to explore the influence of fly ash content（0%, 30% and 60%） and loading age（3, 7, 14 and 28 days） on the tensile creep of early age concrete, the tensile creep characteristics of high volume fly ash concrete with a water-binder ratio of 0.4 are studied experimentally under a stress to strength ratio of 0.4. The results show that the tensile creep of concrete decreases with the delay of loading age. The tensile creep rate decreases exponentially with the delay of loading age at the initial stage of load holding（0-3 days） and the influence of loading age slows down in the middle and late stages of load holding（after 3 days）. The tensile creep of concrete increases with the increase of fly ash content at a given loading age. The tensile creep decreases exponentially with the increase of strength, which is more significant for concrete with 60% fly ash content.

基于监控影像和数字图像处理技术,提出了一种表征结构位置特征点位移变化的方法.首先在结构上安置圆形标靶,用模板匹配法检测圆形标靶的初始图像坐标区域,裁剪出感兴趣区域(ROI);然后用大津法确定该区域的二值化阈值,提取标靶轮廓点坐标,使用最小二乘法将轮廓拟合成椭圆,获得椭圆中心坐标及长短轴尺寸,圆形标靶直径与椭圆长短轴的比值为转换系数η;椭圆中心坐标变化量和η的积为结构实际对应坐标方向的位移量.实验表明:在水平与竖直方向的位移加载实验中,该方法与高精度位移计对比的相对误差均＜3％,可以实现mm级位移监测,精准表征结构对应特征点位移变化.

High volume fly ash concrete (HVFAC) has been widely used, and the mix proportion of HVFAC is usually designed based on the required compressive strength. Therefore, the research of HVFAC under the condition of equal strength has more engineering application value. However, in the current mix proportion design standard, there is no special discussion on the mix proportion design method of HVFAC. In this study, the compressive strength of HVFAC affected by four factors (water-binder ratio, FA content, curing method and curing age) was systematically studied. Based on 594 sets of strength data obtained from experiments, the method to determine the key mix proportion parameters (water-binder ratio and FA content) of equal strength HVFAC was proposed through machine learning algorithms (ML). Two ML methods (i.e., a multiple linear regression (MLR) and an artificial neural networks (ANN)) were developed to predict the HVFAC compressive strength and then their performances were compared. Through comparison, it was found that the mean absolute error and root mean squared error of the ANN model were both lower than the MLR model, and the ANN model has lower error and higher accuracy. In addition, the reliability of the proposed ANN model was verified with data in other literatures, the results showed the errors between the predicted values and the measured values are lower than 25%. The weight contribution rate of each factor to the strength was calculated. Among the four factors, the curing age had the greatest impact on the compressive strength, which contributes up to 60.3%. The influence degree of FA content is greater than that of water-binder ratio. With the development of curing age, the influence degree of FA content and water-binder ratio on the strength gradually decreases while the curing method increases. Finally, according to the ANN prediction results, the key mix parameters design method for equal strength HVFAC under multi-factor conditions was proposed, which provide guidance for concrete preparation in actual engineering.

In this study, the tensile creep (TC) of high-strength concrete (HSC) containing 30 wt% fly ash was measured at early ages to investigate the applicability of creep prediction models for concrete containing FA, and to provide ideas to study the prediction model of concrete creep containing other SCMs in the future. The TC values obtained from the experiment were compared with the predicted values of six TC models. Then the accuracy of different models was evaluated by the ratio of predicted values to experimental values. Finally, the applicability of these models to the TC of HSC with fly ash was discussed at an early age. By comparison, it was found that when the loading age was 1d, 2d, and 3d, the ZC model (ZC are the initials for the word "Self-developed" in Chinese), which is a rheology-based model for TC, proposed by Yang.Y et al. agreed with the experimental values. The predicted values of the other five models deviated significantly from the tested ones. When the loading age was 5d and 7d, the calculated results of the ACI 2009R model were more accurate. Compared with the other five models, the time dependency of the paste with fly ash was considered in the ZC model, and parameter q of the ZC model was introduced in order to characterize the influence of fly ash on the paste at early ages. Therefore, this paper demonstrated both theoretically and experimentally that the ZC model can better predict the early-age TC of HSC with fly ash.

工程伦理课程是工程硕士专业学位教育过程中的重点内容之一，是一门介绍人类正确价值观导向的课程，其教学过 程关系到专业学位硕士研究生正确的工程伦理价值判断的培养和伦理素质的提升以及社会责任担当的强化。文章深 入分析“课程思政”对土木工程方向工程伦理课程教学中的引领作用，探索土木工程方向工程伦理课程教学中，研 究生兴趣点的挖掘与培育，探讨走心式、入心式授课教学方法的实践，分析工程伦理课程教学方法多样化、教学评 价标准化、培育与引领同学们兴趣点等教学难点，提出了关于工程伦理课程教学过程的几点思考。

Some incineration ashes, such as fly ash, blast furnace slag etc., have emerged as eco-friendly alternatives to ordinary Portland cement in order to reduce the environmental impacts. However, it is still unclear that the sludge incineration ash (SIA) which comes from lake or river sludge after incineration can also be used as that or not. In this paper, the pozzolanic activity and chemical excitation assay of SIA were experimentally studied in order to be used as a raw bonding material, and the performances of pervious ecological brick prepared with SIA were investigated. The results showed that the activity index of SIA was similar as that of FA, and it can be used as auxiliary cementing material in concrete instead of part of cement. The hydration process of incineration ash in cement-SIA composite cementitious system can be promoted by chemical activators such as NaOH, Na2SO4, Na2SiO3 and NaAlO2. The activation effect on SIA of multi-component exactor combination which optimized by orthogonal experimental methods was better than that of a single component exactor. It is a new green disposal path of sludge from lake or river which contains humus and pollutants. The permeability, water conservation and freezing resistance of pervious ecological brick which prepared with the SIA-cement paste can meet the engineering application requirements.

以水胶比(0.4、0.5、0.6)和粉煤灰掺量(0、30％、60％)为试验参数,研究不同养护方式(密封养护、标准养护和干燥养护)对大掺量粉煤灰混凝土(HVFAC)抗压强度的影响规律.结果表明:干燥开始龄期越晚,HVFAC的后期抗压强度越高;不同养护条件下,粉煤灰混凝土的后期抗压强度都随着粉煤灰掺量的增长而降低,干燥开始龄期越早,水胶比越大时,随着粉煤灰掺量的提高,混凝土后期抗压强度的下降越显著;粉煤灰掺量较大(60％)时,干燥开始龄期越晚,HVFAC的后期随水胶比增大抗压强度降低速率越快;粉煤灰掺量较小(30％)时,干燥开始龄期越晚,水胶比增大导致的HVFAC后期抗压强度的下降程度越小.

Sewage sludge ash (SSA) is a kind of solid waste which has to be dealt with. Recycling SSA in ultra-high performance concrete (UHPC) as cement replacement is a possible solution. However, related attempts haven't been made yet. In this paper, the effects of SSA on the fluidity and strength of UHPC were studied. The volume deformation of UHPCs under different environmental conditions and the microstructure of UHPC with SSA were investigated. The environmental evaluation on UHPC containing SSA was performed, and the feasibility of recycling SSA in UHPC was discussed. The results showed that the addition of SSA gradually reduced the fluidity and flexural strength of UHPC. The 3d compressive strength of UHPC was also decreased with higher SSA content; however, the7d and 28d compressive strength of UHPC with 10% SSA was slightly increased. The autogenous shrinkage and drying shrinkage were enlarged by adding SSA. Nevertheless, UHPCs with SSA showed expansion when immersed in water. In addition, the presence of SSA reduced the hydration heat release and increased the pore volume of UHPC. Ettringite and CaSO4 were observed in UHPC with SSA due to the high content of SO3 in SSA. The environmental evaluation showed that the recycling use of SSA reduced the environmental impacts of UHPC. Conclusively, it is possible to recycle SSA in UHPC, but further studies are needed to control the volume deformation of UHPC caused by the presence of SSA.

The structural displacement is one of the important indicators to describe the health state of the bridge during service, and the digital image method monitoring structural displacement was paid more attention. In this paper, the image processing technology was used to extract structural deformation feature information by the surveillance cameras images containing structural deformation. A new non-contact measurement method of structural displacement using surveillance camera and digital image processing technology was proposed, and it was confirmed by experiments that the full-time monitoring of tracking structural displacement can be to realize by using surveillance cameras images. Comparing with two various calibration methods, the virtual circle center method based on circular object was selected in this study and it was suitable for surveillance camera calibration. Moreover, A non-contact, real-time, high-precision and convenient displacement monitoring system software would be designed, and this on-line monitoring method of structural displacement can meet to millimeter level.

将湖、河淤泥焚烧后的残渣灰(淤泥焚烧灰,简称焚烧灰)在建材领域进行资源化处置,对比了焚烧灰与粉煤灰的火山灰活性,探讨了养护龄期、焚烧灰掺量和水胶比对水泥-焚烧灰复合胶凝材料净浆硬化浆体(简称为硬化浆体)抗压强度的影响;对比了焚烧灰与粉煤灰对新拌砂浆流动性的影响,探讨了焚烧灰掺量对砂浆流动性的影响规律;采用X射线衍射仪(XRD)和扫描电镜(SEM)研究了硬化浆体的微观结构.结果表明:焚烧灰的28 d抗压强度活性指数达到83％,可作为部分替代硅酸盐水泥的胶凝材料使用;随着焚烧灰掺量的增加,含焚烧灰新拌砂浆的流动性显著下降,硬化浆体的抗压强度早期下降明显,但后期有所提高;当焚烧灰掺量为20％时,硬化浆体的抗压强度达到最大值;水胶比越小,焚烧灰对硬化浆体抗压强度的影响越显著;焚烧灰的火山灰活性促进了复合胶凝材料后期的水化反应.

Concrete crack resistance is an important factor affecting the durability of concrete structures. In order to provide the basis for the evaluation of crack resistance of high volume fly ash concrete (HVFAC), the early-age tensile properties (i.e. tensile strength, tensile elastic modulus and tensile strain capacity) of HVFAC were investigated with direct tensile tests. The results showed that the development of tensile strength, tensile elastic modulus and tensile strain capacity of concrete before 7d decreased with the increase of water-binder ratio and fly ash content, and the tensile elastic modulus decreased significantly when the fly ash content was 60%. The development of tensile strain capacity and tensile strength of concrete from 7 to 28d was remarkably faster when the fly ash content increased, while no significant effect of fly ash content on the development of the tensile elastic modulus at late ages was observed. The tensile strength to cubic compressive strength ratio (T/C) peaked at about 2d, then showed a decreasing trend and stabilized in the range of 0.055–0.132 after 7d. Moreover, the tensile strength, tensile elastic modulus and tensile strain capacity showed a good correlation with the cylindrical compressive strength of concrete. Their respective relationships with cylindrical compressive strength were proposed and could be used to predict the tensile strength, tensile elastic modulus and tensile strain capacity of HVFAC.

通过氯离子稳态扩散试验,研究了混凝土强度(C30、C50、C80)、裂缝宽度(50～600 μm)对氯离子在裂缝中扩散速率的影响.结果表明,氯离子在C30裂缝中扩散速率远小于在C50和C80裂缝中,其原因是由于C30中裂缝的曲折程度大于C50和C80;随着裂缝宽度的增大,混凝土裂缝中的氯离子扩散系数快速增大,但是当裂缝宽度大于150 μm后,氯离子在裂缝中的扩散系数基本保持不变.

提出了一种基于Android APP的混凝土表面裂缝无损检测方法.利用智能手机摄像头模组采集裂缝区域图像,通过灰度化、滤波降噪、泛洪填充等图像处理算法提取裂缝目标,根据裂缝像素点坐标间的几何关系以及裂缝所包含的像素点个数,并结合拍摄手机的单位像素点尺寸来计量裂缝特征值,实现裂缝无损检测.新开发的APP裂缝检测技术能计量检测任意点宽度、裂缝总长度、裂缝面积、裂缝最大宽度.实验结果表明:利用智能手机光学变焦,放大目标裂缝可以有效地提高APP计量检测混凝土表面裂缝精度;与裂缝测宽仪比较,APP计量检测精度误差小于5％,满足工程应用要求.

Sewage sludge ash (SSA) is the combustion residue of the sewage sludge obtained from wastewater treatment plants. In China, SSA normally contains high content of SO3, which may cause detrimental effect on the volume stability of cement-based materials. This study investigated the effect of sulfate-rich SSA (SR-SSA) on the volume deformation and the microstructure of cement paste. The autogenous shrinkage and drying shrinkage of cement pastes incorporating SR-SSA were tested. The microstructure of cement pastes incorporating SR-SSA was studied with mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The results show that the addition of SR-SSA reduced the autogenous shrinkage of cement paste, but increased the drying shrinkage of cement paste. Hence the addition of SSA may cause more serious cracking problem of cement-based materials under drying conditions, but could inhibit the cracking under sealed condition. The SEM and MIP investigations showed that, when SR-SSA was presented, more ettringite was generated in the cement paste and the porosity of the cement paste became higher.