Abstract: Fine aggregate constitutes a vital component of asphalt mixtures, exerting a profound influence on their pavement performance and service life. Fine aggregate angularity (FAA) dictated the internal interlocking structure and compaction density of the mixture. It served as a critical factor in enhancing pavement performance, mitigating early-stage distresses, and extending the service life of the road. According to the industry standard (JTG E42-2005), the FAA test employed funnels with orifice diameters of 12 mm and 16 mm to measure the flow times of particle size fractions of 0.075–2.36 mm and 0.075–4.75 mm, respectively. However, during the testing of the 0.075–4.75 mm fraction, aggregates were highly prone to blockage and unsmooth discharge, rendering the accurate measurement of flow time exceedingly difficult. Although the Chinese specification of JTG 3432-2024 optimized the testing method by strictly limiting the measurement to the 0.3–2.36 mm size fraction—thereby resolving the blockage issue—the narrow range of tested particle sizes fails to comprehensively characterize the flowability of fine aggregates across all sieve intervals. To more accurately characterized and analyzed FAA, a novel testing apparatus that evaluated angularity based on the cone penetration test (CPT) method was proposed. This apparatus optimized the angularity testing parameters across four dimensions: container diameter, cone angle, testing conditions, and the number of vibrations. This optimization effectively compensated for the limitations of the current standard, which was restricted to evaluating the 0.3–2.36 mm fraction. Furthermore, a matrix calculation evaluation method for the cone penetration of both single-size fractions and mixed gradations was established. By analyzing the behavior of fine aggregates suspended in kerosene, the study simulated their workability during the mixing, paving, and compaction processes of hot mix asphalt. Ultimately, cone penetration indices for fine aggregates of various particle size specifications were proposed, facilitating a more precise, convenient, and stable quantitative assessment of fine aggregate angularity.

With the increase in service life of transportation infrastructure, highway crack repair materials have become a critical factor restricting road maintenance quality. Therefore, in order to cope with the technical bottlenecks of insufficient high-temperature stability and poor low-temperature ductility of traditional sealants, a new chemical grafting modified asphalt sealant, maleic anhydride grafted styrene-butadiene block copolymer (MAH-g-SBS) modified asphalt sealant, was developed. Benzoyl peroxide (BPO) was used as the initiator to generate MAH-g-SBS by maleic anhydride (MAH) grafting, modifying styrene-butadiene block copolymer (SBS). Through the coupling of completely randomized design and orthogonal experimental design, a MAH-g-SBS grafting rate prediction model was obtained by multiple nonlinear regression analysis, which considers the effects of reaction time, initiator dosage, reaction monomer dosage, and reaction temperature. Meanwhile, the significance of factors on grafting rate was clarified by the analysis of variance (ANOVA) and the prediction model validity was verified by error analysis. The prediction model and test data were both considered, and the maximum grafting rate was 20%. Simultaneously, by combining Fourier transform infrared spectroscopy (FTIR), the modification mechanism was revealed through the relationship between the carbonyl characteristic peak intensity and the road performance of the material. Subsequently, the road performances of MAH-g-SBS modified asphalt sealants with different grafting rates were studied by a series of laboratory tests and it was found that with the increase of grafting rate, the ductility, viscosity, and resilience recovery significantly increased and the softening point first decreased and then increased, but the cone penetration decreased. Meanwhile, based on the gray relational analysis, the grafting rate had the most significant impact on ductility and the least impact on cone penetration.

The presence of clay in aggregate is frequently associated with the deterioration of concrete properties. The objective of this study was to investigate the effects of varying clay contents on the mechanical properties, freeze-thaw resistance, permeability and water absorption behavior of concrete. Additionally, the differences in the permeability, and water absorption behavior of the surface layer and interior of concrete were comparatively analyzed using self-designed tests. The results indicate that the presence of a minimal quantity of clay did not diminish the compressive strength and static compressive modulus of elasticity of concrete. However, it did result in a reduction in the tensile properties and durability of concrete. Furthermore, the mechanical properties, freeze-thaw resistance, and anti-permeability of concrete were significantly diminished when the clay content reached 1.6%. Furthermore, this study proposed an innovative evaluation method for dividing the water absorption behavior of concrete into three stages, which more accurately reflected the trend of water absorption behavior in concrete. It was found that the sorptivity and permeable porosity of concrete in the three stages exhibited a strong correlation. The presence of clay increased the sorptivity and permeable porosity of concrete, with the most pronounced effect observed in the initial water absorption stage. Moreover, the permeable porosity of the interior of concrete was found to be reduced in comparison to that of the surface layer of concrete at all ages with varying clay contents, with the reduction ranging from 10.7% to 14.7%. In practical engineering construction, it is recommended that the clay content be kept within reasonable limits, and the effect of the clay content on the properties of the surface layer of concrete be given greater attention.

Freeze-thaw (F-T) cycling poses a significant challenge in seasonally frozen zones, notably affecting the mechanical properties of soil, which is a critical consideration in subgrade engineering. Consequently, a series of unconfined compressive strength tests were conducted to evaluate the influence of various factors, including fiber content, fiber length, curing time, and F-T cycles on the unconfined compression strength (UCS) of fiber-reinforced cemented silty sand. In parallel, acoustic emission (AE) testing was conducted to assess the AE characteristic parameters (e.g., cumulative ring count, cumulative energy, energy, amplitude, RA, and AF) of the same material under F-T cycles, elucidating the progression of F-T-induced damage. The findings indicated that UCS initially increased and then declined as fiber content increased, with the optimal fiber content identified at 0.2%. UCS increased with prolonged curing time, while increases in fiber length and F-T cycles led to a reduction in UCS, which then stabilized after 6 to 10 cycles. Stable F-T cycles resulted in a strength loss of approximately 30% in fiber-reinforced cemented silty sand. Furthermore, AE characteristic parameters strongly correlated with the stages of damage. F-T damage was segmented into three stages using cumulative ring count and cumulative energy. An increase in cumulative ring count to 0.02 x 104 times and cumulative energy to 0.03 x 104 mvmu s marked the emergence of critical failure points. A sudden shift in AE amplitude indicated a transition in the damage stage, with an amplitude of 67 dB after 6 F-T cycles serving as an early warning of impending failure.

A basalt fiber asphalt mixture could improve the road performance of pavements and prolong the service life. The oil/asphalt absorption capacity of basalt fiber affects the road performance of asphalt mixtures to a certain extent. However, using kerosene as the medium to measure the oil absorption rate of bundle fibers by the vibration method, as the Chinese specifications recommends, is unreasonable. Therefore, the aim of this paper is to study the effect of the basalt fiber morphology on the oil absorption rate and the oil/asphalt absorption test methods suitable for asphalt mixtures with different structures (dense-graded and gap-graded), and to also explore the appropriate method to determine the oil/asphalt absorption rate of fiber to kerosene and asphalt. The results showed that the filamentous basalt fiber (FBF) was easier to disperse uniformly in asphalt than the bundled basalt fiber (BBF), and the oil absorption capacity of the FBF could more accurately characterize the actual working state of the fiber in the asphalt mixture. For the gap-graded asphalt mixture, the appropriate method to measure the fiber oil absorption rate is the combination of the vibration and centrifugation methods, while the fiber asphalt absorption rate is measured by the vibration method. For the dense-graded asphalt mixture, the combination of the extrusion and centrifugation methods are more reasonable to determine the fiber oil absorption rate, while the extrusion method is suitable for determining the fiber asphalt absorption rate. The concept of an effective fiber oil absorption rate is proposed to characterize the ability of fiber to adsorb kerosene in asphalt mixtures with different structures. A temperature of 160 °C is recommended as the test temperature to determine the fiber asphalt absorption rate. Kerosene as the asphalt absorption test medium could not directly reflect the ability of fiber to adsorb asphalt.

In cold climatic areas, bridge expansion joint concrete is susceptible to damage from freeze-thaw (F-T) cycles and chloride-salt erosion. This paper investigates the differences between the surface layer of concrete (C-S) and the interior of concrete (C-I) under various curing conditions, focusing on pore structure characteristics. The salt freeze-thaw (sF-T) resistance of the C-S and C-I was analyzed using the surface scaling, mass growth rate, and apparent chloride diffusion coefficient after one-sided sF-T cycles (Dapp′). The results indicate that the pore structure of the C-S was more intricate than that of the C-I. However, the paste structure of the C-I was denser. The fractal dimension (DF) of the C-I was lower than that of the C-S under different curing conditions, with a reduction of approximately 10 %. Additionally, it was observed that the C-I exhibited significantly higher sF-T resistance than the C-S. To obtain a more precise evaluation of the concrete's sF-T resistance, it is recommended to remove 2 mm from the edges of the specimen. Furthermore, the Dapp′ is a more reliable indicator of concrete's sF-T resistance when the F-T medium is a chloride-salt solution. The Dapp′ of the C-I decreased by 26.8 %, 33.2 %, and 49.9 % under the curing conditions of 20℃-95 %RH, 5℃-70 %RH, and 0℃-50 %RH, respectively, when using concrete specimens with 2 mm of edges removed, compared to the C-S. The study results can serve as a fundamental basis for designing and constructing of concrete for bridge expansion joints in cold climatic areas.

In seasonally frozen regions, concrete pavement is exposed to cycles of freeze-thaw and erosion from de-icing salt, which can lead to unfavorable service conditions and vulnerability to damage. This paper examines the compressive strength, flexural-tensile strength, abrasion resistance, permeability, and spacing factor of concrete, taking into account the impact of various curing conditions, de-icing salt solutions, and mass fractions on the concrete’s freeze-thaw resistance. Two test methods, the single-face method and the fast-freezing method, were used to comparatively analyze the freeze-thaw resistance of concrete. The analysis was based on the surface scaling, water absorption rate, mass loss rate, relative dynamic elastic modulus, and relative durability index. The results indicate that the presence of salt solution significantly worsened the degree of concrete damage caused by freeze-thaw cycles. The use of freeze-thaw media, specifically sodium chloride (NaCl), calcium chloride (CaCl2), and potassium acetate (KAc) at mass fractions of 5%, 4.74%, and 5%, respectively, had the greatest impact on the surface scaling of concrete. However, their effect on the water absorption rate was inconsistent. When the freeze-thaw medium was water, the concrete’s relative dynamic elastic modulus and relative durability index were 9.6% and 75.3% higher, respectively, for concrete cured in 20 °C—95% RH conditions compared to those cured in 0 °C—50% RH conditions. We propose a comprehensive relative durability index (DFw) by combining the results of two methods of freeze-thaw tests. The DFw of concrete cured in 0 °C—50% RH conditions was 83.8% lower than that of concrete cured in 20 °C—95% RH conditions when exposed to a freeze-thaw medium of 5% mass fraction NaCl solution. To evaluate the salt freeze-thaw resistance of concrete pavement, it is recommended to use surface scaling and DFw together.

Benefiting from low cost, high tensile strength, chemical stability, and great resistance to temperature, alkaline, and acids, it is a reasonable and valuable technology to use basalt fiber (BF) as an admixture to optimize building materials. So far, the challenge is still to master the engineering performance of BF-reinforced materials, especially poor subgrade soils. To this end, this paper carried out a series of unconfined compressive strength (UCS) tests, splitting tensile strength (STS) tests, and scanning environmental microscope (SEM) tests to study the mechanical properties and microstructure mechanism of BF-reinforced subgrade cemented silty sand with different fiber contents and curing times. The aims of this research were: (i) the UCS and STS of basalt fiber reinforced uncemented silty sand (BFUSM) and basalt fiber reinforced cemented silty sand (BFCSM) both increased with the increase of curing time and the strength reached the maximum value after curing for 28 days; (ii) the optimal fiber content was 0.2%, and a good linear correlation existed between UCS and STS; (iii) from the microscopic point of view, the combination of BF and cement could combine the physical action of fiber reinforcement and the chemical action of cement hydration reaction to form a fiber-cement-soil skeleton structure to improve the strength of silty sand and the improvement effect after working together was better than separately incorporated BF or cement; and (iv) the corresponding developed multiple nonlinear regression (MNLR) models which can well predict UCS and STS of BFUSM and BFCSM were established.

为了研究不同剂量SBS对改性沥青性能的影响,采用高速剪切仪制备工程中常见的 3 种SBS掺量的改性沥青,分别是3%,4%,5%.根据针入度、软化点、延度、针入度指数PI、弹性恢复率、当量软化点T800、当量脆点T1.2 及改性沥青老化后相关指标,从SBS改性剂分子结构角度及线型SBS偶联过程分析SBS改性沥青官能团对沥青感温性能、流变性能、延展性及老化对SBS改性沥青的影响.结果表明,综合分析不同掺量SBS改性剂对沥青温度敏感性、高低温性能、抗老化性能的影响,SBS改性剂掺量为5%时对沥青性能改善程度最显著.

为了将超声波检测技术应用于水泥稳定基层材料,利用非金属超声波探测仪,测定了水泥稳定生活垃圾焚烧炉渣基层混合料不同龄期、不同阶段和不同状态下的超声波波速,分析了混合料波速变化规律和波速与混合料强度的相关性,建立了波速与混合料强度的关系式,并通过建立的关系式预测混合料的强度.结果表明:随着炉渣掺量增加,混合料的波速降低,超声波波速能在一定程度上反应混合料内部的变化情况,混合料越密实则波速越高;波速变化规律与混合料强度有较好的相关性,可以用波速推算室内试验和现场检测时不同龄期基层的力学性能,对水泥稳定基层质量检测有一定的参考价值,也为评价水泥稳定基层材料性能尝试了新方法.

为探究二灰稳定建筑固废碎石基层性能,通过正交试验优选出混合料最佳配合比,改变建筑固废的掺量(0％,25％,50％和75％)以探究其对混合料强度、抗压回弹模量与抗冻性能的影响.结果表明,二灰稳定纯碎石混合料的强度、抗压回弹模量和抗冻性能均最高,掺入建筑垃圾各项性能均有所降低;随着建筑固废掺量(25％,50％和75％)的增加,抗压强度和抗压回弹模量表现出先增加后降低的趋势,当建筑固废掺量达到50％时,抗压强度和抗压回弹模量达到峰值;劈裂强度却随着建筑固废掺量的增大而增大,抗冻性能随之增加而降低,但均符合规范要求,证明二灰稳定建筑固废碎石可用作路面基层,特别是用于底基层,可协调变形,提高公路使用寿命.

A basalt fiber-reinforced asphalt mixture can improve the engineering properties of asphalt pavement and prolong the service life of the road. However, few studies have systematically examined the composition of asphalt mixtures or the optimal ratio of fiber asphalt mastic suitable for different structural types. The effects of fiber content, filler–asphalt ratio, and asphalt viscosity on the properties of fiber asphalt mastic were investigated by orthogonal experiments to explore the reinforcement effect of basalt fiber on asphalt mastic. The optimal ratio of fiber asphalt mastic suitable for gap-graded and dense-graded asphalt mixtures was obtained by the fuzzy comprehensive evaluation (FCE) method. Meanwhile, the reinforcement effects of bundled basalt fiber (BBF), flocculated basalt fiber (FBF), polyester fiber (PF), and lignin fiber (LF) on asphalt mastic were compared and analyzed based on the optimal ratio of FBF asphalt mastic. The results showed that the optimal fiber asphalt mastic ratio suitable for gap-graded and dense-graded asphalt mixtures were that fiber content, filler–asphalt ratio, and asphalt viscosity were 3%, 1.8, and 1.1 Pa·s and 2%, 1.0, and 0.7 Pa·s, respectively. Analyzing the properties of different types of fiber asphalt mastic revealed that FBF could effectively enhance the high-temperature rheological properties and low-temperature tensile properties of asphalt mastic compared with other fibers. FBF asphalt mastic improved the asphalt rutting factor by more than four times. The tensile fracture energy of fiber asphalt mastic was more than three times that of the corresponding asphalt. The reinforcement effect of BBF was poor; it was recommended to be broken up before use.

In the seasonal frozen regions, the bridge expansion joint concrete (BEJC) is susceptible to damage during its service life, not only from vehicular loads but also from chloride salt erosion and the effects of freeze-thaw cycles. This study investigates the basic physical and mechanical properties of BEJC under different curing conditions. A rapid chloride permeability test was conducted to comparatively analyze the concrete's chloride ion penetration resistance. The microscopic crack width on the concrete bond surface is evaluated to assess the concrete bond performance under different loading durations. Additionally, the study explores the coupled effect of wheel loads and single-sided salt freeze-thaw cycles (WL-SFT) on the freeze-thaw resistance of BEJC, delving into factors such as spalling mass, water absorption rate, and pore structure characteristics (including air content, specific surface area, spacing coefficient) and connectivity. The results indicate that for specimens subjected to loading at 1-14 days and 3-14 days, the average crack widths on the bond surface are 14.36 mu m and 10.09 mu m, respectively, representing 5.27 times and 3.70 times those of unloaded specimens. The bond strength also decreases by 34.8% and 14.2%, respectively, compared to unloaded specimens. The increase in crack width leads to a reduction in bond strength, highlighting the importance of bond strength as a consideration for the actual opening time of roads in engineering projects. Furthermore, due to its smaller and more stable pore structure, the study suggests that WL-SFT almost does not damage standard curing (SC) concrete; however, it slightly disrupts the pore structure of natural curing (NC) concrete. In comparison, WL-SFT leads to the generation of more microcracks in both the surface and deeper layers of low-temperature curing (LC) concrete, resulting in the destruction of its pore structure and connectivity.

Mud powders in aggregates are often found to cause deterioration of concrete properties. Based on a study of the mechanical properties of bridge deck leveling concrete (BDLC) containing different mud powders at various ages, the effects of mud powders on concrete durability were evaluated through rapid chloride permeability testing, freeze–thaw testing, and the coupling of salt solution and a freeze–thaw test. The properties of the interfacial transition zone (ITZ) were also investigated via microhardness testing. The test results showed that mud powder reduced the compressive strength, static compressive elastic modulus, and bond strength at early stages of curing. Moreover, mud powder was found to reduce the tensile properties and durability of concrete, with clay powder causing a greater reduction than mud powder in river sands and coarse aggregate. In addition, the width of the ITZ of concrete containing mud powder was found to increase by 23.1–48.3%. A significant correlation between the ITZ and the tensile properties, as well as the durability of concrete, was also observed. Therefore, in order to improve the tensile properties and durability of BDLC in seasonally frozen regions, the content of mud powder in the aggregates should be minimized according to the different compositions of mud powders. The coupling effect of salt solution and a freeze–thaw cycle should also be taken into consideration.

In recent years, there have been more and more studies on the use of construction and demolition waste (CDW) as subgrade filler. The physical performance indexes of a single material of floor slabs waste (FSW) are studied, which meet the requirements of subgrade specification. From the perspective of construction quality control, it is proposed that when FSW is used as subgrade filler, the compaction thickness and the maximum allowable particle size should be controlled according to different layers, and the gradation of subgrade filler is evaluated by using the nonuniformity coefficient (Cu) and curvature coefficient (Cc). The compaction test of FSW shows that the maximum dry density and optimum moisture content of different gradations do not change much. The crushing value under the freeze-thaw cycle is proposed to evaluate the frost resistance of FSW. The crushing value of FSW after water absorption and frost heaving changes a little. The CBR and resilience modulus tests were carried out on the FSW such that the results show that they have a good relationship and the relevant expressions under different compaction degrees are fitted. When performing on-site compaction testing, it is proposed that the upper roadbed adopts the sand replacement method according to the different layers of the FSW subgrade and the settlement discrepancy method should be adopted for other parts. Through laboratory tests and construction field detective, the quality control requirements, road performance indexes, and design indexes of FSW materials are put forward.

现有路堤挡土墙稳定性计算方法,均先假定墙后土体破裂面的位置,按照对应的公式计算出破裂角θ,再与假定的破裂角对比以确定计算结果.当挡土墙高度H变化时,应分别采用破裂面交于荷载外侧、内侧、中部的计算公式,所得θ值在高度的某范围内不唯一或无解,造成假设不成立,无法判断破裂面的具体位置,也就无法计算挡墙的最大主动土压力.针对上述问题,本文提出将挡土墙上的车辆荷载换算为土柱时由矩形荷载改为梯形荷载,使之更接近墙后土体性质,并推导出新的破裂角计算公式.分析了梯形荷载与水平线夹角ψα的取值范围,使修改后的公式更具普遍性和适用性.通过改变路基宽度、墙背倾斜角度、边坡高度、坡率等路基参数,经过与规范计算方法对比和实际案例分析,表明采用修正后的计算公式判断破裂面的位置时具有唯一解,验证了修正后公式的正确性和合理性.

为了明确红砖建筑固废作为路基填料路用性能,通过归纳总结并结合大量的室内试验,从颗粒组成、杂物含量、CBR值等提出红砖建筑固废的技术指标;利用不均匀系数和曲率系数对红砖建筑固废路基填料的级配进行评价,并对红砖击实前后的级配进行对比分析,击实后红砖总体的粒径减小,细料增长了 61.5％,击实前后的级配由不良转变为良好;对红砖建筑固废进行击实试验.结果表明,不同级配的最大干密度和最佳含水率的变化并不大,通过CBR试验,结果为132.79％完全满足路基规范要求,且当贯入量达到5 mm左右时,红砖建筑固废的CBR值达到最大.

In order to clarify the influence of the municipal solid waste incineration bottom ash (MSWI BA) content on the pavement performance of the cement-stabilized macadam, the MSWI BA with 0%, 25%, 38% and 50% content was used instead of fine aggregates. To explore the feasibility of building pavement base with cement stabilized MSWI BA, the cement-stabilized MSWI BA mixture was prepared by mixing the MSWI BA at the mass fraction of 50%, 75% and 100% with fine crushed stuff. Subsequently, the compaction test and 7 days unconfined compression test were conducted with 4%, 5% and 6% cement dosage. The compaction test, unconfined compressive strength test, splitting strength test, compressive resilient modulus test and frost resistance tests were carried out based on the long-age samples with an optimal cement dosage of 5%. Furthermore, the unconfined compressive constitutive model was established based on the test data. Afterwards, the test road was built to measure the practical effect of MSWI BA on road construction. Meanwhile, energy-saving and emission-reduction analyses were conducted on the MSWI BA road. The results showed that under 5% cement dosage, the mechanical properties and frost resistance of the mixture with different MSWI BA content both satisfied the specification requirements; during the construction, the appropriate MSWI BA content could be selected according to the requirements of different highway grades in the specification. The established segmented constitutive model could well simulate the stress–strain relationship of the mixture in the compressive process. Using cement-stabilized MSWI BA to build the pavement base was feasible, which provided not only an important reference for the engineering design but also had positive significance for promoting carbon peaking, carbon neutrality and sustainable development of highway engineering construction.

Oil shale waste ash (OSWA) can be divided into semicoke ash (SA), power plant ash (PPA), and grinding ash (GA), which changes the properties of binding materials in varying degrees as partial replacements of cement in cement concrete. Fluidity of cement paste test is formed to reflect the compatibility between binding materials and admixture, using the mixture of cement to test compressive strength, flexural strength, and brittleness coefficient, to determine the mixing ratio of OSWA. The optimal amount of OSWA replacing cement was optimized by orthogonal test method, and the mechanical properties and frost resistance durability tests were carried out to clarify the reasonable amount and properties of OSWA replacing cement with cement concrete. The results show that appropriate admixtures should be taken into account when OSWA is used to replace cement in order to achieve the workability of cement concrete. The brittleness coefficient and crack resistance of cement concrete can be improved by adding proper PPA and GA. The oil shale cement concrete should not be used in the parts that require high frost resistance. It is feasible to replace cement with OSWA, and the fine powder type and mixing amount can be selected according to the actual project demand.

自微表处技术从美国引入我国以来,经科研人员不断研究,微表处技术得到不断突破,但玄武岩纤维微表处技术仍处于起步阶段.通过对玄武岩纤维微表处配合比设计的研究,确定在混合料中加入玄武岩纤维,可延长混合料的可拌和时间,并且不破坏其抗剪能力.以0％,0.2％,0.3％,0.4％的纤维掺量作为变量,进行拌和试验和粘聚力试验,确定在微表处中最佳玄武岩纤维掺量为0.3％.