磷石膏对水泥稳定碎石基层性能影响研究

为掌握磷石膏对水泥稳定碎石基层性能的影响,通过制备不同磷石膏用量的水泥磷石膏稳定碎石试件,并结合室内试验对其无侧限抗压强度、抗压回弹模量和抗裂性能进行研究。研究表明:随着水泥用量增加,水泥磷石膏稳定碎石7d无侧限抗压强度、抗压回弹模量和干缩应变均逐渐增加;随着磷石膏用量增加,水泥磷石膏稳定碎石7d无侧限抗压强度和抗压回弹模量呈先增加后减小趋势,在用量为6%时性能最好,干缩应变则逐渐降低,抗裂性能变好;磷石膏水化过程随龄期增长逐渐深入,故龄期越长其对水泥磷石膏稳定碎石的强度指标提高作用越明显;采用6%磷石膏取代1%水泥制备的水泥磷石膏稳定碎石强度指标和抗裂性能较好。     

超声回弹综合法在剑麻纤维珊瑚混凝土 强度检测中的应用*

为了研究剑麻纤维增强珊瑚混凝土的抗压强度回归方程,本文利用超声回弹综合法和混凝土抗压试验,通过对掺有3 kg/m3剑麻纤维的珊瑚混凝土和未掺剑麻纤维的珊瑚混凝土试件分别进行试验,分别建立该试验中剑麻纤维珊瑚混凝土的超声声速、回弹代表值与抗压强度的之间的相关关系,给出该试验中相应的强度曲线,便于实际中为与剑麻纤维珊瑚混凝土抗压强度相关的研究提供参考。     

结构类型对水泥稳定碎石性能的影响

文章对于三种不同级配类型的集料的含水泥稳定碎石的抗刷性能、收缩性能、无侧限抗压强度以及自身抗压回弹模量等进行相关的测试。最终试验的结果表明:在客观条件以及水泥剂量相同的前提下,粗、细集料的含量相对适中的水泥稳定碎石抗压回弹模量以及抗压的强度与粗集料含量明显多于细集料含量更多的水泥稳定碎石的性能明显更好;细集料的含量明显的多于粗集料的含量的水泥稳定碎石在抗压强度、劈裂强度以及抗压回弹弹量明显更大,在粗集料的含量明显的多于细集料含量的前提下水泥稳定碎石的抗压回弹模量、相关的其他强度明显更小。     

回弹法检测高性能混凝土抗压强度试验研究

通过对54块高性能混凝土立方体试块的回弹法检测及抗压强度试验,对不同龄期高性能混凝土的回弹法非破损检测技术作了研究.经过对试验数据的处理与分析,得到了不同龄期高性能混凝土抗压强度与回弹值之间关系.通过对粉煤灰、磨细矿渣外掺料高性能混凝土破损检测结果的分析,初步得出了混凝土的配合比对高性能混凝土回弹法无损检测方法的影响.     

PR PLASTS沥青混凝土路面塑性变形特性数值模拟研究

用ANSYS在粘弹性理论基础上做掺有PR PLASTS沥青混凝土路面塑性变形仿真计算,进行掺有PR PLASTS沥青混凝土的压缩回弹模量试验和蠕变试验。对两种试验数据进行回归分析,得到不同掺量和不同温度条件下PR PLASTS沥青混凝土的材料参数。利用得到的材料参数进行数值模拟计算,分析了宏观的变形特征,PR PLASTS的掺量与路面变形的关系,温度对路面变形的影响。结果表明:PR PLASTS掺量处于0.4%～0.6%时,沥青混凝土路面具有较好的抵抗路面车辙的能力,路面塑性变形与中面层的弹性模量呈指数关系;随着温度的升高,掺有PR PLASTS的沥青路面车辙变形增大幅度小于普通沥青路面。以上研究结果可为PR PLASTS沥青混凝土在沥青路面中的应用提供理论依据。     

大粒径沥青碎石材料抗压回弹模量的测定

基于《公路沥青路面设计规范》(JTC D50-2006)要求,采用大型马歇尔试件作为试验构件,对大粒径沥青碎石材料在0℃、10℃、15℃、20℃、30℃5个温度下对其抗压回弹模量进行了试验,试验表明大粒径沥青混合料具有较好的抗压性能。     

水泥稳定碎石早期损伤自愈合过程力学性能试验研究

微裂技术(Microcracking)是一种减轻半刚性基层早期开裂的新方法,指在水泥稳定材料上引入微细裂缝网络吸收自身收缩应力,从而降低早期收缩应力避免长、宽裂缝的形成,而水泥稳定碎石材料微裂缝的愈合特性以及微裂程度与愈合程度之间的关系是微裂技术的关键.通过使用振动击实仪制备微裂程度不同的试样,在不同龄期测定无侧限抗压强度、劈裂强度、抗压回弹模量,研究微裂后水泥稳定碎石材料早期损伤自愈合过程及力学强度变化规律.研究得出:综合考虑微裂作用对水泥稳定碎石材料收缩应力的释放以及材料后期的强度恢复,微裂技术的实施时间宜选在养生2d进行,且微裂程度不超过40％;微裂后水泥稳定碎石的7d无侧限抗压强度可恢复至80％以上,满足规范要求,不影响施工工期;水泥稳定碎石试样微裂后,抗压强度、劈裂强度及抗压回弹模量的下降百分率差异较大,劈裂强度下降百分率为抗压强度的1.6～1.8倍,抗压回弹模量下降百分率为抗压强度的1.4～1.6倍.     

改良粉煤灰工程力学性质的试验研究

将含钙量较高的粉煤灰与普通粉煤灰相混合,进行相关的工程力学性质试验.试验结果表明：改良粉煤灰的最佳含水量、最大干密度与高钙粉煤灰的掺加比例呈线性相关关系;改良粉煤灰的无侧限抗压强度、水稳定性能够满足路基工程的要求,且具有一定的抗拉能力,其中压实度对改良粉煤灰的劈裂强度具有显著影响;改良粉煤灰的抗压回弹模量随压实度呈线性增大,一定龄期的改良粉煤灰压缩模量明显大于散粒体粉煤灰的压缩模量.     

低水泥含量级配碎石路用性能试验研究

为研究低水泥掺量对级配碎石路用性能的影响,考虑1%、2%、3%和4%水泥掺量,进行7 d无侧限抗压强度、承载比CBR、抗压回弹模量以及温缩、干缩系数等路用性能指标试验,确定出低水泥含量级配碎石的最佳水泥掺量。结果表明:通过7 d无侧限抗压强度指标确定最佳水泥掺量为3%,抗压强度均为3.65 MPa;3%低水泥含量级配碎石承载比CBR值为435.7%;3%低水泥含量级配碎石抗压回弹模量为900.5 MPa,与普通掺量回弹模量相比,降低了26.45%,有效提高基层韧性抑制反射裂缝扩展;3%低水泥含量级配碎石与普通水泥稳定级配碎石温缩、干缩系数的发展趋势相同,但3%低水泥含量级配碎石对温度和湿度敏感性最弱。     

混合粉煤灰的工程力学性质研究

将含钙量较高的粉煤灰与普通粉煤灰混合,进行相关工程力学性质试验。试验结果表明:混合粉煤灰最佳含水量、最大干密度与高钙粉煤灰的掺加比呈线性相关;混合粉煤灰的无侧限抗压强度和水稳定性能够满足路基工程要求,并具有一定的抗拉能力,其中压实度对混合粉煤灰的劈裂强度具有显著影响;混合粉煤灰的抗压回弹模量随压实度线性增大,一定龄期的混合粉煤灰压缩模量明显大于散粒体粉煤灰的压缩模量。     

垂直振动压实SRX稳定碎石力学性能影响因素研究

为了揭示有机聚合物SRX稳定碎石(SRX-SCS)强度形成机理及影响因素,通过室内垂直振动成型试件,研究相对含水率、SRX含量、压实度与集料岩性对SRX-SCS力学性能的影响,并建立了各强度之间的关系.结果表明:SRX-SCS抗压强度、劈裂强度和回弹模量均随着相对含水率的减小而增大,且相对含水率为0时,三者均达到最大值;力学强度随着SRX含量的增加而增大;压实度在96%~100%之间,压实度每提高1%,SRX-SCS抗压强度提高4%~8%,劈裂强度提高6%~10%,回弹模量提高7%~11%;SRX石灰岩稳定碎石的抗压强度是SRX砂岩稳定碎石、SRX花岗岩稳定碎石的1.27倍、2.19倍,劈裂强度是砂岩、花岗岩的1.23倍、2.03倍,回弹模量是砂岩、花岗岩的1.21倍、2.20倍;抗压强度Rc与劈裂强度Ri之间满足Rc=16.6Ri,抗压强度Rc与回弹模量Ec之间满足Ec=118.4Rc.该成果可为SRX-SCS的路面结构与材料设计提供理论基础.     

Effect of temperature and age on the relationship between dynamic and static elastic modulus of concrete

This study investigates the effects of cement type, curing temperature, and age on the relationships between dynamic and static elastic moduli or compressive strength. Based on the investigation, new relationship equations are proposed. The impact-echo method is used to measure the resonant frequency of specimens from which the dynamic elastic modulus is calculated. Types I and V cement concrete specimens with water-cement ratios of 0.40 and 0.50 are cured isothermally at 10, 23, and 50 °C and tested at 1, 3, 7, and 28 days.Cement type and age do not have a significant influence on the relationship between dynamic and static elastic moduli, but the ratio of static to dynamic elastic modulus approaches 1 as temperature increases. The initial chord elastic modulus, which is measured at low strain level, is similar to the dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic moduli for various cement types, temperatures, and ages.     

Dynamic and Static Tests for Mechanical Properties of Fired Plastic Refractories and Other More Resilient Materials

An apparatus for loading brick-sized specimens and a sensitive deflectometer are described. For a resilient material, the dynamic test, the static shear-free transverse test, and the static shear-corrected transverse test gave the same modulus of elasticity. The resilient materials were dense firebrick, glass, steel, and plaster. The elementary shear correction was satisfactory for the correction of the deflections of transverse test specimens having length-to-depth ratios ranging from 3.2 to 7.2. The dynamic modulus of elasticity, the static secant modulus of elasticity, and the static modulus of rupture were obtained for nine brands of heat-treated plastic refractories. The load-deflection curves obtained from static tests on these materials indicated plastic deformations ranging from nil to 19% of the truly elastic deformations calculated from the results obtained by the dynamic method of test. The differences in the extensibilities calculated from the static and dynamic methods of test were equivalent to these plastic deformations. For studies of thermal spalling, the static extensibilities were preferred because they approximated the strain at rupture.     

Dynamic compressive creep behaviour of structural silicone-to-aluminum and silicone-based sealant-to-aluminum joints

This paper outlines an experimental study on the static and dynamic compressive creep behaviour of structural silicone adhesively bonded joints. The silicone adhesives are subjected to dynamic compressive loading, which is a common case for structural façade and hybrid glazing system. Typical crack propagation of adhesives, relations between compressive load (stress) and displacement (creep strain) are examined experimentally. It is shown that the test specimen with adhesives featured by lower hardness and higher elongation at break exhibit notable crack distribution concentrated in the middle of the crack surface. The compressive behaviour consists of three regions as initial elastic, nonlinear transition and post linear, in which the latter has notable strength increase with the increase of compressive deformation. The secant compressive modulus are measured based on compressive stress and creep strain relations. It is demonstrated that the joint has higher secant compressive modulus due to less crack propagation. All test joints exhibit significant degradation of strength and energy absorption, which can be well fitted in similar exponential forms with normalized cycle numbers for test joints with different adhesives.     

Rheological investigation of the influence of acrylate polymers on the modification of asphalt

The effect of ethylene, ethylene acrylate and glycidyl methacrylate (EA) terpolymer, and ethylene butyl acrylate (EBA) copolymer on asphalt modification was investigated at 4, 6 and 8% polymer concentrations. Both melt state rheology and asphalt concrete mix (ACM) were investigated. In the melt state analysis, dynamic shear rheology, storage stability, artificial ageing, and performance grading (PG) were studied. The PG grading of polymer modified asphalt (PMA) is correlated to the elastic properties of the polymers. Both resins improved the rheological properties, reduced the temperature susceptibility, showed better storage stability, and increase the upper grading (performance) temperature of the base asphalt. The two polymers showed similar ageing characteristics with little influence on flow activation energy. In asphalt concrete mix analysis, Marshall stability, stripping (durability), resilient modulus, and permanent deformation tests were performed. Polymer‐modified asphalt concrete mix (PMACM) has increased percent retained stability and the resilient modulus when compared with ACM. The elastic modulus of PMA and the resilient modulus of their ACM followed the same trend. Weak influence on water sensitivity was observed, but excellent rutting resistance was obtained for PMACM over ACM. EA (much cheaper than EBA) produced satisfactory properties of PMA and superior ACM properties when blended with the high asphaltenes Arabian asphalt. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3446–3456, 2006     

微细钢纤维对高弹性模量混凝土力学性能的影响

基于修正的Furnas堆积模型和骨料紧密堆积试验设计了一种高弹性模量混凝土,并利用微细钢纤维改善高弹性模量混凝土的韧性,研究了钢纤维体积掺量对骨料紧密堆积状态下混凝土流动性能、强度、弹性模量及弯曲韧性的影响规律。结果表明:采用紧密堆积骨料和适量微细钢纤维可以构筑高弹性模量韧性混凝土,其静弹性模量和动弹性模量最高分别可达50.15 GPa和53.23 GPa,断裂能可达5 680.45 N/m,残余弯曲韧度比从0增加到0.43;高弹性模量混凝土的流动性能随着钢纤维掺量的增加而降低,抗折强度、弹性模量及弯曲韧性则均随着钢纤维掺量的增加而增加,混凝土的抗压强度随着钢纤维掺量增加先增加后降低。在骨料紧密堆积状态下,综合考虑流动性能、力学性能和工程经济性,高弹性模量混凝土中微细钢纤维的合理掺量为0.4%(体积分数)。     

钢渣微粉生态型超高性能混凝土力学性能影响因素分析

为促进钢铁企业废渣的无害化处理与资源化利用,将钢渣制成微粉替代石英粉制备生态型超高性能混凝土(UHPC)是其再利用的有效途径之一。针对配制钢渣微粉UHPC的原材料因素影响问题,采用正交试验法对不同配合比下钢渣微粉UHPC的抗压、抗折、劈裂抗拉等强度指标及弹性模量进行测试,以分析硅灰、钢渣微粉、河砂和钢纤维四种原材料掺量对其各项性能指标的影响效果。结果表明：钢纤维体积掺量对钢渣微粉UHPC的各项力学性能影响最为显著,河砂、钢渣微粉掺量影响程度较大,硅灰掺量影响程度较小;立方体抗压强度、抗折强度、静力受压弹性模量指标下的显著性影响顺序为钢纤维>河砂>钢渣微粉>硅灰,轴心抗压强度、劈裂抗拉强度指标下的显著性影响顺序为钢纤维>钢渣微粉>河砂>硅灰;经正交试验得出最佳配合比方案,按该方案制备的钢渣微粉UHPC具有良好的工作性能与力学性能。     

磨细钢渣对混凝土力学性能和耐久性影响的研究

基于钢渣的活性效应和微集料效应研究了不同掺量钢渣对混凝土抗压强度和抗折强度的影响,通过加速碳化试验和抗冻性试验探究了钢渣混凝土的抗碳化性能和抗冻性.采用X-CT技术探究了钢渣混凝土内部的孔结构.结果表明:掺加10%钢渣混凝土的抗压强度和抗折强度最大,掺加30%钢渣混凝土的抗压强度和抗折强度最小.当碳化到56 d时,掺加30%钢渣的混凝土的碳化深度已达12.5 mm;冻融循环到180 d,掺加30%钢渣混凝土的相对动弹性模量降至88.7%.     

Shear Strength of Pressure Sensitive Adhesives and its Correlation to Mechanical Properties

Correlations between shear resistance and the mechanical properties of pressure sensitive adhesives are studied by measuring the deformation behaviour in the static and the dynamic shear test and determining the dynamic shear modulus of the adhesive. For polymers with low or moderate viscosities, the shear strain vs. time characteristics in a static shear test and, accordingly, the static shear strength, can be evaluated from the master curves of the dynamic shear modulus or the dynamic viscosity. The dynamic shear strength also can be calculated. These exact calculations cannot be applied to highly viscous or slightly crosslinked polymers. On the basis of the model experiments, empirical correlations between shear strength and the dynamic shear modulus are established which seem to be generally valid.     

持续荷载与冻融循环耦合作用下纤维混凝土损伤性能研究

为了研究纤维混凝土在持续荷载与冻融循环耦合作用下的损伤性能,开展了不同压应力水平(0、0.3、0.5)作用下的纤维混凝土冻融循环试验,研究了不同应力水平作用下试件质量损失、相对动弹性模量和抗压强度损失等参数随冻融循环次数的变化规律。结合损伤力学,以超声波波速为损伤变量,分析了冻融损伤与荷载耦合作用的变化关系,并基于Weibull分布建立了冻融损伤预测模型,推导出冻融损伤与抗压强度的演化方程。结果表明,随着冻融循环次数的增加,冻融损伤程度表现出加剧上升的现象,应力水平为0.3的耦合作用能减小纤维混凝土的冻融损伤,应力水平为0.5的耦合作用会进一步加剧纤维混凝土的冻融损伤。建立的损伤预测模型具备较高的可行性,能够较精准预测不同冻融循环次数后的损伤,推导的演化方程相关性较好,能灵活实现损伤与强度之间的转化。