Lateral earth pressure of granular backfills on retaining walls with expanded polystyrene geofoam inclusions under limited surcharge loading

Existing studies have focused on the behavior of the retaining wall equipped with expanded polystyrene(EPS)geofoam inclusions under semi-infinite surcharge loading rather than limited surcharge loading.In this paper,the failure mode and the earth pressure acting on the rigid retaining wall with EPS geofoam inclusions and granular backfills(henceforth referred to as EPS-wall),under limited surcharge loading are investigated through two-and three-dimensional model tests.The testing results show that different from the sliding of almost all the backfill in the EPS-wall under semi-infinite surcharge loading,only an approximately triangular backfill slides in the wall under limited surcharge loading.The distribution of the lateral earth pressure on the EPS-wall under limited surcharge loading is non-linear,and the distribution changes from the increase of the wall depth to the decrease with the increase of the limited surcharge loading.An approach based on the force equilibrium of a differential element is developed to predict the lateral earth pressure behind the EPS-wall subjected to limited surcharge loading,and its performance was fully validated by the three-dimensional model tests.

An Effective Green Porous Structural Adhesive for Thermal Insulating,Flame-Retardant,and Smoke-Suppressant Expandable Polystyrene Foam

To develop an efficient way to overcome the contradiction among flame retardancy,smoke suppression,and thermal insulation in expanded polystyrene(EPS)foams,which are widely used insulation materials in buildings,a novel"green"porous bio-based flame-retard ant starch(FRS)coating was designed from starch modified with phytic acid(PA)that simultaneously acts as both a flame retardant and an adhesive.This porous FRS coating has open pores,which,in combination with the closed cells formed by EPS beads,create a hierarchically porous structure in FRS-EPS that results in superior thermal insulation with a lower thermal conductivity of 27.0 mW·(m·K)^(-1).The resultant FRS-EPS foam showed extremely low heat-release rates and smoke-production release,indicating excellent fire retardancy and smoke suppression.The specific optical density was as low as 121,which was 80.6%lower than that of neat EPS,at 624.The FRS-EPS also exhibited self-extinguishing behavior in vertical burning tests and had a high limiting oxygen index(LOI)value of 35.5%.More interestingly,after being burnt with an alcohol lamp for 30 min,the top side temperature of the FRS-EPS remained at only 140℃with ignition,thereby exhibiting excellent fire resistance.Mechanism analysis confirmed the intumescent action of FRS,which forms a compact phosphorus-rich hybrid barrier,and the phosphorus-containing compounds that formed in the gas phase contributed to the excellent flame retardancy and smoke suppression of FRS-EPS.This novel porous biomass-based FRS system provides a promising strategy for fabricating polymer foams with excellent flame retardancy,smoke suppression,and thermal insulation.

Influence of expanded polystyrene size on deformation characteristics of light weight soil

Deformation characteristics of light weight soil with different EPS (expanded polystyrene) sizes were investigated by consolidation tests.The results show that the confined stress-strain relation curve is in S shape,which has a good homologous relation with e-p curve and e-lgp curve,and three types of curves reflect obvious structural characteristics of light weight soil.When cement mixed ratio and EPS volume ratio are the same for different specimens,structural strength decreases with the increase of EPS size,but compressibility indexes basically keep unchanged within the structural strength.The settlement of light weight soil can be divided into instantaneous settlement and primary consolidation settlement.It has no obvious rheology property,and 90% of total consolidation deformation can be finished in 1 min.Settlement-time relation of light weight soil can be predicted by the hyperbolic model.S-lgt curve of light weight soil is not in anti-S shape.It is proved that there is no secondary consolidation section,so consolidation coefficient cannot be obtained by time logarithm method.Structural strength and unit price decrease with the increase of EPS size,but the reducing rate of the structural strength is lower than that of the unit price,so the cost of mixed soil can be reduced by increasing the EPS size.The EPS beads with 3-5 mm in diameter are suggested to be used in the construction process,and the prescription of mixed soil can be optimized.

Effects of Vibration Technology and Polyvinyl Acetate Emulsion on Microstructure and Properties of Expanded Polystyrene Lightweight Concrete

To prevent expanded polystyrene （EPS） beads from rising up to the surface in the molding process of EPS lightweight concrete, vibration with pressure was applied and the polyvinyl acetate （PVA） emulsion was adopted to improve its mechanical properties. The mechanical properties, thermal properties and durability of EPS lightweight concrete were tested. The microstruetures of EPS lightweight concrete were observed by scanning electron microscope （SEM）. Vibration with pressure reduces the number of small cracks. The 180 d compressive strength and flexural strength increase obviously as a large amount of PVA was added. The mixed amount of PVA has no obvious influence on the thermal performance when it is not more than 10% of the cement. Vibration with pressure and surface modification of EPS beads by PVA improve the combination of EPS beads with cement stone and the mechanical properties of EPS lightweight concrete.

Impact Resistance of a Novel Expanded Polystyrene Cement-based Material

The mechanical property of a novel expanded polystyrene cement-based material （EPS-C）, which was prepared by compressing semi-dry materials molding, was investigated. The compressive behavior was analyzed by compression tests to gain the energy absorbed during failure. Performance for impact resistance was tested by a self-made device. The results figures out that the EPS-C has good toughness and can reach swain of 0.7 without failure. The stress-strain curve is quite different from that of normal EPS concrete. It can be divided into three stages and in the third stage the compressing exhibits the highest energy absorption. With the rising of cement ratio, the impact force absorption （IEA） decreases first and then increases. The impact energy absorption （IEA） increases first and then decreases. The lowest IEA and the highest lEA appear at the cement dosage from 233 g/L to 267 g/L and from 233 g/L to 300 g/L, respectively.

EPS颗粒混合轻质土的施工技术及其应用实例

EPS颗粒混合轻质土是一种轻质、高强、环保、经济的新型土工材料,但国内还未见工程应用的报道。通过在新安江电厂88—70开关站交通道路工程中的应用实践,探讨了EPS颗粒混合轻质土的施工技术,证实了该材料可以起到缩短工期和提高工程安全性的目的。

EVA改性EPS混凝土微观结构及性能研究

为了改善聚苯乙烯(EPS)轻集料混凝土中EPS颗粒与水泥砂浆界面的黏结性能,提高EPS轻集料混凝土的力学性能,采用乙烯-醋酸乙烯酯(EVA)乳液对EPS颗粒表面进行改性,并对改性前后EPS轻集料混凝土的力学性能作了对比试验,结合扫描电镜、X射线衍射和红外光谱,分析了EVA乳液对EPS轻集料混凝土性能的影响机理.结果表明:EVA改性改善了EPS轻集料混凝土的微观结构,使其内部孔洞数量减少,孔洞尺寸趋于减小;使水泥水化更为充分,水化产物组成得以优化,EPS轻集料混凝土的180 d抗压强度和抗折强度得到提高.

废弃聚苯乙烯泡沫(EPS)外墙外保温砂浆研究

通过改性,EPS表面由憎水性变为亲水性,能被新拌硅酸盐水泥浆体所润湿。以改性EPS为轻骨料,水泥为胶结材,辅以纤维和聚合物改性,可配制施工性、热工性、耐候性、抗裂性良好的保温砂浆。这种新型保温砂浆可用于外墙外保温,突破了传统保温砂浆只能作内保温的局限,已在建筑工程中大规模应用。

EPS轻质混凝土性能研究

采用类似“裹砂”工艺的预拌方法拌制发泡聚苯乙烯(EPS)轻质混凝土并测试其力学性能.结果表明:用EPS颗粒部分取代粗集料和细集料,可以制得表观密度为800-1 800 kg/m3、抗压强度达11-20 MPa的EPS轻质混凝土;微硅粉能显著改善EPS颗粒与水泥浆体的粘结性能,提高EPS轻质混凝土抗压强度,而掺入钢纤维则能显著改善其干缩性能.

基于EPS减荷措施的高填涵洞试验研究

通过大型高填方涵洞原位减荷试验,对采用EPS减荷材料下的土压力和位移进行了监测,将未减荷情况与不同厚度EPS减荷情况下的结果进行了对比分析,并采用Marc有限元分析软件对其进行了数值仿真,研究了EPS材料的减荷特性及减荷后涵洞结构相关性状的变化规律。结果表明:EPS减荷效果显著,减荷后涵洞结构受力有所改善,为工程设计与施工提供了有效的指导和参考依据。

密度和应变率对聚苯乙烯泡沫(EPS)准静态压缩力学行为的影响

分别研究了聚苯乙烯泡沫(Expanded polystyrene,简称EPS)在三种不同密度和三种不同加载速率下的无侧限单轴准静态压缩力学行为。结果表明:EPS的压缩与一般多孔材料的压缩特征相似,其应力-应变曲线也分为三阶段(弹性段、塑性屈服平台段及致密段)。并验证了聚苯乙烯泡沫(EPS)在线弹性阶段的弹性模量与其密度近似符合二次函数关系;通过对实验结果的拟合得出了EPS的密度与其屈服强度呈线性关系并给出了关系表达式。同时表明:同一密度的EPS在不同加载速率下其线弹性模量基本不变而屈服强度随加载速率的增加而显著增加,其应变率敏感度m值较大且变化显著,EPS表现出明显的应变率效应。

EPS保温砂浆研制及施工工艺

EPS保温砂浆的抗裂性、耐候性优良 ,可用于外保温 ,本文介绍它的性能和施工工艺。

EPS颗粒对混凝土的增韧效应

配制了聚苯乙烯(EPS)颗粒体积分数分别为10%,20%,30%,40%,50%的EPS混凝土,采用100分离式霍普金森压杆(SHPB)试验装置,以比能量吸收作为指标,研究了EPS颗粒对混凝土的增韧效应,探讨了EPS颗粒对混凝土的增韧机理.结果表明:冲击荷载作用下,由于应变率效应,相同体积分数的EPS混凝土冲击韧性随应变率的增加而提高,具有显著的应变率相关性;由于EPS颗粒的微结构效应,在EPS颗粒体积分数为10%～30%时,其韧性较未掺EPS颗粒的混凝土有不同程度的提高,EPS颗粒体积分数为20%时对混凝土韧性的改善效果最佳.当EPS颗粒体积分数达到40%～50%时,其韧性有所降低.

EPS泡沫冲击压缩和吸能特性试验研究

采用小直径霍普金森压杆(SHPB),对3种密度的聚苯乙烯(expanded polystyrene,EPS)泡沫进行冲击测试,得到了5种应变率下的应力-应变全曲线.为了比较EPS泡沫在冲击荷载和准静态加载下的不同响应,对EPS泡沫试样进行3种应变率下的准静态单轴压缩试验.探讨了泡沫密度、加载应变率对EPS泡沫应力-应变行为、能量吸收性能和破坏特征的影响,应用能量吸收能力、吸能效率曲线和能量吸收图评价了其在冲击荷载下的能量吸收性能.结果表明:泡沫初始密度和加载应变率对EPS泡沫的吸能与冲压特性具有较大影响.

负压消失模工艺中EPS热解产物的研究

消失模铸造工艺中EPS热解过程及热解产物的组成一直是消失模工艺研究的热点之一。采用气相色谱法对负压消失模工艺型腔中EPS热解产物样品进行了分析 ,并且考察了合金浇注温度、负压度以及涂层透气性对热解产物组成的影响。试验结果表明 ,浇注温度对EPS热解产物的组成以及EPS在型腔中的发气量有着决定性的影响 ,从而影响金属液流动前沿的形态 ;随着负压度和涂层透气性的增加 ,EPS热解产物能够更快地排出型腔 ,在高温区停留的时间减少 ,EPS发气量降低。

MPC-EPS轻质混凝土性能试验研究

以磷酸镁水泥（magnesium phosphate cement,MPC）为胶凝材料制备出了表观密度为1800-750 kg/m3的可用于结构的磷酸镁水泥-聚苯乙烯泡沫（MPC-EPS）混凝土.试验研究了MPC-EPS混凝土的力学性能、干缩性能、吸水率及抗冻融和干湿循环能力.结果表明：MPC-EPS混凝土具有较高的早期强度,且EPS掺量越大,其早期强度发展越快;与普通水泥为胶凝材料的EPS混凝土相比,MPC-EPS混凝土具有较低的干缩变形和吸水率,是一种耐久性良好的保温隔热材料.

EPS轻质节能混凝土砌块砌体抗压性能研究

可发性聚苯乙烯(简称EPS)轻质节能混凝土砌块是为替代实心粘土砖而自主研发的一种新型墙体材料,因该砌块与普通混凝土砖在材料性质和制作工艺等方面有差异,作为承重墙体砌块使用时,《砌体结构设计规范》(GB50003-2011)中砌体抗压强度计算公式不合适。为得到适用于该砌体的计算公式并使产品推广使用,特取强度等级为MU5、MU15的EPS混凝土砌块,设计8组24个受压构件,开展砌体抗压性能试验研究,并通过实验研究、理论分析、经验回归,推导得出EPS砌块砌体抗压承载力计算公式为fm1=1.182f_1^(0.407)(1+0.07f_2),EPS混凝土砌块砌体弹性模量计算公式建议采用E_1=147.1f_m(f_m)~1/2(承重砌块砌体)和E_2=175.6f_m(f_m)~1/2( 自承重砌块砌体),而泊松比的取值建议采用0.190(承重砌块砌体)和0.220(自承重砌块砌体)。

EPS木塑复合材料的制备及阻燃改性

通过模内发泡成型工艺制备了EPS/刨花木塑复合材料,并采用三聚氰胺磷酸盐对其进行了阻燃改性。进行了力学性能、燃烧性能测试,研究了刨花及三聚氰胺磷酸盐对复合材料性能的影响,并对其阻燃机理进行了分析。结果表明,向EPS中加入等量刨花,能使其极限氧指数显著提升,达到了26.3%,与EPS相比,提升了46.1%。MPP对WPC力学性能具有显著影响,当继续加入22.5份MPP时,复合材料的力学性能明显提高,冲击强度达到466.67 J/m^2,静曲强度达到了1.35 MPa,与WPC相比,冲击强度和静曲强度分别提高了191.7%、77.6%。热释放速率峰值降低且推后,在燃烧过程中,总热释放小幅降低,极限氧指数达29.7%,垂直燃烧等级达V-0级。

EPS用于膨胀土渠坡稳定的压缩与蠕变特性试验研究

聚苯乙烯塑料泡沫(EPS)用于膨胀土渠道水下坡面的混凝土衬砌板下,发挥其减载、防水和保温功能,可减小作用于衬砌板上的膨胀压力,同时能保持膨胀土的基质吸力,从而对维护渠坡稳定起到十分积极的作用。为了更深入地研究EPS在受压时的力学特性,开展了3种密度EPS无侧限的单轴压缩与蠕变试验。结果表明:EPS单轴压缩的应力-应变关系呈明显的非线性特征,据此提出了能完整描述其受压过程的本构模型;3种EPS即使在较小压缩应力的长期作用下,也会发生明显的蠕变。进一步指出了在寒区膨胀土渠坡衬砌结构应用的EPS选择中,应综合考虑EPS密度对其减载、防水和保温特性的不同影响;同时也应考虑EPS的压缩蠕变效应对于衬砌结构的影响。

接枝聚合法回收废发泡聚苯乙烯(EPS)的研究

将一定量的废发泡聚苯乙烯(EPS)溶解在苯乙烯单体中进行自由基悬浮聚合,以过氧化二苯甲酰(BPO)为引发剂,活性磷酸钙(TCP)和聚乙烯醇(PVA)为分散剂,制备了聚苯乙烯(PS)微球。在聚合油相反应液中,随着废EPS添加量的增加,反应液黏度升高,聚合反应搅拌速率和分散剂用量必须随之提高,废EPS的添加量最好不超过苯乙烯质量分数的20%。凝胶含量分析和凝胶渗透色谱(GPC)分析结果表明,聚合反应过程中,体系中发生了均聚、接枝和交联反应,生成的PS微球分子具有线型、支化和交联3种结构类型,并且随着废EPS添加量的增加,产物中凝胶含量先增加后减少;差示扫描量热仪(DSC)和热重分析仪(TGA)结果表明,聚合产物的耐热性能随着废EPS添加量的增加而稍有提高。