铁尾矿砂改良膨胀土填料工程特性研究

为保证膨胀土填料路用工程性质良好，选用铁尾矿砂处治膨胀土填料，并通过室内试验研究了铁尾矿砂改良膨胀土填料击实特性、膨胀特性、力学特性和水稳定性。结果表明，随掺砂率增大，铁尾矿砂改良膨胀土最大干密度逐渐提高，最佳含水率逐渐降低；随掺砂率增加，铁尾矿砂改良膨胀土膨胀性减弱，掺砂率增加10%,改良膨胀土自由膨胀率和膨胀力分别平均降低17.2%、22.2%;在掺砂率30%时，铁尾矿砂改良膨胀土力学特性和水稳定性最优，较素膨胀土水稳系数约提高16.1%。建议铁尾矿砂改良膨胀土最佳掺砂率为30%。     

铁尾矿砂力学特性及再生利用研究进展

铁尾矿砂的储量日趋增加,要减小铁尾矿坝的风险、提高铁尾矿砂的利用率,须明确铁尾矿砂的力学特性.通过对铁尾矿砂静力特性及动力特性的分析发现,尾矿砂的粒径分布是决定尾矿坝稳定及铁尾矿砂再生利用的主要因素之一,细粒含量、干密度、含水率等因素对铁尾矿砂动力特性有一定影响.再生利用铁尾矿砂的主要方式是将铁尾矿砂混凝土、改性铁尾矿砂用作工程材料,水泥、石灰、纤维是改性铁尾矿砂的主要材料.最后指出需进一步研究新型材料取代传统改性材料改善铁尾矿砂的力学特性,从而提高资源利用率.     

尾矿砂改性混凝土的强度与声发射损伤特征研究

为了研究尾矿砂改性混凝土的受压损伤特征,对4组不同磷矿尾矿砂取代率的混凝土进行了单轴压缩-声发射监测试验。根据混凝土受压损伤时所释放的声发射(AE)信号,定量探讨了材料的损伤程度,并以AE指标为基础分析了混凝土损伤演化特征。结果表明:混凝土的应力-应变曲线可分为弹性变形、塑性变形、断裂破坏和残余变形4个阶段;随着尾矿砂含量增加,混凝土的抗压强度先增加后保持稳定,尾矿砂取代率为30%(质量分数)的改性混凝土峰值抗压强度最大;由AE信号提出了损伤因子,损伤因子-应变曲线表明普通混凝土的结构损伤主要在塑性变形阶段,而尾矿砂改性混凝土的结构损伤集中在塑性变形和断裂破坏阶段;一定比例的磷矿尾矿砂有助于提高水泥砂浆的密实度,从而增强抗压强度和变形性能。这为尾矿砂改性混凝土的研究提供了重要参考。     

铜冶炼尾矿砂在污酸废水中固氟除氟的研究

介绍了某铜冶炼厂利用炉渣选铜后产生的尾矿砂对污酸废水进行除氟的试验情况,确定了最佳溶解条件和尾矿砂添加量.该冶炼厂将尾矿砂溶解于含氟污酸中,降低污酸中氟离子的腐蚀活性,并强化废水处理工序的絮凝沉降效果.试验表明:尾矿砂最佳溶解温度为50~60℃,溶解时间为1.0 h,尾矿砂最佳溶解粒径为300~400目,添加量为2.5~3.0 g/L.通过高氟污酸溶解尾矿砂,模拟现有污酸废水全流程处理工艺,中和上清液中ρ(F)在20~25 mg/L,除氟效果较为明显.     

铁尾矿砂石对混凝土抗水渗透性的影响

以铁尾矿砂和铁尾矿石分别取代天然砂和普通碎石,配制了强度等级为C30、C40、C50和C60的混凝土.研究了铁尾矿砂和铁尾矿石对混凝土抗水渗透性的影响.另外,还研究了掺入粉煤灰时,铁尾矿砂和铁尾矿石对混凝土抗水渗透性的影响.结果表明,随着铁尾矿砂取代率的增加,混凝土的相对渗透系数出现先降后升的趋势,当取代率为25％时,混凝土的抗渗性能最好;随着铁尾矿石取代率增加,混凝土的相对渗透系数出现逐渐减小的趋势,即其抗渗性能逐渐提高;随着铁尾矿砂和铁尾矿石同时取代率的增加,混凝土的相对渗透系数出现先降后升的趋势,当铁尾矿砂石取代率为50％时,混凝土的抗渗性能最好;粉煤灰的掺入使得铁尾矿砂石混凝土的渗透性出现劣化现象,与不掺粉煤灰同条件混凝土相比,铁尾矿砂混凝土的相对渗透系数增大.不论哪一种取代方式,取代率对低强度等级混凝土渗透的性影响大于对高强度等级混凝土渗透性的影响;尾矿砂取代天然砂对混凝土渗透性的影响大于尾矿石取代普通碎石;粉煤灰的掺入对尾矿石混凝土渗透性的影响大于对尾矿砂混凝土渗透性的影响.     

铁尾矿粉改良水泥土的强度与动力特性试验研究

为提高水泥改良土强度,验证尾矿粉能够起到对水泥土的增强效果,对已用水泥改良过的路基土,在尾矿粉掺入量不同的条件下,经改良后水泥土的强度特性,以及对被最佳掺量的尾矿粉改良后的水泥土,在围压和频率不同的条件下进行动力特性的试验研究,制备了不同尾矿粉掺量(0%、2%、4%、6%、8%、10%)的试验土样进行无侧限抗压强度试验和动三轴试验;试验结果表明:随着尾矿粉掺入量的增加,无侧限抗压强度先增大后减小,土的应力应变曲线先急剧增加达到峰值后逐渐趋于平缓.当尾矿粉掺量达到最佳时,分析不同围压和不同频率的条件下G/Gmax~γ、λ~γ变化规律.对于同一动剪应变幅,动剪模量比随围压的增加而增大.阻尼比随动剪应变幅的增大而增大,随围压的增大而减小.G/Gmax~γ、λ~γ关系受频率影响不太敏感,都集中于一狭小范围.该试验能够提高水泥土强度的尾矿粉最佳掺量为6%.     

三轴应力条件下泡沫轻质土压缩特性

为探究在复杂应力条件下泡沫轻质土的压缩特性,通过不固结不排水三轴压缩试验研究了三种不同湿密度的泡沫轻质土在多种围压状态下的应力-应变分布规律、抗剪强度特性和破坏形态.结果 表明,泡沫轻质土的三轴压缩变形过程可划分为弹性变形-应变硬化-压密破坏三个阶段.同一湿密度泡沫轻质土的偏应力和峰值应变随加载围压增大均呈现先增大后减小规律.提高泡沫轻质土湿密度,降低孔隙率,能够增大其粘聚力及内摩擦角,粘聚力约为同龄期无侧限抗压强度0.34倍,实测轻质土侧向压力系数与理论计算值一致.轻质土试件破坏形态与其力学强度有关,可根据最终破坏形态分为剪切破坏和压密破坏两类.     

银矿尾矿砂高强陶粒的研制

以广西凤凰银业有限公司的尾矿砂和废矿页岩为主要原料，在前期工作的基础上，经过实验室试验和生产线中试，成功生产出700～1000密度等级、筒压强度超过10MPa的高强陶粒。这为银矿的尾矿砂和废矿页岩的处理也为我国高强陶粒的生产探索了一条新路。     

水泥-铁尾矿泡沫混凝土的性能研究

研究了铁尾矿掺量对水泥-铁尾矿泡沫混凝土的干体积密度和抗压强度的影响,以及孔结构对泡沫混凝土导热系数的影响.测试了泡沫混凝土的导热系数,用显微镜和图像分析软件分析了泡沫混凝土的气孔结构,建立泡沫混凝土的抗压强度与干体积密度的关系模型,分析导热系数随孔结构的变化规律.结果表明铁尾矿取代水泥后泡沫混凝土的抗压强度降低,且其影响程度随混凝土气孔率的增大而减小.泡沫混凝土的抗压强度与干体积密度呈对数关系,与铁尾矿掺量成指数关系.泡沫混凝土密度相同时,气孔孔径越大抗压强度越高.随着气孔孔径的增大,泡沫混凝土的导热系数逐渐增大;随着孔隙率的增大,泡沫混凝土的导热系数逐渐减小;当孔隙率一定时,气孔孔径越小导热系数越小.     

尾矿制备气泡混合轻质土的力学与抗冻性能研究

以尾矿制备气泡混合轻质土,研究了湿密度和尾矿质量掺量对轻质土力学和抗冻性能的影响,并研究了尾矿对轻质土气孔结构的影响。结果表明,气泡混合轻质土的抗压强度与湿密度成正相关,与尾矿掺量成负相关。当尾矿掺量达到45%(质量分数,下同)时,湿密度为700 kg/m³和800 kg/m³的轻质土抗压强度分别为0.97 MPa和1.40 MPa,相比未掺尾矿的轻质土强度分别下降约69%和66%。尾矿制备气泡混合轻质土具有良好的抗冻性,30次冻融循环中,湿密度为700 kg/m³尾矿掺量为0%~45%的轻质土抗压强度损失率均在15%以内,且抗压强度均大于0.80 MPa,提高湿密度等级可以进一步改善轻质土的抗冻性。尾矿的掺入会导致轻质土孔隙率和平均孔径增大,孔圆度降低,相比于未掺尾矿的轻质土,当尾矿掺量达到30%时,孔隙率增大3.58%、平均孔径增大16.7%、圆度值增加7.4%。     

Development of lightweight aggregate geopolymer concrete with shale ceramsite

This paper developed a lightweight aggregate geopolymer concrete (LAGC) with shale ceramsite. 18 groups of LAGC specimens with 3 sand ratios (30%, 40% and 50%) and 6 aggregate contents (10%, 20%, 30%, 40%, 50% and 60%) were prepared. A series of static tests (dry density test and uniaxial compression test) and dynamic tests (ultrasonic pulse velocity test) were performed to achieve the dry density, compression strength and P-wave velocity. The effects of sand ratio and aggregate content on the dry density, compression strength and P-wave velocity were discussed. Two optimal mix proportions for the LAGC were proposed. The results show that the dry density and P-wave velocity increase as sand ratio increases. The compressive strength increases then decreases as sand ratio increases. In addition, the dry density and compressive strength decrease as aggregate content increases. The P-wave velocity increases as aggregate content increases. The LAGC with the sand ratio of 30% and aggregate contents of 30% reaches the dry density of 1378.0 kg/m³ and compressive strength of 18.5 MPa. The LAGC with the sand ratio of 30% and aggregate contents of 40% reaches the dry density of 1348.0 kg/m³ and compressive strength of 16.8 MPa. Both of the proportions satisfied the engineering requirements, which are recommended for the potential application in the construction.     

碱激发-碳养护对铜尾矿固化砖的作用机理研究

以细粒级铜尾矿作为主要原材料,水玻璃为激发剂,辅以少量水泥和粉煤灰,通过碱激发反应、压制成型及碳养护制备铜尾矿固化砖。采用X射线衍射、热重-差示扫描量热法、压汞法和扫描电子显微镜-能谱仪等对试样的物相组成、碳化产物、孔隙分布和微观产物形貌进行分析,探讨碱激发-碳养护对铜尾矿固化砖性能提升的影响规律。结果表明,水玻璃可以激发铜尾矿的部分胶凝活性,生成更多絮凝状C-S-H凝胶,改善铜尾矿固化砖的微观孔结构进而提升其抗压强度。碳养护的时机选择至关重要,固化砖成型后立即进行碳养护,碳化反应会与碱激发反应竞争OH^-,生成文石型和方解石型CaCO₃,导致C-S-H凝胶的生成量减少,孔隙率增大,抗压强度降低。固化砖密封养护84 h后再碳养护84 h,其7 d抗压强度可提高20.9%,碳化产物CaCO₃填充内部孔隙,有害孔和多害孔数量大幅减少,无害孔数量增加,整体结构密实程度提高,从而解决铜尾矿固化砖表面泛霜的问题。     

Effects of silica fume on cemented sand using ultrasonic pulse velocity

When the geotechnical engineering projects have to be built on weak soils, problems related to bearing capacity and settlement arise. Chemical stabilization of soil using cement is a popular and effective technique that can significantly improve workability and shear strength of soil. However, very limited studies have been conducted to reveal the effect of silica fume on the engineering properties of cement-stabilized sandy soil. For this purpose, in the present study, a series of laboratory tests including standard Proctor compaction, unconfined compression and ultrasonic pulse velocity tests were carried out on sand-cement-silica fume samples. Moreover, it has been attempted to investigate the relation between ultrasonic pulse velocity and unconfined compressive strength of cemented sand containing silica fume. The cement contents were 3, 5 and 7% and silica fume contents were 0, 0.25, 0.5 and 1% by weight of dry sand. The cylindrical specimens were prepared and cured for 3, 7, 14, 28, 42 and 56?days and tested. The results show that inclusion of silica fume to cemented sand increases maximum dry unit weight, unconfined compressive strength and ultrasonic pulse velocity while decreases optimum moisture content. In addition, according to the obtained results, acceptable correlations exist between ultrasonic pulse velocity, unconfined compressive strength and stiffness.     

Reduction of the shrinkage–swelling potential with polymer nanocomposite stabilization

This article describes the application of using polymer stabilization to create a new hydrophobic (nanocomposite) material with swollen clay. A series of tests were performed with different polymer contents to study the effect of using polypropylene as a partial soil stabilizer and a shrinkage–swelling modifier for expansive soils. The effect of the obtained clay–polymer nanocomposites on the shear strength of swelling soils was also investigated. The tests showed that the resulting nanocomposites acted as nanofiller materials and decreased both the plasticity index and permeability. The optimum moisture content and dry density decreased relatively with increasing polymer content. The polymer inclusions significantly reduced the free swelling and swelling pressure values. In addition, the produced nanocomposites reduced the volumetric shrinkage of the expansive soils and created isotropic and compressible materials. The unconfined compressive strength of the soil increased significantly with increasing polymer content. The proposed stabilized technique increased the bearing capacity under the model footing and modified the stress settlement relationship. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

硫酸铜/二硫化四甲基秋兰姆配位交联丁腈橡胶硫化胶的弱化Mullins效应

采用硫酸铜/二硫化四甲基秋兰姆(TMTD)配位交联制备了丁腈橡胶(NBR)硫化胶,对不同TMTD用量下混炼胶的硫化特性和硫化胶的力学性能及压缩模式下的弱化Mullins效应进行了研究.结果表明,二价铜离子和TMTD通过协同作用生成的[Cu(SnCNMe2)]·2+络合物与氰基配位交联形成了三维网络结构.随着TMTD用量...     

Experimental research on the dynamic compressive properties of lightweight slag based geopolymer

The present study aims at preparing lightweight slag based geopolymer (LW-SG) and studying its mechanical properties under dynamic and quasi-static loads. Firstly, three LW-SG with different densities were prepared by replacing the slag with expanded perlite (EP). Secondly, the density, wave velocity and pore structure of LW-SG with different EP contents were tested. Thirdly, the mechanical properties under quasi-static and dynamic loads were compared. Finally, the effects of the strain rate and EP content on the mechanical properties and failure modes of LW-SG were discussed. The results showed that with the EP contents increase, the dry density and longitudinal wave velocity gradually decreased, while the porosity increased. In addition, the quasi-static compressive strength and elastic modulus of LW-SG increased with curing ages, but decreased with EP contents increased. The dynamic compressive strength, dynamic increase factor, strain energy density and damaged degree of LW-SG all showed an increasing tendency with the strain rates increase, which exhibits an obvious strain rate dependence. Under the same strain rate, the dynamic compressive strength and strain energy density decreased with the EP contents increase, while the damaged degree increased with the EP contents increase.     

Prediction of combined effects of fibers and cement on the mechanical properties of sand using particle swarm optimization algorithm

In this research, a series of laboratory tests have been performed to investigate the effects of cement and polyvinyl alcohol (PVA) fiber on the performance of sand. Unconfined compression strength and compaction are also assessed in the present study. The cement contents were 0.5, 1, 2, 4, and 6% by weight of the dry sand. Fiber length and diameter were 12 and 0.1 mm, respectively, and were added at 0.0, 0.3, 0.6, and 1% by weight of dry sand. Finally, the obtained results from the experimental data with particle swarm optimization algorithm are used to generate a polynomial model for prediction unconfined compression strength, modulus of elasticity, and axial strain at peak strength. The results of the study indicate that the inclusion of PVA fiber increases the unconfined compressive strength and the peak axial strain. The elastic modulus of specimen decreased with increase in fibers. Maximum dry density of the sand–cement–fiber mixture increases with the increase in cement content and decreases with the increase in fiber content.     

矿渣微粉与珍珠岩尾矿复合对免烧陶粒性能的影响

以珍珠岩尾矿、粒化高炉矿渣微粉、水玻璃为原材料研制无熟料免烧陶粒。以水玻璃作为激发剂,探究其模数和掺量对矿渣微粉强度的影响,研究矿渣微粉与珍珠岩尾矿粉复合对陶粒筒压强度和堆积密度的影响。结果表明:当矿渣微粉、水玻璃质量比为90∶10,水玻璃最佳模数为1.06,矿渣微粉、珍珠岩尾矿质量比为90∶10时,可以使陶粒标养28 d达到筒压强度为7.50 MPa,密度等级为900 kg/m³,孔隙率为31.84%,软化系数为0.92,含泥量为2.25%,煮沸质量损失为2.84%;对陶粒表面进行防水处理后,吸水率由11.68%降到4.88%。采用陶粒配制LC30轻集料混凝土进行道路窨井周围道路基层应用,其28 d抗压强度为35.5 MPa,密度等级为1 700 kg/m³,压缩系数为0.001,应用效果良好,防止了城市道路窨井沉陷。