含渣土的EPS轻质混凝土用于复合夹芯墙板芯材的研究

为提高地铁渣土资源化利用率,将其掺入膨胀聚苯乙烯(EPS)轻质混凝土中,并用此混凝土为芯材制备复合夹芯墙板,研究了浆体的流变性,并探讨了硬化EPS混凝土的抗压强度、导热系数及EPS颗粒在浆体中的面分布。结果表明:随着渣土掺量增加,浆体屈服应力增加,流动度降低;浆体塑性黏度随渣土掺量增加大幅度增加,使得EPS颗粒分布更加均匀;EPS混凝土的干密度、抗压强度与导热系数随渣土掺量增加而逐渐降低。当干渣土与水泥质量比为0.8时,EPS混凝土的干密度为857 kg/m³,抗压强度为4.16 MPa,导热系数为0.231 W·m^-1·K^-1;采用干渣土与水泥质量比为0.8的EPS混凝土制备复合夹芯墙板(硅钙板作面板),墙板粘结性能良好,面密度为81 kg/m²,抗压强度为3.75 MPa,软化系数为0.83,耐火极限大于1 h,其性能满足轻质隔墙条板国家标准要求。     

Properties of lightweight expanded polystyrene aggregate concretes containing fly ash

Lightweight concretes can be produced by replacing the normal aggregates in concrete or mortar either partially or fully, depending upon the requirements of density and strength levels. The present study covers the use of expanded polystyrene (EPS) beads as lightweight aggregate, both in concrete and mortar. The main aim of this programme is to study the mechanical properties of EPS concretes containing fly ash and compare the results with these in literature on concretes containing OPC alone as the binder. The effects of EPS aggregate on the green and hardened state characteristics of concretes containing fly ash were evaluated. The compressive strength of the EPS concretes containing fly ash show a continuous gain even up to 90 days, unlike that reported for OPC in literature. It was also found that the failure of these concretes both in compression and split tension was gradual as was observed earlier for the concretes containing plastic shredded aggregates. The stress-strain relations and the corresponding elastic modulus were also investigated.     

Mechanical and acoustic absorption properties of lightweight fly ash/slag-based geopolymer concrete with various aggregates

Acoustic absorption and thermal insulation play a key role in modern buildings to make living comfortable and energy-saving. This paper aims to study the workability, physical and mechanical properties, thermal conductivity, and acoustic absorption of modified geopolymer concrete (GPC) with various types of lightweight aggregates (LWA) such as extruded polystyrene foam beads waste (EPS), vermiculite, or lightweight expanded clay aggregate (LECA). The mixtures of geopolymer concrete have been modified by substituting for the ordinary aggregates (dolomite) by volume with various ratios of 0, 25, 50, 75, and 100% for each type of LWA. Besides, the mechanisms of specimens were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and mapping. The results illustrated that the compressive strength values range between 8.5 and 47.50 MPa. The hardened density of concrete was between 1500 and 2450 kg/m³, and thermal conductivity was between 0.45 and 1.16 W/m.K. Geopolymer concrete was considered an acoustic absorption and thermally insulating material. Geopolymer concrete was considered an acoustic absorption and thermally insulating material. EPS, vermiculite, and LECA will be beneficial for applications in lightweight geopolymer concrete due to their capability to reduce weight and excellent thermal conductivity, and the property of improving acoustic absorption. The mechanical results indicated that 25% LECA was the best compared with the ratios of other LWA and gained 35.0, 2.7, and 4.3 MPa of compressive, splitting tensile and flexural strength, respectively. It had positive workability; the thermal conductivity was 1.1 W/m.K, and hardened density was decreased to 10% compared to the control. In addition, LECA is considered the superior and suitable material for acoustic absorption compared with other aggregates.     

冲击荷载下EPS混凝土细观动态损伤分析

在冲击动力学试验基础上,利用weibull分布建立随机分布的不同EPS颗粒含量的EPS混凝土模型,通过显式有限元分析软件模拟了该材料在冲击荷载下的动态冲击响应.从EPS颗粒含量、EPS颗粒-水泥基质界面、损伤度和损伤率等方面研究了EPS混凝土的动力学特性及不同颗粒含量EPS混凝土之间的差异.研究结果表明:伴随着EPS颗粒含量和EPS颗粒界面的增加,可极大地改善材料的整体变形能力,使得材料的失效类型从准脆性破坏阶段向延性破坏阶段和挤压流动破坏阶段过渡;材料失效时的终止应变可提高数倍;损伤度显著增加;材料的损伤率峰值时间缩短至一半,且损伤率峰值随EPS含量增加而呈"驼峰"状分布.     

Preparation and characterization of three phase epoxy syntactic foam filled with carbon fiber reinforced hollow epoxy macrospheres and hollow glass microspheres

The present study focuses on the preparation and characterization of three phase epoxy syntactic foam (ESF) filled with carbon fiber reinforced hollow epoxy macrospheres (CFR‐HEMS) and hollow glass microspheres (HGMS). The ESF was produced by embedding CFR‐HEMS into a mixture of epoxy‐hardener and 30 wt% HGMS. An innovative approach and simple procedure was implemented in the preparation of CFR‐HEMS where expanded polystyrene (EPS) beads were used as initiation template. The EPS beads were coated with epoxy resin and carbon fiber using “rolling ball method,” and these coated EPS beads were later cured and post‐cured at high temperature which will shrink the EPS beads thus producing a hollow macrosphere structure. The compressive property of ESF was characterized and the mechanical model was issued. The ESF (450 kg/m³, 30.74 MPa) can withstand 2049 m water pressure and provide 550 kg/m³ buoyancy, the higher strength are due to the fiber spherical x–y network throughout the macrosphere epoxy matrix, which can give some support to the preparation of buoyancy material used in deepwater oil exploration. POLYM. COMPOS., 37:497–502, 2016. © 2014 Society of Plastics Engineers     

Optimization of fly ash content in concrete: Part I: Non-air-entrained concrete made without superplasticizer

This paper outlines the preliminary results of a research project aimed at optimizing the fly ash content in concrete. Such fly ash concrete would develop an adequate 1-day compressive strength and would be less expensive than the normal Portland cement concrete with similar 28-day compressive strength. The results show that, in a normal Portland cement concrete having a 28-day compressive strength of 40 MPa, it is possible to replace 50% of cement by a fine fly ash (∼3000 cm²/g) with a CaO content of ∼13%, yielding a concrete of similar 28-day compressive strength. This concrete can be designed to yield an early-age strength of 10 MPa and results in a cost reduction of about 20% in comparison to the control concrete. In a case of a coarser fly ash (∼2000 cm²/g) with a CaO content of ∼4%, substitution levels of cement by this ash could be from 30% to 40%. This concrete yields a 1-day compressive strength of 10 MPa and a 28-day compressive strength similar to that of the control concrete. The total cost of this concrete is about 10% lower than that of the control concrete.     

Taking into account the inclusions' size in lightweight concrete compressive strength prediction

This paper deals with the mix design and mechanical properties of very lightweight concrete (LWC) made of expanded polystyrene spheres (EPS) and very high performance matrix. To avoid the segregation of EPS spheres in the concrete, it is necessary to adjust the matrix threshold by modifying the superplasticizer dosage. Based on experimental data obtained on different EPS concrete, it is shown that the lower the inclusion size, the higher the compressive strength of the hardened concrete. An empirical model is proposed, to take into account these experimental results. Young's modulus was also measured, it was found that its evolution against strength followed usual physical models, like the well-known Hashin's sphere model, and not an empirical one. Finally, a simulation, based on criteria outlined in the paper, shows that quite new concretes can be proposed in a range of strength versus specific gravity not yet achieved.     

基于正交试验的EPS塑性混凝土配合比优化设计

膨胀聚苯乙烯(EPS)混凝土是一种新型的建筑材料,具有自重轻、保温性能好等特点,广泛运用于工程建设中.制备EPS混凝土的关键在于保障EPS颗粒均匀拌合.采用了六因素三水平的正交试验对高稠度的EPS塑性混凝土的配合比进行了优化设计,从而降低EPS颗粒上浮程度.试验因素包括水灰比、EPS体积比、砂率、外加剂Ⅰ掺量、外加剂Ⅱ掺量以及外加剂Ⅲ掺量.根据对正交试验结果的直观分析和方差分析得到了EPS塑性混凝土的各因素水平最佳组合以及流动性和抗压强度的主要影响因素分别为外加剂Ⅰ和EPS体积比,并总结了各因素与流动性和抗压强度的变化关系.     

Behaviour of lightweight expanded polystyrene concrete containing silica fume

Lightweight concrete can be produced by replacing the normal aggregate with lightweight aggregate, either partially or fully, depending upon the requirements of density and strength. The present study covers the use of expanded polystyrene (EPS) beads as lightweight aggregate both in concretes and mortars containing silica fume as a supplementary cementitious material. The main aim of this project is to study the strength and the durability performance of EPS concretes. These mixes were designed by using the efficiency of silica fume at the different percentages. The resulting concretes were seen to have densities varying from 1500 to 2000 kg/m³, with the corresponding strengths varying from 10 to 21 MPa. The rate of strength gain for these concretes shows that an increase in the percentage of silica fume increases the 7-day strength. This was observed to be about 75%, 85%, and 95% of the corresponding 28-day strength at the silica fume replacement levels of 3%, 5%, and 9%, respectively. The results of absorption, at 30 min and the final absorption, show that the EPS mixes made with sand have lower levels of absorption compared to the mixes containing normal aggregates. Further, the absorption values were seen to be decreasing with increasing cementitious content. The performance of these concretes, in terms of their chloride permeability and corrosion resistance, even at the minimal silica fume content level was observed to be very good.     

新型耐水石膏基墙体材料制备及性能研究

就石膏墙体材料的轻质化目的,运用两种不同的EPS颗粒的加入工艺,对两种工艺的耐水石膏材料的吸水率、强度等多种系数及性能开展对比研究,最终经过试验验证可知,EPS掺入最优值是1.3%,基于此石膏表观密度是839.06 kg/m~3。干燥时的抗压及抗折度是4.05和2.06 MPa,两者软化系数是0.517和0.650,对比未加EPS颗粒时提升百分比分别为20.8%和11.5%。虽然掺入ESP颗粒后要比未掺入的强度要大,但石膏耐水性获得了显著的提高,并且符合《石膏砌块》以及《建筑隔墙用轻质板条》对于石膏材料的性能要求。     

EPS颗粒对超轻水泥基复合保温材料性能的影响

聚苯乙烯泡沫塑料颗粒(EPS颗粒)作为水泥基复合保温材料的超轻骨料,对水泥基复合保温材料力学性能、热工性能影响显著。以水泥为胶凝材料,EPS颗粒、混合材、泡沫剂和改性剂、水等为主要原料,采用物理发泡工艺制备干表观密度不大于120 kg/m³的超轻水泥基复合保温材料(UCIM)。通过设计不同体积掺量的EPS颗粒,分析EPS颗粒掺量对泡沫混凝土基体孔结构、超轻水泥基复合保温材料强度和热工性能的影响规律。结果表明,适宜掺量EPS颗粒可显著提高超轻水泥基复合保温材料抗压强度和抗拉强度,并确保超轻水泥基复合保温材料具有良好的热工性能,即通过EPS颗粒与泡沫混凝土基体的协同作用,协调力学性能和热工性能,制备出高性能超轻水泥基复合保温材料。     

Strength properties of nylon- and polypropylene-fiber-reinforced concretes

The strength potential of nylon-fiber-reinforced concrete was investigated versus that of the polypropylene-fiber-reinforced concrete, at a fiber content of 0.6 kg/m³. The compressive and splitting tensile strengths and modulus of rupture (MOR) of the nylon fiber concrete improved by 6.3%, 6.7%, and 4.3%, respectively, over those of the polypropylene fiber concrete. On the impact resistance, the first-crack and failure strengths and the percentage increase in the postfirst-crack blows improved more for the nylon fiber concrete than for its polypropylene counterpart. In addition, the shrinkage crack reduction potential also improved more for the nylon-fiber-reinforced mortar. The above-listed improvements stemmed from the nylon fibers registering a higher tensile strength and possibly due to its better distribution in concrete.     

粗纤度PVA纤维混凝土力学性能试验分析

将粗纤度聚乙烯醇(PVA)纤维加入混凝土中,采用搅拌试验方法分析PVA纤维在混凝土中的分散性;对比不同纤维体积分数下PVA纤维混凝土的坍落度分析其可施工性;对比不同纤维体积分数PVA纤维混凝土的抗压、抗弯拉及劈裂抗拉强度和破坏状态来探索其综合力学性能。试验结果表明:PVA纤维在混凝土搅拌过程中分布较均匀不易结团;相对素混凝土,PVA纤维混凝土的坍落度略有下降;抗压强度无明显提高,抗弯拉及劈裂抗拉强度随着纤维体积分数增加呈二次函数增大。     

Sulphur-impregnated concrete,SIC.

The impregnation of hardened, dry specimens of Portland cement concrete with melted elemental sulphur increases the compressive strength by a factor of 2.7. The compressive strength of sulphur-impregnated concrete (SIC) with 8.4 per cent sulphur by weight is 174 MN/m² (25,300 psi). Due to the large surplus of sulphur and the low price, SIC might be a useful alternative to polymer-impregnated concrete, PIC.     

聚丙烯纤维及橡胶颗粒对透水混凝土性能的影响

以聚丙烯纤维及橡胶颗粒掺量为影响因素,通过测定透水混凝土的28 d抗压强度、抗折强度、孔隙率及透水系数等性能指标,获取聚丙烯纤维及橡胶颗粒掺量与透水混凝土力学性能及透水性能的关系.试验结果表明:粗骨料粒径为4.75~9.5 mm时,掺入橡胶颗粒和聚丙烯纤维皆会使透水混凝土的28 d抗压强度、抗折强度提高,但会使透水系数减小,透水性能下降;与掺加橡胶颗粒相比,掺加聚丙烯纤维可以更加明显地改善透水混凝土力学性能;随着掺入聚丙烯纤维以及橡胶颗粒比例的增加,透水混凝土28 d抗压强度、抗折强度性能指标上升的幅度逐渐减小,透水性能则逐渐下降.     

纳米秸秆灰对多孔混凝土路面力学性能的影响

本文主要研究了掺加纳米秸秆灰后对多孔混凝土路面性能的影响。根据抗压强度，弯曲强度和抗拉强度来测试多孔混凝土。结果表明，使用纳米秸秆灰材料极大提高了多孔混凝土路面的力学性能，其中纳米秸秆灰以10％质量分数替代水泥制备的多孔混凝土与其它比例制备的样品相比，表现出更加优异的强度；并且测试发现纳米秸秆灰多孔混凝土路面的抗压强度，弯曲强度和抗拉强度随着养护时间的增加而增加。     

混杂纤维混凝土的耐硫酸盐腐蚀性能研究

为了研究混杂纤维混凝土抗硫酸盐腐蚀性能,对聚乙烯纤维(PE)与聚丙烯粗合成纤维(HPP)混凝土进行硫酸盐干湿循环腐蚀和长期浸泡侵蚀试验,采用形貌损伤、质量损失、相对动弹性模量和抗压强度等宏观测试方法研究了混杂纤维混凝土耐硫酸盐腐蚀性能,并结合SEM微观结构测试技术分析了其腐蚀机理.结果表明:不同纤维掺量的混凝土在硫酸盐腐蚀作用下均出现了不同程度的损伤,其干湿循环的腐蚀作用较长期浸泡腐蚀混凝土的腐蚀损伤更为明显;长期浸泡腐蚀作用时,450 d素混凝土抗压强度可达到60 MPa,各纤维混凝土抗压强度均可达到70 MPa,但在干湿循环腐蚀作用下,聚乙烯纤维和聚丙烯粗合成纤维以0.8%+1.2%掺入时,混凝土抗压强度也可达到70 MPa;纤维对于混凝土内部结构应力的缓解,孔隙、通道等缺陷的分散以及纤维之间的捆绑桥联都显著的提高了混凝土抗硫酸盐腐蚀性.     

The effects of gradation and admixture on the pumice lightweight aggregate concrete

The usage of lightweight concrete, which has some advantage over ordinary concrete, has increased to a remarkable level in recent years. Many researchers have investigated the possible uses of lightweight concrete in terms of its strength, density and other mechanical and physical properties. The desired quality for lightweight concrete can be obtained through the proper selection of admixtures and proper grading of the lightweight aggregate.In this article, an experimental investigation on the production of moderate-strength lightweight concrete with pumice, according to the ACI standard, is presented. The gradation curves' (which fall within A16-C16 gradation curves, Turkish Standard Code, TS706) performances were investigated in terms of strength and density. The addition of superplasticizer and air-entraining admixtures improved the strength-to-density ratio of the hardened concrete and the workability of fresh concrete. As a result of this study, lightweight concrete blocks having a minimum compressive strength of 6.56 N/mm² and a density of 1300 kg/m³ were obtained.     

复掺高性能矿物掺合料对高强机制砂混凝土性能的影响

为定量研究S105矿粉与其他矿物掺合料共同作用对C80高强机制砂混凝土的和易性、抗压强度和干燥收缩性能的影响规律,通过试验得到不同龄期(3 d、7 d、28 d、60 d)下,S105矿粉单掺,以及掺S105矿粉的同时以不同含量的微珠、超细矿粉、硅灰分别取代水泥时,高强机制砂混凝土的坍落度、扩展度、抗压强度和干燥收缩率,并利用图表分析及拌合物实际状态对比等对其性能的变化趋势进行分析。结果表明:在一定掺量范围内复掺多种矿物掺合料,有利于提高高强机制砂混凝土的和易性和抗压强度,并显著减小其干燥收缩。在保证混凝土和易性良好的条件下,相比于单掺S105矿粉,S105矿粉与不同矿物掺合料双掺对提高混凝土的综合性能有更显著的作用。综合考虑对和易性、抗压强度和干燥收缩性能的影响,当超细矿粉取代水泥的质量分数为3%时,即水泥与S105矿粉和超细矿粉的质量比为33:11:1时,高强机制砂混凝土的性能处于较好的水平,其粘聚性和流动性都有显著改善,其3 d和60 d抗压强度分别增长3.1%和5.1%,其干燥收缩率则减小了4.0%。     

改进BP神经网络的再生粗骨料混凝土强度预测*

抗压强度作为评价再生混凝土主要性能指标之一,从四篇文献中搜集了43个抗压强度样本。基于改进的BP神经网络理论,建立了以再生粗骨料取代率、水灰比、龄期为输入,抗压强度为输出的神经网络模型,其结构形式为3-7-9-1。对该网络进行训练和学习,对并测试样本进行检测,结果表明,训练效率不仅大大提高,且而误差较小,并结合回归拟合系数,进一步表明该模型能够有效的的预测再生混凝土抗压强度值,能满足工程需要。