Heat transfer model for microwave hot in-place recycling of asphalt pavements

In order to solve for temperature fields in microwave heating for recycling asphalt mixtures, a two-dimensional heat transfer model for the asphalt mixtures within the heating range is built based on the theory of unsteady heat conduction. Four onedimensional heat transfer models are established for the asphalt mixtures outside the heating range, which are simplified into four half-infinite solids. The intensity of the radiation electric field is calculated through experiment by using heating water loads. It is suggested that the mathematical model of boundary conditions can be established in two ways, which are theoretical deduction and experimental reverse. The actual temperature field is achieved by fitting temperatures of different positions collected in the heating experiment. The simulant temperature field, which is solved with the Matlab PDE toolbox, is in good agreement with the actual temperature field. The results indicate that the proposed models have high precision and can be directly used to calculate the temperature distribution of asphalt pavements.

Numerical simulation analysis on multi-layer low-temperature heating method of asphalt pavement in hot in-place recycling

Asphalt mixture pavement reheating is one of the important steps in hot in-place recycling(HIR).To improve the heating speed of asphalt pavement in HIR,based on the numerical analysis model of asphalt mixture heating process,a new multi-layer low-temperature heating method(MLHM)was proposed.Considering input heat flux,the thermal capacity and thermal resistance of asphalt mixture,the heat transfer model was established based on energy conservation law.By heating the asphalt mixture in layers,it changes the situation that the heat energy can only be input from the upper surface of the asphalt mixture pavement.Through the simulation of the heating method of asphalt mixture in the existing technology,the result shows that the existing heating methods lead to serious aging or charring of the asphalt mixture.By MLHM,the upper and the bottom of the asphalt mixture are heated at the same time,and the heating temperature is lower than other heat methods,which not only reduces the heating thickness and increases the heating area of the asphalt mixture pavement,but also improves the heating speed,saves the energy resource and ensures the heating quality.Especially,by MLHM,the heating uniformity is better and speed is faster.

The Characteristics of Asphalt Mixture in the System of Full Thickness Cold In-place Recycling

A new research method was proposed（A/S method） to study the components and properties of reclained asphalt mixture（RAP）. The RAP was divided into two main parts, one was marked with A that included all the reclaimed old asphalt materials（including some parts of particle materials covered by asphalt）, the other was marked with S which mainly included works soil in the road structure. The actual working conditions were simulated by this kind of new method, and the adaption between the RAP properties, A/S, and the content of cementitious materials were studied. The research indicated that the real working condition could be simulated effectively by means of A/S method. It was also showed that high content of cement could improve the overall performance of RAP significantly, but it would have a negative effect on the properties of RAP if the types and sizes of aggregate particles in RAP mixture were too single. The optimum water content and maximum dry density could not be regarded as the primary basis to evaluate the overall performance of RAP, when S=0 in the experiments, although the maximum density of samples was bigger than that with A/S=1/1, the samples were not strong enough and they were easy to collapse, which indicated that component design of RAP played a great role in improving the overall properties of RAP and the comprehensive tests should be considered to evaluate the stability of RAP. Low frequency load in high temperature environment had the negative effect on the overall stability of RAP, and factors such as the loading state of the materials, the hydration degree of cementitious materials, and the aggregate gradation in the mixture were the determining factors for improving the overall performance of RAP.

Cold In-Place Recycling as a Sustainable Pavement Practice

Pavement rehabilitation and reconstruction methods with CIR （cold in-place recycling） are alternatives that can effectively reduce the high stresses and waste produced by conventional pavement strategies. An attempt was made to predict the performance, particularly low-temperature cracking resistance characteristics of CIR mixtures. These were prepared with the mix design procedure developed at the URI （University of Rhode Island） for the FHWA （Federal Highway Administration） to reduce wide variations in the application of CIR mixtures production. This standard was applied to RAP （reclaimed asphalt pavement） to produce CIR mixtures with CSS-Ih asphalt emulsion as the additive. By adjusting the number of gyrations of the SGC （Superpave gyratory compactor） for compaction, the field density of 130 pcf was represented accurately. To secure a base line, HMA （hot mix asphalt） samples were produced according to the Superpave volumetric mix design procedure. The specimens were tested using the IDT （indirect tensile） tester according to the procedure of AASHTO T 322 procedure at temperatures of-20, -10 and 0 ℃ （-4, 14, and 32°F, respectively）. The obtained results for the creep compliance and tensile strength were used as input data for the MEPDG （mechanistic empirical pavement design guide）. The analysis results indicated that no thermal or low-temperature cracking is expected over the entire analysis period of 20 years for both HMA and CIR mixtures. Thus, it appears that CIR is a sustainable rehabilitation technique which is also suitable for colder climates, and it is recommended to conduct further investigation of load-related distresses such as rutting and fatigue cracking.

Cement-fly Ash Stabilization of Cold In-place Recycled (CIR) Asphalt Pavement Mixtures for Road Bases or Subbases

For lack of laboratory and field performance data on stabilization of reclaimed asphalt pavement （RAP） aggregate and stabilized soil （S） for road bases and subbases construction, the influences of RAP/S ratio, cement and fly ash content, modifying agent （MA） on the compact, unconfined compressive strength, indirect tensile strength and water stability of the CIR mixtures were investigated. The experimental results showed that the maximum dry density and the optimum moisture content of the mixture changed significantly with the RAP/S ratio and cement-fly ash content. Unconfined compressive strength, indirect tensile strength and water stability were improved significantly by the addition of MA, and the water stability was improved by nearly 20% on average. Scanning electron microscopy（SEM） images indicated that MA accelerated the hydration of cement-fly ash system. Needle-like AFt and fibrous C-S-H gel were observed in the mixtures, which resulted in the cementation effect among the CIR mixture particles and a more compact microstructure. All these could be the cause of high strength of the CIR mixtures with MA.

A comprehensive comparison of different regression techniques and nature-inspired optimization algorithms to predict carbonation depth of recycled aggregate concrete

The utilization of recycled aggregates(RA)for concrete production has the potential to offer substantial environmental and economic advantages.However,RA concrete is plagued with considerable durability concerns,particularly carbonation.To advance the application of RA concrete,the establishment of a reliable model for predicting the carbonation is needed.On the one hand,concrete carbonation is a long and slow process and thus consumes a lot of time and energy to monitor.On the other hand,carbonation is influenced by many factors and is hard to predict.Regarding this,this paper proposes the use of machine learning techniques to establish accurate prediction models for the carbonation depth(CD)of RA concrete.Three types of regression techniques and meta-heuristic algorithms were employed to provide more alternative predictive tools.It was found that the best prediction performance was obtained from extreme gradient boosting-multi-universe optimizer(XGB-MVO)with R^(2) value of 0.9949 and 0.9398 for training and testing sets,respectively.XGB-MVO was used for evaluating physical laws of carbonation and it was found that the developed XGB-MVO model could provide reasonable predictions when new data were investigated.It also showed better generalization capabilities when compared with different models in the literature.Overall,this paper emphasizes the need for sustainable solutions in the construction industry to reduce its environmental impact and contribute to sustainable and low-carbon economies.

Performance of RAP in the System of Cold Inplace Recycling of Asphalt Pavement

The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.

Asphalt Pavement Cold Recycling and Basic Characteristics of RAP Materials and their application

In the developed countries significant proportion of reclaimed asphalt pavement(RAP)materials are used in the construction of pavements.Until recently,milled asphalt from old roads was sent to tip as waste.However,in recent years there has been increased use of waste materials in many road projects within the capital city and federal road network.Use of RAP materials is relatively new to Ethiopia and understanding its characteristics and related technology with all its potential environmental,economic and social benefits is important.Cold recycling is desired due to its potential economic benefit.In this study characteristics of RAP materials are assessed both from literature and laboratory investigations in order to better understand its performance and use.Questionnaire survey was undertaken to identify factors that are hindering recycling of materials in pavements in Ethiopia and what is to be done to overcome these factors.A policy statement is derived to support a quick start and implementation of asphalt pavement recycling in Ethiopia.Currently,a huge asphalt pavement network is being constructed and virgin construction material exploration and import materials such as bitumen is costing the country a lot of money.Over USD 7 Billion worth asphalt pavement have been constructed over the last 23 years to serve the public and freight transport,which requires about USD 176 million annually for maintenance and rehabilitation works.Therefore,any saving obtained from recycling will have meaningful impact on cost saving and environment preservation.

不同栽培基料配比对大球盖菇生长的影响

为研究利用农业废弃物栽培大球盖菇的可行性,以农作物秸秆、废菌包、牛粪等废弃物为主要原料,设置9种不同基料配方栽培大球盖菇,分析比较供试配方栽培的大球盖菇菌丝生长情况、产量及经济效益。结果表明,D_(3)、D_(4)、D_(8)处理的菌丝生长较好、出菇快、产量高、经济效益好。综合分析,在生产中推荐“玉米秸秆+谷壳+玉米芯+废弃菌包+牛粪”的基料配比组合,可以实现经济效益最大化。

废旧棉/纳米纤维素自增强复合纸的制备与性能

针对机械开松回收后产生的废旧棉短纤维存在力学性能差且难以再利用的问题,将部分回收的废旧棉短纤维在2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)/NaBr/NaClO体系中氧化,制备成纳米纤维素(CNF),然后将不同质量分数的CNF悬浮液和回收的废旧棉短纤维充分混合制备全纤维素纸浆,最后通过湿法成网和热压技术形成全纤维素纤维自增强复合纸(CCP),并探究其形貌、力学性能以及增强机制。结果表明:当CNF质量分数增加至5%时,CCP中的氢键含量增加,CNF和棉短纤维之间形成了广泛的氢键交联,促成CCP形成了致密的结构,其拉伸断裂强度达到84.72 MPa。此外,采用不脱色废旧棉短纤维制备的CCP可加工为包装纸袋使用。

电石生产中直燃活性回转窑炉尾气利用优化技术

为充分回收利用自然活性回转窑炉的化学物质和热能,提出尾气利用优化技术。以某企业电石生产为背景,了解石灰炉尾气利用现状,确定电石炉尾气工艺参数,研究直燃回转式气烧石灰窑工艺,将尾气作为燃料供石灰烧结使用,考虑尾气引起的环境污染问题,设计尾气净化装置。结果表明:应用该尾气利用优化技术后,尾气中热能的回收利用率高,节约工业生产的资源投入,降低生产成本,保护生态环境,取得了良好的生态环境效益和经济效益,对电石生产有指导意义。

泡沫沥青就地冷再生基层施工技术与质量控制

依托国道307线西乌旗境内养护工程,从配合比设计、设备配置、试验段施工等方面开展了基层泡沫沥青就地冷再生施工技术与质量控制研究。成果应用于实体养护工程,保证了冷再生水稳基层工程质量。

山谷型固废填埋场筛分资源化治理精准勘查技术应用

在山谷型固废填埋场(未采取防渗措施)治理勘查中采取精准勘查技术,可为填埋场治理方案设计提供准确、可靠的设计依据。目前对于山谷型固废填埋场精准勘查技术的应用研究还很少,本文依托北京某山谷型固废填埋场治理勘查工程,重点针对筛分资源化方案设计和垃圾清挖地下水控制方案设计所需的填埋场特征参数及水文地质参数等开展了精准勘查技术应用研究,并总结了勘查技术要点。工程实践结果表明,本文提出的精准勘查技术实用性强,在类似固废填埋场勘查中具有重要的参考和借鉴价值。

组合再生混凝土及其衍生结构的应用及展望

为扩大再生混凝土的应用范围,充分发挥其经济与低碳效益,对组合再生混凝土及其衍生结构的应用进行了分析与梳理,总结了再生骨料和再生混凝土的特性,剖析了组合再生混凝土存在的问题并对未来研究进行了展望。结果表明:再生混凝土相比普通混凝土存在着强度低、弹性模量小的特点,仅依靠再生混凝土往往较难满足结构各个部位的力学性能及功能需求;通过组合再生混凝土的形式将再生混凝土与其他混凝土在构件、结构上组合,或将再生骨料与其他骨料进行组合,将满足性能要求的混凝土放在特定部位上,既环保也能充分发挥各混凝土的优势;不同混凝土间的界面剪切强度对组合再生混凝土结构的性能有着重要影响,剪切强度受到界面粗糙度、黏结剂、混凝土强度等多种因素的影响,提高界面粗糙度可以有效提高组合再生混凝土及其衍生结构的整体性和安全性;组合再生混凝土与BIM、3D打印、装配式建筑和智能材料的结合,可在实现绿色建造的同时保证结构性能。

PP模块化雨水收集回用系统的关键施工技术及控制要点研究

通过对PP模块化雨水回收利用基本原理的研究,提出了PP模块化雨水收集回用系统的关键施工技术,以及控制要点。研究结果表明:PP模块化雨水收集回用系统的关键施工项目在工期上能够极大地节省施工时间,并且后期维护简单,重新利用率高,能够带来一定的社会、生态和经济效益。

ABS聚合及分子链修复技术概述

介绍了丙烯腈-苯乙烯-丁二烯共聚物(ABS)的聚合工艺发展及市场主要产品,重点关注了废旧ABS再利用技术,微观分子级的分子链修复技术在废旧ABS再利用中使得ABS回收料的力学性能大大提高。

体外法研究不同油脂对瘤胃原虫吞噬细菌微循环的影响

【目的】研究体外培养条件下,不同油脂对瘤胃原虫吞噬细菌微循环及微生物群体的影响。【方法】3头瘤胃瘘管山羊提供瘤胃液,分别以菜籽油(A)、豆油(B)、玉米油(C)和花生油(D)为底物培养瘤胃微生物,同时设空白对照组,培养10h时用荧光标记瘤胃细菌法进行原虫吞噬细菌试验。【结果】原虫密度以对照组最高,显著高于A、B、C组(P<0.05);细菌密度以B组最高,为4.906×109cells·mL-1,显著高于对照组(P<0.05);原虫蛋白在组间差异不显著(P>0.05),细菌蛋白组以B组最高,B、C、D均高于对照组(P<0.05)。各组原虫的吞噬速率分别为:267.6(对照组)、196.2(A组)、244.4(B组)、274.4(C组)、285.4(D组)cells/(cell·h),组间差异显著(P<0.05)。吞噬细菌N的速率分别为1.445、1.059、0.320、1.482、1.541pgN·(cell·h)-1。【结论】估算每天每头山羊细菌蛋白循环量分别为121.64(对照组)、56.64(A组)、78.39(B组)、87.04(C组)和95.06(D组)mg蛋白·(d·头)-1,B组较低,仅为对照组的64.45%,且该组微生物量最大。在本试验的基础上认为4%的豆油对微循环的调控效应最好。

胜利油田回注污水处理技术现状及发展趋势

结合胜利油田污水回注处理现状,介绍了近两年来胜利油田回注污水处理中应用的新工艺、新技术,主要有:针对腐蚀性污水实施了预氧化处理技术、水质改性处理技术,实施后水质达标,沿程水质稳定;针对含聚污水实施了氮气气浮除油技术和气浮与磁粉处理结合技术,取得较好除油效果,存在问题为产生污泥量大,排污困难;针对油田回注污水中低含油难以去除难题,实施了生物接触氧化处理技术并在樊41低渗透油田工业化应用,配套金属膜精细处理,使处理后水质达到A1级标准。针对油田污水回注处理中后续存在难题,提出了下步攻关方向。

颗粒整形再生胶砂需水量和强度研究

目的系统研究整形再生胶砂的需水量和力学性能,促进整形再生骨料在建筑工程中的广泛应用.方法通过颗粒整形技术制备再生细骨料、配制再生胶砂,测试其需水量、抗折强度、抗压强度,并与简单破碎细骨料、天然砂和标准砂制备的胶砂试样进行对比.结果由于整形再生骨料表面光滑、结构缺陷少、易于紧密堆积,比简单破碎的再生骨料,配制胶砂的需水量比降低6.9%~10%;同时,颗粒整形细骨料胶砂具有较高的抗压强度,其在不同龄期时的抗压强度比简单破碎细骨料胶砂分别提高6.5%、24.2%和8.3%,其抗压强度比相对于简单破碎再生胶砂的强度比提高30.3%.结论可见颗粒整形再生胶砂在综合性能上优于简单破碎细骨料制得的再生胶砂,颗粒整形技术有望在实际工程中得以应用.