重复再生混凝土性能和环境影响研究

基于生命周期评价方法,考虑混凝土重复再生利用的环境影响分配,对重复再生混凝土的性能和环境影响进行研究,并基于功效系数法优化出混凝土最佳重复再生次数.研究结果表明,再生混凝土的坍落度,强度和电通量随着重复再生循环次数的增加而下降,经3次重复再生后,混凝土28d立方体抗压强度为33.3MPa,满足设计要求,而坍落度和电通量与普通混凝土相比,分别减小和增大了38.9%和85.7%;混凝土材料的生态效率随着混凝土重复再生次数的增加而提高,混凝土材料的GWP、CED和CMR的值均随着混凝土重复再生次数的增加而降低,降低幅度从高到低依次为：CMR > GWP > CED;综合考虑混凝土的坍落度,混凝土抗压强度、电通量、GWP、CED和CMR等6个指标,4种混凝土配合比情景中,混凝土总功效系数从高到低依次为：一次再生混凝土 > 二次再生混凝土 > 三次再生混凝土 > 普通混凝土.     

Waste management strategies for concrete

Recycling and reuse of waste such as building rubble, concrete lumps, etc. generated at construction and demolition sites form part of a wider, complex issue, primarily relating to improving supplies of construction material and solving problems of disposal of waste construction material. Within the framework of the sustainable development of the environment, the use of waste materials with minimum environmental impact has received much attention. The conversion of a large amount of demolished waste into an alternative resource will conserve the depleting natural resources of building materials. Demolished waste is mainly used as a non-stabilized base or sub-base in highway construction. The present paper discusses the recycling process and makes an effort to assess a safe and economic use of recycled concrete as a structural grade material for the construction industry. Extensive tests of structural properties such as compressive strength, flexural strength and split tensile strength of recycled concrete were carried out, in which cement and similarly fine aggregate were partially replaced by demolished waste to obtain recycled concrete and recycled aggregate concrete whose properties were compared with results for the conventional concrete.     

Concrete made with recycled tire rubber: Effect of alkaline activation and silica fume addition

The present work deals with the investigation of the potential use of recycled tire rubbers in cement matrices. This facilitates the development of concrete with a lesser environmental impact. Thus, it contributes to developing construction in a sustainable way. Concrete formulations were produced with the replacement of 10% sand aggregate by recycled tire rubber using conventional rubber and rubber modified with alkaline activation and silica fume addition to improve the mechanical properties. The water/cement ratio (or composition) and the testing age were used as additional variables. The concrete characterization was performed by testing the compressive strength, elastic modulus, density and microstructure (SEM). The recycled tire rubber proved to be an excellent aggregate to use in the concrete. It was observed that its compressive strength was reduced by only 14% (28 days), in comparison to the conventional concrete, reaching 48 MPa for the mixture with higher resistance. The concrete compositions were found to be lighter and a reduced interface was observed between the rubber and cement matrix after the chemical treatment. The rubberized concrete can support construction sustainability, minimize the consumption of natural resources by using an industrial residue and produce a material with special features.     

废混凝土在GRC中的再生利用探究

研究了再生砖骨料的取代率对再生骨料GRC的影响及变化规律,并进一步采用正交设计方法,研究了粉煤灰、硅灰及再生混凝土骨料对GRC的影响。结果表明:再生骨料GRC的强度随废混凝土取代率的提高先增长后下降,当废混凝土取代天然砂30%,可达到或超过天然砂GRC的力学性能;当粉煤灰取代水泥10%,同时硅灰取代水泥10%,废混凝土取代天然砂30%时,其抗折、抗压强度值最大。     

碎砖骨料再生混凝土配合比研究

用正交法试验分析了碎砖骨料混凝土的配合比，提出水灰比和碎砖骨料掺量分别是影响混凝土强度和流动性的主要因素。倡导用碎砖做混凝土骨料，保护生态环境。     

废弃混凝土在干混砂浆中的应用研究

废弃混凝土的循环再生利用已日益成为人类关注的重要话题,符合环境保护与可持续发展战略的迫切要求。利用废弃混凝土破碎产生的再生细骨料部分取代天然细骨料来配制干混砂浆。通过试验证明:在固定配合比条件下,再生骨料替代率为50%时,干混砂浆抗压强度、保水率和抗冻融性、强度损失率等均符合M5.0中保水的指标要求。     

利用再生骨料配制透水性混凝土

采用正交设计方法设计试验,从而配置再生骨料透水性混凝土。以再生骨料透水性混凝土的抗压强度、透水系数、孔隙率为主要考核指标,分别研究了水灰比、骨灰比、砂率、再生骨料粒径等因素及其不同的水平对再生骨料透水性混凝土各性能指标的影响。并对各考核指标的主要影响因素进一步细分,结果表明,再生骨料透水性混凝土的透水系数和孔隙率的主要影响因素是水灰比;抗压强度的主要影响因素是骨灰比。水灰比的变化与透水系数和孔隙率之间呈现相同的规律,都出现先上升后下降的趋势;骨灰比的变化与抗压强度之间呈现线性下降的趋势。当水灰比介于0.37～0.43之间,骨灰比介于4.0～4.5之间时,混凝土拌和物和易性较好,混凝土的强度较高,透水性较好。     

建筑垃圾再生骨料生产工艺及应用研究

采用进口移动式破碎-磁选-筛分设备,将混凝土类建筑垃圾加工成再生骨料,并掺入制备混凝土、干混砂浆、道路无机混合料。检测结果表明,再生制品性能可满足使用要求,再生骨料替代天然骨料比例可达到50%以上。     

再生混凝土力学性能研究进展

再生混凝土的应用,不仅能够减少废弃混凝土填埋导致的环境污染,而且能解决天然石料资源不足和废弃混凝土如何再利用的问题,其中,力学性能是再生混凝土研究领域的重要内容。对国内外再生混凝土力学性能的研究进展进行了总结,介绍了再生混凝土的抗压强度、抗拉强度、抗折强度、弹性模量、泊松比和应变的影响因素及其最新研究成果,并分析了目前研究的不足,以期为未来再生混凝土的研究提供新思路。     

Assessing the recycling potential of industrial wastewater to replace fresh water in concrete mixes: application of polyvinyl acetate resin wastewater

This study presents the use of industrial wastewater released from polyvinyl acetate resin manufacturing plant to totally replace the fresh water in concrete composites. Seventy-two laboratory prepared concrete composites were tested to investigate the effect of using various PVAW/C ratios of 0.30, 0.35, 0.40, and 0.45 on the slump, compressive strength, flexural strength, and dry density of the concrete mixes. Results indicated a slight to moderate increase in compressive strength and hard density values compared to those of the control concrete made with fresh water at 7 and 28 day curing. On the contrary, a reduction in the slump values of the PVAW–concrete was observed compared to the slump of the control mixes. However, the slump values increased with increasing the PVAW/C ratios. On the other hand, the waste material leaching test revealed that none of the PVAW toxic constituents was detected. The findings of this work would form basic information for recycling PVAW in concrete mixes and indicate a potential alternative for diminution the adverse effects on the environment posed by the hazardous effluent of the polyvinyl acetate resin industry.     

乌鲁木齐地区再生骨料混凝土的应用初探

再生骨料混凝土的研究和应用能解决日益发展的建筑业带来的环境问题,通过对乌鲁木齐地区建筑业进行调研,具体分析了乌鲁木齐地区废弃混凝土的现状,提出其再生骨料混凝土技术在乌鲁木齐地区推广应用中存在的问题,进行了再生骨料混凝土应用的技术经济可行性分析,并对乌鲁木齐地区再生骨料混凝土的应用提出相应对策。     

透水混凝土抗压强度尺寸效应细观数值模拟研究

针对透水混凝土抗压强度尺寸效应问题,开展透水混凝土抗压强度尺寸效应的细观数值模拟研究.假定混凝土是由骨料、砂浆及孔隙组成,采用Monte Carlo法将孔隙与骨料颗粒随机投放在砂浆基质中,建立透水混凝土试件的细观非均质力学模型,开展透水混凝土试件压缩数值实验.研究结果表明：随着混凝土试件尺寸的增加,透水混凝土的抗压强度降低,存在尺寸效应现象;由于透水混凝土材料高度的非均匀性,其尺寸效应现象比普通混凝土明显.     

Assessing the recycling potential of glass fibre reinforced plastic waste in concrete and cement composites

At present glass fibre reinforced plastic (GRP) waste recycling worldwide is very limited due to its intrinsic thermoset properties, lack of characterisation data and non availability of viable recycling and recovery routes. In the present study, efforts were made to recycle GRP waste powder and fibre in concrete and cement composites and assess its quality to comply with the British standards for use in construction applications. Results revealed that the mean compressive strength of concrete composites using 5%–50% GRP waste powder under water curing varied from 37 N/mm² to 19 N/mm². Increase in the concentration of GRP waste decreased the compressive strength. However, increase in curing duration (14–180 days) resulted in improving the compressive strength of concrete with 5% GRP application to 45.75 N/mm². Moreover, the density of concrete with 50% GRP waste was reduced by about 12% as compared to the control sample. The bending strength in terms of modules of rupture (MOR) of 12 mm thickness cement composites developed using 5% GRP waste fibre attained 16.5 N/mm². The findings of this work pave the way for further GRP waste recycling in precast construction products for use in various applications.     

多固废耦合水泥制备C30混凝土性能研究

为实现工业固废的资源化利用,研究了以钢渣、水渣和脱硫石膏为原料制备的复合胶凝材料作为掺合料替代水泥制备C30混凝土。考察复合胶凝材料的掺入量对胶材标准稠度用水量、凝结时间、混凝土性能的影响。结果表明：净浆的标准稠度用水量和凝结时间与复合胶凝材料的掺入量呈正相关;所制备混凝土的抗压强度随着复合胶凝材料替代水泥量的增加而下降,全部使用胶凝材料制备混凝土试块的28 d抗压强度达到43.5 MPa,为水泥对照组的78.3%。钢渣微粉和脱硫石膏能够促进水渣水化生成钙钒石和水化硅酸钙等水化产物,起到良好的胶结作用,使得混凝土结构致密。该复合胶凝材料可替代部分水泥,减少CO₂排放,带来巨大的经济效益和环境效益,具有广阔的市场应用前景。     

Comparing the implementation of concrete recycling in the Australian and Japanese construction industries

Environmental problems have been considered to be serious in the construction industry. Waste management pressures are pressing very hard with alarming industrial warming signals. Among the different types of construction and demolition wastes, concrete is about 81 percent of the volume of construction and demolition waste in Australia. To minimize the concrete waste generated from construction activities, recycling of concrete waste is one of the best methods to improve the environment. However, situations of concrete recycling in different countries vary considerably. Japan is a leading country in recycling concrete waste, with 100 percent recycling of the wastes that are used for new structural applications. This paper investigates the current concrete recycling situations in Australian and Japanese construction industries. A questionnaire survey and structured interviews were conducted. In comparing the current concrete recycling situations between Australia and Japan, it should be noted that major difficulties found from Australian and Japanese construction industries are on different phases of the transition to recycling of construction wastes. Therefore, it is suggested that the Australian construction industry should be: i) developing a unified policy in concrete recycling; ii) providing financial governmental support; iii) developing clear technical specifications or standards on the use of recycled aggregate for structural applications.     

垃圾焚烧炉渣特性分析及制备免烧砖技术研究

炉渣制备免烧砖的技术作为固废建材化利用的手段之一,具有广阔的应用前景.基于炉渣基本性质,本文探讨了炉渣预处理、原料配比及养护方式等工艺条件对炉渣免烧砖的抗压强度和环保性能的影响,并提出了优化的工艺条件和参数.结果表明:炉渣的热灼减率为1.2%,物相组成与天然骨料相似,但水溶性氯离子含量为GB 50010-2010《混凝土结构设计规范》标准限值的8倍,且存在重金属超标风险,需要在固液比1:3的条件下水洗3次,使得水溶性氯离子含量削减87.5%;免烧砖原料配比较养护方式对抗压强度的影响更大,不添加炉渣的普通免烧砖的最终强度为全炉渣免烧砖的2.23倍;养护方式的影响体现在高温养护初期抗压强度增长速度较自然养护更快,但最终差异在±3%以内;选取全炉渣的免烧砖进行高温养护或者炉渣河砂配比1:1的免烧砖进行自然养护可使产品最终强度达到10 MPa或20 MPa的要求,且水溶性氯离子含量最终削减90%,重金属浸出浓度削减50%~60%,可满足不同用途对砖的标准要求.研究显示,在不同抗压强度的要求下选取适当的配比与养护条件,可以达到炉渣消纳量大且能源耗费少的目的,并削减水溶性氯离子含量与重金属浸出浓度,具有环保效益.      

钢铁渣粉在混凝土中的应用研究

为提高钢铁渣综合利用率,考察了钢铁渣粉作混凝土掺合料对混凝土抗压强度、工作性及对大体积混凝土温升的影响,并介绍了应用钢铁渣粉的工程项目。试验及工程应用表明,钢铁渣粉作混凝土掺合料,在相同胶凝材料用量下可显著提高混凝土抗压强度,在保证设计强度要求下可降低胶凝材料用量。此外,钢铁渣粉作混凝土掺合料能提高混凝土的工作性及施工性能,并可能降低混凝土内部温升,是一种新型的混凝土掺合料。     

The migration and transformation of dissolved organic matter during the freezing processes of water

This study investigated the partitioning behavior of dissolved organic matter (DOM) in liquid and ice phases, as well as the changes in the optical properties and chlorine reactivity of DOM during the freezing processes of water. DOM was rejected from the ice phase and accumulated in the remaining liquid phase during water freezing. Moreover, the decrease in freezing temperature, as well as the increase in dissolved organic carbon (DOC) concentration of feed water, caused an increase in DOM captured in the ice phase. The ultraviolet-absorbing compounds, trihalomethane precursors, as well as fulvic acid- and humic acid-like fluorescent materials, were more liable to be to be rejected from the ice phase and were more easily retained in the unfrozen liquid phase during water freezing, as compared with organics (on average) that comprise DOC. In addition, it was also found a higher accumulation of these organics in the unfrozen liquid phase during water freezing at higher temperature. The freeze/thaw processes altered the quantity, optical properties, and chlorine reactivity of DOM. The decrease in ultraviolet light at 254 nm as well as the production of aromatic protein- and soluble microbial byproduct-like fluorescent materials in DOM due to freeze/thaw were consistently observed. On the other hand, the changes in DOC, trihalomethane formation potential, and fulvic acid- and humic acid-like fluorescence caused by freeze/thaw varied significantly between samples.     

The migration and transformation of dissolved organic matter during the freezing processes of water

This study investigated the partitioning behavior of dissolved organic matter(DOM) in liquid and ice phases, as well as the changes in the optical properties and chlorine reactivity of DOM during the freezing processes of water. DOM was rejected from the ice phase and accumulated in the remaining liquid phase during water freezing. Moreover, the decrease in freezing temperature, as well as the increase in dissolved organic carbon(DOC)concentration of feed water, caused an increase in DOM captured in the ice phase. The ultraviolet-absorbing compounds, trihalomethane precursors, as well as fulvic acid- and humic acid-like fluorescent materials, were more liable to be to be rejected from the ice phase and were more easily retained in the unfrozen liquid phase during water freezing, as compared with organics(on average) that comprise DOC. In addition, it was also found a higher accumulation of these organics in the unfrozen liquid phase during water freezing at higher temperature. The freeze/thaw processes altered the quantity, optical properties, and chlorine reactivity of DOM. The decrease in ultraviolet light at 254 nm as well as the production of aromatic protein- and soluble microbial byproduct-like fluorescent materials in DOM due to freeze/thaw were consistently observed. On the other hand, the changes in DOC, trihalomethane formation potential, and fulvic acid- and humic acid-like fluorescence caused by freeze/thaw varied significantly between samples.     

Resources and waste management in Turin (Italy): the role of recycled aggregates in the sustainable supply mix

The ever increasing quantity of construction and demolition waste (C&DW) in Italy is presently challenging public administrators, which strive to ensure that collection and recycling are sustainably managed and need to understand whether and to what extent recycled aggregates can complement natural aggregates in a sustainable supply mix (SSM) for the construction industry. The paper presents a research aimed at analysing energy and environmental implications of the C&DW recycling chain in the administrative territory of Provincia di Torino in Northern Italy, with 2.25 million inhabitants and yearly generation of 1.8 million tons of C&DW. A combined Geographical Information System (GIS) and Life Cycle Assessment (LCA) model was developed using site-specific data and paying particular attention to land use, transportation and avoided landfill: crucial issues for sustainable planning and management. A GIS was used to handle data and information about 89 recycling plants, including technological features, output and physical–mechanical characteristics of recycled aggregate. The LCA methodology was used to identify and quantify energy and environmental loads, under different assumptions relevant to delivery distances, quality of recycled aggregates, local availability of natural aggregates and geographical coverage of market demand. The C&DW recycling chain was proved to be eco-efficient, as avoided impacts were found to be higher than the induced impacts for 13 out of 14 environmental indicators. It was also estimated that the transportation distance of recycled aggregate should increase 2–3 times before the induced impacts outweigh the avoided impacts.