建筑废弃物再生工艺及在路基中的应用研究

在香港,所有建筑废弃物必须统一回收、分离与利用。小于50 mm的物料主要用于填土(因为含泥量高);大于50 mm的物料经破碎后,可用于道路路基工程、制砖材料,甚至混凝土结构工程;分离出来的塑料板、纤维板、木屑、纸片等废弃物则必须进行掩埋。利用破碎粘土砖取代一定量的再生混凝土集料,可配制道路基层的混合料,其级配、强度(或CBR值)均满足道路基层材料的要求。     

Quality Control of Recycled Aggregates Derived from Construction and Demolition Wastes

In 2007, over 24 million tons of Construction and Demolition (C&D) wastes were generated in Hong Kong. Since the local landfills will be saturated in about 6 years, it is important to find a viable way to reuse these waste materials as to alleviate the demand on public fill capacity. In order to tackle the problem, the Hong Kong government has set up a temporary recycling facility in Hong Kong in 2002 for producing different sizes of recycled aggregate for use in various construction materials. The Hong Kong Polytechnic University has been studying the feasible use of recycled aggregates in Hong Kong for a number of years. A substantial amount of experimental results on the properties of recycled aggregates and the effect of recycled aggregates on the properties of concrete and other construction products (e.g. concrete blocks and granular subbase) has been published. In this paper, the experience of Hong Kong in using recycled aggregates are summarized and a set of quality control guidelines proposed for governing the use of recycled aggregates in Hong Kong is introduced. The experience and guidelines may also be useful for the recycling of waste materials derived from the recent Sichuan earthquake in China.     

香港建筑废物再生骨料混凝土的研究进展

减少,回收和再利用各种废物是当今世界可持续发展的战略之一.香港的建筑工业每天都要产生大量的建筑废物,处理和管理这些建筑废物已经成为严重的社会问题和环境问题.随着经济的快速增长,国内的一些大城市中建筑废物的处理和管理同样成为主要的环境和社会问题之一.回收和再利用建筑废物,不仅可以节约处理建筑废物的土地,减少管理和处理建筑废物的成本,而且可以节约大量的自然资源.香港政府已经建立了回收和筛选建筑废物的设施.香港理工大学在回收和再利用建筑废物领域开展了近十年的研究工作,取得了一定的成果并向香港政府推荐了再生骨料回收再利用的规范.笔者介绍香港理工大学在研究建筑废物再生骨料混凝土方面取得的成果,包括建筑废物再生骨料环保砖、粉煤灰再生骨料混凝土、蒸汽养护再生骨料混凝土等.并介绍再生骨料混凝土在香港湿地公园的应用情况.这些技术成果将对回收和利用建筑废物起到促进作用.     

Hydration and properties of nano-TiO2 blended cement composites

Two types of nano-TiO₂ particles were blended into cement pastes and mortars. Their effects on the hydration and properties of the hydrated cement pastes were investigated. The addition of nano-TiO₂ powders significantly accelerated the hydration rate and promoted the hydration degree of the cementitious materials at early ages. It was demonstrated that TiO₂ was inert and stable during the cement hydration process. The total porosity of the cement pastes decreased and the pore size distribution were also altered. The acceleration of hydration rate and the change of microstructure also affected the physical and mechanical properties of the cement-based materials. The initial and final setting time was shortened and more water was required to maintain a standard consistence due to the addition of the nano-TiO₂. The compressive strength of the mortar was enhanced, practically at early ages. It is concluded that the nano-TiO₂ acted as a catalyst in the cement hydration reactions.     

重金属在废弃粉煤灰-水泥固化体系内的迁移

采用径向动态浸出实验（rDLT）研究了含废弃粉煤灰-水泥固化朋急定样品内部重金属铅、铜、锌的氢氧化物的迁移行为，发现重金属在酸溶液作用下虽然会从样品内部向外迁移，但不同重金属的迁移规律各不相同。其中铅会在靠近固液界面的区域富集而不会及时进入外界浸出液，铜的富集区域远大于铅，锌基本不会富集而被直接浸出。在固化／稳定体系中添加Ca（OH）2可以有效阻碍锌的浸出。     

ANTIMICROBIAL PROPERTIES OF LAURICIDIN IN MECHANICALLY DEBONED CHICKEN, MINCED FISH AND CHICKEN SAUSAGE

Aerobic plate counts on Plate Count Agar at 25°C were used to determine the time required to reach a microbial spoilage level of 1.0 × 10⁷ C.F.U./g, for mechanically deboned chicken meat, minced fish and chicken sausage stored at 2°C. The storage times were 5, 8 and 9 days, respectively. Addition of citric acid (0.2%), ascorbic acid (0.2%) or lauricidin (250 ppm) alone extended the shelf-life by 0–2 days. The combination of lauricidin and citric acid or lauricidin and ascorbic acid extended the time required to reach a microbial spoilage level for mechanically deboned chicken meat by as much as 7 days, minced fish by as much 4 days and chicken sausage by 8 days.     

Photocatalytic construction and building materials: From fundamentals to applications

Heterogeneous photocatalysis has been intensively studied in recent decades because it only requires photonic energy to activate the chemical conversion contrasting with conventional catalysis which needs heat for thermo-activation. Over the years, the theories for photochemical activity of photocatalyst including photo-induced redox reaction and super-hydrophilic conversion of TiO₂ itself have been established. The progress in academic research significantly promotes its practical applications, including the field of photocatalytic construction and building materials. TiO₂ modified building materials are most popular because TiO₂ has been traditionally used as a white pigment. The major applications of TiO₂ based photocatalytic building materials include environmental pollution remediation, self-cleaning and self-disinfecting. The advantage of using solar light and rainwater as driving force has opened a new domain for environmentally friendly building materials. In this paper, the basic reaction mechanisms on photocatalyst surface under the irradiation of ultraviolet and their corresponding applications in building and construction materials are reviewed. The problems faced in practical applications and the trends for future development are also discussed.     

高温条件下混凝土爆裂机理研究进展

对高温条件下混凝土爆裂的研究进行了全面综述,总结了混凝土爆裂发生的影响因素、成因机理及实验和理论研究的进展状况.提出了热开裂和孔隙水(汽)压力的耦合作用是产生混凝土爆裂和不确定性的主要原因.温升诱致混凝土爆裂是一个复杂的非线性问题,建立一个兼顾材料科学和力学的理论体系是全面理解混凝土温升爆裂的根本途径.     

防辐射混凝土研究现状、存在问题及发展趋势

核辐射存在于核电、工业、医疗等各个领域,辐射对环境和人类健康造成了极大威胁,辐射问题引起了人们的高度重视。从防辐射混凝土原材料选择、矿物掺和料对防辐射混凝土性能影响、防辐射混凝土配合比设计、防辐射混凝土长期性能等方面介绍了防辐射混凝土的研究现状,分析了防辐射混凝土发展过程中存在的问题,在对防辐射混凝土发展趋势进行深入思考的基础上,提出磨细废弃电脑屏幕(CRT)玻璃轻骨料代替重金属骨料制备防辐射混凝土的新思路。     

废弃粗粉煤灰-水泥系统固化重金属废弃物的探讨

利用强度发展、毒性浸出试验(TCLP)和动态浸出试验(DLT)等手段探讨了废弃粗粉煤灰-水泥系统固化/稳定含铅、铜和锌的重金属废弃物的可能性。研究发现废弃粗粉煤灰-水泥系统养护28d后符合固化/稳定的指标要求，而且长期效果优于细粉煤灰-水泥系统。另外试验还发现，固化/稳定系统的酸中和能力是决定样品中重金属浸出能力的主要指标。