Cement-bonded composites from lignocellulosic wastes

A large quantity of lignocellulosic wastes is generated worldwide from various sources such as agriculture, construction, wood and furniture industries leading to environmental concerns. Use of these wastes in making cement-bonded construction materials can reduce the magnitude of the problems. However, in this effort there are various restraints like compatibility of these wastes with cement, their toxicity, and limited composite strength. This paper reviews the results of recent research into the use of these wastes in making cement-bonded composites used as building materials. The approaches like pre-treatments, use of chemical admixtures and modified manufacturing process, adopted to overcome the aforementioned drawbacks are described. The benefits and limitations of the use of such materials in building are also discussed.     

Effect of the treatment of wood shavings on the physico-mechanical characteristics of wood sand concretes

This study investigates the effect of a wood shaving treatment on the physico-mechanical characteristics of wood sand concretes. The two main objectives of this work are to improve a lightweight sand concrete and to valorise local materials and industrial wastes. Three wood shaving contents, two types of sand concretes (dune and river sand concrete) and a preliminary wood shaving treatment have been used. Sand, cement, filler, admixture and water composed the sand concrete matrix. The shaving treatment appreciably increases the mechanical strength of the studied composites without a large influence on thermal conductivity. The shrinkage of the composite is considerably reduced and the wood–matrix adherence is improved. At low wood contents, the dune sand concrete remains always slightly more insulating and less strong than the river sand concrete. At higher wood contents, the two concretes present almost similar properties.     

粉磨时间对矿物掺合料颗粒特性的影响

研究了粉磨时间对粉煤灰、矿渣和钢渣等工业废渣的颗粒特征和性能的影响.通过测试各物料在不同粉磨时间下的粒径分布、强度活性指数和微观形貌表明粉磨对各物料颗粒特征和性能的影响是不同的.这说明针对不同物料应该建立独立的、经济的粉磨制度.同时,对各物料颗粒性能进行的研究将为高性能辅助性胶凝材料级配研究提供依据.     

Utilization of Mn–Fe solid wastes from electrolytic MnO2 production in the manufacture of ceramic building products

The aim of this work is to evaluate the utilization of Mn–Fe solid wastes, originating from electrolytic manganese oxide production plants, as raw materials in the manufacturing process and on the properties of traditional ceramic building products such as bricks, roof or floor tiles. The Mn–Fe solid wastes are chemically and morphologically characterized. Subsequently, ceramic test specimens incorporating 2.5, 5, 7.5 and 10 wt.% solid wastes are made. Two different shaping technologies are used, namely compaction and extrusion. The green specimens are finally fired to different peak temperatures ranging from 950 to 1100 °C. The final products are characterized concerning important properties such as modulus of rupture, water absorption, weight loss and color. It appears that Mn–Fe solid wastes when used up to a percentage of 7.5 wt.% improve the basic properties of traditional building ceramic products. The results of this study are demonstrated by the successful pilot production of real size ceramic products.     

Critical review of recent development in fiber reinforced adobe bricks for sustainable construction

This paper presents a state-of-the-art review of research on the utilization of fibers (predominantly derived from waste materials) as reinforcement in adobe brick production. Recycling of these wastes provides sustainable construction materials and helps to protect the environment. Specimen preparation and test procedures are outlined. The effects of addition of these wastes on the physical and mechanical properties of adobe bricks as presented in the literature, are investigated. The main results for each additive are presented and discussed. It is concluded that improved adobe brick properties can be expected with the addition of combination of waste additives. The use of waste materials in the construction industry is generally of interest and useful for engineers and designers seeking sustainable solutions in construction. It is also of interest to researchers actively seeking to develop methodical approaches to quantifying, optimising and testing the performance in use of such waste material additives.     

Environment hazard mitigation of waste gypsum and chalk: Use in construction materials

The rapid urbanization and industrialization have resulted in the production of various types of solid, liquid and gaseous wastes which pose serious problems to the environment. The disposal and use of solid industrial wastes like phosphogypsum, fluorogypsum, fly ash, slag, and lime sludge, is significant in view of their availability and potential applications. The paper deals with studies on select wastes like phosphogypsum and chalk for use in value-added building materials. The engineering properties and techno-economics of materials like gypsum plasters, cementitious binders, boards/blocks, masonry cement and flooring tiles produced from phosphogypsum and lime have been detailed. The production and use of building materials from such wastes will protect the environment from degradation.     

Review of recent developments in cement composites reinforced with fibers and nanomaterials

The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites. Concrete reinforcement with fibers has a long history. Nowadays, many new fibers associated with high performance and possessing eco-environmental characteristics, such as basalt fibers and plant fibers, have received much attention from researchers. In addition, nanomaterials are considered as a core material in the modification of cement composites, specifically in the enhancement of the strength and durability of composites. This paper provides an overview of the recent research progress on cement composites reinforced with fibers and nanomaterials. The influences of fibers and nanomaterials on the fresh and hardened properties of cement composites are summarized. Moreover, future trends in the application of these fibers or of nanomaterial-reinforced cement composites are proposed.     

Concrete with recycled concrete aggregate and crushed clay bricks

In the last two decades, a variety of recycling methods for construction and demolition wastes (CDW) have been developed. For instance, as one of the major components in CDW, concrete rubble has been used to replace natural aggregate after being treated. This is known as recycled concrete aggregate (RCA). The property and use of RCA for structural or non-structural concrete have been extensively studied and numerous findings have been adopted in engineering practice to produce sustainable concrete. Concrete rubble, however, is inevitably mixed with other wastes such as crushed clay bricks (CCB). The level of inclusion varies depending on the original construction materials of demolished buildings. The differing properties of CCB from RCA will affect the mix design as well as the physical and mechanical properties of the resulting new concrete when the inclusion level exceeds a certain limit. Separating CCB from RCA presents an operational difficulty in practice and also has huge cost implications. Therefore, it is important to study the effect of CCB with various inclusion levels on the properties of fresh and hardened concrete. This paper reports on a study conducted to investigate the physical and mechanical properties of recycled concrete with high inclusion levels of RCA and CCB and to explore the potential or the limitation of this type of mixed recycled aggregate in primary concrete structures.     

Experimental study on thermal behavior of a building structure using rubberized exterior-walls

Addition of scrap-tire pieces into cementitious composites improves their thermal insulation performance. Development of such construction materials with lower thermal transmittance reusing these wastes is a challenging issue since it provides a combined solution for today's energy saving and environmental pollution concerns. In favor of this, recent European Union directives have brought quiet strict limits to reduce energy consumption and landfill disposal of solid wastes. A model room whose exteriors are fully made with scrap-tire added concrete is built here to increase its thermal protection. A standard/conventional room at identical dimensions but surrounded by ordinary concretes is also built to examine influence of scrap tire addition on room's thermal protection. Long-term thermal behaviors of these two rooms are investigated and compared under real atmospheric environments. Their indoor temperatures reveal that addition of scrap tire pieces lowers both indoor temperature variations and the effect of outdoor conditions. As an example, mean values of yearly thermal time lag are found to be 3.28 and 2.96 h, respectively for the rooms built with and without using scrap tire pieces, corresponding to nearly 11% improvement in thermal protection. Results in overall verify that scrap tire addition improves thermal protection of the room and it is a cost effective solution for people with low income and/or individuals living in rural areas.     

脱硫石膏粉煤灰砌块研制

脱硫石膏粉煤灰砌块是以火电厂的两种固体废弃物脱硫石膏和粉煤灰为主要原料的新型墙体材料,具有适合建筑物大开间、非承重灵活隔断的诸多优点。文中对这种砌块的原料配比、生产工艺、性能及经济效益等进行了研究与分析。     

Use of aggregates produced from marble quarry waste in asphalt pavements

More than 95% of asphalt pavement materials (by weight) consist of aggregates. The highway and construction industries consume a huge amount of aggregates annually causing considerable energy and environmental losses. The aggregates are usually produced from neighborhood aggregate quarries or from natural aggregate sources. As a result of the increasing demands for new aggregate quarries, the general texture of earth's surface has been steadily deteriorating, causing environmental concerns. The use of marble wastes from marble quarries as aggregates might help meet the increasing demands and slow down any detrimental effects on the environment. In this study, recycled aggregates produced from homogeneous marble and andesite quarry wastes in Afyonkarahisar–Iscehisar region were compared to two other aggregate specimens currently used in Afyonkarahisar city asphalt pavements. Los Angeles abrasion, aggregate impact value, freezing and thawing, flakiness index and Marshall stability flow tests were carried out on the aggregate specimens. The test results indicate that the physical properties of the aggregates are within specified limits and these waste materials can potentially be used as aggregates in light to medium trafficked asphalt pavement binder layers.     

陈腐生活垃圾固化体的路用性能及其重金属稳定性研究

目前，生活垃圾处理技术仍以填埋为主，而填埋处理技术又面临着选址、年处理垃圾量增加和很多填埋场填埋年限到期的问题。受循环经济启发，将陈腐5年以上的填埋场生活垃圾，加入固化剂及工业废渣进行固化处理，可以解决填埋场内陈腐垃圾的出路问题，而制成的固化体强度及耐久性还可达到路用地基材料的技术要求，同时符合环境排放要求，不会带来二次污染，文章探讨了陈腐垃圾固化体重金属的稳定性问题。     

粉煤灰的资源化利用现状与研究进展

粉煤灰是电厂排放的大宗固体废弃物 ,其资源化利用一直是世界各国政府和专家学者极为关注的问题。结合粉煤灰的性质特点 ,介绍了粉煤灰在建筑材料的资源化利用方面的一些新途径和应用现状。     

Skin wrinkling of sandwich polymer matrix composite panels subjected to fire exposure

This paper presents an analytical solution of skin wrinkling for sandwich polymer matrix composite panels in a combined thermal–mechanical condition. The thermal gradient in the transverse direction is induced by one-sided fire exposure, and the mechanical load is the in-plane compression. Due to low thermal conductivities of polymer matrix composites, the thermal gradient exists for a long period of time. The material properties of polymer matrix composites are degraded as temperature rises. These behaviors induce mechanical properties' gradients along the transverse direction. The general solution for the wrinkling load in the thermal–mechanical loading condition is investigated. The solution is characterized in terms of two non-dimensional parameters that represent material properties and dimensional lengths of the skin and the core. The wrinkling load is presented for fairly complete ranges of the two non-dimensional parameters. The wrinkling load is also derived from Winkler model for non-homogeneous materials. An example of thermal-mechanical simulation to design the wrinkling load-bearing capacity of a panel exposed to fire is given.     

Mechanics of the interface for carbon nanotube–polymer composites

Carbon nanotubes possess exceptionally superior mechanical properties like high elastic modulus and tensile strength. Hence, they are envisaged to be the ideal reinforcements for polymer composites, especially for enhancement of mechanical properties. However, the superiority of the mechanical properties of nanotubes alone does not ensure mechanically superior composites because the composite properties are strongly influenced by the mechanics that govern the nanotube–polymer interface. The structural strength characteristics of composite materials greatly depend on the mechanical load transfer from the matrix (polymer interface) to the nanotube and the strength of the interface. Hence, the knowledge and understanding of the nature and mechanics of load transfer between nanotube and polymer is critical for manufacturing of enhanced carbon nanotube-polymer composites and will enable in tailoring of the interface for specific applications or superior mechanical properties. In this paper, a review of the state of the art in mechanics of carbon nanotube-polymer composites will be discussed along with some directions for future research in this field.     

New construction material from concrete production and demolition wastes and lime production waste

New construction materials were developed and patented in Brazil, based on concrete production and demolition wastes mixed with lime production waste. The main objective of this research is to utilize these two types of industrial wastes on as large a scale as possible as a new raw materials for the production of concrete. The lime waste is characterized by a high content of SiO₂, Al₂O₃, CaCO₃ and other elements. After 90 days of aging in open air, the water absorption value of the sample mixtures was 12% and the uniaxial compression strength reached up to 33 MPa, with an average of 29 MPa. XRD and SEM analyses of the compositions reveal various reasons for the material’s increased strength, including transformation of the initial mineral mixture (lime and Portlandite) into calcium, magnesium and amorphous ferrous and crystalline carbonates (Calcite, Dolomite and Ancerite), and chemical interactions of the concrete waste with the lime component, which led to the growth of new amorphous and crystalline calcium hydrosilicates such as Tobermorite, Afwillite and the CSH mineral group. Although this research does not include an economic feasibility study, the zero cost of these novel raw materials for concrete is self-explanatory. However, the main advantage expected from these materials is the environmental conservation they afford, represented by the use of concrete production and demolition wastes and lime production waste.     

An assay on the effect of preliminary restoration tasks applied to a large TENORM wastes disposal in the south-west of Spain

A large industrial wastes disposal site, where two phosphate rock processing plants release their wastes, located close to Huelva town (SW of Spain), has been partially submitted to restoration as a preliminary step in a possible decomissioning process. Due to the high natural radioactivity contents of these wastes, this repository is considered as a radiological anomaly, being actually considered as TENORM (technically enhanced naturally occurring radioactive materials). The efficiency of this restoration from the radiological point of view according to the new European regulatory framework was evaluated in this work. The results allow to conclude that, as a consequence of the partial restoration works, the external dose rate has been drastically reduced above the repository system. Nevertheless, special attention must be paid on the occupational factor to be applied to workers on the unrestored system. The application of a dosimetric model allows the prediction of the negative effects of using certain industrial wastes as a cover system in this restoration/mitigation task.     

Effect of Temperature Exposure on the Flexural Mechanical Behavior of Two Pultruded Composites

The use of non-metallic composites at floor gratings in offshore platforms is driven by the need for increased component life in corrosive environments. As a result, these floor gratings contribute to a lower demand for maintenance and greater operational continuity. However, these composite materials have limitations when are exposed to high temperatures. The application of these floor gratings, on ships and floating offshore platforms have the requirement to retain a significant level of mechanical integrity during and after exposure to a fire. In this work, the mechanical behavior of two composites materials after being subject to a temperature rise was evaluated. One composite has an isophthalic polyester resin as matrix and the other used a phenolic resin. Before the mechanical characterization, thermogravimetric analysis was performed to determine the temperatures of beginning of the thermal degradation, and the microstructure of the composites was evaluated by digital image analysis. From the results of the thermal analysis a temperature of 250°C was chosen as the maximum one to be used, in order to evaluate the behavior of these composites in regions close to fire but not directly exposed to fire. Flexural properties of the two composites were performed by three-point bending test with 25 specimens of each composite. For the phenolic resin composite, the test specimens were manufactured with the average dimensions of 90.5 mm long, 19.5 mm large and 4.2 mm thick. The average dimensions of isophthalic composite specimens were 135.0 mm long, 25.0 mm large and 6.9 mm thick. The results show that the isophthalic resin matrix composite lost its mechanical integrity with the time of exposure to temperature, while the phenolic matrix composite maintained their properties. For example, regarding the maximum flexural stress a decrease of almost 50% was measured for the isophthalic matrix composite in comparison to only 3% for the phenolic matrix composite. However, the mechanical behavior of this composite was impaired by the presence of a high content of voids (5.7%) and of touching fibers arising from the manufacturing process.     

钢渣掺量对3D打印地聚物工作性能和早期强度影响

将多种固废协同制备地聚物用于3D打印胶凝材料,可以提高3D打印技术的可持续性,为固废处置提供新型资源化利用途径,但是关于3D打印固废地聚物的工作性能和早期强度有待研究.本文以钢渣、粉煤灰、矿渣粉三种工业固废为原料,以偏硅酸钠为激发剂,"一步法"制备可3D打印的多固废地聚物,测试不同原料配比下地聚物的流动度、凝结时间和早...     

Solid wastes generation in India and their recycling potential in building materials

Presently in India, about 960 million tonnes of solid waste is being generated annually as by-products during industrial, mining, municipal, agricultural and other processes. Of this ∼350 million tonnes are organic wastes from agricultural sources; ∼290 million tonnes are inorganic waste of industrial and mining sectors and ∼4.5 million tonnes are hazardous in nature. Advances in solid waste management resulted in alternative construction materials as a substitute to traditional materials like bricks, blocks, tiles, aggregates, ceramics, cement, lime, soil, timber and paint. To safeguard the environment, efforts are being made for recycling different wastes and utilise them in value added applications. In this paper, present status on generation and utilization of both non-hazardous and hazardous solid wastes in India, their recycling potentials and environmental implication are reported and discussed in details.