Key Engineering Materials Vol. 634

Abstract: The use of waste to improve sustainability of construction materials has increased in recent years. However, in Brazil no specific official standard has been issued on the solidification/stabilization (S/S) technique for construction materials. Similarly, no leaching methodology to evaluate products that include waste, under common use conditions, has been developed. As a result, both waste and products developed based on the S/S technique are assessed following the same official standard, which considers the landfill as the only final disposal condition. This study presents a leaching methodology to analyze the S/S approach in construction materials. Red ceramic sample blocks were manufactured with the addition of 0.05% Cr₂O₃. Two leaching approaches were conceived: immersion and irrigation. Tests were carried out in four 7-day cycles. Total experimental time was shorter than the period stipulated in a Dutch standard for this purpose. The results had low coefficient of variation and proved the usefulness of the technique to simulate intense and prolonged contact with a leaching agent, as in floods, and exposure to acid rain.

Abstract: Two pathways for chemical modification of wastes from an Amazon hardwood species named Cordia goeldiana were proposed in this work. Variations in reaction time (2 h or 0.5 h) and temperature (80 and 150 °C), besides reaction medium (mechanical stirring or pressurized closed system) were tested for alkali treatment. NaOH at 5% was kept for both conditions. Afterwards, bleaching with H₂O₂ and NaOH was performed, but reaction conditions were held constant for both pathways. In general, the mild alkali treatment resulted mainly in the removal of extractives and hemicelluloses from the raw sawdust. The onset temperature and crystalline index increased. On the other hand, the use of higher pressure and temperature in alkali treatment at closed system had a remarkable lignin removal and crystalline index increase without changing cellulose polymorphism as the main effects, but thermal stability became lower. Apart from mineral residues removal, bleaching had negligible effects on fiber properties, suggesting that this procedure could be avoided.

Abstract: The search for solutions that might promote the environmental preservation is a great challenge to be faced because of the increasingly depletion of natural resources that are used by society. To use more sustainable building material can be a way of reducing environmental damages and the generation of waste. Builds using earth have characteristics of sustainability and they are recommended in places where there is, already, the tradition of the use of this technique, once this is an abundant and propitious resource for edification. The adobe brick can contribute for a sustainable development in the civil construction if made of raw clay and if used in a large scale basis. In this article, there are presented recommendations for building that uses adobe brick, based on the Norm NTE E.080:2000 – Adobe from Peru and based on the building techniques that are adopted by constructors that use this material in the State of Bahia – Brazil At first we analyze the constructive processes that have been adopted by constructors from Bahia comparing to what Peruvian Norm professes and what can be found in the bibliography about this subject. In the end recommendations are made for the building of adobe brick in order to guarantee the effective protection and conservation of the brickwork made with this material and that provides safety and durability of edifications.

Abstract: . The use of bamboo as construction and raw material for producing products can be considered a feasible alternative to the abusive use of steel, concrete and oil byproducts. Its use can also reduce the pressure on the use of wood from native and planted forests. Although there are thousands of bamboo species spread about the world and Brazil itself has hundreds of native species, the use and basic knowledge of its characteristics and applications are still little known and little disseminated. This paper's main objective is to introduce the species, the management phases, the physical and mechanical characteristics and the experiences in using bamboo in design and civil construction as per the Bamboo Project implemented at UNESP, Bauru campus since 1994. The results are divided into: a) Field activities - description of the technological species of interest, production chain flows, types of preservative treatments and clump management practices for the development, adaptation and production of different species of culms; b) Lab experiments - physical and mechanical characterization of culms processed as laminated strips and as composite material (glue laminated bamboo – glubam); c) Uses in projects - experiences with natural bamboo and glubam in design, architecture and civil construction projects. In the final remarks, the study aims to demonstrate, through practical and laboratory results, the material's multi-functionality and the feasibility in using bamboo as a sustainable material.

Abstract: Among non-conventional materials available in Brazil for construction, sugar cane bagasse lignocellulosic particles and “synthetic termite saliva” are included. The utilization of such particles as reinforcement and the “synthetic termite saliva” for soil chemical stabilization in adobe production were not investigated in the literature yet. Therefore, this research aimed to evaluate the mechanical properties of adobes produced with those materials. The soil used was Red Latosol Cambisol type with clayey texture with kaolinite presence, and particle size correction for 50% sand. Bagasse sliver particles were washed with residual water of the distillation process at 45°C and air dried. Their density and chemical composition were determined. The adobes were produced with 30x15x8cm-size wood molds. The following samples were analyzed: adobes without particles (control); and adobes with bagasse incorporation at 2%, 4% and 6% based on dry mass and “synthetic termite saliva” at 1:1500 and 1:500 proportions. Aluminum sulfate solvent was applied at 1:5,000. The adobes were stored in a covered warehouse until complete drying. Compression and static bending strength were evaluated. The results showed a positive interaction between adobe components and compression strength, which was improved up to 60%. The best composition tested was 6% sugar cane bagasse and “synthetic termite saliva” at 1:500.

Abstract: A substantial part of the world building heritage has been performed by earthen building. The durability of this existing heritage and mainly of the new buildings built with earth is particularly conditioned by the erosion caused by water action, especially in countries with high levels of rainfall. This research aims to contribute to the increase of knowledge about the ancient building techniques that provide enhanced durability. It is possible to analyse the ancestral practices used to protect the earth material from the water action in order to understand how the old earthen buildings were preserved over the centuries, resisting to harsh weather conditions. Among these techniques are: the incorporation of biopolymers (such as oils or fats from animal or vegetable origin); the addition of some minerals; and the earth stabilization with lime. However, this knowledge seems to be forgotten, probably due to the prejudice related to earthen constructions, which several times are associated with a poor building. This research also focuses on the study of new methods of earth stabilization with lime and biopolymers, adapting the ancient knowledge to improve the durability related to the water action. Therefore, alternative solutions can be obtained to improve the performance of earthen buildings, mainly the resistance of the material in the presence of water, reducing its permeability to water. In addition, with the proposed solutions it is possible to obtain good levels of water vapour permeability, one of the major advantages of the construction with earth.

Abstract: The interest of the study on the implementation of expanded agglomerated cork as exterior wall covering derives from two critical factors in a perspective of sustainable development: the use of a product consisting of a renewable natural material – cork – and the concern to contribute to greater sustainability in construction. The study aims to assess the feasibility of its use by analyzing the corresponding behaviour under different conditions. Since this application is relatively recent, only about ten years old, there is still much to learn about the reliability of its long-term properties. In this context, this study aims to deepen and approach aspects, some of them poorly studied and even unknown, that deal with characteristics that will make the agglomerate a good choice for exterior wall covering. The analysis of these and other characteristics is being performed by testing both under actual exposure conditions, on an experimental cell at LNEC, and on laboratory. In this paper the main laboratory tests are presented and the obtained results are compared with the outcome of the field study.

Abstract: Bamboos generally have elasticity module in compression of about 9 GPa, which is a relatively low value compared to timber and concrete, 20 GPa, and steel, 200 GPa. However, the compressive strength is high - 40 to 80 MPa – that, combined with axissimetria of the cross section, makes the bamboos structural elements with high strength and flexibility. Considering the low apparent specific weight of the material 8 kN/m³, photosynthetic production and workability, bamboos have no competitor in the market so that loads can be absorbed independently by any of the above materials. But the industrial structural elements may be produced with dimensions and geometries provided in accordance with the load to be transported. This is not the case of bamboo. Thus, the capacity of the bamboo in compression becomes limited by its natural flexural rigidity, EI. Thus, different structural systems with pipe threads to make large columns or masts were investigated, [1,2], all with bamboo Phyllostachys pubescens species. In this paper, a kind of mast composed of a central bamboo 6 m in length and six smaller segments axi-symmetrically distributed around this central bamboo will be presented. This proposed design is organizationally a set of bars shackled by steel bands along the length of the beam. Flexion-compression tests with bamboo species Phyllostachys pubescens, combined with numerical modeling through the MEF were made. The loading capacity was tripled and the lateral deviations are negligible when compared with the axial bamboo tested alone. This mast, while consuming a relatively high number of bamboo units, has the advantages of ease and constructive possibility of structural use of smaller diameter bamboo. All the design and results of experimental and numerical analyzes will be discussed in this paper.

Abstract: A hollow bamboo in its raw state, from the geometrical point of view and language engineering can be defined as an element of tubular bar, not prismatic, approximately circular cross sections, stiff by intermittent internal disks positioned along the bar. The decrease in the diameter and wall thickness usually happens from the bottom up, the basal part may contain some exceptions, with sections of the base with diameters smaller than the second, then to diminish steadily to the top. This architecture has a genetic component that resulted from constant interactions of bamboo with the actions of wind, which stimulated increased local resistance of the most requested points mechanically, not only by concentrated lignification in cellulosic tissues, such as the geometric localized variations. From the viewpoint of composite materials science, bamboo can be defined as a composition of two different materials, a first fiber and vessels oriented and aligned along the internodal stem sections, which connect to another material with fibers and vessels tangled - anastonose - intermittent stiffeners composing the above cited nodes. In both materials vessels and fibers are surrounded by a parenchymathous matrix of hollow cells that store sugars. The mechanical point of view, bamboo, due to the configuration, the rigidity and strength components and a tubular geometry is a flexible structural element with high mechanical resistance. This flexibility makes the long elements have low load capacity in flexion compression, if the goal is the application of bamboo in construction structures. This issue can be circumvented by systemic compositions, called masts, [1,2] which can be applied in a single long bamboo element resistant to relatively high compressive loads. In the present investigation, four parallel bamboos 5.5 meters long, the species Phyllostachys pubescens are discontinuously connected by bamboo segments interposed fixed by steel pins, achieving this composition with a load limit of 48 kN in controlled experiments. These experiments were also used and motivated to find the numerical modeling by the MEF, whose results were widely discussed.

Abstract: The soil is a brittle material compared to other engineering materials such as steel, concrete and wood. The clayey nature of the soils of western Paraná causes them to be chemically reactive towards certain compounds, thereby improving their engineering properties, especially its mechanical strength. The study involved treating the typical soil of the region with two residues from industrial and human activities: rice husk ash (RHA) at doses 0; 2.5; 5; 7.5 and 10%; and burned sewage sludge (BSS) at doses 0; 5; 10; 15 to 20%; in the dry soil mass. The test samples were compacted in Mini-MCV equipment and broken in triaxial compression tests of consolidated undrained type, with confining pressures of 25; 50 and 100 kPa. The results showed that both the RHA change dramatically as the BSS which passes viscoelastic plastic-linear mechanical behavior of the composites. There was a significant increase in deviator tension and elasticity modulus, implying a gain in strength and stiffness of the composite compared to the natural soil. The most striking effect was observed in the RHA cohesion parameter; while the substantial effect of BSS was observed in the interparticles friction angle. These results suggest that RHA promoted the formation of new products filling the pore space of the composite, changing the clayey material in a nature of a continuum, while the BSS promoted a substantial aggregation of the particles, wherein the soil reinforcement transformed clay in a particulate material coarser grain size.