João Adriano Rossignolo

PROPERTIES OF HIGH-PERFORMANCE LWAC FOR PRECAST STRUCTURES WITH BRAZILIAN LIGHTWEIGHT AGGREGATES

Abstract An experimental study was carried out to examine five mixtures made with selected Brazilian lightweight aggregates in order to produce lightweight aggregate concrete (LWAC) for slim precast components. Flow (initial and after 2 h), air content, compressive strength, tensile strength (flexural and splitting), modulus of elasticity and deformation were studied. The 7-day compressive strength and the dry concrete density varied from 39.7 to 51.9 MPa and from 1460 to 1605 kg/m 3 , respectively. The results of this pilot study suggest that there are possibilities of producing slim precast components using high-performance lightweight concrete with Brazilian lightweight aggregates.

Mechanical properties of polymer-modified lightweight aggregate concrete

Abstract This paper deals with the properties of styrene–butadiene rubber (SBR)-modified lightweight aggregate concretes (LWACs) for thin precast components, made with two Brazilian lightweight aggregates (LWAs). Properties in the fresh state, compressive strength, splitting tensile strength, flexural strength, and water absorption of LWACs were tested. The 7-day compressive strength and the dry concrete density vary from 39.7 to 51.9 MPa and from 1460 to 1605 kg/m3, respectively. The inclusion of SBR latex in LWACs decreases the water–(cement+silica fume) [W/(C+S)] ratio and water absorption and increases the splitting tensile and flexural strengths. The results of this pilot study suggest that there are possibilities of producing thin precast components using SBR-modified LWACs with Brazilian LWAs.

Sugarcane bagasse and castor oil polyurethane adhesive-based particulate composite

This paper discusses the potential use of sugarcane bagasse in two different fiber lengths (5 mm and 8 mm) of the same density as a raw material for the production of particleboards, using castor oil-based two-component polyurethane adhesive. The quality of the product that can be manufactured industrially was evaluated based on density, thickness swell (TS), absorption (WA), modulus of elasticity (MOE), modulus of rupture (MOR) in static bending and internal bond (IB), according to the Brazilian NBR 14.810:2006 standard. The results revealed a significant difference between the particleboards made with 5-mm-long fibers and those made with 8-mm-long fibers. An analysis by scanning electron microscopy (SEM) indicates that the interparticle spaces are filled with castor oil-based two-component polyurethane adhesive, contributing to improve the physicomechanical properties of the particleboards. A durability assessment based on accelerated aging tests shows that waterproofed particleboards can be used in moist environments.

Eficiência térmica de telhas onduladas de fibrocimento aplicadas em abrigos individuais para bezerros expostos ao sol e à sombra

This research presents a study of roof thermal efficiency in individual housing for calves exposed to sun and shade through infrared thermography, internal temperature and thermal comfort indexes. Four different individual housing for calves covered with asbestos-free fiber-cement corrugated sheets were evaluated. Three of them were directly exposed to the sun: (i) corrugated sheets painted white in the external surface, (ii) corrugated sheets without painting and (iii) with screen shade fabric installed 0.10m under de internal surface of the corrugated sheet. The fourth individual housing was installed in the shade area and covered with unpainted corrugated fiber-cement sheets. The analysis was taken for 21 days at 11h00min, 14h00min and 17h00min. The results indicate significant variations in the roofing surface temperature and thermal comfort indexes among the treatments exposed to the sun and shade, for all the evaluations during the day. The infrared thermography images were effective for better understanding the heat transfer processes from the roof to the internal environment of the housing.

Effect of silica fume and SBR latex on the pasteaggregate interfacial transition zone

This paper deals with the effect of silica fume and styrene-butadiene latex (SBR) on the microstructure of the interfacial transition zone (ITZ) between Portland cement paste and aggregates (basalt). Scanning Electron Microscope (SEM) equipped with energy dispersive x ray analysis system (EDX) was used to determine the ITZ thickness. In the plain concrete a marked ITZ around the aggregate particles (55 µm) was observed, while in concretes with silica fume or latex SBR the ITZ was less pronounced (35-40 µm). However, better results were observed in concretes with silica fume and latex SBR (20-25 µm).

Avaliação da condutividade térmica de concretos leves com argila expandida

This work fits in a research project on the broader development of lightweight concrete for application in the construction system of cast-in-place monolithic panels of concrete and having as reference the influence of the concrete in the performance of the thermal comfort of the construction. Specifically, this work will present the evaluation of the influence of the expanded clay on the value of the thermal conductivity of the lightweight concrete used in this constructive system. The values of thermal conductivity of lightweight concrete with densities ranging from 1216 to 2364 kg/m3, produced with expanded clay to replace the natural coarse aggregate (basalt), we esalnated. The thermal conductivity of the concrete was determined using the “Method of the Parallel Hot Wire” and varied between 0.54 and 1.80 W/mK.

Evaluation of Calcined Clay Lightweight Aggregates Made with Alkali Activators

This paper aims the evaluation of water absorption and compressive strength of calcined clay lightweight aggregates produced using alkaline activators. The characterization of ceramic material was made by techniques of liquid and plasticity limits, particle size analysis and chemical analysis. The specimens made from these ceramic materials and alkali activators (potassium silicate, sodium silicate with NaOH (15M), phosphoric acid, sodium silicate, potassium hydroxide and sodium hydroxide) were burned at temperatures of 600 °C and 900 °C and they were characterized by evaluation of water absorption and compressive strength. Results of this research indicates that the burn temperature has influence on the final properties of calcined clay lightweight aggregates and, when this aggregates were made using some activators, as sodium silicate, they presented lower values of water absorption and higher values of compressive strength, for both burn temperature, which can generate significant energetic gain in the aggregates production process).

Particleboards with Agricultural Wastes: Sugar Cane Bagasse and Reforestation Wood

In this paper, it was consider the study of the use of sugarcane bagasse and wood particles, residues from the agricultural and the furniture industry, in order to add value to such materials. To add value to these materials it will be utilized in the manufacturing of hybrid panels consisting of wood particles and sugarcane bagasse in certain proportions (20%, 40% and 60%). For the production it was used the bi-component polyurethane resin based on castor oil. Analysis of the products was established based on the physical-mechanical standard NBR 14.810:2006. The hybrid panels were analyzed according to the data obtained in relation to the American standard ANSI A208.1-1999, in order to determine the best treatment for the possible use as a lining in agricultural buildings. Moreover, the hybrid panels were contrasted with panels of other formulations, with similar density. It was evident that the treatment constituting of 40% of sugar cane bagasse and 60% of wood particles had the best physical-mechanical, and showed a potential for the use in non-structural applications.

Influência dos agregados leves de argila calcinada nas propriedades mecânicas de concretos estruturais

This paper aims to evaluate the influence of calcined clay lightweight aggregates on the mechanical properties of structural concretes. Lightweight aggregates were extruded with moisture content close to their plastic limits. After the manufacture of calcined clay lightweight aggregates, concrete specimens were made using calcined clay lightweight aggregates, expanded clay and basalt. Specimens were characterized by fresh specific mass, slump test (fresh condition), compressive strength, tensile strenth, modulus of elasticity and specific mass (cured state). Results of this research indicates that aggregates have great influence on the mechanical properties of concretes and calcined clay lightweight aggregates showed intermediated characteristics when compared with expanded clay and basalt aggregates.

Avaliação da influência de agregados leves de argila calcinada no desempenho de concretos estruturais

Este trabalho tem por objetivo a avaliacao de desempenho de concretos leves produzidos com agregados leves de argila calcinada. Primeiramente, foram coletadas e caracterizadas diferentes amostras de solo (argila) do estado de Sao Paulo. Em seguida, foram confeccionados corpos de prova de argila calcinada com as diferentes massas cerâmicas coletadas. Os corpos de prova confeccionados com essas massas cerâmicas, queimados a temperatura de 900 oC, foram caracterizados por meio da avaliacao da absorcao de agua, porosidade aparente, massa especifica aparente, expansao por umidade e resistencia a compressao. Em seguida, foram moldados corpos de prova de concreto com agregados leves de argila calcinada produzidos com massas cerâmicas provenientes das cidades de Itu, SP, e Porto Ferreira, SP, com argila expandida e tambem com brita. Os concretos foram submetidos aos ensaios de massa especifica e abatimento do tronco de cone, no estado fresco e de resistencia a compressao, resistencia a tracao por compressao diametral, modulo de deformacao e massa especifica no estado endurecido. Os resultados desta pesquisa indicam a viabilidade tecnica da producao de agregados leves de argila calcinada para utilizacao em concretos, uma vez que o desempenho de concretos produzidos com agregados leves de argila calcinada e semelhante ao de concretos produzidos com argila expandida e basalto.