Luciano Pivoto Specht

Key parameters controlling dynamic modulus of crushed reclaimed asphalt paving–powdered rock–Portland cement blends

In order to minimise the impact on the environment of reclaimed asphalt paving (RAP) disposal, a policy was established in Brazil determining that such residue should be recycled and used in roadways whenever possible. Mixing RAP with powdered rock and Portland cement to be used as a base/sub-base of pavements has been experienced with interesting results. Though, there is a lack of studies on the mechanical properties (unconfined compressive – qu and split tensile – qt) and the viscoelastic behaviour (dynamic modulus – E* and phase angle – δ) of RAP – powdered rock – Portland cement blends. The present research aims at quantifying the influence of amounts of Portland cement (C) and the effect of the porosity (η) of the compacted blend in improving qu, qt and E* of the mixtures. This paper advances in the understanding of the key parameters controlling strength and stiffness of compacted RAP – powdered rock – Portland cement mixtures by quantifying the influence of porosity/cement index (η/Civ) on qu and qt strengths and mainly on the viscoelastic behaviour (E* and δ), including the effect of frequency (F) and the testing temperatures (TT). A single qt/qu relationship equal to 0.17 was found, being independent of the η/Civ. On the other side, it is shown that η/Civ is an appropriate parameter to assess both the E* and the qu of the RAP – powdered rock – Portland cement mixtures studied. The phase angle (δ) of the compacted mix is not affected by η/Civ, being slightly influenced by F and TT. It varies from a minimum of 3° at low testing temperatures and high frequency to a maximum of 14°.

Application of artificial intelligence to modelling asphalt–rubber viscosity

The viscosity of binder is of great importance during the handling, mixing, application and compaction of asphalt in highway surfacing. This paper presents experimental data and the application of artificial intelligence techniques (statistics, artificial neural networks (ANNs) and fuzzy logic) to modelling of apparent viscosity in asphalt–rubber binders. The binders were prepared in the laboratory by varying the rubber content (RC), rubber particle size, duration and temperature of mixture in conformity with a statistical design plan. Multi-factorial analysis of variance showed that the RC has a major influence on the viscosity observed for the considered interval of parameters variation. When only limited experimental data of design matrix are available for modelling, the fuzzy logic model is the best model to be used. In addition, the combined use of ANN and multiple regression analysis improved the characteristics of the neural network.

Avaliação do ruído através do SPBI (Statistical Pass-By Index) em diferentes pavimentos

O transporte rodoviario causa grande impacto no meio ambiente, tanto pelo grande consumo de energia quanto pela infra-estrutura fisica necessaria a sua operacao. A emissao de gases e os ruidos causados pelo trafego causam danos irreversiveis ao meio ambiente e tem sido alvo de inumeros estudos e pesquisas. Sabe-se que o atrito pneu/pavimento e as propriedades acusticas dos revestimentos influenciam de sobremaneira a geracao e a propagacao do ruido. Essa pesquisa tem como objetivo avaliar o ruido causado pelo trafego de veiculos em quatro diferentes pavimentos implantados em diferentes rodovias atraves do SPBI (Statistical Pass-By Index). A metodologia adotada seguiu as prescricoes da norma ISO 11819-1, a qual determina que um decibelimetro seja instalado na lateral da via para medir o ruido maximo causado pela passagem de um veiculo. O revestimento em CBUQ foi o pavimento cujas maiores medidas foram observadas (86,84dBA) seguido do CCP (83,28dBA), do TSD (83,26dBA) do MICRO (81,14dBA) e da CPA (81,03dBA). Os resultados indicam que a escolha adequada do revestimento pode atenuar de maneira expressiva o ruido causado pelo trafego rodoviario.

Análise da transferência de calor em paredes compostas por diferentes materiais

O projeto de edificacoes energeticamente eficientes necessita de conhecimentos sobre a transferencia de calor proveniente do ambiente externo, a fim de criar solucoes que associem diferentes materiais e espessuras as condicoes desejadas de conforto termico. O objetivo deste trabalho e avaliar diversos tipos e disposicoes de materiais em paredes de tijolos macicos, sob a otica da termica de edificios. Para a realizacao dos experimentos, modelos em escala real foram confeccionados, instrumentados e acoplados a uma câmara termica, desenvolvida especialmente para esse fim. O problema de transferencia de calor foi modelado pela equacao da energia, resolvida em Diferencas Finitas Centrais, utilizando-se o Metodo Implicito. As difusividades termicas dos materiais foram calculadas resolvendo o Problema Inverso de transferencia de calor. Tambem foi calculado o fluxo de calor e o custo total de cada alternativa, finalizando-se com a obtencao da relacao termoeconomica para cada parede. Atraves da analise termoeconomica pode-se constatar que, apesar de o investimento inicial ser relativamente maior nas paredes mais espessas e/ou com isolamento termico, estas apresentam um comportamento termico muito superior as tradicionais. Notadamente, a parede com EPS na face exterior apresentou o melhor desempenho.

Construção de estruturas de contenção utilizando pneus inservíveis: análise numérica e caso de obra

The use of scrap tires in civil engineering involves creative solutions and diversified applications. The present paper presents parametric analyses based on laboratory data with different tires, wall heights, filling materials, water levels and soil friction angles. A design draft for 376 different earth retaining structures (combining all variables) was made and a statistical analysis performed to study the effect that each variable had on the base value. Finally, a case study is presented of a tire wall construction near Ijui City - RS. The cost of this solution is given in comparison with the traditional concrete ones.

PAHs emissions by 12 Brazilian bitumens: procedure and results

In the last few years, there has been a great focus on human health and improving working conditions. Within this context, it is necessary to study the impact of the highway construction on the quality of life of workers and the environment. This paper aims to study polycyclic aromatic hydrocarbons (PAHs) emission from different bitumens commercialised in Brazil (conventional, modified by polymer or rubber and natural asphalt). The bitumens were submitted to conventional (Brazilian specifications) and rheological (SUPERPAVE classification) tests. The most usual application method is as a hot mixture. When heated, the bitumen releases volatile species and solid particles carried by gases, and this mixture is called bitumen emissions. In this fume, there are organic substances (PAHs), some of which may be carcinogenic. Therefore, the fume emitted during bitumen heating is harmful to health and should be considered both from the environmental sustainability and the worker health points of view. PAH studies were done alongside with other studies where the bitumen and the emission of some PAHs were correlated, which were measured through an experimental apparatus that generates and collects the bitumen fume. The equipment used was a nominated extraction and collection device (ECD) and the tests were conducted on laboratory benches. The fumes were collected in ECD and analysed by liquid chromatography–mass spectrometry to quantify the amount of emitted PAHs. From the research, it was possible to verify if bitumens with different behaviours at paving, from the perspective of sustainability and different impacts to the environment and human health. These emissions have an impact on health and the environment, which require further understanding.

Comportamento mecânico de material fresado após processo de estabilização granulométrica e química por meio da incorporação de cimento e cinza de casca de arroz moída

This research aims to evaluate, through laboratory testing, the feasibility of using pure and stabilized reclaimed asphalt pavement (mechanical, chemical and grading) in layers of flexible pavements. The milled materials are from BR-290 and ERS-509 roadways. Grading stabilization was performed and determined the level of 70% of milled material and 30% of virgin aggregate. For testing of compressive strength were molded into test specimens of 10x20 cm with different levels of Portland cement (CP IV-32), and determine the content of 4,86% (BR-290) and 5,37% (ERS-569) from the compressive strength of 2.1 MPa at 28 days. From these results, specimens were molded for testing the axial compressive strength, indirect tensile strength and resilient modulus; in these specimens, the cement was replaced by rice husk ash (mesh #325 and #500) in ratios of 15, 30 and 50% by weight of cement content, and put into moist chamber for 7, 28 and 160 curing days. The results showed that for compressive and tensile strength, the replacement of 15% of cement by CCA was efficient, with no drop resistance compared to the reference samples. Also evident the effectiveness of CCA, showing positive results when compared to those mixes only with the real content of Portland cement used and with the environmental appeal becomes an interesting alternative for use in pavement layers.

PAHs emissions by Brazilian bitumens

In the last few years, there has been a great focus with human health and improvement in workers’ conditions. Within this context, it is necessary to study the impact caused by the highway construction in people’s life quality. This paper aims to study PAH’s (Polycyclic Aromatic Hydrocarbons) emission from different bitumens commercialized in Brazil (conventional, modified by polymer or rubber and natural asphalt). The bitumen’s were submitted to conventional tests (brazilian specifications) and rheological (SUPERPAVE classification). The most usual application method is hot mixture. When heated, the asphalt releases volatile species and solid particles carried by gases which mixture is called bitumen emissions. Ian this fume there are organic substances (PAH`s), and some of which may be carcinogenic. Therefore, the fume emitted in the bitumens heating is harmful to health and should be considered, both from the environmental sustainability and the worker`s health point of view. PAH`s studies were done alongside with other studies about bitumens where the bitumen and the emission of some PAH`s were correlated, which will be measured through an experimental apparatus that generates and collects the bitumen fume. This equipament is nominated ECD (extraction and collection device). The fumes are collected and analyzed by LC-MS/MS (liquid chromatography mass spectrometry) to quantify the amount of emitted PAH`s. From the research, it will be possible to verify if bitumens with different behaviors at paving have, from the perspective of sustainability, different impacts to the environment and human health. These emissions, although low, have an impact not well known on health and environment.

Identification of pavement layers using a thermal probe

To obtain information about pavement structure, nowadays, destructive prospecting is carried out, interfering significantly with traffic. Proposed here in is a less destructive and invasive technique, whereby a thermal probe with temperature sensors is installed in the pavement. This process identifies the sources of heat to obtain the temperature distribution as a function of time and space at different depths; to solve the heat transfer problem in two dimensions and to estimate the thickness and thermal materials properties of each layer through the Inverse Problem. The Direct Problem has been modeled by a heat conduction equation and solved by Central Finite Differences, using the explicit method of time advancements. The Genetic and Memetic Algorithms have been efficient in estimating the thickness of the layers and they have presented little difference between the estimated values at each application. The proposed technique has been efficient in estimating the thickness in the tests with experimental pavements and it brings a new perspective for structural evaluation, with reduced pavement intervention and traffic interference.

DETERMINAÇÃO DA CONDUTIVIDADE TÉRMICA DE DIFERENTES MATERIAIS DE CONSTRUÇÃO ATRAVÉS DO MÉTODO DO REGIME REGULAR

Resumo: Neste trabalho procurou-se estudar a condutividade termica de alguns materiais empregados na construcao civil da regiao noroeste do estado do Rio Grande do Sul, atraves da analise das temperaturas e aplicacao do Metodo do Regime Regular. Atraves dos processos implementados e dos dados obtidos percebe-se que os resultados poderao ser muito uteis, simulando o comportamento termico de estruturas civis.