Resumo: Os custos de produção de agregados reciclados de concretos de antigos pavimentos devem ser contextualizados nas obras de pavimentação rodoviária no país. Valores fornecidos em tabelas de serviços para vias urbanas podem não refletir as condições específicas da demolição em rodovias. Também, preços operados em outros países são afetados pela tecnologia de reciclagem empregada, que não é aquela que tem sido considerada no Brasil. Neste artigo são determinadas as razões unitárias de produção relacionadas à demolição, carga, transporte e britagem de pavimentos de concreto removidos de pistas de duas rodovias brasileiras. Com base nos resultados pôde-se verificar um acréscimo de 50% no custo final do agregado reciclado em relação ao agregado virgem, resultando em acréscimo de cerca de 20% nos custos de produção de concretos para pavimentação. O potencial brasileiro de produção desses agregados reciclados a partir de pavimentos de concreto deteriorados é limitado o que pode ser um fator estagnante para o emprego da tecnologia no país.Palavras-chave: agregado reciclado, pavimento de concreto, custos unitários, produtividade. Abstract:The costs for the production of recycled aggregate concrete from old concrete pavements must be contextualized in the works for road paving in the country. Values provided for urban roads works may not reflect the specific conditions of the demolition on highways. Also, prices operated in other countries are affected by the recycling technology used abroad that is not what has been used in Brazil. In this article are considered the unit production rates related to demolition, loading, transportation and crushing of concrete pavement removed from two Brazilian highways. Based on the results it was verified an increase of 50% in the final cost of the recycled aggregate compared to virgin aggregate, resulting in an increase of about 20% in production costs of concretes for paving. The Brazilian potential of production of such recycled aggregates is limited what can be a stagnant factor for the use of this technology in the country.

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Fifteen concrete slabs were instrumented with thermal resistors, allowing the monitoring of temperatures in concrete pavements slabs in São Paulo, Brazil, where a typical tropical hot and wet environment prevails. Over the course of 1 year, this research sought the influence of climatic conditions such as temperature and moisture on the daily and seasonal variations of temperature differentials through the slab depths. Daytime temperature differentials of more than 15°C were observed during typical summer days (e.g., high air temperature of 32°C and 7.6 h of solar radiation) and of about 10°C during typical winter days (e.g., low air temperature of 11°C and 3 h of solar radiation). The absolute values of nighttime temperature differentials are not as extreme as the daytime differentials and are significant mostly during spring and summer (from September to March). Nonlinear quadratic temperature distributions through the slab thickness were evident in most cases; nevertheless, distributions that are almost linear may be present at some times during the day and even at night. Positive temperature differentials were recorded even at night, and discussions of those particularities are addressed. The effects of tropical rains on temperature differentials are presented, and empirical models for the prediction of temperature differentials in slabs are suggested.

Indirect tensile strength is not usually used for concrete mixtures proportioning and its technological control; flexural strength tests under third point loads arrangement are the pattern for such goals. Indeed, neither of such tests have the capability to set up the actual strength of a concrete slab since its response is under plane stress state. A critical review of the basic concepts on both kinds of tests allows foreseeing its limitations as well as how to overcome such shortcomings. At last correlations between the two kinds of tensile strength are presented considering dry and plastic concretes typically applied on paving, corroborating to former results achieved for plastic concretes.Keywords: indirect tensile strength; flexural strength; brazilian split test.Medidas de resistência à tração indireta não são normalmente cotejadas na dosagem ou no controle tecnológico de concretos em pavimentação; os resultados de ensaios de resistência à tração na flexão, em especial com dois cutelos, são empregados para tais finalidades. Na realidade, nenhum de ambos os tipos de teste mede de fato a resistência real do concreto acabado na forma de placa por não representarem um componente estrutural que responde mecanicamente em estado plano de tensões. Uma revisão crítica dos conceitos relacionados a essas medidas de resistência permite claramente enxergar as limitações de cada uma das formas de aferição da resistência à tração e as maneiras de melhor encaminhar avaliações dessa natureza. Correlações entre ambas as medidas por meio de ensaios em concretos secos e plásticos específicos para pavimentação são apresentadas, corroborando com resultados anteriores obtidos para concretos plásticos.

The main goal of this paper is to show the analysis of the permeability characteristics of three different mixes of pervious concrete produced with the variation of the coarse aggregate size. Two different test methods were used to achieve the hydraulic conductivity of the samples: falling head and constant head permeability tests. Based on test results it is concluded that the pervious concrete mixes have shown to be good drainable materials. Besides, it was found that the permeability of the mixtures does not seem to depend on the size and gradation of the coarse aggregate.

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O emprego de agregados reciclados de resíduos sólidos da construção civil e demolição tem sido objeto de interesse de agentes públicos engajados em projetos e obras de pavimentação viária. A coleta, triagem e classificação desses materiais como agregados alternativos torna ainda possível seu emprego em concretos para algumas finalidades, sendo que no caso do concreto compactado para fins de pavimentação ainda não se tem precedente de uso no país. Estudos sobre este material para pavimentação têm sido realizados, sendo aqui apresentados resultados relativos a características mecânicas fundamentais para a análise das potencialidades do material para bases de pavimentos asfálticos e de concreto, ainda que para aplicações urbanas e em volumes limitados. Foram empregados nos estudos agregados reciclados de diferentes origens em substituição parcial ou total dos de agregados nos concretos. Os resultados obtidos permitem observar inexpressiva alteração em resistências com pequenos ajustes nos consumos de cimento. Todavia, concomitantemente ocorreu queda expressiva dos valores de módulo de elasticidade dos materiais na medida em que frações menos densas de agregados foram empregadas em maior quantidade e a parcela de substituição de agregados virgens por reciclados aumentou. As características observadas permitem a indicação do emprego do material para vias de baixo volume de tráfego além de áreas residenciais, condomínios, estacionamentos, etc. Por outro lado, o aumento da porosidade dos concretos em função da presença de reciclados exige atenção e estudos mais aprofundados sobre o comportamento à fratura e à fadiga desses materiais. <br /><br /><strong>Abstract</strong>: Along the last decades, recycled aggregate produced from waste material from civil construction activities gained growing interest for its employment in pavements. Appropriate collection, selection and sieving of such a material make it possible to use it in concretes for many applications, such as rolled compacted concrete. As partial results of an in course comprehensive study about compacted concrete, manufactured with this kind of aggregate, essential physical and mechanical characteristics of some concretes are presented herein, promptly aiding to foresee its suitability as bases for asphalt or concrete pavements, despite the constrained context. Recycled aggregate from several sources has been used as a replacement for coarse and fine aggregates in concretes. Results went beyond expectations since the little cement content increases requirements to avoid strength losses as pottery recycled aggregates contents also increase. However, the concrete modulus of elasticity has fallen with the inclusion of alternative aggregate. The set of results allow indicating that such concretes can be used in low-volume pavements such as residential ones, parking lots, garage floors, among others; nevertheless, the increasing porosity of the compacted concretes using recycled aggregate needs further attention as regards to fatigue and fracture of such materials for paving purposes.

ResumoIn recent years, due to the destructive and unproductive character of pavement specimen extraction, pavement maintenance technology intensified the use of non-destructive techniques for pavement evaluation which resulted in the development of several devices and evaluation methods. This paper describes the use of technology based on low frequency ultrasonic tomography for evaluation of concrete pavement parameters. The equipment was applied in three experimental sections with different concrete pavements built at the University of Sao Paulo campus. The ultrasonic signal processing is given. The results analysis enables the efficient and reliable identification of thickness and reinforcement position within the concrete slab. Construction problems were evidenced in one of experimental sections with thickness deficiencies and reinforcement in a position below projected. Furthermore, the use of a novel concrete quality indicator was correlated with the presence of transverse cracks and alkali-silica reaction within the sections.