José Tadeu Balbo

This paper evaluates the aspects of dosage, construction, quality control, and functional and structural quality of self-compacting concrete (SCC) paving slabs built in a vehicle parking area, on a flat surface, with reduced thickness (100 mm). The previously established target for slump flow for applying 8 m³ SCC was agility; aspects related to shrinkage and surface are discussed herein, as well as other lessons learned in a preliminary study. The surface and structural characteristics resulting from the pioneer application were verified by texture tests and dynamic load tests (Falling Weight Deflectometer). The strength and stiffness results were indicative of the SCC's superior quality in terms of durability to fatigue. The stress analysis based on the measured parameters for the concrete slabs indicated the full possibility of using SCC, with economic advantages due to the significant reduction in design thickness, for automobile parking lots, resulting in very low stresses (under 20% of the flexural strength). Regarding deflections, the values measured are about twice the values commonly found for conventional concrete pavements because of the thin slab thickness. Finally, an expressively lower modular relationship (E/MR) was obtained revealing the potential of SCC to perform better than conventional concrete in face of fatigue damage.

Clogging of porous concrete pavements is understood as a performance pathology within this peculiar concrete component. Albeit the clogging performance of porous concrete pavements is a sensitive topic in technical literature, most studies refer to laboratory investigations on concrete samples using different kinds of apparatus for the simulation of loss of permeability due to debris insertion on porous interstices. However, infiltration rate measurements are the basis for defining maintenance needs in actual pavements and shall be carried out periodically to measure and endorse infiltration rate adequacy as the kern of a clogging management protocol. This study dealt with a field experiment in a pervious concrete sidewalk surrounded by a wooded garden with tropical native and a variety of exotic trees. Over four years, eleven monitoring measurements were carried out using the ASTM C1701 infiltration ring test. The main contribution of this paper is a proposition of a mixed linear prediction model considering conditioned exponential distribution and a random normal intercept for the infiltration rate. From residual analysis and diagnosis plots, it can be seen that the proposed model presents a goodness of fit, allowing anticipation of infiltration rates reduction due to clogging by dense organic matter. Minimum infiltration rate is taken as 0.1 cm/s and such condition was achieved in a couple of months, awakening consciously to consider three to four intensive cleaning maintenance per year in dense wooded areas like public parks.

The west section of the Governor Mário Covas São Paulo Metropolitan Road Ring was opened to traffic in 2002. The original pavement was a jointed plain concrete pavement with dowelled joints and a design flexural strength (or modulus of rupture) of 4.5 MPa. Premature failure of the concrete slabs was observed not only by engineers and users, but also reported by the media. Concrete slabs soon started being demolished and replaced. Many of the removed slabs were taken to a nearby recycling plant for crushing. However, the resulting recycled concrete aggregate was not used in the manufacturing of the new slabs. There were concerns that the potential presence of detrimental chemical substances had caused the early deterioration of the slabs. If that were true, using recycled aggregates obtained from the original concrete could result in the same issues in the new mix. This paper describes a feasibility study on recycling the original concrete for use as aggregate in new concrete slabs. The first goal was to verify the presence of fluorite as detrimental substance in the existing concrete because there was a suspicion among concrete technologists engaged on mixture design during the construction. Chemical analysis using X-ray fluorescence spectrometry did not show the presence of chemical components detrimental to concrete durability. Therefore, the second goal was to accept the material for recycling and discuss mix proportions, strength, stiffness, fracture toughness, and fatigue. Although some of the concrete properties were affected by the inclusion of recycled aggregates in the mix, the results indicate that it is possible to use recycled aggregates produced from the original concrete to cast new concrete slabs, however requiring greater thicknesses. The fatigue performance of recycled mixtures points out the demand for thicker and eventually more expansive design solutions.

Stabilization of soils and granular materials has long been used in the 20^th century by road engineers to improve the stiffness of base materials considered unsuitable for paving. Stabilization can be achieved by mixing different materials to change the grain size distribution or even by adding chemicals to the original material, or by combining both processes, to obtain mechanical benefits. The first is achieved by means of improvements of mixture gradation seeking to increase the aggregates interlocking; the second one is associated with the addition of a stabilizing agent such as a hydraulic binder, lime, some types of pozzolans and blast furnace slag activated by lime or cement [¹ 1 E. J. Yoder and M. W. Witczak, Principles of Pavement Design, 2nd ed. New York, NY, USA: Wiley, 1975. ]–^[5] 5 P. Wu, Cement-Bound Road Base Materials, Report 7-11-218-1. Delft, The Netherlands: Delft Univ./PowerCem Technol., 2011. .

Concept of arresting system for vehicles moving on wheels at high speed in roads and highways is not a new subject for Transportation engineers. For instance, regards to trucks losing control where effectively taken as an emphatic design concern during the 1960s after AASHTO Road Tests and its extension studies. Deacceleration and arrester beds are strategically built in road locations with steep ascending ramps to permit the escape of runaway trucks; arrester beds are also placed laterally in dangerous curves in racetracks. In general, the safety containment facilities for trucks runaway are the combination of a gravity ramp (ascending grade), an arrester bed with a certain thickness of small round gravel or sand, and a dragnet with energy absorbing poles [¹ 1 AUSTROROADS, Guide to Road Design Part 6: Roadside Design. Sidney: Safety and Barriers, 2010. ], [² 2 F. A. Capuano, E. Heymsfeld, and N. Li, “Alternative arresting system ramps design for truck escape,” Int. J. Crashworthiness, vol. 23, no. 6, pp. 618–626, 2018. ]. Studies for arresting facilities in highways have been developed main during years 1970s to 1980s [³ 3 Federal Motor Carrier Safety Administration, The Large Truck Crash Causation Study – Analysis Brief (FMCSA-RRA-07-017). Washington, DC, USA: FMCSA, 2007. ], consolidating such systems on codes and design guides [⁴ 4 Federal Highway Administration, Interim Guidelines for Design of Emergency Escape Ramps (FHWA Technical Advisory, T 5040.10), Washington, DC, USA: U.S. Department of Transportation, 1979. ], [⁵ 5 American Association of State Highway and Transportation Officials, A Policy on Geometric Design of Highways and Streets, 6th ed. Washington, DC, USA: AASHTO, 2011. ].

A brita graduada tratada com cimento (BGTC) foi no país introduzida em meados da década de 1960 (SP-280). A tecnologia de mistura e parâmetros de dosagem pouco se alteraram desde então, à exceção de limitados trabalhos de pesquisa publicados que exerceram influência em inúmeros projetos de pavimentos semirrígidos elaborados a partir dos anos 1990. Nas últimas três décadas as tecnologias de cimentos e concretos evoluíram para o atendimento de novos desafios e principalmente para superação de limitações técnicas referentes à dosagem, fissuração, aos processos de usinagem e aos métodos construtivos, bem como durabilidade e sustentabilidade das estruturas. A BGTC, contudo, não absorveu novos conceitos para aplicações em pavimentação com materiais cimentícios, visando sanar desempenhos bastante questionáveis observados no material em serviço. Este artigo trata de uma sistematização de conhecimento, na forma de diálogo triádico escrito (conforme proposto pelo educador Gordon Wells da Universidade de Toronto) entre orientador e orientada, para exploração de tecnologia de concreto na busca de BGTC mais durável, aqui de maneira inaugural alcunhada por BGTC de Alto Desempenho - BGTCAD. São apresentados, comentados e discutidos os meios e princípios tecnológicos disponíveis para se obter misturas de elevada resistência e durabilidade. O artigo apresenta uma abordagem orientada por método de aprendizagem comum na área de Educação denominado IRF (inquire-response-follow up). São discutidas e exploradas as incorporações de tecnologias de concreto para as misturas de BGTC em face das melhorias de desempenho esperadas, bem como racionalmente enfrentada a questão da relação água/cimento na mistura e suas implicações, apresentando-se um modelo multiplicativo para análise da expectativa de ganho de resistência requerido para misturas de elevada qualidade preservada a essência de uma BGTC para o meio rodoviário.

Concrete is one of the most widely used construction materials all around the globe. Associated with urban expansion, concrete pavements increase the impermeable surfaces that affect the hydrological cycle and generate urban heat islands. Cement is one of the main components of concrete, and its production is one of the main sources of worldwide CO₂ emissions. Pervious concrete with partial cement replacement represents a more sustainable alternative. In this paper, the use of natural pozzolans zeolite and pumicite, as partial cement replacement materials in pervious concrete mixtures, is analyzed. The mechanical and hydraulic properties of pervious concretes using different percentages of pumicite and zeolite to replace cement (0% to 20%) were evaluated by a series of tests on compressive strength, flexural strength, permeability, porosity, and a microanalysis by SEM for the samples. Additionally, experiments with a plasticizer additive were conducted. The results show that mixtures with 0.35 W/C ratio present better mechanical and hydraulic properties; pumicite shows a better performance than zeolite, with the better properties achieved at 10% cement replacement; and the addition of plasticizer increased the final strengths. It is recommended to partially replace cement by adding 10% pumicite and to consider using 0.7% of plasticizer.

Para o incentivo e aumento do uso da bicicleta nas cidades, é necessária a oferta de vias cicláveis com geometria adequada. Este trabalho teve como objetivo contribuir para a avaliação da adequação geométrica das ciclovias e ciclofaixas de São Paulo. Para tanto, foi delimitada uma área piloto subdividida em segmentos da rede cicloviária para que três aspectos pudessem ser avaliados: larguras, declividades e velocidades. Foram coletadas as larguras médias e calculadas as declividades de cada segmento e observadas as velocidades máximas permitidas dos automóveis das vias adjacentes para comparação com intervalos de referência. Estes valores foram integrados no Indicador de Adequação Geométrica de Vias Cicláveis (IAGVC) que mostrou que nenhum segmento da área piloto é plenamente inadequado, porém apenas 28,95% foram classificados como plenamente adequados.

Loratorial tests with pervious concrete comprised porosity and hydraulic conductivity as well as mechanical parameters as compressive, indirect tensile and bending strengths besides assessing its static and dynamic elasticity moduli. Later, a pervious sidewalk area of 1.0 x 8.65 square meters was built in order to determine the variation of the infiltration rate along time; over such experimental sidewalk, impact deflection tests performed allowed to assess back calculated moduli of the pervious concrete layer, resulting 33% to 13% lower than conventional concretes. A mechanistic analysis allowed to estimate the required thickness of concrete for heavy- and light-traffic areas. Tests disclosed no significant difference among the different concrete mixes, with 25% porosity and 0,1 cm/s permeability. Initial sidewalk infiltration rate of 0.5 cm/s dropped 50% four months after construction. It was verified that pervious concrete thicknesses for trucks and buses use are far higher than conventional concrete pavements.