Hot Asphalt Concrete Mixes Research Articles

Application of wastepaper sludge ash as mineral powder for hot asphalt concrete mix

In this article the potentiality is proven for application of wastepaper sludge ash (WSA) as mineral powder for traditional hot asphalt concrete mix. For the comparative testing in this article the traditional limestone mineral powder is used. The chemical (oxide) composition of the aggregates was studied, while that was determined by means of DRON - 3.0 diffractometer. It was ascertained that CaO is present in wastepaper sludge ash in sufficient quantity, while it provides for utilization of this waste material as an aggregate for asphalt concrete. The limestone mineral powder granulometric composition was determined and the wastepaper sludge ash was grinded by ball grinder till the appropriate granulometric composition was reached. There were studied the main physical and mechanical parameters of bitumen 70/100 to be used for formation of asphalt binder in combination with the studied mineral aggregate. There were formed the following series of traditional hot asphalt concrete mix: on limestone mineral powder, on wastepaper sludge ash, on both limestone mineral powder and wastepaper sludge ash in ratio 50/50, 30/70, 20/80 (% w/w). By means of grading curves of dense-graded continuous mixes there was designed the chip-grain carcass of asphalt concrete mix. The asphalt concrete mix was designed based on the following characteristics: hot fine-grained densegraded asphalt concrete with residual porosity from 2 % to 5 %, with quantity of chip-grains sized more than 5 mm – 35-45 % and the maximum grain-size up to 15 mm. There was determined that WSA can perform as material to be used as mineral powder for asphalt concrete mixes. According to the requirements of Ukrainian standard (DSTU B V.2.7-119:2011), the asphalt concrete with WSA is of standard condition, but the water-saturation index approaches the acceptably allowed value, while in comparison with asphalt concrete with LMP – it is higher by 55%. Such result is due to the difference in oxide composition of the aggregates, namely lower content of products of calcareous rock in WSA. With combined application of limestone mineral powder and WSA in ratio 50/50, 30/70, 20/80 (% w/w) the water-saturation index decreases. As to the compression tensile strength and compression tensile strength after water-saturation, these indices on WSA are lower than on LMP just by 10%. The most efficient usage of WSA, considering the studies done, can be achieved when coupled with LMP in ratio 50/50.

The Impact of Utilizing Silica Fume as a Filler on Asphalt Concrete Mixes

This study evaluates the influence of utilizing silica fume as a stabilizer to the filler on the behavior of asphalt mixes. The investigation of the properties of asphalt mixes was conducted by using different percentages of Silica Fume (0, 3, 6, and 9% by filler weight). Results indicate that, the OAC is 4.7% and it achieves the best results in the Marshall tests. Marshall Stability is increased by about 27.5% and the flow is decreased by about 20.2 %. In this study the implementation of 9% of silica fume in the asphalt concrete mix showed a considerable excess in the resistance to moisture damage of 28% when compared to the original mix. A great decrease in the tensile strength of asphalt concrete mixes, in a range from (4-15)% could be noticed following the moisture damage process for both the reference and silica fume adjusted mixes. Six percent of it was the optimum percent that had developed the tensile characteristics of the hot asphalt concrete mixes. The moisture sensibility of the asphalt concrete was reduced with an increase in the silica fume content. Following the moisture damage process, Silica fume of 9% was the optimum percent that had developed the punching shear characteristics of asphalt concrete. It exhibited a positive effect of 20%, while 6-9% of silica fume exhibited a positive effect of 5-9% on the development of the tensile characteristics of asphalt concrete.

Features of the Technology of Construction of Road Pavements from Vacuum-Treated Asphalt Concrete Mix

When changing the structural properties of road construction materials, their compaction technologies should be improved with the choice of the best compaction means and their technological modes of operation in specific conditions of work conduction. For a mixture evacuated at an asphalt concrete plant that has increased water and frost resistance characteristics, as well as changed rheological parameters, it is also necessary to determine the technological parameters of the compaction means used, taking into account the features of its rheological characteristics. The compaction technology of vacuum-treated hot asphalt-concrete mix by pneumatic wheel roller with the determination of the necessary number of passes on the trail, speed modes along the roller passages and the magnitude of the air pressure in the tires of the roller has been developed. Using a promising rheological approach, the dynamics of accumulation of the asphalt concrete mixture layer density along the roller passages was studied by simulation modeling, and the time when the pneumatic roller was finished and the compaction work was transferred to heavy smooth rollers was determined. Changing the rheological properties of the vacuum-treated asphalt mix increases the efficiency of its compaction, reducing material costs, increasing the productivity of compaction tools while improving the quality and durability of road asphalt pavements. Keywords: hot asphalt-concrete mix, rheological properties, water and frost resistance of asphalt concrete, road roller, compaction.

The Non-contact Method of Assessing the Quality of the Road Surface with the Rubber Crumb in the Construction Process

Process of cooling of a paving of hot asphalt concrete mixes containing a rubber crumb at construction of highways is considered. The article presents the description of the mathematical model of calculation of temperature fields of pavement. One-dimensional unsteady heat conduction equations for each layer consist in a mathematical model. The boundary conditions on the surface of the top layer consider the heat transfer by convection and radiation. The boundary conditions of the fourth kind are between the layers. The temperature boundaries of the lower layer are constant. Testing the model is performed for limited and semi-infinite rods. The article presents the results of testing the mathematical model. Numerical solution of heat conduction equations held by the implicit scheme. Results of an experimental study of the thermal conductivity of asphalt concrete containing crumb rubber are listed in this article. In article the method of calculation of temperature of a surface of a paving is offered. The calculated values of temperature of a paving depending on the speed of a wind, solar radiation, thickness of a coat layer, a difference of thickness of a layer of hot asphalt concrete containing a rubber crumb, and reference temperature of a layer are presented. It is established that under identical conditions porosity of material of a layer has the greatest impact on change of temperature.

Modelo de previsão do índice de condição dos pavimentos flexíveis

Resumo Este trabalho apresenta o desenvolvimento de um modelo de previsão do índice de condição dos pavimentos flexíveis para a malha rodoviária, em concreto asfáltico usinado a quente, do Estado da Bahia. Teve como ponto de partida um planejamento fatorial, elaborado com base em informações de um banco de dados de rodovias, fornecido pelo Departamento de Infraestrutura de Transportes da Bahia. Para a verificação da adequação do modelo utilizou-se a reta de ajuste dos dados, o coeficiente de correlação (r), a análise de resíduos e o gráfico de probabilidade normal dos resíduos. O modelo correlaciona o desempenho do índice de condição dos pavimentos flexíveis às variáveis idade, tráfego e pluviometria, fatores que tem influência no processo de deterioração dos pavimentos. O modelo desenvolvido apresentou ajuste aos dados observados e r = 0,64, mostrando indícios da validade da sua aplicação, para as características da malha rodoviária do Estado da Bahia. Não existem modelos de desempenho universais e modelos que foram desenvolvidos a partir de dados observados em estudos realizados em locais específicos não são necessariamente transferíveis, e possuem algumas limitações inerentes.

Определение температуры нагрева поверхности выбоины дорожного покрытия при производстве ремонтных работ с применением горячих асфальтобетонных смесей

In the process of roads construction the necessary transport and operational characteristics should be achieved, which depend on the quality of the applied, material and technologies. Under the loads of transport means and the influence of weather conditions on the road pavement deformations and destructions occur, which lead to worsening of transport and operational characteristics, decrease of operational life of the road and they are often the reason of road accidents. According to the data of the Strategic Research Center of Rosgosstrah more than 20 % of road accidents in Russia occur due to bad quality of road pavement. One of the main directions in traffic security control and prolongation of operational life for road pavement of non-rigid type is road works, as a result of which defects of pavement are eliminated and in case of timely repairs of high quality the operational life of the road increases for several years. The most widely used material for non-rigid pavement repairs is hot road concrete mixes and in case of adherence to specifications they provide high quality of works. The authors investigate the problems of hot asphalt concrete mixes for repairs of road surfaces of non-rigid type. The results of the study hot asphalt concrete mix’s temperature regimes are offered in case of repair works considering the temperature delivered to the work site and the ambient temperature depending on the type of mix and class of bitumen.

Performance of gap graded cold asphalt containing cement treated filler

Previous studies have revealed the beneficial effects of adding Ordinary Portland Cement (OPC) to Bitumen Emulsion Mixtures (BEMs). These effects were confirmed for some dense graded mixtures based on recipes currently used for hot asphalt concrete mix in the UK and being considered for usage in BEMs. On the other hand, Hot Rolled Asphalt (HRA) which is a gap graded mixture is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistance durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking.This laboratory study describes the development of novel gap-graded Cold Rolled Asphalt (CRA) by using OPC instead of conventional mineral filler. Stiffness modulus, uniaxial creep, four point load fatigue, and semi-circular bending monotonic tests were used to assess the mechanical properties while stiffness modulus ratio was determined to assess the water sensitivity of the produced mixtures.The study concluded that there is a considerable enhancement in the mechanical properties and water sensitivity of CRA containing OPC. Also, the produced cement treated gap-graded CRA shows a significant lower thermal sensitivity than conventional HRA. More interestingly, the new cement treated CRA is found to be comparable with the mechanical properties of the conventional HRA after less than 1day.

Correlation between permanent deformation-related performance parameters of asphalt concrete mixes and binders

Abstract This paper examines methods to predict the performance of hot asphalt concrete mixes based on performance parameters of binders. Specifically, relationships between binder parameters determined from multiple stress creep and recovery tests were correlated to the creep parameters of hot asphalt concrete mixes obtained from cyclic load compression testing. For the determination of creep parameters, a modified expression of the creep curve is proposed to cover the entire spectrum of permanent deformation; including the tertiary creep phase. Non-recoverable compliance, unrecovered strain, and recoverable strain of binders show good correlation to creep parameters of hot asphalt concrete mixes such as creep rate and high temperature performance ratio. Additionally, unrecovered strain and non-recoverable compliance of binders correlates well with mean rut depth of asphalt concrete mixes. However, no correlation has been detected between the difference in non-recoverable compliance of binders and permanent deformation parameters of asphalt concrete mixes.

CRITICAL EVALUATION OF ASPHALT CONCRETE MIXES CONTAINING GRANULAR VOLCANIC ASH MATERIAL

Granular volcanic ash material is spread over considerable parts of Yemen, including urban and suburban areas. Due to the inferior properties of this material in its natural state, it can not be used as a foundation layer either for roads or buildings. However, when improved it can be used in different applications. A recent study by the author has indicated that using granular volcanic ash as a partial replacement of conventional basalt aggregate in hot asphalt concrete mixes is technically feasible. All conventional criteria requirements suggested by Marshal Mix Design Method for hot asphalt concrete mix design were achieved with samples at different levels of granular volcanic ash content. In this paper, further evaluation was performed to provide critical evaluation of some important mix characteristics. Samples, at different volcanic ash content, were prepared at optimum asphalt content and subjected to different advanced tests. These include dynamic creep, modulus of resilient, fatigue and permanent deformation tests. Results indicated that mixes containing volcanic ash aggregate had performed well in terms of creep and permanent deformation. However, improvements in fatigue life and in modulus of resilience were observed at volcanic ash contents up to 10% and 20%, respectively. Further investigation is recommended to find ways for improving the properties of volcanic ash material so that the negative trends in fatigue life and modulus of resilience can be dealt with at higher volcanic ash content.