Jamel Neji

The use of fluvial and marine sediments in the formulation of Roller Compacted Concrete for use in pavements

In the manufacture of Roller Compacted Concrete (RCC) used for pavement materials, various types of aggregates are used, such as crushed and rolled limestone or siliceous aggregates. The main objective is always to reach the maximum compactness to achieve higher mechanical performances. In the present work, fluvial and marine sediments, resulting from the dredging of harbours and rivers, were introduced as aggregates in the preparation of RCC for pavement construction, with a view to improving the mechanical strength of the RCC. This study included a granulometric, mineralogical and chemical characterization of the aggregates. The work also contains a mechanical characterization of the resulting material. The objective of the study was to find a resistant RCC, by developing materials such as sediments that are often classified as a waste and where their storage is harmful to the environment. The mechanical strengths obtained showed the profitability of using a Roller Compacted Concrete containing sediments.

Laboratory Investigation of Cement-Treated Reclaimed Asphalt Pavement Material

AbstractCold in-place recycling is considered as a pavement rehabilitation technique that is more environmentally friendly than the common practice of simply constructing a new hot-mix asphalt (HMA) overlay on the existing wearing surface. This paper describes a laboratory experimental study for the formulation and mechanical characterization of cement-treated reclaimed asphalt pavement (RAP) material to be used as a base layer during the rehabilitation of pavements. RAP content was varied between 0 and 100% in order to study the effects of this parameter on the mechanical properties. Portland cement content was kept constant at 6% by weight of dry constituents. Results have shown that an increase in RAP content results in a decrease in compressive strength, flexural strength, indirect tensile strength, and elastic modulus. However, for any RAP content of 60% or less, acceptable mechanical properties for a pavement base layer were achieved. Unrestrained shrinkage testing showed statistically insignificant...

Prediction and Measurement of the Bending Strength of the RCC

The present work deals with the prediction, through models and experimental evaluation, of the bending strength of roller compacted concrete (RCC) for pavement applications. This concrete was manufactured using low cement proportioning (150 to 250 kg/㎥). The characterization of hardened RCC was carried out by experimental measurements of bending strengths. The predictions of these characteristics were achieved using empirical models. Comparison, of the values found in experiments with those empirically obtained, was made in order to choose and to propose the adapted and the most reliable models of prediction. The study showed that the bending strengths of the RCC mixture, experimentally found, can be also identified by models.

Compacted Sand Concrete in Pavement Construction: An Economical and Environmental Solution

This paper will discuss how compacted sand concrete is being researched for potential usage in road construction because of the overexploitation of quarry gravels and the risk of a shortage in gravel resources in many countries throughout the world. This paper describes the steps followed to validate the use of such material from the proportioning to the performed mechanical tests (compressive strength, indirect tensile strength, flexural strength, and Young’s modulus). This study also describes the development of an economic test setup to test the fatigue properties of compacted sand concrete. The developed machine produced repeatable results and was able to generate the fatigue curves for a conventional concrete mixture and three different compacted sand concrete mixtures. Two of the tested sand concrete mixtures were made using crushed sand from two different quarries, whereas the third one was made using a mixture of crushed sand and desert sand. The encouraging fatigue results, as well as the acceptable initial construction costs, validate the use of compacted sand concrete in pavements.

Laboratory evaluation of an ecological pavement construction material: sand concrete reinforced with polypropylene fibres

This paper presents the findings of an experimental study performed on sand concrete reinforced with polypropylene fibres, which is a fine concrete containing only sand as aggregate. The material is intended to be used for the construction of rigid pavements for secondary roads. This material is considered ecological since it saves on the consumption of coarse aggregates, which natural resources are getting scarce, and it is based on two materials that are considered as wastes, namely sea-dredged sand and quarry sand. The performed tests include compressive strength, indirect tensile strength, three-point bending flexural strength, modulus of elasticity and free shrinkage. It was found that polypropylene fibres slightly reduce the mechanical properties of the material but significantly enhance its shrinkage behaviour as well as its toughness and therefore ductility. It was concluded that sand concrete reinforced with 1% (by weight of cement) polypropylene fibres is a suitable material for constructing rigid pavements for low-traffic roads.

Mechanical properties of non-autoclaved foam concrete: analytical models vs. experimental data

Abstract In this paper, we focus on the mechanical characterisation of non-autoclaved foam concrete according to its macro porosity (foam volume fraction). Firstly, five densities of foam concrete ranging between 600 and 1400 kg/m3 have been designed and then made by varying the volume fraction of a pre-formed organic foam within the same mortar matrix. Secondly, this range of foam concrete has been characterised experimentally by measuring their Young’s moduli and their compressive and flexural tensile strengths. Based on these experimental results, it has been confirmed that foam concrete mechanical properties decrease with the increase of its macro porosity. Besides, analytical models have been identified to predict foam concrete mechanical properties according to its macro porosity. In fact, it has been found that the Young’s modulus and the compressive strength of foam concrete can be well predicted according to its macro porosity by Balshin type power laws. Moreover, it has been shown that a Shiller type exponential law gives a good prediction for the foam concrete flexural tensile strength. Finally, it has been observed that foam concrete tensile failure becomes less brittle when its macro porosity increases.

Experimental testing and modelling of roller compacted concrete incorporating RAP waste as aggregates

Abstract In recent years, recycling reclaimed asphalt pavement (RAP) has been growing to resolve the waste storage problem and to limit usage of natural resources. One possible recycling technique is cold reuse of RAP as an alternative aggregate in manufacturing roller compacted concrete (RCC) which is an innovative technique for sustainable pavements. The objectives of this study are twofold. Firstly, the effects of substitution of natural aggregates by RAP on RCC mechanical properties (modulus of elasticity, splitting-tensile strength and compressive strength) are tested experimentally. Then, several existing compressive strength models (Bolomey, Tango, and de Larrard models), initially developed for ordinary Portland cement concrete, were tested to evaluate their relevance to the case of this particular concrete. Mechanical laboratory tests results carried on six designed RCC mixes showed that the RCC properties decrease as RAP content increases. Besides, compressive strength modelling results showed that the tested models are all relevant, to different degrees, for the case of the studied mixtures. de Larrard model which accounts for the adhesion quality between aggregate and cement matrix showed that this region is negatively affected by RAP presence. This finding can explain the observed decrease in the mechanical characteristics.

Study of the Anisotropy of the Roller Compacted Concrete (RCC) for Pavement

The roller compacted concrete (RCC) is supposed to be isotropic, whereas the compaction of this material, which is achieved using the same machines used for the soil, appears only unidirectional, making the RCC an anisotropic material. In this experimental work, the influence of the phenomenon of compaction on the isotropy of the RCC is studied. This study was carried out through an evaluation of the compressive strengths and ultrasonic tests which were used for measurements of the elastic modulus and the dynamic Poissons ratio of the RCC as well as a qualitative judgement of the RCC aspect at the hardened state. The results of this work proved the anisotropy of the RCC and they showed the sensitivity of the mechanical strengths and the elastic modulus to the compaction direction.