Analysis of workability, mechanical strength and durability by the FT-IR method of concrete based on silica-limestone sand preserved in aggressive environments

The interest of using combined sand of equal percentage of silica and limestone becomes evident in the formulation of compacted concrete in several previous works around the world, due to the formidable percentage of fines that improves the compactness and increases various mechanical resistances, which produces a more durable construction against different probable aggressions. This paper examines the effect of using this type of sand on workability, compressive strength, flexural strength, and splitting tensile strength. A durability test was consulted using infrared spectroscopy to assess diverse types of hydration products formed. Found results clearly show the advantages of using sand with silica and limestone grains (50/50)% in ordinary concrete infected by aggressive water. There is also an improvement in compactness, different mechanical resistances, and a reduction in the formation of harmful hydration products

Effect of varying silica-limestone sand fines on the physical-mechanical performance of concrete

The use of crushed limestone sand in the concrete industry will be quite possible and imperative for environmental reasons. Many researchers around the world have found that concrete based on 50% substitution of river sand by limestone sand gives better physico-mechanical characteristics. The main objective of this investigation is to search for an optimal percentage of silica-limestone fines resulting from the substitution of half in quantity of alluvial sand by crushed limestone sand in ordinary concrete. The proportions of fines that were tested in this work are 6%, 8%, 10%, 12% and 14%. The obtained results revealed that concrete based on silica-limestone sand and containing 14% of the same type of fines strongly improves the different mechanical strengths and participates in the reduction of 10% and 13%, of the coefficient of capillary absorption and of the porosity accessible to water, respectively, compared to the control concrete. In addition, good statistical relationships between the studied parameters were also foun

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

Active control of the nonlinear bending behavior of magnetorheological elastomer sandwich beam with magnetic field

The purpose of this work is to analyze the nonlinear mechanical behavior of sandwich structures with a magnetorheological elastomer (MRE) core subjected to a permanent magnetic field. A detailed study is first carried out to characterize the mechanical behavior of these structures. The tests were carried out in three-point bending on beams of these complex materials for several distances between supports. An experimental study, of the mechanical behavior response realized using a Zwick 2.5 kN machine, allows to measure displacements as a function of force. The results deduced from the numerical simulation by the Abaqus software are compared with those obtained from the theoretical analysis. This study allows to show that these structures exhibit a non-linear behavior even at small deformations due to the rheological parameters which are more sensitive by the application of a magnetic field

THE EFFECT OF RECYCLED RUBBER AGGREGATES AND DUNE SAND OF EL-OUED REGION ON THE COMPRESSIVE STRENGTH OF CEMENTITIOUS MORTAR: OPTIMIZATION USING TAGUCHI METHOD

This study optimizes the effect of recycled rubber aggregates and dune sand of El-Oued's region by maximizing the compressive strength of cementitious mortar using Taguchi's design experiments. The experiments were designed using an L9 orthogonal array to see the different relationships between the factors targeted in our research, namely: water/cement (W/C) ratio, rubber aggregates (RA) content, and dune sand (SD) content, with the levels of each factor in the mortar mixture. The samples were tested at 28 days in each of the nine trial conditions for two responses: compressive strength and ultrasonic pulse velocity. The results of the analysis of variation (ANOVA) show that RA content is the factor that has the largest effect on the two tests, and the second factor affecting the two tests is the W/C ratio. Then, the analysis shows that the SD content has no significant effect on the mechanical resistance of the mortar for the two tests. And from the mathematical models investigated in this study, we conclude that the factors RA content and W/C ratio have a negative influence on the responses of the compression test and the ultrasonic test togethe

Délimitation du patrimoine urbain de la ville historique de Tlemcen en Algérie

Tlemcen is a city of art and history, which was built in Roman times. It was architecturally enriched over time with stylistic contributions of different dynasties. This city was ranked saved area in 2009 by executive decree. The geographical trace of this area affects only the Islamic medina Tagrart excluding the rest of the city. Therefore, we wondered about the real limits of this millenary city. For that, we traced its urban heritage by studying the stratification and characteristics of the urban fabric. This new geographical trace demonstrates the exclusion of many historic areas of the heritage classification.Tlemcen est une ville d’art et d’histoire qui a été édifiée á l’époque romaine. Elle s’est enrichie architecturalement á travers le temps avec les apports stylistiques des différentes dynasties. Cette ville a été classée secteur sauvegardé en 2009 par décret exécutif. Le tracé géographique de ce secteur ne touche que la médina islamique de Tagrart excluant le reste de la ville. De ce fait, nous nous sommes interrogés sur les véritables limites de cette cité millénaire. Pour cela, nous avons retracé son patrimoine urbain en étudiant la stratification et les caractéristiques des tissus urbains. Ce nouveau tracé géographique démontre l’exclusion de nombreuses zones historiques du classement patrimonial

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

Vibration control of a hydrostatic bearing using magnetorheological elastomer shell bearing

In rotating machines, random movements or sliding movements of the rotor in its housing can produce undesirable phenomena for some parts. To solve this problem, a new hydrostatic bearing with an intelligent magnetorheological elastomer sell bearing has been designed to control the undesirable vibrations of rigid rotors. The different effects of the influence parameters on the vibratory behavior of the sell bearing are calculated numerically using Abaqus software, and the results found are encouraging

Drought and water mobilization in semi-arid zone: The example of Hammam Boughrara dam (North-West of Algeria)

The dam of Hammam Boughrara is an embankment dam built in a transboundary basin, between Algeria and Morocco; it was type-approved and delivered in 1998. This dam was supposed to solve the lack of drinking water in Oran (Algeria's second largest city) and enhance the agricultural perimeter of the area. It should regulate an annual water volume of 59 million m3. However, the northwest Algeria has experienced a fairly severe drought since the 80s. This article aims to show the impact of this drought on the amount of surface water that can be mobilized by this dam. The rainfall series recorded at four stations, located within the basin of the dam, were examined using the proportional deviation from the average, the running average, the frequency analysis, the Pita’s index and the standardized precipitation index. These methods have shown a significant decrease of rain, starting from the hydrological year 1975/1976. These same approaches were also used to analyse series of flows spread over a longer period. This fact revealed three periods of drought which are 1940–1945, 1955–1967 and the most recent one highlighted by the rainfall series, starts at the year 1975/1976. The regularized water volume of the dam, calculated from the series of flow rates, is around 37 million m3. This value reflects a deficit of 40% of the regularized volume predicted by the designers of the dam