Exposure of concrete to high temperatures affects its mechanical properties by reducing the compressive strength, bending… etc. Factors reducing these properties have been focused on by several studies over the years, producing conflicting results. This article interested an important factor, that is the type of aggregates. For this, an experimental study on the behavior of concrete based on different types of aggregates: calcareous, siliceous and silico-calcareous subjected to high temperatures. In addition, the particle size distribution of the aggregates was chosen to be almost identical so that the latter does not affect the behavior of the concrete. Aggregates and concrete samples were subjected to a heating/cooling cycle of 300, 600 and 800 °C at a speed of 1 °C/ min. The mechanical and physical properties of concrete before and after exposure to high temperatures were studied. In addition, a microstructural study using a scanning electron microscope and a mercury porosimeter was performed. Thus, a comparative study between various researches on the mechanical properties of concrete exposed to high temperatures containing different types of aggregates was carried out.
The compressive strength test results showed that the concrete based on siliceous aggregates (C-S) has better mechanical performance up to 300 ° C. However, above 300°C, the compressive strength decreases faster compared to calcareous-based concrete (C-C). According to the mercury porosimeter test, at 600 ° C, C-SC and C-S concretes have the highest number of pores compared to C-C concretes. The microstructure of concrete at high temperatures was influenced mainly by the aggregate’s types and the paste-aggregate transition zone.
This study reinforces the importance of standardizing test procedures related to the properties of concrete in a fire situation so that all the results obtained are reproducible and applicable in other research.
The building industry is increasingly using self-compacting concrete (SCC) in order to improve many aspects of buildings construction. If the limestone filler is traditionally used in the SCC, marble powder and granulated blast furnace slag are the less. The valorization of such wastes in self-compacting concrete as mineral admixture could be an interesting ecological and economical alternative, which allow extending the use of these by-products. The objective of this study is not only to remove the fear of using by-products available locally but also to study the influence of limestone powder replacement by marble powder and granulated blast furnace slag on fresh and hardened properties of SCC under two different curing modes. For this purpose, a comparative study was conducted on a reference SCC with limestone's filler (SCC LP) which was replaced by marble powder (SCC MP) as a calcic material and granulated blast furnace slag (SCC GBFS) as a pozzolanic material. At fresh state, the slumpflow test, T 500 test, V-funnel, air content and L-box test were conducted to characterize the workability of fresh concrete in order to assess filling and passing abilities according to the European guidelines. The hardened properties that were determined included compressive and tensile strength determined at 3, 7 and 28 days. Monitoring the evolution of total shrinkage and weight changes up to 120 days were performed. As well the relationship between the shrinkage and weight loss. All SCC mixtures showed compliance with European recommendations (EFNARC). Considering the results obtained by various byproducts, the most edifying is the performance acquired by GBFS samples, for both modes of curing. Regarding the SCC MP, the results are satisfactory and this promotes their extension in Algeria.
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