Evaluation of Durability and Mechanical Properties of the Cement Mortar Added with Slag Blast Furnace

2015 
Abstract An evaluation of durability and mechanical strength in a cement mortar is presented in this work. A slag coming from steelmaking processes has been added to the mortar. This slag has similar properties to the ones of cement, and it has been added to the mortar in different proportions with two sizes of granulometry. With this addition, better properties against the action of sulfates are expected, and therefore, the presence of fracture and wear in the structures can be reduced. This allows more safety and increased life in the mortar, and the most important thing is that, this will contribute to decrease the environmental contamination because the slag used in this work is coming from the industrial waste, which is produced in big amounts in the steel sector worldwide. The studied materials are mortar cubes in which the mechanical strength has been evaluated. The dimensions of the samples are around 50×50×50 mm 3 and, according to the standard ASTM C109, these cubes should be evaluated during 1, 3, 7, 28, 56 and 118 days. The expansion tests to evaluate the sulfates attack is performed according to the standard ASTM C1012, in bars of around 25×25×285 mm 3 . These bars were submerged in water with lime and when the bars obtained a strength bigger than 20 MPa, they were also submerged in a sulfate solution, which was prepared 24 hours earlier with a pH that should be between 6 and 8. In this way, from the point of view of strength to sulfate attack, the mortar durability is evaluated by employing techniques such as X-ray diffraction, X-ray fluorescence and scanning electron microscopy, which allow us to determine the presence of different components that are responsible for the expansion as the formation of gypsum, ettringite, and thaumasite. As a result of this research, it is evident that slag with smaller particle size shows positive behavior against the action of sulfates, thus revealing minimum expansion percentages.
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