Abstract
Concrete durability is one of the most important concerns in the field of construction. The environmentally friendly materials that can provide the durability are of great value in the construction of concrete structures. The use of natural pozzolans is one of the cheapest and most efficient methods in this field, which offers a good performance from environmental and economic point of view and satisfies required engineering parameters. In this study, the effect of using natural pozzolan in the manufacture of concrete exposed to sulfate and chloride ion of Oman sea water was investigated. The Taguchi optimization method was used to reduce the number of samples prepared, reduce the cost of experiments and achieve an optimal mix design. The four parameters, namely water to cement ratio, different percentages of natural pozzolan, super-plasticizer and cement grade with different ratios, were considered as problem variables. The Taguchi optimization method proposed 8 mix designs based on the defined levels for the variables. By constructing 96 samples, two parameters of permeability and water absorption from Oman Sea and drinking water were investigated in the samples. By introducing the results of the experiments into the Taguchi method, the final optimal design was presented by this method, and by constructing 12 additional samples and conducting permeability and water absorption experiments, the behavior of this optimal mix design was verified. The appropriate performance of the Taguchi method was demonstrated by obtaining the optimal mix designs from the Taguchi method, constructing this mix design and comparing the results with the regulation limitations. The results showed that it is acceptable to use natural pozzolan under moderate to severe chloride and sulfate ion attacks, but it is not recommended in the extreme environmental conditions.
Highlights
Today, the use of natural pozzolans is of great importance due to the improvement of the concrete structure and the increase of concrete performance in aggressive environments considering the economic efficiency and environmental impacts
According to the graphs of water permeability and absorption test results, the higher the amount of pozzolan consumed, the greater the effect on the results of the water absorption test, but the permeability test graphs show that an increase in used pozzolan up to 20% has a positive effect on our results, but with a 25% substitution, we can see the reduced effect of added pozzolan on the permeability of the samples
The results show that the half-hour water absorption results did not change in the optimal Taguchi design compared to M7, the concrete permeability improved in the concrete made from the Taguchi optimal design
Summary
The use of natural pozzolans is of great importance due to the improvement of the concrete structure and the increase of concrete performance in aggressive environments considering the economic efficiency and environmental impacts. Pozzolanic materials are the most important factor in reducing the concrete permeability, which is achieved by TEHNIČKI GLASNIK 15, 1(2021), 69-75 reducing the volume of large cavities in concrete [6] To this end, a study conducted in Algeria by Kaid et al concluded that the use of Algerian natural pozzolans as a percentage of cement replacement can improve the parameters related to durability, corrosion and resistance to acidic environment [7]. Najimi and Ghafoori [13] find the most proper optimum using hybrid aluminosilicate precursors in alkali-activated concretes made with having different proportions of natural pozzolan (low calcium precursor) and blast furnace slag (high calcium precursor) Their experimental investigation shows that the optimum sodium hydroxide concentration was dependent on the precursor and. By comparing the optimum and laboratory values with the standards of the "National Concrete Durability Regulation in Oman Sea", the possibility of using this pozzolan in the construction industry was investigated for the coastal cities of the Oman Sea
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