MECHANICAL PROPERTIES OF SULFUR CONCRETE

Abstract

Fossil fuel consumption is rapidly increasing in the world, and so is the amount of sulfur that is generated as by-product of the industrial refining process. Since sulfur is expected to increase continuously in the future, the huge cost of waste disposal will be required if there is no counterplan. As a result, using sulfur as construction materials such as asphalt and concrete was considered. However, sulfur concrete made with unmodified sulfur has limitation for practical use because it has inferior properties such as poor resistance to water and significantly more brittle than traditional concrete. In order to overcome these drawbacks, Modified sulfur was developed. Sulfur concrete using modified sulfur binders shows excellent durability in high acid or salt concentrations. This study investigated the mechanical and durability properties of sulfur concrete made with modified sulfur binder instead of Portland cement. Preliminary tests were performed to evaluate effects of the maximum size of coarse aggregate, the proportion of binder, aggregate, and modified sulfur binder, the replacement rate of SPB by fly ash on the workability, strength, and elastic modulus. 7 cases of specimens were tested with different types and sizes of aggregate, and various proportions of fly ash and SPB, to find several optimal mix proportions to minimize the amount of SPB with preserving workability. Compressive and tensile splitting strength tests were performed and elastic modulus of sulfur concrete was measured. For the specimens made with the maximum size of 19 mm, 13 mm, and 25 mm coarse aggregate, the average compressive strength was 76, 53, and 50 MPa, respectively. When the proportion of fly ash was increased to 5, 12, and 15% as a replacement of SPB, the compressive strength of sulfur concrete showed 76, 83, and 72 MPa, respectively. Therefore, the case with 19 mm coarse aggregate and 15% fly ash (by weight) presented the best mechanical properties. Based on the results of the preliminary tests, three types of specimens were tested to investigate the properties of sulfur concrete in severe environment, such as freezing and thawing resistance, coefficient of thermal expansion, and chemical resistance. In resistance test in acid and salt solution, The F case showed the most significant strength reductions, while the R case presented the smallest strength reductions in the three different solutions after immersion of 60 days. The average of the measured coefficients of thermal expansion of sulfur concretes is 15.26 × 10−6/˚C. This value is bigger than that of Portland cement concrete (10.0~13.0 × 10−6/˚C). The tested sulfur concretes presented high resistance to freezing and thawing. S- and F-type specimens made with natural aggregates had 84.6% of relative dynamic elastic modulus after 300 cycles of temperature change. However, R-type specimens made with recycled aggregates showed 77.6%.