Wang found that when the temperature changes, S β will change to S α and during the transformation, due to the change of the crystal lattice, the volume of sulfur will shrink and the shrinkage stress will be formed inside the sulfur. Temperatures, researchers have carried out extensive research.īacon and Fanelli found that in the temperature from 120˚C to 200˚C, the viscosity of sulfur first decreases, then increases sharply until reaching the peak at near 190˚C, and then decreases. In order to understand the change of sulfur state and properties at differentįigure 3. With the variation of temperature, the phase changing diagram of sulfur is shown in Figure 3, in which each character is expressed as S α (Orthorhombic sulfur), S β (Monoclinic sulfur), S λ (Amorphous sulfur), S μ (Polymeric sulfur), S δ (Sulfur vapor). At different temperatures, different allotropes appear, and the properties of each allotrope are not the same. Therefore, the better change of sulfur state with temperature variation is the guarantee for the mixture to mix tightly and successful setting and hardening later. It is showed that sulfur needs to be melted at high temperature, and then mixed with other materials for pouring. General forming steps of SC are shown in Figure 2. Meanwhile, some conclusions are also included in this paper.ġ) Understanding of temperature variation This paper presents the research status of the modification in SC to generate some insights, including the understanding of variations in temperature, effects of molding methods and the addition of fillers and modifiers. But the modification theory is not very perfect. Many relevant researchers in civil engineering are making their constant efforts in this field. Hence, it is better to modify the SC to avoid its defects. Some fatal problems like stress concentration and structural depression will happen in SC-based construction projects due to these defects. However, the shortcomings of SC in the process of its application have been exposed including brittleness and large hardening shrinkage. Therefore, people are paying more attention to SC as the in-situ building materials of extraterrestrial planets. In addition, sulfur can be obtained from minerals on the surface of Mars, the moon and other extraterrestrial planets by chemical or physical methods, which reduces the workload and cost of transporting building cementitious materials from the earth to other planets. It can not only play a supporting role quickly but also directly melt in the heat after use, so as to achieve the result of more convenient removal and collection. Therefore, SC can be applied in some temporary structures like the bridge temporary support, which needs quick installation and removal. Once the temperature is raised to more than the melting point of sulfur, SC is easy to melt and be recycled. At room temperature, there is no need to keep the mixture curing to achieve enough compressive strength. After being heated and mixed, with the decrease of the temperature, SC will set and harden, and the speed of setting and hardening is very quick. Secondly, the melting point of sulfur, a kind of cementitious material, is generally not less than 110˚C. Compared with the common Portland cement concrete (PCC), it is more suitable for corrosion-resistant projects of chemical plants and ocean engineering. First of all, with strong corrosion-resistance, SC can resist the invasion of chemical corrosion effectively. With the deepening of research, SC is increasingly widely applied in the fields of construction engineering.īecause of its excellent properties, SC has application prospects in many aspects in construction engineering. In 1924, Kobbe proposed that concrete can be made from sulfur and other mixtures to make sulfur more suitable for conventional construction projects. In 1921, it was learned that sulfur can also be used as a binder in construction engineering. Sulfur has been applied in the fields of agriculture, medicine and rubber products industry. In Figure 1, it can be seen that although the surface of sulfur in the laboratory is slightly dim under the effects of light and ash deposition, it does not affect our conclusion that sulfur is light yellow. Sulfur is a kind of common chemical raw material whose chemical formula is S and it is a light yellow solid as shown in Figure 1 at room temperature.
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