and freeze-thaw resistance, whereas quartz aggregates give higher corrosion 

 resistance. The salts in chloride and sulfate- containing aggregates have 

 no effect on bonding, but some aggregates are unacceptable for SC because 

 they react chemically with the binder. Aggregates containing swelling 

 clays are also undesirable. 



(3) Mix Proportions . Design is normally for maximum compressive 

 strength, and based on the VMA (voids in mineral aggregate) procedure. 

 Optimum strength generally coincides with maximum workability and minimum 

 voids level. Coarse and fine aggregates blended to give about 25 percent 

 VMA were found to be optimal. In the finished SC, 4 to 5 percent voids 

 remained. These voids are not interconnected, and moisture absorption by 

 SC is very low, 0. 05 percent or less, whereas PCC often absorbs 3 percent 

 or more. This is an important factor in the resistance of SC to corrosion. 



Aggregate grading according to ASTM specification is unsatisfactory for 

 SC. From 6 to 1Q percent of fine (200 mesh) material should be included to 

 provide good workability. To prevent dusting, the fine material can be 

 mixed with the modified sulfur before it is added to the heated aggregate 

 in the mixer. 



(4) Properties and Uses . The quick curing characteristics of SC 

 make the material attractive in many situations. Eighty percent or more of 

 final strength is reached within a few hours of pouring, compared to 

 several weeks for PCC. Moreover, SC will cure equally well under freezing 

 conditions, which are highly detrimental to PCC curing. SC can tolerate 

 chloride and sulphate-containing aggregates found in desert areas, because 

 the bonding properties of sulfur are not affected by salts. The good heat 

 insulation characteristics of sulfur and the elimination of water in the 

 manufacturing process are two additional advantages of SC in desert areas 

 (The Sulphur Institute, 1979). 



(a) Fire Effects. The inherent flammability and low melting 

 point of sulfur impose some limitations of SC use. Flammability can be 

 controlled to some extent by the use of additives, and it is fortunate that 

 the DCPD types of additives used to improve the durability of SC also 

 impart a degree of fire resistance. Sulfur concretes are in any case 

 considerably less of a fire hazard than wood. Because of the low thermal 

 conductivity, heat penetration is slow, and SC can survive short exposures 

 to fire without serious damage. Sulfur concretes do not support combustion, 

 and flame spread is essentially zero. 



(b) Structural Use Limitations . The low melting point of 

 sulfur limits the use of SC in applications where loss of structural 

 strength in event of a fire could be catastrophic. Thus, SC for load- 

 bearing structures will probably not be used in high-rise apartment 

 buildings. However, the properties of SC appear to make it fully acceptable 

 for single-story dwellings, as well as for utility buildings and a wide 

 range of prefabricated structures. These materials are well suited to 

 specific uses in the coastal zone environment, and when used in a restricted 

 manner may resist coastal environments for many years. 



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