Sulfur infiltrated test specimens

These tests indicated that sulfur-infiltrated concrete still loses abundant sulfur when immersed in neutral and sulfatic solutions, even though the reaction is localized and relatively slow. Compression tests of a few cylinders showed there had been little reduction in strength over several months. Examination of sawn surfaces revealed no clearly leached zone, but the specimens had turned a mottled blue, except near the center. Faint peripheral fractures had developed, and coherence of the infiltrated matrix near the surface had decreased, suggesting that some leaching had taken place. 

A Study of Leaching of the Infiltrated Concrete. The distilled water experiments provided the most information for examining the reactions involved in the leaching of sulfur-infiltrated concrete in aqueous media. Products selected from the specimens were analyzed, and the experiment was continued in a controlled environment. One specimen was partly immersed in distilled water under a nitrogen atmosphere. Fragments of the concrete were also sealed in a test tube. 

Infiltration of the permeable concrete with molten sulfur yields a matrix which is almost impermeable to water. The freeze-thaw durability tests have indicated this is so, and immersion tests showed that fully infiltrated specimens absorbed less than 0.3% water by volume over several months, although methanol immersion and vacuum poro-simeter measurements revealed that a pososity of over 5% was available for filling. A total shrinkage of about 13% (Table I) occurs when liquid sulfur crystallizes to the stable low-temperature S< form, but much of the volume change appears to be accommodated in closed pores and intercrystal inversion fractures which affect the permeability little. 

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