Concrete, sulfur durability

Sulfur Impregnation (14). Stronger and more durable products such as Portland cement concrete, ceramic tile and even wood and paper products have been shown to be feasible. In addition, sulfur as an impregnant for fabric liner systems would have application in ponds, holding tanks, etc. 

Sulfur Coatings (1J>, 18). Molten sulfur, often mixed with fibers or modifiers can be used to spray coatings on unbonded block or brick buildings, linings for ponds, portland cement concrete, and other applications where a durable coating is required or useful. 

The improved performance of SC over PCC is of importance not only in the applications such as corrosive industrial situations, but also in certain regular construction applications. In some areas of the world, the mineral aggregates available locally do not produce a PCC capable of withstanding the climate conditions. However, those aggregates may be used in SC to give durable building materials. Examples of this aspect of the use of sulfur concretes are sulfur concrete block projects developed by Ortega... 

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. 

SUDICRETE (4 L). All sulfur concrete technologies involve an additive or modifier to increase durability by reducing the pro-... 

T or many years scientists and engineers have attempted to modify the properties of sulfur so that it might be of value as a construction material, but until recently these random efforts lacked direction. Frequently the objectives of work described in many published papers could not be reconciled with the experimental design. For example, authors cited availability, low cost, and low toxicity as reasons for evaluating sulfur as a construction material. The same authors would then proceed to modify sulfur with additives which were in short supply, expensive, and highly toxic. The aging characteristics of sulfur concretes beyond a 28-day period were never examined, and durability outside the laboratory environment was seldom considered. With these limitations, the data were of little value to the construction industry. 

The investigation of sulfur-infiltrated concrete at this laboratory included three major areas of study strength development and retention, resistance to freezing and thawing, and stability in various aqueous media. It was hoped that some conclusions could be drawn regarding practical manufacturing limitations, long-term durability in physically or chemically hostile environments, and potential usefulness of such concrete. 

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. 

Although these tests do support the long-established fact that infiltration 6f portland cement concrete with sulfur makes it more durable... 

The inherent instability of sulfur-infiltrated concrete in aqueous media illustrated in this study may be the most important factor in utilization, because it will affect long-term durability of the concrete in many natural settings. The Ca(OH)2 produced by the hydration of portland cement is a principal reactant in the leaching process, and while it remains sulfur could be extracted, leaving the matrix vulnerable to other destructive processes. The removal rate of sulfur will vary greatly, depending mostly upon the pH of the immersion medium thus, the concrete deteriorates in alkaline sulfatic soils but is relatively stable in the corrosive neutral sulfatic solutions from the sodium sulfate plant. 

Vacuum saturating and freeze-thaw cycling has a much greater detrimental effect on the ordinary asphalt concrete than on the sulfur-asphalt concrete. Indeed after soaking, the sulfur-asphalt concrete shows a slight increase in stiffness, and the freeze-thaw cycling causes only a slight decrease in stiffness. The sulfur-asphalt concrete thus appears more durable than its ordinary asphalt counterpart. 

It is clear that sulfur-asphalt concretes have better potential durability than their non-sulfur counterparts. However, knowledge of the... 

The air-void content of asphalt concrete mixes affects mix permeability and is therefore very important from a pavement durability standpoint. The permeability of various sulfur-extended binder mixes, prepared at a variety of air-void contents, was measured with an air permeameter similar to that described in Ref. 16. The results, presented in Figure 7, indicate that the sulfur-extended binder mixes exhibit an air voids vs. 

Concrete Coatings. The durability, weatherability, and chemical resistance of composites match up well with the required properties of protective coatings for concrete and other rigid materials. A typical application is the protection of concrete structures from the acid solutions used in metal ore leaching plants (9). In one such application, sulfur composite was applied to two leaching vats of a new experimental copper ore leaching facility (Figure 8). 

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