This document discusses sulfur infiltrated concrete (SIC), which is produced by immersing cured concrete specimens in molten sulfur to infiltrate the pores. SIC has significantly higher strength and durability compared to normal concrete. It can be used for precast elements like roofing, fences, pipes, and railway sleepers where fast curing or acid resistance is needed. The production process is simple and inexpensive, involving drying the concrete then submerging it in molten sulfur with or without vacuum. SIC shows large increases in compression and tensile strength, as well as improved elastic properties, freeze-thaw resistance, and acid resistance compared to normal concrete.
3. Table Contents
1. Introduction
2. Abstract
3. Production of Sulphur Infiltrated Concrete (SIC)
4. Observation of the production Result
5. Uses of Sulphur Infiltrated Concrete (SIC)
6. Durability of Sulphur Infiltrated Concrete (SIC)
7. Application Of Sulphur Infiltrated Concrete (SIC)
4. Introduction
Sulfur concrete is a composite construction material, composed mainly of sulfur and aggregate
(generally a coarse aggregate made of gravel or crushed rocks and a fine aggregate such as sand).
Cement and water, important compounds in normal concrete, are not part of sulfur concrete. The
concrete is heated above the melting point of sulfur ca. 140 °C. After cooling the concrete reaches
a high strength, not needing a prolonged curing like normal concrete. Sulfur concrete is resistant
to some compounds like acids which attack normal concrete. Sulfur concrete was developed and
promoted as building material to get rid of large amounts of stored sulfur produced by
hydrodesulphurization of gas and oil. Sulfur concrete is also a possible building material for a
lunar base. As of 2011, sulfur concrete has only been used in small quantities when fast curing or
acid resistance is necessary.
5. Abstract
Research has been done at the Mines Branch for the purpose of producing concretes with high
strength at early ages at a price competitive with conventional concrete or cheaper. Expensive
monomers that require high pressure to impregnate the concrete were ruled out. Instead,
simple and effective procedures for using cheaper materials such as sulfur were sought. Some
of the results obtained up to now are given here. The work has resulted in a new type of high-
strength concrete made from lean, two-day old conventional concrete, using sulfur infiltration
technique. In the laboratory the method has consisted of moist-curing fresh concrete
specimens for 24 hours, drying them at 250 degrees F for 24 hours, immersing them in molten
sulfur under vacuum for two hours, releasing the vacuum and soaking them for an additional
half hour, then removing them from the sulfur to cool. They are tested one to two hours later.
In a simplified version of the above process, vacuum is eliminated and immersion time is
molten sulfur is increased to four hours. Phenomenal increases have been obtained in the
mechanical and elastic properties of sulfur-infiltrated specimens. The compressive strengths
increased about ninefold over those of the reverence moist cured specimens, which were about
1000 psi. A corresponding increase was observed in the flexural strength of the infiltrated test
prisms. Sulfur-infiltrated concrete should have applications in pavements, bridge decks, and
many precast products.
6. Production of Sulphur Infiltrated Concrete (SIC)
Sulphur infiltrated concrete was developed as an economical alternative to polymer impregnated
concrete (PIC) to be used for higher strength and durable precast elements. Sulphur is
considerably cheaper than polymers and the technique of impregnation is more simple. These
factors result in cost benefits.
The concrete to be infiltrated should be produced using normal aggregates with aggregate/cement
ratios between 3:1 to 5:1. The water/cement ratio should be high between 0.7 and 0.8. The size of
coarse aggregate should be 10 mm and below. It should be well graded. The fine aggregate
should be of good quality. Sulphur also should be of high purity of 99.9%.
7. Procedure 1
After moist curing of elements for 24 hours at about 23°C, they are dried at 121°C to 125°C
for another 24 hours. After drying, the specimens arc immersed in molten Sulphur at 121°C
under vacuum for 3 hours. The specimens are removed from container, wiped clean of Sulphur
and allowed to cool to room temperature for one hour and weighed to determine the weight of
Sulphur infiltrated in concrete.
The period of immersion depends upon the type and size of the member. For lean concrete the
period of immersion is 2 hours under vacuum. After this period the vacuum is released and the
specimens are soaked for an additional half an hour in the molten Sulphur under atmospheric
pressure. After this period the elements are removed from the molten Sulphur wiped clean and
allowed to cool. It is weighed to determine the weight of Sulphur infiltrated in concrete.
In case of low water/cement ratio concretes which are relatively dense, external pressure is
applied after the release of vacuum to force Sulphur into the concrete. The above procedure
may be modified to suit the individual job conditions.
8. Following points should be kept in mind :-
1. For concretes with a water/cement ratio of the order 0.65, the one day old elements must be
handled with care to avoid damage.
2. The drying temperature should be kept as high as possible, but not exceeding 150°C, as the
higher temperature may damage the gel structure of the young hydrated cement paste. The period
of drying will depend on the type and size of the element.
3. The period of vacuum (evacuation time) appears to be less critical than the immersion time in
molten Sulphur after evacuation. For concretes with water/cement ratio of about 0.55 increased
immersion times is essential to achieve full infiltration.
9. Procedure 2
In this case, the dried concrete specimen is placed in an air tight container and subjected to
vacuum pressure of 2 mm of mercury for 2 hours. After releasing the vacuum, the specimens
are soaked in the molten sulphur at atmospheric pressure for another half an hour. The
specimen is taken out, wiped clean, cooled to room temperature for about an hour. The
specimen is weighed and the weight of sulphur impregnated in concrete is determined.
The specimens made by both the procedures are tested in compression and tension by
splitting method.
10. Observation of the production Result
1. The compressive strength of Sulphur infiltrated specimens (cubes and cylinders) is enormously
higher than the strength of plain moist cured specimens. It is found that with water/cement ratio
0.7, the increase in compressive strength of cubes prepared by procedure B is found about 7 times
higher. With the use of 0.8 water/cement ratio, cubes prepared by procedure B gave about 10
time’s higher strength.
2. Similarly specimens prepared by procedure B gave more than 4 times increase in splitting
tensile strength.
3. The elastic properties of Sulphur infiltrated concrete improved by 100%.
4. Sulphur infiltrated concrete showed a very high resistance to freezing and thawing. The
Sulphur infiltrated concrete was found in good condition even after 1230 cycles when prepared
by procedure B, while plain moist cured concrete disintegrated after about 40 cycles. Concrete
made with procedure A, deteriorated after about 480 cycles.
11. Uses of Sulphur Infiltrated Concrete (SIC)
The techniques of production of this concrete are simple, inexpensive and effective. The
attainment of strength in about 2 days makes this process all the more attractive.
As the high strength of concrete can be achieved in a very short interval of time, the sulphur
infiltrated concrete can be used for the manufacture of precast roofing elements, fencing posts,
sewer pipes and railway sleepers. It can also be used in industry, where high corrosion
resistant concrete is required.
However this method cannot be employed conveniently to cast in-situ concrete. Further it has
been observed that the sulphur infiltrated pre-cast concrete units are cheaper than normal
concrete. The added cost of sulphur and process may be offset by the savings in the concrete.
12. Durability of Sulphur Infiltrated Concrete (SIC)
1. The performance of the sulphur infiltrated concrete generally has been found satisfactory
against freezing and thawing, sea water attack, wetting and drying conditions.
2. It is more durable than conventional concrete in high concentrations of H2SO4 and HCL.
3. The strength properties are not significantly affected when exposed to short term temperatures
upto 100°C. At these temperatures it shows certain amount of ductility before failure.
4. The increase in abrasion resistance depends on the sulphur loading in the concrete. The sulphur
filling of the pores of the concrete provides an un-interrupted path for heat flow resulting in
increased thermal conductivity over that of normal dry concrete.
5. This concrete provides a corrosive protection cover to the embedded steel. The sulphur loading
required for a given corrosive protection depends upon the water/cement ratio used in the
concrete. Higher the water/cement ratio, higher the sulphur loading required. The minimum
sulphur loading for 0.7 water/cement ratio is 10% and for 0.4 water/cement ratio 5% sulphur
loading is sufficient.
6. When left in stagnant water for a long time, slight leaching of sulphur has been observed and
the concrete showed undesirable expansion followed by cracks.
13. Application Of Sulphur Infiltrated Concrete (SIC)
1. Precast roofing element , fencing posts , sewer pipes
2. Railway sleepers
3. For industrial application , where high corrosion resistance is required
4. Precast concrete units are cheaper than commercial concrete