In recent years, there is enormous increase in the production of sulphur, especially in Canada. In Canada there is a problem to consume the large quantity of sulphur produced. This situation has led to use the sulphur as a low cost construction material for producing sulphur concrete and sulphur infiltrated concrete.
Sulphur concrete consists of sulphur, fine and coarse aggregate only. It contains neither cement nor water. It attains high strength at early age of the order of 35 MPa in 8 hours.
Mix Proportion of Sulphur Concrete:
For optimum strength and workability the typical mix proportions are as 20% sulphur, 32% fine aggregate and 48% coarse aggregate and 5% silica flour, which come as 1:1.6:2.4. The ratio of fine to coarse aggregate comes as 1:1.5. The grading of the aggregate should be as to give a minimum void content.
When a comparison of 1:1.6:2.4 sulphur concrete made with conventional port-land cement concrete of equal strength having proportions as 1:1.8:2.6 with water/cement ratio as 0.41, showed that sulphur concrete gained strength very rapidly and reached its ultimate strength in 6 to 8 hours under normal ambient temperature and humidity conditions where as normal port-land cement concrete attained its ultimate strength in about 1 year time.
Method of Production for Sulphur Concrete:
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Either of the following two methods may be adopted for the production of sulphur concrete:
Method No. 1:
In this method the powdered sulphur and aggregates are mixed in a conventional mixer provided with a heater. With the help of this heater, the temperative of the mix is raised rapidly to a temperature of 140°C. At this temperature the ingredients of the mix form a uniform mixture, which can be cast into moulds.
Method No. 2:
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In this method the coarse aggregate is preheated slowly to a temperature of about 180°C and then this aggregate is fed into a tilting drum mixer. Now a sufficient quantity of sulphur is put into the drum to coat the coarse aggregate. Then the fine aggregate is added followed by the remaining sulphur.
At this stage a workability agent such as silica flour is also added and the mixture is cast into the moulds or form. To allow for the contraction of sulphur on cooling in the mould or form, a little extra mixture is filled. After cooling the surplus concrete is removed by sawing.
Properties of Sulphur Concrete:
The physical and mechanical properties of sulphur concrete are as follows based on the work of Shri V.M. Malhotra.
Advantages of Sulphur Concrete:
Following advantages have been observed of sulphur concrete:
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1. As compared with port-land cement concrete, sulphur concrete gains strength very rapidly and attains about 90% of its ultimate strength in 6 to 8 hours under normal temperature and humidity conditions.
2. Sulphur concrete made with crushed aggregate gives much higher strength than made with natural gravel.
3. The strength values obtained from large specimens have been found lower. The decrease probably may be due to combined effect of specimen size and lower rate of cooling while in mould. This aspect of sulphur concrete can pose a serious problem for thick structural members.
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These advantages make the sulphur concrete suitable for use in pre-cast units for outdoor applications and its chemical durability makes it suitable for industrial plant use.
Disadvantages of Sulphur Concrete:
It has the following disadvantages:
1. It has a low melting point of 119°C with a consequential loss of strength.
2. It is vulnerable to combustion and produces toxic gases.
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3. It creeps more than port-land cement concrete.
4. It has poor resistance to freezing and thawing.
5. It produces corrosive effect on reinforcing steel under wet or humid conditions.
6. It is very brittle.
These disadvantages make the sulphur concrete unsuitable for most structural applications.