Sulfur compressive strength

The engineering properties of aggregate mixtures employing elemental sulfur as a binder are not suitable for highway pavement applications such mixtures possess adequate compressive strength, but are extremely brittle and lack satisfactory fatigue behavior to resist repetitive traffic loading. 

Compressive strength (Figure 6) of sulfur has a very high initial figure falling to a level at about 7000 kNm 2. The modified materials have much lower values, which with the lower levels of additive (5 and 10% styrene), increase rapidly after approximately two weeks, presum-... 

Figure 6. Compressive strength vs. log time plots of modified sulfur materials. Samples are identified by percentage of modifier used (w/w sulfur) and heating time, (a) Sulfur (b) 10% styrene, 3 hr (c) 5% styrene, 3 hr (d) 25% myrcene, 0.8 hr (e) 10% dicyclopentadiene, 3 hr (f) 25% dicyclopentadiene, 3 hr.

Figure 7. Comparison of the ratio between the flexural strength and the compressive strength of cement concrete and sulfur concrete...

In examining the strength properties of sulfur concrete modified with styrene, the compressive strength was insufficient and worse than in the case of unmodified sulfur concrete (Table VI). After 70 days storage, however, the compressive strength of the test samples modified with 10 wt % styrene increased to 432 kp/cm2, which is an average of 46%. The increase in the test samples modified with 5 wt % styrene was 4%, corresponding to a value of 526 kp/cm2. 

Figure II. Compressive strength of sulfur concrete samples made with basalt and granulit aggregate vs. the DCP content...

Figure 12. Compressive strength vs. flexural strength of sulfur concrete samples with different DCP content in the binder...

As shown in Table VIII, about the same compressive strength can be reached with DCP-modified sulfur concrete as with polyester concrete. The temperature loading lies in about the same range in both cases. 

Figure 4. Relation between sulfur loading and compressive strength of sulfur-infiltrated concrete. Wide scattering at higher loadings suggests variable porosity and/or inconsistent filling.

Figure I. Variation in compressive strength of sulfur mortars with hydrogen sulfide content before mixing (18)...

Figure 4. Variation in compressive strength with specimen size for raw sulfur and a sulfur pyrrhotite concrete mean and standard deviation of...

The first test, installed on a section of Dempster Highway about 40 miles south of Inuvik in the Northwest Territories, was designed for permafrost protection. The 45-ft wide and 130-ft long sulfur foam test pad averaged 4.4 in. in thickness and 11 lb/ft3 in density, with an average compressive strength of 46 psi. The foam was installed on top of the 1.5-ft thick pioneer fill and then was covered with 3.5 ft of granular overfill, in this case ripped shale, to complete the road section. 

Sulfur foams with a wide spectrum of properties can be prepared by this process. Properties generally vary with density, which may range from 3 to 45 lb/ft3. However, while density is kept constant, properties such as compressive strength, flexural strength, and closed-cell content may be altered by formulation changes. Some of the more common properties are listed in Table II. 

Construction applications for sulfur have also been tested. Interlocking bricks made predominantly of sulfur have been found to speed up construction, but have inherent fire hazards, which restrict their use. Concrete blocks impregnated with molten sulfur have shown a more than tenfold increase in compressive strength, from 5.9 to 83.9 MPa (megapascals 1 MPa = 10 N/m ), at the same time as an improvement in tensile strength from 1.3 MPa to 8.5 MPa, for a 13-15% sulfur content [7]. It also improves its chemical resistance. Sulfur-coated bamboo has been found to be an economical yet effective concrete reinforcing agent as a replacement for steel, in areas where bamboo occurs naturally. 

The additives were thiurarn-D and Altax . Optimum quantity of the additives in the RubCon composition was obtained by a two-factor experiment. In this case, the dosage of the additives was the varied parameter and the compressive strength of RubCon test specimens was the efficiency function. Figure 2.58 shows the efficiency function surface for RubCon samples in a 36% solution of hydrochloric acid, depending on the quantity of additives sulfur + thiuram-D (x,) and Altax (x2). 

The regression formula for the relationship between RubCon compressive strength R and quantities of additives (x1 = sulfur + thiuram-D and x2 = Altax) is... 

FIGURE 2.58 Compressive strength of RubCon samples relationship between quantities of Altax and sulfur + thiuram-D after exposition in 36% solution of a hydrochloric acid. (Reprinted from Yu. Potapov, Yu. Borisov, V. Chmyhv, and D. Beilin, Research of Polymer Concrete Based on Low Molecular Polybutadiene, Part VIII Chemical Resistance of Polymer Concrete, J. Scientific Israel Technological Advantages 7, nos. 1-2 (2005) 72-78. With permission.)... 

One can see that after 180 days of exposure of RubCon in aggressive environments, its compression strength decreased 22% in a 36% solution of hydrochloric acid, 8% in a 5% solution of a phosphoric acid, 7% in a 70% solution of a sulfuric acid, and 16% in a 25% solution of NH4OH. 

The analysis of obtained results show that the strength of the RubCon samples immersed in inorganic acids increased during the first 10 days (Table 2.11). For this period, compression strength increased by 7% in the 36% solution of a hydrochloric acid, by 9% in the 5% solution of a phosphoric acid, and by 8% in the 70% solution of a sulfuric acid. 

While considerable work was conducted by Southwest Research Institute (2, 3) to develop sulfur-aggregate mixtures, tests were also conducted on the effects on compressive strength of adding sand to sulfur to determine its utility as a mortar material. Two mortar sands of different particle size distributions were used with the sulfur to produce 1-in. cube compression test specimens. Particle size distributions are presented in Table I. 

Figure 6 presents a comparison of the sulfur-sand mixture tests. Sand additions increase the compressive strength of the sulfur up to approximately 50 wt %. Based on these curves it would appear that 40-50 wt % of sand would produce the highest strengths. 

Table II. Compressive Strengths of Bright Sulfur—Sand Mixtures...

Figure 6. Effect of sand additions on compression strength of sulfur aged 1 day...

Tests were then carried out at 75 and 100/blows face. The improvement in compressive strength which then appeared for the pure asphalt binder was considerably less than that for products containing sulfur. With this type of granulometry it seems necessary to adjust the compacting conditions very carefully to obtain the best results. 

Table III. Compressive Strength of Sulfur-Additive Combinations0...

When equal proportions by weight of fly ash and sulfur were mixed, a strong porous solid was formed. The resulting material weighed 95 lb/ft3 and had a compressive strength of 1760 psi at 7 days. 

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