Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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42 NOVEMBER 2018 W W W.MATERIALSPERFORMANCE.COM like chloride or CO 2 , into the concrete and increase corrosion of rebar and spalling of the concrete cover. The aggregate used for manufacturing the H poles was tested for ASR according to ASTM C289-03. 10 According to Figure 2, the concrete aggregate was in a low-risk area of the ASTM C289 curve and the aggregates did not exhibit an ASR problem. Another effective factor in the forma- tion of high-strength concrete is the use of a dense grade of aggregate. Particle size analysis was done on the aggregate and a proposed concrete mix design is shown in Table 2. Table 2 also includes the concrete mix design, which was used previously for unmodified power poles. Concrete Test After making the changes as discussed previously, concrete samples were con- structed in accordance to the proposed concrete mix design mentioned in Table 2. Fur th er, som e samples were prepared according to the previous mix design (Table 2). The samples were cured for 28 days in water at 25 °C. Compressive strength and rapid chloride permeability (RCP) tests were performed on them. In most cases, the higher the compressive strength of con- crete, the longer the concrete durability when exposed to environmental condi- tions, with greater concrete density and lower permeability to corrosive agents. However, the RCP test was performed to confirm the increase in durability and decrease in permeability. According to Tables 3 and 4, concrete samples with mod- ified mix design had considerably higher compressive strength and lower electrical charge than the others. Concrete poles that have been constructed by the new mix design will have longer durability than the previous unmodified concrete pole in envi- ronmental conditions. Concrete Power Pole Test To ensure quality of the concrete poles, some of them were subjected to a bending test like that described in CEB Standard 044-3. 11 A comparison of results of the bending test of modified poles with the previous unmodified poles showed that the modi- fied poles had better acceptance bending behavior in the test, so it is reasonable to TABLE 2. MIXING DESIGNS Mix Designs Aggregate Cementous Material (kg/m 3 ) Water (kg/m 3 ) Super- plasticizer (kg/m 3 ) 0-6 mm Natural Aggregate (kg/m 3 ) 6-12 mm Natural Aggregate (kg/m 3 ) 6-12 mm Manufactured Aggregate (kg/m 3 ) 12-25 mm Manufactured Aggregate (kg/m 3 ) Cement Silica Fume Proposed 10-cm slump, dry aggregate 903 183 182 547 360 40 177 3.4 Previous low-durability H-type poles 1,145 199 — 558 350 — 209 — FIGURE 2 The aggregates were in a low ASR risk area of the curve of ASTM C289-03. MATERIALS SELECTION & DESIGN

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