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111. Brich>Zt_i, yns ~ac:rAaA'f1c~ti <br />3.01 General <br />Backt3ll mix preparation was performed in a geoteehnical testinz laboratory. Proportions of <br />coarse alluvium, overburden, dry bentonite, and dry cement were based on dry wei,hts. Prior <br />to creating backfill mixes, the laboratory determined the mois[ure content of the coarse <br />alluvium and overburden so that the correct proportions were mixed. <br />3.02 Bentonite Shtrrv <br />Two different bentonite slurries were created during the SCB baekfill mix design process. <br />The Clrst slurry was created by mixing the dry benronite powder with the designated site <br />water described in 2.02.A. The standard slurry was created according to API Specification <br />13A. The bentonite was then allowed [o completely hydrate for 16 hours Separation of the <br />s(urr}' was apparen[. A second slum vas prepared by treating the pond water as described in <br />dte next section. Table V summarizes the properties of this bemonite slurry. <br />3.03 Water fireutment <br />The site water was treated with soda ash to reduce water hardness in order to mitigate slurry <br />separation. Sada ash provided by ATT was introduced co the site water until a pH of 8.~ was <br />achieved. <br />3.04 Soil-Cement-Bentmtite ~lix <br />One SCB mix was prepared for performance testing. The design of this mix was to have 30 <br />percent fine rnaterial (passing the No. ?OU sieve} in the soil portion of the mix and 5.{7 <br />percent cement in the overall SCB mix. Table V shows the proportions of components in <br />each mix. Components were thoroughly blended into the mix using ahand-held electric <br />mixer. Initially, coarse alluvium, overburden, dry bentonite, and bentonite slurry were <br />mixed together until a 4 to b inch slump was achieved. Dry cement evas then added into the <br />mix. :~ddhional sturrv was added [o achieve a ~ tv 7 inch slump. Samples from each mis <br />were cast simuttaneously into cylinder containers (4 inch by 4 inch (diameter by length), 4 <br />inch by 8 inch, and b inch by IZ inch) for [esting. <br />- ~ r; PRtll PC LS=: 0-~~ •evVwi, ...~, tr_~,: ~ ~„5~,,, ~:i_..i_n +.~~-:n-tlR RGPJSi d~~c <br />q;:l: il' <br />