Recommended Practice for Stabilization of Subgrade Soils and Base Materials (2009) / Chapter Skim
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From page 17... ...
15 capillary soak protocol, the sample is placed on a porous stone and wrapped in an absorptive fabric and allowed to absorb water through capillary rise until the moisture front ceases to move or for at least 24 hours. Additional Tests Involved in Stabilizer Selection Once an additive has been selected based on the index properties of plasticity index and percent of the soil mass smaller than 75μm, the possible impact of deleterious components of the soil must be considered.
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16 Soil Evaluation The first step in the NLA protocol is similar to the approach described in Figure 2 and in fact either the criteria described in Figure 2 or the criteria described in this section can be used. In this step, the soil fraction passing the no.
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17 are fabricated. However, if it is difficult to achieve satisfactory homogeneity during laboratory mixing, it is reasonable to consider a mellowing period (between initial mixing and final mixing before compaction)
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18 Extended Soaking for 8 Days (psi) Cyclic Freeze-Thaw 3 Cycles (psi)
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19 fines will be appropriately altered as well. However, it is prudent to test the plasticity of the minus no.
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20 understood, when extended mellowing is adopted, that all the strength lost during remixing may not be recovered with additional curing. Hardened soil cement mixtures must withstand adverse environmental conditions.
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21 These cement contents are only preliminary estimates and must be verified or modified based on additional test results. Additional cement requirement for soils with higher organic contents should be considered based on pH test of soil cement mixtures (6)
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22 cement modified soils. This method may also be considered an alternative method by which to assess the durability of cement stabilized soils.
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23 Cement Treatment of Base Courses The protocol described above addresses cement-soil and cement-base mixtures. However, in certain situations a lower level of cement is used to achieve a target increase in compressive strength and/or modulus for structural performance reasons.
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24 Mix Design Considerations Prior to stabilization, the cementitious properties of fly ash should be characterized following ASTM D 5239-04. But, it should be noted that ASTM D 5239-04 does not evaluate the interaction between fly ash and soil or aggregate which must to be verified separately based on mix design procedures outlined in the following paragraphs.
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25 typically vary based on objectives and requirements specified by the agency and these requirements should be followed in selecting the mix design for field application. Non Self Cementing Fly Ash For stabilization with non self cementing fly-ash, the addition of activators such as lime or cement is required to initiate stabilization reactions.
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26 preparation of three replicate samples for compressive strength testing for each blend of fly ash and activator. Curing of Samples for Compression and Durability Testing Fly-ash soil mixes are cured for 7-days in sealed containers.
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From page 29... ...
27 quantities of fly ash should be added to the blend beginning with four percent fly ash and increasing in two percent increments until acceptable strength is achieved. A separate moisturedensity relationship is required for each blend.
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