Determining Concrete Chloride Permeability Rapidly and Effectively

US Transportation Collection2018PDFTech ReportCrouch, L. K.Badoe, DanielDillion, SarahCrowley, AaronLocum, JamesEagan, BlakesleeSmith, CalebMohr, BenTennessee Technological University. Center for Energy Systems ResearchTennessee. Department of TransportationUnited States. Department of Transportation. Federal Highway AdministrationTennessee. Department of TransportationUnited StatesAdmixturesChloridesCompressive strengthConcrete curingFly ashPermeabilityPortland cementConcreteSlagAbsorptionResistance-chloride penetrationRES 2013-41019B268 (FHWA Project No.)August 1, 2013 to July 31, 2018A study was conducted to determine if chloride permeability could be determined more quickly and efficiently. Two mixtures were selected by the Tennessee Department of Transportation (TDOT) Materials and Tests (M&T) Division: a TDOT Class D mixture with 20% Class F fly ash and an experimental mixture containing 35% Grade 120 slag and 15% Class F fly ash. Five validation batches of each mixture were produced. The plastic and hardened properties of all validation batches of both mixtures met TDOT 604.03 Class D requirements. Subsequently, twenty batches of each mixture were produced for chloride permeability comparison. Rapid chloride permeability ((RCP) AASHTO T 277) was measured after 28 days of accelerated curing and also after 56 and 91 days of normal curing. Surface resistivity ((SR) AASHTO TP 95) was measured after 28 days of accelerated curing and also after 28, 56 and 91 days of normal curing. Additional data from other TTU studies was also used in the correlations and predictions. The correlation between SR and RCP was significantly different from the correlation based on AASHTO categories, but, on average, differed from AASHTO by less than 4%. Correlations between earlier and later age values of both SR and RCP were very strong (R2 > 0.9) for both accelerated and normal moist curing. The authors recommend that TDOT M&T: 1. Use SR instead of RCP for primarily logistical reasons. 2. Use normal curing rather than accelerated curing for primarily logistical reasons. 3. Specify minimum SR of 24 kilohm-cm after 28-days of normal curing. 4. Continue accumulating results from different Class D and experimental PCC mixtures.137