2013 Session: 664

• Long-Term Investigation into the use of New Rapid Hardening Cement for Controlled Low-Strength Materials to be Employed in Pavement Applications
  Abstract: Controlled low strength materials (CLSMs) are engineered, cement based materials of growing interest in all trench backfilling and bedding applications where low stiffness, strength and density are required. Although 50 years have passed since its first application, the technology has been the source of continuous innovation. The challenge today concerns the excessive and undesirable long-term gain in strength of current CLSMs available on the market which leads to difficulties in the event of future removal and to unbalanced stress strain behavior with surrounding soils.In this investigation, the authors present a long-term laboratory study aimed at the creation of new formulations for pavement applications with the objective of avoiding or limiting any gain in stiffness and resistance over time. For this purpose, a rapid hardening cement has been used as a substitute for Portland cement. The particular formulation of cement adopted presents many advantages in terms of rapid set, high early strength development and insignificant gain in strength over long periods. All the mixtures studied were subjected to static and dynamic triaxial tests taking the mechanical characteristics of a reference granular soil as the mix design target for new CLSM formulations. The results deriving from the use of different admixtures and mixing procedures in terms of mixing time, batching sequence and type of mixer were also investigated.
  Authors: Bertola, Federica; Bassani, Marco; Canonico, Fulvio; Bianchi, Manuela
  Authors: Bertola, Federica; Bassani, Marco; Canonico, Fulvio; Bianchi, Manuela
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-0509
  Practice-Ready: Yes
• Modeling the In Situ Performance of Cement Stabilized Granular Base Layers of Urban Roads
  Abstract: This study used a three dimensional non-linear orthotropic computational road model to measure the performance of reclaimed and recycled Portland cement concrete (PCC) aggregates and reclaimed asphalt pavement (RAP) aggregates stabilized with cement, as a base layer in a City of Saskatoon local road structure. The pavement structure used in this study was a typical City of Saskatoon local road structure, composed of 45 mm hot mix asphalt concrete (HMAC) on 225 mm granular base, built directly on top of in situ subgrade. The cross section was analysed with a conventional granular base layer as a baseline, and PCC and RAP base layers with two percent cement stabilization. The cement stabilized PCC and RAP base layers showed improved shear strain and horizontal strain behaviour when compared to the conventional granular base layer (which was not cement stabilized). This improvement confirms that cement stabilization of reclaimed PCC and RAP materials provides an enhanced primary response. This study demonstrated that typical thin COS pavement structures are highly dependent on base layer material constitutive properties. Stabilizing the PCC and RAP base layers with 2% cement reduced the maximum shear strains at the edge of the pavement structure by 12% and 25%, respectively, compared to the unstabilized conventional granular base layer. It is believed the increased fracture and cohesion of the residual cementitious materials inherent to recycled granular base, as well as cementitious binder added, improved the structural performance.
  Authors: Soares, Roberto; Haichert, Rielle; Podborochynski, Diana; Berthelot, Curtis F.
  Authors: Soares, Roberto; Haichert, Rielle; Podborochynski, Diana; Berthelot, Curtis F.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-0879
  Practice-Ready: Yes
• Development of Clegg Impact Value Thresholds for Minimizing Rutting of Cement-Treated Base Material Under Early Trafficking
  Abstract: In order to avoid early-age damage such as rutting, cement-treated base (CTB) materials must be allowed to cure before the pavement can be opened to early trafficking. One instrument shown to be effective in assessing the suitability of a CTB for early-age trafficking is the Clegg impact soil tester. In previous research, a Clegg impact value (CIV) threshold was proposed. That testing was conducted in northern Utah and consequently has limited application in other locations and with different CTB materials. Therefore, the objective of this research was to investigate the suitability of that CIV threshold in other conditions. Specifically, data were collected in Georgia, Texas and Idaho to supplement the Utah data. Following the field testing, the data were reduced on a site-specific basis, and CIV thresholds were selected for each site. The results indicate that the threshold is clearly a function of the 7-day unconfined compressive strength (UCS) of the CTB material, and a chart was developed to assist engineers with selecting appropriate CIV thresholds based on a specified 7-day UCS.
  Authors: Reese, G. Benjamin; Guthrie, W. Spencer
  Authors: Reese, G. Benjamin; Guthrie, W. Spencer
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-2299
  Practice-Ready: Yes
• Stabilization of High Sulfate Soils by Extended Mellowing
  Abstract: Using lime to stabilize expansive soils has been a preferred technique of practitioners for many years. However, heaving and premature pavement failures in lime-treated expansive subgrades containing sulfates led to the search for alternative stabilization techniques. Out of the several techniques developed, pre-compaction mellowing has potential to be effective in the stabilization of sulfate bearing soils. Yet this method still needs to be experimentally evaluated. In the current study, an attempt has been made to assess the stabilization effectiveness of pre-compaction mellowing on high sulfate soils. For this task, six natural expansive soils from the state of Texas, with sulfate contents varying from 200 ppm to 44,000 ppm, were collected. Soils with low sulfate contents were spiked with additional sulfates to make them high sulfate soils. Basic classification and chemical tests were performed to establish the clay mineralogy of the soils. Three different mellowing periods (0, 3 and 7 days) were studied. The test soils were treated with lime and allowed to mellow for the specified periods. Following the mellowing, the samples were subjected to three dimensional (3-D) volumetric swell, shrinkage and UCS tests. Reactive alumina and silica measurements were also attempted to study the consumptions of alumina and silica during sulfate-soil-lime reactions. It was observed that shrinkage was of no concern in treated soils since the shrinkage invariably reduced with lime treatment. In four of the six soils, pre-compaction mellowing successfully reduced sulfate-induced swell to a level below the natural expansive swelling. The UCS strengths of treated soils decreased slightly with mellowing. Reasons for the anomaly in UCS strengths and ineffectiveness of pre-compaction mellowing in two soils were explained.
  Authors: Puppala, Anand J.
  Authors: Puppala, Anand J.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-2709
  Practice-Ready: Yes
• Long-Term Investigation into the use of New Rapid Hardening Cement for Controlled Low-Strength Materials to be Employed in Pavement Applications
  Authors: Bassani, Marco
  Authors: Bassani, Marco
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-0509
• Modeling the In Situ Performance of Cement Stabilized Granular Base Layers of Urban Roads
  Authors: Soares, Roberto
  Authors: Soares, Roberto
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-0879
• Modeling the In Situ Performance of Cement Stabilized Granular Base Layers of Urban Roads
  Authors: Berthelot, Curtis
  Authors: Berthelot, Curtis
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-0879
• Stabilization of High Sulfate Soils by Extended Mellowing
  Authors: Puppala, Anand
  Authors: Puppala, Anand
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-2709
• Development of Clegg Impact Value Thresholds for Minimizing Rutting of Cement-Treated Base Material Under Early Trafficking
  Authors: Reese, G. Benjamin
  Authors: Reese, G. Benjamin
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 664
  Paper Number: 13-2299