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Improved shear strength performance of compacted rubberized clays treated with sodium alginate biopolymer

- Soltani, Amin, Raeesi, Ramin, Taheri, Abbas, Deng, An, Mirzababaei, Mehdi

  • Authors: Soltani, Amin , Raeesi, Ramin , Taheri, Abbas , Deng, An , Mirzababaei, Mehdi
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Polymers Vol. 13, no. 5 (2021), p. 1-21
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  • Description: This study examines the potential use of sodium alginate (SA) biopolymer as an environmentally sustainable agent for the stabilization of rubberized soil blends prepared using a high plasticity clay soil and tire-derived ground rubber (GR). The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three soil–GR blends (with GR-to-soil mass ratios of 0%, 5% and 10%) compacted (and cured for 1, 4, 7 and 14 d) employing distilled water and three SA solutions—prepared at SA-to-water (mass-tovolume) dosage ratios of 5, 10 and 15 g/L—as the compaction liquid. For any given GR content, the greater the SA dosage and/or the longer the curing duration, the higher the uniaxial compressive strength (UCS), with only minor added benefits beyond seven days of curing. This behaviour was attributed to the formation and propagation of so-called “cationic bridges” (developed as a result of a “Ca2+/Mg2+

Reappraisal of the astm/aashto standard rolling device method for plastic limit determination of fine-grained soils

- Soltani, Amin, O’Kelly, Brendan

  • Authors: Soltani, Amin , O’Kelly, Brendan
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Geosciences (Switzerland) Vol. 11, no. 6 (2021), p.
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  • Description: Given its apparent limitations, various attempts have been made to develop alternative testing approaches to the standardized rolling-thread plastic limit (PLRT) method (for fine-grained soils), targeting higher degrees of repeatability and reproducibility. Among these, device-rolling techniques, including the method described in ASTM D4318/AASHTO T90 standards, based on original work by Bobrowski and Griekspoor (BG) and which follows the same basic principles as the standard thread-rolling (by hand) test, have been highly underrated by some researchers. To better understand the true potentials and/or limitations of the BG method for soil plasticity determination (i.e., PLBG), this paper presents a critical reappraisal of the PLRT–PLBG relationship using a comprehensive statistical analysis performed on a large and diverse database of 60 PLRT– PLBG test pairs. It is demonstrated that for a given fine-grained soil, the BG and RT methods produce essentially similar PL values. The 95% lower and upper (water content) statistical agreement limits between PLBG and PLRT were, respectively, obtained as −5.03% and +4.51%, and both deemed “statistically insignificant” when compared to the inductively-defined reference limit of ±8% (i.e., the highest possible difference in PLRT based on its repeatability, as reported in the literature). Furthermore, the likelihoods of PLBG underestimating and overestimating PLRT were 50% and 40%, respectively; debunking the notion presented by some researchers that the BG method generally tends to greatly underestimate PLRT. It is also shown that the degree of underestimation/overestimation does not systematically change with changes in basic soil properties; suggesting that the differences between PLBG and PLRT are most likely random in nature. Compared to PLRT, the likelihood of achieving consistent soil classifications employing PLBG (along with the liquid limit) was shown to be 98%, with the identified discrepancies being cases that plot relatively close to the A-Line. As such, PLBG can be used with confidence for soil classification purposes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

An objective framework for determination of the air-entry value from the soil–water characteristic curve

- Soltani, Amin, Azimi, Mahdieh, Boroomandnia, Arezoo, O'Kelly, Brendan

  • Authors: Soltani, Amin , Azimi, Mahdieh , Boroomandnia, Arezoo , O'Kelly, Brendan
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Results in Engineering Vol. 12, no. (2021), p.
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  • Description: The air-entry value (AEV) suction, marking the transition between saturated and unsaturated soil mechanics, is arguably the most important parameter interpreted from the soil–water characteristic curve (SWCC); its accurate determination being essential for the prediction of unsaturated soil properties. The AEV is commonly obtained by a subjective and time-consuming graphical construction. This micro-article proposes an objective framework, developed based on a practical mathematical translation technique, for the AEV determination. Explicit equations for the AEV are derived based on eleven well-established SWCC fitting functions, covering a wide range of functional complexities. In addition to its objective nature (providing unique interpretations of the AEV), the proposed framework complements numerical implementations of unsaturated soil constitutive models. © 2021 The Author(s)

Mechanical performance of tire-derived aggregate permeable pavements under live traffic loads

- Raeesi, Ramin, Soltani, Amin, King, Russell, Disfani, Mahdi

  • Authors: Raeesi, Ramin , Soltani, Amin , King, Russell , Disfani, Mahdi
  • Date: 2022
  • Type: Text , Conference paper
  • Relation: 4th International Conference on Transportation Geotechnics, ICTG 2021 Vol. 164, p. 515-528
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  • Description: Traditional pavements in urban areas are mainly rigid, impervious surfaces, resulting in augmented surface run off during rainfalls, thereby leading to flash-flooding and pollution of waterways. In comparison, permeable pavements permit percolation of water through surface layers, thus alleviating harmful environmental impacts. This study presents the authors’ recent experience in the development of an instrumented large-scale permeable pavement trial site—constructed using a combination of crushed rock (CR) and tire-derived aggregate (TDA), bonded by a polyurethane (PU) binder—located at a car park in South Australia. An area of approximately 400 m2 was paved using different TDA-based mix designs—different CR sizes, colors, and shapes, and different PU contents. Moreover, preliminary field performance monitoring results—including surface deflection measurements by the light weight deflectometer test, and strain measurements using optic fiber and strain gauge sensing techniques—are outlined and discussed in detail. The strength and stiffness of the TDA-based blend was found to be dependent on the TDA content, TDA-to-CR size ratio, CR shape, and PU content. The greater the angularity of the CR particles, the more effective the interlocking of the TDA and CR components, and thus the higher the developed strength and stiffness. The amount of strain generated in the permeable surface layer and at its interface with the lower screening layer were both found to decrease with a decrease in TDA content. Preliminary field observations indicate that the TDA-based system can indeed be a viable (and sustainable) solution to effectively mitigate flash-flooding while sustaining low–medium traffic loads. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Modeling the compaction characteristics of fine-grained soils blended with tire-derived aggregates

- Soltani, Amin, Azimi, Mahdieh, O’Kelly, Brendan

  • Authors: Soltani, Amin , Azimi, Mahdieh , O’Kelly, Brendan
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Sustainability (Switzerland) Vol. 13, no. 14 (2021), p.
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  • Description: This study aims at modeling the compaction characteristics of fine-grained soils blended with sand-sized (0.075–4.75 mm) recycled tire-derived aggregates (TDAs). Model development and calibration were performed using a large and diverse database of 100 soil–TDA compaction tests (with the TDA-to-soil dry mass ratio ≤ 30%) assembled from the literature. Following a comprehensive statistical analysis, it is demonstrated that the optimum moisture content (OMC) and maximum dry unit weight (MDUW) for soil–TDA blends (across different soil types, TDA particle sizes and compaction energy levels) can be expressed as universal power functions of the OMC and MDUW of the unamended soil, along with the soil to soil–TDA specific gravity ratio. Employing the Bland– Altman analysis, the 95% upper and lower (water content) agreement limits between the predicted and measured OMC values were, respectively, obtained as +1.09% and −1.23%, both of which can be considered negligible for practical applications. For the MDUW predictions, these limits were calculated as +0.67 and −0.71 kN/m3, which (like the OMC) can be deemed acceptable for prediction purposes. Having established the OMC and MDUW of the unamended fine-grained soil, the em-pirical models proposed in this study offer a practical procedure towards predicting the compaction characteristics of the soil–TDA blends without the hurdles of performing separate laboratory compaction tests, and thus can be employed in practice for preliminary design assessments and/or soil– TDA optimization studies. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Improving workability of cement paste backfill using new binders

- Taheri, Abbas, Zhao, Y., Soltani, Amin, Karakus M., Deng, A.

  • Authors: Taheri, Abbas , Zhao, Y. , Soltani, Amin , Karakus M. , Deng, A.
  • Date: 2019
  • Type: Text , Conference paper
  • Relation: 13th Australian New Zealand Conference on Geomechanics, 1-3 April 2019, Perth Australia
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  • Description: In this study effects of binder type and content and curing time on the compressive strength development of cement paste backfill (CPB) is investigated. Moreover, the effects of binder type and content and water content on the rheological properties of CPB material were studied. To undertake an experimental study, tailings of a copper mine in South Australia are mixed with binder and water. A new slag-cement called Mine Cement (MC) and ordinary Portland cement (PC) are used as the primary binder materials. Furthermore, fly ash (FA) is used as an additive to reduce the amount of the cement. Some CPB samples were cured under pressure to be more representative of the field conditions. MC exhibited better performance that PC regarding compressive strength development. Fly ash improved the compressive strength of CPB. However, this binder observed to be much less cementitious compare to MC. Strength performance of the CPB sample significantly improved when there were cured under pressure. Based on the results obtained from the test undertaken using a rheometer, it was found that increasing the water content results in lower yield stress. The results also show that MC improves the rheological properties of the CPB.

Reappraisal of fall-cone flow curve for soil plasticity determinations

- Soltani, Amin, O'Kelly, Brendan

  • Authors: Soltani, Amin , O'Kelly, Brendan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Geotechnical Testing Journal Vol. 45, no. 1 (2022), p.
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  • Description: Several attempts have been made to devise alternate plastic limit (PL) determination methods, targeting higher degrees of repeatability and reproducibility. Among these, empirical-type correlations linking the plasticity index (PI) to the flow index (FI) - the slope magnitude of the flow curve - seem to be gaining increased attention, particularly for the fall-cone (FC) approach, and hence demand further examination. To better understand the true potentials and limitations of this emerging practice for soil plasticity determination, this study presents a critical statistical appraisal of FI-based correlations - using a large and diverse database of 230 FC tests (for the 80 g-30° cone) - in estimating the PI (and hence the PL). It is demonstrated that the so-called "strong"correlation between the PI and FI reported in some literature, favoring the use of FI as a PI estimator, is an overlooked "statistical pitfall"originating from an over-reliance on the coefficient of determination (R2) statistic. Employing appropriate error-related statistics, it is shown that the PI predictions made by FI-based correlations are associated with high average errors of 22-33 %. Hence, such correlations, at best, can only provide a rough approximation of the actual PI (and hence PL). An attempt is also made to assess the validity of FI-based correlations in the context of soil classification using the Casagrande-style plasticity chart. The agreement level between the conventional classification approach and that performed using PI deduced from FI-based correlations was 75-80 %. This analysis, however, did not account for errors in the rolling-thread plastic limit data, maintaining a strong possibility that FI-based correlations may be suitable for routine soil classification purposes. © 2021 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

Intermittent swelling and shrinkage of a highly expansive soil treated with polyacrylamide

- Soltani, Amin, Deng, An, Taheri, Abbas, O'Kelly, Brendan

  • Authors: Soltani, Amin , Deng, An , Taheri, Abbas , O'Kelly, Brendan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Journal of Rock Mechanics and Geotechnical Engineering Vol. 14, no. 1 (2022), p. 252-261
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  • Description: This laboratory study examines the potential use of an anionic polyacrylamide (PAM)-based material as an environmentally sustainable additive for the stabilization of an expansive soil from South Australia. The experimental program consisted of consistency limits, sediment volume, compaction and oedometer cyclic swell–shrink tests, performed using distilled water and four different PAM-to-water solutions of PD = 0.1 g/L, 0.2 g/L, 0.4 g/L and 0.6 g/L as the mixing liquids. Overall, the relative swelling and shrinkage strains were found to decrease with increasing number of applied swell–shrink cycles, with an ‘elastic equilibrium’ condition achieved on the conclusion of four cycles. The propensity for swelling/shrinkage potential reduction (for any given cycle) was found to be in favor of increasing the PAM dosage up to PD = 0.2 g/L, beyond which the excess PAM molecules self-associate as aggregates, thereby functioning as a lubricant instead of a flocculant; this critical dosage was termed ‘maximum flocculation dosage’ (MFD). The MFD assertion was discussed and validated using the consistency limits and sediment volume properties, both exhibiting only marginal variations beyond the identified MFD of PD = 0.2 g/L. The accumulated axial strain progressively transitioned from ‘expansive’ for the unamended soil to an ideal ‘neutral’ state at the MFD, while higher dosages demonstrated undesirable ‘contractive’ states. © 2022 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences

Discussion of “Behaviour of a Foam Mixture as a Lightweight Construction Material” [Int J of Geosynth and Ground Eng (2021) 7(3), 51]

- O’Kelly, Brendan, Soltani, Amin

Experiments and dimensional analysis of waste tire-based permeable pavements

- Soltani, Amin, Raeesi, R., Disfani, M.

  • Authors: Soltani, Amin , Raeesi, R. , Disfani, M.
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Geosynthetics International Vol. 29, no. 3 (2022), p. 186-204
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  • Description: This study investigates the stress-strain response of a novel high-porosity semi-bound soft-rigid permeable pavement blend prepared using rock- and tire-derived aggregates (RDA and TDA) bonded by a polyurethane (PUR) binder. A series of unconfined compression tests were performed on 36 mix designs (with different RDA and TDA proportions, PUR contents and curing durations) to identify the variables governing the stress-strain response. The greater the TDA content, the lower the mobilized strength (UCS) and stiffness (E50), both following an exponentially-decreasing trend. Meanwhile, an increase in PUR content (i.e. increase in the number of inter-particle bonds) and/or curing duration enhanced the UCS and E50. Unlike the UCS which often achieved a stabilized state at seven days of curing, the development of stiffness extended into higher curing durations. Applying the dimensional analysis concept, a practical modeling framework was proposed and validated (using an independent database) for the UCS and E50, allowing these parameters to be simulated as a function of the blend's basic properties - that is, RDA (or TDA) content and its mean particle size, PUR content, curing duration, and dry density. The proposed models can be used with confidence for preliminary design assessments and/or semi-bound soft-rigid optimization studies. © 2021 Thomas Telford Ltd.

Stabilization of a highly expansive soil using waste-tire-derived aggregates and lime treatment

- Soltani, Amin, Taheri, Abbas, Deng, An, O'Kelly, Brendan

  • Authors: Soltani, Amin , Taheri, Abbas , Deng, An , O'Kelly, Brendan
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Case Studies in Construction Materials Vol. 16, no. (2022), p.
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  • Description: This study investigates the combined efficacy of waste-tire-derived aggregate (TDA) materials and hydrated lime on the compactability, compressive strength and swelling potential of a highly expansive soil from South Australia. A total of 21 mix-designs, covering a comprehensive range of soil–TDA–lime combinations, were examined through standard Proctor compaction, unconfined compressive strength (UCS) and oedometer swell tests. The mobilized UCS exhibited a ‘rise–fall’ behavior, peaking at 5% TDA content and subsequently decreasing (monotonically) for higher inclusions of TDA. Increasing the TDA mean particle size (from 1.67 to 3.34 mm) also contributed positively to the UCS development. Addition of TDA to the soil/soil–lime-blends produced notable reductions in the swelling potential; the reduction was primarily governed by higher TDA contents, and, to a lesser degree, for larger TDA mean particle sizes. However, the role of TDA particle size in reducing swelling was found to be more significant than that of enhancing the UCS. As expected, lime treatment of the soil–TDA blends provided major further improvements to the UCS and swelling potential reduction; the achieved UCS improvements being positively proportional to the lime content and curing time. In view of the experimental results, soil–lime blends containing TDA to soil–lime mass ratios of up to 10% (preferably employing coarse-sand-sized equivalent TDA) can be deemed as suitable choices (capable of adequately mitigating the swelling potential, while simultaneously enhancing the UCS). © 2022 The Authors
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