Laboratory Comparison of Crushed Aggregate and Recycled Pavement Material With and Without High Carbon Fly Ash

Abstract

In-place recycling of asphalt pavement materials is a sustainable rehabilitation method. Existing hot-mix asphalt (HMA) layer is pulverized and blended with some or the entire base course and possibly some subgrade to form a broadly graded material referred to as recycled pavement material (RPM). The RPM is then compacted as the new base course and overlaid by a new layer of HMA. In some occasions, additives are added to increase the strength of RPM base course, such as cement, emulsion, fly ash. It is plausible to utilize high calcium high carbon fly ash, as the high level of carbon prevents fly ash from being used in concrete. A series of laboratory tests were conducted to evaluate the performance of these materials, including crushed aggregate, untreated RPM, and treated RPM with high carbon fly ash. The tests included compaction, California Bearing Ratio, resilient modulus, and unconfined compressive strength for treated RPM. The engineering properties of these materials were compared.

Recent Development of Recycled Asphalt Pavement (RAP) Bases Treated for Roadway Applications

“…5a. The equation, CBR (%)=A*stabilizing agent (%)+B, was proposed in this study to predict the CBR of chemical-stabilized RAP specimens based on the test results obtained by Wen et al [33] and Cosentino et al [9]. The values of the parameters A and B obtained in this study are presented in Table 4.…”

“…The values for the model parameters (K 1 and K 2 ) are presented in Table 3. Li et al [20] conducted M R tests at a deviatoric stress of 21 kPa on a 14-day-cured fly ash-stabilized RAP specimens while Wen et al [33] conducted M R tests at a bulk stress of 83 kPa on 7-and 14-day-cured fly ash-stabilized RAP specimens. They found that the M R increased with an increase in the fly ash content and the curing period as shown in Fig.…”

“…[33]_7 days, and Wen et al [33]_14 days stand for 14-, 7-, and 14-day-cured fly ashstabilized RAP specimens, respectively. The variations in the properties of RAP, aggregate, and stabilizing agent may be the reason for the difference in the M R values determined by different researchers under similar conditions of stress, RAP content, and stabilizing agent content.…”

“…The CBR of RAP ranged from 3 to 17 % (mean=9 %), the CBR of the laboratory-mixed SRAP ranged from 70 to 95 % (mean=84 %), and the CBR of the field-mixed SRAP ranged from 13 to 53 % (mean=29 %). Wen et al [33] conducted the CBR tests on 7-day-cured fly ashstabilized RAP and found that the CBR of RAP increased linearly with an increase in fly ash content as shown in Fig. 5a.…”

“…8a-c. Wen et al [33] conducted UCS tests on 7-and 14-day-cured fly ash-stabilized RAP specimens and Taha et al [23] conducted UCS tests on 3-, 7-, and 28-day-cured cement-stabilized RAP specimens. They found that the UCS increased with an increase in the stabilizing agent (cement or fly ash) content and the curing period as shown in Fig.…”