Method for calculating the optimum dosage of the two-component synchronous rejuvenator for aged SBS-modified asphalt

A method for calculating an optimum dosage of a two-component synchronous rejuvenator for aged styrene-butadiene-styrene (SBS)-modified asphalt comprising:

• (1) selecting unaged SBS-modified asphalt, detecting vibration intensity of an infrared spectral characteristic functional group polybutadiene at 968 cm−1 of the SBS-modified asphalt, calculating a peak area ratio A968/ΣA650-2000, and recording a characteristic peak area ratio of unaged SBS molecular chain as IB0;
• meanwhile, detecting a vibration intensity of the unaged SBS-modified asphalt at 1376 cm−1 and 1600 cm−1, calculating a peak area ratio of an aliphatic and aromatic group, respectively, and recording a characteristic peak area ratio of the unaged SBS-modified asphalt as IB, aI0=A1376/ΣA650-2000, or ARI0=A1600/ΣA650-2000;
• (2) selecting several groups of SBS-modified asphalt with different aging degrees, following a test method in step (1), detecting a vibration intensity of the infrared spectral characteristic functional group polybutadiene of the SBS-modified asphalt with different aging degrees at 968 cm−1, and recording a characteristic peak area ratio of aged SBS molecular chain as IBA;
• meanwhile, detecting a vibration intensity of the SBS-modified asphalt with different aging degrees at 1376 cm−1 and 1600 cm−1, calculating a peak area ratio of an aliphatic and aromatic group of the aged SBS-modified asphalt, respectively, and recording a characteristic peak area ratio of aged pure asphalt as IB, aIA=A1376/ΣA650-2000, and ARIA=A1600/ΣA650-2000;
• (3) based on the characteristic peak area ratio of the unaged SBS molecular chain IB0 as well as a characteristic peak area ratio of IB, aI0, and ARI0 of the unaged SBS-modified asphalt in step (1), determining a peak area ratio of polybutadiene in the SBS-modified asphalt with different aging degrees at 968 cm−1 and the peak area ratio of aliphatic and aromatic group at 1376 cm−1 and 1600 cm−1 in step (2);
• wherein an SBS molecular chain rejuvenator, instead of restoring a lost peak area ratio at 968 cm−1 by aging, generates a new characteristic absorption peak area ratio through reaction with an oxygen-containing functional group at an end of a broken SBS molecular chain so to compensate for the lost peak area ratio, while a pure asphalt component regulator restores the lost peak area ratio at 1376 cm−1 and 1600 cm−1 due to aging by introducing light components;
• (4) based on a mass percentage of the aged SBS-modified asphalt, adding 1% to 10% SBS molecular chain rejuvenator and 1% to 15% pure asphalt component regulator to the SBS-modified asphalt with different aging degrees to obtain multiple groups of rejuvenated SBS-modified asphalt;
• in step (4), the steps for adding the SBS molecular chain rejuvenator and the pure asphalt component regulator into the aged SBS-modified asphalt are as follows:
• (S1) heating the aged SBS-modified asphalt to 140 to 160° C., controlling a speed of high-speed shears to 800 to 1000 rpm, and uniformly adding a corresponding proportion of the pure asphalt component regulator into the aged SBS-modified asphalt;
• once the pure asphalt component regulator is completely added, adjusting the speed to 1600 to 1800 rpm and continuing to shear and mix for 5 to 10 minutes;
• (S2) adjusting the speed to 500 rpm and uniformly adding a corresponding proportion of the SBS molecular chain rejuvenator;
• once the SBS molecular chain rejuvenator is completely added, adjusting the speed to 800 to 1000 rpm and continuing to shear and mixing for 10 to 15 minutes, and then placing a mixture in an oven at 50 to 70° C. for 60 minutes to obtain the rejuvenated SBS modified asphalt;
• (5) selecting different combinations of pure asphalt component regulator and SBS molecular chain rejuvenator to rejuvenate SBS-modified asphalt, following the test method in step (1), as a chemical reaction type of the SBS molecular chain rejuvenator and oxygen-containing functional groups at an end of a broken SBS molecular chain, detecting a vibration intensity of infrared spectral reaction rejuvenation characteristic functional groups of the SBS-modified asphalt with different degrees of rejuvenation, calculating a peak area ratio, and recording a peak characteristic area ratio of rejuvenated SBS molecular chain as IBR;
• meanwhile detecting the vibration intensity of the SBS-modified asphalt with different degrees of rejuvenation at 1376 cm−1 and 1600 cm−1, calculating a peak area ratio of aliphatic and aromatic group of the rejuvenated SBS modified asphalt respectively, and recording a characteristic peak area ratio of rejuvenated pure asphalt as IB, aIR and ARIR;
• then determining an optimum dosage of the SBS molecular chain rejuvenator and the pure asphalt component regulator, namely, the optimum dosage of the SBS molecular chain rejuvenator is a dosage at which a new characteristic absorption peak area ratio generated by reaction precisely compensates for the lost characteristic peak area ratio at 968 cm−1 by aging, and the optimum dosage of the pure asphalt component regulator is a dosage at which the lost characteristic peak area ratio at 1376 cm−1 and 1600 cm−1 by aging is fully restored;
• (6) as the optimum dosage of the SBS molecular chain rejuvenator and the pure asphalt component regulator and the characteristic peak area ratio needs to be restored, drawing a scatter plot to obtain a regression equation between the optimum dosage of the SBS molecular chain rejuvenator and the restored characteristic peak area ratio y1=k1x+b1, and a regression equation between the optimum dosage of the pure asphalt component regulator and the restored characteristic peak area ratio y2=k2x+b2;
• (7) according to the actual tested IBA, IB, aIA, and ARIA of the SBS-modified asphalt with a specific aging degree, taking IB0, IB, aI0 and ARI0 of the unaged SBS-modified asphalt as reference to calculate corresponding characteristic peak area ratios that need to be restored, and substituting into the regression equations in step (6) to calculate the optimum dosage of the SBS molecular chain rejuvenator and the pure asphalt component regulator;
• in steps (1) to (7), A968, A1376, and A1600 refer to the peak area corresponding to the infrared spectral wave number of 968 cm−1, 1376 cm−1, and 1600 cm−1, respectively;
• ΣA650-2000 is the sum of the peak area of the infrared spectral wave numbers from 650 cm−1 to 2000 cm−1.