Evaluation of Impact Energy Absorption Characteristics of Flexible Sand Asphalt Pavement for Pedestrian Way

보도용 연성 샌드 아스팔트 포장의 충격흡수 특성 평가

Abstract

More than 90% of roadway in the world are paved as asphalt concrete pavement due to its excellent properties compared with other paving materials; excellent riding quality, flexibility, anti-icing property and easy maintenance-ability. In this study, to make best use of the softer property of the asphalt mixture, the flexible sand asphalt mixture (FSAM) was developed for pedestrian ways. The mix design was conducted to prepare FSAM using PG64-22 asphalt, screenings (sand) less than 5mm, crumb rubber, hydrated lime and limestone powder without coarse aggregate. The deformation strength ($S_D$), indirect tensile strength (ITS) and tensile strength ratio (TSR) tests were conducted to make sure durability of FSAM performance. The impact energy absorption and flexibility were measured by drop-boll test and the resilient modulus ($M_R$) test. The impact energy absorption of FSAM was compared with normal asphalt pavement, concrete pavement, stone and concrete block for pedestrian way. As a result of drop-boll test, FSAM showed higher impact energy absorption compared with other paving materials with the range of 18% to 43%. Impact energy absorption of FSAM increased with increasing test temperature from 5 to $40^{\circ}C$. The results of $M_R$ test at $5^{\circ}C$ showed that the flexibility of FSPA was increased further, because the $M_R$ value of the sand asphalt was measured to be 38% lower than normal dense-graded asphalt mixture (WC-1). Therefore, it was concluded that the FSAM could provide a high impact absorbing characteristics, which would improve walking quality of the pedestrian ways.

Fig. 1 Materials for FSAP; (a) sand (screenings), (b) CRM, (c) limestone powder, and (d) hydrated lime

Fig. 2 Gradation of FSAP mixture

Fig. 3 SGC

Fig. 4 Curing at 60℃ for Kim test

Fig. 5 Kim-test set up

Fig. 6 ITS test set-up

Fig. 7 Illustration of (a) drop-ball test concept and (b) test on FSAP slab

Fig. 8 Drop-ball test for paving material (a) asphalt pavement, (b) concrete pavement, (c) footway block and (d) curve stone between asphalt pavement and pedestrian way

Fig. 9 Resilient modulus test system; ⓐ test fixture within temperature chamber, ⓑ load controller and data logger, and ⓒ strain gage-installed specimens to be tested

Fig. 10 Impact energy absorption of sand asphalt mixtures by CR contents at various test temperature

Fig. 11 Impact energy absorption for various field paving materials (test temperature at 15℃)

Fig. 12 Comparison of resilient modulus on sand asphalt mixtures by temperature

Fig. 13 Relationship between impact energy absorption and resilient modulus at three test temperatures

Table 1 Mix design criteria for sand asphalt mixtures

Table 2 Mix design results of sand asphalt mixtures