Investigating mechanical characteristics of aggregate structure for road materials

Figures & data

Figure 1. Sketch of loading device.

Figure 2. Principle diagram of the proposed test. (a) Mechanical model of pavement structure (red arrow: traffic load; black arrow: lateral confinement). (b) Principle diagram of the traditional triaxial test (c) Principle diagram of the proposed test.

Figure 3. Relationship between indenter-force and indenter-displacement.

Table 1. Lab test results of aggregate packing composed of D1.

No.	Confining pressure (KPa)	Mass fraction (%) of aggregates	Indenter peak-force (N)	CV (%)
1	50	100	119.2	6.9
2	100	100	124.7	6.7
3	150	100	136.7	8.6
4	250	100	144.0	6.2
5	350	100	159.3	3.9

Table 2. Lab test results of aggregate packing composed of D1 and D2.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates		Indenter peak-force (N)	CV (%)
		D1 (P1)	D2
6	50	90	10	228.1	7.2
7		85	15	238.1	9.7
8		80	20	254.6	9.8
9		75	25	224.8	8.3
10		70	30	181.9	6.5
11		65	35	171.9	6.9
12		60	40	155.4	3.0
13	100	90	10	222.1	6.9
14		85	15	237.7	6.8
15		80	20	248.5	5.3
16		75	25	266.3	4.8
17		70	30	234.7	4.9
18		65	35	189.5	7.6
19		60	40	178.8	9.1
20	150	90	10	216.6	7.8
21		85	15	237.7	7.6
22		80	20	251.0	6.8
23		75	25	277.2	3.9
24		70	30	265.5	6.0
25		65	35	233.0	6.3
26		60	40	205.3	5.5
27	250	85	15	259.6	8.4
28		80	20	283.1	4.0
29		75	25	304.0	9.7
30		70	30	312.3	7.9
31		65	35	269.7	8.1
32		60	40	214.1	4.7
33	350	80	20	303.8	8.5
34		75	25	328.6	7.9
35		70	30	341.7	9.0
36		65	35	308.7	8.8
37		60	40	235.3	6.2

Table 3. Lab test results of aggregate packing composed of D1–D3.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates			Indenter peak-force (N)	CV (%)
		P2		D3
		D1	D2
38	50	76	19	5	314.6	6.2
39		72	18	10	325.6	8.4
40		68	17	15	334.3	8.3
41		64	16	20	319.9	8.8
42		60	15	25	304.9	9.1
43		56	14	30	287.1	7.7
44	100	71.2	23.8	5	328.3	9.2
45		67.5	22.5	10	339.8	6.1
46		63.7	21.3	15	349.6	7.6
47		60	20	20	333.9	7.8
48		56.2	18.8	25	318.1	7.5
49		52.5	17.5	30	301.2	2.6
50	150	71.3	23.7	5	337.2	8.1
51		67.5	22.5	10	353.3	7.7
52		63.8	21.2	15	374.0	7.2
53		60	20	20	365.5	8.3
54		56.3	18.7	25	358.7	4.4
55		52.5	17.5	30	335.9	8.7
56	250	63	27	10	377.7	5.1
57		59.5	25.5	15	394.6	6.3
58		56	24	20	405.6	9.8
59		52.5	22.5	25	397.1	6.8
60		49	21	30	374.6	7.1
61	350	63	27	10	435.5	8.5
62		59.5	25.5	15	446.6	6.1
63		56	24	20	450.3	8.3
64		52.5	22.5	25	437.1	9.5
65		49	21	30	409.7	9.3

Table 4. Lab test results of aggregate packing composed of D1–D4.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates				Indenter peak-force (N)	CV (%)
		P3			D4
		D1	D2	D3
66	50	64.6	16.2	14.2	5	386.2	4.6
67		61.2	15.3	13.5	10	398.5	6.6
68		57.8	14.5	12.7	15	408.7	5.5
69		54.4	13.6	12	20	393.2	7.6
70		51	12.7	11.3	25	375.2	8.8
71	100	60.5	20.2	14.3	5	404.2	5.8
72		57.4	19.1	13.5	10	417.9	6.1
73		54.2	18	12.8	15	427.7	6.9
74		51	17	12	20	410.6	7.1
75		47.8	15.9	11.3	25	391.3	8.3
76	150	60.6	20.1	14.3	5	428.6	9.9
77		57.4	19.1	13.5	10	439.2	7.1
78		54.2	18	12.8	15	446.4	7.2
79		51	17	12	20	437.1	6.8
80		47.9	15.9	11.2	25	429.2	6.6
81	250	53.2	22.8	19	5	490.1	6.1
82		50.4	21.6	18	10	496.2	6.9
83		47.6	20.4	17	15	499.6	8.9
84		44.8	19.2	16	20	488.8	5.3
85		42	18	15	25	468.6	6.4
86	350	53.2	22.8	19	5	548.6	9.1
87		50.4	21.6	18	10	558.5	7.3
88		47.6	20.4	17	15	561.3	6.2
89		44.8	19.2	16	20	549.3	3.8
90		42	18	15	25	530.1	6.1

Table 5. Lab test results of aggregate packing composed of D1–D5.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates					Indenter peak-force (N)	CV (%)
		P4				D5
		D1	D2	D3	D4
91	50	54.9	13.8	12	14.3	5	428.4	8.0
92		52	13.1	11.4	13.5	10	443.1	5.5
93		49.1	12.3	10.8	12.8	15	450.1	6.6
94		46.2	11.6	10.2	12	20	435.5	5.8
95		43.3	10.9	9.5	11.3	25	415.3	6.2
96	100	51.5	17.1	12.1	14.3	5	447.1	9.2
97		48.8	16.2	11.5	13.5	10	462.6	9.1
98		46	15.3	10.9	12.8	15	470.7	4.6
99		43.4	14.4	10.2	12	20	454.6	8.1
100		40.6	13.5	9.6	11.3	25	433.1	6.2
101	150	51.5	17.1	12.2	14.2	5	481.9	8.3
102		48.8	16.2	11.5	13.5	10	491.1	10.0
93		45.6	15.4	11.1	12.9	15	500.8	9.1
94		43.4	14.4	10.2	12	20	486.9	5.5
95		40.7	13.5	9.6	11.2	25	471.1	8.9
96	250	45.2	19.4	16.2	14.2	5	540.5	6.1
97		42.8	18.4	15.3	13.5	10	551.5	9.0
98		40.5	17.3	14.5	12.7	15	555.1	5.8
99		38.1	16.3	13.6	12	20	547.0	6.7
100		35.7	15.3	12.8	11.2	25	531.5	9.5
101	350	45.2	19.4	16.2	14.2	5	608.6	9.1
102		42.8	18.4	15.3	13.5	10	619.9	3.7
103		40.5	17.3	14.5	12.7	15	621.3	5.0
104		38.1	16.3	13.6	12	20	606.6	7.6
105		35.7	15.3	12.8	11.2	25	594.0	6.2

Table 6. Lab test results of aggregate packing composed of D–D6.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates						Indenter peak-force (N)	CV (%)
		P5					D6
		D1	D2	D3	D4	D5
106	50	46.6	11.7	10.2	12.2	14.3	5	444.3	8.4
107		44.2	11.1	9.7	11.5	13.5	10	458.7	4.3
108		41.7	10.5	9.2	10.8	12.8	15	465.5	9.6
109		39.3	9.9	8.6	10.2	12	20	451.6	6.9
110		36.8	9.2	8.1	9.6	11.3	25	431.7	6.3
111	100	43.7	14.5	10.3	12.2	14.3	5	464.0	7.3
112		41.4	13.8	9.8	11.5	13.5	10	479.0	4.5
113		39.1	13	9.3	10.8	12.8	15	486.8	9.5
114		36.8	12.3	8.7	10.2	12	20	471.1	8.8
115		34.5	11.5	8.1	9.6	11.3	25	450.9	8.7
116	150	43.8	14.5	10.4	12.1	14.2	5	498.5	8.4
117		41.5	13.8	9.8	11.4	13.5	10	509.3	9.6
118		39.2	13	9.3	10.8	12.7	15	515.1	7.0
119		36.9	12.2	8.7	10.2	12	20	498.5	8.9
120		34.6	11.5	8.2	9.5	11.2	25	479.7	4.3
121	250	38.4	16.5	13.7	12.1	14.3	5	562.6	7.2
122		36.4	15.6	13	11.5	13.5	10	566.8	8.6
123		34.4	14.7	12.3	10.8	12.8	15	571.9	8.6
124		32.4	13.9	11.6	10.2	12	20	561.2	5.9
125		30.3	13	10.8	9.6	11.3	25	539.3	9.1
126	350	38.4	16.5	13.7	12.1	14.3	5	644.3	7.3
127		36.4	15.6	13	11.5	13.5	10	647.8	6.3
128		34.4	14.7	12.3	10.8	12.8	15	655.1	6.2
129		32.4	13.9	11.6	10.2	12	20	647.0	7.2
130		30.3	13	10.8	9.6	11.3	25	634.4	8.6

Table 7. Lab test results of aggregate packing composed of D1–D7.

No.	Confining pressure (kPa)	Mass fraction (%) of aggregates							Indenter peak-force (N)	CV (%)
		P6						D7
		D1	D2	D3	D4	D5	D6
131	50	39.6	10	8.7	10.3	12.2	14.3	5	445.8	8.3
132		37.5	9.5	8.3	9.7	11.5	13.5	10	460.1	7.6
133		35.4	8.9	7.8	9.2	10.9	12.8	15	467.0	7.7
134		33.4	8.4	7.4	8.6	10.2	12	20	453.0	8.0
135		31.2	7.9	6.9	8.1	9.6	11.3	25	433.3	6.0
136	100	37.1	12.3	8.8	10.3	12.2	14.3	5	465.7	9.1
137		35.2	11.7	8.4	9.7	11.5	13.5	10	480.4	7.7
138		33.2	11	7.9	9.2	10.9	12.8	15	488.4	6.2
139		31.3	10.4	7.5	8.6	10.2	12	20	473.1	6.7
140		29.3	9.7	7	8.1	9.6	11.3	25	453.7	6.6
141	150	37.2	12.4	8.8	10.3	12.1	14.2	5	496.8	7.6
142		35.3	11.7	8.4	9.7	11.4	13.5	10	507.6	5.1
143		33.3	11.1	7.9	9.2	10.8	12.7	15	518.8	3.3
144		31.4	10.4	7.4	8.6	10.16	12	20	506.6	9.8
145		29.4	9.8	7.0	8.1	9.5	11.2	25	491.9	8.7
146	250	32.7	14	11.7	10.3	12.1	14.2	5	568.2	5.5
147		31	13.2	11.1	9.7	11.5	13.5	10	576.7	9.6
148		29.2	12.5	10.5	9.2	10.9	12.7	15	579.3	8.8
149		27.5	11.8	9.8	8.6	10.3	12	20	568.7	6.2
150		25.8	11	9.2	8.1	9.6	11.3	25	559.1	9.0
151	350	32.7	14	11.7	10.3	12.1	14.2	5	651.0	7.1
152		31	13.2	11.1	9.7	11.5	13.5	10	656.9	5.3
153		29.2	12.5	10.5	9.2	10.9	12.7	15	658.4	9.5
154		27.5	11.8	9.8	8.6	10.3	12	20	651.1	4.4
155		25.8	11	9.2	8.1	9.6	11.3	25	641.9	6.6

Figure 4. f of P1–P7.

Figure 5. Procedure for a randomly generated numerical model.

Figure 6. Numerical specimen.

Figure 7. Numerical specimen.

Figure 8. Average values of the errors (P1–P7) in the case of using different friction coefficients.

Table 8. Input parameters for DEM simulations.

Contact normal stiffness	Contact Shear stiffness	Friction coefficient
460 MPa	177 MPa	0.7

Table 9. Errors between laboratory data and simulation results.

Confining pressure/KPa	Aggregate packing	Error (%) of the peak indenter force	Confining pressure/KPa	Aggregate packing	Error (%) of the peak indenter force
50	P1	4.87	100	P1	5.22
	P2	6.11		P2	5.07
	P3	6.68		P3	6.07
	P4	4.43		P4	4.44
	P5	5.11		P5	7.58
	P6	5.57		P6	4.55
	P7	5.93		P7	6.77
150	P1	5.61	250	P1	3.89
	P2	4.53		P2	6.62
	P3	6.34		P3	5.96
	P4	7.43		P4	4.87
	P5	5.57		P5	5.83
	P6	5.55		P6	6.78
	P7	5.33		P7	5.22
350	P1	4.82
	P2	6.15
	P3	5.22
	P4	7.77
	P5	5.27
	P6	6.59
	P7	4.37

Table 10. Distribution of aggregate contact force in different aggregate packing.

Packing	Confining pressure (KPa)	Index	Grade 1: (double {F}, +∞)	Grade 2: [{F}, double {F}]	Grade 3: (0,<{F})
P1	50	P(f) /%	34.1	30.6	35.3
		Ni	29	26	30
	100	P(f) /%	39.1	36.8	24.1
		Ni	34	32	21
	150	P(f) /%	44.8	41.4	13.8
		Ni	39	36	12
	250	P(f) /%	48.4	43.0	8.6
		Ni	45	40	8
	350	P(f) /%	50	43.8	6.2
		Ni	48	42	6
P2	50	P(f) /%	41.3	24.9	33.8
		Ni	83	50	68
	100	P(f) /%	42.4	30.5	27.1
		Ni	86	62	55
	150	P(f) /%	45.0	35.0	20.0
		Ni	90	70	40
	250	P(f) /%	47.6	38.3	14.1
		Ni	98	79	29
	350	P(f) /%	49.5	40.4	10.1
		Ni	103	84	21
P3	50	P(f) /%	32.6	26.2	41.2
		Ni	126	101	159
	100	P(f) /%	35.2	31.6	33.2
		Ni	136	122	128
	150	P(f) /%	36.8	36.9	26.3
		Ni	143	143	102
	250	P(f) /%	38.6	40.7	20.7
		Ni	151	159	81
	350	P(f) /%	39.7	43.5	16.8
		Ni	157	172	66
P4	50	P(f) /%	27.7	32.1	40.2
		Ni	164	190	238
	100	P(f) /%	29.1	36.7	34.2
		Ni	172	217	202
	150	P(f) /%	30.5	40.6	28.9
		Ni	180	240	171
	250	P(f) /%	31.8	44.8	23.4
		Ni	189	266	139
	350	P(f) /%	33.4	48.1	18.5
		Ni	201	289	111
P5	50	P(f) /%	18.0	32.7	49.3
		Ni	172	312	470
	100	P(f) /%	18.9	39.4	41.7
		Ni	180	376	398
	150	P(f) /%	19.5	45.9	34.6
		Ni	186	439	331
	250	P(f) /%	20.4	53.5	26.1
		Ni	196	513	250
	350	P(f) /%	21.4	59.3	19.3
		Ni	206	571	186
P6	50	P(f) /%	13.1	25.4	61.5
		Ni	172	335	811
	100	P(f) /%	13.9	30.1	56.0
		Ni	183	397	738
	150	P(f) /%	14.3	35.4	50.3
		Ni	188	466	661
	250	P(f) /%	15.2	41.1	43.7
		Ni	201	545	579
	350	P(f) /%	15.9	45.0	39.1
		Ni	211	598	519
P7	50	P(f) /%	9.9	19.1	71.0
		Ni	176	338	1260
	100	P(f) /%	10.5	22.7	66.8
		Ni	186	402	1182
	150	P(f) /%	10.8	26.6	62.6
		Ni	191	471	1109
	250	P(f) /%	11.4	31.0	57.6
		Ni	203	550	1021
	350	P(f) /%	12.2	34.0	53.8
		Ni	217	608	961

Table 11. Specification gradation.

Materials	Pass percent/% through the following sieve pore
	31.5 mm	19 mm	13.2 mm	9.5 mm	4.75 mm	2.36m m	1.18 mm	0.6 mm	0.3 mm	0.15 mm	0.075 mm
Asphalt concrete	100	53–72	39–60	31–51	20–40	15–32	10–25	8–18	5–14	3–10	2–6
Cement stabilised macadam	100	68–86	38–58		22–32	16–28	8–15		0–7

Figure 10. The optimal mass proportion of different aggregates in P5.

Figure 11. Comparison between specification gradation and proposed gradation. (a) Asphalt concrete. (b) Cement stabilised macadam.

Table 12. Gradation calculation.

Materials	Confining pressure	LP/%	D1:D2:D3:D4:D5	Pass percent/% through the following sieve pore
				31.5 mm	19 mm	13.2 mm	9.5 mm	4.75 mm	2.36 mm
Asphalt concrete	50 KPa	68–85	49.1:12.3:10.8:12.8:15	100	58–66	47–58	38–50	27–41	15–32
	100 KPa		46.0:15.3:10.9:12.8:15	100	60–67	47–58	38–50	27–41	15–32
	150 KPa		45.6:15.4:11.1:12.9:15	100	61–68	48–59	39–51	27–41	15–32
	250 KPa		40.5:17.3:14.5:12.7:15	100	65–72	50–60	39–51	27–41	15–32
	350 KPa		40.5:17.3:14.5:12.7:15	100	65–72	50–60	39–51	27–41	15–32
Cement stabilised macadam	50 KPa	72–84	49.1:12.3:10.8:12.8:15	100	58–64	39–47		26–37	16–28
	100 KPa		46.0:15.3:10.9:12.8:15	100	61–66	39–47		26–37	16–28
	150 KPa		45.6:15.4:11.1:12.9:15	100	62–67	39–48		26–37	16–28

Table 13. Proposed gradation.

Materials	Pass percent/% through the following sieve pore
	31.5 mm	19 mm	13.2 mm	9.5 mm	4.75 mm	2.36 mm	1.18 mm	0.6 mm	0.3 mm	0.15 mm	0.075 mm
Asphalt concrete	100	58–72	47–60	38–51	27–41	15–32	10–25	8–18	5–14	3–10	2–6
Cement stabilised macadam	100	58–66	39–48		26–37	16–28	8–15		0–7

Table 14. Pavement performance of road materials.

Materials	Performance index		Proposed gradation	Specification gradation
Asphalt concrete	Dynamic stability/times·mm^−1	AVG	3589	3151
		CV	6.02%	9.39%
		NR	6	6
	Bending stiffness modulus/MPa	AVG	10,167	10,821
		CV	6.98%	8.93%
		NR	9	9
Cement stabilised macadam	Seven-day compressive strength/MPa	AVG	5.3	4.5
		CV	7.88%	8.67%
		NR	9	9
	Seven-day splitting strength/MPa	AVG	0.78	0.70
		CV	8.03%	9.43%
		NR	9	9

Figure 12. Base course cores. (a) Specification gradation. (b) Revised gradation.