Impact of temperature and moisture on the tensile strain of asphalt concrete layers

Figures & data

Figure 1. Cross-sections of pavement structures SE 14, SE 18 and SE 20 and the vertical location of the instrumentation.

Figure 2. Gradation curves for asphalt mix types ABT 16, AG 22 and AG 32 (Arvidsson 2014).

Table 1. Material, binder type, binder content and air void content for all bound layers (Arvidsson 2014).

Structure	Asphalt concrete	Binder type	Binder content [weight–%]	Air void [%]
SE 14	ABT 16	70/100	6.4	2.5
	AG 32	160/220	4.1	4.5
SE 18	ABT 16	70/100	5.8	2.5
	AG 22	160/220	4.2	4.5
SE 20	ABT 16	70/100	6.3	2.5

Table 2. Types of unbound materials and results of plate loading test subgrade (Ev2 and Ev2/Ev1) (Arvidsson 2014).

Structure	Layer	Material	Ev2 [MPa]	Ev2/Ev1
SE 14	Base course	Crushed stone [0/32]	156 ± 12.14	1.9 ± 0.14
	Sub-base	Crushed stone [0/90]	–	–
	Subgrade	Silty sand	63 ± 3.23	2.7 ± 0.23
SE 18	Base course	Crushed stone [0/32]	105 ± 8.14	2.5 ± 0.34
	Sub-base	Crushed gravel [0/90]	–	–
	Subgrade	Silty sand	43 ± 3.94	3.0 ± 0.24
SE 20	Base course	Crushed stone [0/32]	74 ± 3.04	2.5 ± 0.44
	Sub-base	Crushed gravel [0/90]
	Subgrade	Silty sand	48 ± 0.34	3.1 ± 0.14

Table 3. Temperature and groundwater levels used in the study.

Environmental Conditions	SE 14					SE 18			SE 20
Temperature [°C]	5.5	9.0	18.5	10.8	11.3	4.9	10.3	17.4	0.9	6.6
GWT (below subgrade surface) [mm]	>3000	>3000	>3000	400	30	>3000	>3000	>3000	>3000	>3000
Volumetric water content (22.5 cm below subgrade surface) [%]	8.2	8.3	8.3	20.9	30.1	16.6	16.1	16.0	8.0	8.0

Figure 3. Volumetric water content measurements for SE 14 showing test dates (arrows).

Figure 4. (a) FWD measurements, (b) measured horizontal strain at the bottom of the asphalt bound layers for structure SE 18.

Figure 5. (a) FWD measurements, (b) measured horizontal strain at the bottom of the asphalt bound layers for structure SE 20.

Figure 6. (a) FWD measurements, (b) measured horizontal strain at the bottom of the asphalt bound layers for structure SE 14.

Figure 7. (a) FWD measurements at 10°C with varying groundwater levels, (b) measured horizontal strain at the bottom of the asphalt bound layers for structure SE 14.

Figure 8. (a) Measured and predicted values of horizontal strain at the bottom of the asphalt layer using Equation (1) and (b) Equation (2) with respect to the 45° equality line.

Table 4. ANOVA analysis with moisture content as an independent variable.

Statistic	Coefficient	Standard Error	P-value
Constant	199.25	57.01	3.E-03
Temperature	5.31	1.10	2.E-04
Moisture content	−5.50	1.50	2.E-03
D0	0.69	0.28	3.E-02
D300	−1.62	0.75	5.E-02
D900	3.39	0.73	3.E-04
R^2	0.76	n/a	n/a
Adjusted R^2	0.68	n/a	n/a
Standard Deviation	20.97	n/a	n/a

*n/a = not applicable.

Table 5. ANOVA analysis without moisture content as an independent variable.

Statistic	Coefficient	Standard Error	P-value
Constant	298.08	66.24	3.E-04
Temperature	3.05	1.19	2.E-02
D0	1.03	0.35	9.E-03
D300	−2.43	0.94	2.E-02
D900	2.89	0.95	7.E-03
R^2	0.55	n/a	n/a
Adjusted R^2	0.44	n/a	n/a
Standard Deviation	27.62	n/a	n/a

*n/a = not applicable.

Figure 9. Measured and predicted values of horizontal strain at the bottom of the asphalt layer using (a) Equation (3) and (b) Equation (4) with respect to the 45° equality line.

Arvidsson, H., 2014. HVS-test för skattning av nedbrytningseffekter från den tunga trafikens belastning: SE14, SE18 och SE20. Linköping, Sweden: Statens väg-och transportforskningsinstitut.

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