ministerie van verl<eer en waterstaat
rijkswaterstaat
ii^l
W J ^ P
^ Rijkswaterstaat
Dienst Weg- en Waterbouwkunde Delft
archief Asfalt in de Waterbouw
SOME PROPERTIES OF ASPHALTIC CONCRETE FOR USE IN HYDRAULIC
EN-GINEERING.
IR. W. BANDSMA and ING. C.C. MONTAUBAN, Road Engineering
Divi-sion of the Rijkswaterstaat (Wegbouwkundige Dienst)-Delft
THE NETHERLANDS
1. Introduction
Since the 1960s sea defences in the Netherlands are being improved for better protection of the land against
inun-dation. For a major percentage of the revetments applied for this purpose, asphaltic concrete is used. The main requirement to be met by asphaltic concrete revetments is
impermeability, which is achieved through a low voids content. Simultaneously this produces a beneficial effect
on durability. (Ref. 1).
The layer thicl<ness is determined on the basis of the
"uplift criterion"; i.e. enough weight, to prevent lift-ing of the revetment due to water pressures from the em-bankment. (Ref. 2 ) . Actually properties such as strength
and stiffness have never been taken into account exten-sively in the design of the revetments, as the results of rough computations showed, that application of the
"up-lift criterion" leads to some overdesigning in terms of strength. For several reasons however there is need for more and better information on the strength and
defor-mation behaviour of asphaltic concrete for dike revet-ments.
C.C. Moncauban U. Bandsma
A. Safety
It is very important to be able to determine by
calcu-lation, the safety of water defence constructions. The
assumption of a certain degree of overdesigning is not
acceptable. The safety can be determined only through
ap-plication of a design model, where the asphaltic
con-crete's parameters must be known.
B. Durability
Water defences are constructed and designed for long
ser-vice life, with minimum maintenance requirements. To
•
achieve that, the service life of the various component
parts must be determined.
The same applies to asphalt revetments, as the properties
of the material will change with time. The degree to
which these properties (particulary the material's
strength and stiffness) change in the course of time will
be one of the factors determining the safety of the dike,
and thus be highly decisive for the maintenance strategy
to be observed.
C. Non traditional materials
In the past few years application has strongly widened of
waste materials and industrial by-products (construction
waste; crushed asphalt). If these materials are to be
used in asphalt mixes, information must be collected on
the effect of such materials on the properties and
beha-viour of these new mixes.
So, the criteria for safety and durability, expressed in
terms of strength and deformation behaviour, play a very
significant role in comparative research.
Some properties of asphaltic concrete for use in hydraulic engineering works.
Some p r o o e r c i e s of a s p h a l t i c C.C. Montauban
* concrete for use in h y d r a u l i c W. Bandsma
engineering works.
iZ. Properties of asphaltic concrete revetments
The most pertinent properties of asphaltic concrete re-vetments must be, considering their function as
construc-tion elements:
a. Impermeability
The water proofing function is guaranteed by reducing the voids content of the applied asphalt to a minimum.
b. Strength
The revetment must have a specific strength, to prevent the loads (waves etc.) from causing the construction to
collapse.
c. Resistance te deformation
Lasting deformation, due to loads, must be avoided;
con-sequently the stiffness must meet specific requirements. d. Flexibility
In case of differential settlements occurring under the revetment, some deformation must be possible, without the
maximum allowable strain values being exceeded.
e. Layer thickness
A specific layer thickness is required, in view of the
desired strength and deformation properties and the "up-lift criterion".
The level of the properties listed above initially
deter-mines the safety of the construction.
However, these properties will change with time.
In the case of asphalt these changes are related to four
-Eone properties of asphaltic C.C. Montauban
concrete for use ir. hydraulic W. Bandssa
engineering works.
I. Ageing
The action of U.V.-light and oxygen causes the binder to "harden". This effect produces higher stiffnesses, higher
strengths, and lower allowable strains. A low voids
con-tent prevents early ageing.
II. Stripping
Bitumen, due to the greater affinity for water of mineral aggregates, is driven out by water on the long term. Such "stripping" causes the cohesion of the asphalt mix (or
strength) and the stiffness and allowable strain te be reduced. The axiom stating that low air void percentages prevent early ageing also applies to this particular
du-rability aspect: the stripping rate will be strongly slowed down.
III. Fatigue
Asphalt is sensitive to fatigue. Due to significant load fluctuation the strength, stiffness, and allowable strain of the material are reduced. For the moment asphaltic
concrete revetments are assumed to be subject to fatigue for a long period of time, due to frequent attack by
wa-ves. Information must be collected to determine which mixes are the least sensitive to that phenomenon.
IV. Erosion
With time, asphalt revetments may show signs of wear, due to the effect of wave and current forces, particulary if
solid substances (stone, sand, dirt) are entrained by the water.
C.C. Montauban
W. Bandsma
These four phenomena affect the properties of the
asphal-tic concrete revetment. This is illustrated in Fig. 1. It should be noted that the phenomena occur simul-taneously, and may also affect each other strongly (for
instance, stripping causes increased sensitivity to ero-sion). As a consequence research into the individual ef-fect of these phenomena on the revetment properties is
very complex. Durability-phenomena Ageing Stripping Fatigue Erosion
Influence on properties of revetment: Imper-meability 0 (-)? 0 Strength + Resistance to deformation + flexibility -layer thickness 0 0 o
0 = no influence; + = increase; - = decrease
Fig. 1. Influence of the durability phenomena on the proper-ties of an asphalt revetment.
3. Test methods and results
For the purpose of analysing the strength and deformation
properties a wide variety of test methods is available (Ref. 3 ) .
The Road Engineering Division has at its disposal a
num-ber of tools and devices for the analysis of asphalt pav-ing mixtures. The equipment includes: fatigue test
devi-ces, a compressive and tensile strength tester, and creep
and wheel tracking devices.
Some properties of asphaltic concrete for use in hydraulic engineering works.
Some p r o p e r t i e s of a s p h a l t i c C.C. Montauban
c o n c r e t e for u s e in h y d r a u l i c U. Bandsma
e n g i n e e r i n g w o r k s .
For the analysis of asphaltic concrete for hydraulic
en-gineering, it was obvious to use test methods commonly j applied in road engineering research (creep, splitting and fatigue tests) combined with some additional methods
(strain, compressive and tensile strength tests).
In the course of the pastperiod various asphaltic concre-te mixes were concre-tesconcre-ted, for the purpose of several
pro-jects.
The test methods applied in the process are shown in Fig. 2. Method Creep (uniax) Strain ( " ) Compression ( " ) Tension ( " ) Splitting (diametr.) Fatigue* (4-p-b.) Specimens (im) 100 X 100 (0 X h) 100 X 100 (a X h) 100 X 60 (0 X h) 100 X 60 (B X h) 100 X 60 (B X h) 50 X 50 X 450 (b X h X 1) temperature (°C) 10 en 30 1Qj20;30 10 en 30 10 en 30 10iZ0;30 (0);10s20 «(max) (N/m^) 3j5 en 10 x lu" Z-ZO X lo" 3-17 X 10* Time (sec.) 60-3600 6Ü-1ÜUUÜ 30 Hz. e (mm/min.) 5 en 5U 5 en 50 20 en 50 Mix. A B C D t L E E A B C D E A C D*« * 4 - p o i n t - b e n d i n g t e a t : oodnax) = constant
• * Mix 0 : only measured So at 0,10 and ZD°C w i t h co(max) : c o n s t a n t .
Fig. 2. Review of used test-methods.
Fig. 3 lists the various mixes that were analysed.
These mixes all meet the current requirements applying to asphaltic concrete for use in hydraulic engineering.
One of the mixes (A) is composed of (partially) recycled
C.C. Moncauban U. Bandsma
Some properties of asphaltic concrete for use in hydraulic
engineering works.
7
M i x . Stone (> 2 mm) Sand (2 mm - 63 Mm) F i l l e r (< 63 |Jm) Bitumen V o l . % v o i d s c o n t e n t V o l . % Bitumen V o l . % M i n . a g g r . B i t u m e n : - P e n e t r a t i o n - Temp. R 4 B - Pen. I n d e x A 53,0 3 9 , 2 7 , 8 100,0 6 , 1 5 , 0 1 2 , 7 8 2 , 3 100,0 77 4 8 , 7 - 0 , 5 B 49,3 4 2 , 3 8,4 100,0 6 , 4 6,0 13,3 8 0 , 7 100,0 40 54,7 - 0,5 C 51,6 4 1 , 7 6 , 7 100,0 6 , 5 3,6 1 4 , 3 8 2 , 1 1 0 0 , 0 63 4 9 , 5 - 0 , 8 D 5 0 , 0 4 2 , 8 7 , 2 100,0 6 , 6 5 , 7 13,8 8 0 , 5 1 0 0 , 0 67 4 9 , 0 - 0 , 8 E 50,2 42,3 7,5 100,0 6,9 4 , 7 14,5 80,8 100,0 65 53,5 + 0 , 3 S p e c i f i c a t i o n s 50 ± 5 42 ± 5 8 ± 1 6 , 5 ± 0 , 5 < 6Fig. 3. Review of tested mixtures.
io: 10 6 10. Smix (N/n,2) A B C D E 6.1 % Bitumen 6.4 n 6.S •• 6 . 6 X 6 . 9 •• lbs Sbit •H ». i'o« .10° .10' . _10 10'
C.C. Montauban U. Bandsma
Some p r o p e r t i e s of a s p h a l t i c c o n c r e t e for use in h y d r a u l i c
e n g i n e e r i n g w o r k s .
8
The mix stiffness (S mix) determined by means of creep
tests are plotted in Fig. 4 against the associated bitu-men stiffness. (S bit). S bit has been computed using the Shell PONOS program based on the van der Poel nomogram
(Ref. 5 ) . In the lower stiffness range (30°C) S mix shows a specific variation that can best be related to the va-riation of the bitumen content. In the upper stiffness
range (10°C) the lines appear to almost coincide. To have some idea of deformation under constant tensile stress,
some strain tests were carried out. The results of S mix as a function of S bit (Fig. 5) appear to show more vari-ation than with the creep test. "Weak" spots, like hair
cracks, may be playing a more significant role with ten-sile deformation than with compressive deformation. Further research into the strain behaviour under constant
load will possibly produce more useful information only if larger numbers of specimens are tested,
10 10 Smix (N/„,l) Sbit •H >• J O ' .10" .10 1 0 ' 10-^ 1 0 " ^ 10"^
C.C. Moncauban
Vr'. Bandsma
I For a first impression of the strength of asphaltic con-I Crete several uniaxial compressive and tensile strength i
I tests were carried out. The results (Fig. 6) clearly show j the major influence of temperature and deformation rate
on the strength. Mix. A B C D Temp. (°C) 10 20 30 10 20 30 10 20 30. 10 20 30 Splitting • e = 50 1,54 0,26 1,83 0,33 2,15 0,72 0,35 1,47 0,27 Tension e = 5 2,20 0,22 e = 50 3,80 0,54 Compression e = 5 4,50 0,93 e = 50 9,00 1,70 Fatigue (N = 1) f = 30 hz • 7,40 6,30 7,3 9,00 7,30 (a in 10^ N/m^)
• Extrapolated values for N = 1 from Nfracture - aa(max) - rela-tion
Fig. 6. Strength results.
S mix and the associated S bit values were computed from the strength values and the maximum deformations.
It appears from Fig. 7 that the mix stiffness based on compressive stress is greater than with tensile stress. This can be attributed to the role played by the coarse mineral aggregate in the case of compressive stress.
Sor.a procerties of asphaltic
concrete for use in hydraulic
C.C, Montauban U. Bandsma
Sone properties of a s p h a l t i c concrete for use in hydraulic
engineering works.
/o
110^ 10^4. 10' '^mix (N/m2) 10^ 10^ 10"^ Compression i.10=Sbit
(N/n,2) •H > .10*= -JO' 10^ 10'Fig. 7. Compressive strength and tension tests - S mix as- a function of S bit. io: 10' Smix (N/n,^) 1 0 ' . IO-" . . 1 0 ' C o m p r a s i i o n Tenalon ..10° (N/mM 41 > .10' ..10° 1 0 ' 1 0 - 10°
C.C. Montauban U. Bandsma
Some properties of asphaltic concrete for use in hydraulic
engineering works. //
N
Splitting tests have been carried out to obtain some im-pression of the strength data that can be collected
through application of this (simple) technique (Fig. 6 ) .
The splitting strength at 10°C and 30°C appears to be ap-proximately 50 percent of the tensile strength.
With these tests as a matter of fact the horizontal
de-formation has not been measured, so it was not possible to determine any stiffness modulus.
With the fatigue tests using a four-point bending device (frequency = 30 Hz) the stress amplitude was kept
con-fat.
+ 10^.1 10-^1 10** I A \ & \ • Temp 20°c M I X A ! c o 1 • 1 A . G^(lO^N/m2) Fia. 0,4 1,0 1,5 9. Fatigue tests - Nfatigue as a function of ao(max)C.C. Montauban
V, Bandsma
Some properties of asphaltic concrete for use in hydraulic engineering works.
/2
stent. In Fig. 9, for two asphaltic concrete mixes (con-ventional, and recycled), the number of load cycles
(N.fat.) at e = 2 X eo has been plotted against the
stress amplitude ao(max). At 10°C there appears to be a difference between the two asphaltic concrete mixes. How-ever, if the number of load cycles at fracture
(N.fract. = N.fat.) is plotted, (test-independently; Ref 4.) against the energy consumption, the two mixes appear tho show virtually the same trend at the twotest
tempera-tures. (fig. 10).
To get an impression of the dynamicbreaking strength, the relation Nfract.-oo(max) has been extrapolated at one
single load (N=1) (Fig. 6 ) .
10 . 10'. 10'
W,„
t O ^ o« 0 A Temp 10° c 20'c M I X A C O • A A Nfract _ 10 .10' 101^
F i g . 10. Fatigue t e s t s -10= 10" N f r a c t u r e as a f u n c t i o n of Wtot.C.C, Moncauban U. Bandsma
Some prooerties of asphaltic concrete for use in hydraulic
engineering works. /3
All stiffness values derived from the various tests have
been plotted into a master curve (Figs. 8 and 11).
Both for the upper and the lower stiffness ranges the va-lues are fairly within one band. The stiffness vava-lues
computed on the basis of tensile stress (tensile strength and strain tests) show a lower level than those computed
on the basis of compressive loads. This difference is mo-re marked with compmo-ressive and tensile stmo-rength tests than with creep and strain tests. The variation of S mix
related to S bit will depend, in principle, on the mine-ral composition, the bitumen content, and the voids con-tent. Further research into the individual effects is
de-sirable. Smix » ^^ Dyn. Bending Compraation «Tanilon Sbit 10" .10" I08 10' F i g . 1 1 . S mix as a f u n c t i o n of S b i t ( T o t a l - r e s u l t ) .
C.C, Montauban
W. Bandsma
Some properties of asphaltic concrete for use in hydraulic
engineering works.
f^
A. Nomograms
For the purpose of determining the bitumen stiffness (S
bit) as a function of the bitumen properties, the tempe-rature and the load time, the Van der Poel nomogram is
being used for quite some time (Ref. 5 ) . Direct
determi-nation through analysis practically no longer occurs. Since 1977 a new nomogram is available (Fig. 12) (Ref. 6)
S H E U FR«NC*IS£ RCSEMCH C Ï M r R E QRUtO'CCXIIICNNE • 0 «3 90 9» S t i t ' n . of rn« Oilumtnou. m i . • N / m * I-H M C R U . W l l M I I H V f to. Of ttw •llummoua t V 'v W » »
Ex S<itfn»i« moooiu» Of tr>e f « o * » ' * a Dina«r 3 3 - 1 0 ' S / m * Vb Voium* o'Oinoc' >S\ VoluTi» o( fwin^f»! aqgr«q«f* flO N
j S l i f f n » , , 1 meouiuk .0* in»m>a ' 1 5.IO"S>m 1 ^ 10 20 30 «O lituminouK binovn
r
Fig. 12. Nomogram for Predicting the Stiffness Modulus of bi-tuminous mixes.
C.C. Moncauban V. Bandsma
Some p r o p e r t i e s of a s p n a l t i c c o n c r e t e for u s e in h y d r a u l i c
e n g i n e e r i n g w o r k s .
/r
for the prediction of mix stiffness (S mix). The parame-ters used are the percentage by volume of the bitumen and
of the mineral aggregate, and the bitumen stiffness. Ap-plication of the technique is limited insofar as that the technique can be used only for the upper stiffness ranges
(S bit > 10^ N/m^, and S mix > 10^ N/m^).
In the "Guideline for application of asphalt in hydraulic engineering" (Ref. 7) the technique has been applied to
predict the S mix of various mixes for use in hydraulic engineering (at one given temperature and load frequen-cy). In order to test the significance of that prediction
it is examined what is the effect of the normal varia-tions in an asphaltic concrete mix for use in hydraulic engineering on the S mix (at a load frequency: 30 Hz)
(Fig. 13). T . O ' C T . I O ' C i . a o " c P E N . 6 0 p. I . . -1.0 6 . 4 . 1 0 ° 2.4 • 1 0 " 5.B « 1 0 ' H n . 4 . 0 B i r . e . S PEN. 70 P.I. . 0 S b l l 1 . 0 . 1 0 ° 3.1 . l o ' P E N - 8 0 P.I. ..1.0 ' b l l 1.3 « 1 0 ^ 5.1 « t o ' V A S M ^ 1 * 1 1 ! L ^ L / ' ' * Smix 3 . 3 . 1 0 ' ° 1 . 9 . I 0 ' ° 7 . 3 . 1 0 * Vm. 85 V Sml« 2 . 7 . 1 0 ' ° 1 . 5 . 1 0 ' ° 5 . 7 . 1 0 ' V m . 82.2 V i Sinl« 2 . 0 - 1 0 ' ° 1 . 2 . 1 0 ' ° 4 . 3 . 1 0 * V m . 8 0 t Sn.l« 2 . 0 . 1 0 ' ° 1 . 2 . 1 0 ' ° 5 . 0 . 1 0 * Vm. 85 V Smix 1.7.10'° 8 . S . I 0 * 4 , 0 . 1 0 * Vm. 82.2 i Smix 1 . 3 . , 0 ' ° 6 . 5 . 1 0 * 3 . 0 . 1 0 ' Vm. 80 !t 1 I 1 S m l « 1 . 4 . 1 0 ' ° 7 . 0 . 1 0 * 3 . 5 . 1 0 * V m . 8 5 S m i x 1 . 1 . 1 0 ' ° « i s . i o * 2 . 7 . 1 0 * V m . 8 2 . 2 * i S . n l x 8 . 0 . 1 0 * 4 . 1 . 1 0 * 2 . 0 . 1 0 * V m , 8 0 y aSMIR_l_«N_. .11 AS MIX IIOIA.II
C.C, Mont aub an U. Bandsma
The bitumen content varies, in practice, from 6.0 to 7.0%
t
i (m/m) and the voids content varies from 2.0 to 6.0?ó
(v/v). The effect thereof on the percentage by volume of bitumen (Vb) and on the percentage by volume of the
mineral aggregate (Vma) produces a variation of -Vb = 12.5 - 15.0 (aver. = 13.8)
Vma = 80.0 - 85.0 (aver. = 82.2)
Next, the effect has been computed of the bitumen proper-ties and the temperature on the bitumen stiffness (at 30 Hz).
! Experience tells that the penetration has been reduced, after application, to 75 - 80 percent of the original pe-netration value. With an allowed P.I. variation from -1.0
to 1.0, bitumen penetrations of 60, 70 and 80, and the associated softening point, the S bit at 0, 10 and 20°C and a 30Hz load frequency has been computed. At 0°C the
upper S bit value appears to be higher by a factor of 5 than the lowest S bit value; that factor is 4.5 an 3.3 at
10°C an 20°C, respectively.
The maximum possible variation of the computed S bit
amounts to - 1.8 x 10^ to 64 x 10^ (N/m^), i.e. a factor of 36.
The total range of variations that can ocuur has been ac-counted for in the S mix that can be read from the
nomo-gram (Fig. 12). These readings were produced for a (refe-rence) mix with average properties, for the extreme S bit
values and the extreme Vma values. (The Vb limits appear-ed to produce negligible variation).
The summary conclusion is, that a mix of asphaltic
con-crete for use in hydraulic engineering with (in view of the applying requirements) allowable variations of the properties and a service temperature of CP-2ü°C, can
Some properties of asphaltic concrete for use in hvdraulic
C.C. Montauban W. Bandsma
Some p r o p e r t i e s of a s p h a l t i c c o n c r e t e for use in h y d r a u l i c
e n g i n e e r i n g w o r k s .
n
show, on the basis of the present nomogram, a dynamic
S-modulus (30 Hz) of 2.0 x 10^ to 33 x 10^ N/m^ (= a factor of 16.5).
In 1980, at the AAPT congress, a nomogram (Fig. 14) was
presented (Ref. 8 ) , that allows simple prediction of the fatigue life of asphalt mixes. Input parameters are: the percentage by volume of the bitumen, the Penetration
In-dex (P.I.), and the S mix at constant deformation or stress fatigue. The result is a fatigue life (= number of load repetitions) at a specific initial strain amplitude
(or stress amplitude).
For asphaltic concrete for use in hydraulic engineering
the effect was analysed of the mix variation referred to above on the allowable initial strain with fatigue.
It can be derived from the nomogram that the smallest eo values are obtained at minimum Vb and PI, and the highest
(..«(••ft mt -a - 1 0 2 - _ - » ' 13 )» IT Vk VOLUMCTIIlC B I T U M E N l \ | C O N T E N T I . «• •c' :LÏ . • • • .... .... „.., .., 1U *.. .... • > -. -. w .. B . .«.-• •"-( • • . i .... -,,, 13 \ - O T * .«»• 4,5 .A MS w-* \ KJ' , «y - • *-\ i A 'JO' \ \ \ ' -\ -\ -\ '• ', \ \ \ ' '> \ \ \ • \ \ \ r — *- \--\ - -" \ \
V
.N
s — \ '''*-\ '''*-\ '. f \ \ '\^ ' \ \ \ ^VrVW "',
1 \ \ \ \
i
'v\\
T , . . ' * • . . . ^ 10 M A I S t t A I M • • » 'Fig. 14. Nomogram for predicting the fatigue life of bitumi-nous mixes.
Some p r o p e r t i e s of a s p h a l t i c c o n c r e t e for use in hTdraulic e n g i n e e r i n g works.
values are obtained at maximum Vb and PI. Using the va-lues Vb = 12.5 and PI = -1.0, Vb = 15.0 and PI = 1.0, and
the reference values (Vb = 13.8 and PI = 0) the initial strain amplitude has been computed if So (= initial S mix) varies from 1.0 x 10^ to 5.0 x 10^° (N/m^). Fig. 15
shows the eo values of the reference at load repetitions of io'* to 10^.
Further the maximum variation of eo is shown for the
ex-treme limits of Vb and PI at load repetitions of 10 , 10
Q
and 10 . The effect, at one and the same So value, is
ap-prox. 20 percent.
Fig. 15. Initial strain amplitude (EO) as a function of ini-tial S mix (SO) and the number of loadcycles.
C.C, Montauban W. Bandsma
C.C. Montauban W. Bandsma
Some properties of asphaltic concrete for use in hydraulic
engineering works.
'9
.5. Testing of measured values aoainst nomoarams
\
For some mixes the initial dynamic stiffness modulus (So)
has been measured using the fatigue test. At the same
time the So has been predicted using the nomogram (Fig.
12). The measured and the predicted values have been
plotted in Fig. 16, all predicted values appearing to be
slightly higher than the measured values. The average
stiffness modulus determined on the basis of the nomogram
is approx. 30 percent higher than the measured stiffness
modulus. This variation falls within the variation limits
of approx. 200 percent, that apply with the use of this
nomogram.
lO^V
io^°4
10'So(pred)
(N/m2)A
/ / 2/
/
/
/
/
•"
/J/
/ 21
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/ .
/
/
/
/
/
/
/
/
/
10' 10 10So(meas)(N/m2)
-H ^ -I '- I 10 11Fig. 16. Measured S mix (Sm) as a function of predicted S mix
(Sp).
C.C, Montauban U. Bandsma
Sone prooerties of asphaltic concrete for use ir. hydraulic engineering works.
10
Finally, the eo values measured with two fatigue analysis have been compared with the calculated eo values. The latter were obtained through application of the nomogram (Fig. 1 4 ) , the input parameters being the measured So and the number of load cycles at fracture. In Fig. 17 the
measured and the calculated eo values have been plotted, which shows that virtually all predicted values lie with-in a variation range of 30 to - 10 percent of the measur-ed value. This variation also falls within the limits of approx. 50 percent that apply if the present nomogram is applied to predict the eo, using a measured So.
3u 2. 10-li 9 ' 8J
£o(pred)
/ / / / . '^ u /A
/ / ' / . * / Temp 20°c Ml A o X C • A £o(meas)('^/M) ' I I I I I ' I f 10 -4Fig. 17. Measured initial strain-amplitude (co-m) as a func-tion of predicted initial strain amplitude (eo-p).
Some properties of asphaltic C.C. Montauban concrece for use in hvdraulic
2/
W. Bandsma engineering works.
6. Conclusions
- The strength analysis confirms the great effect of
tem-perature and deformation rate on the strength level. A difference also appears to exist due to compressive or tensile load. Extrapolation from the fatigue test to
N=1 offers an impression of the dynamic breaking strength that requires further analysis, however.
For this purpose, extrapolation from dynamic analysis
to N=1 can be considered, or extrapolation from strength tests with increasing deformation rate.
- In the lower stiffness range (S mix < 10^ N/m^) it ap-pears to be possible to determine the S mix- S bit
re-lation using various test methods. The S mix level in particular appears to be affected by the bitumen con-tent proportionate to the reduction of the stiffness.
The difference is further apparent between the stiff-ness modulus at compressive load and at tensile load, which is more manifest with the compressive and tensile
tests than with the creep and strain tests.
The upper stiffness range (5 mix > 10 N/m ), measured with dynamic load tests, appears to be fairly well in line with the values measured in the lower stiffness
range.
- The results of the fatigue analysis confirm the fact, that the results depend on the selected test method.
Because, with a test-independent approach (N-Wtot) the results appear not to differ significantly. As a matter
of fact detailed analysis of the significance of this type of fatigue test is desirable within the framework of developing a design model.
Seme properties or a s p h a l t i c concrete for use in hydraulic engineering works.
- Application of nomograms for assessment of the dynamic
stiffness modulus and the fatigue life appears very well possible. However, the commonly occurring mix va-riations can significantly affect these predictions.
This fact will have to be taken into account with further development of design models.
Fot the purpose of recording S mix - S bit relations in the lower stiffness range further research is required,
particularly into the role of the mineral aggregate.
- Research into the service life expectancy must actually
still be launched. The preferred test method to be ap-plied (which is expected to be best suited for this purpose) could be the splitting test. If properly
car-ried out, this "simple" technique can offer information on the strength, the stiffness modulus, and on the Poisson ratio. That information can serve as the basis
for comparative research of new asphaltic concrete and asphaltic concrete of existing revetments. Such an
ana-lysis can produce better understanding of the residual value of asphaltic concrete revetments.
, Montauban Bandsma
C.C. .Montauban W. Bandsma
References;
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Some properties of asphaltic
concrece for use in hydraulic 2 3 engineering works.
C.C, Montauban
Some properties of asphaltic concrete for use in hydraulic
W, Bandsma engineering works,
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