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The effect of stabilizing additives of waste pulp and paper industry on the properties of crushed stone-mastic asphalt concrete.

INTRODUCTION

At present and in the near future, there is not a considerable alternative to nonrigid pavement of bitumenbased materials. At the same time, asphalt mixtures used for laying upper and lower pavement courses under increasing traffic load cannot provide a complex of functional performance properties needed for upper pavement courses. It is an established fact that the life of nonrigid capital-type asphalt pavement of hot mixture is 5-7 years instead of 10-15 years required. This situation is conditioned by several factors: carrying base capacity, stone materials and bitumen quality, the level of work execution. Structural and mechanical properties of asphalt concrete as the material, for which specifications and the theoretical foundations were developed at the beginning of the last century, should be also taken into account.

Nowadays, the main problems in road construction are:

--traffic increase;

--increased load on the axle;

--noise reduction;

--the use of recycled materials;

--security aspects;

--durability (the highest possible service life);

--facilities for drivers;

--the need for economical efficiency technologies.

Crushed stone-mastic asphalt concrete meets the above requirements.

Crushed stone-mastic asphalt concrete was developed in Germany in the 1960s. Due to its very high economical effect, it has been used all over the world, regardless of climatic conditions.

Crushed stone-mastic asphalt concrete provides for maximum resistance to permanent deformation due to the friction inside crushed stone frame. Pavement itself reduces drivers' fatigue. A high content of coarse aggregate makes an excellent road, i.e. a very good wheel adhesion to pavement. At the same time, the structure of the crushed stone-mastic asphalt concrete surface significantly reducing noise. When it rains, it reduces the amount of spray and aquaplaning as an additional effect, decreases glare brightness of road pavement and improves visibility of road markings. The improvement in water resistance, cracking resistance, lack of stratification, and the presence of a thick binder film around a mineral part are a pavement durability guarantee. Some examples of crushed stone-mastic asphalt concrete application in different countries show that the life of this type of pavement is 20 years or more. Reduced maintenance costs lead to savings.

Methods:

Crushed stone-mastic asphalt concrete was tested in accordance with the Russian Federation State Standard 12801-98.

When preparing mixtures in the laboratory, using a hot technology, mineral materials (gravel, sand, mineral powder) are pre-dried and bitumen is dehydrated.

Mineral materials in amounts specified in terms of composition are weighed into a vessel, stirred occasionally, and heated up to the temperature indicated in Table 1; and the required amount of binder heated in a separate container is added.

The mixtures of mineral materials with organic binder are stirred finally until all the components are combined completely and uniformly.

To determine the physical and mechanical properties of mixtures asphalt concrete samples are made in accordance with the Russian Federation State Standard 31015-2002 in 71.4 mm-diameter typical cylindrical moulds. The samples are packed by vibration and then they are packed additionally by compacting.

Determination of the binder runoff index:

The essence of the method is to assess the ability of a hot crushed stone-mastic asphalt concrete mixture to keep the binder contained in it. The prepared crushed stone-mastic asphalt concrete mixture is heated up to a maximum temperature in accordance with Table 1 and mixed thoroughly. The drying oven is also heated up to a specified temperature, which is maintained a permissible error of [+ or -] 2[degrees]C when conducting the tests.

An empty glass is weighed, then it is placed in the drying oven and kept there at the temperature indicated in Table 3 for at least 10 minutes. After that the glass is placed on the scales and 0.9-1.2 kg of the mixture is put quickly into it, then it is weighed and a cover glass is put on it.

The glass containing the mixture is placed in the drying in which it is kept the maximum temperature indicated in Table 3 for (60 [+ or -] 1) min. Then the glass is taken out, the cover glass is taken away, and the mixture is removed by turning the glass over without shaking it upside down for (10 [+ or -] 1) seconds. Then the glass is put bottom down again, cooled for 10 minutes and weighed together with the remaining binder and mixture adhered to its inner surface.

Binder runoff,% by mass, is determined by the formula:

B = [g.sub.3] - [g.sub.1]/[g.sub.2] - [g.sub.1] 100, (1)

where [g.sub.1], [g.sub.2], [g.sub.3]--mass of the empty glass, the glass containing the mixture and the glass without it, respectively, g.

Determination of water saturation

The essence of the method consists in determining the amount of water absorbed by the sample under the specified saturation conditions. The mixture samples weighed in the air and in water are placed into a vessel containing water of the temperature of (20 [+ or -] 2)[degrees]C. The water level above the samples should be not less than 3 cm.

The vessel with the samples is put into the vacuum unit, in which the pressure is created and maintained at the level of not more than 2000 Pa for one hour.

The pressure was then adjusted to atmospheric one and the samples are kept in the same vessel with water of (20 [+ or -] 2)[degrees]C for 30 minutes. Thereafter, the samples are removed from the vessel, weighed in water, wiped with a soft cloth and weighed in the air.

Water saturation of the sample W,%, is determined by the formula:

W = [g.sub.3] - [g.sub.1]/[g.sub.2] - [g.sub.1] x 100, (2)

where g--the mass of the sample weighed in the air, g;

[g.sub.1]--the mass of the sample weighed in water, g;

[g.sub.2]--the mass of the sample kept in water for 30 minutes and suspended in the air, g;

[g.sub.3]--the weight of the water-saturated sample weighed in the air, g.

Determination of compressive strength

The test samples are prepared on the basis of the above procedure. The samples are incubated before the test at the predetermined temperature (50 [+ or -] 2) or (20 [+ or -] 2)[degrees]C. The temperature of (0 [+ or -] 2)[degrees]C is created by mixing water with ice. The samples of hot mixtures are kept in water at the predetermined temperature for one hour.

Compressive strength R, MPa, is calculated by the formula:

R = P/F x [10.sup.-2], (3)

where P - breaking load, N;

F--initial cross-section area of the specimen in [cm.sup.2];

[10.sup.-2]--scaling factor in MPa.

Determination of split tensile strength:

The method consists in determination of the load required for splitting the sample along a generating line. The samples are incubated in water before the test at the predetermined temperature (0 [+ or -] 2)[degrees]C for at least one hour. The temperature of (0 [+ or -] 2)[degrees]C is created by mixing water with ice.

The split tensile strength [R.sub.p], MPa, is calculated by the formula:

[R.sub.p] = P/hd [10.sup.-2] (4)

where P--breaking load, N;

h--sample height, cm;

d--sample diameter, cm;

[10.sup.-2]--scaling factor in MPa.

The main part:

The study was performed as part of the state task of the Ministry of Education and Science of the Russian Federation No. 7.4049.2011, as well as the project of the strategic development of Belgorod State Technological= University named after V.G. Shukhov N0. 2011-CR-146.

Crushed stone-mastic asphalt concrete is the material developed specifically for laying pavement upper layers of very heavy traffic roads (Schumaher, G., 2002). A stabilizing additive is widely used in the process of its production, because crushed stone-mastic asphalt concrete gains its unique properties with the help of this additive. It is therefore necessary to pay special attention to the necessity of its application and the correctness of its choice.

The use of the stabilizing additive is conditioned by a high content of bitumen in crushed stone-mastic asphalt concrete mixtures (6.5-7.5%). To prevent leakage of the binder a stabilizing additive is introduced in the mixture; it absorbs unstructured binder. The nature of the adsorption process between the fiber surface and bitumen is conditioned by the action of molecular forces and the quantity of surface energy. As a result of the adsorption, an increased viscosity adsorption layer is formed on the fiber surface.

From a thermodynamic point of view (Kolbanovsky, A.S., 1973), bitumen adhesion with mineral material (including a fiber) is determined, mainly, by the presence of the material surface active groups provoking chemisorbing processes of bitumen acid components, and it is an important factor for making qualitative and durable building conglomerate.

The differences in surface properties of fibrous materials produce a considerable effect on the nature of sorption processes by interacting with bitumen. The choice of fiber material having a high sorption capacity is the first step towards the creation of specified properties of crushed stone-mastic asphalt concrete.

Initially, the so-called free cellulose fibers cut and "feazed" in a special way were used as a stabilizer. However, some mixture defects were more often found when mass production of crushed stone-mastic asphalt concrete began. These are mixture segregation and bitumen spots of various size (sometimes those of a vast area) on the newly laid road surface directly in the process of compaction. After the additional study, it was found that loose fibers had serious drawbacks, as under, despite the excellent stabilizing effect:

--higher hygroscopicity: cellulose fibers like wool absorb perfectly environmental moisture, which makes it impossible their further use;

--loose fibers impede the distribution of the mixer;

--a tendency to clump together, which impedes dosing and further distribution in the mixer;

--high probability of burning: when loose fibers fall onto superheated inert materials (190-200 [degrees]C) in the mixer, in the first instance, OH intermolecular bridges bonding cellulose molecules with binder and stone ones are burnt (GroBhans, D., 1998).

The creation of granular additives has been further evolutionary development of a family of stabilizers. Granular additives are the fibers pressed into pellets and treated with modifying compounds or not treated with them (Ilina, T.N., 2010). A fibrous additive must be homogeneous, impurity-free, resistant to heating up to the temperature of 220[degrees]C, and have a moisture content not exceeding 8% by mass (Kostin, V.I., 2009). Three types of granular additives should be distinguished: granules containing pure cellulose, granules with addition of paraffin (wax, stearine) to reduce hygroscopicity, and granules, in which each fiber has a cellulosic bituminous coating. The latter eliminates moisture saturation of cellulose fibers, which provides for a simple and reliable dosing system, a perfect distribution in the mixer without increasing dry mixing time and, as a result, making a stable mixture. Besides, the availability of bitumen pavement prevents fibers from being burnt when they are applied onto a hot inert material.

Since crushed stone-mastic asphalt concrete mixtures must be resistant to delamination during transportation, loading and unloading, the most important quality parameter of a stabilizing additive in the process of its development is its runoff index determined according to the Russian Federation State Standard 31015-2002. We have developed and studied various compositions of stabilizing additives produced from industrial wastes for conducting tests. They have the conventional names, like SA-1 80, SA-2 80, SA-70-1, SA2 70, SA-70-3 SA-70-4, SA-70-5, SA-70-6 as compared with the well-known additive having a "VIATOP-66" trade name. The pictures of the additives mentioned above are given in Fig. 1.

f-SA-70-4; g-SA-70-5; h-SA-70-6; i-Viatop-66.

The results of the binder run-off index are shown in Table 2.

According to Table 1, all additives meet the requirements of the Russian Federation State Standard 310152002 in terms of the binder run-off index and are applicable for further study.

To study the effect of stabilizing additives on physical and mechanical characteristics of crushed stonemastic asphalt concrete we tested the samples prepared with the use of granite crushed stone of 5-10 mm fractions produced at Novopavlovsk ore-dressing and processing plant and screened sand of 0-5 mm fractions produced at Pavlovsk granite quarry. MP-1 fine-ground limestone of "Gurovo-Beton" plant was applied as mineral powder. We used petroleum bitumen of BND 60/90 brand produced at Ryazan oil processing company; it meets the requirements of the Russian Federation State Standard 22245-90. Bitumen containing asphalt acid and bitumen containing a carboxyl group interact chemically with both carbonate rock and basic metal oxides.

To ensure a constant grain composition of the test asphalt concrete the material was prescreened, and then, a mineral part of the mixture was prepared for each batch of these individual mineral fractions.

The study results of physical and mechanical characteristics of crushed stone-mastic asphalt concrete are given in Table 3.

Table 3 shows that all the mixtures tested meet the requirements of the Russian Federation State Standard 31015-2002 in terms of all indices.

When comparing the properties of crushed stone-mastic asphalt concrete with VIATOP-66, SA-80-1, SA80-2, SA-70-1, SA-70-2, SA-70-3, SA-70-4, SA-70-5, SA-70-6 additives, it is clear that the mixture with the test SA-70-1 and SA-70-5 additives have better physical and mechanical characteristics. For example, the compressive strength of the crushed stone-mastic asphalt concrete samples with SA-70-5 fiber additive at the temperature of 20 [degrees]C is the same as the compressive strength of those with of the VIATOP- 66 additive. In case of the crack resistance test of the samples, crushed stone-mastic asphalt concrete with the SA-70-1, SA-70-2, SA-70-3, SA-70-4, SA-70-5, SA-70-6 additives has a greater strength as compared with that having the VIATOP-66 additive. The compressive strength of all the crushed stone-mastic asphalt concrete mixtures at the temperature of 50[degrees]C, except for those with SA-80-1 and VIATOP- 66 additives turned out to be approximately the same.

In view of the above, one can propose to use industrial wastes with conventional names, like SA-70-1 and SA-70-5 as a stabilizing additive for crushed stone-mastic asphalt concrete.

The main disadvantage of any type of asphalt concrete as a road-building material is great dependence of its strength and deformation properties on temperature. If temperature increases, viscosity of bitumen contained in asphalt concrete decreases, bonds of mineral particles weaken, which results in strength reduction.

These strength changes worsen road pavement life. When strength indices change, deformation behaviour of asphalt concrete also changes. In view of operational conditions of road pavement, this material should be sufficiently deformation-resistant at high summer temperatures, i.e. heat-resistant in terms of temperature fluctuations.

When using SA-80-1, SA-2 80, SA-70-1, SA-2 70, SA-70-3, SA-70-4, SA-70-5 SA-70-6 additives, the heat resistance factor ([R.sub.20]/[R.sub.50]) of crushed stone-mastic asphalt concrete has approximately the same value as in case of introduction of ordinary additives, which is indicative of high operational composite properties at both low winter and high summer temperatures. The results are presented in Figure 2.

The most important property of crushed stone-mastic asphalt concrete predetermining this material durability is its structure stability under changing moisture and temperature conditions. Like most other porous building materials, crushed stone-mastic asphalt fails, mainly, due to prolonged wetting

If asphalt concrete pavement is wetted for a long time, it can fail due to weakening structural bonds at the expense of the flaking of mineral grains, which leads to pavement wear and pot-hole formation [6-10]. Asphalt concrete water resistance depends on density and stability of adhesive bonds. Water as polar liquid wets all mineral materials well, which means that water diffusion under a bitumen film may occur in case of a long contact with mineral grains treated with bitumen. In addition to it, water penetrates into microdefects of the asphalt concrete structure, causing adsorption reduction in material strength at the expense of the decrease in surface energy of crack side, and the weakening of structural bonds at the crack top as far as a crack develops.

Asphalt concrete strength and water resistance indices are largely dependent on the properties of mineral materials used.

A water resistance index of any type of asphalt concrete is a water resistance factor, demonstrating how strength decreased after water saturation, and it also characterizes asphalt concrete ability to resist damaging effects of water.

The tests were conducted, using crushed stone-mastic asphalt concrete. Viatop-66 and SA-80-1, SA-80-2, SA-70-1, SA-70-2, SA-70-3, SA-70-4, SA-70-5, SA-70-6 industrial wastes were used as stabilizing additives. Long water resistance factors were determined after 15 days' water saturation. The obtained property indices of crushed stone-mastic asphalt concrete samples are shown in Table 4.

Table 4 demonstrates that the water resistance factor of crushed stone-mastic asphalt concrete fiber under study remains higher after 15 days' water saturation as compared with that having an ordinary fiber. Therefore, after 15 days' water saturation, the water resistance factor of the test SA-80-2, SA-70-1, Sa-70-5, SA-70-6 samples decreases on average by 4.2%, and the factor of those with an ordinary VIATOP binder stabilizer--by 5.2%.

Findings:

The stabilizing additives produced by using waste paper according to two technologies were studied. It was found that in terms of a runoff factor the granular additives met the requirements of the State Standard 310152002 and not worse than ordinary additives. The effect of stabilizing additives produced from cellulose pulp and paper wastes on physical and mechanical characteristics of crushed stone-mastic asphalt concrete having the composition selected was studied. It was established that crushed stone-mastic asphalt concrete based on the raw materials under study was similar to the material with the use of ordinary raw components in terms of strength, water saturation, swelling, water resistance, and shear resistance. The study results demonstrate that industrial wastes can be applied as raw materials for making stabilizing additives to be used for production of crushed stone-mastic asphalt concrete.

Conclusion:

Thus, the improvement in physical and mechanical properties of bituminous composite with the use of additives from pulp and paper industry wastes as a stabilizer will allow producing high-quality crushed stonemastic asphalt concrete, having a longer pavement life.

ARTICLE INFO

Article history:

Received 25 January 2014

Received in revised form 12 March 2014

Accepted 14 April 2014

Available online 5 May 2014

REFERENCES

Schumaher, G., 2002. Splittmastixasphalt mint Zusats von synthetischen Fasern / G. Schumaher, L. Bullinger, J. Lehdrich // Bitumen. 4: 157-158.

Kolbanovsky, A.S., Road bitumen / A.S. Kolbanovsky, V.V. Mikhailov, 1973. Moscow: Trantport, 261.

GroBhans, D., 1998. Ursachen fur Verformungen in Asphaltbefestigungen mit

Splittmastixasphaltdeckschichten am Beispiel des Autobahnnetyes in Brandenburg / D. GroBhans, P. Pohlmann, H-R. Reuter // Bitumen., 2: 50-59.

Ilina, T.N., 2010. Constructive and technological improvement of aggregates for the granulation of powdered materials / T.N. Ilyin, M.V. Sevostianov, E.A. Shkarpetkin // Herald of the Belgorod Shukhov state technological university, 2: 100-102.

Kostin, V.I., 2009. Stone mastic asphalt paving / V.I. Kostin // Tutorial on the course "New technologies in road construction" for the students specialty 270205 - "Highways and airports" pp: 65.

Pechenyy, B.G., 1975. On the change in the composition and properties of bitumen during aging at different temperatures / B.G. Pechenyy, E.P. Zhelezko // Refining and Petrochemicals., 8: 10-13.

Strokova, V.V., 2009. The analysis of organic-based composites with the genesis and dimensional levels of minerals / V.V. Strokova, I.V. Zhernovski, S.A. Lyutenko, M.S. Lebedev // Herald of the Belgorod Shukhov state technological university, 2: 28-32.

Zelic, I., 2000. Efficiency of silica Fume in Concrete / I. Zelic, D. Rusic, R. Krstulovic // Ibausil: Bauhaus Univ. Weimar., 2: 659-668.

Duval, R., 1998. Influence of silica fume, on the workability and the compressive strength of high-performance concretes / R. Duval, E.H. Kadri // Cem. and Concr. Res., 28(4): 533-547.

Tabor, D., 1981. Principles of adhesion bonding in cement and concrete / D. Tabor // Adhes. Probl. Resycl. Concr. Proc. NATO Adv. Res. Inst., Saint Remy--Les. Chevreus, 25-28 Nov., 1980.--New York, London, pp: 63-87.

Valentina Vasilievna Yadykina, Anatoly Mitrofanovich Gridchin, Anna Ivanovna Trautvain

Belgorod State Technological University named after V.G. Shukhov, Russia, 308012, Belgorod, Kostyukova, 46

Corresponding Author: Valentina Vasilievna Yadykina, Belgorod State Technological University named after V.G. Shukhov, Russia, 308012, Belgorod, Kostyukova, 46

Table 1: Heating temperature of the materials
depending on binder indices.

                     Heating temperature, [degrees]C
                     depending on the binder indices
Name of materials    (depth of needle penetration at 25
                     [degrees]C, 0.1 mm)

                     40-60     61-90     91-130    131-200   201-300

Mineral materials    170-180   165-175   160-170   150-160   140-150
Binder               150-160   140-150   130-140   110-120   100-110
Mixture              150-160   145-155   140-150   130-140   120-130

Table 2: The binder run-off index.

                        State Standard
Description             31015-2002        VIATOP   SA-80-1   SA-80-2

Content of additives    0.2-0,5           0.4      0.4       0.4
in a mixture, %

Content of bitumen      6.5-7.5           6.5      6.5       6.5
in a mixture, %

Binder run-off          no more 0.20      0.13     0.14      0.15

Description             SA-70-1   SA-70-2   SA-70-3   SA-70-4

Content of additives    0.4       0.4       0.4       0.4
in a mixture, %

Content of bitumen      6.5       6.5       6.5       6.5
in a mixture, %

Binder run-off          0.10      0.11      0.09      0.07

Description             SA-70-5   SA-70-6

Content of additives    0.4       0.4
in a mixture, %

Content of bitumen      6.5       6.5
in a mixture, %

Binder run-off          0.12      0.13
index, % by mass

Table 3: The indices of physical and mechanical properties
of crushed stone-mastic asphalt.

                       Requirements for the
                       State Standard
Index description      31015-2002             SA-80-1   SA-80-2

Water saturation,%     from 1.0 to 4,0        1.8       1.2
by volume of samples
moulded from
mixtures

Compressive            2.2                    3.8       3.7
strength, MPa, not     0.65                   1.4       1.1
less than: at 20
[degrees]C at
50[degrees]C

Crack                  2.5-6                  3.8       3.2
resistance--the
tensile strength in
case of cracking at
0[degrees]C, MPa

Index description      SA-70-1   SA-70-2   SA-70-3   SA-70-4

Water saturation,%     1.6       1.1       1.3       1.4
by volume of samples
moulded from
mixtures

Compressive            3.7       3.3       3.4       3.4
strength, MPa, not     1.2       1.1       1.1       1.1
less than: at 20
[degrees]C at
50[degrees]C

Crack                  4.4       4.3       4.3       4.2
resistance--the
tensile strength in
case of cracking at
0[degrees]C, MPa

Index description      SA-70-5   SA-70-6   VIATOP

Water saturation,%     1.8       1.3       1.4
by volume of samples
moulded from
mixtures

Compressive            3.9       3.6       3.9
strength, MPa, not     1.3       1.2       1.3
less than: at 20
[degrees]C at
50[degrees]C

Crack                  4.5       4.1       4.0
resistance--the
tensile strength in
case of cracking at
0[degrees]C, MPa

Table 4: Long asphalt concrete water resistance.

                    The State
Water saturation    Standard
period, days        requirements   SA-80-1   SA-80-2   SA-70-1

0                   --             0.95      0.97      0.97

15                  0.85           091       0.93      0.93

Water saturation
period, days        SA-70-2   SA-70-3   SA-70-4   SA-70-5   SA-70-6

0                   0.94      0.95      0.97      0.98      0.98

15                  0.91      0.89      0.92      094       0.93

Water saturation
period, days        VIATOP-66

0                   0.97

15                  0.92
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Author:Yadykina, Valentina Vasilievna; Gridchin, Anatoly Mitrofanovich; Trautvain, Anna Ivanovna
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Date:Apr 1, 2014
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