Abrasion resistance of concrete as a two-phase composite material

The International Journal of Cement Composites and Lightweight Concrete, Volume 9, Number3 August 1987

A b r a s i o n res is tance of concre te as a t w o - p h a s e c o m p o s i t e mater ia l

Turan Ozturan * and Ferruh Kocataskin 1

Synops is In this paper, concrete is treated as a two-phase composite material to investigate its resistance to abrasion. A relation based on the mixtures rule is considered; this predicts the abrasion resistance of concrete from the abrasion resistances and volume fractions of the mortar and coarse aggregate phases. Evaluation of the results of tests on composites with coarse aggregate volume fractions ranging from 0 to 0.40 showed good agreement to this relation. The effects of aggregate type and water -cement ratio on abrasion properties of the const i tuent phases of the composite are discussed. The relations between the abrasion depth of concrete wi th length of slide have indicated good agreement to the theory of abrasion offered for metals; and correlations wi th some other mechanical properties of concrete have been demonstrated.

Keywerds Abrasion resistance, concretes, composite materials, wear, aggregates, sands, matrix phase, aggregate phase, water -cement ratio, strength of materials.

INTRODUCTION Two-phase composite models for the study of concrete properties such as elastic deformation, shrinkage and creep have found general acceptance [1-4]. However, there is no published reference on the abrasion of concrete, considering it as a composite material. The aim of the present study [5] is to investigate the abrasion of concrete with a two-phase composite materials approach, by assuming it to be composed of the mortar and coarse aggregate phases. The scope of the investigation covers a survey of literature on theories of wear and previous investigations about abrasion of concrete, and an experimental study involving a variety of mortar and concrete mixes with different types and volume fractions of the coarse aggregate phase and different water -cement ratios.

* Dr: Turan Ozturan is Assistant Professor of Civil Engineering at Bogazici University, Istanbul, Turkey. He received an M.S. degree from Bogazici University and a Ph.D. degree from the Technical University of Istanbul. His research interests are concrete and cement composites.

t Dr. Ferruh Kocataskin, a member of ACI, is Professor of Building Materials at the Technical University of Istanbul, Turkey. He received his Ph.D. degree from the Technische Hochscule, Stuttgart, West Germany. He was a post-doctorate fellow at National Research Council, Canada, in 1955-56; a research associate at Purdue University, USA, in 1956-57; and a visiting professor at Cornell University, USA, in 1962-63. His research interests include concrete and composite materials

Received 20 February 1986 Accepted 21 April 1987

@ Longman Group UK Ltd 1987

0262-5075/87/09305169/$02.00

Evaluation of the test results confirmed the findings of earlier investigations regarding the effects of aggregate type and water -cement ratio and indicated that 'abrasion resistance' of concrete fitted well a simple mixture rule type relation between volume fractions and abrasion resistances of the mortar and coarse aggregate phases. This is the result of the parallel-phase type internal structure of the concrete cross-section subjected to abrasion. They indicated also good agreement to the law of abrasive wear.

THEORIES OF WEAR Wear may be defined as transfer and/or loss of material from surfaces subject to friction. This property has mostly been investigated for metals and certain theories have been developed [6-8]. The following two theories or laws, developed for metals, will be considered for the abrasion of concrete.

Adhesive wear Archard [9] established a model by assuming that spherical wear particles developed at contact points where two surfaces adhered to each other, and he expressed the amount of wear in the following form:

PS V = Z( )

3H (1)

where the volume of wear V is proportional to the applied force P and the sliding distance S, and inversely proportional to the surface hardness H. The constant Z expressed the ratio of contact points taking part in the wear process.

169

Abrasion resistance of concrete as a two-phase composite material Ozturan and Kocataskin

Abrasive wear A hard surface may produce this type of wear by scratching a soft surface, or small pieces of foreign hard matter between two surfaces sliding upon each other may produce it. Khruschow and Babichev [8] gave for this type of wear the following expression, which is very similar to equation (1):

h = K -qaS H (2)

where the depth of wear h is proportional to nominal surface pressure qa and the sliding distance S, and inversely proportional to the surface hardness H. The constant K is called coefficient of wear. Even though the types and properties of nonmetallic materials show a wide variation, it has been pointed out that their wear mechanism may generally be expressed with the wear laws given above for metals [6].

PREVIOUS I N V E S T I G A T I O N S ON ABRASION OF CONCRETE It has generally been accepted that, due to scratching effects, abrasive wear develops on the surface of concrete [10]. Prior [11 ] reported that concrete surfaces may suffer from the abrasive action of: (a) foot traffic and skidding, scraping or sliding of objects; (b) heavy trucking and cars with or without chains; (c) abrasive materials carried by waters and cavitational forces where a high hydraulic gradient is present. Abrasion of concrete has been studied also by various other investigators. Their results may be summarized as follows:

• Resistance of concrete to abrasion increases with the increase in cement content, compressive strength, and the decrease in water-cement ratio [12-15].

• Concrete becomes more resistant to abrasion as the fine and coarse aggregates used are harder, better graded and more resistant to abrasion [15-17].

• Curing and surface finish are among the important factors which affect the abrasion of concrete surfaces [12, 14, 18-20].

• In some cases, special surface hardeners, liquid or dry-shake, are found to increase the resistance of concrete surfaces to abrasion [14, 15, 18, 20, 21-23].

EXPERIMENTAL W O R K In the experimental part of the present study, different series of gap graded concrete mixtures were prepared, in which the qualities and volume fractions of the mortar and coarse aggregate phases were varied. The quality of the mortar was changed by varying its water-cement ratio, while the types of cement and sand were kept constant. The cement-used was a Type t portland cement, and the sand used was a good graded natural sand with a maximum particle size of 4mm. The quality of the aggregate was varied by using three different types of coarse aggregate - crushed limestone, crushed granite, and natural quartz gravel - all in the fraction size of 8-32mm. Results of petrographic examination on these fine and coarse aggregates are reported in Table 1.

Three prism specimens, 500 x 100 x 100mm in size, were fabricated from every mix and subjected to a series of successive tests. Thus it was possible to obtain various mechanical properties of concrete on the same specimen.

Dynamic modulus of elasticity was first determined by the non-destructive resonance frequency test on each prism which was later subjected to centre point loading flexural test to determine the modulus of rupture. Then, one broken piece of each specimen was tested for the compressive strength by the equivalent cube test. Prior to this, the rebound hammer hardness test was under- taken under a small loading on one molded side face. From twelve rebound hammer readings, the average of ten readings, excluding the highest and lowest values, was determined as the Schmidt hardness of the specimen. Individual hammer readings on single specimens had a scatter within the specimen average of +3 on 85% of the specimens whereas on 95% of the mixes, Schmidt hardnesses for the three specimens in each mix remained within the limits of +2 of the average value for the mixture. Following this the load was increased until compressive failure.

Finally, abrasion test on a sample cut from the remaining broken piece of the specimen was performed on a rotating B6hme abrasion table and with the use of powdered corrunclum as abrasive.

Before conducting the abrasion test, the amount of exposed aggregate on the sawn surface of the concrete sample was determined by tracing the aggregate contours on a transparent graph paper (1 mm x lmm grid) and the fractional area of the coarse aggregate phase

Table 1 Petrographic analysis of the aggregates

Sand Crushed limestone (CL) Crushed granite (CG) Natural gravel (NG)

Quartz + Quartzite 31% Calcareous + Calcite 85% Quartz 40-50% Quartz 50-55% Feldspar + Quartz 32% Andesite 10% Feldspar 30-40% Quar tz i te 25-30% Feldspar 30% Silt Stone 5% Biotiteand Opacs 10-20% Chalcedony 20-25% Shell 6% Opal 1-2% Opal 0.3% Calcite 2-3% Basalt 0.3%

170


was determined through counting the number of grids in the area enclosed by the coarse aggregate contours. Correlating the area and the volume fractions of the coarse aggregate phase in concrete mixes, however, showed that the variation was within +0.072 with 95% confidence. Thus the test results were evaluated with respect to the volume fraction of the coarse aggregate phase obtained from the total batch weights.

The German DIN 52108 standard test method [24] was modified slightly to be applied on 100_x 100mm square-shape sawn cross-sections of the concrete samples. The loss in the height of the test sample, measured in mm after a total of 440 turns of the abrasion table, was determined and taken as depth of abrasion of the sample. The reciprocal of this depth of abrasion, on the other hand, was defined as the 'abrasion resistance' and was used as the material property. In this form, it could be given a physical meaning and corresponded well to the parallel phase internal structure of the concrete cross section subjected to wear.

Compositions of various mixes and test results are reported in Table 2.

TEST RESULTS AND DISCUSSION

Variation of abrasion resistance with volume fraction and type of aggregate The main concern of this study was to predict abrasion resistance of concrete from the abrasion properties and volume fractions of its two constituents. Figures 1 and 2 show the variation of the abrasion resistance of concrete versus the volume fraction of the coarse aggregate phase. Each point on these diagrams represents the average result of tests on three specimens. Figures 1 and 2 cover the variation of the abrasion resistance of concrete for the whole range of coarse aggregate volume fractions between 0 and 1.0, even though there actually is an upper limit for the maximum possible volume fraction of the coarse aggregate. This critical limit

Table 2 Mix compositions and test results

Mix

Volume Water-cement Abrasion fraction Type of ratio resistance

Va aggregate w/c (mm-1)

Test Results

Compressive Dynamic Modulus of strength Schmidt modulus rupture (N/mm 2) hardness (kN/mm 2) (N/mm 2)

0 CL O.65 O.27O 0.10 CL 0.65 0.292 0.20 CL 0.65 0.268 0.30 CL 0.65 0.292 0.35 CL 0.65 0.297 0.40 CL 0.65 0.308

0 CL 0.50 0.349 0.10 CL 0.50 0.378 0.20 CL 0.50 0.313 0.30 CL 0.50 0.369 0.35 CL 0.50 0.397 0.40 CL 0.50 0.370

0 CL 0.45 0.451 0.10 C L 0.45 0.452 0.20 CL 0.45 0.427 0.30 CL 0.45 0.402 0.35 CL 0.45 0.398 0.40 CL 0.45 0.397

0 NG 0.50 0.349 0.10 NG 0.50 0.551 0.20 NG 0.50 0.949 0.30 NG 0.50 1.045 0.35 NG 0.50 1.058 0.40 NG 0.50 1.639

0 CG 0.50 0.349 0.20 CG 0.50 0.771 0.40 CG 0.50 0.838

14.0 31.5 18.85 2.1 16.9 30.3 24.65 2.4 16.2 31.2 28.03 2.7 17.1 31.0 31.66 2.9 18.0 34.7 34.70 2.6 18.5 36.3 36.24 2.6

21.8 35.0 25.18 4.2 23.2 34.3 28.78 3.5 25.8 34.9 34.50 3.8 27.3 35.2 39.69 4.2 30.3 36.1 43.21 4.3 29.6 37.8 44.35 4.0

27.1 36.2 29.73 4.3 30.6 36.2 34.42 4.1 29.6 37.1 38.06 4.2 35.0 37.5 42.87 4.5 32.8 36.3 44.26 5.1 36.6 36.9 47.40 4.4

21.8 35.0 25 .18 4.2 20.9 37.3 28.77 2.8 21.2 35.7 3t .90 2.5 23.9 34.0 36.72 3.0 23.6 35.3 38.68 3.2 24.2 34.6 40.46 3.1

21.8 35.0 25.18 4.2 31.8 36.0 30.76 4.2 32.2 38.2 33.04 3.7

CL = crushed limestone NG = natural gravel CG = crushed granite

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0.8

02

E

~- 0.5

o

20.3 . / 3 <

0.2

0.1

X w/c =O.Z,5 0 w/c =0.50

I • w/c=0.6S

I

I mortar

4Ix ! Limestone

x ~ x i X , ~ - - - - - - _ _ __~ I 0 0 o --, -- ~- . . . . . ~f'~

1 0 / ' - • • " I 0 ~ 0 1% ", ',

II ~'~

I

,

' ' ' " 0 . ' 7 ' ' O0 0.1 Q3 (1/. 0.5 OB 0.9 1.0 VoLume fraction of dispersed phase, V a

Figure 1 Variation of abrasion resistance of concrete with volume fraction of crushed limestone coarse aggregate and water-cement ratio

(Va)cr is practically equal to the compactability of the coarse aggregate. Mixtures prepared with coarse aggregate volume fractions in excess of (Va)cr, that is, with volume fractions of mortar phase less than the bulk porosity 1 - (Va)cr of the coarse aggregate, resulted in concretes with air voids remaining unfilled between the coarse aggregate particles. In this case, a three phase composite resulted, changing the internal structure and also the laws governing the properties of the concrete. Interpretation of the test results below will be limited to the first range of coarse aggregate volume fractions, because only this range will correspond to a normal concrete.

In Figures 1 and 2 it is seen that test results corresponding to the same mortar qualities (i.e. same water-cement ratios) and the same types of aggregate are fairly well distributed along straight lines connecting two points: one point representing the abrasion resistance of the mortar phase for Va = O, and the other one representing the same property of the coarse aggregate phase forVa = 1.0. This result has been interpreted that a

simple mixture rule type relation, corresponding to a parallel phase composite model, fitted well to the experimental data, and gave the following composit ion- property relation:

1 1 1 ( - - ) = ( ) V m -k ( - - ) Va

hc hm ha (3)

where ho hm and ha are the abrasion depths in mm and 1 1 1

( - - ) , ( ), and ( - - ) are the abrasion resistances of the hc hm ha

concrete, mortar and the coarse aggregate phases respectively, and Vm and Va are the volume fractions of the mortar and the coarse aggregate phases, respectively, satisfying also the following volume compatibility relation:

V m -I- V a = 1 (4)

The abrasion resistance of the coarse aggregate phase was determined on specimens cut from larger pieces of the parent stone for the l imestone and granite coarse aggregates. The value for the natural gravel

3.2

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t -

{..)

r i o

U'I ° _

¢ )

3C

2.8

2.6

2.4

Z2

20

1.8

1.6

1.4

1.2

1.0

• grave[ ocrushed granite - 'crushed Limestone

C~4

II i

..~1 /

Gravel est imated) ,)

/ /

/ /

/ Granite

~ 1 ' , /

>,~,/ / . ~j-/. ,

.~ 0.8 / o / ,~ ", , . < / / ~ ,, , Ltme-

0.6 ~ / ' / ~1 ", ~stone

>~I ", '.\ ~Ik ~ I "~ •

0.~ Mortar I "- ",, , --.

°0 0.i o) 03 o:5 0:6 0'.e d9 10 VoLume fract ion of dispersed phase,Va

Figure 2 Effect of type and volume fraction of coarse aggregate on the abrasion resistance of concrete with w/c = 0.50

172

Abrasion resistance of concrete as a two-phase composite ma terial Ozturan and Kocataskin

coarse aggregate was estimated. In Figures 1 and 2 it is seen that the relation between abrasion resistance and coarse aggregate volume fraction of the concrete follows Equation (3) well within the range 0 < Va < (Va)cr. ,-,_ (155 However, the experimental points should remain inferior to values predicted by Equation (3) in the range (Va)cr < Va < 1.0, following descending curves directed towards zero abrasion resistance for Va = 1.0, which should be , (~50[ r , the result obtained from fictitious tests on loose coarse aggregates, containing no mortar. Observations during ~ | abrasion tests on mortar specimens confirmed this, by "; 0~5 indicating that the major part of the abrasion losses in the ,- range where volume fraction of sand (Vs) was greater = than its critical value were due to the aggregate pieces 8 getting loose from the specimen surface, because there ~ ~0 was not enough paste to keep them bounded (Figure 3). Q, Thus, the results of abrasion tests on specimens with Vs > (V~)~r were evaluated by considering the volume fraction of not the aggregate, but the cement paste. m 0.35

By considering Equations (3) and (4) jointly, the '- abrasion resistance of concrete may also be expressed as follows, in terms of the abrasion resistances of the ~ 03o two phases and the coarse aggregate volume fraction

< I I I ( )=( )+(.-- hc hm ha

The absolute value of the quantity (

1 --) Va hm (5)

1 1 - - ) i n Equation

ha hm (5) measures the relative effect of the aggregate upon the abrasion resistance of concrete. When this value is large, the abrasion resistance of the composite will be more sensitive to changes in coarse aggregate volume

E

u

t.0

0.8

0.6

(14 L,=

g m

~ 0.2

0 m m m I m

0 0.1 0.2 03 0.4 O. s Vpaste

Vol. ume fraction of constituent

/ /

/ /

. w~4:0.s0 / o , ~ / o w :0.+0 / ' o / - ! \ \

~ ° II

~ 1 . ) °

>~1 i

o16 o) ---Vs O.J* 0,3 ~ 011

phases

Figure 3 Variation of abrasion resistance of mortar with volume fraction of quartz sand

Q25

Ratio of abrasion resistance of mortar to that of the dispersed phase

0.? 0.8 0.9 1.0 1.1 1.2

, /

_*2r±s2 "_ 2s±L "ze of limestone , ~ : ~ /

/ ~ , o " . va=o

a . / ~ ¢ @ o V a :O.z.O

m l | ¢

1,3

025 030 035 0/.0 0/.5 050 Abrasion resistance of matrix phase,1/hrn(mm 4)

Figure 4 Effect of abrasion resistance of the matrix phase on the abrasion resistance of concrete made with crushed limestone aggregate

fraction, as shown by the large slope of the natural gravel coarse aggregate line in Figure 2. The slope of the crushed limestone coarse aggregate line, on the other hand, is seen to be zero in Figure 2, or even negative in Figure 1, indicating that use of coarse aggregates with equal or lower abrasion resistances than that of the mortar will not be beneficial. As seen from Figure 2, use of crushed granite and natural gravel in place of crushed limestone approximately doubled and tripled, respectively, the abrasion resistance of concrete for a volume fraction of Va = 0.3 of the coarse aggregate phase. This is a confirmation of the results obtained by Smith [17] and Liu [15], who reported increases in abrasion resistance of concrete by replacement of crushed limestone through crushed granite or chert coarse aggregates.

Variation of abrasion resistance wi th the quality of mortar It is possible to change abrasion resistance of mortar phase either by changing its water-cement ratio (see Figure 1) or by changing the type of the fine aggregate used in it. Figure 4 shows the variation of the abrasion resistance of concrete, made with crushed limestone coarse aggregate, versus the abrasion resistance of the mortar. It is seen that the resistance of concrete to

1 7 3


050

0~5

E

v l

w L .

c 030 o

L-

< a25

O2O

ova=O

• o Va = 0.z.O

L O -- --_ _Abra_s_sion r_esi..~stanc~.o !

' ~ , , , ~ limestone

d , .

i i i i I

&~ 5 0.50 0.55 E60 0.65 wat e r-cement rat io, w//c

Figure 5 Effect of water-cement ratio on the abrasion resistance of .mortar and of concrete made with crushed limestone aggregate

abrasion increased with the increase in abrasion resistance of its mortar phase. It is also seen that, for concretes containing 0.30-0.40 volume fraction of coarse aggregate phase, the abrasion resistance may be higher or lower than that of the mortar phase, depending on the relative abrasion resistances of its two constituent phases. When the mortar was less resistant than the

limestone, addition of limestone increased the resistance of the composite; when the opposite was true, it decreased the resistance of the composite to abrasion.

Var ia t ion of abras ion resistance w i t h w a t e r - c e m e n t rat io Through its effect on the abrasion resistance of the mortar phase, water-cement ratio is one of the factors influencing the abrasion resistance of concrete. Results in Figures 1 and 5 show this influence, which is in agreement with the results of previous investigators [12, 15-17] who reported that the abrasion resistance of concrete increased with a decrease in its water-cement ratio. The effect of relative abrasion resistances of the two constitutent phases on the abrasion resistance of concrete, discussed above in relation with Figure 4, is also seen here in Figure 5, where for higher values of water-cement ratio, the abrasion resistance of concrete is higher than that of its mortar phase, whilst for lower values of the water-cement ratio, it is lower, implying that addition of these coarse aggregate particles into the more resistant mortars will give no benefit. The critical value of water-cement ratio for which the abrasion resistances of the two phases of the composite with limestone coarse aggregate are equal is seen to be around 0.48 in Figure 5.

A g r e e m e n t of t es t results to the t h e o r y of abrasion The test results showed also good agreement to the law of abrasive wear given above as h = K (q~S/H). In Figure 6 it is seen that the amount of abrasion hc increased with number of turntable rotations S in linear relation for a large number of these rotations. In Figure 7, it is seen that the amount of abrasion hc decreased with increasing compressive strength and Schmidt hardness. Corre-

10.0

9.0

8.0 E E

"7.0 2 ~'6.o

s.o

c L~3

,- 3.0

2~

IO

0 o

gw°;~:r0~d sand+crushed l 'mest°ne ~ , / / O , , / f e O / ' /

~ | m m m I m m i I i i ! m i

88 176 264 352 4/,0 528 616 ?04 ?92 880 968 1056 11/.4 1232 TurntabLe rotations,S

Figure 6 Variation of the abrasion depth with number of rotations of the turntable of the B6hme machine

174


E 30 E

¢ _

X211

t -

o

"~ 1.0 i _

<

0 10

&O

E

o c -

" o

• c~ 1.[1 ell

<

t

2 3.0/, hc= R 0 6 6

r = - 0 .792

1"5 20 . . . . 25 30 35 40 Compressive strength,R (N mm 2)

h = ?.84-0.142 (Sc) r = - 0209

t'a 2"9 3"o 3"2 35 36 37 38 39 Schmidt hardness, Sc

40 41

45

Figure 7 Variation of the abrasion depth with compressive strength and Schmidt hardness

lation coefficients for these relationships were 0.79 and 0.71 respectively. These data indicate a significant correlation between abrasion and both the compressive strength and the Schmidt hardness of concrete at the 99% confidence level. The scope of this study, on the other hand, did not allow any evaluation with respect to the nominal surface pressure qa.

CONCLUSIONS The following conclusions may be drawn in the light of the test results and discussions presented above:

1. Considering it is a two-phase composite material, the abrasion resistance of concrete may be predicted in terms of the abrasion resistances and volume fractions of its constitutent mortar and coarse aggregate phases. Experimental data fit well a simple mixture rule relation between composition and properties for this purpose.

2. Abrasion resistance of concrete increases with increase in volume fraction of the phase with higher resistance. Thus, if the abrasion resistance of the coarse aggregate is lower than that of the mortar, then there is no benefit in using that kind of aggregate. For a given mortar quality the abrasion resistance of the concrete may be increased through the use of hard coarse aggregates like crushed granite or quartz gravel used in the study.

3. Water-cement ratio and the type of fine aggregate are two important factors that affect the abrasion resistance of mortar, and through it the abrasion resistance of the concrete. Decreasing the water-cement ratio and using superior quality fine aggregates increase the abrasion resistance of both the mortar phase and the concrete.

4. Results of tests obtained with the B6hme abrasion apparatus on concrete show good agreement to the law of abrasive wear.

175


5. As explained earlier, the abrasion tests were performed on the sawn surfaces of the concrete samples for the purpose of investigating the two-phase internal structure model and fulfilling the aim of the study. It is appreciated that, at least at early stages of service, the finishing techniques will have a major effect on the performance of concrete slabs which are subjected to abrasion. However, sooner or later during service life, the relatively thin mortar layer on the finished surfaces of concrete pavements will be abraded and a surface containing both mortar and coarse aggregate will be subjected to abrasive action. For this final stage, the results of the present investigation may be extended for some practical evaluations.

REFERENCES 1. Holliday, L. 'Composite Materials', Elsevier

Publishing Company, 1966. 2. Hansen, T. C. 'Creep and stress relaxation of

concrete', Swedish Cement and Concrete Research Institute, Proceedings, No. 31, Stockholm, 1960.

3. Hirsch, T. J. 'Modulus of elasticity of concrete affected by elastic moduli of cement paste matrix and aggregate', Journal, American Concrete Insti- tute Proceedings, Vol. 59, March 1962, pp. 427-51.

4. Hashin, Z. 'The elastic moduli of heterogenous materials', Transactions ASME, Journal of Applied Mechanics, Vol. 29, Series E, No. 1, March, 1962, pp. 143-50.

5. Ozturan, T. 'Study of abrasion of concrete as a two-phase composite material', Ph.D. Thesis submitted to the Faculty of Civil Engineering, Tech- nical University of Istanbul, Turkey, October, 1983.

6. Bowden, F. P. and Tabor, D. 'The Friction and Lubrication of Solids', Clarendon Press, Oxford. Part 2, 1964.

7. Suh, N. P. and Turner, A. P. L. 'Elements of Mechanical Behaviour of Solids', McGraw-Hill, 1978.

8. Kragelzkii, I. V. 'Friction and Wear', Translated from Russian by Leo Renson, Butterworths, London, 1965.

9. Archard, J. F. 'Contact and rubbing of flat surfaces', Journal of Applied Physics, Vol. 24, No. 8, August 1953, pp. 981-8.

10. Robinowicz, E. 'Friction and Wear of Materials', John Wiley, 1966.

11. Prior, M. E. 'Abrasion resistance', American Society for Testing and Materials, STP 169-A,

Concrete and Concrete Making Materials, 1966, pp. 246-60.

12. Sawyer, J. L. 'Wear tests on concrete using the German standard me*hod of test and machine', American Society for Testing and Materials, Pro- ceedings, Vol. 57, 1957, pp. 1143-53.

13. Witte, L. P., and Backstrom, J. E. 'Some properties affecting the abrasion resistance of air-entrained concrete', American Society for Testing and Mater- ials, Proceedings, Vol. 51, 1951, pp. 1141-53.

14. ACI Committee 201, 'Guide to Durable Concrete', Journal, American Concrete Institute, Proceedings, Vol. 74, No. 12, December, 1977, pp. 573-609.

15. Liu, T. C. 'Abrasion resistance of concrete', Journal, American Concrete Institute, Proceedings, Vol. 78, No. 5, September-October 1981, pp. 341-50.

16. a'Court, C. L. 'Mix design and abrasion resistance of concrete', Symposium on Mix Design and Qual- ity Control of Concrete, London, May 1954, pp. 77-91.

17. Smith, F. L. 'Effect of aggregate quality on resistance of concrete to abrasion', American Society for Testing and Materials, STP 205, Cement and Con- crete, 1956, pp. 91-105.

18. Fentress, B. 'Slab construction practices compared by wear tests', Journal, American Concrete Insti- tute, Proceedings, Vol. 70, No. 7, July 1973, pp. 486-91.

19. Burnett, G. E. and Spindler, M. R. 'Effect of time of application of sealing compound on the quality of concrete', Journal, American Concrete Institute, Proceedings, Vol. 49, November 1952, pp. 193- 200.

20. Li, S. 'Wear-resistant concrete construction', Jour- nal, American Concrete Institute, Proceedings, Vol. 55, February 1959, pp. 879-92.

21. Price, W. H, and Wallace, G. S. 'Resistance of concrete and protective, coatings to forces of cavitation', Journal, American Concrete Institute, Proceedings, Vol. 46, October 1959, pp. 109-20.

22. ACI Committee 302, 'Guide for Concrete Floor and Slab Construction', Concrete International, Design and Construction, Vol. 2, No. 6, June 1980, pp. 51-96.

23. Hersey, A. T. 'Causes of floor failures', Journal, American Concrete Institute, Proceedings, Vol. 70, No. 6, June 1973, pp. 426-9.

24. DIN 52108, Beuth-Vertrieb GmbH, Berlin 30, August, 1968.

25. Graf, O., Albrecht, W. and Schaffler, H. 'Die Eigen Schaften des Betons', Springer-Verlag, Berlin, 1960, pp. 219-27.

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Abrasion resistance of concrete as a two-phase composite material