An investigation on the wear resistance of high strength concretes

An investigation on the wear resistance of high strength concretes

Wear 260 (2006) 615–618 An investigation on the wear resistance of high strength concretes S¸. Yazıcı ∗ , G. ˙Inan ˙ Civil Engineering Department, Eg...

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Wear 260 (2006) 615–618

An investigation on the wear resistance of high strength concretes S¸. Yazıcı ∗ , G. ˙Inan ˙ Civil Engineering Department, Ege University, 35100 Izmir, Turkey Received 1 June 2004; received in revised form 3 February 2005; accepted 16 March 2005 Available online 31 May 2005

Abstract In this study, a relationship was determined between the mechanical properties (compressive and splitting tensile strengths) and wear resistance of high strength concretes (HSC) having compressive strength between 65 and 85 MPa. For this purpose, 108 test specimens were produced from six different mixtures. After 28 days standard curing, compressive strength, splitting tensile strength, and wear resistance tests were performed on the specimens. From the test results, mathematical expressions were developed to estimate the wear resistance of concrete regarding their compressive strength and splitting tensile strength. As result a reliable relationship was produced from this properties. © 2005 Elsevier B.V. All rights reserved. Keywords: Wear resistance; Mechanical properties; Fly ash; Silica fume

1. Introduction Abrasive wear is known to occur in pavements, floors, hydraulic structures such as tunnels and dam spillways or other surfaces upon which friction forces are applied due to relative motion between the surfaces and moving objects. The resistance of concrete to wear is influenced by variables such as strength, aggregate properties, surface finish and type of hardeners or toppings. It is well establish that concrete wear resistance increases with increasing compressive strength and tensile strength [1,2]. In order to develop concrete with high wear resistance, it is desirable to use hard surface material, aggregate and paste having low porosity and high strength [2]. Wear resistance of concrete depends a great deal on the hardness of the aggregates used. High strength concretes with low water/cement ratio (W/C) is less dependent on aggregate type and the use of a low W/C can provide a dense, strong concrete which is resistant to wear [1]. High strength is made possible by reducing porosity in homogeneity and microcracks in concrete and in the interface between cement paste and aggregate (the transition zone). This can be achieved by using super plasticizers ∗

Corresponding author. Tel.: +90 232 3886026; fax: +90 232 3425629. E-mail address: [email protected] (S¸. Yazıcı).

0043-1648/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2005.03.028

and supplementary cementing materials such as fly ash, silica fume, granulated blast furnace slag and natural pozzolan [3,4]. Fortunately, most of these materials are industrial byproducts and help in reducing the amount of cement required to make concrete less costly, more environmental friendly and less energy intensive [3]. In this research, the effect of compressive strength and splitting tensile strength on wear resistance of concrete was taken into consideration. Besides, an expression predicting loss on wear including the parameters mentioned above was proposed.

2. Experimental study 2.1. Materials In this study, an ordinary portland cement (PC), silica fume (SF), and fly ash (FA) were used as cementitious materials. Also, fly ash was used as an aggregate replacement in some concrete mixtures. The chemical composition and some physical properties of portland cement, silica fume and fly ash are given in Table 1. The coarse aggregate was crushed basalt with maximum size of 16 mm. The fine aggregate was a silica based natural sand and with maximum size of 4 mm.

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Table 1 Chemical compositions of cements and mineral admixtures Chemical analysis (%)

PC

SiO2 Al2 O3 Fe2 O3 CaO MgO SO3 Insoluble residue Loss on ignition Na2 O K2 O Physical analysis Specific gravity Blaine specific surface (cm2 /g)

19.7 5.1 2.6 64.2 1.4 2.4 0.4 1.8 0.3 0.8 3.06 3470

SF

FA

94–95 0.4–1.35 0.4–1.0 0.6–1.0 1–1.5 – – 0.85 2.27 0.59

42.4 27.6 5.5 23.0 2.0 – – 1.5 0.5 0.9

2.24

2.33

Compound composition (Bogue) (%) C3 S 59.35 C2 S 11.71 9.22 C3 A 7.79 C4 AF

Fig. 1. Abrasion test apparatus as specified in TS 699.

Saturated surface dry specific gravity (SSD) of coarse and fine aggregates is 2.70 and 2.63, respectively. The absorption capacity of coarse and fine aggregates is 0.8 and 1.1%, respectively. Coarse aggregate was separated into two different size fractions as 4/8 mm (CAI) and 8/16 mm (CAII) and then recombined to a specified uniform grading during mixing. The blend consisted of 50% CAI, 23% CAII and 27% natural sand (NS). The blend conforms to ASTM C33 aggregate grading standard. A melamine sulfonate polymer type (brown, density of 1.2 kg/l) high range water reducing admixture (HRWRA), was used in all mixtures in constant value accept for first mixture within the limits proposed by the manufacturer. 2.2. Preparation and casting of specimens The proportioning and description of the concrete mixtures are summarized in Table 2. Six series of high strength concrete mixtures were designed to have a slump of 50 ± 15 mm. Mixture M1 is a normal HSC. M2 and M3 were prepared for 30% SF and 25% FA replacement of cement, respectively. M4–M6 mixtures consist of 30% SF replacement of cement and 5, 10 and 15% FA, respectively, replacement with aggregate.

In the study, six batches were prepared for each concrete mixture. From each batch three specimens were prepared in order to use same batch at following three tests. The compressive and splitting tensile strength tests were performed on 100/200 mm cylinders at 28 days according to ASTM C39 and ASTM C496, respectively. Cube samples of 71 ± 1.5 mm were used for the determination of wear resistance at 28 days according to Turkish standard specifications TS 699-1987. Although this standard is highly recommended for the abrasion of natural stones, this standard is applied on concrete specimens as an alternative of ASTM C779. Many other researchers used this method and obtained reliable results [5,6]. In compliance with TS 699, the abrasion system had a steel disc, which had a diameter of 750 mm and rotating speed of 30 ± 1 cycle/min, a counter and a lever, which could apply 300 ± 3 N on the specimens. Abrasion test apparatus is shown in Fig. 1. In the test procedure, 20 ± 0.5 g of abrasion dust was spread on the disc, the specimens were then placed, the load was applied to the specimen and the disc was rotated for four periods, while a period was equal to 22 cycles. After that, the surfaces of the disc and the sample were cleaned. The above-mentioned procedure repeated for 20 periods (totally 440 cycles) by rotating the sample 90◦ in each period. The volume decrease was measured in cm3 /cm2 due to wear. Abrasive dust used in this test was corundum (crystalline Al2 O3 ).

Table 2 Mix proportions and description of concrete mixtures Mixture code

Batch weight (kg/m3 ) PC

SF

FA

Water

CAI

CAII

NS

HRWRA

M1 M2 M3 M4 M5 M6

550 385 413 385 385 385

0 165 0 165 165 165

0 0 137 28 55 83

123 135 130 153 175 194

905 860 867 821 776 732

416 396 399 377 357 337

477 454 457 433 409 386

13.75 16.50 16.50 16.50 16.50 16.50

Aggregates were used in saturated-surface dry (SSD) condition in the concrete mixtures.

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Table 3 Statistical parameters of test results for each concrete mixture Loss on wear (cm3 /50 cm2 )

Mixture code

Statistical values

Compressive strength (MPa)

Splitting tensile strength (MPa)

M1

Average (MPa) S.D.

75.5 1.2

5.3 0.36

8.14 1.26

M2

Average (MPa) S.D.

82.7 2

6.8 0.43

7.01 1.40

M3

Average (MPa) S.D.

68.4 3

5.6 0.51

10.28 1.55

M4

Average (MPa) S.D.

76.8 2.4

5.7 0.25

7.73 1.46

M5

Average (MPa) S.D.

75.2 2.2

5.1 0.66

8.07 1.28

M6

Average (MPa) S.D.

73.8 2

5.9 0.48

8.26 1.57

S.D.: standard deviation. Each value is the average of six specimens.

3. Results and discussion The average results of compressive strength, splitting tensile strength and wear loss values as well as the coefficient of variation for each concrete mixture are summarized in Table 3. Reported values are the average of six specimens. The mean compressive strength values ranged from 68.4 to 82.7 MPa. The 28-day maximum compressive strength, 82.7 MPa was obtained in M2 mixture where 30% of cement was replaced with SF. It is recognized that SF can contribute significantly to the compressive strength development. This is because of the pore refining effect and excellent pozzolanic properties of the material, which causes a stronger zone at the paste-aggregate interface [7–9]. The minimum 28-day compressive strength, 68.4 MPa, was found for the 25% FA replacement concrete (M3), which is typical behavior of FA concrete at 28 days. The use of 25% FA as replacement for cement can decrease the 28-day compressive strength of the concrete. It is known that fly ash generally may has negative effects on the concrete strength, particularly at early ages [10–12]. But after 28 days, the strength of FA concrete increases more rapidly due to the pozzolanic reaction. Compressive strength results indicated that gain in strength of SF–FA mixtures (M4–M6) were in the same trend with the HSC (M1) whereas, the compressive strength of the M4–M6 mixtures is higher than M3 mixture and lower than M2 mixture. Strength reduction of these mixtures (M4–M6) can be attributed entirely consumption of calcium hydroxide by SF and increase in water/(cement + silica fume and/or fly ash) ratio by reason of raise in water requirement due to FA which is replaced with aggregate. Splitting tensile strength values ranged from 5.1 to 6.8 MPa. The maximum splitting tensile strength, 6.8 MPa, was obtained in the mixture M2. The lowest 28-day splitting tensile strength, 5.1 MPa, was found for the M5. It seems that this gain was partly due to pore refining effect of SF. The re-

sults of this test indicated that the splitting tensile strength of the concrete incorporating SF and/or FA varies in the same manner as compressive strength. As shown in Table 3, the lowest (7.01 cm3 /50 cm2 ) and maximum (10.28 cm3 /50 cm2 ) loss of volume on wear was obtained in M2 and M3 mixture, respectively. These test results showed that in general, this property of concrete increases as the strength increases. In addition, the wear resistance of high strength concretes was improved by the use of SF but decreases proportionally with the FA content in the mixtures. Same results were also obtained by other researchers [13,14]. Siddique reported that wear resistance of concrete mixtures containing fly ash was lower than that of control mixture and decreases with increasing fly ash content [13]. Also, Naik et al. determined lower wear resistance values for high-volume fly ash concrete systems relative to no-fly ash concrete [14].

4. Statistical evaluation of test results A multiple regression analysis was applied to obtain the following relationship among compressive strength, splitting tensile strength and loss on wear value: LOW = 29.38 − 0.31fc + 0.39fst

(1)

where LOW is the 28-day wear loss value of concrete (cm3 /50 cm2 ); fc the 28-day compressive strength of concrete (MPa); and fst is the 28-day splitting tensile strength of concrete (MPa). The measured and estimated losses on wear values are given in Table 4. The comparison of experimental and estimated loss on wear values (obtained from Eq. (1)) as well as 95% confidence interval is shown in Fig. 2. The estimated values are in a good agreement with the experimental values obtained in this study. The coefficient of correlation between estimated and experimental values is 83%. In the other words, the

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differences between calculated and experimentally obtained values are within the range of ±1.90

Table 4 Measured and estimated wear loss values Mixture code

Batch no.

28-Day loss on wear values (cm3 /50 cm2 ) Estimated

M1

Measured

1 2 3 4 5 6

7.52 7.59 8.44 7.88 8.86 7.99

6.84 8.10 9.81 8.21 9.23 6.63

M2

1 2 3 4 5 6

6.57 6.47 7.46 6.92 5.64 5.33

7.21 5.72 9.36 7.63 5.62 6.54

M3

1 2 3 4 5 6

9.36 10.37 10.82 9.43 11.26 10.94

8.49 11.32 9.36 8.86 11.96 11.70

M4

1 2 3 4 5 6

8.16 9.28 7.57 7.47 7.56 6.79

8.24 9.96 8.43 7.21 6.69 5.85

M5

1 2 3 4 5 6

7.40 8.11 7.24 8.16 8.37 9.12

6.95 8.22 7.65 6.69 8.76 10.16

M6

1 2 3 4 5 6

8.64 8.66 8.51 9.51 9.42 8.15

6.92 8.25 7.46 9.95 10.35 6.63

Fig. 2. Comparison of experimental and calculated loss on wear values.

5. Conclusions • Wear damage of high strength concrete can be estimated from compressive and splitting tensile strength results. The proposed equation has a sufficient reliability. • The 30% SF replacement of cement provided improvement in the mechanical properties and wear resistance of the concrete while the presence of 25% FA, as a partial replacement of cement, caused significant reduction. • High strength concrete mixtures (M4–M6) consist of 5, 10 and 15% FA, respectively, as an aggregate replacement, generally exhibited same mechanical properties and wear resistance with mixture M1.

References [1] S. Mindess, J.F. Young, Concrete, Prentice-Hall International, USA, 1985. [2] T.R. Naik, S.S. Singh, B.W. Ramme, Effect of source of fly ash abrasion resistance of concrete, J. Mater. Civil Eng. (2002) 417–426. [3] M.J. Shannag, High strength concrete containing natural pozzolan and silica fume, Cement Concrete Comp. 22 (2000) 399–406. [4] M.N. Hague, O. Kayalı, Properties of high-strength concrete using a fine fly ash, Cement Concrete Res. 28 (1998) 1445–1452. [5] M. Arslan, The effects of permeable formworks with sucker liners on the physical properties of concrete surfaces, Constr. Build Mater. 15 (2001) 149–156. [6] S. Oymael, M.A. Ye˘ginobalı, The effect of bituminous schist on abrasion resistance of concrete, in: Proceedings of the Fourth National Concrete Conference on Mineral and Chemical Admixtures in Concrete Technology, Istanbul, 1996, pp. 359–367. [7] K.H. Khayat, P.C. A¨ıtcin, Silica fume in concrete, in: Proceedings of the Fourth International Conference on the Use of Fly Ash, Silica Fume, Slag and Other Minerals By-products in Concrete, ACI SP132, Istanbul, Turkey, 1992, pp. 835–872. [8] ACI Committee 226, Silica fume concrete, ACI Mater. J. 84 (2) (1987) 158–166. [9] V.M. Malhotra, G.G. Carette, V. Sivasundaram, Role of silica fume in concrete: a review, Division Report No. MSL 91-98, CANMET, Energy, Mines and Resources Canada, 1992, p. 73. [10] ACI Committee 226, Use of Fly ash in concrete, ACI Mater. J. (1987) 381–409. [11] G.G. Carette, V.M. Malhotra, Early-age strength development of concrete incorporating fly ash and condensed silica fume, in: Proceedings of the First International Conference on the Use of Fly Ash, Silica Fume, Slag and Other Minerals By-products in Concrete, ACI SP-79, Detroit, 1983, pp. 765–784. [12] A. Bilodeau, G.G. Carette, V.M. Malhotra, Mechanical Properties of Non-air-entrained, High Strength Concrete Incorporating Supplementary Cementing Materials, Division Report No. MSL 89-129, CANMET, Energy, Mines and Resources, Canada, 1989, p. 30. [13] R. Siddique, Performance characteristics of high-volume class fly ash concrete, Cement Concrete Res. 34 (2004) 487–493. [14] T.R. Naik, S.S. Singh, M.M. Hossain, Abrasion resistance of concrete as influenced by inclusion of fly ash, Cement Concrete Res. 24 (1994) 303–312.