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Properties of pervious concrete made with electric arc furnace slag and alkali-activated slag cement
Construction and Building Materials 109 (2016) 34–40
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Properties of pervious concrete made with electric arc furnace slag and alkali-activated slag cement J.J. Chang, W. Yeih ⇑, T.J. Chung, R. Huang Department of Harbor and River Engineering, National Taiwan Ocean University, Keelung 20201, Taiwan
h i g h l i g h t s The 28-d compressive strength of pervious concrete made with EAFS and AASC is 35 MPa. Pervious concrete made with AASC has a lower BPN than that made with OPC. Pervious concrete made with AASC has low-frequency absorption for 125–250 Hz.
a r t i c l e
i n f o
Article history: Received 9 September 2015 Received in revised form 17 December 2015 Accepted 28 January 2016
Keywords: Electric arc furnace slag Alkali-activated slag cement Pervious concrete British pendulum number Sound absorption ratio
a b s t r a c t In this paper, the properties of pervious concrete made with electric arc furnace slag (EAFS) and alkaliactivated slag cement (AASC) were investigated. It was found that the mechanical strengths of pervious concrete made with AASC were higher than those of pervious concrete made with Portland cement. The 28-day compressive strength for pervious concrete made with EAFS and AASC exceeded 35 MPa while its permeability was higher than 0.49 cm/s. The British pendulum number (BPN) for the pervious concrete made with AASC was lower than that made with Portland cement, which implied the pervious concrete made with AASC had a better anti-skid performance. In addition, the sound absorption ratio for the pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm) could reach 0.94 for low frequency noise (125 Hz). Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Pervious concrete is an environmentally friendly material in many aspects. Due to its superior permeability, pervious concrete is considered as a good alternative in flood control [1]. Pervious concrete is also beneficial in reducing the ‘heat-island effect’, which makes the temperature of urban area higher than that of suburban area [2]. In addition, pervious concrete can provide a better anti-skid performance in rainy days and better sound absorption capability [3]. Park et al. [4] studied the sound absorption properties of pervious concrete using recycled aggregate and various target void ratios. They reported the sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the Noise Reduction Coefficient (NRC) was optimum at the void ratio of 25% but the percent content of the recycled aggregate had very little influence on the NRC. Therefore, they concluded that the optimum void ratio is 25% and the recycled aggregate is 50%. ⇑ Corresponding author. E-mail address: [email protected] (W. Yeih). http://dx.doi.org/10.1016/j.conbuildmat.2016.01.049 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
Park et al. [5] studied water purification capability of pervious concrete. A porous concrete with a smaller size of aggregate and a higher void content was found to have superior ability of the removal of the total phosphorus and total nitrogen in the test water. They concluded this effect is due to the large specific surface area of the porous concrete. For studying the mixture design of pervious concrete and the effects of aggregate size on mechanical behaviors, the following references may be helpful. Fu et al. [6] studied the influence of aggregate size and binder material on the properties of pervious concrete. Fu et al. [7] used the Taguchi method to study the design of pervious concrete. Crouch et al. [8] studied the aggregate effects on the static elastic modulus of pervious concrete. They reported an increased aggregate amount resulted in a statistically significant decrease in both compressive strength and static elastic moduli. The following researches adopted waste to make pervious concrete. Gesog˘lu et al. [9] studied the effect of adding three types of rubber to replace aggregates for pervious concrete. They found that the use of rubber significantly aggravated the pervious concrete mechanical properties and its permeability in different degrees according to the rate and type of rubber used. However, replace-
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
ment of natural aggregate with rubber particles resulted in a significant increase of toughness and ductility of concrete as well as better damping capacity. Gesog˘lu et al. [10] further investigated the effects of particle size and volume content of waste tire rubber on the flexural strength, abrasion and freezing thawing resistances of pervious concretes. Kuo et al. [11] used washed municipal solid waste incinerator bottom ash as a substitute for natural aggregate in pervious concrete. They reported that the split tensile and bending strengths were approximately 1/9 and 1/4 of the compressive strength, respectively. Cheng et al. [12] used recycled aggregate to make pervious concrete, and they reported that among their trials the optimal mixture was described as the followings: w/ b = 0.35, nominal diameter for the recycled aggregate is 11.1 mm; the volume fraction for the binder is 0.5; and aggregate to cement ratio is 3.9. To extend the use of pervious concrete, how to promote the compressive strength becomes an important issue. Fujiwara et al. [13] reported that a high strength pervious concrete could be made by coating the coarse aggregates with a high-strength mortar, then applying vibration to fuse them. Huang et al. [14] reported the properties of polymer-modified pervious concrete. They concluded that it was possible to obtain pervious concrete mixture with acceptable permeability and strength through the combination of latex and sand. Chindaprasirt et al. [15] reported that good porous concretes with void ratio of 15–25% and strength of 22–39 MPa were produced using paste with flow of 150–230 mm and top surface vibration of 10 s with vibrating energy of 90 kN m/m2. Chindaprasirt et al. [16] also investigated the effects of aggregate size and cement paste strength on the compressive strength and void ratio of pervious concrete. Generally speaking, pervious concrete does not have a high compressive strength since fruitful connected porosity exists inside it to keep high water permeability. Most pervious concretes have 28-day compressive strength lower than 21 MPa, which is the minimum required compressive strength for structural use. Most applications for pervious concrete are limited to parking lot pavement, pedestrian walkway, bike route and places where concrete compressive strength is not important. It is quite controversial for requiring the high permeability and high compressive strength at the same time. According to [17], three ways to increase the compressive strength of pervious concrete were suggested: (1) Enhancing the characteristics of cement paste by decreasing the water–cement (w/c) ratio and adding pozzolanic materials such as silica fume. (2) Adopting different cementitious materials such as epoxy. (3) Applying slight pressure and increasing the temperature during the curing stage. Recently, Yeih et al. [18] provided an alternative to improve the compressive strength of pervious concrete. They reported that cement paste could penetrate into the air-cooling electric arc furnace slag (EAFS) and formed a strong interlocking effect. Consequently, a pervious concrete with higher compressive strength but greater water permeability could be made. Based on this idea, in this article the pervious concrete made with EAFS and alkaliactivated slag cement was investigated. The alkali-activated slag cement concrete was known to have a stronger mechanical property than the ordinary Portland cement (OPC) paste although quick setting and a more apparent shrinkage were existing drawbacks. Some recent researches about the alkaliactivated slag concrete were given in [19–24]. Although Yeih et al. [18] developed pervious concrete to meet the requirement of structural concrete (28-day compressive strength exceeds 21 MPa) and pervious concrete (permeability coefficient greater than 0.01 cm/s), pervious concrete with a higher
compressive strength is required to be developed due to two reasons. First, the pervious concrete developed in [18] had a maximum compressive strength of 28 MPa only. Considering the possible degradation due to the differences between laboratory and in-situ conditions, pervious concrete with a higher compressive strength is still a goal for engineers. In addition to that, although for concrete with 28-day compressive strength exceeding 21 MPa can be used for pavement engineering a high traffic volume pavement or airport runway might require a higher 28-day compressive strength such as 35 MPa. According to these requirements, it is our goal to develop a pervious concrete system to have 28-day compressive strength exceeding 35 MPa and permeability coefficient higher than 0.01 cm/s at the same time. Based on this motivation, pervious concrete made with EAFS and AASC will be proposed here. 2. Experimental 2.1. Materials Type I Portland cement was used. Another cement paste adopted the blast furnace slag with the following properties: (specific area of 405 m2/kg, specific weight of 2.67. 7-day activity index of 76.6%, 28-day activity index of 103.3% and its major chemical components: 38.38% SiO2; 17.46% Al2O3; 2.08% Fe2O3; 33.71% CaO; 5.52 MgO and 0.40% SO3). The alkali-activator was prepared by mixing the sodium silicate and sodium hydroxide according to our previous research [25], and phosphoric acid was added to play as the retarder to inhibit quick setting. The details of the alkali-activator are stated in the follows: SiO2 = 100 g/L; Na2O = 100 g/L; H3PO4 = 0.74 M. Two aggregates, gravel and air-cooling EAFS, for the same size (0.24–0.48 cm) were prepared as the coarse aggregates. In [18], they reported aggregates with a greater size reduced the compressive strength of pervious concrete. Therefore, the smaller size of aggregates in [18] was considered. The properties of aggregates are given in Table 1. The chemical compositions of EAFS are tabulated in Table 2. 2.2. Mixture design The idea of making the pervious concrete is first described in the follows. First, one can pack aggregates into a unit volume and check the initial porosity after packing. The values of initial porosities using different aggregates are shown in Table 1. These values represent the initial volume of voids after packing aggregates. Theoretically, this volume of voids then should be fully filled by the binding material for the conventional concrete design. However, for pervious concrete this volume is only partially filled by cement paste such that a significant amount of void volume exists to allow water penetration. In this study, different filled percentages of voids by binder (denoted as V) were selected as variables. Two different binders, the OPC and AASC, were adopted for this research. In order to have an easy comparison, for the OPC the water/cement (denoted as w/c) ratio of 0.35 was selected while for the AASC the Liquid/Slag (denoted as L/Sg or L/S) ratio of 0.35 was used. Therefore, the variables considered here include the aggregate types and the filled percentages of voids by binder. Mix designs and the variables considered are tabulated in Table 3. 2.3. Specimen preparation The pervious concrete specimens were made according to mixture designs in Table 3. Cylindrical specimens (diameter of 10-cm and height of 20-cm) were made for unit weight test, connected porosity test, water permeability coefficient and compressive strength. For the British pendulum test, concrete blocks with size of (5 cm 10 cm 2.5 cm) were made. For the sound absorption coefficient test, cylindrical specimens were made and the specimen sizes were determined according to the specification, which will be given in the next subsection. For each individual test for pervious concrete of a specific mixture, five specimens were made. Therefore, every data point represents the average value of five specimens. After Table 1 Physical properties of aggregates. Aggregate types
EAFS
Gravel
Label Maximum aggregate size Range of aggregate size Specific weight Initial porosity (％) Water absorption (％)
A 0.48 cm 0.48–0.24 cm 3.44 40.75 3
B 0.48 cm 0.48–0. 24 cm 2.69 37.5 –
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40 (5) British pendulum test (ASTM E303-93 [30]): the British pendulum test was used to understand the anti-skid performance of the pervious concrete. The results are illustrated by the British pendulum number (BPN) where a higher BPN indicates a better anti-skid performance, i.e., the friction force provided by the concrete surface is greater. (6) Sound absorption coefficient (ASTM E1050 [31]).
Table 2 Chemical compositions of EAFS. Chemical composition
Range (%)
Average (%)
SiO2 Al2O3 CaO MgO SO3 S FeO Others
14.91–42.2 1.78–12.27 5.55–39.58 1.89–17.63 0.01–0.08 0.003–0.222 0.92–48.28
21.38 6.09 23.4 8.32 0.03 0.07 18.87 21.84
3. Results and discussion 3.1. Unit weight Fig. 1 depicts the results of unit weights. As the filled percentage of voids by binder (V) increased, the unit weight increased as well. For the same aggregate, the pervious concrete made with the OPC had a heavier unit weight than that made with the AASC. The reason may be explained by the specific weight of Portland cement (about 3.15) and the specific weight of the blast furnace slag (2.67). Therefore, for the same volumetric amount of cement paste the OPC paste was heavier than the AASC. The aggregate types also influenced the unit weight. When other conditions are the same, the pervious concrete made with the gravel was lighter than that made with EAFS. This reason comes from the fact the specific weight of EAFS was 3.44, which was larger than the specific weight of gravel (2.67).
casting, specimens were demolded in 1 day. The specimens then were embedded in saturated lime water for 27-d curing. As the age of specimens reached 28 days, the specimens then were removed from the curing pool and all experiments were conducted afterwards which meant the age of pervious concrete was 28 days. 2.4. Experiments conducted The experiments conducted included: (1) Unit weight: (ASTM C138 [26]). (2) Connected Porosity [27]: the total porosity in pervious concrete includes disconnected porosity and connected porosity, and the connected porosity is the primary influencer of water permeability. The specimen volume V1 was first measured; then it was immersed in water until it was filled with water. The weight in water W1 was then measured. Subsequently, the specimen was taken out of water and dried. When its weight became stable, then its weight in air W2 was measured. The equation for connected porosity P1 is expressed as follows:
P1 ¼ ½1 ðW 2 W 1 Þ=V 1 100%
3.2. Connected porosity Fig. 2 depicts the relationship between the connected porosity and the filled percentage of voids by binder. Comparing the influence of aggregate type, it can be found that the connected porosity for pervious concrete made with EAFS was higher than that made with gravel. This reason comes from the fact that the initial packing porosity for EAFS was higher than gravel due to the porous nature of EAFS. Therefore, under the same filled percentage of voids by binder the pervious concrete made with EAFS would have a higher connected porosity than that made with gravel. In addition, using the same aggregate the pervious concrete made with OPC had a lower connected porosity than that made with AASC under the same filled percentage of voids by binder. It is known that the contraction of AASC is much apparent than OPC [32], consequently, as the same filled percentage is used the more serious contraction of AASC results in a larger volume of connected porosity. Also, when the filled percentage of voids by binder increased the connected porosity decreased. It is natural since when the filled percentage of voids increased more voids were filled by binder and consequently the connected porosity decreased.
ð1Þ
The porosity in Eq. (1) represents the connected porosity, which is directly related to the permeability. The above mentioned method can be found in [27]. (3) Water permeability coefficient [28]: the water permeability coefficient was calculated using the constant-head permeability test, which is based on the Pavement Test Manual established by the Japan Road Association. The permeability instrument measured the permeability coefficient of U10 * 20 cm cylindrical specimens. The equation for water permeability coefficient K is expressed as follows:
K¼
QL AHDt
ð2Þ
where K = water permeability coefficient (cm/s) Q = flow volume (mL) L = specimen thickness (cm) A = the pervious surface area of specimens (cm2) H = water head height (cm) Dt = t1 t0 represents time duration of measurement (s) (4) Compressive strength [29]: the 28-day compressive strength was determined based on the ASTM C39 for cylindrical concrete specimens.
Table 3 Mix designs (w/c = 0.35 or L/Sg = 0.35). Aggregate label
Filled percentage of voids by cement paste (%), V
Coarse aggregate (kg/m3)
Cement (kg/m3)
Water (kg/m3)
Blast furnace slag (kg/m3)
Alkali-activator (kg/m3)
A
70 80 90 100
1688 1688 1688 1688
455 520 585 651
159 182 205 228
0 0 0 0
0 0 0 0
B
70 80 90 100
1621 1621 1621 1621
349 399 449 499
122 140 160 175
0 0 0 0
0 0 0 0
A
70 80 90 100
1688 1688 1688 1688
0 0 0 0
0 0 0 0
431 494 557 619
151 173 195 217
B
70 80 90 100
1621 1621 1621 1621
0 0 0 0
0 0 0 0
332 380 431 474
116 133 151 166
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40 0.8
2400
Water Permeability Coefficient (cm/sec)
Unit weight AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
Unit weight (kg/m 3)
2200
2000
1800
1600
0.6
0.4
K AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
0.2
0 60
70
80
90
100
Filled percentage of voids by binder (%)
1400 60
70
80
90
100
Fig. 3. Water permeability coefficients for pervious concretes.
Filled percentage of voids by binder (%) Fig. 1. The unit weights for pervious concretes.
In addition, for the filled percentage of voids by binder reached 100% the water permeability coefficient of concrete cannot be measured in this test due to the measuring duration of this test only lasts lower than 10 min. The permeability coefficient for the filled percentage of voids by binder of 100% is very small (for example 1 106 cm/s), it approached to zero if we use the scale in Fig. 3. This is the reason why in Fig. 3 for the filled percentage of voids by binder reached 100% we assigned water permeability coefficient was 0 cm/s. Actually, data for the filled percentage of voids by binder reached 100% were not ‘available’ as explained earlier.
25
15
10
3.4. Compressive strength Connected Porosity AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
5
0 60
70
80
90
100
Filled percentage of voids by binder (%) Fig. 2. The connected porosity for pervious concretes.
3.3. Water permeability coefficient Water permeability coefficient is the most important index to check the performance of pervious concrete. According to the requirement of Japan Road Association, concrete with its water permeability coefficient greater than 0.01 cm/s can be categorized into pervious concrete. Fig. 3 depicts the relationship between the water permeability coefficient and the filled percentage of voids by binder. It can be found that pervious concrete made with EAFS had higher water permeability coefficient than that made with gravel. This trend matched the results for connected porosity, and the higher initial porosity using EAFS was the major factor. Similarly, one also can observe that the pervious concrete made with OPC had a lower water permeability coefficient than that made with AASC provided the same filled percentage of voids by binder was adopted. The more serious contraction of AASC was the reason for this phenomenon as we already explain in the previous subsection. Also, when the filled percentage of voids by binder increased the water permeability decreased. It is natural since when the filled percentage of voids increased more voids were filled by binder and consequently the water permeability decreased.
Compressive strength is the most important index in evaluating the mechanical properties of concrete. Usually, the 28-d compressive strength for structural concrete needs to exceed 21 MPa (or 3000 psi). For pavement with high travel flow such as the highway pavement or runway pavement in airport, the 28-d compressive strength needs to exceed 35 MPa (or 5000 psi). Fig. 4 depicts relationship between the 28-day compressive strength and the filled percentage of voids by binder. It can be found that pervious concrete made with EAFS had higher compressive strength than that made with gravel. Remember that in the previous subsection, the pervious concrete made with EAFS had higher water permeability than that made with gravel. This result indicates that the pervious 50 Compressive strength
Compressive Strength (MPa)
Connected Porosity (%)
20
AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
40
30
20
10
0 60
70
80
90
Filled percentage of voids by binder (%) Fig. 4. Compressive strengths for pervious concretes.
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
3.5. British pendulum test British pendulum number (BPN) is taken as the index of antiskid performance of pervious concrete. A lower BPN means a less friction force can be provided, and a worse anti-skid performance is expected. In [18], the minimum required BPN for various conditions can be found. Fig. 5 depicts the BPNs for various pervious concretes. Several trends can be found in this figure following this guideline. First,
100
BPN
90
80 BPN AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
70
60 60
70
80
90
100
Filled percentage of voids by binder (%) Fig. 5. British pendulum numbers for pervious concretes.
as the filled percentage of voids by binder increased the BPN decreased. In [18], the reason for this phenomenon was given. As the filled percentage of voids by binder increased, more paste was used and consequently a smoother surface was formed. Second, the pervious concrete made with EAFS had a higher BPN than that made with gravel. This phenomenon can be explained by the rougher surface of EAFS than the gravel. In addition, the pervious concrete made with AASC had a smaller BPN than that made with
0.5
Sound-absorption coefficient
concrete made with EAFS had greater volume of voids, and it is then expected the compressive strength of pervious concrete made with EAFS will be lower. However, the results conflicts our expectation. One may guess the EAFS may have a stronger nature than gravel. In our previous research [18], the crushing value of EAFS was 0.311 while the crushing value of the natural aggregate was 0.289. This result implied that the mechanical property of EAFS was worse than the natural aggregate. Then, why the observation violates our expectation. In [18], the evidence was provided to explain this phenomenon. The porous nature of EAFS allowed penetration of cement paste, and it resulted in a strong interlocking effect and consequently increased the compressive strength. Our results can be explained by the same reason provided in [18]. It is worth to make a notice here: the above statement is true only when the two types of aggregates do not have great difference in mechanical properties. In our study, the crushing values of EAFS and gravel were different but they did not have a huge difference. It meant these two aggregates had similar mechanical performance. If the mechanical properties of two aggregates deviate a lot, the interlocking effect is meaningless since its contribution does not overcome the effect of deviation in mechanical strength of two aggregates. It means that we should not use a porous aggregate with poor mechanical strength then expect it can be used to develop a high strength pervious concrete. For the common concrete, its compressive strength depends on the quality of aggregates, the grading of aggregates, and mostly the binder quality. Usually, the concrete can be viewed as the composite containing two phases: coarse aggregates and mortar. The compressive strength of coarse aggregate is usually higher than mortar. Therefore, the quality of mortar decides the quality of concrete. For pervious concrete, it contains more voids than the common concrete due to different design concept. It is known that the mechanical quality of pervious concrete mainly depends on the point-wise connection between aggregates due to the fact in pervious concrete we do not fill space between aggregates fully with paste. The contact of gravels has a smoother surface, and binder can bind aggregates simply by its binding characteristics (binding capability between binder and aggregate). For EAFS, first the contact surface between aggregates was rougher than that between gravels which contributes a little enhancement in mechanical strength. Mainly the porous nature of EAFS allows paste to penetrate into aggregates and form a very strong interlocking force between aggregates, which can be thought as the hardened paste forms anchors inside aggregates consequently these anchors enhance the connection between aggregates. In addition, the compressive strength increased as the filled percentage of voids by binder increased which is an obvious result. When the same aggregate is adopted, the compressive strength for pervious concrete made with OPC was lower than that made with AASC. The paste of AASC is known to have a stronger compressive strength than that of OPC [33], therefore this result is natural. It is worthy to mention here that the pervious concrete made with AASC as binder material, EAFS as coarse aggregate, and filled percentage of voids by binder of 90% could have a 28-day compressive strength of 35 MPa and water permeability coefficient of 0.49 cm/s.
W/C=0.35 Agg. A V=70% W/C=0.35 Agg. A V=80% W/C=0.35 Agg. A V=90% W/C=0.35 Agg. A V=100%
(a)
0.4
0.3
0.2
0.1
0 125
250
375
500
625
750
875 1000 1125 1250
Hz 0.4
Sound-absorption coefficient
38
W/C=0.35 Agg. B V=70% W/C=0.35 Agg. B V=80% W/C=0.35 Agg. B V=90% W/C=0.35 Agg. B V=100%
(b)
0.3
0.2
0.1
0 125
250
375
500
625
750
875 1000 1125 1250
Hz Fig. 6. Sound absorption coefficients for pervious concretes made with OPC: (a) using EAFS as aggregate; (b) using gravel as aggregate.
J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
OPC. It is known the cohesion of AASC is stronger than OPC [32], consequently it results in a tighter and smoother surface for AASC. Basically, the pervious concrete made with AASC as binder material, EAFS as coarse aggregate, and filled percentage of voids by binder of 90% can reach a best compressive strength and a satisfactory water permeability had its BPN of 79 which is higher than the required value for all cases referred in [18].
3.6. Sound absorption coefficient The sound absorption coefficients of pervious concretes made with OPC are illustrated in Figs. 6(a) and (b). It can be found that at frequency of 500 Hz, a peak value of sound absorption coefficient appeared for all pervious concrete no matter which aggregate was used. It implied that this peak might reflect the sound absorption characteristic of C–S–H gel. In addition, as the filled percentage of voids by binder increased the sound absorption decreased. Voids inside the pervious concrete contributed to the sound absorption. When the filled percentage of voids by binder increased, the void volume decreased. Consequently, a smaller sound absorption coefficient was obtained. In addition, comparing these two figures one can conclude that pervious concrete made with EAFS had a greater sound absorption coefficient than that made with gravel. From the results of connected porosity, it is known that pervious concrete made with EAFS had a larger void volume than that made with gravel. It then be natural that pervious concrete made with EAFS had a larger sound absorption coefficient.
Sound-absorption coefficient
1
(a)
L/S=0.35 Agg. A V=70% L/S=0.35 Agg. A V=80% L/S=0.35 Agg. A V=90% L/S=0.35 Agg. A V=100%
0.8
39
The sound absorption coefficients for pervious concretes made with AASC are illustrated in Figs. 7(a) and (b). In these figures, the results for pervious concretes made with AASC showed scattered data and no apparent trend can be found. However, for most cases the absorption peak at 500 Hz still existed. It is known that the chemical resultant for AASC contains C–S–H and analogous zeolite structure. According to this, the peak at 500 Hz then is natural since AASC also contains C–S–H. In addition to this, some cases had a peak value at 125–250 Hz which might come from the analogous zeolite structure. This result implied that the pervious concrete made with AASC had a better sound absorption characteristic than that made with OPC. Now, let us examine the performance of pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm). The sound absorption coefficient for it at 125 Hz was 0.94, it meant this pervious concrete could have good sound absorption at low frequency. 4. Conclusions In this article, the performances of pervious concretes made with EAFS and AASC were investigated. The optimum mixture found in this research was the pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm). The 28-day compressive strength of it was 35 MPa, the water permeability coefficient was 0.49 cm/s, the BPN was 79 and the sound absorption coefficient at 125 Hz was 0.94. A pervious concrete with high compressive strength could be achieved by using EAFS and AASC. The porous nature of EAFS provided a strong interlocking effect and the AASC was a stronger binding material than OPC. Consequently, a high strength pervious concrete is possible and it can be applied to many engineering applications where the water permeability and strength was required at the same time.
0.6
Acknowledgment 0.4
The authors want to express their thanks for the financial support from the National Science Council, Taiwan under the Grant number NSC 100-2221-E-019-055.
0.2
References 0 125
250
375
500
625
750
875 1000 1125 1250
Hz
Sound-absorption coefficient
1
(b)
L/S=0.35 Agg. B V=70% L/S=0.35 Agg. B V=80% L/S=0.35 Agg. B V=90% L/S=0.35 Agg. B V=100%
0.8
0.6
0.4
0.2
0 125
250
375
500
625
750
875 1000 1125 1250
Hz Fig. 7. Sound absorption coefficients for pervious concretes made with AASC: (a) using EAFS as aggregate; (b) using gravel as aggregate.
[1] AJ. Schokker, The Sustainable Concrete Guide – Strategies and Examples, U.S. Green Concrete Council, 2010. [2] J.S. Golden, K.E. Kaloush, Mesoscale and microscale evaluation of surface impacts on the urban heat island effects, Int. J. Pavement Eng. 7 (1) (2006) 37– 52. [3] A. Marolf, N. Neithalath, E. Sell, K. Wegner, J. Weiss, J. Olek, Influence of aggregate size and gradation on acoustic absorption of enhanced porosity concrete, ACI Mater. J. 101 (1) (2004) 82–91. [4] S.B. Park, D.S. Seo, J. Lee, Studies on the sound absorption characteristics of porous concrete based on the content of recycled aggregate and target void ratio, Cem. Concr. Res. 35 (9) (2005) 1846–1854. [5] S.B. Park, M. Tia, An experimental study on the water-purification properties of porous concrete, Cem. Concr. Res. 34 (2) (2004) 177–184. [6] T.C. Fu, W. Yeih, J.J. Chang, R. Huang, The influence of aggregate size and binder material on the properties of pervious concrete, Adv. Mater. Sci. Eng. (2014) (Article ID 963971, 17 pages). [7] T.C. Fu, R. Huang, W. Yeih, J.J. Chang, P.C. Lee, Study of the pervious concrete properties using the experimental design method, Adv. Mater. Res. 1089 (2015) 253–264. [8] L.K. Crouch, J. Pitt, R. Hewitt, Aggregate effects on pervious Portland cement concrete static modulus of elasticity, J. Mater. Civ. Eng. 19 (7) (2007) 561–568. _ Investigating properties of [9] M. Gesog˘lu, E. Güneyisi, G. Khoshnaw, S. Ipek, pervious concrete containing waste tire rubbers, Constr. Build. Mater. 63 (2014) 206–213. _ Abrasion and freezing–thawing [10] M. Gesog˘lu, E. Güneyisi, G. Khoshnaw, S. Ipek, resistance of pervious concrete containing waste rubber, Constr. Build. Mater. 73 (2014) 19–24. [11] W.-T. Kuo, C.-C. Liu, D.-S. Su, Use of washed municipal solid waste incinerator bottom ash in pervious concrete, Cem. Concr. Compos. 37 (2013) 328–335.
40
J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
[12] A. Cheng, H.-M. Hsu, S.-J. Chao, K.-L. Lin, Experimental study on properties of pervious concrete made with recycled aggregate, Int. J. Pavement Res. Technol. 4 (2011) 104–110. [13] H. Fujiwara, R. Tomita, T. Okamoto, A. Dozono, A. Obatake, Properties of highstrength porous concrete, ACI SP-179 (1998) 173–188. [14] B. Huang, H. Wu, X. Shu, E.G. Burdette, Laboratory evaluation of permeability and strength of polymer-modified pervious concrete, Constr. Build. Mater. 24 (5) (2010) 818–823. [15] P. Chindaprasirt, S. Hatanaka, T. Chareerat, N. Mishima, Y. Yuasa, Cement paste characteristics and porous concrete properties, Constr. Build. Mater. 22 (5) (2008) 894–901. [16] P. Chindaprasirt, S. Hatanaka, N. Mishima, Y. Yuasa, T. Chareerat, Effects of cement paste strength and aggregate size on the compressive strength and void ratio of porous concrete, Int. J. Mineral Metall. Mater. 16 (6) (2009) 714– 719. [17] J. Yang, G. Jiang, Experimental study on properties of pervious concrete pavement materials, Cem. Concr. Res. 33 (2003) 381–386. [18] W. Yeih, T.C. Fu, J.J. Chang, R. Huang, Properties of pervious concrete made with air-cooling electric arc furnace slag as aggregates, Constr. Build. Mater. 93 (2015) 737–745. [19] Chao Li, H Sun, L. Li, A review: the comparison between alkali-activated slag (Si +Ca) and metakaolin (Si+Al) cements, Cem. Concr. Res. 40 (9) (2010) 1341– 1349. [20] S.A. Bernal, R.M. Gutiérrez, A.L. Pedraza, J.L. Povis, E.D. Rodrigue, S. Delvasto, Effect of binder content on the performance of alkali-activated slag concretes, Cem. Concr. Res. 41 (1) (2011) 1–8. [21] M. Palacios, H. Manzano, J.S. Dolado, A. Rico, Rodrígues, A model for the C-A-SH gel formed in alkali-activated slag cements, J. Eur. Ceram. Soc. 31 (12) (2011) 2043–2056. [22] J.E. Oh, P.J.M. Monterio, S.S. Jun, S. Choi, S.M. Clark, The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers, Cem. Concr. Res. 40 (2) (2010) 189–196.
[23] Y. Fu, L. Cai, W. Yonggen, Freeze–thaw cycle test and damage mechanics models of alkali-activated slag concrete, Constr. Build. Mater. 25 (7) (2011) 3144–3148. [24] T. Tho-in, V. Sata, P. Chindaprasirt, C. Jaturapitakkul, Pervious high-calcium fly ash geopolymer concrete, Constr. Build. Mater. 30 (2012) 366–371. [25] J.J. Chang, W. Yeih, C.C. Hung, Effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag paste, Cem. Concr. Comput. 27 (1) (2005) 85–91. [26] ASTM C138/C138M-14, Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete, ASTM International, PA, USA, 2014. [27] Japan Concrete Association, Test methods for properties of porous concrete, draft, 1998 (in Japanese). [28] Japan Road Association, Pavement Testing Manual, supplement volume, 317, 1996 (in Japanese). [29] ASTM C39/C39M-14, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, ASTM International, PA, USA, 2014. [30] ASTM E303-93, Standard Test Method for Measuring Surface Frictional Properties using the British Pendulum Tester, ASTM International, PA, USA, 2013. [31] ASTM E1050-12, Standard Test Method For Impedance And Absorption Of Acoustical Materials using a Tube, Two Microphones and Digital Frequency Analysis System, ASTM International, PA, USA, 2012. [32] F. Collins, J.G. Sanjayan, Effect of pore size distribution on drying shrinkage of alkali-activated slag concrete, Cem. Concr. Res. 30 (9) (2000) 1401–1406. [33] S.D. Wang, X.C. Pu, K.L. Scrivener, P.L. Pratt, Alkali-activated slag cement and concrete: a review of properties and problems, Adv. Cem. Res. 7 (27) (1995) 93–102.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Properties of pervious concrete made with electric arc furnace slag and alkali-activated slag cement J.J. Chang, W. Yeih ⇑, T.J. Chung, R. Huang Department of Harbor and River Engineering, National Taiwan Ocean University, Keelung 20201, Taiwan
h i g h l i g h t s The 28-d compressive strength of pervious concrete made with EAFS and AASC is 35 MPa. Pervious concrete made with AASC has a lower BPN than that made with OPC. Pervious concrete made with AASC has low-frequency absorption for 125–250 Hz.
a r t i c l e
i n f o
Article history: Received 9 September 2015 Received in revised form 17 December 2015 Accepted 28 January 2016
Keywords: Electric arc furnace slag Alkali-activated slag cement Pervious concrete British pendulum number Sound absorption ratio
a b s t r a c t In this paper, the properties of pervious concrete made with electric arc furnace slag (EAFS) and alkaliactivated slag cement (AASC) were investigated. It was found that the mechanical strengths of pervious concrete made with AASC were higher than those of pervious concrete made with Portland cement. The 28-day compressive strength for pervious concrete made with EAFS and AASC exceeded 35 MPa while its permeability was higher than 0.49 cm/s. The British pendulum number (BPN) for the pervious concrete made with AASC was lower than that made with Portland cement, which implied the pervious concrete made with AASC had a better anti-skid performance. In addition, the sound absorption ratio for the pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm) could reach 0.94 for low frequency noise (125 Hz). Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Pervious concrete is an environmentally friendly material in many aspects. Due to its superior permeability, pervious concrete is considered as a good alternative in flood control [1]. Pervious concrete is also beneficial in reducing the ‘heat-island effect’, which makes the temperature of urban area higher than that of suburban area [2]. In addition, pervious concrete can provide a better anti-skid performance in rainy days and better sound absorption capability [3]. Park et al. [4] studied the sound absorption properties of pervious concrete using recycled aggregate and various target void ratios. They reported the sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the Noise Reduction Coefficient (NRC) was optimum at the void ratio of 25% but the percent content of the recycled aggregate had very little influence on the NRC. Therefore, they concluded that the optimum void ratio is 25% and the recycled aggregate is 50%. ⇑ Corresponding author. E-mail address: [email protected] (W. Yeih). http://dx.doi.org/10.1016/j.conbuildmat.2016.01.049 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
Park et al. [5] studied water purification capability of pervious concrete. A porous concrete with a smaller size of aggregate and a higher void content was found to have superior ability of the removal of the total phosphorus and total nitrogen in the test water. They concluded this effect is due to the large specific surface area of the porous concrete. For studying the mixture design of pervious concrete and the effects of aggregate size on mechanical behaviors, the following references may be helpful. Fu et al. [6] studied the influence of aggregate size and binder material on the properties of pervious concrete. Fu et al. [7] used the Taguchi method to study the design of pervious concrete. Crouch et al. [8] studied the aggregate effects on the static elastic modulus of pervious concrete. They reported an increased aggregate amount resulted in a statistically significant decrease in both compressive strength and static elastic moduli. The following researches adopted waste to make pervious concrete. Gesog˘lu et al. [9] studied the effect of adding three types of rubber to replace aggregates for pervious concrete. They found that the use of rubber significantly aggravated the pervious concrete mechanical properties and its permeability in different degrees according to the rate and type of rubber used. However, replace-
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
ment of natural aggregate with rubber particles resulted in a significant increase of toughness and ductility of concrete as well as better damping capacity. Gesog˘lu et al. [10] further investigated the effects of particle size and volume content of waste tire rubber on the flexural strength, abrasion and freezing thawing resistances of pervious concretes. Kuo et al. [11] used washed municipal solid waste incinerator bottom ash as a substitute for natural aggregate in pervious concrete. They reported that the split tensile and bending strengths were approximately 1/9 and 1/4 of the compressive strength, respectively. Cheng et al. [12] used recycled aggregate to make pervious concrete, and they reported that among their trials the optimal mixture was described as the followings: w/ b = 0.35, nominal diameter for the recycled aggregate is 11.1 mm; the volume fraction for the binder is 0.5; and aggregate to cement ratio is 3.9. To extend the use of pervious concrete, how to promote the compressive strength becomes an important issue. Fujiwara et al. [13] reported that a high strength pervious concrete could be made by coating the coarse aggregates with a high-strength mortar, then applying vibration to fuse them. Huang et al. [14] reported the properties of polymer-modified pervious concrete. They concluded that it was possible to obtain pervious concrete mixture with acceptable permeability and strength through the combination of latex and sand. Chindaprasirt et al. [15] reported that good porous concretes with void ratio of 15–25% and strength of 22–39 MPa were produced using paste with flow of 150–230 mm and top surface vibration of 10 s with vibrating energy of 90 kN m/m2. Chindaprasirt et al. [16] also investigated the effects of aggregate size and cement paste strength on the compressive strength and void ratio of pervious concrete. Generally speaking, pervious concrete does not have a high compressive strength since fruitful connected porosity exists inside it to keep high water permeability. Most pervious concretes have 28-day compressive strength lower than 21 MPa, which is the minimum required compressive strength for structural use. Most applications for pervious concrete are limited to parking lot pavement, pedestrian walkway, bike route and places where concrete compressive strength is not important. It is quite controversial for requiring the high permeability and high compressive strength at the same time. According to [17], three ways to increase the compressive strength of pervious concrete were suggested: (1) Enhancing the characteristics of cement paste by decreasing the water–cement (w/c) ratio and adding pozzolanic materials such as silica fume. (2) Adopting different cementitious materials such as epoxy. (3) Applying slight pressure and increasing the temperature during the curing stage. Recently, Yeih et al. [18] provided an alternative to improve the compressive strength of pervious concrete. They reported that cement paste could penetrate into the air-cooling electric arc furnace slag (EAFS) and formed a strong interlocking effect. Consequently, a pervious concrete with higher compressive strength but greater water permeability could be made. Based on this idea, in this article the pervious concrete made with EAFS and alkaliactivated slag cement was investigated. The alkali-activated slag cement concrete was known to have a stronger mechanical property than the ordinary Portland cement (OPC) paste although quick setting and a more apparent shrinkage were existing drawbacks. Some recent researches about the alkaliactivated slag concrete were given in [19–24]. Although Yeih et al. [18] developed pervious concrete to meet the requirement of structural concrete (28-day compressive strength exceeds 21 MPa) and pervious concrete (permeability coefficient greater than 0.01 cm/s), pervious concrete with a higher
compressive strength is required to be developed due to two reasons. First, the pervious concrete developed in [18] had a maximum compressive strength of 28 MPa only. Considering the possible degradation due to the differences between laboratory and in-situ conditions, pervious concrete with a higher compressive strength is still a goal for engineers. In addition to that, although for concrete with 28-day compressive strength exceeding 21 MPa can be used for pavement engineering a high traffic volume pavement or airport runway might require a higher 28-day compressive strength such as 35 MPa. According to these requirements, it is our goal to develop a pervious concrete system to have 28-day compressive strength exceeding 35 MPa and permeability coefficient higher than 0.01 cm/s at the same time. Based on this motivation, pervious concrete made with EAFS and AASC will be proposed here. 2. Experimental 2.1. Materials Type I Portland cement was used. Another cement paste adopted the blast furnace slag with the following properties: (specific area of 405 m2/kg, specific weight of 2.67. 7-day activity index of 76.6%, 28-day activity index of 103.3% and its major chemical components: 38.38% SiO2; 17.46% Al2O3; 2.08% Fe2O3; 33.71% CaO; 5.52 MgO and 0.40% SO3). The alkali-activator was prepared by mixing the sodium silicate and sodium hydroxide according to our previous research [25], and phosphoric acid was added to play as the retarder to inhibit quick setting. The details of the alkali-activator are stated in the follows: SiO2 = 100 g/L; Na2O = 100 g/L; H3PO4 = 0.74 M. Two aggregates, gravel and air-cooling EAFS, for the same size (0.24–0.48 cm) were prepared as the coarse aggregates. In [18], they reported aggregates with a greater size reduced the compressive strength of pervious concrete. Therefore, the smaller size of aggregates in [18] was considered. The properties of aggregates are given in Table 1. The chemical compositions of EAFS are tabulated in Table 2. 2.2. Mixture design The idea of making the pervious concrete is first described in the follows. First, one can pack aggregates into a unit volume and check the initial porosity after packing. The values of initial porosities using different aggregates are shown in Table 1. These values represent the initial volume of voids after packing aggregates. Theoretically, this volume of voids then should be fully filled by the binding material for the conventional concrete design. However, for pervious concrete this volume is only partially filled by cement paste such that a significant amount of void volume exists to allow water penetration. In this study, different filled percentages of voids by binder (denoted as V) were selected as variables. Two different binders, the OPC and AASC, were adopted for this research. In order to have an easy comparison, for the OPC the water/cement (denoted as w/c) ratio of 0.35 was selected while for the AASC the Liquid/Slag (denoted as L/Sg or L/S) ratio of 0.35 was used. Therefore, the variables considered here include the aggregate types and the filled percentages of voids by binder. Mix designs and the variables considered are tabulated in Table 3. 2.3. Specimen preparation The pervious concrete specimens were made according to mixture designs in Table 3. Cylindrical specimens (diameter of 10-cm and height of 20-cm) were made for unit weight test, connected porosity test, water permeability coefficient and compressive strength. For the British pendulum test, concrete blocks with size of (5 cm 10 cm 2.5 cm) were made. For the sound absorption coefficient test, cylindrical specimens were made and the specimen sizes were determined according to the specification, which will be given in the next subsection. For each individual test for pervious concrete of a specific mixture, five specimens were made. Therefore, every data point represents the average value of five specimens. After Table 1 Physical properties of aggregates. Aggregate types
EAFS
Gravel
Label Maximum aggregate size Range of aggregate size Specific weight Initial porosity (％) Water absorption (％)
A 0.48 cm 0.48–0.24 cm 3.44 40.75 3
B 0.48 cm 0.48–0. 24 cm 2.69 37.5 –
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40 (5) British pendulum test (ASTM E303-93 [30]): the British pendulum test was used to understand the anti-skid performance of the pervious concrete. The results are illustrated by the British pendulum number (BPN) where a higher BPN indicates a better anti-skid performance, i.e., the friction force provided by the concrete surface is greater. (6) Sound absorption coefficient (ASTM E1050 [31]).
Table 2 Chemical compositions of EAFS. Chemical composition
Range (%)
Average (%)
SiO2 Al2O3 CaO MgO SO3 S FeO Others
14.91–42.2 1.78–12.27 5.55–39.58 1.89–17.63 0.01–0.08 0.003–0.222 0.92–48.28
21.38 6.09 23.4 8.32 0.03 0.07 18.87 21.84
3. Results and discussion 3.1. Unit weight Fig. 1 depicts the results of unit weights. As the filled percentage of voids by binder (V) increased, the unit weight increased as well. For the same aggregate, the pervious concrete made with the OPC had a heavier unit weight than that made with the AASC. The reason may be explained by the specific weight of Portland cement (about 3.15) and the specific weight of the blast furnace slag (2.67). Therefore, for the same volumetric amount of cement paste the OPC paste was heavier than the AASC. The aggregate types also influenced the unit weight. When other conditions are the same, the pervious concrete made with the gravel was lighter than that made with EAFS. This reason comes from the fact the specific weight of EAFS was 3.44, which was larger than the specific weight of gravel (2.67).
casting, specimens were demolded in 1 day. The specimens then were embedded in saturated lime water for 27-d curing. As the age of specimens reached 28 days, the specimens then were removed from the curing pool and all experiments were conducted afterwards which meant the age of pervious concrete was 28 days. 2.4. Experiments conducted The experiments conducted included: (1) Unit weight: (ASTM C138 [26]). (2) Connected Porosity [27]: the total porosity in pervious concrete includes disconnected porosity and connected porosity, and the connected porosity is the primary influencer of water permeability. The specimen volume V1 was first measured; then it was immersed in water until it was filled with water. The weight in water W1 was then measured. Subsequently, the specimen was taken out of water and dried. When its weight became stable, then its weight in air W2 was measured. The equation for connected porosity P1 is expressed as follows:
P1 ¼ ½1 ðW 2 W 1 Þ=V 1 100%
3.2. Connected porosity Fig. 2 depicts the relationship between the connected porosity and the filled percentage of voids by binder. Comparing the influence of aggregate type, it can be found that the connected porosity for pervious concrete made with EAFS was higher than that made with gravel. This reason comes from the fact that the initial packing porosity for EAFS was higher than gravel due to the porous nature of EAFS. Therefore, under the same filled percentage of voids by binder the pervious concrete made with EAFS would have a higher connected porosity than that made with gravel. In addition, using the same aggregate the pervious concrete made with OPC had a lower connected porosity than that made with AASC under the same filled percentage of voids by binder. It is known that the contraction of AASC is much apparent than OPC [32], consequently, as the same filled percentage is used the more serious contraction of AASC results in a larger volume of connected porosity. Also, when the filled percentage of voids by binder increased the connected porosity decreased. It is natural since when the filled percentage of voids increased more voids were filled by binder and consequently the connected porosity decreased.
ð1Þ
The porosity in Eq. (1) represents the connected porosity, which is directly related to the permeability. The above mentioned method can be found in [27]. (3) Water permeability coefficient [28]: the water permeability coefficient was calculated using the constant-head permeability test, which is based on the Pavement Test Manual established by the Japan Road Association. The permeability instrument measured the permeability coefficient of U10 * 20 cm cylindrical specimens. The equation for water permeability coefficient K is expressed as follows:
K¼
QL AHDt
ð2Þ
where K = water permeability coefficient (cm/s) Q = flow volume (mL) L = specimen thickness (cm) A = the pervious surface area of specimens (cm2) H = water head height (cm) Dt = t1 t0 represents time duration of measurement (s) (4) Compressive strength [29]: the 28-day compressive strength was determined based on the ASTM C39 for cylindrical concrete specimens.
Table 3 Mix designs (w/c = 0.35 or L/Sg = 0.35). Aggregate label
Filled percentage of voids by cement paste (%), V
Coarse aggregate (kg/m3)
Cement (kg/m3)
Water (kg/m3)
Blast furnace slag (kg/m3)
Alkali-activator (kg/m3)
A
70 80 90 100
1688 1688 1688 1688
455 520 585 651
159 182 205 228
0 0 0 0
0 0 0 0
B
70 80 90 100
1621 1621 1621 1621
349 399 449 499
122 140 160 175
0 0 0 0
0 0 0 0
A
70 80 90 100
1688 1688 1688 1688
0 0 0 0
0 0 0 0
431 494 557 619
151 173 195 217
B
70 80 90 100
1621 1621 1621 1621
0 0 0 0
0 0 0 0
332 380 431 474
116 133 151 166
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40 0.8
2400
Water Permeability Coefficient (cm/sec)
Unit weight AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
Unit weight (kg/m 3)
2200
2000
1800
1600
0.6
0.4
K AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
0.2
0 60
70
80
90
100
Filled percentage of voids by binder (%)
1400 60
70
80
90
100
Fig. 3. Water permeability coefficients for pervious concretes.
Filled percentage of voids by binder (%) Fig. 1. The unit weights for pervious concretes.
In addition, for the filled percentage of voids by binder reached 100% the water permeability coefficient of concrete cannot be measured in this test due to the measuring duration of this test only lasts lower than 10 min. The permeability coefficient for the filled percentage of voids by binder of 100% is very small (for example 1 106 cm/s), it approached to zero if we use the scale in Fig. 3. This is the reason why in Fig. 3 for the filled percentage of voids by binder reached 100% we assigned water permeability coefficient was 0 cm/s. Actually, data for the filled percentage of voids by binder reached 100% were not ‘available’ as explained earlier.
25
15
10
3.4. Compressive strength Connected Porosity AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
5
0 60
70
80
90
100
Filled percentage of voids by binder (%) Fig. 2. The connected porosity for pervious concretes.
3.3. Water permeability coefficient Water permeability coefficient is the most important index to check the performance of pervious concrete. According to the requirement of Japan Road Association, concrete with its water permeability coefficient greater than 0.01 cm/s can be categorized into pervious concrete. Fig. 3 depicts the relationship between the water permeability coefficient and the filled percentage of voids by binder. It can be found that pervious concrete made with EAFS had higher water permeability coefficient than that made with gravel. This trend matched the results for connected porosity, and the higher initial porosity using EAFS was the major factor. Similarly, one also can observe that the pervious concrete made with OPC had a lower water permeability coefficient than that made with AASC provided the same filled percentage of voids by binder was adopted. The more serious contraction of AASC was the reason for this phenomenon as we already explain in the previous subsection. Also, when the filled percentage of voids by binder increased the water permeability decreased. It is natural since when the filled percentage of voids increased more voids were filled by binder and consequently the water permeability decreased.
Compressive strength is the most important index in evaluating the mechanical properties of concrete. Usually, the 28-d compressive strength for structural concrete needs to exceed 21 MPa (or 3000 psi). For pavement with high travel flow such as the highway pavement or runway pavement in airport, the 28-d compressive strength needs to exceed 35 MPa (or 5000 psi). Fig. 4 depicts relationship between the 28-day compressive strength and the filled percentage of voids by binder. It can be found that pervious concrete made with EAFS had higher compressive strength than that made with gravel. Remember that in the previous subsection, the pervious concrete made with EAFS had higher water permeability than that made with gravel. This result indicates that the pervious 50 Compressive strength
Compressive Strength (MPa)
Connected Porosity (%)
20
AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
40
30
20
10
0 60
70
80
90
Filled percentage of voids by binder (%) Fig. 4. Compressive strengths for pervious concretes.
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
3.5. British pendulum test British pendulum number (BPN) is taken as the index of antiskid performance of pervious concrete. A lower BPN means a less friction force can be provided, and a worse anti-skid performance is expected. In [18], the minimum required BPN for various conditions can be found. Fig. 5 depicts the BPNs for various pervious concretes. Several trends can be found in this figure following this guideline. First,
100
BPN
90
80 BPN AASC (L/Sg=0.35), EAFS AASC (L/Sg=0.35), gravel OPC (w/c=0.35), EAFS OPC (w/c=0.35), gravel
70
60 60
70
80
90
100
Filled percentage of voids by binder (%) Fig. 5. British pendulum numbers for pervious concretes.
as the filled percentage of voids by binder increased the BPN decreased. In [18], the reason for this phenomenon was given. As the filled percentage of voids by binder increased, more paste was used and consequently a smoother surface was formed. Second, the pervious concrete made with EAFS had a higher BPN than that made with gravel. This phenomenon can be explained by the rougher surface of EAFS than the gravel. In addition, the pervious concrete made with AASC had a smaller BPN than that made with
0.5
Sound-absorption coefficient
concrete made with EAFS had greater volume of voids, and it is then expected the compressive strength of pervious concrete made with EAFS will be lower. However, the results conflicts our expectation. One may guess the EAFS may have a stronger nature than gravel. In our previous research [18], the crushing value of EAFS was 0.311 while the crushing value of the natural aggregate was 0.289. This result implied that the mechanical property of EAFS was worse than the natural aggregate. Then, why the observation violates our expectation. In [18], the evidence was provided to explain this phenomenon. The porous nature of EAFS allowed penetration of cement paste, and it resulted in a strong interlocking effect and consequently increased the compressive strength. Our results can be explained by the same reason provided in [18]. It is worth to make a notice here: the above statement is true only when the two types of aggregates do not have great difference in mechanical properties. In our study, the crushing values of EAFS and gravel were different but they did not have a huge difference. It meant these two aggregates had similar mechanical performance. If the mechanical properties of two aggregates deviate a lot, the interlocking effect is meaningless since its contribution does not overcome the effect of deviation in mechanical strength of two aggregates. It means that we should not use a porous aggregate with poor mechanical strength then expect it can be used to develop a high strength pervious concrete. For the common concrete, its compressive strength depends on the quality of aggregates, the grading of aggregates, and mostly the binder quality. Usually, the concrete can be viewed as the composite containing two phases: coarse aggregates and mortar. The compressive strength of coarse aggregate is usually higher than mortar. Therefore, the quality of mortar decides the quality of concrete. For pervious concrete, it contains more voids than the common concrete due to different design concept. It is known that the mechanical quality of pervious concrete mainly depends on the point-wise connection between aggregates due to the fact in pervious concrete we do not fill space between aggregates fully with paste. The contact of gravels has a smoother surface, and binder can bind aggregates simply by its binding characteristics (binding capability between binder and aggregate). For EAFS, first the contact surface between aggregates was rougher than that between gravels which contributes a little enhancement in mechanical strength. Mainly the porous nature of EAFS allows paste to penetrate into aggregates and form a very strong interlocking force between aggregates, which can be thought as the hardened paste forms anchors inside aggregates consequently these anchors enhance the connection between aggregates. In addition, the compressive strength increased as the filled percentage of voids by binder increased which is an obvious result. When the same aggregate is adopted, the compressive strength for pervious concrete made with OPC was lower than that made with AASC. The paste of AASC is known to have a stronger compressive strength than that of OPC [33], therefore this result is natural. It is worthy to mention here that the pervious concrete made with AASC as binder material, EAFS as coarse aggregate, and filled percentage of voids by binder of 90% could have a 28-day compressive strength of 35 MPa and water permeability coefficient of 0.49 cm/s.
W/C=0.35 Agg. A V=70% W/C=0.35 Agg. A V=80% W/C=0.35 Agg. A V=90% W/C=0.35 Agg. A V=100%
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J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
OPC. It is known the cohesion of AASC is stronger than OPC [32], consequently it results in a tighter and smoother surface for AASC. Basically, the pervious concrete made with AASC as binder material, EAFS as coarse aggregate, and filled percentage of voids by binder of 90% can reach a best compressive strength and a satisfactory water permeability had its BPN of 79 which is higher than the required value for all cases referred in [18].
3.6. Sound absorption coefficient The sound absorption coefficients of pervious concretes made with OPC are illustrated in Figs. 6(a) and (b). It can be found that at frequency of 500 Hz, a peak value of sound absorption coefficient appeared for all pervious concrete no matter which aggregate was used. It implied that this peak might reflect the sound absorption characteristic of C–S–H gel. In addition, as the filled percentage of voids by binder increased the sound absorption decreased. Voids inside the pervious concrete contributed to the sound absorption. When the filled percentage of voids by binder increased, the void volume decreased. Consequently, a smaller sound absorption coefficient was obtained. In addition, comparing these two figures one can conclude that pervious concrete made with EAFS had a greater sound absorption coefficient than that made with gravel. From the results of connected porosity, it is known that pervious concrete made with EAFS had a larger void volume than that made with gravel. It then be natural that pervious concrete made with EAFS had a larger sound absorption coefficient.
Sound-absorption coefficient
1
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The sound absorption coefficients for pervious concretes made with AASC are illustrated in Figs. 7(a) and (b). In these figures, the results for pervious concretes made with AASC showed scattered data and no apparent trend can be found. However, for most cases the absorption peak at 500 Hz still existed. It is known that the chemical resultant for AASC contains C–S–H and analogous zeolite structure. According to this, the peak at 500 Hz then is natural since AASC also contains C–S–H. In addition to this, some cases had a peak value at 125–250 Hz which might come from the analogous zeolite structure. This result implied that the pervious concrete made with AASC had a better sound absorption characteristic than that made with OPC. Now, let us examine the performance of pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm). The sound absorption coefficient for it at 125 Hz was 0.94, it meant this pervious concrete could have good sound absorption at low frequency. 4. Conclusions In this article, the performances of pervious concretes made with EAFS and AASC were investigated. The optimum mixture found in this research was the pervious concrete made with EAFS and AASC (void filled percentage of 90%, and aggregate size in the range from 0.24 cm to 0.48 cm). The 28-day compressive strength of it was 35 MPa, the water permeability coefficient was 0.49 cm/s, the BPN was 79 and the sound absorption coefficient at 125 Hz was 0.94. A pervious concrete with high compressive strength could be achieved by using EAFS and AASC. The porous nature of EAFS provided a strong interlocking effect and the AASC was a stronger binding material than OPC. Consequently, a high strength pervious concrete is possible and it can be applied to many engineering applications where the water permeability and strength was required at the same time.
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Acknowledgment 0.4
The authors want to express their thanks for the financial support from the National Science Council, Taiwan under the Grant number NSC 100-2221-E-019-055.
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[1] AJ. Schokker, The Sustainable Concrete Guide – Strategies and Examples, U.S. Green Concrete Council, 2010. [2] J.S. Golden, K.E. Kaloush, Mesoscale and microscale evaluation of surface impacts on the urban heat island effects, Int. J. Pavement Eng. 7 (1) (2006) 37– 52. [3] A. Marolf, N. Neithalath, E. Sell, K. Wegner, J. Weiss, J. Olek, Influence of aggregate size and gradation on acoustic absorption of enhanced porosity concrete, ACI Mater. J. 101 (1) (2004) 82–91. [4] S.B. Park, D.S. Seo, J. Lee, Studies on the sound absorption characteristics of porous concrete based on the content of recycled aggregate and target void ratio, Cem. Concr. Res. 35 (9) (2005) 1846–1854. [5] S.B. Park, M. Tia, An experimental study on the water-purification properties of porous concrete, Cem. Concr. Res. 34 (2) (2004) 177–184. [6] T.C. Fu, W. Yeih, J.J. Chang, R. Huang, The influence of aggregate size and binder material on the properties of pervious concrete, Adv. Mater. Sci. Eng. (2014) (Article ID 963971, 17 pages). [7] T.C. Fu, R. Huang, W. Yeih, J.J. Chang, P.C. Lee, Study of the pervious concrete properties using the experimental design method, Adv. Mater. Res. 1089 (2015) 253–264. [8] L.K. Crouch, J. Pitt, R. Hewitt, Aggregate effects on pervious Portland cement concrete static modulus of elasticity, J. Mater. Civ. Eng. 19 (7) (2007) 561–568. _ Investigating properties of [9] M. Gesog˘lu, E. Güneyisi, G. Khoshnaw, S. Ipek, pervious concrete containing waste tire rubbers, Constr. Build. Mater. 63 (2014) 206–213. _ Abrasion and freezing–thawing [10] M. Gesog˘lu, E. Güneyisi, G. Khoshnaw, S. Ipek, resistance of pervious concrete containing waste rubber, Constr. Build. Mater. 73 (2014) 19–24. [11] W.-T. Kuo, C.-C. Liu, D.-S. Su, Use of washed municipal solid waste incinerator bottom ash in pervious concrete, Cem. Concr. Compos. 37 (2013) 328–335.
40
J.J. Chang et al. / Construction and Building Materials 109 (2016) 34–40
[12] A. Cheng, H.-M. Hsu, S.-J. Chao, K.-L. Lin, Experimental study on properties of pervious concrete made with recycled aggregate, Int. J. Pavement Res. Technol. 4 (2011) 104–110. [13] H. Fujiwara, R. Tomita, T. Okamoto, A. Dozono, A. Obatake, Properties of highstrength porous concrete, ACI SP-179 (1998) 173–188. [14] B. Huang, H. Wu, X. Shu, E.G. Burdette, Laboratory evaluation of permeability and strength of polymer-modified pervious concrete, Constr. Build. Mater. 24 (5) (2010) 818–823. [15] P. Chindaprasirt, S. Hatanaka, T. Chareerat, N. Mishima, Y. Yuasa, Cement paste characteristics and porous concrete properties, Constr. Build. Mater. 22 (5) (2008) 894–901. [16] P. Chindaprasirt, S. Hatanaka, N. Mishima, Y. Yuasa, T. Chareerat, Effects of cement paste strength and aggregate size on the compressive strength and void ratio of porous concrete, Int. J. Mineral Metall. Mater. 16 (6) (2009) 714– 719. [17] J. Yang, G. Jiang, Experimental study on properties of pervious concrete pavement materials, Cem. Concr. Res. 33 (2003) 381–386. [18] W. Yeih, T.C. Fu, J.J. Chang, R. Huang, Properties of pervious concrete made with air-cooling electric arc furnace slag as aggregates, Constr. Build. Mater. 93 (2015) 737–745. [19] Chao Li, H Sun, L. Li, A review: the comparison between alkali-activated slag (Si +Ca) and metakaolin (Si+Al) cements, Cem. Concr. Res. 40 (9) (2010) 1341– 1349. [20] S.A. Bernal, R.M. Gutiérrez, A.L. Pedraza, J.L. Povis, E.D. Rodrigue, S. Delvasto, Effect of binder content on the performance of alkali-activated slag concretes, Cem. Concr. Res. 41 (1) (2011) 1–8. [21] M. Palacios, H. Manzano, J.S. Dolado, A. Rico, Rodrígues, A model for the C-A-SH gel formed in alkali-activated slag cements, J. Eur. Ceram. Soc. 31 (12) (2011) 2043–2056. [22] J.E. Oh, P.J.M. Monterio, S.S. Jun, S. Choi, S.M. Clark, The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers, Cem. Concr. Res. 40 (2) (2010) 189–196.
[23] Y. Fu, L. Cai, W. Yonggen, Freeze–thaw cycle test and damage mechanics models of alkali-activated slag concrete, Constr. Build. Mater. 25 (7) (2011) 3144–3148. [24] T. Tho-in, V. Sata, P. Chindaprasirt, C. Jaturapitakkul, Pervious high-calcium fly ash geopolymer concrete, Constr. Build. Mater. 30 (2012) 366–371. [25] J.J. Chang, W. Yeih, C.C. Hung, Effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag paste, Cem. Concr. Comput. 27 (1) (2005) 85–91. [26] ASTM C138/C138M-14, Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete, ASTM International, PA, USA, 2014. [27] Japan Concrete Association, Test methods for properties of porous concrete, draft, 1998 (in Japanese). [28] Japan Road Association, Pavement Testing Manual, supplement volume, 317, 1996 (in Japanese). [29] ASTM C39/C39M-14, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, ASTM International, PA, USA, 2014. [30] ASTM E303-93, Standard Test Method for Measuring Surface Frictional Properties using the British Pendulum Tester, ASTM International, PA, USA, 2013. [31] ASTM E1050-12, Standard Test Method For Impedance And Absorption Of Acoustical Materials using a Tube, Two Microphones and Digital Frequency Analysis System, ASTM International, PA, USA, 2012. [32] F. Collins, J.G. Sanjayan, Effect of pore size distribution on drying shrinkage of alkali-activated slag concrete, Cem. Concr. Res. 30 (9) (2000) 1401–1406. [33] S.D. Wang, X.C. Pu, K.L. Scrivener, P.L. Pratt, Alkali-activated slag cement and concrete: a review of properties and problems, Adv. Cem. Res. 7 (27) (1995) 93–102.