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Sustainable clean pervious concrete pavement production incorporating palm oil fuel ash as cement replacement
Journal of Cleaner Production 172 (2018) 1476e1485
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Sustainable clean pervious concrete pavement production incorporating palm oil fuel ash as cement replacement Elnaz Khankhaje a, c, *, Mahdi Rafieizonooz a, Mohd Razman Salim b, c, Rawid Khan c, Jahangir Mirza d, e, Ho Chin Siong f, Salmiati b, ** a
Department of Civil Engineering, Gorgan Branch, Islamic Azad University, Gorgan, Iran Centre for Environmental Sustainability and Water Security, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor, Malaysia Department of Civil Engineering, University of Engineering and Technology, Peshawar, Pakistan d Institute for Smart Infrastructures and Innovative Construction, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Malaysia e Department of Materials Science, Research Institute of Hydro-Quebec, 1800 Blvd. Lionel Boulet, Varennes, J3X 1S1, Quebec, Canada f Low Carbon Asia Centre, Faculty of Built Environment, Universiti Teknologi Malaysia, 81310, UTM, Johor Bahru, Johor, Malaysia b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 March 2017 Received in revised form 4 October 2017 Accepted 15 October 2017 Available online 1 November 2017
The significant increase in global urban population and rapid growth of impervious urban surfaces result in erosion of stream channels, flooding, and damage to stormwater infrastructures. The aim of this research was to study pervious concrete pavement as a sustainable solution to control the stormwater at source, reducing heat island effect and enhancing safety of driving. The sustainability of pervious concrete can be increased and the carbon dioxide emissions reduced by replacing a huge amount of ordinary Portland cement with waste materials such as palm oil fuel ash. Palm oil fuel ash is a waste material obtained from the combustion of oil palm shells and fibers in palm oil industry to produce electricity, which caused environmental problems in countries such as Indonesia and Malaysia. This study presented experimental investigations to assess the substitution of control pervious concrete with palm oil fuel ash up to 40% (by mass) to produce sustainable and eco-friendly pervious concrete pavement. Density and void content of specimens were determined at fresh and hardened-state. Falling head permeability test was carried out to investigate the stormwater filtration capacity. Compressive and tensile strengths were conducted on pervious concrete specimens. Skid and abrasion resistances were also employed to evaluate the effects of palm oil fuel ash on safety of driving and surface durability of the pervious concrete pavement. The results showed that void content and water permeability of pervious concrete increased slightly with increasing palm oil fuel ash, while compressive and tensile strengths decreased. They satisfy the typical range for pervious concrete according to American Concrete Institute. A minor effect of palm oil fuel ash on the skid resistance was observed, increasing its substitution levels caused the abrasion resistance of pervious concrete mixtures to decrease. The heavy metal concentrations in leachates of the pervious concrete containing 40% palm oil fuel ash were significantly lower than recommended in the standard. The pervious concrete containing 20% palm oil fuel ash presented the most optimum mixture both technically and environmentally. © 2017 Elsevier Ltd. All rights reserved.
1. Introduction Rapid population growth and urbanization especially in Asia will have a dramatic effect on the demand for large-scale building
* Corresponding author. Department of Civil Engineering, Gorgan Branch, Islamic Azad University, Gorgan, Iran. ** Corresponding author. Centre for Environmental Sustainability and Water Security, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor, Malaysia. E-mail address: [email protected] (E. Khankhaje). https://doi.org/10.1016/j.jclepro.2017.10.159 0959-6526/© 2017 Elsevier Ltd. All rights reserved.
infrastructures; meaning an ever-increasing need for more cement production. According to Aprianti (2015), almost 1 t of CO2 is distributed into the atmosphere due to each ton of cement production. During cement and concrete production, carbon dioxide emissions along with the energy use affect the environment considerably. In order to increase sustainability in green construction, substitution using various forms of waste materials is vital (Mohammadhosseini and Yatim, 2017). More sustainable and eco-friendly concrete can be produced by partial replacement of cement with waste materials, such as fly ash (Rafieizonooz et al., 2016) and palm oil fuel ash (POFA) (Zeyad et al.,
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2017). POFA is one of the waste by-products which is produced from burning of oil palm kernels, empty fruit bunches and fibers as fuel (Awal and Mohammadhosseini, 2016). About 10 Mt of POFA are produced in Malaysia annually (Yusoff, 2006). The costs for POFA disposal is increasing each year which could be addressed if POFA is used in replacing cement in concrete to enhance its properties. This can be addressed by using POFA as cement replacement, which enhanced the properties of concrete (Khankhaje et al., 2016). Several other researches have also carried out studies on the feasibility of using POFA in concrete as cement replacement. Despite the broad based research carried out across the globe in utilizing POFA as a cement replacement material in concrete, the effects of POFA on properties of especial concrete: pervious concrete is still limited. Due to its environmental-friendly manufacturing, pervious concrete pavement is highly endorsed by the Environmental Protection Agency (EPA) of the US (Rahman et al., 2015). Its usages has been shown to improve skid resistance as well as reduce traffic noise (Khankhaje et al., 2017c). In pervious concrete, water is allowed to pass through voids, which is a result of uniform gradation, constrained used of fine aggregates and low water/cement (w/ c) ratio (ACI 552R-10, 2010). Based on Schaefer et al. (2006), a typical range for water permeability of pervious concrete was between 0.25 mm/s and 6.1 mm/s which resulted in void content of pervious concrete ranging between 15% and 30%. Meininger (1988) concluded that a direct relation exists among compressive strength and void content of pervious concrete. Correspondingly, the range of compressive strength for the pervious concrete is between 2 MPa and 28 MPa (Tennis et al., 2004). Yang and Jiang (2003) revealed that because of its lower surface durability (abrasion resistance) and strength (in comparison to normal concrete), pervious concrete is only practicable in areas with low traffic volumes such as local roads, parking lots and road shoulders. Due to its rough surface and open-graded structure, pervious concrete pavement can produce high skid resistance and low abrasion resistance. Skid resistance of road surfaces is essential to traffic safety. Pervious concrete is able to remove storm water off the road surface due to its high void content and more rapid infiltration of storm water into the ground (Schaefer et al., 2006). By reducing water on the pavement surface, skid resistance is noticeably enhanced. With regard to testing skid resistance of pavement, the British Pendulum Number (BPN) test is usually applied. Yoshitake et al. (2016) investigated the skid resistance of concrete pavement containing fly ash. They found that the BPN of fly ash concrete was almost the same as that of the normal concrete. Bonicelli et al. (2015) concluded that the addition of sand and reduction in w/c resulted in greater skid resistance as the cement paste texture became rougher. Hosking (1992) suggested a range of between 45 and 65 acceptable for skid resistance values (BPN) in different wet conditions. The abrasion resistance of concrete pavement was also investigated by several researchers. A test method is needed to help assess the surface durability of pervious
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concrete regardless of its specific conditions (Kevern et al., 2008). The L.A abrasion machine was utilized by Alvarez et al. (2010) to evaluate the abrasion resistance of porous asphalt mixture with similar void content as pervious concrete. Wu et al. (2011) assessed the abrasion resistance of pervious concrete using L.A abrasion machine. They explained that during first 100 revolutions the edges of the cylindrical specimen were smoothed. The shape of the samples became more spherical with increasing in the number of revolutions until some damage occurred in the major part of the samples. They indicated that the weight loss ranged between 35% and 80%. There are limited published studies investigating the use of POFA as cement replacement in pervious concrete to produce greener and cleaner pervious concrete. This research investigated both mechanical characteristics which revealed whether the POFA can be used as a partially cement replacement in pervious concrete, and environmental characteristics. The aim of this study was to utilize POFA up to 40% as a replacement of cement in pervious concrete. The properties such as density, void content, permeability, compressive strength, tensile strength, skid and abrasion resistances were examined and compared with those of control pervious concrete (CPC) without any POFA. 2. Materials An OPC (type I) was used in this study which achieved the requirements of ASTM C150 (2016). Besides that, POFA was used as a substitution of cement. The required POFA was obtained from a palm oil factory located in Johor, the southern part of Malaysia. The raw POFA was then finely ground in a Los Angeles milling device containing ten steel bars that were 800 mm long and 12 mm in diameter for a period of 2 h for each 4 kg of POFA. The ash conformed to the requirements of BS3892: Part 1e1992. According to ASTM C618-15 and considering the source and sort, the ash was neither of class C nor F and may be categorized in between class C and F. The chemical analysis of both OPC and POFA was conducted using energy dispersive spectrometry and their properties are shown in Table 1. In this study, crushed granite with a grain size of 6.30 mm was used as the coarse aggregate. This coarse aggregate showed a water absorption of 1.8% and specific gravity of 2.7 kg/m3. The river sand was used with saturated surface dry (SSD) condition passing through a 4.75 mm sieve, with a fineness modulus of 2.67, a water absorption of 7.4% and a specific gravity of 2.62 kg/m3. The supplied tap water was used in this study for mixing and curing purposes. In all mixtures a constant w/c ratio of 0.32 was used. For the leaching test de-ionized water (pH ¼ 7.7) was used. 2.1. Preparation of specimens A control (CPC) and four pervious concrete mixtures containing
Table 1 Chemical and physical properties of the OPC and POFA. Chemical properties (Wt.%)
CaO SiO2 Al2O3 Fe2O3 MgO SO3 K2O Loss on ignition
Physical properties OPC
POFA
62.4 20.4 5.2 4.2 1.6 2.1 0.005 2.36
8.40 43.60 8.50 10.10 4.80 2.80 3.50 18.00
Specific gravity Specific surface Blain (m2/kg) Initial setting time (min) Final setting time (min)
OPC
POFA
3.15 3.99 125 210
2.42 4.93 e e
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Table 2 Mixture composition of pervious concrete samples. Mix
Rate POFA
Cement (kg/m3)
POFA (kg/m3)
Water (kg/m3)
Coarse aggregate (kg/m3)
Sand (kg/m3)
CPC PPC10 PPC20 PPC30 PPC40
0 10 20 30 40
339.5 305.5 271.6 237.6 203.7
0 34.0 67.9 101.9 135.8
107.54 107.54 107.54 107.54 107.54
1313.8 1313.8 1313.8 1313.8 1313.8
146.0 146.0 146.0 146.0 146.0
POFA (PPC) as cement replacement were prepared. The labels, ‘10’, ‘20’, ‘30’ and ‘40’, indicated the percentage of POFA added with respect to weight of the cement proportion. The details of mixture proportion are listed in Table 2. The samples were cast in cylinder moulds (100-mm diameter 200-mm high) to conduct the density, permeability, void content, compressive strength, tensile strength and abrasion tests. To evaluate skid resistance, the pervious concrete specimens were cast in moulds with dimensions of 200-mm length 100-mm wide 60-mm height. Samples were compacted by filling them in three layers using 25 drops of a (15.9mm diameter) steel rod and 10 drops of a standard Proctor hammer (2.5 kg). Each layer was used as the placement method for all mixtures according to the findings of Khankhaje et al. (2017b). All samples were cured for 24 h in a fog room kept at 20 C ± 2 C and 95% ± 5% relative humidity. The samples were removed from the moulds after 24 h and cured for a 7 d and 28 d.
3. Experimental procedure 3.1. Physical and mechanical tests The compressive strength, as prescribed in ASTM C39 (2015), was conducted at 7 d and 28 d. The compressive strength was applied at 7 d and 28 d intervals using a constant rate loading of 0.06 MPa/s. The splitting tensile strengths were tested based on ASTM C496 (2011). Void content of fresh mixtures were measured as prescribed in ASTM C1688 (2014), whereas, void content of hardened mixtures were performed in agreement with ASTM C1754 (2012). To evaluate the water permeability of the pervious concrete mixtures, the falling-head test was performed and calculated by Eq. (1):
K¼
a1 L h ln 1 a2 t h2
(1)
where K (mm/s) is the water permeability coefficient, L (mm) is the length of specimen, a1 is the area of the cross-section of the tube (mm2), a2 is the area of the cross-section of the specimen (mm2), and t (s) is the time needed for water to fall from h1 ¼ 260 mm to h2 ¼ 60 mm. Fig. 1 shows the test apparatus for water permeability test. To measure abrasion resistance, a Los Angeles (L.A) test was carried out as described in ASTM C1747 (2013) by Los Angeles machine (BC-AS1008, BS Test equipment Company, Malaysia). Five sets of mixtures with 100 mm 100 mm cylinders were tested. The percentage of mass reduction was determined by Eq. (2):
Ml ¼
W1 W2 100 W1
(2)
where Ml is abrasion loss (%), W1 is initial mass of sample (g) and W2 is final mass of sample (g). A portable skid resistance tester (89100, Munro Instrument, UK) was used to measure BPN for both dry and wet conditions of the pervious concrete mixtures in accordance with ASTM E303 (2013).
Fig. 1. Scheme of permeability test (Khankhaje et al., 2017a).
3.2. Leaching test procedure POFA is an agro-industrial waste consists of huge amount of inorganic oxides, such as SiO2, Al2O3, CaO, and Fe2O3, which are considered potential adsorption substances for various pollutants (Shenvi et al., 2016). It is vital to check verify that the pervious concrete containing POFA is not dangerous to the environment. Method 1312 (1994) and SW-846 (2004) are used to investigate the leachability of heavy metals. If the concentration of leached heavy metals exceeds the regulatory standard, the pervious concrete containing POFA is categorized as hazardous material. In this study, the pervious concrete mixture (PPC40) containing the highest amount of POFA at the age of 28 days was selected and crushed to <9 mm. Specimen with glacial acetic acid buffer solution (pH ¼ 2.7 ± 0.05) was rotary agitated at the temperature of 24 C at the frequency of 30 r/min keeping a 1:20 sample-to-solution ratio for 18 h. After agitation, leachates were collected by glass fiber filters and acidified with HNO3 to pH < 2. The heavy metals concentrations in the solution were verified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) (6100 series, Perkin Elmer, USA).
4. Results and discussion 4.1. Fresh and hardened density From Fig. 2, it can be seen that the density of all pervious concrete containing POFA and without POFA (CPC). It was observed that the range for fresh density values was between 1864 kg/m3 and 1930 kg/m3. This range is almost the same as the values
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Fresh
2,000
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Hardened
1,950 1,900
Density (kg/m3)
1,850 1,800 1,750 1,700 1,650 1,600 1,550 1,500 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 2. Density of pervious concrete mixtures.
reported by Tennis et al. (2004), which ranges from 1600 to 2000 kg/m3. The density of pervious concrete mixtures decreased slightly with increasing POFA. This might be due to lower specific gravity of POFA in comparison with cement. Fresh density of pervious concrete containing 10%, 20%, 30% and 40% POFA as the replacement of cement reduced 0.2%, 1%, 2% and 3% respectively, in comparison to that of CPC. It was observed that the effect of POFA replacement up to 40% was a limit on density of pervious concrete mixtures. As anticipated, the hardened density was lower than the fresh density. From Fig. 2, it can be seen that at 28 d age, the density values ranged between 1845 kg/m3 and 1882 kg/m3 for pervious concrete mixtures and can be classified as lightweight concretes. By increasing POFA content, the hardened density of pervious concrete mixtures also slightly decreased. It can also be seen that the minimum hardened-state density was obtained from the mixture containing 40% POFA, which was approximately 2% lower than that of the CPC mixture without any POFA. From Fig. 3, it can be seen that a strong correlation between fresh and hardened density of all pervious concrete samples. A strong correlation between the fresh and hardened density of samples can be concluded. To correlate the values, linear regression method was used as presented in Eq. (3), which gained a coefficient of determination (R2), of 0.98 for pervious concrete mixtures, and showed high certainty for the correlation.
Hd ¼ 0:541 Fd þ 836:37
(3)
where Hd is hardened density (kg/m3) and Fd is fresh density (kg/ m3). 4.2. Fresh and hardened void content From Fig. 4, it can be seen that void content of all mixtures of pervious concrete, measured by volumetric method. It can be concluded that by increasing the POFA from 0 to 40% in pervious concrete mixtures, the fresh and hardened void content increased slightly. This might be due to the high porosity of POFA particles, which causes more water absorption and increasing void content of pervious concrete. From Fig. 4, it can be seen that the maximum hardened-state void content was obtained from the mixture containing 40% POFA, which was approximately 32% higher than that of the CPC without any POFA or fiber. From Fig. 5, it is discernible that a strong correlation exists between hardened density and voids content of pervious concrete specimens. A strong correlation between the hardened density and void content can be noticed. To correlate the values, linear regression method was applied as shown in Eq. (4), which gained R2 of 0.93 for all mixtures, and presented high certainty for the correlation.
Fresh
30
Hardened
Void content (%)
25 20 15 10 5 0 CPC
Fig. 3. Relationship between fresh and hardened density.
PPC10
PPC20 Mixture
PPC30
Fig. 4. Void content of pervious concrete mixtures.
PPC40
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Fig. 7. Correlation between void content and permeability.
Fig. 5. Relationship between density and void content.
Hd ¼ 9:054 V þ 2094:4
(4)
where Hd is hardened density (kg/m3) and V is void content (%).
4.3. Water permeability The permeability of pervious concrete pavement must be at least 5.4 m/s for water can pass easily (Nguyen et al., 2013). From Fig. 6, it is apparent that the permeability coefficient values measured by falling head test, for all specimens were higher than 5.4 m/s. The permeability coefficients values ranged from 5.80 mm/ s to 10.49 mm/s. The water permeability increase is directly proportional to POFA increment. These results can be explained by the void content of the pervious concrete mixtures which increases with increasing content of POFA (Fig. 6). The permeability values increased by 28%, 44%, 81% and 132% for mixtures containing 10%, 20%, 30% and 40% POFA compared to that of CPC mixture, respectively. These results were comparable with the findings of Tennis et al. (2004) which reported that the typical range of permeability values for pervious concrete was between 2 mm/s and 12 mm/s.
To show the correlation among voids content and water permeability obtained from the results of the study, one of the most commonly used analytical models i. e., exponential regression method was used. The correlation among the water permeability and void content is illustrated in Fig. 7. It is fairly obvious that a very strong relationship exists among them. The coefficient of determination (R2) presenting an overall change in the dependent variables is also accounted for the regression equation, which was 0.99 as determined from Eq. (5).
K ¼ 0:0568e0:1992V
(5)
where, K is water permeability coefficient (mm/s) and V is void content (%). 4.4. Compressive strength The compressive strength of pervious concrete mixtures incorporating POFA is illustrated in Fig. 8. As the POFA content of mixtures increased, the compressive strength of mixtures decreased at 7 d and 28 d of curing. The compressive strength of PPC10, PPC20, PPC30 and PPC40 pervious concrete mixtures decreased by 9%, 20%, 30% and 49% respectively, compared to the CPC at 28 d of curing
16
Water permeability (mm/s)
14 12 10 8 6 4 2 0 CPC
PPC10
PPC20 Mixture
PPC30
Fig. 6. Water permeability of pervious concrete mixtures.
PPC40
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16
7 days
1481
28 days
Compressive strength (MPa)
14 12 10 8 6 4 2 0 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 8. Compressive strength of pervious concrete specimens at 7 d and 28 d.
time. This might be due to the delay in hydration and slow pozzolanic reaction of POFA, which prevented the increase in compressive strength. The reduction in compressive strength of the mixtures incorporating POFA is attributed to the spongy structure of POFA particles, which leads to more water absorption, increasing void content and decreasing compressive strength of pervious concrete samples. The results obtained in this study showed that obtained compressive strengths of pervious concrete containing POFA were within the acceptable range, as reported by ACI for strength of pervious concrete (2e28 MPa) (Tennis et al., 2004). The compressive strength value of the pervious concrete mixture containing up to 20% of POFA was almost comparable to the value of the CPC mixture. The failure mode of pervious concrete mixture containing 20% POFA was almost the same as that of mixture without any POFA as illustrated in Fig. 9. A linear correlation among compressive strength and void content of the pervious concrete mixtures can be deduced from the results (Fig. 10). The strong correlation among the compressive strength and void content can be observed. The R2 value was 0.97 for Eq. (6), signifying high certainty for the correlation.
4.5. Tensile strength From Fig. 11, it can be seen that the value of tensile strength test of all pervious concrete samples. The range of tensile strength of all samples were between 1.64 MPa and 2.47 MPa. As shown in the figure, tensile strength decreased as POFA contents increased. This trend was similar to that of compressive strength as well. The replacement of cement with 10, 20, 30 and 40% of POFA decreased the tensile strength by 1%, 18%, 22% and 34%, respectively compared with pervious concrete without any POFA (CPC). This could be due to the delay in hydration and slow pozzolanic reaction of POFA, which prevented the increase in tensile strength. These results indicated that all of the strength parameters for pervious concrete mixtures incorporating POFA are within the typical ranges for pervious concrete with OPC alone (1e3 MPa) (Tennis et al., 2004). From Fig. 12, it can be seen that a strong relationship between the compressive and tensile strengths values of pervious concrete mixtures containing POFA. A linear regression method was applied to correlate the experimental results as in Eq. (7), which has a R2 value of 0.95 for all samples.
Ft ¼ 0:128 Fc þ 0:681 Fc ¼ 1:6481 V þ 52:722 where, Fc is compressive strength and V is void content (%).
(6)
(7)
where, Ft is tensile strength (MPa) and Fc is compressive strength (MPa). The tensile strength values of the pervious concrete mixture containing up to 20% of POFA were almost comparable to the value of the CPC mixture. It was also observed that failure mode of pervious concrete mixture containing 20% POFA (PPC20) was almost similar to the mixture without any POFA (CPC) in tension, as shown in Fig. 13. 4.6. Skid resistance
Fig. 9. Failure modes of pervious concrete specimens in compression.
The skid resistance (British Pendulum Number or BPN) of the pervious concrete mixtures for both dry and wet conditions is presented in Fig. 14. The error bars for the skid resistance measurements indicated one standard deviation for the BPN of four swings, which were made on the surface of each pervious concrete specimen. As illustrated in Fig. 14, the skid resistance values of specimens containing POFA was comparable to value of CPC. The effect of POFA
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16
Compressive strength (MPa)
14 12 10
Fc = -1.6481×V + 52.722
8
R² = 0.969
6 4 2 0 20
21
22
23
24
25
26
27
28
Void content (%) Fig. 10. Correlation among compressive strength and void content.
3
Tensil strength (MPa)
2.5 2 1.5 1 0.5 0 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 11. Tensile strength of pervious concrete mixtures.
Fig. 12. Correlation among compressive and tensile strengths.
Fig. 13. Failure modes of pervious concrete specimens containing 0% and 20% POFA in tension.
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120
Dry
1483
wet
Skid resistance (BPN)
100 80 60 40 20 0 CPC
PPC10
PPC20
PPC30
PPC40
Mixture Fig. 14. Skid resistance of pervious concrete mixtures.
on the skid resistance of the pervious concrete mixtures was not notable. The BPN in wet conditions for PPC10, PPC20, PPC30 and PPC40 were 71, 70.5, 69.7 and 68.7 respectively, which were almost similar to that of CPC (71.5). Bonicelli et al. (2015) found comparable range of BPN for pervious concrete mixtures (60e75). Increasing POFA content in pervious concrete mixture caused skid resistance to decrease slightly. Ralph Haas et al. (1994) reported that both the microtexture of a pavement's surface affected skid resistance. This phenomenon can be explained by the smoother surface of pervious concrete mixture containing POFA than the mixture without any POFA (CPC). As such, the high skid resistance of the PPC mixtures might be due to the finer particles of POFA than cement, which decreased the surface friction of the PPC specimens.
slightly reduced with increase in revolutions. It is possible that by increasing the revolutions, the shape of samples became more and more spherical (Fig. 16). It can be noted that 29e48% of the pervious concrete mixture weight was lost after 500 revolutions. The weight loss for PPC10, PPC20, PPC30 and PPC40 were 32, 35, 41 and 48% respectively, when compared to that of CPC (29%), after 500 revolutions. By increasing POFA the weight loss of specimens increased slightly which could be due to lower strength of the pervious concrete mixtures incorporating POFA compared with mixture without POFA (CPC). Wu et al. (2011) reported almost similar results. They found that 20% of the pervious concrete specimen weight was lost after 300 revolutions. 4.8. Heavy metal leachability
4.7. Abrasion resistance To monitor the trend of abrasion mass loss, the samples were weighed after each 100 revolutions till 500 revolutions were achieved. The mass loss variation rate of all pervious concrete specimens is presented in Fig. 15. The mass loss of the specimens increased with increasing revolutions. The mass loss rate was
CPC
PPC10
The leachability of waste materials is essential and a significant factor in assessing the environmental impact. The heavy metals leaching of the crushed pervious concrete incorporating 40% of POFA are presented in Table 3. According to the results, all dissolved concentrations of heavy metals for pervious concrete mixture containing 40% POFA used in this study, were minimal than that of
PPC20
PPC30
PPC40
60
Weight loss (%)
50 40 30 20 10 0 0
100
200
300
Revelutions Fig. 15. Abrasion resistance of pervious concrete mixtures.
400
500
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minimal effect on the skid and abrasion resistance of pervious concrete mixtures. Due to the water permeability, the strength of pervious concrete containing POFA was only 20 MPa. Heavy metals leaching concentrations from pervious concrete containing POFA were extremely lower than that of the regulation. From the environmental point of view, POFA is safe to be used in the field. References
Fig. 16. Specimen containing 20% POFA in L.A abrasion test at various revolutions.
Table 3 Heavy metal leachability of crushed pervious concrete containing 40% POFA (mg/L). Heavy metals
Cr
Zn
Cd
Pb
Ni
Cu
PPC40 Standard Limitation SW-846 (2004)
0.013 5
0.121 250
0.001 1
0.003 5
0.010 20
0.011 25
the required regulations, thus qualifying it for recycling purposes. Although the hardened mixture was crushed into size of smaller than 9 mm, the values of heavy metals leaching concentrations were within the acceptable range. Hardened pervious concrete leaching in situ is a slowly mitigating process and only limited grains are smaller than 9 mm in comparison with the experimental condition. Therefore, the heavy metals immobilizing of crushed pervious concrete containing POFA might be more reliable in the field environment. 5. Conclusions In this study, 10e40% of OPC was substituted with POFA by mass in pervious concrete mixture. The fresh and hardened characteristics of pervious concrete containing POFA were evaluated. The effect of 20% POFA replacement up to was minimal in terms of void content and permeability of the pervious concrete mixtures. By increasing POFA up to 40% the void content and permeability increased. 10%e20% of cement replacement with POFA was determined as optimum substitution range for compressive and tensile strengths of pervious concrete. By increasing POFA from 30% to 40%, compressive and tensile strengths deceased. They satisfied the typical range for compressive strength (2e28 MPa) of pervious concrete as described in ACI. It is recommended for use in general bicycle ways, sidewalks, and landscaping. Strong correlations were found among different hardened properties of pervious concrete mixtures. Density, permeability and compressive strength can be predicted from the void content values. The compressive strength of pervious concrete mixture can be used to predict the tensile strength of pervious concrete mixture. Addition of POFA had a
ACI 552R-10, 2010. Report on pervious concrete, American concrete institute. American Concrete Institute, Farmington Hills, Mishigan. Alvarez, A.E., Epps-Martin, A., Estakhri, C., 2010. “Evaluation of durability tests for permeable friction course mixtures. Int. J. Pavement Eng. 11, 49e60. Aprianti, S.E., 2015. A huge number of artificial waste material can be supplementary cementitious material (SCM) for concrete production - a review part II. J. Clean. Prod. 142, 4178e4194. https://doi.org/10.1016/j.jclepro.2015.12.115. ASTM C1754/C1754M-12, 2012. Standard Test Method for Density and Void Content of Hardened Pervious Concrete. ASTM Int, West Conshohocken, PA. ASTM C39/C39M-15a, 2015. Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. ASTM Int, West Conshohocken, PA. ASTM C496/C496M, 2011. Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete. ASTM Int, West Conshohocken, PA. ASTM C150/C150M-16e1, 2016. Standard Specification for Portland Cement. ASTM Int, West Conshohocken, PA. ASTM C1688/C1688M-14a, 2014. Standard Test Method for Density and Void Content of Freshly Mixed Pervious Concrete. ASTM International, West Conshohocken, PA. ASTM C1747/C1747M-13, 2013. Standard Test Method for Determining Potential Resistance to Degradation of Pervious Concrete by Impact and Abrasion. ASTM Int, West Conshohocken, PA. ASTM E303, 2013. Standard Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester. ASTM Int, West Conshohocken, PA. Awal, A.S.M.A., Mohammadhosseini, H., 2016. Green concrete production incorporating waste carpet fiber and palm oil fuel ash. J. Clean. Prod. 137, 157e166. https://doi.org/10.1016/j.jclepro.2016.06.162. Bonicelli, A., Giustozzi, F., Crispino, M., 2015. Experimental study on the effects of fine sand addition on differentially compacted pervious concrete. Constr. Build. Mater 91, 102e110. https://doi.org/10.1016/j.conbuildmat.2015.05.012. Hosking, R., 1992. State of the Art Review 4, Road Aggregates and Skidding. HMSO, London. Kevern, John, Schaefer, V., Wang, K., 2008. The effect of curing regime on pervious concrete abrasion resistance. J. Test. Eval. 37. Khankhaje, E., Hussin, M.W., Mirza, J., Rafieizonooz, M., Salim, M.R., Siong, H.C., Warid, M.N.M., 2016. On blended cement and geopolymer concretes containing palm oil fuel ash. Mater. Des. 89, 385e398. https://doi.org/10.1016/ j.matdes.2015.09.140. Khankhaje, E., Rafieizonooz, M., Salim, M.R., Mirza, J., Salmiati, Hussin, M.W., 2017a. Comparing the effects of oil palm kernel shell and cockle shell on properties of pervious concrete pavement. Int. J. Pavement Res. Technol. https://doi.org/ 10.1016/j.ijprt.2017.05.003. Khankhaje, E., Razman, M., Mirza, J., Warid, M., 2017b. Sustainable pervious concrete incorporating palm oil fuel ash as cement replacement. Chem. Eng. Trans. 56, 445e450. Khankhaje, E., Salim, M.R., Mirza, J., Salmiati, Hussin, M.W., Khan, R., Rafieizonooz, M., 2017c. Properties of quiet pervious concrete containing oil palm kernel shell and cockleshell. Appl. Acoust. 122, 113e120. https://doi.org/ 10.1016/j.apacoust.2017.02.014. Meininger, R.C., 1988. No-fines Pervious Concrete for Paving. National Ready Mixed Concrete Association, p. 175. Method 1312, 1994. Synthetic Precipitation Leaching Procedure. Environmental Protection Agency (EPA). Mohammadhosseini, H., Yatim, J.M., 2017. Microstructure and residual properties of green concrete composites incorporating waste carpet fibers and palm oil fuel ash at elevated temperatures. J. Clean. Prod. 144, 8e21. https://doi.org/10.1016/ j.jclepro.2016.12.168. Nguyen, D.H., Boutouil, M., Sebaibi, N., Leleyter, L., Baraud, F., 2013. Valorization of seashell by-products in pervious concrete pavers. Constr. Build. Mater 49, 151e160. https://doi.org/10.1016/j.conbuildmat.2013.08.017. Rafieizonooz, M., Mirza, J., Salim, M.R., Hussin, M.W., Khankhaje, E., 2016. Investigation of coal bottom ash and fly ash in concrete as replacement for sand and cement. Constr. Build. Mater 116, 15e24. https://doi.org/10.1016/ j.conbuildmat.2016.04.080. Rahman, M.A., Imteaz, M.A., Arulrajah, A., Piratheepan, J., Disfani, M.M., 2015. Recycled construction and demolition materials in permeable pavement systems: geotechnical and hydraulic characteristics. J. Clean. Prod. 90, 183e194. https://doi.org/10.1016/j.jclepro.2014.11.042. Ralph Haas, W., Hudson, R., Zaniewski, J.P., 1994. Modern Pavement Management, second ed. Krieger Pub. Co. Schaefer, V., Wang, K., Suleiman, M., Kevern, J., 2006. Mix design development for pervious concrete in cold weather climates. Cent. Transp. Res. Educ. Iowa State Univ. 67. Shenvi, S.S., Isloor, Arun M., Ahmad, A.L., Garudachari, B., Ismail, A.F., 2016.
E. Khankhaje et al. / Journal of Cleaner Production 172 (2018) 1476e1485 Influence of palm oil fuel ash, an agro-industry waste on the ultrafiltration performance of cellulose acetate butyrate membrane. Desalin. Water Treat. 57, 55e57. https://doi.org/10.1080/19443994.2016.1171169. SW-846, 2004. In: Characteristics Introduction and Regulatory Definitions. Environmental Protection Agency (EPA), United State. Tennis, P., Leming, M., Akers, D., 2004. Pervious Concrete Pavements, National Ready Mixed Concrete Association (NRMCA). Portland Cement Association Skokie Illinois and National Ready Mixed Concrete Association. Silver Spring, Maryland: Silver Spring. Wu, H., Huang, B., Shu, X., Dong, Q., 2011. Laboratory evaluation of abrasion resistance of Portland cement pervious concrete. J. Mater. Civ. Eng. 23, 697e702. https://doi.org/10.1061/(ASCE)MT.1943-5533.0000210. Yang, J., Jiang, G., 2003. Experimental study on properties of pervious concrete
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pavement materials. Cem. Concr. Res. 33, 381e386. Yoshitake, I., Ueno, S., Ushio, Y., Arano, H., Fukumoto, S., 2016. Abrasion and skid resistance of recyclable fly ash concrete pavement made with limestone aggregate. Constr. Build. Mater 112, 440e446. https://doi.org/10.1016/ j.conbuildmat.2016.02.185. Yusoff, S., 2006. Renewable energy from palm oil e innovation on effective utilization of waste. J. Clean. Prod. 14, 87e93. https://doi.org/10.1016/ j.jclepro.2004.07.005. Zeyad, A.M., Megat, M.A., Tayeh, B.A., Yusuf, M.O., 2017. Pozzolanic reactivity of ultra fi ne palm oil fuel ash waste on strength and durability performances of high strength concrete. J. Clean. Prod. 144, 511e522. https://doi.org/10.1016/ j.jclepro.2016.12.121.
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Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Sustainable clean pervious concrete pavement production incorporating palm oil fuel ash as cement replacement Elnaz Khankhaje a, c, *, Mahdi Rafieizonooz a, Mohd Razman Salim b, c, Rawid Khan c, Jahangir Mirza d, e, Ho Chin Siong f, Salmiati b, ** a
Department of Civil Engineering, Gorgan Branch, Islamic Azad University, Gorgan, Iran Centre for Environmental Sustainability and Water Security, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor, Malaysia Department of Civil Engineering, University of Engineering and Technology, Peshawar, Pakistan d Institute for Smart Infrastructures and Innovative Construction, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Malaysia e Department of Materials Science, Research Institute of Hydro-Quebec, 1800 Blvd. Lionel Boulet, Varennes, J3X 1S1, Quebec, Canada f Low Carbon Asia Centre, Faculty of Built Environment, Universiti Teknologi Malaysia, 81310, UTM, Johor Bahru, Johor, Malaysia b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 March 2017 Received in revised form 4 October 2017 Accepted 15 October 2017 Available online 1 November 2017
The significant increase in global urban population and rapid growth of impervious urban surfaces result in erosion of stream channels, flooding, and damage to stormwater infrastructures. The aim of this research was to study pervious concrete pavement as a sustainable solution to control the stormwater at source, reducing heat island effect and enhancing safety of driving. The sustainability of pervious concrete can be increased and the carbon dioxide emissions reduced by replacing a huge amount of ordinary Portland cement with waste materials such as palm oil fuel ash. Palm oil fuel ash is a waste material obtained from the combustion of oil palm shells and fibers in palm oil industry to produce electricity, which caused environmental problems in countries such as Indonesia and Malaysia. This study presented experimental investigations to assess the substitution of control pervious concrete with palm oil fuel ash up to 40% (by mass) to produce sustainable and eco-friendly pervious concrete pavement. Density and void content of specimens were determined at fresh and hardened-state. Falling head permeability test was carried out to investigate the stormwater filtration capacity. Compressive and tensile strengths were conducted on pervious concrete specimens. Skid and abrasion resistances were also employed to evaluate the effects of palm oil fuel ash on safety of driving and surface durability of the pervious concrete pavement. The results showed that void content and water permeability of pervious concrete increased slightly with increasing palm oil fuel ash, while compressive and tensile strengths decreased. They satisfy the typical range for pervious concrete according to American Concrete Institute. A minor effect of palm oil fuel ash on the skid resistance was observed, increasing its substitution levels caused the abrasion resistance of pervious concrete mixtures to decrease. The heavy metal concentrations in leachates of the pervious concrete containing 40% palm oil fuel ash were significantly lower than recommended in the standard. The pervious concrete containing 20% palm oil fuel ash presented the most optimum mixture both technically and environmentally. © 2017 Elsevier Ltd. All rights reserved.
1. Introduction Rapid population growth and urbanization especially in Asia will have a dramatic effect on the demand for large-scale building
* Corresponding author. Department of Civil Engineering, Gorgan Branch, Islamic Azad University, Gorgan, Iran. ** Corresponding author. Centre for Environmental Sustainability and Water Security, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor, Malaysia. E-mail address: [email protected] (E. Khankhaje). https://doi.org/10.1016/j.jclepro.2017.10.159 0959-6526/© 2017 Elsevier Ltd. All rights reserved.
infrastructures; meaning an ever-increasing need for more cement production. According to Aprianti (2015), almost 1 t of CO2 is distributed into the atmosphere due to each ton of cement production. During cement and concrete production, carbon dioxide emissions along with the energy use affect the environment considerably. In order to increase sustainability in green construction, substitution using various forms of waste materials is vital (Mohammadhosseini and Yatim, 2017). More sustainable and eco-friendly concrete can be produced by partial replacement of cement with waste materials, such as fly ash (Rafieizonooz et al., 2016) and palm oil fuel ash (POFA) (Zeyad et al.,
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2017). POFA is one of the waste by-products which is produced from burning of oil palm kernels, empty fruit bunches and fibers as fuel (Awal and Mohammadhosseini, 2016). About 10 Mt of POFA are produced in Malaysia annually (Yusoff, 2006). The costs for POFA disposal is increasing each year which could be addressed if POFA is used in replacing cement in concrete to enhance its properties. This can be addressed by using POFA as cement replacement, which enhanced the properties of concrete (Khankhaje et al., 2016). Several other researches have also carried out studies on the feasibility of using POFA in concrete as cement replacement. Despite the broad based research carried out across the globe in utilizing POFA as a cement replacement material in concrete, the effects of POFA on properties of especial concrete: pervious concrete is still limited. Due to its environmental-friendly manufacturing, pervious concrete pavement is highly endorsed by the Environmental Protection Agency (EPA) of the US (Rahman et al., 2015). Its usages has been shown to improve skid resistance as well as reduce traffic noise (Khankhaje et al., 2017c). In pervious concrete, water is allowed to pass through voids, which is a result of uniform gradation, constrained used of fine aggregates and low water/cement (w/ c) ratio (ACI 552R-10, 2010). Based on Schaefer et al. (2006), a typical range for water permeability of pervious concrete was between 0.25 mm/s and 6.1 mm/s which resulted in void content of pervious concrete ranging between 15% and 30%. Meininger (1988) concluded that a direct relation exists among compressive strength and void content of pervious concrete. Correspondingly, the range of compressive strength for the pervious concrete is between 2 MPa and 28 MPa (Tennis et al., 2004). Yang and Jiang (2003) revealed that because of its lower surface durability (abrasion resistance) and strength (in comparison to normal concrete), pervious concrete is only practicable in areas with low traffic volumes such as local roads, parking lots and road shoulders. Due to its rough surface and open-graded structure, pervious concrete pavement can produce high skid resistance and low abrasion resistance. Skid resistance of road surfaces is essential to traffic safety. Pervious concrete is able to remove storm water off the road surface due to its high void content and more rapid infiltration of storm water into the ground (Schaefer et al., 2006). By reducing water on the pavement surface, skid resistance is noticeably enhanced. With regard to testing skid resistance of pavement, the British Pendulum Number (BPN) test is usually applied. Yoshitake et al. (2016) investigated the skid resistance of concrete pavement containing fly ash. They found that the BPN of fly ash concrete was almost the same as that of the normal concrete. Bonicelli et al. (2015) concluded that the addition of sand and reduction in w/c resulted in greater skid resistance as the cement paste texture became rougher. Hosking (1992) suggested a range of between 45 and 65 acceptable for skid resistance values (BPN) in different wet conditions. The abrasion resistance of concrete pavement was also investigated by several researchers. A test method is needed to help assess the surface durability of pervious
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concrete regardless of its specific conditions (Kevern et al., 2008). The L.A abrasion machine was utilized by Alvarez et al. (2010) to evaluate the abrasion resistance of porous asphalt mixture with similar void content as pervious concrete. Wu et al. (2011) assessed the abrasion resistance of pervious concrete using L.A abrasion machine. They explained that during first 100 revolutions the edges of the cylindrical specimen were smoothed. The shape of the samples became more spherical with increasing in the number of revolutions until some damage occurred in the major part of the samples. They indicated that the weight loss ranged between 35% and 80%. There are limited published studies investigating the use of POFA as cement replacement in pervious concrete to produce greener and cleaner pervious concrete. This research investigated both mechanical characteristics which revealed whether the POFA can be used as a partially cement replacement in pervious concrete, and environmental characteristics. The aim of this study was to utilize POFA up to 40% as a replacement of cement in pervious concrete. The properties such as density, void content, permeability, compressive strength, tensile strength, skid and abrasion resistances were examined and compared with those of control pervious concrete (CPC) without any POFA. 2. Materials An OPC (type I) was used in this study which achieved the requirements of ASTM C150 (2016). Besides that, POFA was used as a substitution of cement. The required POFA was obtained from a palm oil factory located in Johor, the southern part of Malaysia. The raw POFA was then finely ground in a Los Angeles milling device containing ten steel bars that were 800 mm long and 12 mm in diameter for a period of 2 h for each 4 kg of POFA. The ash conformed to the requirements of BS3892: Part 1e1992. According to ASTM C618-15 and considering the source and sort, the ash was neither of class C nor F and may be categorized in between class C and F. The chemical analysis of both OPC and POFA was conducted using energy dispersive spectrometry and their properties are shown in Table 1. In this study, crushed granite with a grain size of 6.30 mm was used as the coarse aggregate. This coarse aggregate showed a water absorption of 1.8% and specific gravity of 2.7 kg/m3. The river sand was used with saturated surface dry (SSD) condition passing through a 4.75 mm sieve, with a fineness modulus of 2.67, a water absorption of 7.4% and a specific gravity of 2.62 kg/m3. The supplied tap water was used in this study for mixing and curing purposes. In all mixtures a constant w/c ratio of 0.32 was used. For the leaching test de-ionized water (pH ¼ 7.7) was used. 2.1. Preparation of specimens A control (CPC) and four pervious concrete mixtures containing
Table 1 Chemical and physical properties of the OPC and POFA. Chemical properties (Wt.%)
CaO SiO2 Al2O3 Fe2O3 MgO SO3 K2O Loss on ignition
Physical properties OPC
POFA
62.4 20.4 5.2 4.2 1.6 2.1 0.005 2.36
8.40 43.60 8.50 10.10 4.80 2.80 3.50 18.00
Specific gravity Specific surface Blain (m2/kg) Initial setting time (min) Final setting time (min)
OPC
POFA
3.15 3.99 125 210
2.42 4.93 e e
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Table 2 Mixture composition of pervious concrete samples. Mix
Rate POFA
Cement (kg/m3)
POFA (kg/m3)
Water (kg/m3)
Coarse aggregate (kg/m3)
Sand (kg/m3)
CPC PPC10 PPC20 PPC30 PPC40
0 10 20 30 40
339.5 305.5 271.6 237.6 203.7
0 34.0 67.9 101.9 135.8
107.54 107.54 107.54 107.54 107.54
1313.8 1313.8 1313.8 1313.8 1313.8
146.0 146.0 146.0 146.0 146.0
POFA (PPC) as cement replacement were prepared. The labels, ‘10’, ‘20’, ‘30’ and ‘40’, indicated the percentage of POFA added with respect to weight of the cement proportion. The details of mixture proportion are listed in Table 2. The samples were cast in cylinder moulds (100-mm diameter 200-mm high) to conduct the density, permeability, void content, compressive strength, tensile strength and abrasion tests. To evaluate skid resistance, the pervious concrete specimens were cast in moulds with dimensions of 200-mm length 100-mm wide 60-mm height. Samples were compacted by filling them in three layers using 25 drops of a (15.9mm diameter) steel rod and 10 drops of a standard Proctor hammer (2.5 kg). Each layer was used as the placement method for all mixtures according to the findings of Khankhaje et al. (2017b). All samples were cured for 24 h in a fog room kept at 20 C ± 2 C and 95% ± 5% relative humidity. The samples were removed from the moulds after 24 h and cured for a 7 d and 28 d.
3. Experimental procedure 3.1. Physical and mechanical tests The compressive strength, as prescribed in ASTM C39 (2015), was conducted at 7 d and 28 d. The compressive strength was applied at 7 d and 28 d intervals using a constant rate loading of 0.06 MPa/s. The splitting tensile strengths were tested based on ASTM C496 (2011). Void content of fresh mixtures were measured as prescribed in ASTM C1688 (2014), whereas, void content of hardened mixtures were performed in agreement with ASTM C1754 (2012). To evaluate the water permeability of the pervious concrete mixtures, the falling-head test was performed and calculated by Eq. (1):
K¼
a1 L h ln 1 a2 t h2
(1)
where K (mm/s) is the water permeability coefficient, L (mm) is the length of specimen, a1 is the area of the cross-section of the tube (mm2), a2 is the area of the cross-section of the specimen (mm2), and t (s) is the time needed for water to fall from h1 ¼ 260 mm to h2 ¼ 60 mm. Fig. 1 shows the test apparatus for water permeability test. To measure abrasion resistance, a Los Angeles (L.A) test was carried out as described in ASTM C1747 (2013) by Los Angeles machine (BC-AS1008, BS Test equipment Company, Malaysia). Five sets of mixtures with 100 mm 100 mm cylinders were tested. The percentage of mass reduction was determined by Eq. (2):
Ml ¼
W1 W2 100 W1
(2)
where Ml is abrasion loss (%), W1 is initial mass of sample (g) and W2 is final mass of sample (g). A portable skid resistance tester (89100, Munro Instrument, UK) was used to measure BPN for both dry and wet conditions of the pervious concrete mixtures in accordance with ASTM E303 (2013).
Fig. 1. Scheme of permeability test (Khankhaje et al., 2017a).
3.2. Leaching test procedure POFA is an agro-industrial waste consists of huge amount of inorganic oxides, such as SiO2, Al2O3, CaO, and Fe2O3, which are considered potential adsorption substances for various pollutants (Shenvi et al., 2016). It is vital to check verify that the pervious concrete containing POFA is not dangerous to the environment. Method 1312 (1994) and SW-846 (2004) are used to investigate the leachability of heavy metals. If the concentration of leached heavy metals exceeds the regulatory standard, the pervious concrete containing POFA is categorized as hazardous material. In this study, the pervious concrete mixture (PPC40) containing the highest amount of POFA at the age of 28 days was selected and crushed to <9 mm. Specimen with glacial acetic acid buffer solution (pH ¼ 2.7 ± 0.05) was rotary agitated at the temperature of 24 C at the frequency of 30 r/min keeping a 1:20 sample-to-solution ratio for 18 h. After agitation, leachates were collected by glass fiber filters and acidified with HNO3 to pH < 2. The heavy metals concentrations in the solution were verified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) (6100 series, Perkin Elmer, USA).
4. Results and discussion 4.1. Fresh and hardened density From Fig. 2, it can be seen that the density of all pervious concrete containing POFA and without POFA (CPC). It was observed that the range for fresh density values was between 1864 kg/m3 and 1930 kg/m3. This range is almost the same as the values
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Fresh
2,000
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Hardened
1,950 1,900
Density (kg/m3)
1,850 1,800 1,750 1,700 1,650 1,600 1,550 1,500 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 2. Density of pervious concrete mixtures.
reported by Tennis et al. (2004), which ranges from 1600 to 2000 kg/m3. The density of pervious concrete mixtures decreased slightly with increasing POFA. This might be due to lower specific gravity of POFA in comparison with cement. Fresh density of pervious concrete containing 10%, 20%, 30% and 40% POFA as the replacement of cement reduced 0.2%, 1%, 2% and 3% respectively, in comparison to that of CPC. It was observed that the effect of POFA replacement up to 40% was a limit on density of pervious concrete mixtures. As anticipated, the hardened density was lower than the fresh density. From Fig. 2, it can be seen that at 28 d age, the density values ranged between 1845 kg/m3 and 1882 kg/m3 for pervious concrete mixtures and can be classified as lightweight concretes. By increasing POFA content, the hardened density of pervious concrete mixtures also slightly decreased. It can also be seen that the minimum hardened-state density was obtained from the mixture containing 40% POFA, which was approximately 2% lower than that of the CPC mixture without any POFA. From Fig. 3, it can be seen that a strong correlation between fresh and hardened density of all pervious concrete samples. A strong correlation between the fresh and hardened density of samples can be concluded. To correlate the values, linear regression method was used as presented in Eq. (3), which gained a coefficient of determination (R2), of 0.98 for pervious concrete mixtures, and showed high certainty for the correlation.
Hd ¼ 0:541 Fd þ 836:37
(3)
where Hd is hardened density (kg/m3) and Fd is fresh density (kg/ m3). 4.2. Fresh and hardened void content From Fig. 4, it can be seen that void content of all mixtures of pervious concrete, measured by volumetric method. It can be concluded that by increasing the POFA from 0 to 40% in pervious concrete mixtures, the fresh and hardened void content increased slightly. This might be due to the high porosity of POFA particles, which causes more water absorption and increasing void content of pervious concrete. From Fig. 4, it can be seen that the maximum hardened-state void content was obtained from the mixture containing 40% POFA, which was approximately 32% higher than that of the CPC without any POFA or fiber. From Fig. 5, it is discernible that a strong correlation exists between hardened density and voids content of pervious concrete specimens. A strong correlation between the hardened density and void content can be noticed. To correlate the values, linear regression method was applied as shown in Eq. (4), which gained R2 of 0.93 for all mixtures, and presented high certainty for the correlation.
Fresh
30
Hardened
Void content (%)
25 20 15 10 5 0 CPC
Fig. 3. Relationship between fresh and hardened density.
PPC10
PPC20 Mixture
PPC30
Fig. 4. Void content of pervious concrete mixtures.
PPC40
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Fig. 7. Correlation between void content and permeability.
Fig. 5. Relationship between density and void content.
Hd ¼ 9:054 V þ 2094:4
(4)
where Hd is hardened density (kg/m3) and V is void content (%).
4.3. Water permeability The permeability of pervious concrete pavement must be at least 5.4 m/s for water can pass easily (Nguyen et al., 2013). From Fig. 6, it is apparent that the permeability coefficient values measured by falling head test, for all specimens were higher than 5.4 m/s. The permeability coefficients values ranged from 5.80 mm/ s to 10.49 mm/s. The water permeability increase is directly proportional to POFA increment. These results can be explained by the void content of the pervious concrete mixtures which increases with increasing content of POFA (Fig. 6). The permeability values increased by 28%, 44%, 81% and 132% for mixtures containing 10%, 20%, 30% and 40% POFA compared to that of CPC mixture, respectively. These results were comparable with the findings of Tennis et al. (2004) which reported that the typical range of permeability values for pervious concrete was between 2 mm/s and 12 mm/s.
To show the correlation among voids content and water permeability obtained from the results of the study, one of the most commonly used analytical models i. e., exponential regression method was used. The correlation among the water permeability and void content is illustrated in Fig. 7. It is fairly obvious that a very strong relationship exists among them. The coefficient of determination (R2) presenting an overall change in the dependent variables is also accounted for the regression equation, which was 0.99 as determined from Eq. (5).
K ¼ 0:0568e0:1992V
(5)
where, K is water permeability coefficient (mm/s) and V is void content (%). 4.4. Compressive strength The compressive strength of pervious concrete mixtures incorporating POFA is illustrated in Fig. 8. As the POFA content of mixtures increased, the compressive strength of mixtures decreased at 7 d and 28 d of curing. The compressive strength of PPC10, PPC20, PPC30 and PPC40 pervious concrete mixtures decreased by 9%, 20%, 30% and 49% respectively, compared to the CPC at 28 d of curing
16
Water permeability (mm/s)
14 12 10 8 6 4 2 0 CPC
PPC10
PPC20 Mixture
PPC30
Fig. 6. Water permeability of pervious concrete mixtures.
PPC40
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16
7 days
1481
28 days
Compressive strength (MPa)
14 12 10 8 6 4 2 0 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 8. Compressive strength of pervious concrete specimens at 7 d and 28 d.
time. This might be due to the delay in hydration and slow pozzolanic reaction of POFA, which prevented the increase in compressive strength. The reduction in compressive strength of the mixtures incorporating POFA is attributed to the spongy structure of POFA particles, which leads to more water absorption, increasing void content and decreasing compressive strength of pervious concrete samples. The results obtained in this study showed that obtained compressive strengths of pervious concrete containing POFA were within the acceptable range, as reported by ACI for strength of pervious concrete (2e28 MPa) (Tennis et al., 2004). The compressive strength value of the pervious concrete mixture containing up to 20% of POFA was almost comparable to the value of the CPC mixture. The failure mode of pervious concrete mixture containing 20% POFA was almost the same as that of mixture without any POFA as illustrated in Fig. 9. A linear correlation among compressive strength and void content of the pervious concrete mixtures can be deduced from the results (Fig. 10). The strong correlation among the compressive strength and void content can be observed. The R2 value was 0.97 for Eq. (6), signifying high certainty for the correlation.
4.5. Tensile strength From Fig. 11, it can be seen that the value of tensile strength test of all pervious concrete samples. The range of tensile strength of all samples were between 1.64 MPa and 2.47 MPa. As shown in the figure, tensile strength decreased as POFA contents increased. This trend was similar to that of compressive strength as well. The replacement of cement with 10, 20, 30 and 40% of POFA decreased the tensile strength by 1%, 18%, 22% and 34%, respectively compared with pervious concrete without any POFA (CPC). This could be due to the delay in hydration and slow pozzolanic reaction of POFA, which prevented the increase in tensile strength. These results indicated that all of the strength parameters for pervious concrete mixtures incorporating POFA are within the typical ranges for pervious concrete with OPC alone (1e3 MPa) (Tennis et al., 2004). From Fig. 12, it can be seen that a strong relationship between the compressive and tensile strengths values of pervious concrete mixtures containing POFA. A linear regression method was applied to correlate the experimental results as in Eq. (7), which has a R2 value of 0.95 for all samples.
Ft ¼ 0:128 Fc þ 0:681 Fc ¼ 1:6481 V þ 52:722 where, Fc is compressive strength and V is void content (%).
(6)
(7)
where, Ft is tensile strength (MPa) and Fc is compressive strength (MPa). The tensile strength values of the pervious concrete mixture containing up to 20% of POFA were almost comparable to the value of the CPC mixture. It was also observed that failure mode of pervious concrete mixture containing 20% POFA (PPC20) was almost similar to the mixture without any POFA (CPC) in tension, as shown in Fig. 13. 4.6. Skid resistance
Fig. 9. Failure modes of pervious concrete specimens in compression.
The skid resistance (British Pendulum Number or BPN) of the pervious concrete mixtures for both dry and wet conditions is presented in Fig. 14. The error bars for the skid resistance measurements indicated one standard deviation for the BPN of four swings, which were made on the surface of each pervious concrete specimen. As illustrated in Fig. 14, the skid resistance values of specimens containing POFA was comparable to value of CPC. The effect of POFA
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16
Compressive strength (MPa)
14 12 10
Fc = -1.6481×V + 52.722
8
R² = 0.969
6 4 2 0 20
21
22
23
24
25
26
27
28
Void content (%) Fig. 10. Correlation among compressive strength and void content.
3
Tensil strength (MPa)
2.5 2 1.5 1 0.5 0 CPC
PPC10
PPC20 Mixture
PPC30
PPC40
Fig. 11. Tensile strength of pervious concrete mixtures.
Fig. 12. Correlation among compressive and tensile strengths.
Fig. 13. Failure modes of pervious concrete specimens containing 0% and 20% POFA in tension.
E. Khankhaje et al. / Journal of Cleaner Production 172 (2018) 1476e1485
120
Dry
1483
wet
Skid resistance (BPN)
100 80 60 40 20 0 CPC
PPC10
PPC20
PPC30
PPC40
Mixture Fig. 14. Skid resistance of pervious concrete mixtures.
on the skid resistance of the pervious concrete mixtures was not notable. The BPN in wet conditions for PPC10, PPC20, PPC30 and PPC40 were 71, 70.5, 69.7 and 68.7 respectively, which were almost similar to that of CPC (71.5). Bonicelli et al. (2015) found comparable range of BPN for pervious concrete mixtures (60e75). Increasing POFA content in pervious concrete mixture caused skid resistance to decrease slightly. Ralph Haas et al. (1994) reported that both the microtexture of a pavement's surface affected skid resistance. This phenomenon can be explained by the smoother surface of pervious concrete mixture containing POFA than the mixture without any POFA (CPC). As such, the high skid resistance of the PPC mixtures might be due to the finer particles of POFA than cement, which decreased the surface friction of the PPC specimens.
slightly reduced with increase in revolutions. It is possible that by increasing the revolutions, the shape of samples became more and more spherical (Fig. 16). It can be noted that 29e48% of the pervious concrete mixture weight was lost after 500 revolutions. The weight loss for PPC10, PPC20, PPC30 and PPC40 were 32, 35, 41 and 48% respectively, when compared to that of CPC (29%), after 500 revolutions. By increasing POFA the weight loss of specimens increased slightly which could be due to lower strength of the pervious concrete mixtures incorporating POFA compared with mixture without POFA (CPC). Wu et al. (2011) reported almost similar results. They found that 20% of the pervious concrete specimen weight was lost after 300 revolutions. 4.8. Heavy metal leachability
4.7. Abrasion resistance To monitor the trend of abrasion mass loss, the samples were weighed after each 100 revolutions till 500 revolutions were achieved. The mass loss variation rate of all pervious concrete specimens is presented in Fig. 15. The mass loss of the specimens increased with increasing revolutions. The mass loss rate was
CPC
PPC10
The leachability of waste materials is essential and a significant factor in assessing the environmental impact. The heavy metals leaching of the crushed pervious concrete incorporating 40% of POFA are presented in Table 3. According to the results, all dissolved concentrations of heavy metals for pervious concrete mixture containing 40% POFA used in this study, were minimal than that of
PPC20
PPC30
PPC40
60
Weight loss (%)
50 40 30 20 10 0 0
100
200
300
Revelutions Fig. 15. Abrasion resistance of pervious concrete mixtures.
400
500
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minimal effect on the skid and abrasion resistance of pervious concrete mixtures. Due to the water permeability, the strength of pervious concrete containing POFA was only 20 MPa. Heavy metals leaching concentrations from pervious concrete containing POFA were extremely lower than that of the regulation. From the environmental point of view, POFA is safe to be used in the field. References
Fig. 16. Specimen containing 20% POFA in L.A abrasion test at various revolutions.
Table 3 Heavy metal leachability of crushed pervious concrete containing 40% POFA (mg/L). Heavy metals
Cr
Zn
Cd
Pb
Ni
Cu
PPC40 Standard Limitation SW-846 (2004)
0.013 5
0.121 250
0.001 1
0.003 5
0.010 20
0.011 25
the required regulations, thus qualifying it for recycling purposes. Although the hardened mixture was crushed into size of smaller than 9 mm, the values of heavy metals leaching concentrations were within the acceptable range. Hardened pervious concrete leaching in situ is a slowly mitigating process and only limited grains are smaller than 9 mm in comparison with the experimental condition. Therefore, the heavy metals immobilizing of crushed pervious concrete containing POFA might be more reliable in the field environment. 5. Conclusions In this study, 10e40% of OPC was substituted with POFA by mass in pervious concrete mixture. The fresh and hardened characteristics of pervious concrete containing POFA were evaluated. The effect of 20% POFA replacement up to was minimal in terms of void content and permeability of the pervious concrete mixtures. By increasing POFA up to 40% the void content and permeability increased. 10%e20% of cement replacement with POFA was determined as optimum substitution range for compressive and tensile strengths of pervious concrete. By increasing POFA from 30% to 40%, compressive and tensile strengths deceased. They satisfied the typical range for compressive strength (2e28 MPa) of pervious concrete as described in ACI. It is recommended for use in general bicycle ways, sidewalks, and landscaping. Strong correlations were found among different hardened properties of pervious concrete mixtures. Density, permeability and compressive strength can be predicted from the void content values. The compressive strength of pervious concrete mixture can be used to predict the tensile strength of pervious concrete mixture. Addition of POFA had a
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