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Environmental impact and quality assessment of using eggshell powder incorporated in lightweight foamed concrete
Construction and Building Materials 244 (2020) 118341
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Environmental impact and quality assessment of using eggshell powder incorporated in lightweight foamed concrete Hock Yong Tiong, Siong Kang Lim ⇑, Yee Ling Lee, Chuan Fang Ong, Ming Kun Yew Lee Kong Chian Faculty of Engineering & Science, Universiti Tunku Abdul Rahman, Malaysia
h i g h l i g h t s Five LFC mixtures with ESP as cement replacement material were prepared. ESP improve ISAT, sorptivity, water absorption, compressive strength, and UPV. Optimal ESP replacement level in LFC is 7.5% for mentioned properties. ESP replace 10% OPC in LFC reduce 6.6% to 9.9% of certain environmental loads.
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Article history: Received 1 September 2019 Received in revised form 14 January 2020 Accepted 2 February 2020
Keywords: Lightweight foamed concrete Eggshell powder Partial cement replacement material Quality performance Life cycle assessment
a b s t r a c t This paper is aimed to investigate the effects of eggshell powder (ESP), as partial replacement material of cement, on quality performance of lightweight foamed concrete (LFC) with density of 1300 kg/m3 in terms of initial surface absorption, sorptivity, water absorption, ultrasonic pulse velocity, and compressive strength; and meanwhile evaluate environmental impact of said replacement by performing life cycle analysis (LCA). Different eggshell powder lightweight foamed concrete were developed by replacing 0%, 2.5%, 5%, 7.5%, and 10% of cement with eggshell powder. A water to cement ratio of 0.58 was adopted to study the engineering properties of the eggshell powder lightweight foamed concrete for various ages of 7, 28 and 90 days. The laboratory results show that the incorporation of eggshell powder has decrease initial surface absorption, sorptivity, and water absorption of the lightweight foamed concrete. Besides, incorporation of eggshell powder has increase compressive strength and ultrasonic pulse velocity (UPV) of the lightweight foamed concrete as well, and the optimal replacement level is found at 7.5% based on compressive strength results. Moreover, the life cycle assessment result shows reductions of 6.6% to 9.9% in various environmental loads and impacts such as climate change, acidification, fossil fuel, eutrophication, photochemical oxidation, and ozone layer depletion. Ó 2020 Elsevier Ltd. All rights reserved.
1. Introduction Lightweight foamed concrete (LFC) is a mixture of ordinary Portland cement (OPC), fine aggregate, water, and foam, which has a pore structure that caused by artificial air voids. The foaming agent is applied and entrained into cement mortar in order to create artificial air bubbles, resulting in lightweight concrete as compared to normal concrete [1]. Lightweight concrete is a versatile material that has a concrete density range between 300 kg/m3 and 1850 kg/m3 [2]. The lightweight foamed concrete also known as aerated concrete due to its versatilities and lightness, has ⇑ Corresponding author. E-mail addresses: [email protected] (H.Y. Tiong), [email protected] (S.K. Lim), [email protected] (Y.L. Lee), [email protected] (C.F. Ong), yewmk@ utar.edu.my (M.K. Yew). https://doi.org/10.1016/j.conbuildmat.2020.118341 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved.
brought an alternative application of economic building material for building technology [3,4]. Other than lower density and lighter weight, LFC provides better fire resistance, thermal and sound insulations, higher workability, and lower dead load; and easier to be produced as compared to that of normal weight concrete [1,5]. Lightweight foamed concrete with a density of 1200– 1600 kg/m3 is used in precast panels [6]. Based on the statistics from Malaysia Veterinary Department (DVS) [7], as shown in Fig. 1, 8979.8 million eggs were consumed in 2011 and this figure had been increased to 12235.3 million eggs in 2017 in Malaysia, and it is expected to increase in coming years [7]. A local news report had shown that Malaysian consume 20 million eggs daily which makes it becomes the largest egg consumption country in the world [8]. As cited by Shuhadah [9], around 150,000 tons of eggshell (ES) waste is disposed in landfills [10]. It is logical to deduce that the eggshell waste increases
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Fig. 1. Poultry eggs consumption in Malaysia from year 2011 to 2017 [7].
significantly as the populations grow. Disposal of ES is a problem as it can create an undesirable smell and some allergies when kept a longer time in the trash. This will result in comprising ecological issues that might demand proper treatment [11]. In certain cases, companies pay up to 100,000 dollars to dispose of eggshell waste in landfills and consequently the landfills reaching its capacity [12]. Eggshell waste is involved in the development of innovative technology in various industries. Eggshell waste is used as a solid catalyst for the production of biodiesel [13] and stabilizer for expansive clay [14]. Eggshell ash also used as an accelerator for cement-bound materials in order to perform its effect on the strength properties of cement-stabilized lateritic soil [15]. Eggshell consists of several mutually growing layers of CaCO3 that form 95% of the shell [16]. The eggshell waste powder with the porous irregular particle size of 2 to 900 mm that rich in calcite (CaCO3) can be used for wall tile production [17]. Therefore, the production of lightweight foamed concrete incorporated with eggshell waste shows its potential to reduce the huge problem of eggshell waste disposal, yet improving in its ecological manner while maintaining its significant properties toward creating sustainable building materials. Besides, the manufacturing of OPC has a high demand on energy and generates heat and greenhouse gasses. The production process of the cement including mining of raw materials, crushing or milling of into fine powder and heating to the sintering temperature of over 1400 °C [18]. According to the Global Cement and Concrete Association (GCCA) [19] Sustainability Guidelines, cement production makes up about 5% of annual global carbon emissions. Thus, eggshell powder (ESP) as cement replacement material is a promising alternative in concrete production which able to reduce the environmental impacts from the normal concrete production. Nevertheless, there is a limited study that revealed the potential environmental benefits of LFC incorporated with ESP. The quality performance of lightweight foamed concrete is much significant nowadays in order to maintain its durability. Non-durable concrete requires repair, replace, and destruct which results in undesirable high cost and unsustainable development. Quality of lightweight foamed concrete can be evaluated physically or chemically. Adverse physical effects on concrete include surface wear, cracking, exposure to extreme temperature, etc.; deleterious chemical effects include leaching, sulphate attack, alkali-aggregate reaction, chloride ion attack, etc [20]. Water is an agent of deterioration for porous material whereby the internal moisture movements are known to cause disruptive volume changes [20]. Therefore, water is used as an agent for quality evaluation of lightweight foamed concrete which are initial surface absorption test, sorptivity, and water absorption test as mentioned in experimental work. Generally, the quality of concrete with respect to durability is related to its characteristics of pore system which measured in terms of permeability [6,21]. The more porous the concrete, the more vulnerable the material is to degradation mechanism caused by penetrating substances [21]. The research shows that the result
from the water absorption test shows an approximate total concrete pore volume, but the concrete permeability cannot be indicated [21]. The permeability is referred to as diffusion or flow of liquid in concrete and penetrate into concrete [2]. Concrete with low porosity and permeability is normally better to resist undesirable phenomena. However, permeability is not a simple function of porosity. It is possible for two porous concretes to have the same porosity but different permeabilities. The segmenting of capillaries influences largely on concrete permeability [2]. The water absorption test is intended as a durability quality check and to predict concrete durability [22]. Furthermore, porosity has been used as a durability performance predictor of the concrete [23]. Sorptivity is the water ingress of unsaturated porous concrete due to surface tension dominated by capillary suction and is a function of the pore structure of the porous concrete [24]. Sorptivity test is necessary in order to determine the rate of water absorption of capillary suction since the driving force for the water absorption test is also a response to pressure [25]. Based on the study, permeability and sorptivity of the pore structure of concrete are two different physical characteristics [26]. Thus, permeability and sorptivity of concrete must be evaluated by a different method. A relationship between strength and sorptivity of lightweight concrete indicated that the sorptivity reduced significantly when the strength that is indicating a denser microstructure increased. [26]. The pore structure of cementitious material is significantly affecting properties that are more dependent on material porosity and permeability such as strength and durability [1]. Also, porosity is a primary influencing factor of the strength of the cement paste [2]. Despite this, total void (porosity) determination might not be sufficient as the strength and durability of concrete might be affected by other properties of the voids such as shape, size, and distribution in concrete [27,28]. Therefore, Ramamurthy et al. [1] mentioned that the importance of air-void influencing the strength of foamed concrete and concluded that the strength of foamed concrete is higher when void has a narrower size distribution. Many researchers have studied the relationship between strength and pulse velocity of concrete. The pulse velocity cannot be used as a general indicator of compressive strength because of the factor of its aggregate [2]. However, the strength of concrete has a direct relation with the pulse velocity for well compacted concrete and for given aggregate type [22]. The relationship between ultrasonic pulse velocity (UPV) and compressive strength was found exponential for mineral admixture mortars, both UPV and compressive strength were low at early stages but increases as the curing period increases [29]. The inclusion of ferrochrome ash and lime as partial cement replacement has confirmed a strong relationship between compressive strength, water permeability, and UPV whereby low water permeability gives increment of both compressive strength and UPV [30]. Previous research regarding to the incorporation of ESP as cement replacement material in normal weight concrete had shown positive results in mechanical properties as well as water absorption and sorptivity or either their relationship [31]. A similar study also shows positive result in compressive strength while incorporating eggshell as partial cement replacement [32]. Therefore, this research is aimed to further study and assess environmental impacts and quality performance of incorporating ESP as partial cement replacement material in LFC namely environmental load reduction, absorption properties, UPV, and compressive strength. For the sake of comparison of environmental impacts between different OPC replacement foamed concretes, cradle-togate life cycle assessments have been conducted based on Ecoinvent database and CML baseline method (CML is the abbreviation for the name of an institute of the Faculty of Science of Leiden University in Dutch ‘Centrum voor Milieuwetenschappen in Leiden’).
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2. Experimental program 2.1. Materials Raw materials which originate locally such as ordinary Portland cement (OPC), fine sand, eggshell powder (ESP), foam, and water, were used to prepare lightweight foamed concrete specimen that has a density of 1300 ± 50 kg/m3. The 52.5 N local branded OPC complying with Type I Portland Cement in accordance with ASTM C 150 [33] and MS EN 197-1 [34] was used in this study. Cement was sieved at a size of 300 lm to ensure the removal of hydrated cement lumps. The cement replacement material, eggshell (ES) waste which obtained from the local commercial area such as bakeries, was being cleaned and dried under the hot sun to remove its surface moisture. The ES was then being crushed, ground, and sieved to obtain particle with size less than 63 lm. In order to avoid depletion of lime content, the ES shall be ground within 2 days after obtained from the sources [35]. The chemical compositions of ESP are presented in Table 1 [17]. Fine sand complying with ASTM C 778-02 [36], BS EN 12,620 [37] and BS 882 [38] was used in this study, and it was subjected to 24 h oven drying at 105 °C to remove the moisture content and then sieved to obtain sand with particle size not more than 600 mm. Normal tap water and synthetic foaming agent, which is a special blend of polyoxyethylene alkyether sulfate, were used during the production of LFC. 2.2. Mix proportions In this study, water to cement ratio (w/c) was selected and maintained at 0.58 ± 0.02. Stable foam with a density of 45 ± 5 kg/m3 was produced by the dry pre-foaming method [39]. The foam must be stable in order to resist the pressure of the mortar and hold until a strong skeleton of cement paste is built up
Table 1 Chemical composition of eggshell powder. Chemical Constituents (%)
Eggshell Powder [17]
Eggshell Powder*
Calcium Oxide, CaO Calcium Carbonate, CaCO3 Silicon Dioxide, SiO2 Aluminium Oxide, Al2O3 Ferric Oxide, Fe2O3 Magnesium Oxide, MgO Sulphur Oxide, SO3 Sodium Oxide, Na2O Potassium Oxide, K2O Phosphorus Pentoxide, P2O5 Strontium Oxide, SrO Nickel Oxide, NiO Chlorine, Cl
50.70 – 0.09 0.03 0.02 0.01 0.57 0.19 – 0.24 0.13 0.001 0.219
– 99.19 – 0.207 0.093 – 0.467 – 0.029 – – – –
*Chemical constituents result obtained from X-ray fluorescence (XRF) analysis.
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around the foam or air void [40]. The foaming agent was diluted with water in the foam generator at a ratio of 1:30 by volume. The foam was generated at a pressure of 0.5 MPa and immediately added into the mortar by the amount of 1.6% to 1.9% of dry mix weight. For the LFC incorporated with ESP, the percentage of ESP used as cement replacement material ranging from 2.5% to 10.0% at an interval of 2.5%. A summary of the mixtures and experiment are shown in Table 2. 2.3. Specimens preparation First, the raw materials namely cement, ESP, sand, and water were mixed to obtain base mix or mortar. Then, the dry foam, which generated by the foam generator, was immediately mixed with the mortar thoroughly. The fresh lightweight foamed concrete was controlled at the density of 1300 ± 50 kg/m3 and then poured into the respective mould with a cubical size of 100 mm and cylindrical size of 100 mm diameter and 200 mm height. The specimens were demoulded after 24 h and then water cured under temperature of 25–30 °C until testing the ages of 7, 28, and 90 days respectively. Prior to testing, hardened 100 mm diameter cylindrical specimens were cut into three small cylindrical specimens with a height of 50 mm for the sorptivity test. For every mixture and testing age, 3 specimens were prepared, in which, water absorption, compressive strength, and UPV test share the same specimen. Therefore, total 90 number of 100 mm cubical specimens prepared for 5 mixtures, 3 testing ages, 2 testing groups, and 3 specimens per group; and 15 number of 100 mm diameter and 50 mm height cut cylindrical specimens prepared for 5 mixtures, 1 testing age, and 3 specimens per testing age. 2.4. Testing methods 2.4.1. Initial surface absorption test (ISAT) Initial surface absorption test (ISAT) was conducted as prescribed in BS 1881- Part 208 [41]. This test was conducted to determine the rate of flow of water into an oven-dried and flat concrete surface through both capillary and non-capillary pores, by the circumstances where a water pressure head of 200 mm ± 20 mm and constant temperature are applied. Time taken for water to flow in capillary tubes at a fixed distance was recorded at 10, 30, 60, and 120 min from the time the concrete surface exposed to water. 2.4.2. Sorptivity test Sorptivity test was conducted by referring to ASTM C 1585 [42] and BS EN 772-11 [43]. This test was conducted to determine the flow of water into an oven-dried and flat cut concrete surface by capillary action, where the 100 mm diameter and 50 mm height cut specimens are immersed in water at depth of 1–3 mm to suck the water. The mass of specimens was measured at 1, 5, 10, 15, 30, 60, 90, 120, and 150 min after the concrete surface exposed to water, then the calculation of sorptivity was performed based on ASTM C 1585.
Table 2 Summary of experimental work details. Mix details
c/s
ES/c
w/c
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
1 1 1 1 1
0 0.025 0.050 0.075 0.100
0.58 0.58 0.58 0.58 0.58
± ± ± ± ±
0.02 0.02 0.02 0.02 0.02
Preformed stable foam*
Curing condition
Investigated properties
1.6 to 1.9%
Totally immersed in water at temperature in the range of 25–30 °C
ISAT, compressive strength, and UPV at the ages of 7, 28, and 90 days; Sorptivity and water absorption, at the age of 90 days
Note: c/s = cement to sand ratio, cement included OPC and ES, ES/c = eggshell powder to cement ratio, w/c = water to cement ratio, LFC = lightweight foamed concrete, ES = eggshell. * Percentage of stable foam used was based on the weight of total dry mix which consists of cement, eggshell powder and sand.
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2.4.3. Water absorption test Water absorption test was carried out as referred to BS 1881122 [44]. The surface-dry saturated mass and oven-dried mass of 100 mm cubical specimen was measured after 1 h of air-dried after water curing and after 24 h of oven-drying at the temperature of 105 ± 5 °C respectively to obtain saturated surface dry density (SSDD), and oven-dried density (ODD). Then, water absorption was calculated by (SSDD-ODD)/ODD 100%. This is to test the total amount of water that can be absorbed by the LFC after immersed in water throughout the entire curing period.
Fig. 2 shows the boundary condition of ESP foamed concrete from the cradle-to-gate system, where the activities start from raw material extraction and end with the production of concrete at the mixing plant. The life cycle assessment considered the stages of: (1) extraction of all raw materials of foamed concrete, (2) transportation of raw concrete to mixing plant, and lastly (3) concrete production at the plant. 3. Results and discussion 3.1. Initial surface absorption test
2.4.4. Ultrasonic pulse velocity test (UPV) UPV was measured by a Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT 7) that measures the propagation time of ultrasonic waves (54 kHz) through an oven-dried cubical specimen with accuracy up to 0.1 ls [2]. In accordance with BS EN 12504-4 [45], the direct transmission was adopted by positioning the transmitter and receiver in the middle of each opposing surface of the specimen [6,46,47]. This is the arrangement that gives the most reliable results as the signal strength is the highest [22]. Prior to testing, the apparatus was set up and calibrated to 25.2 ls. This test was performed to check the quality of the LFC. 2.4.5. Compressive strength Compressive strength was determined by using compression test machine. 100 mm oven-dried cubical specimens were used for this test. The loading rate of 0.02 mm/s was applied as referring to BS EN 12390-3 [48].
Fig. 3 shows the effect of the incorporation of ESP on initial surface absorption of LFC at the age of 90 days. Generally, the flow or initial surface absorption of all specimens were decreased with the increased testing time due to the saturation of LFC. A vital observation shows that the incorporation of ESP has resulted in decreased flow or initial surface absorption as compared to the control mix. The higher the percentage of ESP incorporated, the lower the flow was observed. This might because the capillary pore has been interrupted and segmented by the ES particles at which the passage was only partly connected [51,52]. Fig. 4 shows the effect of the incorporation of ESP on 120 min initial surface absorption of the LFC at the ages of 7, 28, and 90 days. The effect of the curing period shows an obvious trend by which the flow or initial surface absorption was decreased along the curing period. The incorporation of ESP that acts as an inert filler in LFC resulted in lower flow or initial surface absorption as compared to that of the control mix.
2.5. Life cycle assessment 3.2. Sorptivity One of the main concerns on concrete production is the environmental impact produced throughout its upstream. LFC is expected to be more environmentally sound by partial replacement of OPC with ESP. A life cycle assessment (LCA) is conducted for the investigation, it follows the guidelines of ISO 14040 [49] and ISO 14044 [50] standards, these standards have been used to capture the environmental impacts of the boundary system under analysis. Since the ESP concrete is yet to be commercialized, some of the environmental impact inventories only assume inputs at laboratory scale. The functional unit of 1 kg of concrete produced is adopted in this study.
Manufacture of cement
Manufacture of aggregates - Gravel - Sand
Manufacture of Foaming Agent
Transportation
Transportation
Transportation
Fig. 5 shows the effect of the incorporation of ESP in LFC on its sorptivity at the age of 90 days. The absorptions of all specimens were increased throughout the testing time. The absorptions of all specimens were directly proportional to the square root of time which gave R2 value nearly to unity as shown in Fig. 5. ESP in LFC has significantly decreased its sorptivity as compared to that of the control mix. The higher the incorporation of eggshell in LFC, the lower its sorptivity coefficient as shown in Fig. 6. However, incorporation of 10% eggshell in LFC has an inverse effect which resulted in a higher sorptivity coefficient than LFC-ES2.5, LFC-ES5.0 and
Transportation
Tap Water
Washing Eggshell Powder
Concrete Mixing Plant
Grinding
Output: Concrete with different eggshell powder replacement
Sieving
Fig. 2. System boundary of LFC with eggshell powder replacement.
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Flow, f (ml/m²s) per 1000 kg/m³
3.5 3 2.5
LFC-CTR
2
LFC-ES2.5 1.5
LFC-ES5.0 LFC-ES7.5
1
LFC-ES10.0 0.5 0 10
30
60
120
Test time (min) Fig. 3. Effect of incorporation of eggshell powder in LFC on its initial surface absorption through the testing time of 10, 30, 60 and 120 min at the age of 90 days.
Flow, f (ml/m²s) per 1000 kg/m³
2.5
2
1.5
7-Day 1
28-Day 90-Day
0.5
0 LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
LFC-ES10.0
Type of Specimens Fig. 4. Effect of incorporation of eggshell powder in LFC on its initial surface absorption during the testing time of 120 min at the ages of 7, 28 and 90 days.
5
y = 0.0437x + 0.3507 R² = 0.9993 (LFC-CTR)
4.5
Absorption, I (mm)
4
y = 0.0271x + 0.6051 R² = 0.9977 (LFC-ES2.5)
3.5
y = 0.0246x + 0.3421 R² = 0.9983 (LFC-ES5.0)
3 2.5
y = 0.0228x + 0.1537 R² = 0.9907 (LFC-ES7.5)
2
y = 0.0304x + 0.1973 R² = 0.9972 (LFC-ES10.0)
1.5 1 0.5 0 0
20
40
60
Square root of time, √t
80
100
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
(s0.5)
Fig. 5. Effect of incorporation of eggshell powder in LFC on its sorptivity at the age of 90 days.
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30
0.05 0.045 0.04 0.035
20
0.03 15
0.025 0.02
10
0.015
Sorptivity (mm/s0.5)
Water Absorption (%)
25
0.01
5
0.005 0
LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
Type of Specimens
LFC-ES10.0
0
Water Absorption Sorptivity
Fig. 6. Effect of incorporation of eggshell powder in LFC on its water absorption and sorptivity at the age of 90 days.
LFC-ES7.5. It might because the cement had been diluted, in which lesser water undergoes hydration process with an increment of replacement level and more free water to form interconnected pores, and when replacement level exceeds a certain value, the further favourable effect of ESP is insufficient to compensate the adverse effect of the said cement dilution effect. In overall, LFCES7.5 has shown the lowest sorptivity coefficient among all specimens. 3.3. Water absorption Fig. 6 shows the effect of the incorporation of ESP on water absorption of the LFC at the age of 90 days. The incorporation of ESP in LFC has decreased the water absorption as compared to that of the control mix. A similar study opined that the incorporation of ESP in normal weight concrete has resulted in lower water absorption [31]. In this study, increment percentage of ESP had resulted in decreased water absorption, however LFC-ES10.0 shows higher water absorption than that of LFC-ES5.0 and LFC-ES7.5 and it might due to cement dilution effect as well. Overall, LFC-ES7.5 has the lowest water absorption. As a summary for ISAT, sorptivity, and water absorption test, ISAT represents initial rate of water penetration underwater pressure head and is guided by interconnected capillary and noncapillary pores, and also affected by shape and size of passage; sorptivity represents ability of concrete to absorb water by capillary action and guide by interconnected capillary pores; and water absorption represents total amount of water absorbed by concrete during curing period, is also guided by interconnected capillary and non-capillary pores. Incorporation of ESP as partial replacement material of cement can improve the mentioned properties, in which the properties improve with increased replacement level of up to 7.5%. A further replacement will start to deteriorate said properties, and this might be caused by the cement dilution effect. 3.4. Compressive strength Fig. 7 shows the effect of incorporation of ESP as partial cement replacement material in LFC on its compressive strength at the ages of 7, 28, and 90 days. It is clearly shown that the performance of compressive strength increased throughout the curing periods. Generally, all specimens of ESP LFC showed higher performance index for all the curing periods as compared to the control mix.
A similar study also deduced that the incorporation of ESP as partial cement replacement in normal weight concrete has possessed higher compressive strength as compared to the control mix [31]. The researcher opined that the ESP has same behaviour as lime stone filler in strength properties. It has been reported that ESP is mostly made up of calcium carbonate. The calcium carbonate might act as an inert filler to increase the compressive strength of concrete [52]. Another possible reason is that the calcium carbonate reacts with alumina phases of cement and produces monocarboaluminates which result in an increment of strength [53]. From the results, LFC-ES7.5 has achieved the highest compressive strength among all LFC specimens. 3.4.1. Correlation between compressive strength and ultrasonic pulse velocity (UPV) The effect of incorporation of ESP on compressive strength and UPV of various types of LFC specimens at the ages of 7, 28, and 90 days are shown in Fig. 8. Both compressive strength and UPV were increased relatively as the percentage of incorporation of ESP increased. However, LFCES10.0 showed lower compressive strength and UPV as illustrated in Fig. 8. Overall, LFC-ES7.5 has achieved both the highest compressive strength and UPV among all LFC specimens. This may due to the reduction of porosity in LFC-ES7.5 which resulted in higher pulse velocity. The reduction of the porous structure of LFC-ES7.5 may due to the effect of ESP derived as calcium carbonate which acts as inert filler. Furthermore, Acharya and Patro [30] highlighted that the effect of inclusion of lime as partial cement replacement had shown the increment of both compressive strength and UPV. Fig. 9 shows the effect of incorporation of ESP on its correlation between compressive strength and UPV at curing ages of 7, 28, and 90 days. R2 values of respective LFC specimens are also shown in Fig. 9. It can be seen that the correlation between compressive strength and UPV was found slightly exponential to each other. Previous studies have shown the same result for correlation between compressive strength and UPV [22,29]. Both compressive strength and UPV for ESP LFC were relatively higher than that of the control mix. From the graph, LFC-ES7.5 has showed the highest compressive strength and UPV. Further increment of replacement level after exceeding 7.5% will deteriorate compressive strength and UPV, and it might also due to cement dilution effect as the LFC might become more porous and favourable effects of ESP is insufficient to compensate adverse effect of cement dilution.
7
4
4.44 4.66 5.08
5.03 5.40 4.86
4.44 4.56
5
3.75 3.72 4.16 4.31 3.30
Performance Index of Compressive Strength (MPa/1000 kg/m3)
6
5.58 5.36
H.Y. Tiong et al. / Construction and Building Materials 244 (2020) 118341
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
3
2
1
0
7-Day
28-Day Curing Period (Days)
90-Day
Fig. 7. Performance indexes of compressive strength for various types of specimens at the ages of 7, 28, and 90 days.
8
7
2.0
Compressive Strength, fc (MPa)
6
1.9
5 1.8 4 1.7 3 1.6
2
1.5
1
0
Ultrasonic Pulse Velocity, UPV (km/s) per 1000 kg/m3
2.1
1.4
LFC-CTR
LFC-ES2.5
LFC-ES5.0 LFC-ES7.5 Type of Specimens
LFC-ES10.0
7-Day fc
28-Day fc
90-Day fc
7-Day UPV
28-Day UPV
90-Day UPV
Fig. 8. Effect of incorporation of eggshell powder in LFC on its compressive strength and ultrasonic pulse velocity for various types of specimens at the ages of 7, 28, and 90 days.
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9
Compressive Strength, fc (MPa)
8
R² = 0.9504
7
R² = 0.9689 6
5
R² = 0.9969 R² = 0.8628
R² = 0.9961
4
3 1.80
1.85
1.90
1.95
2.00
2.05
Ultrasonic Pulse Velocity, UPV (km/s) per 1000 kg/m3 LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
LFC-ES10.0
Linear (LFC-CTR)
Linear (LFC-ES2.5)
Linear (LFC-ES5.0)
Linear (LFC-ES7.5)
Linear (LFC-ES10.0) Fig. 9. Correlation between compressive strength and ultrasonic pulse velocity for various types of specimens at the ages of 7, 28, and 90 days.
4. Environmental sustainability In regards to life cycle inventory, the inputs and outputs of raw materials of foamed concrete (OPC, fine and coarse aggregates, water, and foaming agent) and transportation are extracted from Ecoinvent 3.4 database. The cut-off system model is adopted in this study. The basic concept of the cut-off system model is the activity of the product is fully responsible for the waste produced, and the recyclable process of the waste product does not give credit to the activity. All transportation is assumed to be by road using diesel fuel. It is assumed that the transport for all raw materials to the concrete mixing plant for a round trip through the road is 100 km. For ESP, the activities start from the transportation of eggshells from poultry or shops to the laboratory, transportation distance is estimated at 10 km. Grinding machine and sieving machine with low voltage are used in the process of preparing ESP, 1.5 kWh of energy is used for grinding and sieving of 1 kg of
eggshell. Besides, 5 kg of water is estimated to be consumed for washing every 1 kg of ES. Drying of the eggshell is done by exposing and drying under local natural weathering. Thus, no input required. The energy usage in the concrete mixing plant is taken from Stripple [54]. The inputs and outputs of concrete mixing are assumed to be identical for both reference concrete and ESP concrete, and therefore all the mixes share the same quantity of environmental loadings from the mixing process. The impact assessment adopted CML baseline method created by the Centre of Environmental Sciences - Leiden University. Six categories of environmental impacts are considered in the analysis, including acidification, climate change, fossil fuel, photochemical oxidation, eutrophication, and ozone layer depletion. The results are tabulated in Table 3. In order to assess the impacts of OPC-ESP replacement, the four quantity ranges of partial OPC-ESP replacement are used to compare with the reference mix.
Table 3 Baseline CML method results for the production of 1 m3 of foamed concrete.
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
Acidification (kg SO2)
Climate change (kg CO2)
Fossil fuel (MJ)
Photochemical oxidation (kg ethylene)
Eutrophication (kg PO4)
Ozone layer depletion ( 10–5 kg CFC-11)
1.291 1.276 ( 1.5%) 1.250 ( 3.6%) 1.233 ( 4.9%) 1.187 ( 8.4%)
505.54 500.90 ( 0.9%) 487.50 ( 3.6%) 477.45 (5.60%) 455.27 (9.90%)
2183 2169 ( 0.6%) 2125 ( 2.7%) 2099 ( 3.8%) 2019 ( 7.5%)
0.0752 0.0734 ( 2.4%) 0.0724 ( 3.7%) 0.0719 ( 4.4%) 0.0701 ( 6.8%)
0.431 0.422 ( 2.1%) 0.416 ( 3.5%) 0.412 ( 4.4%) 0.401 ( 7.0%)
1.702 1.691 ( 0.6%) 1.660 ( 2.5%) 1.645 ( 3.3%) 1.589 ( 6.6%)
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The environmental loads of foamed concrete mainly decided by its OPC content. The magnitude of environmental loads of foamed concrete tends to reduce with the increase of ESP replacement. Among all the concrete ingredients, OPC is the major contributor for every category of environmental impacts since the cement production consumes a lot of energy and involves the combustion of fossil fuel that releases the pollutant to the air and water. Massive of CO2 is emitted from the calcination process that involved the burning of limestone into calcium oxide, and during the burning of fossil fuel for the heating of kiln [55]. At 10% ESP replacement, the reduction of environmental load can achieve as much as 9.9% in the category of climate change, and follow with 8.4% in acidification, 7.5% in fossil fuel, 7% in eutrophication, 6.8% in photochemical oxidation, and 6.6% in ozone layer depletion. In a nutshell, the results of LCA indicate the sustainable application of ESP as a partial replacement of OPC, and contribute to the reduction of environmental impacts in the production of foamed concrete.
5. Conclusion This study shows that the incorporation of eggshell powder that partially replaces cement in lightweight foamed concrete could enhance the quality performance of lightweight foamed concrete and reduce environmental impacts. However, the incorporation of different replacement percentage of eggshell powder has differently influenced the durability and strength properties. From this study, several conclusions can be drawn: 1. By incorporating eggshell powder into lightweight foamed concrete as a partial cement replacement material, initial surface absorption, sorptivity, and water absorption of lightweight foamed concrete have decreased. 2. Both ultrasonic pulse velocity and compressive strength of lightweight foamed concrete increased with the increment of eggshell powder replacement level. Compressive strength is exponential to ultrasonic pulse velocity. 3. The optimal replacement level of eggshell powder is found at 7.5% which gives the highest strength and quality performance of lightweight foamed concrete. 4. It is sustainable to apply eggshell powder to replace ordinary Portland cement at the replacement level of up to 7.5% in the production of lightweight foamed concrete to reduce environmental load.
CRediT authorship contribution statement Hock Yong Tiong: Conceptualization, Methodology, Writing original draft, Writing - review & editing. Siong Kang Lim: Conceptualization, Writing - original draft, Writing - review & editing, Supervision. Yee Ling Lee: Methodology, Investigation, Writing review & editing, Supervision. Chuan Fang Ong: Methodology, Investigation, Writing - original draft, Writing - review & editing. Ming Kun Yew: Resources, Writing - original draft.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Acknowledgement The efforts contributed by Mr. Lee Ren Siong on laboratory work and all supports provided by Universiti Tunku Abdul Rahman are highly appreciated.
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Environmental impact and quality assessment of using eggshell powder incorporated in lightweight foamed concrete Hock Yong Tiong, Siong Kang Lim ⇑, Yee Ling Lee, Chuan Fang Ong, Ming Kun Yew Lee Kong Chian Faculty of Engineering & Science, Universiti Tunku Abdul Rahman, Malaysia
h i g h l i g h t s Five LFC mixtures with ESP as cement replacement material were prepared. ESP improve ISAT, sorptivity, water absorption, compressive strength, and UPV. Optimal ESP replacement level in LFC is 7.5% for mentioned properties. ESP replace 10% OPC in LFC reduce 6.6% to 9.9% of certain environmental loads.
a r t i c l e
i n f o
Article history: Received 1 September 2019 Received in revised form 14 January 2020 Accepted 2 February 2020
Keywords: Lightweight foamed concrete Eggshell powder Partial cement replacement material Quality performance Life cycle assessment
a b s t r a c t This paper is aimed to investigate the effects of eggshell powder (ESP), as partial replacement material of cement, on quality performance of lightweight foamed concrete (LFC) with density of 1300 kg/m3 in terms of initial surface absorption, sorptivity, water absorption, ultrasonic pulse velocity, and compressive strength; and meanwhile evaluate environmental impact of said replacement by performing life cycle analysis (LCA). Different eggshell powder lightweight foamed concrete were developed by replacing 0%, 2.5%, 5%, 7.5%, and 10% of cement with eggshell powder. A water to cement ratio of 0.58 was adopted to study the engineering properties of the eggshell powder lightweight foamed concrete for various ages of 7, 28 and 90 days. The laboratory results show that the incorporation of eggshell powder has decrease initial surface absorption, sorptivity, and water absorption of the lightweight foamed concrete. Besides, incorporation of eggshell powder has increase compressive strength and ultrasonic pulse velocity (UPV) of the lightweight foamed concrete as well, and the optimal replacement level is found at 7.5% based on compressive strength results. Moreover, the life cycle assessment result shows reductions of 6.6% to 9.9% in various environmental loads and impacts such as climate change, acidification, fossil fuel, eutrophication, photochemical oxidation, and ozone layer depletion. Ó 2020 Elsevier Ltd. All rights reserved.
1. Introduction Lightweight foamed concrete (LFC) is a mixture of ordinary Portland cement (OPC), fine aggregate, water, and foam, which has a pore structure that caused by artificial air voids. The foaming agent is applied and entrained into cement mortar in order to create artificial air bubbles, resulting in lightweight concrete as compared to normal concrete [1]. Lightweight concrete is a versatile material that has a concrete density range between 300 kg/m3 and 1850 kg/m3 [2]. The lightweight foamed concrete also known as aerated concrete due to its versatilities and lightness, has ⇑ Corresponding author. E-mail addresses: [email protected] (H.Y. Tiong), [email protected] (S.K. Lim), [email protected] (Y.L. Lee), [email protected] (C.F. Ong), yewmk@ utar.edu.my (M.K. Yew). https://doi.org/10.1016/j.conbuildmat.2020.118341 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved.
brought an alternative application of economic building material for building technology [3,4]. Other than lower density and lighter weight, LFC provides better fire resistance, thermal and sound insulations, higher workability, and lower dead load; and easier to be produced as compared to that of normal weight concrete [1,5]. Lightweight foamed concrete with a density of 1200– 1600 kg/m3 is used in precast panels [6]. Based on the statistics from Malaysia Veterinary Department (DVS) [7], as shown in Fig. 1, 8979.8 million eggs were consumed in 2011 and this figure had been increased to 12235.3 million eggs in 2017 in Malaysia, and it is expected to increase in coming years [7]. A local news report had shown that Malaysian consume 20 million eggs daily which makes it becomes the largest egg consumption country in the world [8]. As cited by Shuhadah [9], around 150,000 tons of eggshell (ES) waste is disposed in landfills [10]. It is logical to deduce that the eggshell waste increases
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Fig. 1. Poultry eggs consumption in Malaysia from year 2011 to 2017 [7].
significantly as the populations grow. Disposal of ES is a problem as it can create an undesirable smell and some allergies when kept a longer time in the trash. This will result in comprising ecological issues that might demand proper treatment [11]. In certain cases, companies pay up to 100,000 dollars to dispose of eggshell waste in landfills and consequently the landfills reaching its capacity [12]. Eggshell waste is involved in the development of innovative technology in various industries. Eggshell waste is used as a solid catalyst for the production of biodiesel [13] and stabilizer for expansive clay [14]. Eggshell ash also used as an accelerator for cement-bound materials in order to perform its effect on the strength properties of cement-stabilized lateritic soil [15]. Eggshell consists of several mutually growing layers of CaCO3 that form 95% of the shell [16]. The eggshell waste powder with the porous irregular particle size of 2 to 900 mm that rich in calcite (CaCO3) can be used for wall tile production [17]. Therefore, the production of lightweight foamed concrete incorporated with eggshell waste shows its potential to reduce the huge problem of eggshell waste disposal, yet improving in its ecological manner while maintaining its significant properties toward creating sustainable building materials. Besides, the manufacturing of OPC has a high demand on energy and generates heat and greenhouse gasses. The production process of the cement including mining of raw materials, crushing or milling of into fine powder and heating to the sintering temperature of over 1400 °C [18]. According to the Global Cement and Concrete Association (GCCA) [19] Sustainability Guidelines, cement production makes up about 5% of annual global carbon emissions. Thus, eggshell powder (ESP) as cement replacement material is a promising alternative in concrete production which able to reduce the environmental impacts from the normal concrete production. Nevertheless, there is a limited study that revealed the potential environmental benefits of LFC incorporated with ESP. The quality performance of lightweight foamed concrete is much significant nowadays in order to maintain its durability. Non-durable concrete requires repair, replace, and destruct which results in undesirable high cost and unsustainable development. Quality of lightweight foamed concrete can be evaluated physically or chemically. Adverse physical effects on concrete include surface wear, cracking, exposure to extreme temperature, etc.; deleterious chemical effects include leaching, sulphate attack, alkali-aggregate reaction, chloride ion attack, etc [20]. Water is an agent of deterioration for porous material whereby the internal moisture movements are known to cause disruptive volume changes [20]. Therefore, water is used as an agent for quality evaluation of lightweight foamed concrete which are initial surface absorption test, sorptivity, and water absorption test as mentioned in experimental work. Generally, the quality of concrete with respect to durability is related to its characteristics of pore system which measured in terms of permeability [6,21]. The more porous the concrete, the more vulnerable the material is to degradation mechanism caused by penetrating substances [21]. The research shows that the result
from the water absorption test shows an approximate total concrete pore volume, but the concrete permeability cannot be indicated [21]. The permeability is referred to as diffusion or flow of liquid in concrete and penetrate into concrete [2]. Concrete with low porosity and permeability is normally better to resist undesirable phenomena. However, permeability is not a simple function of porosity. It is possible for two porous concretes to have the same porosity but different permeabilities. The segmenting of capillaries influences largely on concrete permeability [2]. The water absorption test is intended as a durability quality check and to predict concrete durability [22]. Furthermore, porosity has been used as a durability performance predictor of the concrete [23]. Sorptivity is the water ingress of unsaturated porous concrete due to surface tension dominated by capillary suction and is a function of the pore structure of the porous concrete [24]. Sorptivity test is necessary in order to determine the rate of water absorption of capillary suction since the driving force for the water absorption test is also a response to pressure [25]. Based on the study, permeability and sorptivity of the pore structure of concrete are two different physical characteristics [26]. Thus, permeability and sorptivity of concrete must be evaluated by a different method. A relationship between strength and sorptivity of lightweight concrete indicated that the sorptivity reduced significantly when the strength that is indicating a denser microstructure increased. [26]. The pore structure of cementitious material is significantly affecting properties that are more dependent on material porosity and permeability such as strength and durability [1]. Also, porosity is a primary influencing factor of the strength of the cement paste [2]. Despite this, total void (porosity) determination might not be sufficient as the strength and durability of concrete might be affected by other properties of the voids such as shape, size, and distribution in concrete [27,28]. Therefore, Ramamurthy et al. [1] mentioned that the importance of air-void influencing the strength of foamed concrete and concluded that the strength of foamed concrete is higher when void has a narrower size distribution. Many researchers have studied the relationship between strength and pulse velocity of concrete. The pulse velocity cannot be used as a general indicator of compressive strength because of the factor of its aggregate [2]. However, the strength of concrete has a direct relation with the pulse velocity for well compacted concrete and for given aggregate type [22]. The relationship between ultrasonic pulse velocity (UPV) and compressive strength was found exponential for mineral admixture mortars, both UPV and compressive strength were low at early stages but increases as the curing period increases [29]. The inclusion of ferrochrome ash and lime as partial cement replacement has confirmed a strong relationship between compressive strength, water permeability, and UPV whereby low water permeability gives increment of both compressive strength and UPV [30]. Previous research regarding to the incorporation of ESP as cement replacement material in normal weight concrete had shown positive results in mechanical properties as well as water absorption and sorptivity or either their relationship [31]. A similar study also shows positive result in compressive strength while incorporating eggshell as partial cement replacement [32]. Therefore, this research is aimed to further study and assess environmental impacts and quality performance of incorporating ESP as partial cement replacement material in LFC namely environmental load reduction, absorption properties, UPV, and compressive strength. For the sake of comparison of environmental impacts between different OPC replacement foamed concretes, cradle-togate life cycle assessments have been conducted based on Ecoinvent database and CML baseline method (CML is the abbreviation for the name of an institute of the Faculty of Science of Leiden University in Dutch ‘Centrum voor Milieuwetenschappen in Leiden’).
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2. Experimental program 2.1. Materials Raw materials which originate locally such as ordinary Portland cement (OPC), fine sand, eggshell powder (ESP), foam, and water, were used to prepare lightweight foamed concrete specimen that has a density of 1300 ± 50 kg/m3. The 52.5 N local branded OPC complying with Type I Portland Cement in accordance with ASTM C 150 [33] and MS EN 197-1 [34] was used in this study. Cement was sieved at a size of 300 lm to ensure the removal of hydrated cement lumps. The cement replacement material, eggshell (ES) waste which obtained from the local commercial area such as bakeries, was being cleaned and dried under the hot sun to remove its surface moisture. The ES was then being crushed, ground, and sieved to obtain particle with size less than 63 lm. In order to avoid depletion of lime content, the ES shall be ground within 2 days after obtained from the sources [35]. The chemical compositions of ESP are presented in Table 1 [17]. Fine sand complying with ASTM C 778-02 [36], BS EN 12,620 [37] and BS 882 [38] was used in this study, and it was subjected to 24 h oven drying at 105 °C to remove the moisture content and then sieved to obtain sand with particle size not more than 600 mm. Normal tap water and synthetic foaming agent, which is a special blend of polyoxyethylene alkyether sulfate, were used during the production of LFC. 2.2. Mix proportions In this study, water to cement ratio (w/c) was selected and maintained at 0.58 ± 0.02. Stable foam with a density of 45 ± 5 kg/m3 was produced by the dry pre-foaming method [39]. The foam must be stable in order to resist the pressure of the mortar and hold until a strong skeleton of cement paste is built up
Table 1 Chemical composition of eggshell powder. Chemical Constituents (%)
Eggshell Powder [17]
Eggshell Powder*
Calcium Oxide, CaO Calcium Carbonate, CaCO3 Silicon Dioxide, SiO2 Aluminium Oxide, Al2O3 Ferric Oxide, Fe2O3 Magnesium Oxide, MgO Sulphur Oxide, SO3 Sodium Oxide, Na2O Potassium Oxide, K2O Phosphorus Pentoxide, P2O5 Strontium Oxide, SrO Nickel Oxide, NiO Chlorine, Cl
50.70 – 0.09 0.03 0.02 0.01 0.57 0.19 – 0.24 0.13 0.001 0.219
– 99.19 – 0.207 0.093 – 0.467 – 0.029 – – – –
*Chemical constituents result obtained from X-ray fluorescence (XRF) analysis.
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around the foam or air void [40]. The foaming agent was diluted with water in the foam generator at a ratio of 1:30 by volume. The foam was generated at a pressure of 0.5 MPa and immediately added into the mortar by the amount of 1.6% to 1.9% of dry mix weight. For the LFC incorporated with ESP, the percentage of ESP used as cement replacement material ranging from 2.5% to 10.0% at an interval of 2.5%. A summary of the mixtures and experiment are shown in Table 2. 2.3. Specimens preparation First, the raw materials namely cement, ESP, sand, and water were mixed to obtain base mix or mortar. Then, the dry foam, which generated by the foam generator, was immediately mixed with the mortar thoroughly. The fresh lightweight foamed concrete was controlled at the density of 1300 ± 50 kg/m3 and then poured into the respective mould with a cubical size of 100 mm and cylindrical size of 100 mm diameter and 200 mm height. The specimens were demoulded after 24 h and then water cured under temperature of 25–30 °C until testing the ages of 7, 28, and 90 days respectively. Prior to testing, hardened 100 mm diameter cylindrical specimens were cut into three small cylindrical specimens with a height of 50 mm for the sorptivity test. For every mixture and testing age, 3 specimens were prepared, in which, water absorption, compressive strength, and UPV test share the same specimen. Therefore, total 90 number of 100 mm cubical specimens prepared for 5 mixtures, 3 testing ages, 2 testing groups, and 3 specimens per group; and 15 number of 100 mm diameter and 50 mm height cut cylindrical specimens prepared for 5 mixtures, 1 testing age, and 3 specimens per testing age. 2.4. Testing methods 2.4.1. Initial surface absorption test (ISAT) Initial surface absorption test (ISAT) was conducted as prescribed in BS 1881- Part 208 [41]. This test was conducted to determine the rate of flow of water into an oven-dried and flat concrete surface through both capillary and non-capillary pores, by the circumstances where a water pressure head of 200 mm ± 20 mm and constant temperature are applied. Time taken for water to flow in capillary tubes at a fixed distance was recorded at 10, 30, 60, and 120 min from the time the concrete surface exposed to water. 2.4.2. Sorptivity test Sorptivity test was conducted by referring to ASTM C 1585 [42] and BS EN 772-11 [43]. This test was conducted to determine the flow of water into an oven-dried and flat cut concrete surface by capillary action, where the 100 mm diameter and 50 mm height cut specimens are immersed in water at depth of 1–3 mm to suck the water. The mass of specimens was measured at 1, 5, 10, 15, 30, 60, 90, 120, and 150 min after the concrete surface exposed to water, then the calculation of sorptivity was performed based on ASTM C 1585.
Table 2 Summary of experimental work details. Mix details
c/s
ES/c
w/c
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
1 1 1 1 1
0 0.025 0.050 0.075 0.100
0.58 0.58 0.58 0.58 0.58
± ± ± ± ±
0.02 0.02 0.02 0.02 0.02
Preformed stable foam*
Curing condition
Investigated properties
1.6 to 1.9%
Totally immersed in water at temperature in the range of 25–30 °C
ISAT, compressive strength, and UPV at the ages of 7, 28, and 90 days; Sorptivity and water absorption, at the age of 90 days
Note: c/s = cement to sand ratio, cement included OPC and ES, ES/c = eggshell powder to cement ratio, w/c = water to cement ratio, LFC = lightweight foamed concrete, ES = eggshell. * Percentage of stable foam used was based on the weight of total dry mix which consists of cement, eggshell powder and sand.
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2.4.3. Water absorption test Water absorption test was carried out as referred to BS 1881122 [44]. The surface-dry saturated mass and oven-dried mass of 100 mm cubical specimen was measured after 1 h of air-dried after water curing and after 24 h of oven-drying at the temperature of 105 ± 5 °C respectively to obtain saturated surface dry density (SSDD), and oven-dried density (ODD). Then, water absorption was calculated by (SSDD-ODD)/ODD 100%. This is to test the total amount of water that can be absorbed by the LFC after immersed in water throughout the entire curing period.
Fig. 2 shows the boundary condition of ESP foamed concrete from the cradle-to-gate system, where the activities start from raw material extraction and end with the production of concrete at the mixing plant. The life cycle assessment considered the stages of: (1) extraction of all raw materials of foamed concrete, (2) transportation of raw concrete to mixing plant, and lastly (3) concrete production at the plant. 3. Results and discussion 3.1. Initial surface absorption test
2.4.4. Ultrasonic pulse velocity test (UPV) UPV was measured by a Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT 7) that measures the propagation time of ultrasonic waves (54 kHz) through an oven-dried cubical specimen with accuracy up to 0.1 ls [2]. In accordance with BS EN 12504-4 [45], the direct transmission was adopted by positioning the transmitter and receiver in the middle of each opposing surface of the specimen [6,46,47]. This is the arrangement that gives the most reliable results as the signal strength is the highest [22]. Prior to testing, the apparatus was set up and calibrated to 25.2 ls. This test was performed to check the quality of the LFC. 2.4.5. Compressive strength Compressive strength was determined by using compression test machine. 100 mm oven-dried cubical specimens were used for this test. The loading rate of 0.02 mm/s was applied as referring to BS EN 12390-3 [48].
Fig. 3 shows the effect of the incorporation of ESP on initial surface absorption of LFC at the age of 90 days. Generally, the flow or initial surface absorption of all specimens were decreased with the increased testing time due to the saturation of LFC. A vital observation shows that the incorporation of ESP has resulted in decreased flow or initial surface absorption as compared to the control mix. The higher the percentage of ESP incorporated, the lower the flow was observed. This might because the capillary pore has been interrupted and segmented by the ES particles at which the passage was only partly connected [51,52]. Fig. 4 shows the effect of the incorporation of ESP on 120 min initial surface absorption of the LFC at the ages of 7, 28, and 90 days. The effect of the curing period shows an obvious trend by which the flow or initial surface absorption was decreased along the curing period. The incorporation of ESP that acts as an inert filler in LFC resulted in lower flow or initial surface absorption as compared to that of the control mix.
2.5. Life cycle assessment 3.2. Sorptivity One of the main concerns on concrete production is the environmental impact produced throughout its upstream. LFC is expected to be more environmentally sound by partial replacement of OPC with ESP. A life cycle assessment (LCA) is conducted for the investigation, it follows the guidelines of ISO 14040 [49] and ISO 14044 [50] standards, these standards have been used to capture the environmental impacts of the boundary system under analysis. Since the ESP concrete is yet to be commercialized, some of the environmental impact inventories only assume inputs at laboratory scale. The functional unit of 1 kg of concrete produced is adopted in this study.
Manufacture of cement
Manufacture of aggregates - Gravel - Sand
Manufacture of Foaming Agent
Transportation
Transportation
Transportation
Fig. 5 shows the effect of the incorporation of ESP in LFC on its sorptivity at the age of 90 days. The absorptions of all specimens were increased throughout the testing time. The absorptions of all specimens were directly proportional to the square root of time which gave R2 value nearly to unity as shown in Fig. 5. ESP in LFC has significantly decreased its sorptivity as compared to that of the control mix. The higher the incorporation of eggshell in LFC, the lower its sorptivity coefficient as shown in Fig. 6. However, incorporation of 10% eggshell in LFC has an inverse effect which resulted in a higher sorptivity coefficient than LFC-ES2.5, LFC-ES5.0 and
Transportation
Tap Water
Washing Eggshell Powder
Concrete Mixing Plant
Grinding
Output: Concrete with different eggshell powder replacement
Sieving
Fig. 2. System boundary of LFC with eggshell powder replacement.
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Flow, f (ml/m²s) per 1000 kg/m³
3.5 3 2.5
LFC-CTR
2
LFC-ES2.5 1.5
LFC-ES5.0 LFC-ES7.5
1
LFC-ES10.0 0.5 0 10
30
60
120
Test time (min) Fig. 3. Effect of incorporation of eggshell powder in LFC on its initial surface absorption through the testing time of 10, 30, 60 and 120 min at the age of 90 days.
Flow, f (ml/m²s) per 1000 kg/m³
2.5
2
1.5
7-Day 1
28-Day 90-Day
0.5
0 LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
LFC-ES10.0
Type of Specimens Fig. 4. Effect of incorporation of eggshell powder in LFC on its initial surface absorption during the testing time of 120 min at the ages of 7, 28 and 90 days.
5
y = 0.0437x + 0.3507 R² = 0.9993 (LFC-CTR)
4.5
Absorption, I (mm)
4
y = 0.0271x + 0.6051 R² = 0.9977 (LFC-ES2.5)
3.5
y = 0.0246x + 0.3421 R² = 0.9983 (LFC-ES5.0)
3 2.5
y = 0.0228x + 0.1537 R² = 0.9907 (LFC-ES7.5)
2
y = 0.0304x + 0.1973 R² = 0.9972 (LFC-ES10.0)
1.5 1 0.5 0 0
20
40
60
Square root of time, √t
80
100
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
(s0.5)
Fig. 5. Effect of incorporation of eggshell powder in LFC on its sorptivity at the age of 90 days.
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30
0.05 0.045 0.04 0.035
20
0.03 15
0.025 0.02
10
0.015
Sorptivity (mm/s0.5)
Water Absorption (%)
25
0.01
5
0.005 0
LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
Type of Specimens
LFC-ES10.0
0
Water Absorption Sorptivity
Fig. 6. Effect of incorporation of eggshell powder in LFC on its water absorption and sorptivity at the age of 90 days.
LFC-ES7.5. It might because the cement had been diluted, in which lesser water undergoes hydration process with an increment of replacement level and more free water to form interconnected pores, and when replacement level exceeds a certain value, the further favourable effect of ESP is insufficient to compensate the adverse effect of the said cement dilution effect. In overall, LFCES7.5 has shown the lowest sorptivity coefficient among all specimens. 3.3. Water absorption Fig. 6 shows the effect of the incorporation of ESP on water absorption of the LFC at the age of 90 days. The incorporation of ESP in LFC has decreased the water absorption as compared to that of the control mix. A similar study opined that the incorporation of ESP in normal weight concrete has resulted in lower water absorption [31]. In this study, increment percentage of ESP had resulted in decreased water absorption, however LFC-ES10.0 shows higher water absorption than that of LFC-ES5.0 and LFC-ES7.5 and it might due to cement dilution effect as well. Overall, LFC-ES7.5 has the lowest water absorption. As a summary for ISAT, sorptivity, and water absorption test, ISAT represents initial rate of water penetration underwater pressure head and is guided by interconnected capillary and noncapillary pores, and also affected by shape and size of passage; sorptivity represents ability of concrete to absorb water by capillary action and guide by interconnected capillary pores; and water absorption represents total amount of water absorbed by concrete during curing period, is also guided by interconnected capillary and non-capillary pores. Incorporation of ESP as partial replacement material of cement can improve the mentioned properties, in which the properties improve with increased replacement level of up to 7.5%. A further replacement will start to deteriorate said properties, and this might be caused by the cement dilution effect. 3.4. Compressive strength Fig. 7 shows the effect of incorporation of ESP as partial cement replacement material in LFC on its compressive strength at the ages of 7, 28, and 90 days. It is clearly shown that the performance of compressive strength increased throughout the curing periods. Generally, all specimens of ESP LFC showed higher performance index for all the curing periods as compared to the control mix.
A similar study also deduced that the incorporation of ESP as partial cement replacement in normal weight concrete has possessed higher compressive strength as compared to the control mix [31]. The researcher opined that the ESP has same behaviour as lime stone filler in strength properties. It has been reported that ESP is mostly made up of calcium carbonate. The calcium carbonate might act as an inert filler to increase the compressive strength of concrete [52]. Another possible reason is that the calcium carbonate reacts with alumina phases of cement and produces monocarboaluminates which result in an increment of strength [53]. From the results, LFC-ES7.5 has achieved the highest compressive strength among all LFC specimens. 3.4.1. Correlation between compressive strength and ultrasonic pulse velocity (UPV) The effect of incorporation of ESP on compressive strength and UPV of various types of LFC specimens at the ages of 7, 28, and 90 days are shown in Fig. 8. Both compressive strength and UPV were increased relatively as the percentage of incorporation of ESP increased. However, LFCES10.0 showed lower compressive strength and UPV as illustrated in Fig. 8. Overall, LFC-ES7.5 has achieved both the highest compressive strength and UPV among all LFC specimens. This may due to the reduction of porosity in LFC-ES7.5 which resulted in higher pulse velocity. The reduction of the porous structure of LFC-ES7.5 may due to the effect of ESP derived as calcium carbonate which acts as inert filler. Furthermore, Acharya and Patro [30] highlighted that the effect of inclusion of lime as partial cement replacement had shown the increment of both compressive strength and UPV. Fig. 9 shows the effect of incorporation of ESP on its correlation between compressive strength and UPV at curing ages of 7, 28, and 90 days. R2 values of respective LFC specimens are also shown in Fig. 9. It can be seen that the correlation between compressive strength and UPV was found slightly exponential to each other. Previous studies have shown the same result for correlation between compressive strength and UPV [22,29]. Both compressive strength and UPV for ESP LFC were relatively higher than that of the control mix. From the graph, LFC-ES7.5 has showed the highest compressive strength and UPV. Further increment of replacement level after exceeding 7.5% will deteriorate compressive strength and UPV, and it might also due to cement dilution effect as the LFC might become more porous and favourable effects of ESP is insufficient to compensate adverse effect of cement dilution.
7
4
4.44 4.66 5.08
5.03 5.40 4.86
4.44 4.56
5
3.75 3.72 4.16 4.31 3.30
Performance Index of Compressive Strength (MPa/1000 kg/m3)
6
5.58 5.36
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LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
3
2
1
0
7-Day
28-Day Curing Period (Days)
90-Day
Fig. 7. Performance indexes of compressive strength for various types of specimens at the ages of 7, 28, and 90 days.
8
7
2.0
Compressive Strength, fc (MPa)
6
1.9
5 1.8 4 1.7 3 1.6
2
1.5
1
0
Ultrasonic Pulse Velocity, UPV (km/s) per 1000 kg/m3
2.1
1.4
LFC-CTR
LFC-ES2.5
LFC-ES5.0 LFC-ES7.5 Type of Specimens
LFC-ES10.0
7-Day fc
28-Day fc
90-Day fc
7-Day UPV
28-Day UPV
90-Day UPV
Fig. 8. Effect of incorporation of eggshell powder in LFC on its compressive strength and ultrasonic pulse velocity for various types of specimens at the ages of 7, 28, and 90 days.
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9
Compressive Strength, fc (MPa)
8
R² = 0.9504
7
R² = 0.9689 6
5
R² = 0.9969 R² = 0.8628
R² = 0.9961
4
3 1.80
1.85
1.90
1.95
2.00
2.05
Ultrasonic Pulse Velocity, UPV (km/s) per 1000 kg/m3 LFC-CTR
LFC-ES2.5
LFC-ES5.0
LFC-ES7.5
LFC-ES10.0
Linear (LFC-CTR)
Linear (LFC-ES2.5)
Linear (LFC-ES5.0)
Linear (LFC-ES7.5)
Linear (LFC-ES10.0) Fig. 9. Correlation between compressive strength and ultrasonic pulse velocity for various types of specimens at the ages of 7, 28, and 90 days.
4. Environmental sustainability In regards to life cycle inventory, the inputs and outputs of raw materials of foamed concrete (OPC, fine and coarse aggregates, water, and foaming agent) and transportation are extracted from Ecoinvent 3.4 database. The cut-off system model is adopted in this study. The basic concept of the cut-off system model is the activity of the product is fully responsible for the waste produced, and the recyclable process of the waste product does not give credit to the activity. All transportation is assumed to be by road using diesel fuel. It is assumed that the transport for all raw materials to the concrete mixing plant for a round trip through the road is 100 km. For ESP, the activities start from the transportation of eggshells from poultry or shops to the laboratory, transportation distance is estimated at 10 km. Grinding machine and sieving machine with low voltage are used in the process of preparing ESP, 1.5 kWh of energy is used for grinding and sieving of 1 kg of
eggshell. Besides, 5 kg of water is estimated to be consumed for washing every 1 kg of ES. Drying of the eggshell is done by exposing and drying under local natural weathering. Thus, no input required. The energy usage in the concrete mixing plant is taken from Stripple [54]. The inputs and outputs of concrete mixing are assumed to be identical for both reference concrete and ESP concrete, and therefore all the mixes share the same quantity of environmental loadings from the mixing process. The impact assessment adopted CML baseline method created by the Centre of Environmental Sciences - Leiden University. Six categories of environmental impacts are considered in the analysis, including acidification, climate change, fossil fuel, photochemical oxidation, eutrophication, and ozone layer depletion. The results are tabulated in Table 3. In order to assess the impacts of OPC-ESP replacement, the four quantity ranges of partial OPC-ESP replacement are used to compare with the reference mix.
Table 3 Baseline CML method results for the production of 1 m3 of foamed concrete.
LFC-CTR LFC-ES2.5 LFC-ES5.0 LFC-ES7.5 LFC-ES10.0
Acidification (kg SO2)
Climate change (kg CO2)
Fossil fuel (MJ)
Photochemical oxidation (kg ethylene)
Eutrophication (kg PO4)
Ozone layer depletion ( 10–5 kg CFC-11)
1.291 1.276 ( 1.5%) 1.250 ( 3.6%) 1.233 ( 4.9%) 1.187 ( 8.4%)
505.54 500.90 ( 0.9%) 487.50 ( 3.6%) 477.45 (5.60%) 455.27 (9.90%)
2183 2169 ( 0.6%) 2125 ( 2.7%) 2099 ( 3.8%) 2019 ( 7.5%)
0.0752 0.0734 ( 2.4%) 0.0724 ( 3.7%) 0.0719 ( 4.4%) 0.0701 ( 6.8%)
0.431 0.422 ( 2.1%) 0.416 ( 3.5%) 0.412 ( 4.4%) 0.401 ( 7.0%)
1.702 1.691 ( 0.6%) 1.660 ( 2.5%) 1.645 ( 3.3%) 1.589 ( 6.6%)
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The environmental loads of foamed concrete mainly decided by its OPC content. The magnitude of environmental loads of foamed concrete tends to reduce with the increase of ESP replacement. Among all the concrete ingredients, OPC is the major contributor for every category of environmental impacts since the cement production consumes a lot of energy and involves the combustion of fossil fuel that releases the pollutant to the air and water. Massive of CO2 is emitted from the calcination process that involved the burning of limestone into calcium oxide, and during the burning of fossil fuel for the heating of kiln [55]. At 10% ESP replacement, the reduction of environmental load can achieve as much as 9.9% in the category of climate change, and follow with 8.4% in acidification, 7.5% in fossil fuel, 7% in eutrophication, 6.8% in photochemical oxidation, and 6.6% in ozone layer depletion. In a nutshell, the results of LCA indicate the sustainable application of ESP as a partial replacement of OPC, and contribute to the reduction of environmental impacts in the production of foamed concrete.
5. Conclusion This study shows that the incorporation of eggshell powder that partially replaces cement in lightweight foamed concrete could enhance the quality performance of lightweight foamed concrete and reduce environmental impacts. However, the incorporation of different replacement percentage of eggshell powder has differently influenced the durability and strength properties. From this study, several conclusions can be drawn: 1. By incorporating eggshell powder into lightweight foamed concrete as a partial cement replacement material, initial surface absorption, sorptivity, and water absorption of lightweight foamed concrete have decreased. 2. Both ultrasonic pulse velocity and compressive strength of lightweight foamed concrete increased with the increment of eggshell powder replacement level. Compressive strength is exponential to ultrasonic pulse velocity. 3. The optimal replacement level of eggshell powder is found at 7.5% which gives the highest strength and quality performance of lightweight foamed concrete. 4. It is sustainable to apply eggshell powder to replace ordinary Portland cement at the replacement level of up to 7.5% in the production of lightweight foamed concrete to reduce environmental load.
CRediT authorship contribution statement Hock Yong Tiong: Conceptualization, Methodology, Writing original draft, Writing - review & editing. Siong Kang Lim: Conceptualization, Writing - original draft, Writing - review & editing, Supervision. Yee Ling Lee: Methodology, Investigation, Writing review & editing, Supervision. Chuan Fang Ong: Methodology, Investigation, Writing - original draft, Writing - review & editing. Ming Kun Yew: Resources, Writing - original draft.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Acknowledgement The efforts contributed by Mr. Lee Ren Siong on laboratory work and all supports provided by Universiti Tunku Abdul Rahman are highly appreciated.
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