CHEMICAL ENGINEERING TRANSACTIONS

VOL. 56, 2017

A publication of

The Italian Association

of Chemical Engineering
Online at www.aidic.it/cet

Guest Editors: Jiří Jaromír Klemeš, Peng Yen Liew, Wai Shin Ho, Jeng Shiun Lim
Copyright © 2017, AIDIC Servizi S.r.l.,
ISBN 978-88-95608-47-1; ISSN 2283-9216

Concrete Waste Management Decision Analysis Based On
Life Cycle Assessment

Chooi Mei Maha,*, Takeshi Fujiwaraa, Chin Siong Hob
aSolid Waste Management Research Center, Okayama University, 3-1-1, Tsushima-Naka, Kita-ku, Okayama, 700-8530
Japan
bFaculty of Built Environment, Universiti Teknologi Malaysia, 81310 Skudai, Johor Malaysia
mahchooimei@gmail.com

Malaysia, a developing country has always had a high level of construction activity. While it means economic
growth, the waste generated by the construction industry has always posed a problem. Most of the
construction waste is made up of concrete. The inert and non-hazardous concrete waste, suffers from weak
enforcement provisions and this further escalates it into large scale landfill dumping and illegal dumping. The
consequences of improper waste management are potentially alarming. With the rising concerns of waste
management and global carbon concentrations, this study aims to evaluate the potential environmental
impacts associated with concrete waste materials and to identify the best alternative in managing the concrete
waste. A comprehensive life cycle assessment framework is proposed to assess the environmental impacts
associated with the upstream and downstream of concrete waste life cycle; from raw material extraction to
material processing, distribution to disposal or recycle. This study analysed the life cycle system in three
scenarios: Scenario 1 depicts the cradle-to-grave scenario where concrete waste is sent to landfill without
treatment and recycling. Scenario 2 and 3 depict the cradle-to-cradle scenarios in which the concrete waste is
cyclically recycled into aggregates and reuse as road base material and reuse in recycled aggregate concrete
production. With the compilation of a systematic life cycle inventory of relevant energy, fuel, and process
emissions as inputs and released carbon emissions as outputs, this study helps in interpreting the
environmental impacts of different waste management into a series of quantitative measures for more
informed decision making. A construction project case study is modelled and analysed in the life cycle
assessment framework to demonstrate the model’s applicability. Results from this study suggest that the
recycle of concrete waste into aggregates and reuse in recycled aggregate concrete production have the least
GHG impact to the environment at 0.094 tCO2. Recycling of concrete waste for road base material emits
0.095 tCO2 and followed by landfilling at 0.139 tCO2. This model intended to be an analysis and decision-
making tool while embracing sustainable development stewardship.

1. Introduction
Construction and demolition waste continues to increase in parallel with the economic growth especially in the
emerging and developing countries like Malaysia. Among all the type of waste, concrete waste (CW) occupied
the highest percentage of total waste generated (Mah et al., 2016; Lachimpadi et al., 2012). In USA,
approximately 200 Mt of concrete waste is generated every year (USEPA, 2016). Globally, CW generated is
recycled and reused as road base material or to produce recycled aggregate concrete (RAC). In Australia, 90
% (CCANZ, 2011) of the CW produced is recycled and in Japan, recycling of CW has achieved 99.5 %
recycling rate in 2012 (MLIT, 2014).
However, Malaysian CW management practices are principally guided by economic incentives such as low
disposal cost, inexpensive and abundance of virgin material resources outweigh the recycling cost. The
benefits derived from recycling CW could not offset the recycling cost, resulting in a large-scale of landfill
dumping practices and low recycling rate. Even though CW itself is inert, non-hazardous, and does not
produce GHG in landfill, yet the amount of CW occupying the amount of land in landfill somehow depletes the
finite land resource. In Butera et al. (2015) study, it shows that the leachate caused by CW in landfill could

DOI: 10.3303/CET1756005

Please cite this article as: Mah C.M., Fujiwara T., Ho C.S., 2017, Concrete waste management decision analysis based on life cycle
assessment, Chemical Engineering Transactions, 56, 25-30 DOI:10.3303/CET1756005

potentially cause contamination to subsoil and groundwater too. In addition, with the country’s pledge to
achieve 40 % of reduction in the carbon emission intensity, current CW management practise need to move
toward a green economy transition and lower carbon emissions practice.
Life cycle assessment (LCA) is a useful tool in conducting a systematic assessment focusing in the
environmental impacts of the concrete life cycle from cradle to grave. LCA quantify all the inputs and outputs
of the material flows and assessing how these inputs and outputs impact the environment. The impact
assessment from LCA is useful as a decision-making tool to improve the current concrete waste management
practise, particularly important in the green economy transition (Ondova and Stevulova, 2013). A number of
international researchers have devoted applicable research in the development of construction and demolition
waste, and concrete aggregate LCA. For instance, Mercante et al. (2012) conducted a LCA study to develop
and analyse a life cycle inventory of construction and demolition waste (CDW) management system. Tao et al.
(2016) study in a closed-loop concrete waste LCA based on cradle-to-cradle theory in China. However, even
though many studies have reported the increased importance of LCA of concrete waste, there has been very
little research reported in Malaysia.
The purpose of this study is to evaluate the potential environmental impacts associated with the CW
management in an open-loop and closed-loop LCA and to identify the best alternative in managing the CW
with a case study in Malaysia. The evaluation of the environmental impacts is done through life cycle
assessment in examining the inputs and outputs of the material flows and accessing how the carbon
emissions affect the environment.
The outline of this study is presented in a few sections. Section 1 is the introduction, research purpose and
objective. Second section describes the research methodology, the scenarios development, assumptions, and
analysis. Case study application, result analysis, and discussion are presented in section 3. The last section is
the summary and conclusions of this study.

2. Methodology
Development of concrete LCA is according to LCA analysis defined in ISO 14040 and 14044. Figure 1 shows
the study boundary in which it defines the concrete LCA in 3 types of scenarios. System boundary of this
study defines the cradle-to-grave and cradle-to-gate scenarios. Three scenarios are built to allow the
comparison of different waste management strategy. Scenario 1 is the business as usual scenario (BaU)
where the CW generated from construction site (CS) is sent to landfill without treatment. Scenario 2 is where
the CW is crushed in RP to produces CCA and to be reuse as road base material in road construction site
(RCS). Scenario 3 is where the CW is crushed in RP and the CCA produces is uses as a substitution to VA in
RAC production. Both scenarios 2 and 3 are set to be the countermeasure scenarios of BaU.

Figure 1: System boundary of CW life cycle assessment.

The type of emissions that are considered in this study included the energy and fuel emission from mining,
extraction, and crushing of virgin aggregate (VA), energy emission from recycling plant (RP), fossil fuel
combustion emission, and the avoided emissions from reusing crushed concrete aggregate (CCA).
The effective functional unit of this study is kgCO2/tCW disposed and kgCO2/tCW recycled. These
assumptions and limitation were applied in this study:
• CW material is inert waste which is neither chemically or biologically reactive and will not decompose in

landfill. In landfilling, CW does not emit CH4 and N2O, and both of the substances are not taken into
account as part of the GHG emissions calculation.

• Carbon sink from landfilling is not considered in this study.
• The CO2 emission from calcination process in cement manufacturing is not covered in this study.
• It is assumed that the substitution of CCA with VA in normal concrete and RAC productions does not

affect the content of cement, sand, and water needed for the normal concrete and RAC productions.
Thus, the emission from CCA substitution in RAC production is assumed to be neutral.

• The natural carbonation process occurs in building concrete and the uptake of CO2 in re-carbonation of
CCA are both not considered in this study.

• The carbon footprint of the construction of RP, concrete batching plant (CBP), and construction of
machineries are excluded in this study.

Figure 2: System boundary for scenario 1, BaU
(landfilling)

Figure 3: System boundary for scenario 2 where CW
is recycled as road base material

Scenario 1 –BaU is the landfilling scenario. BaU is current waste management practise in the industry, where
all the CW generated from the construction site (CS) is sent to the landfill without treatment. In general,
landfilling is subjected to GHG emissions from transportation and machineries operation, landfill carbon
storage, energy recovery, and CO2 absorption in the CW in landfill. However, this study focused only on
transportation emissions in anthropogenic CO2 emissions from diesel combustion. Figure 2 shows the material
flow of scenario 1. The amount of CW produces from the CS is assumed to be at w amount. In the RCS, the
demand for aggregate material is assumed to be at x amount. In CBP, it needs y amount of aggregates to
produces a ton of concrete. In this scenario, the w amount of CW is sent for landfilling, neither the RCS nor
the CBP are benefited from the CW. Thus, the demand of aggregates for both the RCS and the CBP are
fulfilled by VA, supplied by AMQ. The total supply of VA needed from AMQ is therefore assumed at (x+y).
Virgin aggregate is a product output from AMQ. To have a complete comparison between the scenarios, the
emissions from AMQ for supplying VA to both RCS and CBP are also considered in this study. Figure 1 shows
the complete system flows of CW and VA. Emissions from scenario 1 are calculated based on transportation
fuel emissions and aggregate mining process emissions (Table 1). The CO2 emission coefficients for
transportation (Et), recycling (Er), and mining (Em) are calculated from life cycle inventory data obtained from
previous researches (Table 2). The value of Et, Er, and Em are 0.14 kg-CO2 t

-1km-1, 1.27 kg-CO2 t
-1km-1 and

31.93 kg-CO2 t
-1km-1. The d1, d5, and d6 denote the distances between CS~LF, AMQ~RCS, AMQ~CBP.

Table 1: Total emissions from scenario 1 – BaU (landfilling)

Emissions Transportation (kg-CO2 t
-1) Mining or Recycle (kg-CO2 t

-1)
CW is sent to landfill Et×w×d1
AMQ supply VA to RCS Et×x×d5 Em×x
AMQ supply VA to CBP Et×y×d6 Em×y
Total emissions from Scenario 1 Et×d1×w + [Et×d5+Em]×x + [Et×d6+Em]×y

Scenario 2 – is the scenario where CW is sent to the RP for recycling, produces CCA and to be reuse as road
base material in the RCS. CCA is the product output from RP and is produced through the processes of
separation, crushing, and sieving of CW. CCA is used to replace VA up to a certain percentage in RAC
production. In scenario 2, it is assumed that 100 % of the CW is recyclable and reusable as road base
material. Thus, the w amount of CW is assumed to have fulfilled the x amount of demand from the RCS (w=x).
Recycling of CW diverted the CW from being dump to landfill. The replacement of VA with CCA as road base
material likewise reduced the mining emissions of the x amount of VA needed in RCS. In this scenario, the
AMQ supply only y amount of VA to the CBP, while the demand for RCS is fulfilled by recycling of CW. Total
emissions from scenario 2 are summarized in Table 3. The d2, d3, and d6 denote distances of CS~RP,
RP~RCS, AMQ~CBP.

Table 2: Calculation of emission factors

Transportation
Fuel

Consumption
(L/t-km)

Emission
Factor

(kgCO2/L)

Emission
kgCO2/t-km

References

Truck Medium Heavy Class 6-
7 (20 t)

0.052 2.66 0.14 (USEPA and
NHTSA, 2016)

Mining Machineries Capacity (t/h)

Fuel
Consumption

(L/h)

Emission
Factor

(kgCO2/km)

Emission
(kgCO2/t)

Extraction (CAT D9R dozzer)
(16.4 m3) 73.8 55 2.66 1.98

(Michalis, 2011)

Pusher / Excavator (CAT
330C excavator) (3 m3) 73.8 30 2.66 1.08

Loader (Volvo L180F 265kW)
(4 m3) 73.8 40 2.66 1.44

Loader (Volvo L150F 265kW)
(4 m3) 73.8 38 2.66 1.37

Primary crusher, secondary
crusher, screen, hopper &
feeder

200 346.5 0.51 0.89

Fuel
Consumption

(L/t-km)

Emission
Factor

(kgCO2/L)

Emission
(kgCO2/t-km)

Off-road mining truck (CAT
797F) 9.46 2.66 25.17

(CAT Caterpillar,
2013)

Emission from Aggregate
Mining Quarry 31.93

Recycling Plant Machinery
Energy

Consumption
(kWh)

Emission
Factor

(kgCO2/kWh)

Emission
(kgCO2/t)

Feed hopper - (Samyoung
Plant Co., 2016) Vibrating feeder

(QH-1042) (200 t) 22 0.51 0.06

Jaw crusher
(FSK-4430) (200 t) 110 0.51 0.28

First cone crushing
(MC-200(A)) (200 t) 160 0.51 0.41

Vibrating screen
(OP3-2160) (200 t) 45 0.51 0.12

Second cone crushing
(MC-200(B)) (200 t) 160 0.51 0.41

Emission from Recycling plant 497 1.27

Table 3: Total emissions from scenario 2 where CW is recycled as road base material

Emissions Transportation (kg-CO2 t
-1) Mining or Recycle (kg-CO2 t

-1)
CW is sent to landfill 0 0
CW is sent to RP, produced CCA Et×w×d2 Er×w
CCA is transport from RP to RCS Et×w×d3
AMQ supply VA to RCS 0 0
AMQ supply VA to CBP Et×y×d6 Em×y
Total emissions from Scenario 2 [Et×(d2+d3) + Er]×w + [Et×d6 + Em]×y

Scenario 3 - is where CW is sent to RP for recycling, produces CCA and to be reuse as a replacement to VA
in RAC production. In RAC production, there are many specifications limit on the percentage of replacement of
VA by CCA. In Hong Kong and New Zealand, up to 100 % of CCA replacement is allowed and the RAC
produces is acceptable for all non-structural applications. Meanwhile, in countries like UK, Australia, Korea,
Germany, Portugal and Hong Kong, the allowable CCA substitution for structural concrete range from 20 % to
35 %, depending on the required RAC strength (CCANZ, 2011). However, the usage of CCA in RAC is likely
to influence most of the concrete properties such as compressive strength, modulus of elasticity, shrinkage,
and creep. The relative density of CCA is about 5 % - 10 % lower than the VA and this is because of the

cement mortar that remains adhered to the aggregates. Nevertheless, RAC can be manufactured using 100 %
CCA replacement where the processing of the CCA and the manufacture of the RAC are all closely controlled
(CCANZ, 2011). In this study, we assumed that the allowable substitution of CCA is 50 % (VA:CCA = 1:1) to
produce a unit of RAC. Thus, the CBP demand on aggregate to produce a unit of RAC is y = 2w. CW is sent to
RP for recycling and only 50 % (0.5w) of CCA produced from RP is sent to CBP to produce RAC. The balance
of the 50 % of CCA (0.5w) is assumed to be unsuitable material for RAC production and is reused in RCS as
road base material. Hence, the supply of VA from the AMQ to the CBP is reduced by 0.5w and is defined as y-
0.5w and the supply of VA from the AMQ to the RCS is defined as (x-0.5w). Recycling of CW to produces
RAC and reuse in the RCS diverted the CW from being dump to landfill. Emissions from scenario 3 are
calculated based on transportation fuel emissions, RP processing emissions, and aggregate mining process
emissions (Table 4). The distances d2, d3, d4, d5, and d6 are the distances between CS~RP, RP~RCS,
RP~CBP, AMQ~RCS, AMQ~CBP.

Figure 4: System boundary for scenario 3 where CW is recycled as road base material and reused to
produces RAC.

Table 4: Total emissions from scenario 3 where CW is recycled as road base material and reused to produces
RAC

Emissions Transportation (kg-CO2 t
-1) Mining or Recycle (kg-CO2 t

-1)
CW is sent to landfill 0 0
CW is sent to RP, produced CCA Et×w×d2 Er×w
CCA is transport from RP to RCS Et×0.5w×d3
CCA is transport from RP to CBP Et×0.5w×d4
AMQ supply VA to RCS Et×(x-0.5w)×d5 Em×(x-0.5w)
AMQ supply VA to CBP Et×(y-0.5w)×d6 Em×(y-0.5w)
Total emissions from Scenario 3 (Et×d2+Er)(w) + (Et×0.5w)(d3+d4) + (Et×d5+Em)(x-0.5w) + [Et×d6+Em](y-0.5w)

3. Analysis and results
The scenario analysis is applied to a high-rise development construction project in Iskandar Malaysia, Johor
Malaysia. Throughout the construction period of 3 y, the project generated approximately w = 3,049.63 t of
CW and the distances between each destination are recorded in shortest driving distance. Transportation
distances between each destination are obtained from plotting in the Google map. The distances are recorded
based on the return trip of the shortest driving distance between the 2 destinations. The d1 = 76 km, d2 = 42
km, d3 = 24 km, d4 = 4 km, d5 = 82 km, and d6 = 76 km. In scenario 3, y=2w = 6,099 t, w=x, 50 % of w is
assumed to be the 50 % of x too. (0.5w = 0.5x=1,524.82 t). Results of the impact assessment are presented in
Table 5.

Table 5: Total emissions from scenarios analysis

Total emissions tCO2 tCO2 / tCW
Scenario 1 – BaU (landfilling) 422.9 0.139
Scenario 2 - CW is recycled as road base material 290.6 0.095
Scenario 3 - CW is recycled as road base material and reused to produces RAC 287.6 0.094

Results show that scenario 3 emits the least GHG at 287.6 tCO2 / 3,049.63 tCW or 0.094 tCO2 / tCW, followed
by scenario 2 that emits 290.6 tCO2. Scenario 1 emits the highest GHG at 370.8 tCO2. Recycling of CW to
produces RAC and to reuses as road base material (scenario 2 and 3) show significant reduction in total CO2

emissions. Both scenarios emit 31 % - 32 % of CO2 lesser as compared to scenario 1 of landfilling. Recycling
of CW leads to reduction of CO2 emissions since it avoids the emissions from virgin materials extraction and
manufacturing.
The transportation emission from scenarios 2 and 3 are main contributor to total emissions and also a driving
factor in determining the feasibility of both scenarios. For instance, the location of the landfill is located far
away from the construction site (d1 = 76 km), while the CBP is set up at just 4 km away from the RP (d4 = 4
km) and in this case, recycling is seems more viable than landfilling. Sensitivity analysis in transport distances
could help to refine the feasibility of the LCA results.
However, uncertainties do exist in this study as in both scenario 2 and 3, the process of removing mortar is not
considered in the final emission factors and the CCA is reuse as-it-is condition. In reality, it is recommended to
remove the mortar adhered to the CW before crushing it to becomes CCA. Mortar removal process will
eventually add more to the GHG emissions.

4. Summary and Conclusions
The main findings of this study can be summarized as follows: while landfilling (scenario 1) of concrete waste
emitted the highest carbon emissions, concrete waste is preferably to recycle as road base material and also
to reuse as a substitution to virgin aggregate in recycled aggregate concrete production (scenario 2 and 3).
Substitution of virgin aggregate with concrete waste shows significant benefits by reducing the necessity of
landfilling, mining of virgin aggregate, and reduction in carbon emissions associated with energy and fuel
consumption. Recycle and reuse of concrete waste could possibly reduce the overall environmental impact as
compared to landfilling.

References

Butera S., Christensen T.H., Astrup T.F., 2015, Life Cycle Assessment of Construction and Demolition Waste
Management, Waste Management 44, 196-205.

CAT Caterpillar, 2013, New Off-Highway Trucks 797F, <www.cat.com/en_US/products/new/equipment/off-
highway-trucks/mining-trucks/18093014.html> accessed 01.09.2016

CCANZ (Cement and Concrete Association of New Zealand), 2011, Recycled Aggregates in New Concrete,
CCANZ, New Zealand.

Lachimpadi S.K., Pereira J.J., Taha M.R., Mokhtar M, 2012, Construction Waste Minimisation Comparing
Conventional and Precast Construction (Mixed System and IBS) Methods in High-RIse Buildings: A
Malaysia Case Study, Resources, Conservation and Recycling 68, 96-103.

Mah C.M., Fujiwara T., Ho C.S., 2016, Construction and Demolition Waste Generation Rates For High-Rise
Buildings in Malaysia, Waste Management and Research, DOI: 10.1177/0734242x16666944.

Mercante I.T., Bovea M.D., Ibáñez-Forés V., Arena A.P., 2012, Life Cycle Assessment of Construction and
Demolition Waste Management Systems: a Spanish Case Study, The International Journal of Life Cycle
Assessment 17, 232-241.

Michalis P., 2011, Report on Equipment Efficiency, Sardinia, Italy.
MLIT (Ministry of land infrastructure transport and tourism), 2014, White Paper on Land, Infrastructure,

Transport and Tourism in Japan 2014, MLIT, Tokyo, Japan.
Ondova M., Stevulova N., 2013, Environmental Assessment of Fly Ash Concrete, Chemical Engineering

Transactions 35, 841-846.
Samyoung Plant Co. L., 2016, Crushing Plant, Sand Plant, and Mill Plant, <www.syplant.co.kr/common/

images/SYKorean_catalog2016.pdf> accessed 01.09.2016
Tao D., Xiao J.Z., Tam Vivian W.Y., 2016, A Closed-Loop Life Cycle Asessment of Recycled Aggregate

Concrete Utilization in China, Waste Management 56, 367-375.
USEPA (United States Environmental Protection Agency), 2016, Construction and Demolition Materials, Office

of Resource Conservation and Recovery, USEPA, United States.
USEPA (United States Environmental Protection Agency) and NHTSA (National Highway Traffic Safety

Administrations), 2016, Joint Fuel Consumption Standards and GHG Emission Limits, USEPA and
NHTSA, United States.