CIB2007-485

Reusing and Recycling Construction Aggregates as Mitigation Measures to

Environmental Destruction The Case of Dar es Salaam, Tanzania

Tobias, S. Mufuruki1; Emilia, L. C. van Egmond; and Frits J.M.

Scheublin

ABSTRACT The extraction, processing, and transportation of construction aggregates cause a variety of environmental destruction in many different ways. Further knowledge on these problems and how to solve them are currently forming many research topics and objectives worldwide. In Dar es salaam City Tanzania, for instance, a research triggered by the escalating environmental destruction, is on going to establish how reusing and recycling of building materials can bring about innovative building materials and environmental protection against extraction of virgin materials and disposal of construction and demolition wastes (C&DW). This paper throws some light on the proposed need and means for sustainable use of construction aggregates to mitigate environmental destruction and other conflicts as construction activities increase with resultant depletion of diminishing natural deposits. Reusing and recycling are among the key ingredients of sustainable construction development. KEYWORDS: Reuse, Recycle, Construction aggregates, Mitigation,

Environmental destruction

1 Contacts: P. O. Box 513, 5600 MB Eindhoven, Netherlands; Tel.: +31 40 247 2745; Mobile: +31 6 48719248; Fax: +31 40 247 8488; E-mail: t.s.mufuruki@tue.nl

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1. INTRODUCTION Construction aggregates are natural mineral and rock materials used by the construction industry in Portland cement concrete, bituminous concrete pavement, road base, construction fill, railway embankment, riprap for water ways, landscaping and other construction uses. The use of these materials is an indicator of the economic well being of a Nation, because of the above mentioned construction products (Kelly, 1997). However, the extraction, processing, and transportation of construction aggregates cause a variety of environmental destruction in many different ways manifested at different stages of the lifecycle of these essential building materials (Figures 1 and 2).

While a number of studies have been done worldwide to understand the impacts of construction industry on environment and how to solve them, the existing gaps in literature are appreciated. Such differences which are mainly caused by variation in construction materials and techniques, work procedures and common practices, limit transfer of research findings among different projects; countries and geographic regions (Yahya and Boussabaine, 2006; Cole, 2005 and Kotaji et al, 2003).

In Dar es Salaam City, Tanzania, there are environmental, land use, and socio-economic conflicts emanating from extraction, processing, transportation and use of construction aggregates. While there are all signs of shortage of aggregates, reusing and recycling are regarded beneficial both from socio-economic and environmental standpoints. This is in line with the National Strategy for Growth and Reduction of Poverty (NSGRP), which is the centerpiece of development policy for Tanzania. NSGRP explicitly focuses on sustainable development as the underlying principle and emphasizes the environment as a foundation for sustainable growth and poverty reduction (Assey et al, 2007). From the technical point of view, increased recycling of aggregates should focus on the fitness for purpose rather than origin (natural or recycled) of the resource (wrap, 2007).

As such, this paper dwells in the context of the CIB working group TG55- smart and sustainable built environment as well as the new working commission W115 - construction materials stewardship, that aims at reducing the deployment and consumption of new non-renewable construction materials, to replace non-renewable materials with renewable ones, to achieve equilibrium in the demand and supply of renewable materials and ultimately to restore the renewable resource base.

2. GENERAL PERSPECTIVES Reusing and recycling of construction and demolition wastes (C&DW) are among the key principles of sustainable construction that advocates creation and operation of healthy built environment based on resource efficiency and ecological principles (Kibert, 2003). As such, they are the

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Environmental Destruction – The Case of Dar es Salaam, Tanzania means to ease pressure on dwindling natural resources as well as protect the environment against further destruction (Crowther, 2001, Kibert, 2003). It is therefore worthwhile to define the terms reuse and recycle because many of the times they are wrongly used interchangeably:

Reuse, refers to using an object or material again, either for its original purpose or for a similar purpose, without significantly altering the physical form of the object or material. Reuse is preferred to recycling because reuse consumes less energy and less resource than recycling (CIWMB, 2006).

Recycle, means using wastes as material to manufacture a new

product, involves altering the physical form of an object or material and making a new object from the altered material. This requires energy and resource input. Nonetheless, recycling consumes less energy and resources than making new replacement items with virgin material (CIWMB, 2006).

Furthermore, three categories of recycling may be identified: recycling using wastes as raw materials for the same or equivalent end use; up-cycle create value–added products; and down-cycle uses wastes as raw materials for a lower value product (Kibert and Chini, 2000) 3. THE FLOW SYSTEM OF CONSTRUCTION AGGREGATES The flow system of construction aggregates may be presented by Figure 1. The sources of supply demand or areas of application, and the residual or end-of-life of products are the key state and stages the construction aggregates exist. However, dissipative losses mainly in form of dusts occur across the three stages, and this is critical as it causes air pollution by increasing the atmospheric suspended particulates.

Figure 1: Construction aggregates flow system (Wilburn, and Goonan, 1998)

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3.1 Sources of Supply of Natural Aggregates Natural aggregates may be mined from different types of rock formations (Table 1). The intended use of aggregates and availability of desired rock in the vicinity of the project area may play a key role in the extraction of respective type of rock materials. Table 1: Types of rocks from which virgin construction aggregates may be extracted for various uses

Classification of Rock Types

Sub-classes and Remarks

Basalt: Dark coloured rock made from rapidly cooled magma at the ocean floor, with small crystals as mineral crystals do not have time to grow very large. They are rich in magnesium

Igneous Rocks solidify from a liquid magma as it cools

Granite: Slow cooled magma allowing crystals to grow to several millimetres or more in size. They are intrusive igneous rock, rich in quartz Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln

Sandstones are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers

Carbonates (Limestone): Made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions. Conglomerate: made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals

Sedimentary Rocks Formed from weathered, stratified (at bottoms of rivers, lakes and oceans) and compacted igneous rocks

Gypsum Rocks made up of sulphate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, moulds, and wallboards Schist: Formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock

Metamorphic Rocks Formed when Igneous and sedimentary rocks are subjected to consolidated heat and pressure Gneiss: may have been granite, which is an igneous rock,

but heat and pressure changed it 3.2 Sources and Quality of Recycled Aggregates Recycled Aggregates can be sourced from a variety of material arising from construction and demolition (concrete, bricks, and tiles), highway maintenance, excavation and utility operations. They can be purchased from demolition sites or from suitably equipped processing centres. There

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Environmental Destruction – The Case of Dar es Salaam, Tanzania are two methods of producing recycled aggregates: in situ at the site of the arising, or ex situ in a central plant. Major cost savings can be achieved by in situ production of recycled aggregate, including transport costs and the accrual of the environmental benefits of reducing lorry movements (wrap, 2007).

The quality of the recycled aggregate is dependent on the quality of the materials that are processed, the selection and separation processing used, and the degree of final processing that these materials undergo. Nevertheless, the focus should be on the technical fitness for purpose rather than origin or the resource of the aggregates. For instance, the recently introduced European standards for aggregates (2004) do not discriminate between different sources, they apply to aggregates from natural, recycled and manufactured materials (wrap, 2007). 3.3 Technical Factors Affecting Aggregates Recycling Wilburn and Goonan, (1998) made a detailed compilation of the technical factors (Table 2) determined to affect the profitability of an aggregates recycling operation. It is noted that all factors do not always apply, but they have been found to apply in many cases. Table 2: Technical factors affecting aggregate recycling

Technical factors Remarks Product Sizes

Screen product-size distributions (that can be adjusted) determine the amount of each product available for sale

Operational Design

In order to maximize efficiency and profitability, careful consideration must be given to operational layout and design, production capacity, and equipment sizing

Labour

Labour requirements are low; a typical operation would require fewer than 10 personnel. For a stationary facility, labour accounts for about 20–30 % of total operating cost, while mobile operation, can be higher due to takedown and setup requirements

Feed Source Material Characteristics

The quality of the feed material to be processed affects product mix, production efficiency, and labour requirements. Deconstruction can produce less mixed materials unlike demolition

Energy Energy, primarily electricity and diesel fuel, is required for powering the processing and transportation equipment. Refer to Wilburn and Goonan, (1998) for energy estimates

Infrastructure Life The useful life of infrastructure affects both supply and demand for recycled aggregate products. Aggregate characteristics, economic utility choices, weather conditions, and intensity of use also impact infrastructure

Recycled Product Specifications

The quality of the recycled aggregate is dependent on the quality of the materials that are processed, the selection and separation processing used, and the degree of final processing that these materials undergo. Thus, the focus should be on the fitness for purpose rather than origin of the resource

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3.4 Developments in Reusing and Recycling Construction Aggregates The road and highway construction are leading in using recycled concrete aggregates as subbase aggregates. In the Netherlands for example where the amount of C&D wastes generated is in the range of 11-16 million tones per year; about 80-90% of this waste stream is recycled mainly as road base (Dorsthorst and Kowalczyk, 2001; Kibert and Chini, 2000; and EU, 2000). Wilburn and Goonan, (1998) listed the advantages and disadvantages related to use of recycled concrete products as road subbase aggregates summarised in Table 3: Table 3: Advantages and disadvantages of using recycled concrete products as road subbase aggregates

Advantages Disadvantages Recycled concrete is inexpensive and will not grow or expand with moisture.

They are often composed of material with highly variable properties.

Recycled concrete has optimum moisture of approximately 13% about twice that of natural road base, due to its particle size distribution. It may absorb twice the water before becoming saturated.

The strength values are often lower than those of natural aggregates, resulting in product application limitations.

Recycled concrete is 10–15% lighter in weight, resulting in reduced transportation costs. Recycled concrete compacts faster up to two to three times as fast as unstabilised natural road base.

Use of recycled material must be evaluated on a project by project basis in order to determine suitability. Customers are often not used to matching material characteristics with project quality requirements.

Masood, et al, (2001) compared the strength and economy of standard and recycled concrete with partial replacement of cement and fine aggregates. The recycled concrete achieved up to 77% compressive strength, and above 90% for splitting tensile and flexural strength and a cost saving of 15%. These indicate the potential of C&D wastes as valuable building materials on technical, environmental and economic grounds. On a separate study Aljassar, et al, (2005), demonstrated that the asphalt concrete produced using aggregates of demolished wastes met all the requirements of local specifications in Kuwait. In another recent development, Poon and Chan, (2005) produced paving blocks made with recycled concrete aggregate and crushed clay bricks that meet minimum requirements in Hong Kong. More successful recycling of aggregates is reported by Wilburn and Goonan, (1998); Poon et al, (2002).

However, it is noted that these studies are not harmonised in terms of methodologies and the standards they are trying to satisfy with the recycled products.

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Environmental Destruction – The Case of Dar es Salaam, Tanzania 4. THE CASE OF DAR ES SALAAM CITY, TANZANIA Dar es Salaam (Figure 2) is the Tanzania’s largest city and major administrative, commercial and industrial and transportation centre. The city has a total surface area of 1,800 square kilometres, of which 1,393 square kilometres is land mass with eight offshore islands, which is about 0.19% of the entire Tanzania Mainland’s area (945,000 square kilometres) (DCC, 2004). The city is divided into three municipalities namely; Ilala, Temeke and Kinondoni with areas of 210; 652 and 531 square Kilometres respectively.

(B) (A)

Indian Ocean

(C)

Figure 2: Map of Dar es Salaam (Tanzania) showing: (A) the three municipalities (Temeke, Ilala and Kinondoni) (modified from DCC, 2004); (B) concentration of construction and (C) quarrying activities (red spots) mainly in Ilala and Kinondoni Municipalities (modified from NBS, 2007) 4.1 Disparity between the City Growth and Services The city’s population grew from only about 3,500 in 1867 to 128,742 in 1957, to 272,821 in 1967 and to 843,000 in 1978 (DCC, 2004). The 1988 census recorded the city’s population to be 1,357,581 while the 2002

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census recorded a population of 2,497,940 with an intercensal growth rate of 4.3% (TNW, 2007b). The current population is estimated at 2,680,535. The relatively high population growth rate is due to increased birth rates, immigration rates, and more significantly by transient population (DCC, 2004). The City’s unprecedented rapid population growth does not balance with the ill-prepared services. Settlements development, land surveying, propagation of simple construction technologies for affordable housing and urban environmental management stand out as key challenges (VPO, 2005). Other challenges include; inadequacy in water supply and power supply.

The shortage in housing has triggered an increasing self-housing, especially in unplanned settlements, and the informal upgrading of unplanned settlements with the rich buying out the poor. This changes the semi-permanent into permanent settlements and low rise to high rise buildings. Both new housing and upgrading increase demand for building materials in the city (Maira, 2001). Of all the materials in demand; aggregates, timber, metals in various forms and cement, are the most used materials. However, the scope of this paper focuses on aggregates (crushed stone, gravel and sand).

4.2 The Demand and Supply of Construction Aggregates In 1997, the National wide aggregates demand was estimated to range between 30 and 60 million tones (Woodbridge, 1997). Table 3 presents National trend of production of construction aggregates, dolomite (CaMg(CO3)2), crashed limestone, Pozzolanic materials and sand. Despite the annual increase in production, it is evident that the estimated production is by far not close to satisfying the demand estimated eight years earlier. It is estimated that about 324,000 tones of stone aggregates are produced annually in Dar es Salaam alone (Maira, 2001). Table 3: Tanzania annual production trend of construction materials (data extracted from Yager, 2005)

Year and amount produced (metric tones)

Material 2000 2001 2002 2003 2004

Aggregates Na Na 20,223 107,960 120,000 e

Dolomite Na Na Na 2,197 2,500 e

Lime stone crashed 1,500,000 2,269,359 2,856,711 1,206,000 r 1,391,000

Pozzolanic materials 57,014 41,468 52,000 105,910 r 152,679

Sand Na Na 503,485 2,035,960 2,400,000 e

Total 1557014 2,310827 3,432,419 3,458,027 4,066,179

e= Estimated data are rounded to no more than three significant digits; Na = Not available; r = Revised.

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Environmental Destruction – The Case of Dar es Salaam, Tanzania 4.3 Current Life Cycle of Construction Aggregates in Dar es Salaam The lifecycle of construction aggregates in Dar es Salaam City as observed in the ongoing research may be summarised by Figure 3. Sources of natural aggregates and the associated operations/processes (extraction, crushing and grading, transportation and using) have been identified. Recycled aggregates are generated from demolition of structures and excavation of infrastructures. Respective actors of each of the identified operations are also indicated.

Operations/Processes

Demolition & Excavation

Crushing & Grading

Transportation Extraction

Actors

Quarrying companies

Small scale miners

Contractors Small scale Recyclers

C&D Wastes Natural sources Uses

Stones & Gravel

Figure 3: Summary of the current life cycle of aggregated in Dar es Salaam as observed in the on going research. It is estimated that about 324,000 tones of stone aggregates worth Tanzanian shillings 7, 128, 000,000 (≈ € 4,280,000) are produced annually

Cross-cutting Issues

Virgin Aggregates Building Concrete Road &Highway base Railway embankment Riprap of Drainage

Reusing & Recycling Foundation fill Filling road potholes Small Concrete works Landscaping

Land use Conflicts Environmental Conflicts Socio-economic Conflicts

Rock outcrops Subsurface rock

Stones &Gravels Crushed concrete Road excavation

Sand Subsurface deposits

Sand Road excavation

Sand Beaches River beds

Disposal Open Dumping

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in Dar es Salaam alone (Maira, 2001). Nonetheless, the demand is still so high especially after the closure in early 2006 of the quarry complex located in Kunduchi area about 10 kilometres from the city centre. Other sources include Mjimwema, Boko, Bunju and Kigamboni quarries, supplemented by small scale family operations in disused quarries scattered throughout the urban area, especially in Msasani, Oysterbay and Masaki. The rock formation in these areas is characterised mainly by coral limestone. The closest quarry site to the city that produce granite stones is Mikese in Morogoro region located about 180 from Dar es Salaam

The cross-cutting issues (Figure 2) are raising alarm because they bring about conflicts among the stakeholders of the construction industry, the environment and the city inhabitants. Such conflicts resulted to the closure by the Government (in 2006) of the quarry complex located in Kunduchi area about 10 kilometres from the city centre. The details of these conflicts are being studied on the ongoing research and will be discussed in subsequent publications.

Environmental conflicts related to sand mining include: erosion on beaches, river/stream bed and banks, destruction of beachfront properties; unearthing infrastructures such as bridge footings, telephone and power poles, water and sewer pipes, thus rendering them prone to further destruction e.g. from wind and vandalism. Eroded river banks cause change of water courses resulting into flooding, that affects property, and threatens lives.

Limestone mining on the other hand, produces dusts which affect neighbouring settlements; shockwaves from blast explosions cause cracks on neighbouring structures/houses; also noise become a nuisance; exhausted mines become waterlogged and breading ground for insect vector e.g. mosquitoes.

Land use conflicts involve incidents such as: Invasion of open spaces and private property (mainly by small scale miners) for sand and stone mining that cause destruction of landscape, and property value; exhausted mines become wastelands, some of which are inhabited without proper reclamation, thus endangering lives. Another conflict is displacement of settlements, e.g. the case of Twiga Cement factory Vs residents of Chasimba village ruled by High Court against the villagers.

Socio-economic conflicts include: destabilisation of self-employment for men, women and children (human crusher or processors) mainly from economically unprivileged families, who are in most cases exploited by middlemen; these human crushers do not have protective gears against injuries and dusts; debris from blasting destruct roofs of neighbouring buildings (Malele, 2006), but owners are not compensated due to informal nature of settlements and the business; also the small and medium scale miners do not pay revenues.

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Environmental Destruction – The Case of Dar es Salaam, Tanzania 5. CONCLUSIONS AND THE WAY FORWARD The shortage of aggregates supply to the city is vivid, and it likely to increase. It is observed that construction and mining activities are taking place on already inhabited areas (Figure 2), thus affecting existing buildings and other infrastructures.

Furthermore, the environmental destruction as a result of mining, processing and transportation of aggregates is likely to get even worse if appropriate measures are not implemented.

Wastage of construction and demolition wastes (C&DW) on the other hand, is another problem that accelerates depletion of natural resource (e.g. construction aggregates), and environmental destruction.

The current expansion of the construction industry in Dar es Salaam City; the already deficient natural aggregates deposits; the existing environmental and other conflicts are just grounds for embarking on reusing and recycling of construction aggregates.

Reusing and recycling can reduce disposal costs and also the cost of new aggregate on construction projects. The environmental benefit includes reducing land destruction air and water pollution as well as unlawful disposal problems and conserving limited landfill space.

The fact that the technological and economic level of Tanzania cannot be compared with that of industrialised countries limits borrowing such developed recycling techniques. Hence this calls for evaluation and upgrading of available and applicable alternatives. These are some of the tasks of the on going research. 6. REFERENCES Aljassar Ahmad H; Al-Fadala Khalifa Bader, Ali Mohammed A. 2005. Recycling building demolition waste in hot-mix asphalt concrete: a case study in Kuwait. J Mater. Cycles Waste Manag. 7:112–115. Assey P, Stephen B, Blandina C, David H, George J, Idris K, Servacius L, Amon M, Eric M, Ruzika M and Longinus R. 2007. Environment at the heart of Tanzania’s development: Lessons from Tanzania’s National Strategy for Growth and Reduction of Poverty (MKUKUTA). Natural Resource Issues Series No. 6. International Institute for Environment and Development. London, UK California Integrated Waste Management Board (CIWMB). 2006. Waste Prevention Terms and Definitions. Internet site: http://www.ciwmb.ca.gov/WPW/Define.htm (accessed February, 2007) Cole Raymond J. 2005. Building environmental assessment methods: redefining intentions and roles. Building Research & Information 35(5), 455–467. Building Research & Information ISSN 0961-3218

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Environmental Destruction – The Case of Dar es Salaam, Tanzania Poon C. S., Yu T.W. and Ng L. H. 2001. A Guide for Managing and Minimizing Building and Demolition Waste Research Centre for Urban Environmental Technology and Management. Department of Civil and Structural Engineering. The Hong Kong Polytechnic University.

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growth and reduction of poverty (NSGRP) Internet site: http://www.tanzania.go.tz/nsgrf.html (accessed in February, 2007) Waste and resource action programme (wrap). Internet site: http://www.wrap.org.uk/index.html (accessed in February, 2007) Woodbridge, M E. 1997. The development and value of a construction material information system. Annual Roads Convention on Road Transport: The Key to Development, Dar es Salaam, 24 - 26 September 1997. Wilburn, D.R. and Goonan, T.G. 1998. Aggregates from Natural and Recycled Sources. Economic Assessments for Construction Applications—A Materials Flow Analysis. U.S. Geological Survey Circular 1176 Yager, T. R. 2005. The mineral industry of Tanzania. Internet site: http://minerals.usgs.gov/minerals/pubs/country/2004/tzmyb04.pdf (February, 2007) Yahya Khairulzan and Boussabaine A. Halim. 2006. Eco-costing of construction waste. Management of Environmental Quality, Vol. 17 No. 1, pp. 6-19. Emerald Group Publishing Limited 1477-7835

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