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From Stone to Stone – Experiments with Stone Waste

Part of the graduation project “Mountains Reclaiming the Stone”, Civic Architecture Unit – Arch. Liat Brix and Arch. Ytav Bouhsira 2018/2019

Abstract

This paper addresses the stone waste produced as leftovers from the stone-cutting industry in the Occupied Palestinian Territories. It discusses the idea of recycling that waste as an opportunity for developing alternative crafts in the Palestinian villages that are economically reliant on the stone industry. The proposed reuses involve the techniques of casting and creating new stone models. These models aim at redefining the cultural and architectural role of the stone facade using new raw materials: stone powder, gravel and broken stone pieces. The recycled stones would turn the waste from an environmental burden on the Palestinians to an economic opportunity and a way to rethink their industrial practices and their relationship with the landscape.

The current paper initially explains the background behind the research, describes experiments carried out by designers, artisans and academic researchers as well as experiments that I carried out as part of my graduation project, and finally discusses their conclusions and projections. The aim is to point out the ongoing environmental and economic issues in the Palestinian Territories and to initiate an open-ended research to deal with these issues through material design.


Background

My graduation project, “Mountains reclaiming the Stone”, questions the value of stone in Jerusalem’s cultural heritage by addressing the impact of the stone industry on the landscape and on the building practices in the Occupied Palestinian Territories today. The project shines a light on the environmental and economic aspects of quarrying practices overshadowed by Jerusalem’s holiness.

Since the outset of British Mandate in 1918, Jerusalem has been perceived as a “precious rock” frozen in time. The preservation of stone, as the main local building material in Jerusalem and a physical illustration of its biblical image, has been translated into the most rigorous cladding regulations. These regulations are still valid today within “Greater Jerusalem” – the city of Jerusalem and the surrounding Israeli settlements – driving a huge Palestinian stone industry in the Occupied Territories, widely known as “White Oil”.11 A term used by Judy ...

The stone industry faces many economic challenges today. “We are running out of stone”, says the owner of Al-Waleed Company in Beit Fajjar town, near Bethlehem, the largest industrial zone of stone quarrying and cutting in the West Bank. The remaining lands for extracting the stone within Area B, under partial Palestinian governance, are scarce, while Area C, under full Israeli control, contains the largest areas for possible stone quarrying. Moreover, the industry is mainly dependent on Israeli demand, which constitutes around 65% of the total sales (Hashish, 2012). Nevertheless, in my interviews with the factories’ owners, they acknowledged that this percentage has significantly declined in the last decade due to the Israeli shift towards Turkish and Chinese stones, dramatically affecting the stone-producing sector in Palestine.

Among many other challenges that the industry is facing today, the issue of stone slurry disposal – a by-product of the water circulation used to cool the diamond blades of the stone-cutting machines in the factories – is one of the most urgent to deal with. The slurry has never been dealt with systematically; rather, it is disposed of in large quantities in open areas and it directly affects agriculture and the health of the nearby residents (Beit Fajjar Municipality, 2018). The slurry also inflicts extra costs on the factories that need to dispose of it on a daily or weekly basis.

In my proposal, I revert the stone waste to the construction industry. The aim is to introduce a possible alternative to natural stone while creating new industrial opportunities for Palestinians. To do so, I have looked into international and local research that deals with stone slurry reuse. Also, having this project as my first experience working with material design, I carried out experiments in casting stone waste, utilizing my architectural skills in reusing it as building material.


About Stone Waste

Figure 1: Stone waste. Photo: Abid Alkadri

Stone waste can be divided into two categories: broken pieces disposed of for not being suitable for construction, and stone slurry produced by pressing the sludge released from the stone-cutting machines (a mixture consisting mainly of water and CaCO3).

The broken pieces are usually carried to stone crushers and turned into gravel for construction purposes in various sizes: na’ima, simsimiyya, adasiyya and fuliyya.22 Na’ima is mainly ... The stone slurry is not reused in any significant way, but rather it is disposed of near the factories, inside inactive quarries, in agricultural lands and close to residential areas. A middle-sized stone factory produces around fifteen tons of slurry per day. In one year, around one million tons are produced in the West Bank from all stone factories in total. This amount is equivalent to around half a million cubic meters of pressed slurry per year (Joulani, 2014).


Opportunities

Figure 2: Artificial stone for cladding with blue-glass pieces. Photo: Abid Alkadri

In an interview with the geologist Dr. Taleb Al Harithi, he mentioned possible uses of stone slurry after it is processed, including fodder production, paper production (80% CaCO3 + 20% plastic), medications, polishing materials, etc. These industries can be very promising and can bring great economic benefits; however, they need technologies that may not exist at the moment, and they involve high investment costs and complicated logistics (Al Joulani, 2014).

In his paper “The Stone Slurry in Palestine from Environmental Burden to Economic Opportunities—Feasibility Analysis”, Dr. Nabil Al Joulani argues that among the different possible uses of stone slurry, the current optimal solution that suits the Palestinian economic and environmental circumstances and the challenges associated with the stone industry is the ready-mix concrete.

Figure 3: Reinforced glass fiber concrete with stone slurry powder, Photo: Abid Alkadri

Dr. Al Joulani mentions several reasons for the benefit of using stone slurry in concrete production. One is the practicality of the concrete as a basic construction material and the suitability of ready-mix concrete for vertical construction, which makes concrete a high-demand commodity. Therefore, the use of stone slurry in the concrete mix is an efficient way to get rid of the large amounts of slurry produced annually. Another important factor that favors the use of slurry instead of sand in concrete mixes is the conservation of sand – a non-renewable natural material. This will help create a new, sustainable development engine in addition to getting rid of a heavy, devastating environmental burden (Al Joulani, 2014). The main challenge would be finding the technical tools and knowledge to make it applicable.

 


Local Experiments and Models

Figure 4: Artificial stone tile with around 66% stone slurry. Photo: Abid Alkadri

In the Jerusalem Design Week 2018, designers Avior Zada and Eliad Michaeli presented their new catalog of designed stones that can replace the monotonous stone cladding imposed on architects working in Jerusalem. About 90 stones of varying compositions were hung on the wall, while their shapes are identical as they were cast in the same mold. 80% of the compound are made of stone aggregates and powders while the rest are polymeric binding materials. One example is a stone made of stone powder from a quarry in Sa’ir, Hebron, and clay from a dismantled house in Agripas street, Jerusalem. The work is political and controversial as it mixes materials that have been collected from Israeli areas and from the Occupied Palestinian Territories (Riba, 2018).

These designers see their stones as models that may be mass-produced or even 3D printed to replace the natural limestone in the future. These models raise questions about what “Jerusalem Stone” is, a stone that no longer comes from Jerusalem, but rather from the West Bank or is even imported from China or Turkey nowadays. Are the stones they have developed more local than the natural stones that the building regulations in Jerusalem strictly demand?

Figure 5: The process of casting stone powder with glass powder

Mousa Hureizat from Yatta, Hebron, owns a factory where he produces artificial stone with stone slurry from wet-cast concrete mixes.33 A flowable form of ... Artificial stone is usually made of white cement, sand and gravel aggregates with a small amount of additives to improve its durability. He started his project three years ago, after he realized what a great burden the stone slurry causes to his family’s stone business. He thought he could help recycle the waste by developing an alternative model that not only looks and functions like natural stone but also is made of stone leftovers. He began to add the slurry in very small amounts (up to 5%) to the concrete mix, partially replacing the sand. Today, the stones he produces include up to 70% stone slurry, completely replacing the sand and the gravel in the concrete mix. Mousa claims that the slurry-cement stone not only is made of a better, homogeneous mixture with less possibility of cracks compared to regular, artificial stone, but also is competitive in price and durability with natural stone.

In an interview with Mousa, he gave me three different models that he developed for my reference. The first is an artificial stone made of stone slurry (around 60%), small blue-glass pieces and white cement. The glass is another type of waste produced in large quantities in the glass workshops of Hebron. Mousa hammered the stone face into tubza, 44 A stone brick with ... to reveal the blue glass inside the block. The stone may be used as an outer cladding material to buildings. The second stone is a tile with up to 66% of it made of stone slurry in the wet-cast concrete mix. Mousa also adds chemical dyes to create different shades and effects of the stone tiles, mimicking natural stone. The third stone is a 1cm-thin concrete block curved into a U-shape. The stone is reinforced with glass fiber that gives it a lot of strength.

Figure 6: Blocks made of stone powder with glass powder baked in the oven. Photo: Abid Alkadri

Throughout my graduation project, I worked on experiments with stone waste in the Department of Ceramics and Glass Design in Bezalel Academy, as I was allowed to use their laboratories. These experiments functioned as complementary materials to my architectural proposal in Beit Fajjar. My intervention proposes an economic and cultural renewal in an ongoing, destructive, economic activity in the town, which is mainly based on the stone industry. In my proposal, I present a new model of common stone factories with areas for recycling stone waste and a research center for material development. My aspiration is to help reclaim the historic, integral relationship of Palestinians with their landscape through new industrial and cultural activity. Instead of introducing new materials and technologies, the proposal uses existing materials, techniques and knowledge and recasts them as a starting point for change. My aim behind the stone experiments was to explore the potential of stone powder and gravel as raw materials for designing new mixtures that can be used in the Palestinian stone industry.

Figure 7: Concrete blocks made of a mix of cement and discarded stone pieces. Photo: Abid Alkadri

The first experiment is associated with the specialty of the hosting department: glass. I mixed the stone powder with glass powder in four different ratios, filled plaster molds with them and baked them in the oven at 770 0C. At this temperature, there is a high probability that the stone turn into calcium oxide.55 Commonly known as ... The result is a very light material with tiny pores. The mixture with the highest proportion of glass (75% glass, 25% stone powder) is the hardest model; the mixture with the lowest proportion of glass completely broke apart after being taken out of the mold. Although the material has not undergone any physical or chemical tests, the results suggest that if the model is further developed it will have the potential to act as heat insulator, because of the small air bubbles trapped in it.

In the second experiment, I replaced the stone gravel in the concrete mix with stone pieces that were thrown away as waste from the hammering of stone tile faces used for cladding. I created two models – one with smaller pieces and the other with larger pieces. I cut the surface of the block in order to reveal the stone pieces. According to the physical examinations that I carried out, the block with the larger stone pieces had better compression strength than the other block with the smaller stone pieces.

Figure 8-a: Dry-cast concrete tile with stone-slurry powder

In another experiment, I replaced the sand in the concrete mix with stone slurry, an experiment that has been explored in depth by Dr. Nabil Al Joulani. I tried it in dry-cast66 Dry cast has a low ... concrete tiles and in wet-cast concrete blocks. The compression tests on the wet-cast blocks showed better results for the concrete containing stone slurry instead of sand. However, in order to reach better conclusions, the experiment should be done several times with the final result being based on an average of the different tests’ results. Dr. Al Joulani’s research, which was based on several similar experiments, indicate that slurry-waste powder could be used instead of sand in artificial stone production with reasonable compressive strength and absorption compared to natural stones. His artificial stones, according to him, are more suitable for indoor decoration.

Figure 8b: Dry-cast concrete tile with stone-slurry powder

The last set of experiments involved the technique of compression to create briquettes out of stone-slurry powder. I tried to compress the powder under high pressure of up to 120 tons. At the beginning, I compressed the stone slurry without any additives, and then added other materials such as clay and cement to help bind the powder together. Due to the inaccuracy of the work and the limitations of the used molds – made of several metallic units in cylindrical shape – the models were broken when taken out of the mold. However, these experiments could be further developed with better results if the mold used were made of a single-piece metallic cylinder or any other closed shape, using suitable separation material and technique to carefully remove the inside model.


Conclusions

Figure 9: Wet-cast concrete blocks with stone-slurry powder

From the different experiments discussed in this paper, we can conclude that there are different possibilities for casting stone slurry to create new stone models depending on the technique and the binding material. Their success is measured by different factors: physical qualities (i.e., compressive strength, water absorption, etc.), environmental considerations, economic benefit and aesthetics.

Avior and Eliad’s models presented in the Jerusalem Design Week have great physical qualities when compared to natural stone and can also compete with it economically. The designers have addressed the aesthetic aspects of their stones firstly by mixing different types of stone to create one model, and secondly by developing different shapes of stones to create different functions. However, there may be environmental considerations related to their used materials due to the inclusion of polymeric binding materials.

In Mousa Hureizat’s models, cement is used as a binding material that also brings up the environmental issue. However, the availability of concrete as well as its practicality makes it favorable, economically. The models also have similar physical qualities to natural stone and have more homogeneous mixtures compared to the standard artificial stone mixture. While the colors of Avior and Eliad’s models are a result of mixing different types of natural stone, Mousa uses chemical dyes to add different shades of colors. In some of the models, Mousa uses elastic molds for casting the stone to create curvy shapes, a technique that can be further experimented on to create stone shapes that are impossible to cut from natural stone. These experiments can lead to new interpretations of the stone facade through developing new architectural details from the curvy shapes.

Figure 10: Compressed stone-slurry powder experiments

Replacing gravel with broken stone leftovers in concrete, as demonstrated in my experiments, reduces the amount of cement used in the mix, making it more environmentally efficient. In order to prove its competitiveness with gravel-cement concrete mixes, compression and water absorption tests must be done to compare the two. When cutting the surface of the new concrete to reveal the stones, a mosaic pattern is revealed, adding an aesthetic aspect to the concrete structure. This mixture of concrete and stone introduces a new model of the stone facade for replacing the common stone-cladding technique used to cover the concrete structure. However, the main challenge to be dealt with is the weathering factors that affect the concrete in the long term.

The pressing of stone slurry needs to be studied in depth. An interesting direction would be to use natural materials such as clay and earth as binding materials. This is reminiscent of the rammed-earth technique used to build walls on site. Instead of using a block-and-mortar building technique, a wall made of one module pressed in batches can become the new model of the stone wall.

Figure 10: Compressed stone-slurry powder experiments

In conclusion, each of these models can be developed for different purposes and bring new perspectives to the use of stone as a response to the urgent economic and environmental challenges facing the stone industry in the Occupied Palestinian Territories. This research constitutes an initial and primary step towards future studies, which may examine any of these techniques in depth, investigate new directions and technologies, focus on studying the economic opportunities that arise out of these models, or propose new architectural elements and entire building.

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1. A term used by Judy Price, in her doctoral dissertation.
2. Na’ima is mainly used for painting, simsimiyya and adasiyya for concrete production and fuliyya in road pavement.
3. A flowable form of concrete that is often poured down on molds.
4. A stone brick with a rough, textured face.
5. Commonly known as quicklime or burnt lime, calcium oxide is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature.
6. Dry cast has a low water-to-cement ratio. The mixture is pressed inside a metallic mold and is soaked in the water for 2-3 days.

Bibliography

  • Al Harithi, Taleb. “Interview with the Geologist.” November 2018.
  • Al-Joulani, Nabil, and Nidal Salah. “The Stone Slurry in Palestine from Environmental Burden to Economic Opportunities—Feasibility Analysis”. Journal of Environmental Protection, vol. 05, no. 12, 2014, pp. 1075–1090., doi:10.4236/jep.2014.512106.
  • Al-Joulani, Nabil. “Utilization of Stone Slurry Powder in Production of Artificial Stone”. Research Journal in Engineering and Applied Sciences, 2014.
  • Beit Fajjar Municipality, “وثيقة الخطة التنموية المحلية لبلدة بيت فجار 2021-2018 (Local Development Plan of Beit Fajjar Town 2018-2021”, 2018.
  • Hashish, Maher. “صناعة الحجر والرخام في فلسطين (Stone and Marble Industry in Palestine)”. Dubbel, 2012.
  • Hureizat, Mousa. “Interview on the Utilization of Stone Slurry Powder in Artificial Stone Production”. Apr. 2019.
  • Riba, Na’ama. “איך תיראה האבן הירושלמית בעוד מאה שנה?”, “הארץ”, עיצוב, 11 (How will the Jerusalem Stone Look Like in 100 years), June 2018, www.haaretz.co.il/gallery/design/.premium-MAGAZINE-1.6159682.
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