#puzzolan

[findsunbiz]

Cabo Verde, also called Cape Verde, country comprising a group of islands that lie 385 miles (620 km) off the west coast of Africa. Praia, on Santiago, is the capital.

Cabo Verde is named for the westernmost cape of Africa, Cape Verde (French: Cap Vert), which is located in nearby Senegal and is the nearest point on the continent. The largest port in the islands is located at Mindelo, on São Vicente. Its deepwater harbour accommodates sizable vessels and has been used as a fueling station since the 19th century.

After independence, the government played a central role in Cabo Verde’s economy and created several state-owned businesses, which ultimately was a limiting factor in the country’s economic growth. Dramatic changes to the Cabo Verdean economic structure, especially from the mid-1990s, have since guided the country toward a market economy. As a result of these reforms, the number of state-owned businesses declined significantly; numerous interests such as utilities companies, banks, tourism-sector entities, and other enterprises had been privatized by the early 2000s.

Cabo Verde’s service-oriented economy is centred on commerce, trade, transport, and public services. The revenue from the country’s international airports, emigrants’ remittances, and, increasingly, tourism are all important and have enabled the balance of payments to stay generally positive despite imports’ far exceeding exports.

Agriculture in Cabo Verde is limited by the severe and recurrent droughts that affect the islands. The harsh conditions have long posed serious challenges to agricultural pursuits, resulting in irregular crop output and periodic bouts of large-scale famine. Poor grazing practices for sheep and goats and little effort toward reforestation and water conservation under the centuries of Portuguese colonialism only aggravated this poor ecological condition. The postcolonial governments have made a major effort to plant drought-resistant acacia trees and build dikes, retaining dams, and terracing in order to curb intense water erosion, improve water retention in the subsoil, and improve and expand the limited areas available for subsistence and small-scale commercial farming.

Crops grown for local consumption include corn (maize), sugarcane, castor beans, broad beans, potatoes, and peanuts (groundnuts). There is a heavy reliance on imported foodstuffs, however, and the importation of food has long been an absolute necessity. Although Cabo Verde’s fishing capabilities are not fully exploited, fish is important for both domestic consumption and export, and both tuna and lobster are caught.

Use of firewood as a source of fuel has placed a strain on Cabo Verde’s woodland resources. While the use of wood fuel continued to increase in the late 20th century, the level of forested area on the islands was simultaneously on the increase because of governmental reforestation efforts. At the beginning of the 21st century, about one-fifth of Cabo Verde was forested.

Cabo Verde has few natural resources. Supplies of sand, limestone, puzzolane (a cement or plaster additive), and salt are of some commercial and utilitarian value. The very limited water supply is a grave liability, and there are no domestic sources of energy except firewood, wind, and sunlight. The country on the whole relies on imported petroleum fuel; on the local level, most domestic energy needs are met by the use of firewood, although the resulting demand placed upon these resources poses an environmental threat. Experimental approaches toward energy supply are under investigation, and the potential of Cabo Verde’s renewable energy resources has been recognized.

Only a few small-scale industries exist in Cabo Verde. These include sewing, textiles, ceramics, mining, timber, beverages, and pharmaceuticals. Tuna fish canning takes place in some areas, and the processing of frozen seafood such as lobster has been profitable.

Banco de Cabo Verde is the central bank and issues the Cabo Verdean currency, the escudo. There are several foreign banks and a stock exchange. The privatization in the late 1990s of a number of financial enterprises, such as banking and insurance institutions, accompanied a broader initiative to privatize state holdings in other economic sectors that was already under way.

Fish, salt, puzzolane, rum, animal hides, bananas, and coffee are exported, but none in very large quantities. As Cabo Verde is heavily dependent on imported food, its principal imports include cereals, fruits and vegetables, beverages, and other foodstuffs. Fuel and building materials are also important. Portugal and Spain are the country’s most important trade partners, although it also maintains significant trade linkages with other countries, such as the Netherlands and the United States.

Services account for a substantial proportion of the gross domestic product. The draw of nautical sports such as sailing and fishing and the attraction of the islands’ biodiversity have contributed to an increase in tourism to the islands, particularly by European visitors.

Industrial activity, including construction, employs a significant proportion of the labour force. In spite of the fact that Cabo Verde is not self-sufficient in food production, more than one-fifth of the labour force is devoted to agricultural pursuits. High unemployment is one of the major factors driving the country’s emigration pattern.

The constitution guarantees workers the right of association, and the country’s unions are grouped under two umbrella organizations, the Council of Free Labor Unions and the National Union of Cabo Verde Workers. Although labourers are also nominally guaranteed the right to strike, government interference has been noted. Unions are also permitted to forge international connections, and some are affiliated with organizations abroad.

Tax revenues account for a significant proportion of the Cabo Verdean budget. Of these, consumption taxes and taxes on income and profits provide the most sizable contributions.

The majority of roads in Cabo Verde are paved, and there are no railways. All the inhabited islands have airports. There is international air service to destinations such as Lisbon, Boston, Rome, Paris, Brazil, and points in western Africa. Within the islands, regular ferries and planes provide local service. There is a small national shipping line and a national airline, Transportes Aéreos de Cabo Verde. Porto Grande, the country’s primary port, is located at Mindelo, on São Vicente; other ports include those located at Praia, on Santiago, and Palmeira, on Sal.

Telephone service in Cabo Verde is generally good, and cellular telephone use is expanding. Compared with the regional average, the proportion of available personal computers relative to the population is quite high, and cybercafes can be found in larger towns and cities.

Finally, I will leave a link which includes all companies and enterprises in Cape Verde, for those who want to research and discover more about this country. Thanks for reading.

All businesses address in Cape Verde: https://findsun.net/Dh

[up889187materialexpression]

Week Six: Think Surface - Research and Gather

Venetian Plaster: an exploration into a craft of a natural material that has declined in modern times

Venetian plaster is a general term that refers to putty made from fired limestone combined with water, then it’s mixed together to make lime plaster [Herzig, 2017]. It has stood the test of time, and its extensive uses can be traced back to ancient Greece and Egypt (and even beyond), and intact pieces of lime plaster have been found in some of the pyramids [Green Growing, 2017]. One of the earliest examples of lime plaster dates to around 7200 BC, where three statues were discovered in Jordan that were sculpted with lime plaster, over an armature of reeds [Schmandt-Besserat, 2020]. When excavated, the statues were in an almost perfect condition, despite their age, – which showed just how durable lime plaster actually is [Tubb, 1998]. During the Pre-Pottery Neolithic, lime plaster was mainly used for architectural and artistic purposes in the Middle East, in settlements around the Levantine and upper Mesopotamian regions of the Fertile Crescent [Chazan, 2017]. One of settlements was Aşikli Höyük in Anatolia, one of the oldest known to use lime plaster in the lining of floors and walls [Hauptmann, Yalcin, 2000]. Ancient lime plaster often contained pozzolan additives to reduce working time, and the proximity to the fertile volcanic lands of Mesopotamia and Anatolia made this a staple in the building of ancient settlements [Hauptmann, Yalcin, 2000].

When applying Venetian plaster, there is no need to paint it; leaving it in a raw state, the plaster is breathable and free of chemicals. Hydrated lime plasters cure, instead of drying. They absorb carbon dioxide, which completes the lime cycle and turns the lime back into stone, giving it a natural appearance [Guralnick, 2020]. The curing process can take up to a century, during which the plaster becomes harder with each passing year.

Lime works well in places that sustain tough weather conditions and works well anywhere that gets a lot of humidity and moisture, such as by the coast. Lime is also the best as a render for the exterior of a building – it is less porous and harder-curing that clay or gypsum plasters. It requires little maintenance over time and can be “refreshed” by applying a new coat of lime wash each year [Abundant Edge, 2020]. Lime plasters are easy to work with, non-toxic and environmentally friendly. It is almost carbon neutral, which means that it is perfect for eco-friendly builds [Abundant Edge, 2020].

It is a traditional method of construction and is encouraged by the Society for the Protection of Ancient Buildings because it allows the building to breathe. It reduces the risk of trapped moisture and consequently, the risk of damage to the structure [Green Growing, 2017]. It regulates the humidity and filters the air, and because of the elevated pH of the lime and caustic properties, it acts as a fungicide, and prevents bacteria and mould from forming and so it creates a healthier living environment for the occupants [Abundant Edge, 2020].

The binding qualities of lime plaster are better than that of cement because lime plaster is made up of finer particles and allows it to penetrate the surface of other materials better. Due to these binding qualities, lime plaster is incredibly strong and long lasting. Lime was used in the construction of the Pantheon’s concrete dome, the world’s largest unreinforced concrete dome. An analysis of Roman concrete revealed that it was made out of three materials: pasty hydrated lime, pozzolan and pieces of aggregate [Muench, 2015]. Lime consisted of calcium carbonate, that was heated in a kiln to undergo a chemical reaction and release the gas in the limestone. After being burnt for days, the end product was quicklime. When quicklime is mixed with water, it becomes pasty and hardens as it dries [Muench, 2015]. Pozzolan is a volcanic ash that when mixed with the quicklime paste, the molecules lock together. And when these products are mixed with a rock aggregate, it further increased the strength [Muench, 2015].  

Lime plaster is versatile, and the finishing effects and appearance can be changed by adding pigments or minerals, and by changing the application technique. Lime plaster can be painted with water soluble paints to create frescoes in the same way the Sistine Chapel was done [Abundant Edge, 2020]. In lime plaster, there are no aggregates added. Tadelakt and Marmorino are plasters which include aggregates such as marble, granite and glass. Their final texture differentiates them from Venetian plaster [Herzig, 2017]. It is important to mention, though, that due to the widespread preference and adoption of drywall and gypsum plaster, there had been a decline in the number of qualified tradesmen who specialise in lime plaster.

The introduction of “white washing”, or painting the plaster white or off-white, emphasises the psychology of the space and colour. White creates a sense of space and it is predominantly used to make a room seem larger and more spacious. White Venetian plaster emanates a “freshness” and simplicity to a space. White brings a balance with other elements of the space, particular natural finishes and objects, such as wood and plants.

The final finish is earthy and soft; applying it in thin translucent layers creates an iridescent finish, giving the material a sense of depth and movement, that shifts with natural light due to the calcite crystals imbedded inside [Herzig, 2017]. The qualities of Venetian plaster offer a minimalistic look to an interior and emanate warmth and lightness in a space. An interior plastered with Venetia plaster looks natural and clean, and offers a modern approach to ancient methods of construction.

Word Count: 922

References:

Tubb, J. (1998). Canaanites (People of the Past). The British Museum Press.

Chazan, M. (2017). World Prehistory and Archaeology: Pathways Through Time. Routledge. p. 197.

Hauptmann, A, Yalcin, Ü. (2000). Lime Plaster, Cement and the First Puzzolanic Reaction. Persée.

Eubanks, W. (2017). Is Lime Plaster Safe to Use? Green and Growing. https://www.greenandgrowing.org/lime-plaster-safe-facts-tips/

Abundant Edge. (2020). Earthen Plasters: The Healthiest and Most Beautiful Ways to Finish Your Home. Abundant Edge. https://abundantedge.com/articles-1-2016-6-17-earthen-plasters-the-healthiest-and-most-beautiful-way-to-finish-your-home/

Ayres, S. Top 10 Reasons Why You Should Give Lime Plaster A Go. Renovate Me. https://renovateme.co.uk/blog/lime-plaster/

Herzig, L. (2017). Venetian Plaster: An Everything-You-Need-To-Know Guide. Architectural Digest. https://www.architecturaldigest.com/story/venetian-plaster-trend-guide

Muench, S. (2015). Construction and Behaviour of the Pantheon. https://brewminate.com/construction-and-behavior-of-the-pantheon/

Guralnick, M. (2020).  Remodeling 101: Modern Plaster Walls, Six Ways. Remodelista. https://www.remodelista.com/posts/modern-plaster-walls-clay-plaster-slaked-lime-plaster-venetian-plaster-and-more/

[maynghiencat]

MÁY NGHIỀN PHẢN KÍCH METSO PHẦN LAN

Máy nghiền phản kích PF

Máy nghiền phản kích được sử dụng như máy nghiền mịn, hoạt động trên nguyên lý bởi sự biến đổi của r

otor và khoang nghiền…

Máy nghiền phản kích có thể nghiền được thô, trung bình, mịn các nguyên vật liệu có độ dài không quá 500 mm, lực đề kháng không vượt quá 350 MPa ( như đá hoa cương, đá Puzzolan, đá vôi, đất), được sử dụng trong các ngành xây dựng. Hiện nay qua thực tiễn, những tính năng tổng hợp của máy nghiền phản kích có thể sánh ngang cùng với máy nghiền côn và máy nghiền búa.

https://youtu.be/fFGY6iV9JEw

Đặc điểm

Máy nghiền phản kích được sử dụng như máy nghiền mịn, hoạt động trên nguyên lý bởi sự biến đổi của rotor và khoang nghiền. Tùy theo mục đích sử dụng, máy nghiền kiểu va đập cũng có thể được sử dụng như một máy nghiền thô. Sản phẩm được sử dụng rộng rãi trong các ngành như xây dựng công trình giao thông, vật liệu xây dựng, và các ngành khác.

Máy nghiền phản kích mang lại hiệu quả cao trong vận hành, công suất lớn, tỷ lệ nghiền cao, dễ vận hành và bảo trì, bảo dưỡng.

Nguyên lý hoạt động

Máy nghiền phản kích là loại thiết bị nghiền sử dụng khả năng phản kích để nghiền nguyên liệu. Khi nguyên liệu vào trong khu làm việc của búa, nguyên liệu chịu sự tác động cực mạnh, không ngừng của búa sau đó nguyên liệu lại bắn trở lại từ trên tấm phản kích trở lại khu làm việc của búa, nguyên liệu được tiến hành nghiền nhiều lần từ to đến nhỏ trong khoang nghiền. Hoạt động nghiền được thực hiện cho đến khi nguyên liệu đạt được độ hạt như yêu cầu, sau đó được đưa ra ngoài.

Công ty THANH LONG JSC cung cấp máy nghiền đá giá tốt, báo giá chính hãng: chuyên cung cấp dây chuyền nghiền đá, nghiền cát nhân tạo, vật tư trạm nghiền chính hãng với giá tốt nhất. Là đại lý của Metso tại Việt Nam, THANH LONG JSC đã lắp đặt trên 25 trạm nghiền cát, đá và sỏi sông, nghiền than từ công suất 50 khối/h đến 750 khối/h. Hãy nhanh tay gọi cho chúng tôi theo sdt: 091- 2712- 772 để được tư vấn giải pháp đầu tư tiết kiệm và hiệu quả nhất.