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As a knowledgeable expert in various industries, I would like to share some insights on the topic of cement, specifically on the types of cement that are no longer used in modern construction. Cement is a crucial building material that binds together other materials like sand, gravel, and water to form concrete, mortar, and other structures. However, not all cement types are created equal, and some have been phased out due to various reasons. So, what kind of cement is no longer used? Let’s explore.
Firstly, one type of cement that is no longer used widely is asbestos cement. Asbestos is a naturally occurring mineral that was once added to cement to enhance its strength, insulation, and fire resistance. However, asbestos fibers are now known to cause serious health problems, such as lung cancer and mesothelioma, when inhaled or ingested. Therefore, most countries have banned the use of asbestos cement since the 1980s, and replaced it with safer alternatives like fiber-cement or polymer-cement.
Secondly, another type of cement that is becoming less popular is high-alumina cement (HAC). HAC is a type of rapid-hardening cement that contains a high proportion of alumina, which makes it suitable for specialized applications like refractory linings, precast concrete, and marine structures. However, HAC is also prone to cracking, expansion, and corrosion, especially in humid or acidic environments. Moreover, HAC can release heat during hydration, which can cause thermal cracking and weaken the structure. Therefore, HAC is now being replaced by other types of cement, such as Portland cement or blended cement, which offer better durability, versatility, and sustainability.
Lastly, a third type of cement that is no longer used in some regions is sulfate-resisting cement (SRC). SRC is a type of cement that is designed to resist the attack of sulfate ions, which can cause chemical reactions and swelling in concrete, leading to cracking and spalling. SRC is commonly used in areas with high sulfate content in the soil or water, such as coastal regions or industrial areas. However, SRC is also more expensive and less available than ordinary Portland cement, which is the most widely used cement type in the world. Therefore, some countries have stopped producing or promoting SRC, and instead use other measures like proper design, drainage, and maintenance to prevent sulfate attack.
In conclusion, the kind of cement that is no longer used depends on the context and the reasons behind it. Asbestos cement, high-alumina cement, and sulfate-resisting cement are three examples of cement types that are no longer used or used less frequently due to health, performance, or economic concerns. However, there are still many other types of cement that are used in various applications, such as white cement, colored cement, low-heat cement, and blended cement. Therefore, it is important to choose the right type of cement for each project based on its requirements, specifications, and standards.
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