ব্যাখ্যা: Metamorphic rocks are formed by the metamorphism process. Some example of metamorphic rocks are slate, gneiss, schist, marble, soapstone etc.
ব্যাখ্যা: Gneiss is a common and widely distributed type of metamorphic rock or silicious rock. Gneiss is a foliated siliceous rock in which the coarse mineral grains have been arranged into a banded structure.
288. Which of the following is an example of silicious rock? [MES-18]
ব্যাখ্যা: The rocks which contain silica in predominant amount are called as siliceous rocks. Presence of a large amount of free sillca makes them harden and durable. Granite, greiss, quartzite, chert. etc. are example of siliceous rocks.
ব্যাখ্যা: Soundness of cement may be determined by two methods, namely le-chatelier method and autoclave method,
Soundness of cement is tested by le-chatelier apparatus.
291. Laterite is chemically classified as [MES-18]
ব্যাখ্যা: Laterite is chemically classified as Argillaceous rock (আগ্নেয় শিলা) Laterite is a red coloured clayey material wich forms a topsoil in tropical regions. It is hard when it is dry.
ব্যাখ্যা: The specific weight, also known as the unit weight, is the weight per unit volume of a material. A commonly used value is the specific weight of water on Earth at 4°C, which is 9.807 kN/m² or 62.5 Ibf/ft².
293. Which of the following cements is suitable for use in massive concrete structures such as large dams? [BB-20]
ব্যাখ্যা: Low heat cement is one of the hydraulic binding materials and would always be perferred for massive structures such as dams. It has excellent performance such as high final strength, long lasting properties.
296. Oil point-এর ক্ষেত্রে সাধারণত Solvent হিসাবে ব্যবহার করা হয়- [BPSC-20]
ব্যাখ্যা: Oil paint-এর সাথে Turpentine মিশ্রণের মাধ্যমে Paint- কে ব্যবহার উপযোগী করা হয়, কারণ Oil paint-এর Solvent হিসাবে Water মিশ্রিত করা যায় না। Oil paint-কে পাতলা বা নরম করার জন্য Solvent হিসাবে Turpentine ব্যবহার করা হয়।
299. What are the two main elements of Portland cement? [BREB-17, HED-19]
ব্যাখ্যা: The elements of portland cement are lime or calcium oxide, silica, alumina, iron oxide, Magnesium oxide. But the main elements of portland cement are lime and silica.
300. Which of the following is an example of argillaceous rock? [MES-18]
ব্যাখ্যা: The rocks in which clay content is
predominant are called argillaccous rock
The rocks are soft in nature and with the
presence of water they can be crumbled
easily some of the argillaceous rocks are
shale, slate, kaolin, literate etc.