Cement clinker Type 1 , Type 2 and Type 3 Crown Portland Composite Cement is CEM-II/A-M which is a cement consisting of Clinker, Gypsum, Pulverized Fuel Ash (PFA), Blast Furnance Slag and Limestone designated by the specifications of BDS EN 197-1: 2003; CEM -II/A-M (V-S-L), 42.5 N. PCC is the most suitable cement for constructions in Bangladesh. CEM â?? II /A-M contains 80-94% Clinker, which is substantially higher than CEM â?? II/B-M containing 65 â?? 79% Clinker that provide us extra advantage in strength development and increase concrete performance. Both slag & fly ash (PFA) are used in PCC. Percentage of SiO2 in PFA is higher than slag which is advantageous to gain more long-term strength and ensure durable concrete. This type of cement is used for large constructions all around the world and it has been used during the last few decades. The hydration process of normal cement produces Calcium Silicate Hydrate CHS & Calcium Hydroxide Ca(OH)2. Calcium Hydroxide Ca(OH)2 does not contribute to gain strength and it is the weak part of reaction which is not suitable for concrete. Since PFA contains higher portion of reactive silica and slag contains alumina, it helps to convert Ca(OH)2 into CSH to gain further strength.