Showing posts from November, 2019


Determination of moisture content in aggregate is of vital importance in the control of the quality of concrete particularly with respect to workability and strength. The measurement of the moisture content of aggregates is basically a very simple operation. But it is complicated by several factors. The aggregate will absorb a certain quantity of water depending on its porosity. The water content can be expressed in terms of the weight of the aggregate when absolutely dry, surface dry or when wet. Water content means the free water, or that held on the surface of the aggregate or the total water content which includes the absorbed water plus the free water, or the water held in the interior portion of aggregate particles.  The measurement of the moisture content of aggregate in the field must be quick, reasonably accurate and must require only simple appartus which can be easily handled and used in the field.  Some of the methods that are being used for determination of moisture


Some of the aggregates are porous and absorptive. Porosity and water absorption of aggregate will affect the water/cement ratio and hence the workability of concrete. The porosity of aggregate will also affect the durability of concrete when the concrete is subjected to freezing and thawing and also when the concrete is subjected to chemically aggressive liquids.  The water absorption of aggregate is determined by measuring the increase in weight of an oven dry sample when immersed in water for 24 hours. The ratio of the increase in weight to the weight of the dry sample expressed as percentage is known as absorption of aggregate. But when we deal with aggregates in concrete the 24 hours absorption may not be of much significance, on the other hand, the percentage of water absorption during the time interval equal of final set of cement may be of more significance. The aggregate absorbs water in concrete and thus affects the workability and final volume of concrete. The rate and a


INTRODUCTION Autoclaved aerated concrete (AAC) block is also known as Autoclaved cellular concrete (ACC) block. It is a lightweight, precast, foam concrete building material which is suitable for producing concrete masonry unit (CMU) like blocks. The material composed of quartz sand, calcined gypsum, lime, cement, water and aluminum powder. AAC products are cured under heat and pressure in an autoclave. AAC blocks are Invented in the mid-1920s, by the Swedish architect and inventor Dr. Johan Axel Eriksson.  AAC simultaneously provides structure, insulation, and fire- and mold-resistance. Forms include blocks, wall panels, floor and roof panels, cladding (fa├žade) panels and lintels. AAC is a highly thermally insulating concrete-based material used for both internal and external construction. Besides AAC's insulating capability, one of its advantages in construction is its quick and easy installation, because the material can be routed, sanded, or cut to size on site usin