Rock Pozzolana

About 1.2 square kilometer underlain deposit of hard rock at Maddhapara of district Dinajpur, may be a versatile source of pozzolana in Bangladesh. At present, the mine is designed to produce boulders and aggregates from the underground reserve to meet the requirement of flood control, construction of coastal and town protection embankment, construction and maintenance of bridges, roads and highways, embankment, river training, railway ballast, high rise buildings, decoration tiles and other heavy duty construction works. The rock deposit is overlain by about 140m of unconsolidated sediments. Below this, the basement is the Archean era and subdivided into the kaolinized granodiorite, the weathered granodiorite and fresh granodiorite. Dykes of micro-granodiorite (Fig. 1), fine grained silicified whitish granite (Fig. 2) and pegmatite is thinly inserted in the basement. In the upper part of the basement, the granodiorite was highly weathered and thus is friable. The rock exhibits gr...

Numerous patents, publications, reviews and reports on the beneficial utilization of rice husk ash have appeared during last few decades [ Proceeding of Joint UNIDO-ESCAP-RCTT-PCSIR Workshop on Production of Cement Like Materials from Agro-waste, p 135-49, 1979 ] . In India rice husk has been put to use in some specific areas as renewable source of energy, development of pozzolanic/cementitious materials, filling materials etc. The suitability of rice husk ash as a soil stabilizer were also studied by Okereke of Nigeria [ Housing Science, Vol. 18(1), p 23-42, 1991 ] and he claimed that rice husk ash has some pozzolanic properties which with little addition of cement can effectively stabilizer lateritic soil. One of the earlier reference to potential benefits of using rice husk ash for making cement was published in 1956. [ Agricultural Experimental Station, Louisiana State University, Bull. No.507, 1956 ]. The characteristics of rice husk ash were studied in relation to utilizat...

When pulverized coal is burnt in kiln the ash is carried forward in the gases as fused (soften) particles which solidify into a roughly spherical shape. It is called as fly ash or pulverized fuel ash. The properties of this material as a pozzolana was first reported on in 1937 and its use in concrete started to develop in the USA in the following decade particularly for mass concrete dams. Later its use became wider and spread out to many other countries. In India f ly ash, an industrial by-product from thermal power plants, with annual generation of approximately 108 million tones and its proven suitability for variety of applications as admixture in cement/concrete/mortar, lime pozzolana mixture (bricks/ blocks) etc. is claimed as an ideal material which attracts the special attention. Cement and concrete industries account for 50% fly ash utilization at present. Up to 35% of suitable fly ash can directly be substituted for cement blending material. Addition of fly ash significa...