Seasonal and spatial variation properties of aggregate from different sources in Bangladesh

Abstract

Concrete is one of the most widely used construction materials throughout the world, because of the variations in properties of locally available aggregates due to seasonal and spatial variation, the properties of concrete may vary widely. Aggregates can be classified on the basis of the size of the aggregate as coarse aggregate and fine aggregate. Aggregates generally exhibits two types of properties. They are physical properties (absorption, porosity, permeability, surface texture, strength and elasticity, density and specific gravity, aggregate voids, particle size, hardness and undesirable physical component) and chemical properties (composition, reaction with asphalt and cement). These properties of aggregate vary a lot according to aggregates from different sources are different as the rock from which the aggregate processed are not same. As the geological and geo-morphological process of rock are different, the aggregate formed are also different. Moreover temperature, humidity and rainfall etc varies in different seasons. The specific objectives of the study has been to acquire knowledge about coarse and fine aggregates properties and specifications of collected from different sources in Bangladesh, to observe seasonal and spatial variation on physical properties of aggregates and spatial variation on gradation of fine aggregate from different sources in Bangladesh. Aggregate properties vary significantly with the change of seasons in Bangladesh. Coarse and fine aggregate has been collected from different sources in Sylhet, Moulvibazar, Mymensingh, Munshiganj, Rajbari, Kushtia, Dinajpur, Lalmonirhat and Panchagarh. These samples have been collected in summer season as well as in winter season. According to ASTM and BS specification sieve analysis, specific gravity (OD and SSD) conditions, unit weight (loose and compacted) has been performed in the laboratory for both coarse and fine aggregate. According to ASTM and BS specification aggregate crushing value (ACV) and los angles abrasion test (LAAT) has been performed in the laboratory with coarse aggregate. These research works revels that sieve analysis, aggregate crushing value (ACV) and los angles abrasion (LAAV) value of coarse aggregate exhibit no significant seasonal variation. But the fineness modulus (FM), specific gravity for both oven dry (OD) and saturated surface dry (SSD) conditions, unit weight for both loose and compacted coarse aggregate, seasonal variation has been observed where the values are higher in summer season than winter season. Moreover, the fineness modulus (FM), specific gravity for both oven dry (OD) and saturated surface dry (SSD) conditions, unit weight for both loose and compacted fine aggregate, the values are higher in summer season than winter season and thus seasonal variation has been observed. Spatial variations in properties of coarse and fine aggregate have been predominantly observed during this study for all the tests. Considering specific gravity and unit weight of coarse aggregate, sample from Modhopara in Dinajpur has the higher values in comparisons with other sources. On the other hand it has lower aggregate crushing value and los angles abrasion value. Moreover, in the case of fine aggregate sample from Sumanganj in Sylhet has been observed higher values in fineness modulus (FM) and unit weight in comparisons with other sources. But in specific gravity for both oven dry (OD) and saturated surface dry (SSD) conditions higher value has been found in sample of Fulbaria in Dinajpur. During this research work sand sample have been collected from Jaganathpahar and Sreemangal in Moulvibazar. After washing, drying and sieving this sand resembles with Ottawa sand in most of the properties as physical state, specific gravity, bulk density and colour. The possibility of using sand from Jaganathpahar and Sreemangal in Moulvibazar in lieu of Ottawa sand in research work. On the basis of the seasonal and spatial variation of aggregate properties it has been suggested that the government and construction companies in Bangladesh can get a clear and definite idea of aggregate from different sources in Bangladesh as well as it is possible to select the best aggregate to ensure the quality and strength of concrete.