Building Materials

Specification of Aggregate Concrete Block
Special Blocks Blocks produced to form an extensive 'kit-of-parts' which gives the designer-specifier great flexibility	Block Specification Block description Block types are available in various ranges produced by CBA manufactures, which may be generally described as follows Standard common blocks  Blocks suitable for general building work, offering excellent all round performance and normally available in 440 x 215mm face size, in addition to their loadbearing capabilities, they provide an excellent background for plastering and rendering as wall as for fixings. Paint grade common blocks Blocks manufactured with a close texture and suitable for direct painting. Standard facing blocks Blocks manufactured for applications where shape and texture consistency are of prime importance. Slight variations in color may be discernible .   Architectural masonry facing block Blocks manufactured to high standards of dimensional accuracy and consistency of color and texture. The block are inteded for use in situation where the visual apperance of the wall is of primary concern. The blocks are available in a range of color, textures finishes and shapes.   Dimensions Face sizes Aggregate concrete blocks are typically available in two standard face sizes (length x height)of 440 x 215mm and 390 x 190mm. Other face sizes are available of aid manual handling. To obtain the coordinating dimensions add the specified joint thickness (normally 10mm) to the height and length of the block.  Dimensions tolerances Tolerances permitted by BS EN 771-3 are:   Limiting deviation in millimetres.  Blocks will generally be supplied to D1 tolerance category unless otherwise specified. Block Strengths Block are available in compressive strengths from 2.9N/mm² to 40n/mm² (Solid) and 2.9N/mm² to 22.5N/mm² (cellular and hollow). Common strengths are 3.6N/mm² and 7.3N/mm² Density Aggregate concrete blocks are available in the net dry density range of 650 - 2400kg/m³ with tolerance of ± 10%. The full range of densities will not necessarily be available from all manufacturers. Gross dry densities are typically used for cellular and hollow units and for the same products will be lover than net dry densities. Configuration Units to BS EN 771-3: Aggregate concrete masonry units will fall within one of the 4 groups specified in BS EN 1996-1-1: Eurocode 6 – Design of masonry structures. Group 1 < 25% formed voids Group 2 > 25% < 60% formed vertical voids Group 3 > 25% < 70% formed vertical voids Group 4 > 25% < 50% formed horizontal voids Generally units will fall within Group 1 and Group 2 configurations.
Source From:� The Concrete Block Accosiation buildingmaterial1213.blogspot