5.2　Masonry Works

5.2.1　The shell of brick chimney shall be constructed with the standard or atypical，first grade，ordinary clay fired brick.The brick strength shall meet the design requirements.When there are frost resistance requirements，the brick frost resistance performance shall meet the design requirements.The bricks at the exterior shell surface shall be free of cracks，and the edges of one end shall be intact at least.

5.2.2　When the construction is carried out at general season，bricks shall be wetted with water prior to the construction.And the water content should be 10%-15%.

5.2.3　The shell shall be constructed with headers.When the outer diameter of the shell is larger than 5m，it may also be constructed with stretchers and headers staggered.

5.2.4　When the shell thickness is not less than one and a half of brick length，half brick may be used both inside and outside.But small pieces that the length is less than the half brick shall not be used.

5.2.5　The circumferential cross joints of the adjacent storey shall be staggered by 1/2 of the brick.The cross joints along the radius direction shall be staggered by 1/4 of the brick.The atypical bricks shall be staggered by 1/2 of theirs width.

5.2.6　When the ordinary fired clay brick is cut to the atypical brick for header，it shall be carried out at one side of the brick.The width of the modified smaller head shall not be less than 2/3 of the original width.For the finished exterior shell surface，the staggered brick corner must not exceed 5mm.

5.2.7　The brick storey may be levelly constructed，or inclined to the chimney center.The inclination shall be perpendicular to the slope of the exterior shell surface.The inclination of the brick storey shall be inspected frequently.

5.2.8　Medium sand should be used for the sand of the mortar，and shall be sieved.There shall be no roots and other debris.For the blended cement mortar of which the strength is not less than M5，the clay content of the sand shall not exceed 1%.And for the strength is less than M5，the clay content of the sand shall not exceed 3%.

5.2.9　The mortar mix ratio shall be weight ratio.The consistency shall be 80mm-100mm.The mortar shall be mixed along with the construction work，and shall be all taken prior to the initial set.

5.2.10　The joint mortar of the shell masonry shall be plump.The mortar plumpness must not be less than 80%.The grouting work must not be carried out by pouring water.The shell exterior face shall be grouted.The grout should be 1∶1.5 cement grout mixed with fine sand.