masonry specs

huangyhg

masonry specs
in just about every project manual i see i read the following:
d. motar joints:
1. general:
a. lay first course in full bed of mortar; foundation bed joint shall not be less than 1/4" or more than 3/4".
masonry contracts read this to mean spread mortar on the gross cross-sectional area of the cmu.
i read this to mean spread mortar on the net cross-sectional area of the cmu.
aci-530
3.2 d. debris 鈥?construct grout spaces free of mortar
dropping, debris, loose aggregates, and any material
deleterious to masonry grout.
whose right?  
i don't see a definition of full mortar bed in aci530.
however, the commentary to article 3.3 reads "face shell mortar bedding of hollow units is standard....if full mortar beds throughout are required for structural capacity..."
full mortar bedding then, is differentiated from face shell bedding throughout a wall.  as such, it can only include mortaring of the webs, in addition to the face shells.
i assume here we are dealing with placement of cmus for the first course....the initial bed joint, to be specific.
in addition msjc spec 3.3b (c)and the reference you cited, the excerpt below should buttress your point of view:
"the first course on the foundation should have all webs and face shells set in mortart for full bearing. the mortar, however, must not project more than 1/2 inch (13 mm) into the cells that are to contain grout, as shown in figure 4.1".---section 4.2 of the mia rcmc inspector's handbook--last paragraph, page 117 of 4th edition or page 114 of the 5th edition.
show the masonry foreman figure 4.1 in the mia handbook.
full mortar bedding for the first course of masonry refers to the the or gross area of the cmu, which comprises the webs and face shells.
boffintech - the grout spaces are are within the webs and face shells. the point in 3.2 d limits the material deleterious to the masonry grout. the limitations pointed out by henri2 limit the amount of material that may intrude into the grout space. sound mortar extrusions are not considered deleterious materials unless they extend over 1/2".
there are cases where it is desireable that the first course is not laid in a full mortar bed and these must be specifically noted and specified.
for subsequent courses of hollow masonry, face shell mortaring is the standard as listed in 3.3 of aci 530. in the cases where full mortar bedding is required, the engineer should insure and specify that the block configuration is compatible with this requirement, since a standard (in most areas) 2 core cmu does not permit full mortar bedding. shapes permitting this are readily available, but are not normally used or required in most regions or countries.
for full mortar bedding or "partially"(old, but descriptive term) reinforced masonry, a block with two webs spaced at 8" (200 mm) offers complete alighnment of both webs and grout cells in running bond masonry.
dick