Concrete Masonry. Weights and Process. Grades & Types

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1 Concrete Masonry Weights and Process Two basic weights Normal weight 40 lbs. / unit 1,200-1,800psi comp strength Lightweight lbs. / unit 700-1,000 psi comp strength Molded with a very dry mix - 3 to a mold Molds cost over $25,000 each Mold is cycled 3 to 5 times per minute Cured in low pressure steam kiln to give rapid strength - 90% of rated strength in 2-4 days. Remains very porous unless formulated for face units Expands when wet - contracts when dry Grades Grades & Types N for exterior or moisture exposure below grade S for no weather or moisture exposure Types I Moisture controlled (N-I or S-I) conforms to ASTM standards for moisture in concrete block. II Unrestricted moisture content - may shrink excessively - don t use with brick! 1

2 Parts Webs Face shell Flanges Face shell Apply mortar here Standard sizes work with modular brick 7 5/8 Block height dimension 8 to center of mortar joint 15 5/8 Actual dimension 1 5/8 3 5/8 5 5/8 7 5/8 9 5/8 11 5/8 Nominal dimension 2 block 4 block 6 block 8 block 10 block 12 block Block Sizes Concrete Masonry Units (CMU s) are nominally considered to be 16 inches long, 8 inches tall and 2 to 12 inches deep. A CMU s actual dimension is always 3/8 less than the nominal, to make room for a mortar joint. 2

3 Block form types Standard block for running bond Solid end for corner blocks Solid block Bullnosed block for soft corners 10 or or Return block for corners in 10 or 12 inch block walls Block surface types Standard - appears just as it is when withdrawn from the autoclave Block surface types split face Split face - two blocks poured face to face, then split before curing to make rough textured irregular face 3

4 Block surface types ground face Ground face - face ground lightly to polish cement particles and expose color of aggregate in the concrete Block surface types colorants Colored - mineral colorants added to the concrete mix, more like a deep tint than a solid color. Block surface types scored Scored face - sawcut to same dimension as masonry joint to simulate smaller block face, can be single score to give 8x8 square pattern on face, double score, or triple score. Single scored split face 4

5 Block surface types...spectra-glaze Glazed face - ceramic adhered to face in autoclave process, deeply saturated bright color possible, permanent color, permanent bond Block surface types fluted Fluted, block are formed or sawcut to make a vertical flute pattern. Split faced fluted 5

6 Smooth (standard face) block Split face block Saxon sized brick Maximum heights / lengths of wall Rule of Thumb: Load bearing: Unbraced height or length for a 2 wythe wall (backup + veneer) = 18 x total thickness (backup + veneer) Non loadbearing: Interior: Unbraced height or length (single wythe) = 36 x thickness (single wythe) Exterior: Unbraced height or length (single wythe) = 18 x thickness (single wythe) 6

7 Unbalanced fill (fill on one side, basement or crawl space on the other) 7 of fill = 12 of cmu 5 of fill = 8 of cmu 3 of fill = 8 of cmu Fire ratings Generally considered to be 2 hours Normal weight block does better 4.5 hours Lightweight can resist fire up to 3.2 hours Rated block often labled on faces. 7

8 Trough block The bond beam is a trough-shaped block that acts as formwork. When rebar are placed in the bond beam block, and concrete placed, the bond beam becomes a continuous reinforced beam Bond beams Used at the top of a wall, below bearing for structure, and anywhere the wall needs to be tied together along it s length. 8

9 Bond Beam Key to all connections Meeting Steel 9

10 Meeting Precast 10

11 Stay on Coursing On Course - cores align 11

12 Off Course - loss of core overlap volume and predictability Max allowable rebar size #4 (1/2 ) 3 5/8 5 5/8 #7 (7/8 ) 7 5/8 #9 (1 1/8 ) 9 5/8 #9 (1 1/8 ) 11 5/8 12

13 On Course with a little work Corner Block to speed course correction (12 inch block) Corner block to stay on coursing (10 inch block) 13

14 Support the sill Horizontal Joint Reinforcing The truss that ties it together 14

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