ETC 1250 Lesson 07b - Lesson 7b Concrete Masonry ETC1250...

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Unformatted text preview: Lesson 7b Concrete Masonry ETC1250 - Properties Of Materials - The first concrete masonry units used in construction were large, ° Chapter # 7 cumbersome blocks of solid concrete that had been cast in P95 324 _ 343 wood forms Late in the nineteenth century builders began experimenting with m the production of hollow concrete has masonry units — Lighter than the solid type — Retained adequate load—c arrying c apacity Concrete Masonry Concrete Masonry ' The first patent for a “OHOW I - The term concrete masonry unit concrete masonry unit mold and M (CMU) refers to molded concrete manufacturing process was units - - — Cored or solid 25:38:! to Harold S. Palmer In _ Manufactured off srte _ _ 7 . — Integrated into the structure on site, — Molds filled With relatively dry utilizing field materials (mortars) and concrete and hand—tamped _ skilled workmanship — 80 units per clay was average _ _ — By the 19203, automatic machines Sizes are stated as nominal were producing about 3000 concrete dimensions masonry units per day ' — 8—in_, 8 X_15 concrete block _ 7 Today manufacturing equipment - ?—5J'5 In. Wide and 7—33 In. High by 15- . SIB in. Lon produce over 20000 block units per - The 313 ingdifference from nominal to day actual represents the head and bed mortarjoint when the block is installed 7 8 x16 block occupies 089 sq it ofwall surface Concrete Masonry Raw Materials - Portland cement — Most is type i portland cement; — Type III high—early—strength cements _ _ used to increase early strengths and - See Florida Block Shapes 8. Sizes reduce breakage during handling handout from Rinker Materials and delivery Portland blast—fumace slag cements, fly ash. silica flour, and other pozzolanic materials may also be substituted for some ofthe type | c ement - Different sizes and shapes are produced regionally ' Clean Water Raw Materials - Aggregates 7 Approximately 90 percent of the unit by weight — Desirable aggregate properties generally are the same as those required to produce quality concrete 1. Toughness, hardness and slrength to resist impact, abrasion, and loading 2. Durability to resist freezing and thawing and expansion and contraction 3, Uniform gradation of fine and coarse aggregate - Produces an economical, moldable mixtu'e and uniform appearance - Aggregates used should not exceed one-third ofthe smallest block shell 4. Free of any deleterious material which would affect strength or cause surface imperfections Manufacture of CMU’s Follow along on pg 327 Figure 7—6 Storing raw materials - The main raw materials used to produce CMUs are cement. sand. and aggregate Cement is stored in storage silos equipped with dust collectors When the sand and aggregates arrive they are normally stockpiled in the yard. then transferred as needed to storage bins Manufacture of CMU’s Follow along on pg 32?r Figure 7—6 Molding - After a concrete batch is mixed, it is fed into a mold - Masonry units can be manufactured in almost any configuration — provided that the sthctural integrity ofme unit is not compromised by walls that are structurally unstable — Arnold box can make many different shapes by altering the combinations of parts that are assembled "he concrete is compacted and consolidated by a combination of pressure and vibration Compacted products are pushed out of the mold onto a steel pallet — The concrete products are referred to as “green" or uncured "he mold can be filled, compacted, and stripped 8 to 11 times per minute — more that 3240 (8" equivalent) concrete masonry units can be made eac I} ”OUT Raw Materials In some cases admixtures - Coloring agents Air—entraining material — Increase plasticity and workability of block mix concretes — Increases ability to resist weathering — Allow greater compaction. producing denser units with more uniform surfaces and less breakage Water repellents — Metallic stearates somewhat effective in reducing absorption rates and capillary action — Use is limited Accelerating admixtures — Calcium chloride and other accelerating admixtures allow faster production rates during cold weather Other additives Manufacture of CMU’s Follow along on pg 327 Figure 7—6 Batching and mixing - Raw materials for each batch are weighed or batched to ensure batch consistency - The mixer is an oversized cylinder turned on its side, with mixing blades attached to a horizontal shaft — Materials are dry mixed in the mixer for several minutes 7 A relativeiy small amount of water is then added to the dry mix — Admixtures, such as water repellents and coloring agents, are also added at this time — The batch is then mixed for five to eight minutes — Once mixed, the concrete is clumped from the bottom of the Manufacture of CMU’s Follow along on pg 32?r Figure 16 Curing Once a curing rack is filled with steel pallets of "green" or uncured products, the entire rack is transported to the kiln or curing chamber Concrete products are normally cured at a maximum temperature of 120“ to 130“ F at atmospheric pressure Steam, if used‘ is turned on to maintain 100% humidity — In sortie climates, the heat generated by the chemical process, referred to as the heat of hydration, is sufficient to raise the temperature to desired levels wimout the use of slum The entire curing process normally takes 24 hours, but could be shortened by adjusting the mix design and curing temperatures Products generally achieve 90% of their ultimate strength when 2 to 4 days old Manufacture of CMU's Follow along on pg 32f F Ipure r-d ' LO'I'I—DI'ESSUFG steam — lilpertenl otfl uncut product-1n Perfumed In urinal lrllns at atrrespnet’o: prEEbll'EE - Curing sequence — Borne IrIIIEI hardenhgfcla FIEf‘rE-zl “1 m3 llaurspllnrtoslm owls - Ths Urns eccetomanhr rare-red to as me hoio'lng Dana-1 - Heating-up pemd ammo-up palm - smmmam drmiflahls'ledlrfll 1hs lilll'l - Tehoeroiu'e ct ire Lriis Is mac-d at a robe not meedinu Bfl'F oer Ito-J. lo- a madman of tall ho 1an -'1I'Ee Binomlshtmdotrandthebhcl‘ transpose 3mm o1'12 in - l1' failure-1. an anthem m.- m :ondlllon mar ha- lrldmad by elm-min: tl'e kiln temperature rorooommabeh' d mus ' Low-pressure steam IIUI'TIQ'S fifiMIFIE] MI'IEIII. I5 economy — museum lite S‘lrfilgflt gain 01 tile units Willey may be plated 'I'llio II'I'LE qUIclocr — 2-1:] 4 SUBMII'ISDFEI} mam orrmrecrmeir ultimte stratum — Birengthof steam-cured bloc: Is more than dIZIIIIlE: thatol moist-cured DIIII Manufacture of GMU's Follow.I along on pg 32? Figure 3-6 * Afiercuring, special operations rren.I occur — Sol ace — Slowing I Curmlfi: masouw units are moved to cutting slatiorla. — Six Iaycrs clhlcclt. each layer whining 15in '13 blocks. dependi’ig upon the I'ithJuEll unit's sme - concrete masclw units are ncrrnelhr stored oLIIside — "I'M: to "that? tulle: I‘Igh — Roqmrc nospoclai protectozlh from the weiher — firchflccluld outcrclc rresohn' units ac con-(cred rri1i1 protoclion — ll shipped to a consLItrclioh pmjcct boo soul. the oral-tag: lroln handing may he qua Iii-gn '- [“1 ed, Split, and Scored phly’s E?! A residence off Bayshore in Tampa Manufacture of CMU’s Follow along on pg 32? Figure T-fi - Hiptt-prcssme steam Least-clove: curing accelerates the block setting time — Saturated 3118311 SI pressures ranging ”M1251EI153NI — Fufolmccl II on mm»: - Curing sequenc e - Ittlal halos-ling ror ae- inc-summoning perm cerore Deng place-1m IhE mimlme — Temmmemm mapsmarsnmrs — 'I'IIIEI'I a 35.1”?" I'Ef‘rpfl‘t'l‘l‘llr‘e reached IhE bionic IS SIIIIHJEEI Io SMITH 5 ID 19 I'IOIJI'S — ”IE pressurereiease [5 EH ”WHOM “BEES EHEIJ'I'ITE‘SE [CI I'I'IZII'ITI FE Rapid. hmnlhmflu rnashl'l'g.I Lrlt: ha lane mnrmreqllrhrlfll'n-Lfl LEI-Em Ll} sfliroeoe siresses * EIIquqII "rubble is le-Illcwud ILIiu ”IE fibula-1| ohm: Hid. ll: CHUE me UE'IT clear: to a. reh‘li'rel,I slable air-rt;I cordilion - High-pressure steam cur'ng‘s prinzipial benefit — mkrlmhfiat 1-day Edam cote! 1D the Ell-In? strengths armoured — PrEflIJEEE il'roenslonalhl Stable LI1I1£ mat EINIDI [ESELdurTIE change Item flirted-cured block Manufacture of CMU’s Follow along on pg 3-2? Figure T—fi Palll‘ilalrlg and stoma v Diced concrete products areremoedtrorn the lrlhs and rho-ed ho a pro-casing sl'ea uherecp‘ihed operations talce plecetocreste ardlectursl units 'I1Ic: unils are then 'cuocd" or palcliaed and fitted in image {tubing consists {dentin Minimal mono placiflgli-emi't Hmaling layers In create an I1Ieu1oclong c the. cones aegonenaly stazlzecl mos: hot-our nut I1 the was urmi liar are delivered to a jco Site. Compressive Strength of CMU’s - Strength and absorption requirements for concrete meeon units are given in ASTM [:90 in the appendix - The factors which affect compressive strength values for concrete bloclc include — Type ofaggcgctc — Gradafion ofaoomgate _ Type of cement — Amount ol'ccrnanl. — Amount ol walcr «- Iil'iietter mixes — Easier to mold and gamer}- yidld hfltficmrfisircstrmfllts — Hreacage otyeat uhIs ncreases {H.II'IQ nanlqu colorants *- 5!er dnr rn'ooes Donsolldatoon prcblen'e durhg mold-I19 operations and altimeter.I Iowa's comp-cm shamans - Each block-nenufacmnno facility. through mammation. will develop rrl'ir dmrgns — Consolidation clur'ng molding — Method of c uring — Shape and size of uni Tensile Strength of CMU’s . Tensile strength, flexural strength, and modulus of elasticity values vary with the compressive strength values — Tensile strength normally ranges from T to 10 percent of the compressive strength — Flexural strength from 15 to 20 percent ofcompressive strength — Modulus of elasticity from 300 to 1200 times the compressive strength Dimensional Changes in CMU's Dimensional changes due to - Temperature changes — Governed primarily by the type of aggregate in the unit — Resolved by Controljoints in long walls - 25 feet apart in walls without openings - 2|] feet apart in walls with openings - 15—15 feet from comers - Located in areas oi high stress concentrations or potential wall weakness — changes in wall leigtrl orthickness, above floor orfoundationjoinls, and below root and floorjoints that bear onthe wall as well as one or both sides of door am window openings hill-H an, onllale brick mum amass Hound-might com-ten: mnry 0.0000052 Lighunighccom mummy 0.0000043 Guanine ELM? Lime ELM“ Marble 0.00M?! Normal weight concrete 0.0000355 Eli-urinal m-I-I em Thermal Properties of CM Us The heat flow through wall systems is a small percentage of the total heat loss in building construction — One square foot of single—pane glass has a heat flow six or seven times as great as a square foot of lightweight concrete block wall with filled cores Resistance values of singlewythe 8 in. Concrete masonry walls are given in figure 7-15a on page 342 Heat-transfer values increase as moisture content increases 7 Walls become saturated. heat transfer increases based upon the masonry unit's density — Exterior masonry walls are usually protected from moisture Absorption of CMU’s Absorption tests provide a measure of the density of the concrete in concrete masonry units — Value is calculated in pounds of water per cubic foot of concrete — Varies over a wide range, depending upon the aggregates used in the unit - From 4 lbs per cu ltfor dense sands and stones - m much as 20 lb per cu It for lightweight aggregates Absorption will also influence other properties — Permeability, thermal conductivity‘ weight reduction, and acoustical properties — High initial rate of absorption or suction indicates concrete masonry units of high permeability and low durability Though CMU’s have reasonably high suction rates — Concrete masonry units are never presoaked Dimensional Changes in CMU’s Moisture content — CMU's expand when wet and shrink when dried — Original drying shrinkage is an important factorin crack development in concrete masonry wall - Drying shrinkage is greatly reduced by propeny curing and drying units so that the moisture content of the unit is in equilibrium with the sunounding air Carbon ation — Irreversible shrinkage when carbon dioxide is absorbed into the hardened concrete paste — Changes in volume are approximately the same as those caused by moisture condition fluctuations — Reduce carbonation during cold by requiring all heat sources to be properly vented to the exterior of the work area Thermal Properties of CM U’s . Masonry construction is considered heavy-wall construction as opposed to light-wall construction of wood and metal stud — Does not respond to temperature changes as rapidly as light c on struction — Even though the two walls' may have the same R values 9‘ r - ililltiL iriiiriiiiiiir l “l Acoustical Properties of CMU’s - Excellent sound barrier because of — Density — In some situations, its absorption qualities - Building codes generally regulate the amount of noise stopped by floors. walls, and ceilings at 40 to 55 db of sound loss for airborne and impact sounds - Concrete masonry units' ability to reduce sound transmission will vary depending upon — Wallconstmction — Type ofblock — Painted or unpainted surfaces — Other characteristics Fire Ratings for CMU’s - Two concerns of fire safety codes — Structural integrity during a fire - Resistance to thermal shock - Resistance to impact - Resistance to overturning forces (See heavy Timber) during the most severe fire — Containment of the fire - Resistance to heat transmission - Resistance to flame spread - Three criteria are used to develop a fire rating for a masonry wall or partition assembly 1. Structural failure of the system while carrying design loads 2. Heat transmission through the wall that will cause an average rise in temperature of the side not exposed to direct flame or a rise of 325°F at one location 3. Passage of: 1. flame or heated gases which will ignite cotton waste 2. water from a fire hose through the wall assembly Estimating Masonry Materials The number of units required determined - Based on the face surface area of the concrete masonry unit — Corners are usually only counted once — Openings over 10 sq tt are deducted from the wall area — Variable waste factors are added - Estimating guide is illustrated on page 345 in Figure 7-18 W Weight of Hamid gum for roam-f: Watt mum» “ too-sq-r: Watt Am NUNM Size Nunavut (mm x eager x Um Maid! um Units M! «are m we; groomer. Sand-Grand W NM Fhirlm rm Mme-y Um'zs I’m-J ammr mum? of Units rc- {ti Fire Ratings for CMU’s - Fire rating in terms of equivalent solid thickness — Thickness that would be obtained if the same amount of concrete were recast without core holes EXAM PLE - A B-in. Hollow masonry wall is constructed with limestone aggregate is 50 percent solid what is the estimated fire resistance of the wall? — 1625 in. X .50 = 3.81 in — Limestone with a 3.4 in equivalent thickness has a fire resistance rating of 1.5 hours — Fire—resistance rating = 1.5+ hrs Aggregate type inthe concrete 4 3 2 1.5 1 1].?‘5 115 masorry unit hoLls hoLls hoLls hoLls hoLl hoLls hoLls - Chart on page 340, FiTure 7-15 4X4116 4550 3550 123 1.3.5 6x4x16 5100 3-900 225 [3.5 83(4le 60130 4450 225 13.5 4XBXIE 4050 3000 19(8le 4600 5350 SXEKIS $550 3951] leExlé 7550 5200 calcareous or siliceous gravel 62(15?) 5.3(135) 4.2 (1D?) 3.6 (91) 2.8 (71} 2.4031) 2.051) Limestone,cinders orstag 59(150) 5.0(121) 4.0 (1o2) 3.4935) 2.?(69) 2.3(53) 1.9(43) Expanded clay, shale or slate 51 (130) 4.4(112) 3.6 (91) 3.3 (34) 2.6035} 2.2 (55) 1.8 (45) Expanded slag or pumice “(119) 4.00132) 3.2 (31) .7939) 2.1 (53} 1.9(43) 1.5 (33) Estimating Masonry Materials Example: - A wall (20) 8’ CMU’s wide and (12) 8’ CMU’s high has 19 mortarjoints along it’s length and 12 joints in it’s height (Walls are laid in a bed of mortar) - Thus it is — (20 x 15-518“ + 19 x 313‘} = 25’ 7-518“ long or simply (20 x15“ — 1 x SIS“) = 26’ 7-5i8‘ long — (12 10-518“ + 12 x 31'8”} = 8’ 0’ high or simply (12 x8”) = 8’ 1]“ high Estimating Masonry Materials - Determine the number of8 x18—in. concrete masonry units required to build a wall 8 ft high and 44 ft long with four 3 x4—tt openings Total wall area 8 X44 11 = 352 sq 11 Subtract the openings 4(3 X4 ft) = — 48 sq tt Net wall area : 304 sq It Number of CMUs = 304 sq ft = 341.6 = 342 units [189 sq it Using Figure Y—18: Net wall area in squares (100 sq it) = 304 sq ft = 3.04 square 100 sq ft 3.04 square X1125 unitstsquare = 342 units The mortar required to place 342 concrete blocks is 15 cu ft per 100 units: [342 unitsHOD) X15 cu ft = 25.55 cu tt NG‘F Edit—£00 Fab :2- n Ilia I! a 33: as: ‘32 .. his. 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