56.-Quality Control of Brick Masonry Construction in the ...

56.-Quality Control of Brick Masonry Construction in the USA

by

c. T. GRIMM

TI/e Vlliver.l' i!)' oI Texas ar Allsrin, Texas

and

R. D. HALSELL

Clay Prod/lcts AssociatiOIl oi lhe Sowhll'esf, Allslin, Texas

ABSTRACT Recommenda/;ons are made for fhe qualiry control of brickwork in ac­cordance wilh best Amer;can prac­lice. Differences belween good and bad workmanship are ilIl1sfrared.

Le Contrôle de Qualité dans la COII­stl'ucr;on en Briques allx Etats-Unis

Qualitatskontl'olle von Ziegelhauten in den USA

Des recommandariolls fondées SUl' la meilleure pratique Gméricaine sonl Jaites pOlir te contrôle de qualité des maçonneries en briques. Des exemples illusfralll les d~lférel1ces entre une bonne ef tine maI/valse exécufion so111

donnés.

In Übereinslimmung mil der beslen amerikanisclren Praxis werden Emp­feh/ungen für die Qualiliilskolllrolle von Z"tegelmauenverk gegeben. Unter­schiede zlI'ischen guter und schlechtel' handlVerk ficher A usführung sind 11-lustriert.

1. INTRODUCTION

Quality contrai af masonry construction is important to lhe structural integrity, aesthetic appeal and economic security af the real-estale investment. Methods for ensuring quality vary greatly within the USA and even more so internationally. 11 is lhe purpose af this paper to ex pose the masonry quality-control rnethods employed in lhe USA to a world audience with confidence lhat an exchange af views will improve Qur rnethods and lhe hope lhat we may have so mething to offer olhers.

This paper frequently employs the word 'should ' to avoid lhe impression lhat lhe preponderance af brick­work in America conforms in detail to the procedures outlined herein. The construction techniques described are those recommended by the Structural Clay Products rnstitute for st ructural masonry which is defined as any load-bearing wall with an average compressive stress of more than 100 Ibf/in2 ar any non·load­bearing wall designed (O support a lateral load of more than 5Ibf/ft 2 . Less restrietive practices are comlTIon for non-structural brick masonry which includes veneer or walls having a compressive st ress of 1001bf/ in 2 o r less or an interior non-loadbearing partition designed to support a lateral load of 5lbf/ft' ar less_

2. MATERIALS 2.1 Bricks

8ricks for structural masonry sholl ld be rOlltinely sampled at lhe job site and tested in a laboratory. 8ricks for nonstructural maso nry should be tested only when quality is questioned by the purehaser. Seleet a sample of test speci mens from each lot of 50000 bricks ar fraction thereof. For lots of more than 500000. seleet fi ve bricks from each 100000 or fract ion thereof.

identification. Tests on bricks should be made in accord­ance with the ASTM Standard Method ofTest' and should inc1ude at least compressive strength, sat uration coefficient, suction, warpage, size, and percent perforation. For structural masonry bricks perforation should not exceed 25 % of the gross area in any plane parallel to the bearing surface. Additional tests may be required for efllores­cence. Tests are rarely required for modulus of rupture ar freezing and thawing.

2.2 Wetting Brick

Welting brick wiU be required if the initial rate of absorption exceeds 0·0250z/in'/min. A rough but effective field test for determining which units require wetting consists of drawing with a wax penei I a cirele approximately I in, in diameter 011 the brick surface, which will be in contaet with the mortar ar grout. With a medieine dropper, place 20 drops of water inside this circle and note the time requi red for lhe water to be abso rbed. (Figure I). If this is less than 8 min, wetting is recommended. High-suction bricks should

Specimens should be representati ve of the lot and should .. include lhe complete range ofcolours and sizes. Standard modular face bricks, conforming to ASTM C2 16-66, I grade FBS. may include units dilfering in length by nor more than t in. Mark each brick test specimen for FIGURE l- Field test fo r initial rale of absorption.

337

338 Quality Control of Brick Masonry Construction in the USA

FIGURE 2- Brick when laid should be nearly saturated surfacc dry (upper lefl). Dry surface wel (upper right), tOlally dry (Iower left) and lotally saturaled (Iowcr right) are nOI acceptable.

be thoroughly wetted 3 to 24 h prior to use by sub­mersion in waler for 1 to 3 mino Bricks should be surface dry and nearly saturated (Figure 2). The ideal moisture content is about two-thirds of the 24-h cold water absorption .3

2.3 Mortar and Grout

ASTM specifications for sampling and testing field specimens af mortar and grout are nQw under develop­ment in the USA. T n the interim for structural brick masonry lhe constituent morta r materiais must be sampled and tested separately and their proportions carefully controlled on the job. No air-entraining admixture and no mortar material containing any air­entraining agent should be permitted in morta r used in structural brick masonry, and this requirement should be rigorously enforced. Mortar materiaIs are rarely tested for non-structural brick masonry. In this case reliance is placed on the in tegrity of the material sup­pliers and 00 lhe contractor's proportioning technique.

2.4 Cement

Cement shOllld conform to the applicable ASTM speCl­fication. For structural brick masonry only Portland cement conforming to ASTM C I50' shollld be permitted. Air-entraining Portland cements, masonry cements, and other cement types should be used only in non-structural brick masonry.

2.5 Lime

Lime should conform to ASTM C5' or ASTM C207.· For structural brick masonry only ASTM C207 type-S non-air-entraining lime should be used.

2.6 Aggregate

Aggregate should conform to ASTM CI447 for mortar and C404' for grou!. The maximum aggregate size is t in . for mortar joiot sizes between t and t in. For t -in. joints 95 % of the aggregate should pass a No. 16 sieve. Aggregate should not exceed t in . for coarso grout and i in . for fine grou!.

2.7 Water

Water should be clean. The 7-day compressive strenglh

of morta r made with questionable water should be at least 90 % of companion specimens made with potable water.

2.8 Admixtures Admixtures should not be permitted in mortar for structural brick masanry, but mineral pigments and calcium cnloride may be used in restricted quantities, when laboratory tests indicate adequate strength for the same materiaIs and quantities to be employed in the project. Calcium chloride may be used in amounts not exceeding 2 % of the weight of the cement, but should not be used in morta r or groul in which metal ties ar anchors are used. Mineral pigments should not exceed 10 % of the weight of the cemenl. Carbon black should nol exceed I t % of the cement weight.

2.9 Proporlions Proportion mortar or grout materiaIs accurately by use of volume or weighl measuring devices, e.g. a l-ftJ box. Shovel measurements are rarely accurate. Use maximum amount of water consistent with workability. Mortar may be retempered as often as necessary (bul see below) by making a mortar bowl into which water is passed and working the mortar into the water by trowel ar shovel. Grout should have slump (ASTM C1439) be­tween 9 and II in. to pour readily. The aggregate volume should be 2:\- to 3 times the sum of the volumes of the cementious materiais, i.e . cernent and lime.

2.10 Mixiog and Use Mix mortar and grout mechanically aI least 5 mino Use mortar and grout within 2t h of mixing or until set has begun, whichever is less.

2.11 MelaI Reinforcing steel should conform to the applicable ASTM specifications. Before placement it should be free of rust and other coatings or kinks. Metal ties and anchors in each shipment shou ld be measured for com­pliance with thickness requirements. Copper or zinc coating requirements should be strictly enforced. Certifi­cates of compliance with the specifications should be required for ali metal anchors and ties.

2. I2 Storage MateriaIs storage should be safe, under a water repellenl co ver, off the ground and in a dry place (Figure 3).

3. ERECTION

3.1 Sample Panels Sample panels of masonry should be erected as required by the specificatians as acceptance criteria for the visual characteristics af masonry in the praject.

3.2 Morlar Joiots Mortar joints should be completely filled and should not exceed 1- in. in thickness in structural brick masonry. Minimum grout or mortar joint thickness between brick and reinforcement should be not less than t in . except that t- in . bars may be laid in t- in. horizontal mortar joints, and No. 6 gauge or smaller wires may be laid in ·~ -in . horizontal joints. Collar joints or grouted

C. T. Grimm and R. D. Halsell 339

FIGURE 3- Light plastic covers are used to protect materiais in job storage.

cores containing both horizontal and vertical reinforce­ment should be not less Ihan 1 in. larger Ihan lhe sum af the diameters af the horizontal and vertical reinforce­ment conlained Iherein. High slump grout should ftow freely around steel (Figure 4).

Bricks should be laid wilhin I min of spreading morta r. Mortar should not be strung oul ai great lenglhs and deeply furrowed. Morlar placed on the wall should not exceed above tive bricks in length. and lhe bed joint should be bevelled, not furrowed (Figure 5). The head of each brick should be complelely covered with morlar (Figure 6) and nol just 'buttered' on Iwo edges. Bricks placed in deeply furrowed bed joinls and 'buttered' head joints weaken the wall and leave voids through which water can traveI. Slushing head joints after they are laid does not completely till the joint. Brick suction should be such as to develop good bond with lhe mortar, which should cling to a brick removed after laying. Mortar should protrude on ali sides of the brick being laid. A lap wilh the trowel on a brick just laid improves bond strength, but subsequent movement of the brick breaks bond. Collar joints left untilled promote increased waler permeability and low strength.

Keep the interior of cavity walls and grout spaces free of mortar droppings. Grouting in spaces less than i in. in lhe least horizontal direction should not be permitted. Fine groul may be used in spaces having a least horizontal dimension af i to 2 in. Coarse graut may be used in larger spaces. The maximum height of groul pour is 12 in. in spaces less than 2 in. in the least horizontal dimension and 4 ft in larger spaces. The pour length should not exceed 25 ft. The wall should be at least 3 days old before grouting and 5 days old in rainy weather. Puddle or vibrate grout after each pour. When grouting is stopped for I h or longer, the grout should be stopped 11 in. below the top of the last course. Bricks may be placed in groul cores provided the distance between bricks is at leasl i in. (Figure 7).

Line pins should nol be permitted since line-pin holes are frequentIy left unplugged. The use of line blocks is preferable. For maximum resistance to rain penetration, mortar joinls should be tooled concave or V-shaped.

FIGURE 4- Steel placemcnI shouldlProvide aI least !~in. groul between steel and brick.

FIGURE 5- Bed joints should be bevelled and only lightly furrowed, ir at alI.

FIGURE 6-Header end should be- completely covered before the brick is laid.

340 Quality Control or Brick Masonry Construction in the USA

• • • • •

1\ ; •• • • • • •

FIGURE 7- Provide t ·in. min itnurn joint b; lwecn br icks wnc n bricks are placed in grout core.

3.3 Masonry Test Specimens

These are not required for non-structural maso nry. but three test prisms for compressive strength sho uld be made for each 5000 ft 2 of slrucl ural brick masonry wall area Of each storey height, whichever is the more frequent. The pri sl11s should be stored at lhe si te in air for not less than 24 h. Thereafter. lhey shall be stored in air temperalures not less lhan 18' C and sha ll be tested afler ageing 28 days. Seven-day strengl h may be as­sumed to a[[ain 90 % of lhe 28-day slrenglh . Prisms should be built of si mi lar materiais under lhe same coo­ditions as lhe structure. In building lhe pri sms, the moisture con tent af the units at time af laying, lhe consistency of lhe mortar, lhe thickness cf mortar joints, and the workmanship should be the same as will be used in the structure. Specimens should be not less lhan 12 in. in height and should have a height-to-thickness ralio (h(r) as close lo 5 as praclical but nol more than 5. Each specimen should be marked for easy idenlification. In lhe absence of a slandard ASTM test method which is now under developrnent lhe test procedure should comply with the requirements of the Slructural Clay Products Instilule " (Figure 8).

3.4 Tolerances

Tolerances in variatio l1 of bui lding dirnensians should nat exceed:

Plumb: walls and columns t in . in 10 ft , i in. JIl one storey or 20 ft , and t in. in 40 ft or more.

FIGURE 8- Test on prism for each 5000 rt 2 of structural br ick masonry wall.

LereI: sills, lintels, parapels, ar canspicuollS lines t in. in any bay or 20 ft , and -!- in. in 40 fL or more. Thicklless: walls and columns, rninus t in ., plus -1 in . Locatioll ill p/ali: colurnns, walls and partitions, ! in . in . 20 ft or any bay, and t in. in 40 flor more (Figures 9 and 10).

3.5 Metal

P/acemellt o/ reillforcing slee/ bars shou ld pravide a mi nirnum clear distance between parallel bars, except in colurnns af not less than lhe nominal diameter of the bars, It times lhe rnaximum size of lhe coarse aggregate used in lhe grout, ar 1 in . In columns lhe clear distance belween longitudinal bars should be nol less lhan I-!­times lhe bar diameter. I t times the maximum size af lhe coarse aggregate used, or I-!- in.

Steel cOl'erage (distance between reinforcing and face of masonry) sho uld be provided as required by the draw­ings or specificatians, but not less than i in. (Figure 11). Anchors and lies shou ld be centrally placed and should exlend imo each wylhe of masonry at leaSl I in . measured perpend icular to lhe wylhe (Figure 12). Melai ties should be placed perpendicular lo the plane af lhe \Vali. Diagonal placement of ties is improper.

3.6 \Valls

Corbelled ... olls shou ld meet lhe following requirements: Tn non-reinfa rced brick masonry lhe maximum hori­zo ntal projection of corbelling from the plane of the wall

c. T. Grimm and R. D. Halsell 341

-

): /

FIGURE 9- lf colurnns are QUI of position Of oul of plumb OU(­ward, struclurally inadequate anchorage may oecur.

FIOURE 10- lf colurnns are oul of position or oul af plumb oul­ward, cutting brick may be required.

should not exceed one-half of the wall thickness for so lid walls or one-half or the wythe thickness for cavity wall,. The maximum projection af one unit should not exceed one-halftheheight ofthe unit norone-third ofits bed depth.

Supporl for walls during construction should be adequate to resist wind.

Bearing or concentrated loads should extend onto the masonry at least 3 in.

BOllding anchorage and tying of walls should be in accordance with the plans and specifications. Size and spacing or these items is especially important (Figure 13).

Chases and recesses not shown on the plans should not be permitted.

Proteclion of the top of the wall from precipitation

FIGUR E [l-Cavity wall with properly placed continuous metal J t ties and joim reinforcement.

FIGURE 12-Metal tie is too narrow for lhe wall width.

should be provided at the end of each work day (Fig­ure 14).

3.7 Cold Wealher

Cold weather construction requirements should be as follows: No protection is required when the air tempera­ture is above 4°C.

Construction requirements (masonry being worked on):

Air temperature 4° to ooe: Heat sand or mixing water to minimum of 21 °C and maximum of 71 °C.

342 Quality Contrai of Brick Masonry =Construction in the USA

FIGURE O - Slrap anchors as required by lhe job specifications should bc embedded in mortar.

Air temperalure 0° to - 4°C: Heat salld 3nd mixing water to minimum af 2 JoC and maximum cf 71 °C.

Ai,. temperatllre _ 4° 10 - 7°C: Heat sand and mixing waler to mini mUlTI af 21°C and maximum af 71 °C. Use sa lamanders 011 other SQurccs cf heat 011 bOlh sides af walls under cOl1struction. Employ windbreaks when wind velocity is in excess af 15 mijes/h.

Air temperalure-7°C and belo)\!: Heal sa nd and mixing water to minimum af 21 °C and maximuITI af 71 oCo Provide cnclosure and auxiliary heat to maintain air temperature above O°C. Temperature af units when laid shall be nol less lhan - 7"C.

Protection requirements (completed masanry ar secl ions nol being worked on)

Mean daily air lemperalllre 4° TO DOC: Protect masonry from rain OI' snow for 24 h.

Mean daily air lemperawre DO lo - 4°C: Completely cover masonry for 24 h.

Meall daily air femperafltre _ 4° 'o _ 7:JC: Completely cover masonry with insulating blankets for 24 h.

Mean daHy air temperatllre -1°C and belo\\': Maintaill masonry temperalure above Doe for 24 h by enclosure and supplemenlary heal , by eleelrie healing blankels, infra-red heat lamps or other approved method. 11

3.8 Flashing and Coping

Flashing and coping should be installed without punctures and lapped as speeified.

3.9 Furring

Furring of lhe lype and size speeified should be firmly allaehed lo walls.

3.10 Non-destructive Testing

Non-destructive testing of brick masonry walls in place

FIGURE 14- Cover should exlend 2 rt over the walJ and be weighled down .

may be aeeomplished by sonie or X-ray leehniques. Allhough these methods will undergo further refinement, lhe feasibility of deleeling internai eraeks, voids and ot her defects in the grout cores of sl ructural masonry walls by ultrasonie and radiographie methods has already been confirmed and su itable commercially available equipment has been identified. 12.1J

REFERENCES I . AMERICAN SOCtETY FOR TESTI NG ANO MATERIALS. Facing

Brick (Solid Masonry U nits Made rrom Clay o r Shale). ASTM C216-66.

2. AMERICAN SOCII:TY fOR. TESTI NG ANO MATERIALS. Sampling and Tesling Brick. ASTM C67- 69.

3. SINHA, B. r . and H ENORY, A . W. , Further Investigation ar Bond Tension. Bond Shear and lhe EfTect of Prccomprcsslon on lhe Shear Strength or Model Brick Masonry Couplcls. B. Cera"'. R. A. Tech. Note 80, 1966.

4. AMERICAN SOCIETY FOR TESTlNG ANO MATERIALS, Porlland Cemen!. ASTM C150-61.

5. AMERICAN SOCIETY FOR TESTING ANO MATERIALS, Quicklimc ror Slructural Purposes. ASTM C5- 59.

6. AMERICAN SOCIETY FOR TESTING ANO MATERIAlS, Hy dr:ued Lime for Masonry Purposes. ASTM C207-49.

7. AMERICAN SOCIETY FOR TESTING ANO MATERIAlS. Aggregale ror Masonry Mortal'. ASTM CI44-69.

S. AMERICAN SOCIETY FOR TESTING ANO MATERIAlS, Aggregales ror Masonry Orou!. ASTM C404- 6 1.

9. Ai\1ETl.I CAN SOCIETV FOR T ESTING ANf'} MATFRIALS. Slump ror Portland Cernenl Concrete. ASTM C I43- 66.

10. STRUCTURAl CLAV PRODUCTS I NSTlTUTE. Build ing Code Requirclllenls ror Engineered Brick Masonry. August , 1969.

11 . STRUCTURAL CLAY PRODUCTS I NSTlTUTE, Co ld Wcather Mas­onry Construction. S .c. P./. Tecll . Nore I A. January, 1968.

12. BENJAMIN, J. R. and WILUAMS, H. A. , Radiographic Inspcction of Rcinrorced Grouted Briçk Masonry. Stanford University, Septcmber. 1958.

13. AEROJET- GENERAL CORPORATION, lnvcstigation of Sonic Tcsting of Masonry Walls. Sacramento, Calir., A.G.c. , October, 1967.