17 Conc Structures | Precast Concrete

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  SECTION XVIICONCRETE STRUCTURES1701 SCOPE The Contractor shall construct all concrete structures shown on the Drawings.Concrete shall be proportioned, mixed, placed, finished and cured as specified inSection XV, Concrete, except as modified herein. The sequence of construction of thestructures shall be subject to the approal of the !ngineer. here the thic#ness of an$ portion of a concrete structure is ariable, it shall ar$ uniforml$ between the dimensionsshown. Cement mortar plastering is not allowed in the construction of structures, unlessotherwise specified elsewhere in these Specifications. 1702 CONCRETE CONSTRUCTION %ll concrete construction shall conform to the proisions of Section XV, Concreteand the detailed requirements of the following paragraphs. Concrete finished shall conformto &aragraph '(') and*or shall be as noted on the Drawings.%ll structures shall be built to the specified lines, grades and dimensions. Thelocation of all construction joints shall be shown on the Drawings or as approed b$ the!ngineer. Construction joints shall be constructed as shown on the Drawings. TheContractor shall place and embed or attach to each structure all timber, metal or other accessories necessar$ for its completion as shown on the Drawings or as directed b$ the!ngineer.The dimensions of each structure shown on the Drawings will be subject to changeas ma$ be found necessar$ b$ the !ngineer to adopt the structures to actual fieldconditions and conditions disclosed b$ excaation. 1703 METHOD OF MEASUREMENT +easurement for pa$ment of an$ and all classes of concrete will be made b$ thenumber of cubic meter computed to the neat lines of the structure, unless otherwisespecificall$ shown on the Drawings or specified in these Specifications. n the eentcaities resulting from careless excaation or from excaation performed to facilitate theContractor-s operations, as determined b$ the !ngineer, are required to be filled withconcrete. Such refilling will be made b$ at the expense of the Contractor. n measuringconcrete for pa$ment, the olume of all openings, embedded pipes, woodwor# and metalwor# within the concrete will be deducted. 1704 BASIS OF PAYMENT &a$ment for an$ and all classes of concrete in arious parts of the wor# will bemade at the applicable contract unit prices per cubic meter which price and pa$ment shallTSXV'  Concrete Structuresinclude cost for furnishing all materials, equipment and labor, and all operations requiredin the construction as specified under Section XV, Concrete, except that pa$ment for reinforcing bars and joint materials will be made at the applicable separate contract unit prices in the /ill of 0uantities.f during the implementation of the project, the sources of aggregates differ fromthose chosen b$ the Contractor considered in the deriation of his unit bid price for concrete, the Contractor shall not be entitled to an$ claim for unit price adjustment as aresult of such alteration of sources. 1705 CONCRETE FOR ALL STRUCTURES 1a2 Gene! The item 3Concrete for %ll Structures3 in the /ill of 0uantities include all concretein diersion wor#s 1except 4ubble +asonr$2, canal structures and road structures such assiphons, bridges, drainage culerts, road crossings, pipe crossings, ungated thresher crossings, control structures, drop structures, headgates and turnouts and all other structures not otherwise specified elsewhere in these Specifications.Small concrete structures, at the option of the Contractor, ma$ be installed as precast units proided that precast structures installed in place are equal in all respect tocastinplace construction as specified in these specifications.Concrete for diersion wor#s, canal structures and other structures will bemeasured and paid for as specified in &aragraphs '567 and '568, respectiel$. Structuresnot full$ and acceptabl$ completed will not be measured for pa$ment. &recast structuresinstalled and acceptabl$ completed in place shall be paid for as specified in &aragraph'568.%ll materials used li#e cement, admixtures, aggregates and steel reinforcing barsshall conform to the proisions of Section XV, Concrete and Section XX, 4einforcingSteel /ars, respectiel$. Classes of concrete to be used shall be those specified in theDrawings.1b2 C#$n% !n& '($n)* %ll concrete shall be cured in accordance with paragraph '(99, except thatconcrete for canal siphon shall be cured until the concrete test c$linders shall hae attaineda strength of at least 9'6 #g. per square cm. 17,666 pounds per square inch2. The Contractor shall construct expansion and construction joints at sectionsspecified on the drawings all in accordance with the proisions of paragraph '('5 andSection XX, Concrete :oints and :oint +aterials, and elsewhere in these Specifications. 170+ PRE CAST CONSTRUCTION 1a2 S,(-e !n& De*,$-)$(n TSXV9  Concrete Structures&recasting of reinforced concrete ma$ be resorted to as an alternatie to pouredinplace concrete for certain structures such as headwalls and collars, parshall flumes,turnouts, diision boxes, and other structures. Should the Contractor choose to emplo$ precast construction on these structures, he must so inform the !ngineer in writing,submitting in detail his proposed design, modifications of concrete sections, concretespecifications, reinforcements and schemes of construction of all precast units. The ;%ma$ further required the Contractor to submit all other additional informations as ma$deemed necessar$.The ;% ma$ approe the construction proposed on precasting of concrete with or without correction. The approal, howeer, does not reliee the Contractor of an$responsibilit$ if such wor# does not meet specified results.4einforced concrete pipes and concrete hollow bloc#s are not considered precastconstruction, hence, are excluded under this Section.1b2 T!n*-()$n% !n& P !,$n% !xtreme care should be obsered in handling, storing, moing and erecting toaoid crac#ing, twisting, or other distortions that would result to crac#ing or damage tothe precast concrete. &recast concrete members shall be handled, transported and erectedin an upright position and the points of support and directions of the reactions with respectto the members shall be approximatel$ the same as when the member is in final position.1c2 S!.- $n% !n& Te*)$n% The indiidual components of precast concrete structures, shall conform to theapplicable proision of Section XV, Concrete and will be subject to the usual test for reinforced concrete.1d2 Me!*#e.en) !n& P!/.en) +easurement of concrete in precast structures will be measured b$ the number of cubic meter. t shall be computed to the neat lines as if these structures were constructedto the details shown on the Drawings.The Contractor will be paid for all precast structures acceptabl$ installed or completed in place. <e shall be paid for each precast unit as if the units were constructedto the details shown on the Drawings, regardless of the actual dimensions of the precastunit. 1707 LEAN CONCRETE n the construction of siphons, the bottom of the castinplace concrete barrels will be exposed to high elocit$ flow of seepage during pouring which will absorb or wash outthe cement in the concrete poured. To minimi=e the effect of seepage, a blinding concreteTSXV7  Concrete Structureswith minimum strength of 56 #g*sq. cm. shall first be poured to the lines, grade anddimensions on which the barrels will be constructed as shown on the Drawings.>ean concrete shall be measured and paid for as specified in paragraphs '567 and'568, respectiel$. 170 STAFF GAGES The Contractor shall install two ertical staff gages, one upstream and onedownstream, in all parshall flumes and turnouts with ale structures and in all chec# structures in the laterals as shown on the Drawings or as directed b$ the !ngineer. The porcelain plated or enameled steel staff gages and other materials and accessoriesnecessar$ for the installation shall be supplied b$ the Contractor.nstallation of staff gages will not be measured for pa$ment including all thechannels, anchors, anchor bolts and other metal materials necessar$ to install the staff gages at the parshall flumes and chec# structures. The cost of installation and other materials supplied b$ the Contractor shall be included in the contract unit price for concrete in the respectie structure where gages are required. TSXV8
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