SANS 10120-3 G-1982 Code of practice for use with standardized specifications for civil engineering construction and contract documents Part 3 Guidance for design Section G Concret.pdf

1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. SABS 0120 : Part 3 Section G-1982 Concrete (structural) PART 3 : GUIDANCE FOR DESIGN SECTION G CONTENTS Page Number PRE-TENDER CONSZDEWPIONS 1 InvestAgat

4、ions . 1 Wdter l Aggregates 1 Concrete nix proportions . 1 Administration . 1 Prescribed mix 1 Documentation . 1 Special conditioris of contract . l Expansive alkali-aggregate reaction 1 Concrete exposed to sulphate attack 1 Erawings and berldinq schedule details for reinforcement 2 Tolerances . 2 S

5、cheduling . 2 Grouting to machine and structural bedplates . 3 DESIGX REQIJIREMEHTS 3 Particulal Problems 3 Concrete subject to alkali-aggregate reaction or sulphate attack . 3 Spacing of bars to be fixed 4 Slab thickness and corlcrete cover 4 Concrete cover over binding wire . 4 Concrete cover incr

6、eased for exposed aggregate finishes 4 Designated joints and length of main reinforcement . 4 Pipes and coilduits 4 Design of Concrete Mixes . 4 General 4 Degree of control 4 Mix Design Procedure . 6 General 6 Procedure and example for design . 6 APPLICABILITY OF OTHER SAHS CODES 9 TEST PROCEDURES 9

7、 QUALITY CONTROL AND OTHER CONSIDERATIONS . 9 General 9 Disputes. Mediations. Arbitrations. and Court Cases 9 Scheduled quantities of reinforcicg bars . 9 Flatness o: plane surface 9 Court cases . 9 First Revision August 1982 This section of the code supersedes SABS 0120 : Part 3 : Section G-1982 Ap

8、proved by the COUNCIL OF TilE SO!JTM AFRICAN BUKEAU OF STANDARDS SABS 0120 : Part 3 Section G-1982 Concrete (structural) SABS l200 G : CONCRETE (STRUCTUXAl.) NOTE: The clause numher(s) given at tlw beginning or after the heading of a clause idare, unless otherwise stated, the nunber(s) of the releva

9、nt clause(s) of SABS 1200 G. PRE-TENDER COtJSIUEPATIONS TPJVESTIGATIONS Ma:.er (subclause 3.3). If doubt exists as to the suitability of water for concrete making, particularly in remote areas ancl areas where the water is brackish, test the available water during pre-tender irvestigations. In these

10、 tests, compare the 28-d strength of mortar cubes made with portland cement and the water in question with the strength of similar cubes made with the same cement and water of known purity. The water may be considered fit for use if the average 28-d strength of 3 mortar cubes made with the suspect w

11、ater is at least 90 % of that of 3 similar cubes made with water of known purity. Aqgregates (Subclause 3.4) Consider, and investigate on the site of the works where necessary, the aggregates that will be most readily and economically available. Utilize the results of such investigations in the proj

12、ect specification (see 1.1.3, 1.2.1 and 1.3.2 below). Note that Appendix C of SABS 1083) identifies characteristics of certain fine and coarse aggregates that are normally not acceptahlc but are none the less acceptable for use in particular circumstances and are frequently to be preferred on the gr

13、ounds of economy. Where such aggregates are preferred, say so in the project specification. I.ocal fine aggregates from the Orange River in the Northern Cape and various sources in the Orange Free State are frequently unacceptable tor strength concrete. If such aggregates are unacceptable say so in

14、the project specification (see 1.2.1 and 1.3.2 below), because the difference in cost between local sand and sand complying with the requirements of SABS 1083) may be significant. Local aggregates which are acceptable are the follcwing: a) Fine aggregate from Port Elizabeth having a fineness modulus

15、 of between 1.2 and 1,6; b) fine aggregate from Cape Town and environs that is hard sand of shell origin; C) coarse agqregate from the Reef area, consisting of crushed mine rock; d) coarse aggregate from the Pretoria area, consisting of norite. Concrete Nix Proportj%s. - a) Prescribed mix concrete (

16、Subclause 5.5.1.6). In order to be in a position to specify materials and the mix(es) for prescribed concrete, investigate the availability of materials in the vicinity of the site and, unless satisfactory evidence is available from previ.ous use of the materials and the proposed mix(es), arrange fo

17、r preliminary tests to be carried out. Arrange also for such tests to be carried out during the progress of the work to check that the specified mix proportions are suitable. (See Subclause 2.1.1 (d) of Section G of Pxt 5 of the code.) b) ? 5) Strength (undue variations in member size, excessive cov

18、er to reinforcement, and excessive bow in struts are among the deviations which may cause a reduction in strength); c) Fit (when prefabricated units are required to fit together or when machinery is to be installed, the tolerances have to be carefully considered); d) L,egal (structures may not encro

19、ach on neighbouring property). Bow, camber, twist, and squareness_ (Subclause 6.2.3(d). Tolerances for bow, carcber, twist, and squareness are usually specified where prefabricated components are required to fit together. If necessary, make reference to SABS 0155). Scheduling Reinforcing bars: Measu

20、rement and rates (Subclauses 8.1.2.1 - 8.1.2.3ia) a) The recent rapid escalation and the expected future rises in the price of reinforcing steel have resulted in such a disproportionate difference in the prices per ton of steel bars of different sizes (diameter or side,.as relevant) that pricing on

21、the basis of the four groups of sizes formerly used is no longer fair t.o either the employcr or the contractor. On the other hand, except in the case of bridges, difficulty is generally experienced in providing reasonably accurate detailed schedules of reinfor 8Ye;e for structures that have not bee

22、n detailed completely at the tender stage and, in terns of the GCC , employer can expect to receive claims when the final quantity of steel of any particular size or group of sizes differs greatly from that scheduled. 13) TO ensure that the most reasonable prices are obtained and to minimize the ris

23、k of disputes, schedu.le reinforcement as shown in Section G of Part 4 of the code (ensuring that the quantities scheduled comply with the notes given on the right-hand side of the typical schedule), and insert a special condition of contract in the contract document,such as one of the following: 1)

24、 Special Condition of Contract, to be read with 1;cc4) (in contracts other than SA Transport Services: contracts) : Clause 52. Amend Subclause (l), aluations of variations, to read as follows: “52(1) Except in the case of quantities of reinforcing steel that are stated in the Schedule of Quantities

25、to be “Extra-over the basic Contract Price for 25 mm reinforcing steel, and to be provisional in terms oE the Special Conditions of Contract“, the Engineer shall detormine the amount (if any) to be added to or deducted from the sum named in the Tender in respect of any extra or additional work done

26、or work omitted by his order. All such work shall be valued at. the rates set out in the Contract if in the opinion of the Engineer the same shall be applicable. If the Contract shall not contain any rates applicable to the extra or additional work, then the Engineer in agreement with the Contractor

27、 shall fix such prices so far as possible consistent with the rates set out in the Contract as in the circumstances he shall think reasonable and proper.“ Amend Subclause (2), Authority of Engineer to fix rates, to read as follows: “(2) Provided that if the nature or amount of any omission, addition

28、, increase or decrease in quantity, whether ordered or arising under Subclause 5l(2) relative to the nature or amount of the whole Contract or part thereof, shall be such that it results in a change iri method or scale of operation, process of construction or source of supply, such as in the opinion

29、 of the Engineer renders the rate or price contained in the Contract for any item of the Works by reason of such omission, addition, increase or decrease of quantity unreasonable or inapplicable, the Engineer i.n agreement with the Contractor shall fix such other rate or-price so far as possible con

30、sistent wi.th the rates or prices set out in the Contract as in the circumstances he shall think reasonable and proper. Provided also that no increase of the Contract Price under Subclause (1) of this Clause or variation. of rate or price under Subclause (2) of this Clause shall be made unless, as s

31、oon as is practicak)le, and in the case of extra or additional work before the commencement of the work or as soon thereafter as is practicable, notice shall have been given in writing a) by the Contractor to the Engineer of hi.s intention to claim extra payment or a varied rate or b) by the Enginee

32、r to the Contractor of his intention to vary a rate or price as the case may be. Provided also that no increase of the Contract Price under Subclause (1) of this Clause or variation of any rate or price under Subclause (2) of this Clause shall be made where the quantities of reinforcing steel measur

33、ed in the Works vary from those stated in the Schedule of Quantities uzder items scheduled as “Extra-over the basic Contract Price for 25 mm reinforcing steel and to be provisional in terms of the Special Conditions of Contract“, regardless of the magnitude of the variation of such quantities.“ -W-

34、3) Accuracy in building. 4) General conditions of contract; see footnote to Subclause 1.3.1 of Section A. SABS 0120 : Part 3 Section G-1982 Concrete (structural) 2) Special Condition of Contract far SA Transport Services contract5) : Clause 31.2. Amend Clause 31.2, Dlfffr-ce in final measured3:antit

35、y more than 20%, to read. as follows: “Except that, regardless of the magnitude of the variation of quantities, no adjustment of the scheduled rate will be made in the case of quantities of reinforcing steel that are stated in the Schedule of Quantities to be “Extra-over the basic contract price for

36、 25 mm reinforcing steel and provisional in terms of the Special Conditions of Contract“, where the final measured quantity of any scheduled item differs from the estimated quantity by more than twenty (20) per cent, either the Enylneer or the Contractor may request an adjustment of the scheduled ra

37、te for the particular item and, where the quantities are increased, in respect only of that portion of the final measured quantity which falls outside the limits of the twenty (20) per cent difference. The Engineer will submit full details with his recommendatior: to the Chief Civil Engineers deputy

38、.“ Welded mesh reinforcement (Subclause 8.1.2.2(b). Where the project involves large quantities of welded mesh, include in the reinforcement schedule lists of the numbers of sheets required, and set out sheets of standard and non-standard sizes separately. Grouting to Machine and Struct.urc71 Bedpla

39、tes (Subclause 5.5.13). Where grouting to machine and - - -p structural bedplates is required, include suitable project specification clauses based on the example given in Subclause 3.2.14 of Section G of Part 2 of the code and the examples given in Subclause 3.1.13 and the recommendations given in

40、Subclause 3.2.24 of Section G of Part 5 of the code. DESIGN REQUIREMENTS PARTJCIJLAR PROBLEMS Concrete Subject to Alkali-Aggregate Reaction or Sulphate Attack Alkali-aggregate reaction. See 1.3.2 above. - - Concrete exposed to sulphate attack. When selecting a w/c rati.0 for design purposes in circu

41、mstances where the concrete will be exposed to sulphate attack, make provision in the design for it to be protected by adopting the applicable of the measures set out in 1.3.3 above and in Table 1 (bearing in mind the NOTE (a)-(e) below and extrapolating for higher degrees of concentration). TABLE 1

42、 : MAXlMUM WATER/CEI“.EN RATIOS FOR CONCRETE EXPOSED TO SULPHATE ATTACK Concentration of sulphate as SO 3 Degree of sulphate concen- tration Irl soil In ground water Maximum w/c ratio, by mass Recormended type of cement Total SO 3 % by mass SO in 2:1 3 water extract, 9/e Ordinary portland or portlan

43、d blast- furnace cement Less than 0,2 Less than 30 Ordinary portland or portland blast- furnace cement 0,2 and up to and including 0,5 30 and up to and including 120 Sulphate-resisting portland cement More than 120 and up to and including 250 More than 0,5 and up to and including 1.0 Sulphate-resist

44、ing portland cement More than 1.0 and up to and includirg 2.0 More than 3,l and up to and including 5.6 More than 250 and up to and including 500 Sulphate-resisting portland cement Sulphate-resisting portland cement plus adequate pro- tective coatings Over 2,O Over 5,6 Over 500 5) E5 Conditions of c

45、ontract, published by the SA Transport Services. SABS 0120 : Part 3 Section G-1982 Concrcte !structural) PIOTE a) Determine the concentration of sulphate as SO3, using SABS Method 850. b) Table l applies wily to concrete made with aggregates from natural sources placed in near-neutral ground water o

46、f pH G-pfi 9, containing naturally occurring sulphates but not contaminants such as amoniurn salts. Do not select ordinhry portland cement for concrete to be placed in acidic conditions (pH 6 or less). Sulphate-resisting portland cement is sliyhtly more acid-resistant than ordinary portland cement b

47、ut no experience of lirge-scale use in these conditions is currently available. Supersulphated cement (which is currently not manufactured in the Republic: of South Africa) has proved to give an acceptable life in rnincral acids of pli as iow as 3,5, provided that the concrete is dense and has a w/c

48、 ratio of 0,4 or less. C) The w/c ratios given tor Degree 2 are the maxima recommended by the manufacturers. For SO3 contents near the upper limit of Derjree 2, lower w/c ratios are recommended. cl) Where the total. SO3 concentration (Column 2) exceeds 0.5 %, a 2:l water extract from the soil may re

49、sult in d lower site classi.fication if much of the sulphate is present as low-solubility calcium sulphate. C) Where the concrete i:. subject to severe stresses or is exposed to water, e.g. thin sections, sections under. hydrostatic pressure on one side only, sections partly immersed, give consideration to a decrea2.e in tile w/c ratio recommended and, if necessary, increase the cement content to ensure the degree of workability needed for full compaction and thus minimum pcrrneability. Spacinq of Bars to be Fixcd (Subclause 5.1.2). Note that the maximum