Presentation on theme: "Tolerances and Price Impacts Presented by:- Er. Bhagawan Shrestha."— Presentation transcript:
Tolerances and Price Impacts Presented by:- Er. Bhagawan Shrestha
Construction Control Testing/Process Control Testing Unless otherwise directed, values given in these Specifications are minimum values for the properties of materials and the workmanship. They shall be considered satisfactory, if all results of the tests, taken at the frequencies specified, are at least equal to the values given in the relevant Section of these Specifications
Tolerances (contd.) In the Specifications, minimum numbers of tests to be conducted for checking the construction tolerances (Surface levels, thickness, width, smoothness, compaction etc) have been provided in relevant section of the Specifications.
Tolerances (contd.) Where any tolerances are exceeded, the Contractor shall assess the full extent of the area which is out of tolerances and shall make good the surface of the pavement course, earthworks or formation in the manner described in Section 1100.
Tolerances (contd.) (a) Horizontal Alignments: Horizontal alignments shall be determined from the centreline of the pavement surface as shown or calculated from the Drawing. The centreline of the pavement surface as constructed, and all other parallel alignments, shall be correct within a tolerance of 13 mm there from. (b)Thickness of Pavement Layers The average thickness of any pavement layer measured at five conjugative points at every 20m in any Section shall not be less than the thickness specified nor more than 120% of the thickness specified or ordered by the Engineer. The thickness of the pavement layer measured at any point shall have tolerance of + 25 % and - 2 % of the thickness specified.
Tolerances (contd.) (c)Surface Levels of Pavement Layers and Formation The level measured at any point on the surface of a pavement layer to the formation level shall not deviate from the corresponding level calculated from the Drawing by more than the tolerances shown in Table For checking compliance with Table 11.1 measurements of surface levels shall be taken at points selected by the Engineer at 12.5m centres longitudinally and at 2m centres transversely. (d)Surface Regularity The surface regularity of pavement layers and the formation shall be tested at points decided by the Engineer with a rigid, steel straight-edge of 3 m length placed parallel to or at right angles to the centreline of the road. The maximum allowable deviation of the surface below the straight-edge shall not deviate from that shown on the Drawing by more than the tolerances shown in Table 11.1.
Tolerances DescriptionTolerances Horizontal Alignments ± 13 mm Thickness of pavement layers Avg. thickness measured at 5 conjugative pts at every 20m in any section – 0.00 and +20% of thickness specified Measured at any pt. -2% and +25% of thickness specified Cutting & embankment slopes and Width of cuttings and embankments ±200mm for cutting and +50mm for embankment Depth of side drains±25mm
Tolerances (contd.) Layer Level mm Straight edge mm Slope or Crossfall % Bituminous Wearing Course 10 6* 0.25 Bituminous Binder Course 10 6 0.25 Base 10 6 0.25 Subbase 0.50 Gravel Wearing Course 0.50 Formation (subgrade) 0.50 Table11.1:Tolerances for Level And Surface Regularity
Tolerances (contd.) * In case of asphalt concrete surface it shall be 4mm. The tolerances for level and surface regularity as given in above table shall be applicable only for New construction, Re-construction and Rehabilitation works and not applicable in case of resealing by surface dressing / sand seal / slurry seal in existing paved surfaces.
Tolerances (contd.) Description Tolerances for spray rates of Bit. binder Tolerances for application rates of Agg/chips width Prime coat and tack coat Across width of each spray run For each single run of spray ± 5% of rate ordered ± 0.03l/sq. m. of specified rate Surface dressing Across width of each spray run For each single run of spray ± 5% of rate ordered ± 0.03l/sq.m. of rate ordered ± 5% of rate ordered Avg. overall width measured at six equidistant pts over a length of 100m at least equal to width specified or instructed. At no point distance between c/l and edge of surface dressing be narrower than that instructed/ specified by more than 13mm.
Tolerances (contd.) Penetration Macadam- Semi- grout Across width of each spray run For each single run of spray ± 5% of rate ordered ± 0.03l/sq.m. of rate ± 5% of rate ordered Sand seal Across width of each spray run For each single run of spray ± 5% of rate ordered ± 0.03l/sq.m. of rate ± 5% of rate ordered Slurry seal Across width of each spray run For each single run of spray ± 5% of rate ordered Not less than rate ordered
Tolerances (contd.) For Asphalt Concrete, Sand Asphalt, Emulsion Aggregate Mix and Cold Asphalt, the composition of the mixture as determined from the laboratory and site trials should be maintained within the following tolerances, per single test:- (a)Bitumen content : 0.3% of (Total weight of bitumen in total mix) (b)Aggregates (i) Passing through 10 mm sieve and larger sieves: 6%of X (ii) Passing through 10 mm sieve and retained on 1mm sieve : 4% of X (iii) Passing through 1 mm sieve and retained on mm sieve : 3% of X (iv) Passing through mm sieve : 2% of X Where X: Total wt of dry aggregates including mineral filler
Tolerances (contd.) Number of batchesMaximum coefficient of variation Ordinary concreteHigh quality concrete After 20 tested batches18%15% After 50 tested batches15%12% Section Concrete for structure provides the tolerances for the concrete works which are as follows: In the case of Early works test cubes, no single result (average of 3 cubes) should be less than the characteristic strength (f ck ) and the avg. of 3 consecutive results should not be less than characteristic strength (f ck ) + 4 (N/mm 2 ). When at least 20 consecutive results on tested batches are available for any class of concrete mixed in any one plant, no single result should be less than characteristic strength (f ck ) – 4 and the average of any group of three consecutive results should not be less than characteristic strength (f ck ) + 4 (N/mm 2 ). In addition the Coefficient of Variation shall be less than the figure given below:
Mechanically Stable Sub base (Example) TestsOne test in every Min. no of tests per section Materials: Gradation Plasticity Index Maximum Dry Density and Optimum Moisture Content Workmanship: Field Density and Moisture Content 200 m 3 or part of it and change in source " " 1000 m 3 " " " 500 m Construction Tolerances: Surface Levels Thickness Width 10 m 25 m 200 m Table 12.2 : Minimum Testing Frequency
Tolerances (contd.) The work is considered conforming to the requirements of the Contract if the entire quality assurance tests are performed with the frequency as stipulated in the Technical Specifications and the results fall within the tolerances stipulated in the Technical Specifications.
Sub – Standard Payment The Standard Specifications for Road and Bridge Works stipulates the Sub – Standard Payment for the Cement Masonry works and Cement Concrete works only.
Sub – Standard Payment Concrete and Cement masonry works not meeting the requirements of the relevant Specifications (termed as substandard concrete) shall be paid as substandard work provided it is accepted by the Engineer as substandard work. For the acceptance of such work the Engineer may require further investigation and/or tests which the Contractor shall conduct at his own cost. Acceptance or rejection of such work is the sole responsibility of the Engineer and his decision in this respect shall be the final and binding upon the Contractor.
Sub – Standard Payment If accepted as substandard work the payment for such work shall be made at the contract unit rate reduced by the formula given below Design strength - Observed strength Percent of reduction, P = X 100 Design strength
Sub – Standard Payment But the limit of non compliance is not specified and solely given the authority to the Engineer for decision. The Engineer may conduct the Non destructive tests for the conformation of the strength, homogeneity and durability at the cost of the Contractor to accept the work as sub standard.
Sub – Standard Payment If tolerances exceed the limits specified in the Contract/Standard Specifications for road and Bridge works in all other works except the cement concrete and cement masonry works, then the work should be rejected and rectified and /or reconstructed as per the instruction of the Engineer and no adjustment for contract price should be done.