PQC Methodology
Pavement Quality Concrete (PQC) M40 – Complete Construction & QA/QC Guide Pavement Quality Concrete (PQC) M40: Complete Construction & QA/QC Guide Pavement Quality Concrete (PQC) of M40 grade forms the structural load-bearing layer in rigid pavements of National Highways. This guide provides a detailed overview of materials, mixing, placement, curing, joint detailing, dowel and tie bar installation, and quality assurance/quality control (QA/QC) procedures. It also highlights common issues, their solutions, and aligns with MoRTH Section 602 and IRC standards. For more insights, see the main pillar page on Rigid Pavement Components. Applicable Standards Reference Documents S. No. Document Description 1 Contract Agreement 2 IRC: SP: 84-2014 3 Ministry of Road Transport & Highways Specifications (MoRTH – 5th Revision) 4 Relevant Drawings 1. Understanding PQC PQC is a high-strength concrete layer designed to transfer traffic loads directly to the subgrade through slab action. It is especially suited for highways with heavy traffic, high axle loads, and long-term durability requirements. Benefits of PQC include: Exceptional flexural strength and load transfer capacity Durable surface resistant to rutting and deformation Expected service life of 30–40 years Reduced long-term maintenance requirements Resistance against oil, water, and temperature-induced damage 2. Material Specifications for M40 PQC Materials 1. Source of Materials The Contractor shall indicate to the AE the source of all materials to be used in the concrete work with relevant test data sufficiently in advance. 2. Cement Any of the following types of cement capable of achieving the design strength may be used: S. No. Type of Cement Conforming To 1 OPC 43 / OPC 53 Grade IS:269 2 Portland Slag Cement IS:455 3 Portland Pozzolana Cement IS:1489 (Part-I) 3. Admixtures a. Chemical Admixtures Admixtures conforming to IS:9103 and IS:6925 shall be permitted to improve workability of concrete or extension of setting time, on satisfactory evidence that they will not have any adverse effect on the properties of concrete with respect to strength, volume change, durability and shall have no deleterious effect on steel bars. b. Mineral Admixtures Fly ash up to 20% by weight of cementitious material may be used in Ordinary Portland Cement 43 or 53 Grade as part replacement of cement provided uniform blending with cement is ensured. The fly ash shall conform to IS:3812 (Part-I) and GGBFS shall conform to IRC:15-2017 / IS:16714-2018. Site mixing of fly ash shall be permitted ensuring availability of equipment at site for uniform blending through specific mechanized facilities with automated process control like batch mix plants conforming to IS:4925 and IS:4926. 4. Aggregate Aggregates for pavement concrete shall be natural material complying with IS:383 but with Los Angeles Abrasion Test value not exceeding 35 percent. The limits of deleterious materials shall not exceed the requirements set out in Table 600-2 of MoRTH Specifications. a. Coarse Aggregate The maximum size of coarse aggregate shall not exceed 31.5 mm for pavement concrete. The Los Angeles Abrasion Value shall not exceed 35. The combined flakiness and elongation index of aggregate shall not be more than 35 percent. b. Fine Aggregate The fine aggregate shall consist of clean natural sand or crushed stone sand or a combination of the two and shall conform to IS:383. The fine aggregates shall have a sand equivalent value of not less than 50 when tested in accordance with IS:2720 (Part-37). c. Combined Gradation of Fine and Coarse Aggregate The combined gradation of fine and coarse aggregates shall be as per Table 600-3 of MoRTH Specifications. 5. Water Water used for mixing and curing of concrete shall be clean and free from injurious amounts of oil, salt, acid, vegetable matter and other substances harmful to the finished concrete. 6. Steel for Dowels and Tie Bars Steel shall conform to the requirements of IS:432 and IS:1786 as relevant. Dowel bars shall conform to IS:432 of Grade-I. Tie bars shall be either High Yield Strength Deformed bars conforming to IS:1786 and Grade Fe-500 or plain bars conforming to IS:432 of Grade-I. Steel shall be coated with epoxy paint for protection against corrosion. 7. Joint Filler Board Synthetic joint filler board for expansion joints shall be used only at abutting structures like bridges and shall be of 20–25 mm thickness with a tolerance of ±1.5 mm and of firm compressible material complying with IS:1838, having compressibility more than 25%. 8. Joint Sealing Compound The joint sealing compound shall be of hot poured elastomeric type or cold polysulphide/polyurethane/silicone type having flexibility, resistance to age hardening and durability as per IRC:57. 9. Preformed Seals The pre-formed sealing material shall be vulcanized elastomeric compound using polychloroprene (Neoprene) as the base polymer. 10. Storage of Materials All materials shall be stored in accordance with the provisions of Clause 1014 of MoRTH Specifications. Proportioning of Concrete 1. Cement Content The quantity of cement shall not be less than 360 kg/cu.m for all types of cement. In case Fly Ash Grade-I (as per IS:3812) is blended at site as part replacement of cement, the quantity of fly ash shall be up to 20% by weight of cementitious material and the quantity of OPC in such blend shall not be less than 310 kg/cu.m. If GGBFS is used, minimum OPC content shall not be less than 310 kg/cu.m. 2. Concrete Strength The characteristic flexural strength of concrete for 28 days shall not be less than 4.5 MPa unless specified otherwise. Target mean flexural strength for mix design shall be: 4.5 MPa + 1.65s Where “s” is the standard deviation of flexural strength derived by conducting tests on minimum 30 beams. The water content shall be the minimum required to provide the agreed workability for full compaction of concrete to the required density as determined by trial mixes. The maximum free water cement ratio shall be: 0.45 when only OPC is used 0.50 when blended cement (PPC / PSC / OPC blended with Fly Ash or GGBFS) is used IRC:44 shall also be referred regarding selection of water-cement ratio. The ratio between the 7-day and 28-day strength shall be established for the mix to