IRC 44:2017 offers detailed instructions for developing cement concrete mixtures tailored for pavement construction across India. It addresses the principles of mix proportioning, material selection, and modifications to achieve desired workability, strength, and longevity, including special guidance on high-strength and pervious concrete mixes. This code is a vital reference for engineers and professionals involved in designing and building robust concrete pavements.
Overview
IRC 44:2017 offers detailed instructions for developing cement concrete mixtures tailored for pavement construction across India. It addresses the principles of mix proportioning, material selection, and modifications to achieve desired workability, strength, and longevity, including special guidance on high-strength and pervious concrete mixes. This code is a vital reference for engineers and professionals involved in designing and building robust concrete pavements.
Audience
Contents
Structure
This section defines the extent of IRC 44, detailing specifications for concrete materials and mix design tailored to road pavements, including high-strength and pervious concrete types. It specifies testing parameters such as free moisture content in aggregates and sieve analysis for coarse aggregate classifications, categorizing them into three size fractions with corresponding passing percentages. The scope encompasses definitions, materials, and mix design methodologies applicable to durable highway concrete construction.
This chapter establishes the standardized terminology and abbreviations used throughout the code, referring to relevant IS codes for comprehensive definitions. It lists common abbreviations for cementitious materials, admixtures, and concrete types, ensuring consistent communication within the field of concrete pavement design.
This part outlines the essential materials used in pavement concrete, including types of cement like OPC, PPC, and PSC, and chemical admixtures such as HRWRA and HRWRAS to enhance workability and strength. It discusses key parameters like water-cement and water-cementitious material ratios that affect durability and performance. The section covers specifications for pavement quality concrete and references the use of recycled aggregates and ready-mix concrete along with moisture state considerations.
This chapter describes core principles for determining concrete mix proportions, including grade designation, cement type, aggregate size, minimum cement content, maximum water-cementitious ratio, target slump, supervision level, aggregate characteristics, and admixture type. It provides material property values such as specific gravity and water absorption for cement, silica fume, and aggregates. The section also outlines adjustments for water content and admixture dosage based on trial mixes and transport considerations.
This portion presents a step-by-step method for proportioning concrete mixes, involving calculations of aggregate volumes from specified tables, computation of absolute concrete volume accounting for air content, and determination of component volumes and masses using specific gravities. An illustrative example demonstrates the calculation process for a particular aggregate size and water-cement ratio, ensuring accurate proportioning for desired concrete properties.
This section provides formulas and criteria for designing pervious concrete mixtures, including typical void content, paste volume, and aggregate proportions based on target permeability rates. It explains how to calculate cement and aggregate quantities considering moisture conditions and presents an illustrative mix design for M10 grade pervious concrete. Water permeability testing methods and moisture adjustment procedures are also described to ensure performance and durability.
This part focuses on controlling concrete workability and consistency through slump and water content adjustments, supported by trial mixes and admixture dosing. It specifies target slump ranges, recommended water contents for different aggregate sizes, and provides guidelines for modifying water content based on aggregate shape and desired slump. Use of chemical admixtures to reduce water demand and maintain workability during transportation is emphasized.
This chapter explains the calculation of target strength to ensure the specified concrete strength is reliably achieved, accounting for variability through standard deviation. It presents the formula for target strength as the sum of characteristic strength and a multiple of standard deviation, referencing tables for typical standard deviation values. The approach supports quality assurance in mix design.
This section addresses factors influencing concrete durability, including aggregate moisture content management, adjustment of aggregate and water quantities, and water permeability testing procedures. It details specimen preparation for permeability tests and gradation requirements for aggregates to ensure long-lasting pavement performance.
This segment highlights the importance of conducting trial mixes to validate and refine concrete proportions. It outlines a sequence of trial mixes with variations in water and admixture content, and water-cement ratios to assess workability and strength outcomes. Moisture corrections for aggregates and adjustments for slump and admixtures are detailed to optimize mix design.
This portion provides guidance on incorporating mineral admixtures such as fly ash, metakaolin, GGBFS, and silica fume within specified limits to enhance concrete properties. It discusses the influence of admixtures on water demand and workability, with recommendations for dosage adjustments based on material availability and performance requirements.
This chapter presents quality control measures including moisture content verification and sieve analysis for aggregates in accordance with specified gradation zones. It emphasizes the necessity of confirming aggregate quality and grading to ensure compliance with pavement concrete requirements.
This section covers adjustments in concrete mix to accommodate transit and placement challenges, such as increasing initial slump to counter slump loss during transportation. It outlines calculation methods for component volumes and aggregate masses, with examples to illustrate mix design accounting for transport conditions. The role of chemical admixtures in maintaining workability is also discussed.
While the code does not explicitly detail safety and environmental formulas or tables, this section acknowledges standard construction practices for safety, dust control, noise management, and waste disposal. It also references tables that support material reliability, indirectly contributing to safety and environmental performance.
This final part lists key reference tables and annexures that provide additional data and examples for mix design, material properties, and quality control. Included are standard deviations for strength parameters and detailed sieve analysis data, supporting accurate and reliable pavement concrete design.
Frequently Asked
The recommended volumes of coarse aggregate per unit volume of total aggregate vary depending on the nominal maximum size of the coarse aggregate and the grading zone of the fine aggregate. For standard concrete grades with a water-cementitious material ratio of 0.30, Table 17 (Clause 5.3.7) specifies volumes for crushed angular aggregates under saturated surface dry conditions. Adjustments are made with changes in water-cement ratio by increasing or decreasing coarse aggregate volume by 0.01 for every 0.05 change in w/cm. For higher water-cement ratios such as 0.50, Table 11 (Clause 4.4.5.1) provides correspondingly lower volumes. Aggregate shape and combined gradation may require further modifications to meet overall grading limits.
Target compressive strength is calculated to ensure that the majority of test results exceed the specified characteristic strength. This is done by adding 1.65 times the standard deviation to the characteristic strength, following the formula: f = f_ck + 1.65 × S, where f_ck is the characteristic compressive strength and S is the standard deviation. For instance, with f_ck = 10 N/mm² and S = 2.5 N/mm², the target strength becomes 14.13 N/mm². This methodology provides a margin to account for variability and maintain quality.
To achieve target workability, adjustments in water content and chemical admixture dosage are necessary. Base water content depends on aggregate size and angularity, with values like 208 kg/m³ for 9.5 mm aggregates at 50 mm slump. For less angular aggregates, water content can be reduced by 10-20 kg/m³. Water content should be increased by roughly 3% for every additional 25 mm slump required. Chemical admixtures such as water reducers and superplasticizers can decrease water demand by 5-10% and up to 20% respectively. Trial batches and slump testing are critical for fine-tuning these adjustments, especially for ready-mix concrete with transit time considerations.
The code provides comprehensive guidance on pervious concrete mix design through examples and detailed procedures, including the use or omission of fine aggregates. It emphasizes conducting trial batches with aggregates in saturated surface dry condition, adjusting water and aggregate quantities based on moisture content, and targeting permeability and strength criteria. An illustrative M10 grade pervious concrete mix includes OPC 43 grade cement, 9.5 mm maximum aggregate size, and a water-cement ratio of 0.38, achieving a minimum percolation rate of 350 mm/min. Water permeability testing methods are specified to verify performance, ensuring both hydraulic and structural requirements are met.
Fly ash conforming to IS:3812 Grade I can be used as a partial cement replacement up to 25% by mass of cementitious materials, ensuring uniform blending and approval by the Engineer-in-Charge. Metakaolin usage is recommended up to 20%. For high-strength concrete mixes, recommended dosages include fly ash at 15-25%, ground granulated blast furnace slag at 25-50%, and silica fume at 5-10%. These supplementary materials must comply with IRC:15 limits and be accounted for in mix design to mitigate risks such as shrinkage, thermal cracking, and alkali-silica reactions.
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