UNIT - 01
Cement: Composition and Grades
Chemical Composition of Cement
Portland cement is primarily made by heating a mixture of limestone (calcium carbonate) and clay (silica and alumina) to form clinker, then grinding it with gypsum. Key oxides in cement include:
Calcium oxide (CaO): 60–67%
Silica (SiO₂): 17–25%
Alumina (Al₂O₃): 3–8%
Iron oxide (Fe₂O₃): 0.5–6%
Gypsum (CaSO₄·2H₂O): 3–5%
These proportions control setting behavior, strength development, and heat of hydration.
Grades of Cement
In India, ordinary Portland cement is classified by its minimum 28-day compressive strength:
| Grade | 28-Day Compressive Strength (MPa) | Typical Use |
|---|---|---|
| 33 (OPC 33) | ≥ 33 | General concrete work, non-critical |
| 43 (OPC 43) | ≥ 43 | Reinforced concrete, pavements |
| 53 (OPC 53) | ≥ 53 | High-strength concrete, industrial slabs |
Special cements (e.g., Portland Pozzolana Cement) have additional additives for improved durability or reduced heat of hydration.
Tests on Cement
Field Tests on Cement
Before procurement, simple on-site checks ensure basic quality:
Visual inspection for lumps, color uniformity, and free-flowing powder
Smell test for any foreign organic odors
Sampling in triplicate from different bags or lots
These quick tests flag obvious defects before detailed lab testing.
Market Analysis of Cement
A market analysis survey covers:
Price trends per bag or tonne across local suppliers
Availability of different grades (33, 43, 53)
Brand reputation (customer feedback on consistency, delivery)
Bulk purchase discounts and credit terms
This helps select cost-effective yet reliable cement sources.
Laboratory Tests on Cement
1. Fineness
Sieve analysis (retained on 90 µm IS sieve): Determines the percentage retained by mass
Blaine’s air permeability method: Measures surface area in m²/kg; finer cement hydrates faster
2. Normal Consistency
Water percentage required to produce a cement paste of standard flow
Determined using a Vicat apparatus; essential for subsequent setting time tests
3. Setting Time
Initial setting time: When paste loses plasticity (should be ≥ 30 minutes)
Final setting time: When paste fully hardens (should be ≤ 600 minutes)
Both measured by penetration resistance in a Vicat mould per IS 4031 (Part 5).
4. Soundness
Le Chatelier method: Measures expansion in a standardized mould; limits prevent excessive volume change in hardened cement
5. Specific Gravity
Ratio of cement density to water density; typically around 3.15
Measured using a Le Chatelier flask or pycnometer
6. Compressive Strength of Cement Cube
Standard mortar cubes (1:3 cement:sand) tested at 3, 7, and 28 days
Validates whether cement meets its grade’s strength requirement
Storing Cement
Warehouse Storage
Store in dry, enclosed sheds with raised platforms
Maintain at least 300 mm clearance from walls and floor
Stack bags not more than 10 bags high
Site Storage
Keep under waterproof tarpaulins on raised platforms
Use on a first-in, first-out basis to avoid aging
Inspect for bag damage and moisture before use
Effect of Storage on Strength
Prolonged exposure to humidity leads to pre-hydration (“lumped” cement)
Loss of fineness and early strength if stored beyond three months in damp conditions
Mixing Water Quality
Requirements
Must be potable, free of organic matter, oils, acids, alkalis, and salts
Acceptable limits per IS 456:
Chlorides ≤ 0.1% by mass of cement
Sulphates ≤ 0.2% by mass of cement
Alkalis ≤ 5% (as Na₂O equivalent)
Impact on Concrete
Impure water can:
Reduce strength gain
Cause efflorescence or corrosion of reinforcement
Affect setting time and durability
UNIT - 02
Fine Aggregate Properties and Laboratory Exercises
Context within the Concrete Technology Module
This section follows cement chemistry and testing and introduces students to fine aggregates—sand and related materials. It combines theoretical properties with hands-on experiments and market studies to prepare learners for concrete mix design and quality control.
Key Material Properties
Fine aggregates are particles passing a 4.75 mm sieve, crucial for concrete workability, strength, and durability. Three primary properties are emphasized:
Specific Gravity – Ratio of aggregate density to water density. – Affects void content, mix proportions, and concrete density.
Bulk Density – Mass of aggregate per unit volume in loose, rodded, or vibrated state. – Guides storage planning and material estimation.
Moisture Content – Percentage of water in aggregate by mass. – Influences water-cement ratio; must be accounted for in batching.
Laboratory and Field Exercises
Water Absorption Test on Silt
Determines water uptake of fine particles under standardized immersion.
Indicates porosity and potential volume change in concrete or soil-cement blends.
Comparative Study: Manufactured Sand vs. River Sand
Assess grading, shape, surface texture, and angularity.
Evaluate workability, bleeding, and strength outcomes in trial mixes.
Cement Cube Compressive Strength Test
Cast 70.6 mm cubes with standard mortar (1:3).
Test at 3, 7, and 28 days to verify cement grade and ensure consistent concrete performance.
Bulking, Sieve Analysis, Grading Curve, and Deleterious Materials
Bulking: volume increase of moist sand; vital for accurate batching.
Sieve Analysis: plot cumulative percent retained to obtain grading curve.
Calculate Fineness Modulus (sum of cumulative percentages retained ÷ 100).
Check for clay lumps, organic matter, shale, or mica exceeding code limits.
Specific Gravity and Fineness Modulus Tests on Fine Aggregate
Use pycnometer or Le-Chatelier flask for specific gravity.
Compute fineness modulus to categorize coarseness: typical range 2.3–3.1.
Emerging Trends in Fine Aggregates
Manufactured Sand (M-Sand) – Crushed rock fines produced to controlled grading; offers consistent supply and lower impurities.
P-Sand (Plastering Sand) – Ultra-fine, washed and graded specifically for plaster and masonry mortars, minimizing crack risk.
Filtered Sand – Recovered from wastewater treatment—washed, graded, and used in non-structural concrete or backfill.
Design and Practice Implications
Understanding these properties and tests ensures:
Accurate batching and water-cement ratio control
Optimal workability without segregation or excessive bleed
Durable concrete with minimal cracking and shrinkage
Strategic selection of alternative sands to balance cost, quality, and sustainability
What Comes Next
Students will leverage these test results to:
Develop trial concrete mixes
Perform workability tests (slump, compacting factor)
Study coarse aggregate properties and combined grading
Execute full mix design procedures per relevant IS codes
UNIT - 03
Coarse Aggregate: Properties, Testing and Practical Exercises
Context within the Concrete Technology Module
This topic appears in the Diploma in Civil Engineering syllabus under Concrete Technology (typically 4th semester). It builds on the earlier section covering fine aggregates, moving into the characteristics, laboratory tests, and site‐handling procedures specifically for coarse aggregates. The theory lectures explain why each property matters, while the practicals reinforce hands‐on skills.
Importance of Size, Shape and Texture
Size
Influences the maximum aggregate size in a mix and affects workability, pumpability and segregation.
Larger aggregates reduce cement demand but may increase bleed and voids.
Shape
Angular aggregates interlock better and give higher strength but reduce workability.
Rounded or sub‐angular particles improve workability and ease of compaction.
Texture
Rough texture increases the bond with cement paste, boosting strength.
Smooth or polished surfaces risk poor adhesion and lower durability.
Grading of Coarse Aggregates
Grading ensures a well‐graded skeleton that minimizes voids and optimizes paste content. In India, IS 383 classifies coarse aggregates into zones based on sieve cut-offs:
| IS Sieve (mm) | Zone I (%) Passing | Zone II (%) Passing | Zone III (%) Passing |
|---|---|---|---|
| 40 | 100 | 100 | 100 |
| 20 | 90–100 | 90–100 | 85–100 |
| 10 | 20–55 | 25–60 | 30–70 |
| 4.75 | 0–10 | 0–10 | 0–10 |
Laboratory and Field Exercises
Study on Recycled Coarse Aggregate
Collect samples of recycled concrete aggregate (RCA) from demolition sites.
Test for grading, specific gravity, water absorption and strength parameters.
Prepare a report comparing RCA properties against natural aggregates and discuss suitability for non‐structural or structural use.
Bulking of Fine Aggregate (River Sand, M-Sand, P-Sand)
Though focused on fine materials, this exercise helps students appreciate how moisture affects volume in adjacent aggregates.
Measure bulking percentage at different moisture contents to understand batching corrections.
Sieve Analysis, Specific Gravity, Flakiness & Elongation Index
Sieve Analysis: Determine particle size distribution using stacked sieves down to 4.75 mm.
Specific Gravity: Use a pycnometer or specific‐gravity flask to find the density ratio to water.
Flakiness Index (IS 2386 Part 1): Percentage of particles whose least dimension is less than 0.6 × their mean size.
Elongation Index (IS 2386 Part 1): Percentage of particles whose greatest dimension exceeds 1.8 × their mean size.
Fineness Modulus & Specific Gravity of Coarse Aggregate
Fineness Modulus (FM): Sum of cumulative % retained on standard sieves ÷ 100; typical FM range for coarse aggregate is 6.5–8.0.
Specific Gravity: As above, but emphasizes the difference between loose, compacted and saturated surface-dry conditions.
Moisture Content, Impact Test & Abrasion Test; Site Storage
Moisture Content: Oven-dry method to determine free and absorbed water—crucial for accurate mix proportions.
Aggregate Impact Value (IS 2386 Part 4): Resistance to sudden shock loads; lower values indicate tougher material.
Los Angeles Abrasion Test (IS 2386 Part 4): Wear resistance under rotating drum action; identifies durable aggregates for pavements.
Site Storage: Store on well-drained platforms, separate stockpiles by size, cover to prevent contamination and moisture ingress.
How These Fit into Mix Design
All of the above properties feed directly into:
Selecting the right aggregate blend for target workability and strength
Calculating mix proportions and water-cement ratios
Ensuring durability (abrasion resistance, frost action) and long-term performance
In subsequent lectures and labs, students will integrate these test results into full concrete mix designs per relevant IS codes.
UNIT - 04
Context within the Concrete Technology Module
This snippet comes from the Concrete Technology syllabus (usually in Semester 4 of the Civil Engineering diploma). It follows detailed study of aggregates and precedes full mix-design procedures. On the surrounding page, you’ll see:
Earlier lectures on fine and coarse aggregate properties and tests
Hands-on activities for grading, absorption, shape indices
An impending shift from raw materials into the chemistry and performance of actual concrete
Core Lecture Topics
Hydration of Cement
How cement minerals react with water, releasing heat and forming solid hydrates
Stages of hydration (initial wetting, dormant period, acceleration, deceleration, steady-state)
Bogue’s Compounds
The four principal clinker phases in Ordinary Portland Cement:
Tricalcium silicate (C₃S)
Dicalcium silicate (C₂S)
Tricalcium aluminate (C₃A)
Tetracalcium alumino-ferrite (C₄AF)
Their approximate proportions control early strength, later strength and heat evolution
Tutorial & Demonstration Activities
Advantages and Uses of Concrete
Compare concrete’s compressive strength, durability, fire resistance, moldability
Contrast with steel, masonry, timber and alternative materials
Hydration Video Demonstration
Visualize hydration stages under the microscope
Observe the microstructure of hydrated cement paste (capillary pores, C–S–H gel, CH crystals)
Laboratory Exercises
Aggregate Shape Indices
Flakiness Index & Elongation Index on coarse aggregate to assess particle geometry
Hydration-Related Calculations
Compute gel/space ratio to predict paste microstructure
Determine theoretical water requirement for complete hydration
Relate these to practical water-cement ratios
Moisture and Absorption Tests
Fine and coarse aggregates: water absorption and surface-moisture content
Understand how free vs. absorbed water alters batching
Effect of W/C Ratio on Microstructure
Cast small cement paste samples at different w/c ratios
Examine porosity, crack tendencies and strength potential as w/c increases
How This Builds Toward Mix Design
By linking cement chemistry (Bogue’s phases) to real-world water demands and microstructure, students learn why controlling w/c is paramount.
Aggregate moisture and shape data feed directly into accurate batching and durability checks.
These foundations pave the way for the subsequent weeks’ full concrete mix design per IS codes, workability tests, and strength trials.
UNIT - 05
Explanation of Concrete Testing and Behaviour Topics
Context within the Concrete Technology Syllabus
This set of topics appears after students have learned about cement hydration, aggregate properties, and early mix trials. It bridges the gap between understanding raw material characteristics and performing full mix design by focusing on how environmental and specimen factors influence concrete strength, along with workability and basic strength‐related tests[_{{{CITATION{{{_1{](file:///D:/TRASH/Diploma_Civil_Syllabus_3rd,_4th[1]%20(2).pdf).
Internal Factors Affecting Cube Strength
Internal moisture
Moisture retained within the paste and aggregates at casting affects hydration rate and final strength.
Temperature
Higher curing temperatures accelerate hydration but can cause uneven microstructure; low temperatures slow strength gain.
Age of specimen
Standard tests at 3, 7, and 28 days capture strength development curve; longer curing generally increases strength up to a limit.
Size of specimen
Larger cubes or cylinders may exhibit lower apparent strength due to internal flaws and nonuniform stress distribution.
These variables must be controlled or corrected for when comparing cube test results.
Practical Exercise: Workability Comparison
Prepare a report comparing different concrete grades (e.g., M20, M25, M30) on the basis of workability measures (slump, compacting factor, flow).
Cast nominal mixes for each grade and record slump values under standardized conditions.
This exercise helps students link mix proportions to on‐site handling characteristics.
Workability Concepts
Factors affecting workability
Water–cement ratio, aggregate shape and grading, cement content, admixtures, and temperature.
Measurement methods
Slump test (ease of deformation under gravity)
Compaction factor test (degree of compaction under standard hammering)
Segregation and bleeding
Segregation: coarse aggregate settling out of the mix
Bleeding: water rising to the surface of placed concrete
Understanding these phenomena ensures safe placement without defects.
Practical Exercise: Compaction Factor Test
Conduct the compaction factor test on the nominal mix to quantify how easily the concrete compacts under a controlled drop. Compare results with slump values to appreciate each method’s sensitivity to mix changes.
Strength, Durability, and Permeability
Characteristic strength
The 28-day compressive strength below which not more than 5% of test results are expected to fall.
Durability
The ability of concrete to resist weathering, chemical attack, abrasion and maintain serviceability.
Permeability
Measure of how readily fluids pass through concrete; directly related to pore structure and w/c ratio.
Factors Affecting Strength and Durability
Water–cement ratio
Lower w/c yields higher strength and lower permeability but reduces workability.
Maturity
Combined effect of time and temperature on strength development; higher maturity index corresponds to higher strength gain.
Aggregate properties
Strength, grading, shape and surface texture influence bond with paste and overall concrete performance.
What Comes Next
With these fundamentals and test data, students will proceed to:
Detailed concrete mix design per IS 10262
Use of admixtures for enhanced workability and durability
Advanced durability testing (chloride penetration, freeze–thaw cycles)
Field inspection and quality control procedures on real structures
UNIT - 06
Concrete Mechanical Properties and Shrinkage
Context within the Concrete Technology Module
This topic follows mix design and basic workability tests. It introduces how concrete behaves under different loadings and environmental conditions, and it ties together strength, stiffness, bond, and volume‐change characteristics before students move on to advanced durability and non-destructive evaluations.
1. Strength Parameters
Compressive Strength
The maximum axial load per unit area that concrete can resist.
Tested on 150 mm cubes (or 100 mm for smaller mixes) at 7 and 28 days.
Defines the concrete grade (e.g., M20 means 20 MPa at 28 days).
Split Tensile Strength
An indirect measure of concrete’s resistance to tension.
A cylinder is loaded diametrically until it splits.
Typically 8–10% of compressive strength, guiding crack‐control design.
Bond Strength
The shear stress at the concrete–steel interface under pull-out loading.
Governs development length and anchorage of reinforcement.
Ensures composite action between steel and concrete.
Modulus of Rupture (Flexural Strength)
The load‐carrying capacity under bending before cracking.
Determined by three‐ or four‐point loading of beams.
Used for pavements and precast elements where flexure dominates.
2. Elastic Properties and Bond
Modulus of Elasticity (E)
The slope of the initial linear portion of the stress–strain curve.
Relates stress (σ) to strain (ε): σ = E·Îµ.
Typically 0.4–0.5 × √fck (in MPa) per IS 456.
Poisson’s Ratio (ν)
The ratio of lateral strain to longitudinal strain under axial loading.
Commonly ranges from 0.15 to 0.20 for normal-weight concrete.
Relationship Between E and ν
For isotropic, linear-elastic materials:
Shear modulus G = E / [2(1 + ν)]
Bulk modulus K = E / [3(1 − 2ν)]
Aggregate–Cement Bond Strength
Reflects how well the paste adheres to aggregate surfaces.
Influenced by aggregate texture, moisture condition, and mix design.
Tested via pull-out of embedded studs or bars to simulate anchorage.
3. Shrinkage
Plastic Shrinkage
Volume reduction before concrete sets, caused by rapid moisture loss from the surface.
Manifests as map-like surface cracks on fresh slabs.
Controlled by curing, wind breaks, and plasticizers.
Drying Shrinkage
Long-term shrinkage as hardened concrete loses internal moisture.
Results in gradual length reduction over months.
Mitigated by low w/c ratio, proper curing, and use of shrinkage-reducing admixtures.
Factors Affecting Shrinkage
Water–cement ratio (higher w/c → more shrinkage)
Cement content (more paste → more shrinkage)
Aggregate proportion and stiffness (more stiff aggregates → restrain shrinkage)
Temperature and relative humidity (higher temperature & lower RH → greater shrinkage)
What Comes Next
Integrating these properties into serviceability checks (deflection, crack width).
Durability evaluations: permeability, chloride penetration, freeze–thaw resistance.
Non-destructive testing methods: rebound hammer, ultrasonic pulse velocity.
Code provisions (IS 456) for allowable stresses, crack control, and shrinkage limits.
UNIT - 07
Creep and Durability Topics in Concrete Technology
Context within the Syllabus
This module appears after students have learned concrete mix design, workability, strength, and shrinkage. It introduces time-dependent deformation (creep), crack causation and control, and concrete performance in aggressive environments. Hands-on site visits and laboratory demonstrations reinforce theory.
1. Creep of Concrete
Factors Affecting Creep
Water–cement ratio (higher w/c → more creep)
Age at loading (younger concrete creeps more)
Stress level (creep increases with sustained stress)
Temperature and humidity (higher temperature & RH accelerate creep)
Aggregate type and stiffness (stiffer aggregates restrain creep)
Effects of Creep
Long-term deflections in beams and slabs
Progressive shortening of columns
Redistribution of internal forces in indeterminate structures
Potential for secondary cracking if restraint exists
Site Visit / Demonstration
Measurement of Creep • Install dial gauges or LVDTs on loaded concrete specimens over weeks/months • Record gradual strain increase under constant load
Permeability Testing • Conduct water-penetration or rapid chloride-ion penetration tests on site-cured samples • Relate permeability to long-term durability and creep behavior
2. Cracks in Concrete and Remedies
Factors Contributing to Cracks
Settlement cracks (uneven support settlement)
Thermal expansion/contraction (daily and seasonal temperature swings)
Structural design deficiencies (insufficient reinforcement, poor detailing)
Common Crack Remedies
Epoxy injection for narrow structural cracks
Routing and sealing with polyurethane sealants for non-structural joints
Installing additional reinforcement (stitching) at frequent crack locations
Surface overlays or overlays with fiber-reinforced mortar
Proper joint layout (control and expansion joints) during construction
Testing: Core Cutter Test for Compressive Strength
Extract 100–150 mm diameter cores from hardened concrete
Machine ends flat and load to failure in a compression testing machine
Adjust results for aspect ratio and age to verify in-situ strength
3. Concrete in Aggressive Environments
Degradation Mechanisms
Alkali–Aggregate Reaction (AAR): internal expansion and cracking due to reactive silica
Sulfate Attack: ettringite formation causing expansion and spalling
Chloride Attack: pitting corrosion of reinforcing steel
Acid Attack: surface erosion in low-pH environments
Sea Water Exposure: combined chloride ingress and wet–dry cycling
Carbonation: reduction of pH leading to steel depassivation
Freeze–Thaw Cycles: surface scaling from cyclic freezing of pore water
Protective Measures
Use of low-permeability mixes (low w/c, pozzolanic additions)
Corrosion-inhibiting admixtures and epoxy-coated reinforcement
Application of silane/siloxane waterproofing coatings
Design of proper cover thickness and drainage details
Air-entrainment for freeze–thaw resistance
What Follows
Students will integrate creep and durability considerations into:
Advanced mix designs with supplementary cementitious materials
Serviceability checks for long-span and prestressed elements
Detailed durability specifications per IS 456 and relevant special codes
Non-destructive evaluation methods for in-service structures
UNIT - 08
Concrete Operations in the Concrete Technology Syllabus
This set of topics sits right after students learn mix design theory and material testing. It covers the practical steps of producing fresh concrete: measuring (batching) ingredients, combining them (mixing), and moving the mix to where it’s needed (transportation).
1. Batching
Batching ensures each concrete ingredient is measured accurately to achieve the designed proportions and target strength.
(a) Cement Batching
By volume: use a calibrated gauge box to scoop out cement
By weight: weigh on spring balances or electronic scales for higher accuracy
Importance: even small errors in cement quantity alter workability and strength
(b) Aggregate Batching
Volume batching
Use a gauge box sized to the nominal mix proportions (e.g., 1 : 2 : 4)
Select box dimensions so that one “gauge” of sand and aggregate fits exactly
Correct for sand bulking—moist sand occupies more space, so pre‐dry or apply a bulking factor
Weight batching
Spring balances or mechanical/electronic batching machines
More precise and compensates automatically for moisture in aggregates
(c) Water Measurement
Measure with graduated buckets or by weight on scales
Adjust for moisture in aggregates to maintain the designed water–cement ratio
IS Codal Provisions for Mix Design
Follow IS 10262 for mix‐proportioning steps
Adhere to IS 456 tolerances on batching accuracy and moisture correction
2. Mixing
Proper mixing distributes cement paste uniformly over aggregates, avoids pockets of dry sand, and ensures consistent concrete quality.
(a) Hand Mixing
Small batches on a clean, flat platform
Spread cement and sand, mix dry, then add aggregate and finally water
Labour‐intensive and prone to inconsistency
(b) Machine Mixing
Mixer Types
Tilting drum mixers (0.5–2 m³ capacity)
Non‐tilting drum mixers (1–6 m³ capacity)
Pan and pugmill mixers for high‐precision mixes
Selecting Mixer Size
Match daily concrete volume and site space
Ensure mixer can complete full mixing cycle (charging → mixing → discharging)
Operation & Maintenance
Clean immediately after use to prevent hardened buildup
Check blades, seals and motor regularly
Lubricate bearings and inspect paddles for wear
Gauge Box Preparation & Demonstration
Fabricate a wooden or metal box with internal dimensions based on mix ratio
Calibrate by weighing known volumes of sand/aggregate
Students demonstrate both hand and machine mixing using the prepared gauge box
3. Transportation
Once mixed, concrete must reach the formwork before initial set without segregation or loss of workability.
Pans and wheelbarrows for very short hauls (within a few meters)
Transit mixers (truck‐mounted) for medium to long distances; keep mix agitating en route
Chutes attached to mixer drums for direct discharge into formwork
Belt conveyors in precast yards or large batching plants
Concrete pumps (line pumps and boom pumps) for placing at height or in confined areas
Tower cranes with buckets or skips for vertical lifts on high‐rise sites
Linking Back to Mix Design
Accurate batching and mixing preserve the water–cement ratio and aggregate grading established during mix design.
Proper transport methods prevent segregation, ensuring the fresh concrete arrives with the designed slump, entrapped air content, and strength potential.
These operational controls, when combined with correct mix proportions (per IS codes) and curing, lead to durable, high‐performance concrete.
UNIT - 09
Explanation of “CONCRETE OPERATIONS” in the Concrete Technology Syllabus
Context within the Course
This topic typically appears in the Concrete Technology subject (Semester 4 of the Diploma in Civil Engineering). Having covered material properties, mix design and basic on-site processes, students now learn the full sequence of producing, placing, consolidating, finishing and curing concrete—both site-mixed and ready-mix—through demonstrations, site visits and hands-on trials.
1. Ready-Mix Concrete (RMC)
Manufacturing of RMC
Central batching plants weigh cement, aggregates and water precisely.
Semi-automated plants meter materials into hoppers; fully automated plants use computer controls for dosing and mixing.
Admixtures are added in measured quantities for slump control, setting time or durability enhancements.
Quality Inspection of RMC at Site
Check delivery ticket for mix grade, batch time, plant temperature and drum revolutions.
Perform slump test immediately on arrival to confirm workability.
Monitor concrete temperature; adjust placement or use retarders in hot weather.
Cast trial cubes for 7- and 28-day strength validation.
Precautions and Care
Before delivery: ensure formwork, reinforcement and embedments are clean and ready.
During placement: maintain continuous communication with the plant to avoid delays; clear chutes/pumps of blockages.
After placing: protect fresh concrete from rapid moisture loss or temperature extremes; begin curing promptly.
2. Field Demonstrations and Reporting
Site Visit: Observe end-to-end operations—batching, mixing, loading, transit mixing, placing, compaction, finishing and curing.
Batching Demonstration:
Volume batching with a calibrated gauge box on a small site mix.
Weigh batching at a plant or using portable scales.
Operations Report: Students document each stage—equipment used, sequence, quality checks and safety practices—comparing semi-automated vs fully automated RMC processes.
3. Compaction of Concrete
Hand Compaction
Use tamping rods or pokers to consolidate small pours or corners where vibrators cannot reach.
Apply firm, even strokes at regular spacing to expel entrapped air.
Machine Compaction
Internal Vibrators: Needle probes inserted vertically; ideal for beams, columns and slabs of medium depth.
External Vibrators: Clamped to formwork; suitable for heavily reinforced or thin precast panels.
Pan Vibrators: Portable vibrating plates; used for pavements and shallow slabs.
Handling and Suitability
Insert internal vibrators 50–75 mm from formwork or reinforcement and hold 5–15 seconds until mortar sheen appears.
Over-vibration causes segregation; under-vibration leaves honeycombing.
Choose external
UNIT - 10
Mineral Admixtures in Concrete
Context within the Syllabus
This topic appears in the Concrete Technology module immediately after coverage of concrete operations (batching, mixing, compaction) and durability issues. It introduces supplementary cementitious materials that modify fresh and hardened concrete properties.
1. Fly Ash
Fly ash is the finely divided residue from coal combustion in thermal power plants.
Composition
Mainly silica (SiO₂), alumina (Al₂O₃), and calcium oxide (CaO)
Classified as Class F (low CaO) or Class C (higher CaO) by ASTM C618
Properties
Pozzolanic reactivity with calcium hydroxide
Spherical particle shape improving workability
Specific gravity around 2.1–2.9
Uses
Partial cement replacement (15–30%) in structural concrete
Mass concrete to reduce heat of hydration
Self-consolidating concrete
Advantages
Reduces permeability and improves long-term strength
Lowers heat evolution and thermal cracking risk
Eco-friendly by recycling an industrial by-product
2. Ground Granulated Blast-Furnace Slag (GGBS)
GGBS is a by-product of iron-making, obtained by quenching molten slag.
Composition
Rich in calcium silicates and aluminosilicates
Glassy granular form, ground to cement fineness
Properties
Latent hydraulic activity activated by alkalis in cement
Specific gravity about 2.9
Uses
Cement replacement up to 50% in marine and sewer-exposed concrete
Precast units for improved surface finish
Advantages
Increases sulfate and chloride resistance
Reduces alkali-silica reaction risk
Lowers embodied CO₂ compared to OPC
3. Silica Fume
Silica fume (microsilica) is an ultra-fine by-product of silicon/ferrosilicon smelting.
Composition
Over 90% amorphous silicon dioxide (SiO₂)
Particle size around 0.1 µm (100× finer than cement)
Properties
Extremely high specific surface area (~20,000 m²/kg)
Highly pozzolanic, filling nano-voids
Uses
High-performance and high-strength concrete (>100 MPa)
Epoxy mortars, grouts, and repair mixes
Advantages
Dramatically improves early strength and impermeability
Minimizes chloride ingress and abrasion
Reduces bleeding and segregation
Practical Activities
Study and report on natural fibres (e.g., jute, coir) versus artificial fibres (e.g., polypropylene, glass) for fibre-reinforced concrete.
Prepare concrete mix designs incorporating fly ash, GGBS, and silica fume per IS 10262. Conduct slump tests (IS 1199) and compaction factor tests (IS 1199) on the fresh mixes.
UNIT - 11
Chemical Admixtures in Concrete Technology
Context within the Course
This topic follows the sections on concrete mixing, transportation, and compaction in the Concrete Technology module. It introduces chemical admixtures that modify fresh and hardened concrete properties and sets up hands-on activities like market surveys and site visits to understand real-world application.
1. Plasticizers and Superplasticizers
Composition
Plasticizers: lignosulfonates or sulfonated melamine/formaldehyde condensates
Superplasticizers: sulfonated naphthalene, polycarboxylate ethers
Properties
Plasticizers reduce water demand by 5–10% without affecting workability
Superplasticizers can lower water–cement ratio by 15–30% or increase slump by 100–150 mm
Uses
Plasticizers for general workability improvement in beams, slabs, pavements
Superplasticizers for high-strength, self-compacting, or pumped concretes
Advantages
Enhanced flowability at low water–cement ratios
Reduced bleeding and segregation
Improved early strength development and long-term durability
2. Accelerators and Retarders
Composition
Accelerators: calcium chloride (up to 2% by mass), triethanolamine, calcium nitrite
Retarders: sugars, hydroxycarboxylic acids, phosphates
Properties
Accelerators shorten setting time and speed early strength gain
Retarders extend setting time, preventing cold joints in hot climates or long transport
Uses
Accelerators in cold weather concreting or for rapid repair works
Retarders in mass pours, complex formwork, or RMC needing long haul times
Advantages
Control over setting time to match ambient conditions and placement rate
Minimized risk of thermal cracking in large pours
Flexibility in logistics for Ready-Mix operations
3. Air-Entraining and Integral Waterproofing Compounds
Composition
Air-Entraining Agents: vinsol resin, synthetic detergents, fatty acids
Integral Waterproofing Compounds: crystalline or siloxane-based powders/liquids
Properties
Air-Entraining Agents introduce stable micro-bubbles (3–5% air content)
Waterproofing Compounds react to form insoluble crystals that block pores
Uses
Air-Entraining for freeze-thaw resistance in pavements, bridge decks, and climate-exposed structures
Integral Waterproofing in basements, water tanks, underground works
Advantages
Improved resistance to frost damage and scaling
Reduced permeability to water and aggressive ions
Enhanced durability of concrete in harsh environments
Practical Exercises
Conduct a market analysis comparing available chemical admixture brands, pricing, dosage rates, and technical support.
Undertake site visits to observe and report on concrete pumping methodology for upper-floor placement: pump selection, pipeline layout, admixture adjustment, and quality control.
UNIT - 12
Special Concretes in the Concrete Technology Module
Context within the Syllabus
These topics appear toward the end of the Concrete Technology subject (typically 4th semester of the Civil Engineering diploma). After students master mix design, batching, mixing, compaction, and admixtures, the syllabus shifts to special-purpose concretes that push performance boundaries. Practical exercises then reinforce theoretical concepts through workability and flow tests.
1. High Strength Concrete (HSC) and High Performance Concrete (HPC)
Ingredients and Preparation
Cement
Use of higher-grade OPC (53) or special rapid-hardening cements
Water–cementitious materials ratio
Very low w/cm (0.25–0.40) to achieve strength > 60 MPa for HSC
Inclusion of supplementary binders (silica fume, fly ash, GGBS) for HPC
Aggregates
Well-graded, strong coarse aggregates with high crushing values
Clean, single-sized or optimally graded fine aggregates
Chemical admixtures
Superplasticizers to maintain workability at low w/cm
Viscosity modifiers (for self-compacting variants)
Mixing and curing
Thorough dry mixing of powders and aggregates
Introduction of water and admixtures in controlled sequence
Extended moist curing (14–28 days) to prevent microcracking
Advantages
Very high compressive and flexural strengths
Reduced permeability and enhanced durability
Better modulus of elasticity and creep resistance
Superior fatigue and abrasion performance
Applications
High-rise buildings and long-span bridges
Pre-stressed concrete elements
Industrial floors and carbonated environments
Marine structures and nuclear shielding (HPC variants)
1 & 2. Practical Exercise: SCC Workability Tests
After comparing HSC/HPC with conventional M20/M30:
Prepare a Self-Compacting Concrete (SCC) mix per IS 10262, then determine flow characteristics using:
Slump flow test (spread diameter in mm)
V-funnel test (flow time in seconds)
L-box test (height ratio of blocked to free flow)
U-box test (flow balance across two chambers)
These tests quantify filling ability, passing ability, and segregation resistance.
2. Pervious Concrete and High Density Concrete
Pervious Concrete
Ingredients and Preparation
Coarse aggregate (10–20 mm), little to no fines
Cement paste just enough to coat aggregates
No fine aggregate ensures interconnected void network
Advantages
Allows storm-water infiltration and reduces runoff
Mitigates urban flooding and recharges groundwater
Applications
Pavements, parking lots, pedestrian walkways
Environmental landscaping and green roofs
High Density Concrete
Ingredients and Preparation
Heavy aggregates (barite, magnetite, hematite) with specific gravity 4–6
Standard OPC, low w/cm to maintain strength
Advantages
High mass per unit volume (3.6–4.0 t/m³)
Excellent radiation shielding and vibration damping
Applications
Nuclear reactor shields, medical radiation bunkers
Counterweights in cranes and bridges
3. Self-Compacting Concrete (SCC)
Ingredients and Preparation
High cementitious content (OPC + fillers like limestone powder)
Fine aggregates adjusted to achieve high powder ratio
Superplasticizer for high flow (S4/S5 classes)
Optional viscosity-modifying admixture to prevent segregation
Mixing sequence: powders → aggregates → water+superplasticizer → rest
Advantages
No mechanical vibration required, saving labor and time
Excellent surface finish and minimal honeycombing
Superior filling of congested reinforcement cages
Applications
Precast factory production
Complex form-works and heavily reinforced sections
Repair works in confined spaces
<div align="center">---</div>
What Follows
Students build on these special concrete topics by:
Designing trial mixes for each special concrete type
Evaluating hardened properties (strength, durability, permeability)
Studying long-term behaviors (shrinkage, creep) under aggressive environments
Integrating special concretes into real-world project specifications and quality control plans
UNIT - 13
Special and Emerging Concretes in Concrete Technology
Context within the Concrete Technology Module
These topics come after traditional concrete mix design and performance testing. Students now explore specialty concretes—each formulated for unique mechanical, durability, or environmental demands. The focus is on understanding what goes into these mixes, how they’re prepared, their benefits, and where they’re used.
1. Reactive Powder Concrete (RPC), Roller-Compacted Concrete (RCC) & Epoxy Concrete
Reactive Powder Concrete (RPC)
Ingredients
Very fine powders: cement, silica fume, quartz sand
Superplasticizer to achieve high flow
Steel fibers (optionally) for toughness
Preparation
Dry‐mix all powders and fibers
Add water and superplasticizer under high‐speed mixing
Cast in dense form; apply vibration to eliminate voids
Advantages
Ultra-high compressive strength (> 200 MPa)
Exceptional durability and abrasion resistance
Minimal porosity and permeability
Applications
Thin architectural panels and façades
High-performance bridge decks and overlays
Blast-resistant and protective structures
Roller-Compacted Concrete (RCC)
Ingredients
Zero-slump mix: high coarse aggregate content, moderate cement
Optional fly ash or slag for workability and economy
Preparation
Produce in a conventional concrete plant or continuous mixer
Place with an asphalt paver to desired thickness
Compact in successive passes using vibratory rollers
Advantages
Rapid placement over large areas
Lower cement content and reduced cost
High strength (> 30 MPa) and long-term performance
Applications
Dam spillways, levees, canal linings
Heavy-duty pavements (industrial yards, ports)
Embankments and flood control works
Epoxy Concrete
Ingredients
Epoxy resin binder and hardener
Clean, graded aggregates (quartz, silica sand)
Fillers (optional) for volume stability
Preparation
Pre‐mix resin and hardener to exact ratio
Blend in aggregates until uniform coating
Place quickly; cures at ambient temperature
Advantages
Outstanding chemical and corrosion resistance
Very high bond strength to existing substrates
Rapid strength gain (hours)
Applications
Industrial flooring, trench and pit linings
Structural repair and grouting
Chemical containment areas
2. Compressive Strength Testing of Special Concretes
Students perform standardized strength tests tailored to specialty mixes:
Cast cubes or cylinders per each special concrete type.
Cure under prescribed conditions (ambient or elevated for geopolymer).
Test at 7- and 28-day intervals to compare against conventional concrete benchmarks.
These results validate mix performance and guide practical deployment.
3. Geopolymer and Lightweight Concretes
Geopolymer Concrete
Ingredients and Preparation
Alumino-silicate source: fly ash or GGBS
Alkali activator: sodium hydroxide + sodium silicate solution
Aggregates and controlled water content
Mix activator solution first, then blend in binder and aggregates
Advantages
Drastically lower CO₂ footprint
Rapid early strength (up to 50 MPa in 24 hours)
Excellent chemical and fire resistance
Applications
Precast structural elements
Fire-resistant cladding panels
Infrastructure in aggressive chemical environments
Lightweight Concrete
Ingredients and Preparation
Lightweight aggregates: expanded clay, shale, perlite or pumice
Alternatively, foam agents produce air-entrained cellular concrete
Mix gently to preserve aggregate or foam structure
Advantages
Reduced dead loads on structures
Thermal and acoustic insulation properties
Ease of handling and faster placement
Applications
Non-load-bearing partition walls and panels
Roof insulation layers and floor screeds
Bridge decks and floating structures
What Comes Next
Students will integrate these specialty concrete concepts into:
Advanced durability testing (chloride penetration, sulfate resistance)
Field trials of mix placement and finishing
Life-cycle cost and sustainability assessments
Code compliance for novel materials (IS 456, relevant ASTM/EN standards)
0 Comments