Code of practice for preparation and use of lime concrete
1991 Edition

Overview of Scope

• Addresses the preparation, application, and testing of lime concrete.
• Materials and mix ratios should replicate those used onsite.
• Test specimens are frustum-shaped cones with dimensions:
  • Base diameter: 200 mm
  • Top diameter: 100 mm
  • Height: 300 mm

Mix Ratio Guidelines

• Refer to specified tables for mix proportions tailored to different applications.
• Mix must simulate field conditions.

Curing Instructions

• Continuous curing for a minimum of 21 days.
• Employ curing methods as detailed in the relevant clauses.

Referenced Standards

• Includes IS 269, IS 383, IS 712, IS 1344, IS 2250, and IS 5817 among others.

Test Specimen Dimensions

graph TD
A[Frustum Cone Specimen] --> B[Base Diameter: 200 mm]
A --> C[Top Diameter: 100 mm]
A --> D[Height: 300 mm]

Summary

• Use identical materials and ratios as onsite.
• Fabricate test specimens with specified dimensions.
• Maintain curing continuously for 21 days.
• Consult listed IS codes for material and design guidance.

Material Selection and Proportions

• Materials and proportions must mirror those utilized in actual construction.
• Water content in test mixes should closely match site conditions.
• Consult designated tables for mix ratios based on intended use.

Curing Requirements

• Maintain continuous curing for no less than 21 days.
• Follow prescribed curing techniques.

Referenced Indian Standards

• Key references include IS 269 (Portland cement), IS 383 (aggregates), IS 712 (building limes), IS 1344 (calcined clay pozzolana), IS 3812 (fly ash), and IS 2250 (masonry mortars).

Flexural Strength Calculation

• For a specimen span of 150 mm, the modulus of rupture is calculated using specified formulas depending on the fracture line location.

Summary

• Employ standardized materials per IS specifications.
• Match water content with site usage.
• Cure specimens for at least 21 days.
• Use defined formulas for strength evaluation.

flowchart LR
    A[Material Selection] --> B[Mix Proportioning]
    B --> C[Specimen Preparation]
    C --> D[Curing]
    D --> E[Strength Testing]

Categories of Mortar

• Plain lime mortar
• Lime-pozzolana mortar
• Lime-cement mortar

Lime should be used as dry hydrated lime or lime putty conforming to IS 1635:1975. Mortar preparation follows IS 2250:1981.

Suggested Mortar Mix Ratios

Workability

• Lime mortars retain water effectively.
• Improved workability achieved with higher lime proportions and well-graded aggregates.

General Mortar Mix Formula

[ \text{Mortar} = \text{Lime} : \text{Pozzolanic Material (optional)} : \text{Fine Aggregate} ]

Example: 1 lime : 1 pozzolana : 1 fine aggregate.

Fine Aggregate Specifications

• Must be clean and free of clay lumps and organic matter.
• Brick aggregates should comply with IS 3182:1986.
• Proper grading and cleanliness are essential for quality concrete.

Coarse Aggregate Requirements

• Wash aggregates if contaminated with excessive dirt.
• Porous aggregates such as burnt clay or cinder must be used in a saturated surface dry (SSD) state.
• Soaking guidelines:
  • Immerse for 24 hours at 27°C ± 2°C.
  • Drain excess water for 2 to 3 hours before use.

Testing Conditions

• Materials should be at room temperature (27°C ± 2°C) prior to testing.
• Coarse aggregates prepared to SSD condition.

flowchart TD
    A[Coarse Aggregate] --> B{Is Dirt Present?}
    B -- Yes --> C[Wash Aggregate]
    B -- No --> D[Soak Aggregate]
    D --> E[24 hours at 27°C ± 2°C]
    E --> F[Drain Excess Water 2-3 hours]
    F --> G[Use in SSD Condition]

Mixing Proportions for Lime Concrete

Strength Requirements

Strength Parameters

• Minimum compressive strength of 1 N/mm² at 28 days.
• Transverse strength of 0.2 N/mm² at 90 days.
• Compressive strength expected around 1.2 N/mm² at 90 days.

Mix Ratios by Application

Lime Quality

• Must comply with IS 712:1984 (Classes A to E).
• When using lime putty, proportion by equivalent dry slaked lime.

Workability

• Recommended slump ranges from 50 to 75 mm.

Additional Considerations

• Adjust mixes based on moisture content, groundwater level, and load conditions.
• Use either stone or broken brick as coarse aggregates depending on availability.

Placement and Layer Thickness

• Do not exceed 100 mm thickness per concrete layer under normal conditions.
• Layers up to 150 mm permitted if adequately consolidated.
• Avoid dropping concrete from a height to prevent segregation.

Compaction

• Compact layers until moist mortar surfaces appear.
• Use manual ramming or mechanical devices such as plate compactors or surface vibrators.
• Prevent contamination during placement.

Subgrade Preparation

• Prepare subgrade by moistening and tamping before concrete placement.

Curing

• Maintain continuous curing for at least 21 days.
• Employ methods such as water sprinkling or covering with moist materials.

flowchart TD
    A[Prepare Soil Subgrade] --> B[Moisten and Ram Soil]
    B --> C[Place Concrete Layer ≤ 100 mm]
    C --> D[Compact Layer (Manual/Mechanical)]
    D --> E{Wet Mortar Visible?}
    E -- Yes --> F[Proceed to Next Layer or Curing]
    E -- No --> D
    F --> G[Begin 21-Day Curing]

Refer to mix proportion tables and relevant IS codes for detailed specifications.

Typical Uses

• Leveling courses in foundations and plain concrete footings.
• Base concrete layers beneath floors.
• Filling haunches in masonry arch constructions.

Selection Considerations

• Moisture condition of the subgrade.
• Groundwater depth.
• Load requirements of foundations and floors.
• Type of floor finish desired.

Recommended Mixes

Additional Notes

• Use lime putty proportions equivalent to dry slaked lime.
• Recommended slump for workability is 50 to 75 mm.
• Fine aggregate should meet cleanliness and grading requirements.
• Adjust mix based on specific moisture and load conditions.

Specifications for Arch Haunch Filling

• Lime concrete mix recommended for filling over masonry arch haunches.
• Typical volume mix ratio:
  • 1 part lime : 1 part pozzolanic material : 1 part fine aggregate.
• Coarse aggregate: broken brick with maximum size of 25 mm.
• Mortar to coarse aggregate ratio: 45 parts mortar to 100 parts aggregate by volume.
• Workability slump: 50 to 75 mm.

Strength Criteria

Notes

• Lime classes B through E are suitable for these mixes.
• Dry hydrated lime or lime putty (equivalent dry lime content) is acceptable.
• These mixes provide moderate strength and durability appropriate for arch haunch applications.

Summary Table

This standard references multiple Indian Standards essential for materials and practices related to lime concrete:

Notes

• Emphasis on durability and sulphate resistance.
• Cement grades referenced include 33, 43, and 53 Grade as per IS 269, 8112, and 12269.
• Pulverized fuel ash is used in lime-pozzolana mixtures.
• These standards cover materials, preparation processes, and testing methods critical for lime concrete.

Specimen and Equipment

• Use lime concrete cubes prepared under controlled laboratory conditions.
• Testing machine must have adequate capacity and accuracy within ±2% of maximum load.
• Steel platens with hardened faces; one platen with spherical seating to ensure uniform load distribution.
• Platens' flatness: ≤ 0.01 mm when new; maintained within 0.02 mm.

Testing Procedure

• Clean specimen faces and platens.
• Apply load on opposite vertical faces, not on the top and bottom.
• Align specimen axis with the center of the spherical platen.
• Apply load continuously at a rate of 10 ± 5 N/mm² per minute until failure.
• Record maximum load and observe failure mode.

Strength Calculation

[ \text{Compressive Strength} = \frac{P_{max}}{A} ] Where:

• ( P_{max} ) = maximum load in Newtons
• ( A ) = cross-sectional area in mm²

Acceptance

• Average strength from three specimens constitutes the batch result.
• Individual results should be within ±15% of the average; otherwise, retesting is necessary.

flowchart TD
    A[Prepare Specimens] --> B[Clean Platens & Specimen Faces]
    B --> C[Place Specimen Vertically]
    C --> D[Align Axis with Spherical Platen Center]
    D --> E[Apply Load at 10 ± 5 N/mm² per min]
    E --> F[Record Max Load and Failure Mode]

Specimen Preparation and Dimensions

• Specimens of size 150 mm × 150 mm × 700 mm prepared and cured as per compressive strength tests.
• Store specimens in water at 27°C ± 2°C for 22 hours prior to testing.

Test Setup

• Support span: 600 mm between two steel rollers (diameter 38 mm).
• Loading applied via two rollers spaced 200 mm apart at third points of the span.
• Load applied axially without torsion or restraint.
• Loading rate: increase so that fiber stress rises approximately at 0.7 N/mm² per minute or 4000 N per minute.
• No packing material between specimen and rollers; ensure clean contact surfaces.

Calculation of Flexural Strength (Modulus of Rupture)

Let:

• P = Maximum load (N)
• b = Specimen width (mm)
• d = Depth at failure (mm)
• a = Distance from fracture to nearest support (mm)
• l = Span length = 600 mm

Diagram of Test Setup