Masonry Mortar Joint Shear Strength Index Test
(In-Situ Shear Strength — ASTM C1531)

In-situ measurement of masonry mortar bed joint shear strength — providing actual shear resistance data for structural and seismic assessment of existing unreinforced masonry walls.

Overview

What is the Masonry Mortar Joint Shear Strength Index Test?

The Masonry Mortar Joint Shear Strength Index Test removes mortar from adjacent vertical joints, then applies a horizontal shear force to slide a single brick along its bed joint. The test provides initial shear strength (cohesion) data critical for IS 1893 seismic assessment of unreinforced masonry.

Conducted as per ASTM C1531, this test is essential for seismic vulnerability assessment of URM buildings, heritage building structural assessment and post-earthquake safety evaluation. The measured shear strength is used directly in masonry shear capacity calculations per IS 1905 and IS 1893.

In-Situ Shear Strength

Actual mortar shear resistance measured — not estimated from lab cube tests.

IS 1893 Seismic Input

Shear strength directly used in IS 1893 seismic capacity assessment.

Minimal Intervention

Single brick removed — wall remains structurally intact during test.

Cohesion Determination

Initial shear strength (c₀) determined per ASTM C1531 Mohr-Coulomb method.

NABL Certified Reports

All results on NABL-accredited letterhead per ASTM C1531.

Multiple Locations

Tests at multiple locations provide representative shear strength distribution.

Test in Action

Masonry Mortar Joint Shear Strength Index Test — Site Images

Vertical Joint Mortar Removed for Test

Hydraulic Jack Applying Shear Load to Brick

Shear Failure Along Bed Joint Recorded

Test Procedure

How the Masonry Mortar Joint Shear Strength Index Test is Conducted

1

Brick Selection

A brick unit in a representative location is selected. Adjacent vertical joint mortar removed carefully.
2

Loading Plate Placement

Steel loading plate and hydraulic jack positioned to apply horizontal shear load.
3

Normal Load Measurement

Existing vertical compressive stress on test brick measured or calculated.
4

Shear Load Application

Horizontal load applied at constant rate until brick slides along bed joint.
5

Shear Strength Calculation

Shear strength = peak shear force / brick face area. Cohesion c₀ determined. NABL report within 48 hours.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
ASTM C1531	Standard Test Methods for In Situ Measurement of Masonry Mortar Joint Shear Strength Index	Shear Test	ASTM
IS 1905	Code of Practice for Structural Use of Unreinforced Masonry	Masonry Design	Indian Standard
IS 1893	Criteria for Earthquake Resistant Design of Structures	Seismic Assessment	Indian Standard
ASCE 41	Seismic Evaluation and Retrofit of Existing Buildings	Seismic Retrofit	ASCE

Applications

Where is the CAPO Test Used?

Seismic vulnerability assessment of unreinforced brick masonry buildings

Post-earthquake safety evaluation of damaged masonry structures

Heritage building seismic retrofit design parameter determination

Structural assessment of aging government and institutional masonry buildings

Pre-renovation structural assessment of old masonry load-bearing buildings

Research on masonry mortar bond and shear properties

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid shear strength certificates for seismic assessment compliance.

IS 1893 IntegrationResults formatted for direct use in IS 1893 seismic capacity calculations.

Heritage Building ExpertiseExperienced in masonry testing on listed and sensitive historic structures.

Pan-India CoverageNDT teams across all 7 lab locations.

Fast 48-Hour ReportComplete shear test and NABL report within 48 hours.

Combined Masonry PackageShear strength + Flat jack + Rebound hammer as complete masonry assessment.

Masonry Mortar Joint Shear Strength Index Test(In-Situ Shear Strength — ASTM C1531)