Standards Development

Scope

This document specifies the method for determining the tensile bond between sprayed concrete and substrate of concrete or rock tested in a laboratory or in-situ. Bond strength is defined as the capacity to transfer tension between two layers. This document does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Purpose

Sprayed concrete (shotcrete) has been widely used in stabilization and support of structures for its fast setting and rapid hardening properties. Presently sprayed concrete has replaced the traditional methods of lining tunnel profiles and has become very important in stabilizing the excavated tunnel section. Without sprayed concrete the construction of modern tunnelling is inconceivable. In comparison with conventionally poured concrete, sprayed concrete requires far less formwork and adapt to any substrate to form complicated curved shapes, which are impossible to achieve using conventional formwork.

For the reasons of rapidly increasing mobility and limited space, the need for underground infrastructures will continue to grow. Sprayed concrete is also widely used in the fields of mining, slope protection, repairing work and civil engineering projects. Bond strength of sprayed concrete is the fundamental performance required and to be evaluated during constructions. Justification: During tunnel construction, The bond strength of sprayed concrete is a core performance indicator that determines the overall integrity, long-term stability, and durability of the structure. Adhesive failure will directly lead to delamination, peeling, and even structural instability, causing significant safety hazards. The standard for testing the bonding strength of sprayed concrete is developed to ensure consistency, comparability, and accuracy in the evaluation of bonding performance, providing a solid basis for the quality control of tunnel construction. So far there is no ISO standard for test method of bond strength for sprayed concrete, so drafting the test method for bond strength of sprayed concrete is of priority importance to provide support for the performance evaluation and quality control of sprayed concrete, and also an important basis work for the development of sprayed concrete and technology.