Assesment of Relative Surface Hardness of Existing Concrete Member by Schmidt Hammer

S. V. Chandramouli, Manager (Technical) Sindhu S Saraswathi, Manager (Technical Services); Sharad R Pothnis, Business Executive-NDT, and Ravikumar, Market Development Engineer, BBR (India) Pvt. Ltd., Bangalore.
Concrete structures as many other engineering structures are subjected to deterioration that affect their integrity, stability, and safety. Faced with the importance of the damages noted on the structures, the current choices are directed towards the repair of the existing structures rather than towards the demolition and construction of new ones. But before any repair work being done, it is a common practice to study the existing structures by analysis after ascertaining the quality of material. Destructive methods of evaluation are inherently limited because specimen removal may be relatively expensive, aesthetically unpleasant and structurally damaging. The number of specimens taken may be limited to a small number for such evaluation method. Thus, potentially, the quantity and quality of the resulting data may be poor and/or inconsistent. Non-destructive Testing is usually undertaken as part of the detailed investigation to complement the other methods. The conclusions of the investigation are based essentially on these tests. The use of Schmidt hammer is commonly accepted for the preliminary assessment of surface concrete strength as the non- destructive test. This article discusses the assessment of existing concrete member by the use of Schmidt hammer and highlights few application importance and limitations for repair and rehabilitation projects.

Introduction

Concrete structures as many other engineering structures are subjected to deterioration that affect their integrity, stability and safety. Faced with the importance of the damages noted on the structures, the current choices are directed towards the repair of the existing structures rather than towards the demolition and construction of new ones. But before any repair work being done, it is common practice to determine the causes of the deterioration so that successful repair can be done. Many repair work fail because the exact causes of the deterioration was not adequately identified. This identification process comprises many methods including non-destructive testing methods. Non-Destructive Testing (NDT) is usually undertaken as part of the detailed investigation to complement the other methods. The conclusions of the investigation are based essentially on these tests. A correct assessment of a deteriorated structure is a crucial basis for the success of a repair system. Experience has shown that in many cases repairs fail much earlier than expected due to improper diagnosis of the actual situation of the structure, either because the cause of the degradation was not properly understood, or the extent of the damage was under-stated. The strength of the concrete structure will vary by age but its rate may depend on various factors. Since, the use of Schmidt hammer is commonly accepted for the preliminary assessment of concrete surface hardness as the non destructive test, this will provide useful estimation of the uniformity of concrete and measure the strength of existing surface concrete and to detect weak spots. This article discusses the assessment of surface hardness of existing concrete member by the use of Schmidt hammer and highlights few application importance, and limitation for repair, rehabilitation projects.