9 9 Research Note:: Determination of Strengths of Construction Materials Applying the in Situ Twist off Method

Since for some reasons such as studying the behaviour of old construction materials and proper replacement of the deteriorated sections, adequate knowledge about the true in situ strength of the construction materials has become a necessity, many attempts have been made to invent and develop new in situ methods in recent years. Most of these methods measure the in situ strengths of materials indirectly by measuring properties other than the strength and relating them to strength by some defined relationships. This paper introduces an innovative partially destructive method, called “Twist-off”, for the assessment of in situ concrete, mortar, and masonry strengths of materials used in buildings and structures. In addition to the laboratory results, the results of the successful application of this method on site are also presented in this paper. Based on the results obtained, the use of this new in situ method with its advantages of simplicity (no need for experts), low expense, cheap and simple apparatus, little damage to the surface area, and high accuracy is strongly recommended for the determination of in situ strengths of construction materials (concrete, mortar, and masonry) used in different buildings and structures.