Damage to reinforced concrete structures in the form of spalled concrete may occur either as a result of reinforcement corrosion, impact damage, or from the effects of fire. A widely accepted method of patch repair is by making use of either resin mortars or polymer modified cementitious systems. At the present time the durability of such methods, particularly to chloride attack, is the subject of several independent studies. However, these materials may have very different thermal and time-dependent properties to the steel or concrete to which they are bonded. This aspect of the concrete repair process has so far received little attention. An experimental and analytical programme of research is in progress to evaluate the structural integrity of such patches. The paper describes the initial test series involving patch repairs within both the tension and compression zones of flexural specimens. Repair materials having a wide range of elastic and thermal characteristics have been used in patches of varying shapes and sizes. Their effect on short-term structural performance is assessed and conclusions drawn as to the relative performance of a range of systems. (Author/TRRL)