Technical director, Conproco Corp., Hooksett, NH
Accurate correlation between standard test results and observed field performance of repair mortars has been difficult to achieve. A study was conducted in an attempt to understand the development of physical properties and induced tensile stresses as a repair material cures and how these affect the likelihood of early age cracking. A mathematical model was developed to predict when induced stresses may be sufficient to crack a repair mortar while curing. Using this technique, the influence of two polymers on a generic mortar was investigated in the laboratory. The laboratory study included measurements over time of tensile strength, drying shrinkage, tensile modulus of elasticity, and tensile creep. The model's predictions were checked by placing the studied mortars in a simulated repair situation.
The influence of polymers on physical properties, the stress developed while curing, and field performance were studied. Results suggest that the type of polymer has an important effect on properties, such as tensile creep and modulus of elasticity. The data also indicate a balance of certain properties is needed in order to make a repair mortar more resistant to cracking. Further, since these properties change as the material cures, their relationship over time must be understood.
The test procedures, mathematical model, and results are discussed in this paper. Cross references to a simulated field installation is also included.
Paper ID: CCA10143J