Direct electric curing of mortar and concrete
Direct electric curing is the method by which the hydration reactions within concrete are thermally accelerated by passing an alternating electric current through the sample. This use of electricity as a means of supplying heat to young concrete and mortar has become recognised as a more effective and energy efficient form of accelerating the curing process than traditional steam curing. The present investigation involves studying the affects of thermally accelerated curing of cementitious materials in comparison to normally non-heated curing. Prior to mixing, tests are performed on the constituents of the cementitious mixes. Results of these tests are used in the creation of mix designs for mortar and concrete samples. A range of concrete mixes are designed with and without additives and admixtures are used to make cubes, slabs and beams. From the testing results, the factors affecting the short and long term properties of electrically cured cementitious materials are investigated and heating regimes are presented to achieve specific properties of both strength and durability at specific ages. A substantial section of reinforced concrete is required to gain representative results in electrically curing reinforced concrete slabs. Compressive strength is difficult to measure due to the electrical distortion affects of inserts and the damage caused by coring so that at present, basic maturity concepts are used as a compressive strength guide which limits the validity of results obtained. This research looks at refining these concepts to include early age heating effects induced by direct electric curing. The microstructural development of concrete when subjected to accelerated curing is also considered. The affect of delay periods and maximum temperature is studied using a scanning electron microscope and the results presented.