Experimental Research On Directional Static Crack Of The Concrete Beams

Because the advantages of the static cracking agent is very clear,for example,main raw material is low cost?wide source,simple construction,application of no noise?no stone,it is applied widely.For some breakup projects,especially in local breakup and broken projects,the static cracking agent is required to achieve a good cracking effect.This paper summarize and analyze the domestic and foreign research,theoretical analyze principle of the static cracking agent cracking mechanism and guiding device action.The paper determine the swelling properties of static cracking agent.And a series of directional static cracking test of concrete beams are conducted to analyze cracking morphology and strain changes,and study the cracking migration regular of concrete beams.The test of expansive performance of static crushing agent was carried out with different water temperature and ambient temperature.The change of temperature-time curve of test with ambient temperature of 6.2? and water temperature of 24.2? is the slowest,but the volume expansion rate reaches the maximum of 3.91 times,while that of test with ambient temperature of 12.5? and water temperature of 30.3? is the fastest;The maximum temperature of test with the water temperature of 24.2? and ambient temperature of 12.5? is 241.9?.In the test,the jet hole phenomenon occurred in test with increasing ambient temperature and water temperature.Directional cracking test of concrete beams,the dimensions of the beams are also 1100mm×250mm×200mm,set up two groups which are no guiding equipment and having slotted guiding steel tube.Each group used two ways of fill hole,all hole filing agents and septum filling.The results showed that,the initial cracks always occur at the most outside of the concrete beam.For the beam without guiding equipment and septum filling,crack propagation around the part of the filling hole is similar to that of single hole on concrete block.The beam finally generate multiple main cracks and break them into many separate bodies.And there are three beams with slotted guiding steel tube or all hole filling agents,which usually generate a main crack that crosswise through the filling hole and two longitudinal secondary cracks.Finely they break into three or four parts which are not completely separated.Inside,with all hole filing agents,the main crack width of beam without guiding equipment is the maximum of 41.6mm,and that of beam with slotted guiding steel tube is the minimum of 30 mm.From the strain curve analysis,the value of strain far away from crack location tend to be horizontal and the change value is small.The strain near the crack location is generally subjected to tensile force,and the strain value will increase rapidly and then decrease.The longitudinal measurement of the beams without guiding equipmet and septum filling are most changed,which correspond to the development of the cracks.The Directional cracking test results show that the direction of the crack of the concrete beams without guiding equipment and septum filling is unforeseeable,and the effect of the cracks is the worst.While the direction of the main crack of the beam with the slotted guiding steel tube or all hole filing agents is foreseeable,and the number and width of the secondary cracks is small.So the directional cracking effect of that beams is better.In which,the directional cracking effect of beams with all hole filing agents are better than that of the septum filling.And the effect of directional cracking of the beams with slotted guiding steel tube is better than that of the beams without guiding equipment.