In this paper, a comparative cold weather concrete member test was conducted with gang form and euro form, which are generally used as forms for construction in Korea. Three members were fabricated for the comparative test: the member with the general gang form and euro form, the member with the existing insulation gang form on the outside and the general form on the inside, and the member with the existing insulation gang form on the outside and the newly developed insulation euro form on the inside. In this test, ready-mixed concrete with a nominal strength of 24 MPa that met a certain standard was cast in the cold weather concrete condition at a temperature of 0℃ (5℃ ～–5℃), which is lower than the cold weather concrete management standard temperature in Korea 4℃ mean daily temperature. The standard water curing compressive strength, core compressive strength and temperature history were measured and comparatively examined for the general gang form-general euro form and insulation gang form-general euro form members that were cured at a certain inside temperature, and for the insulation gang form-insulation euro form member that was cured without additional temperature control.
This paper intends to review possible application in the high strength area through compressive strength estimation of the simulated high strength concrete member using Rock Test Hammer and suggest it as a reference data for the strength estimation technique of the ultra high strength concrete in the future. From the results of test, in the low strength area less than 15MPa and normal strength area in 15∼60MPa, as shown on the existing studies, it is indicated that P Type Schmidt Hammer in the low strength area and N Type Schmidt Hammer in the normal strength area have high correlation of rebound-compressive strength. As the Rock Test Hammer indicated more or less reduced accuracy in the low strength area and the normal strength area but high correlation on the high strength area (50∼100MPa) defined on this test, it is determined that it would be possible to make the fastest and simplest compressive strength estimation on the site where the high strength concrete is applied. As was resulted above the experiments, on the basis of the result of Rebound Hardness Method and Compressive Strength on the high strength area which is over 50MPa, the conclusion is drawn which is Fc=4.409e0.059R through regression analizing the relations of Compressive Strength which is based on Rebound Hardness Method.
This paper has fabricated insulation gang-form adhering general gang-form to the polyisocyanurate board and analyzed type of members, temperature record by locations and strength development after placing the concrete, in order to ensure efficient concrete quality under cold weather. According to our test, we can see that general gang-form member with curing under the same conditions as the actual field has a trend of constantly decreasing concrete temperature regardless to surface or central area due to rapid outdoor air temperature reduction, while in the case of insulation gang-from I and II, temperature increased up to around 25℃ after 12 hours under rapid outdoor air temperature change and temperature distribution did not appear large separation according to hydration reaction measurement locations. In addition, results of measurement for temperature records on weak insulation area by types of gang-forms showed that the temperature record distribution on the form tie surface and horizontal bar surface of angle bar has generally similar trend as the temperature records on the surface of the insulation gang-form, while corner area of the insulation gang-form did not have large insulation effect. It is determined that it requires additional curing measure for the weak corner area of the insulation gang-form in the future.
In this study, the drying shrinkage of concrete used for the reduction of expansive additive and shrinkage reducing agent committed to the concrete Mixing characteristics, compressive strength and drying shrinkage of examining my new honhwajaeryoin elements by putting in concrete Their characteristics were compared and analyzed. Experiments, SP was fixed jeryangeul equally expansive additive and shrinkage reducing agent in the formulation of the Injection rate increased with increasing fluidity, shrinkage reducing air flow rates increase the amount of air even if the input Increases with, and if the expansion of re-injection rates increase rather than decrease was found that the volume of air. I committed to the elements of the concrete, but an increase in inputs even if the air content of concrete or no liquidity Were confirmed to have no effect. In addition, the compressive strength test Shrinkage Reducing the dosage increases, Tended strength falls, inflation 5.0% of material inputs in the formulation was found to be the highest. Element material Concrete with Shrinkage Reducing committed a similar compressive strength falls with increasing dosage tended Unlike the small degree of shrinkage reducing agent was affected. Shrinkage characteristics include all three admixture With increasing dosage can reduce the drying shrinkage was observed that, if the shrinkage reducing agent, of the elements and almost Reducing the level of contraction was found to be. Therefore, the element first, if you commit to concrete admixtures to Characteristics of the concrete mix does not affect the lapse rate contract that can be used as a highly admixture is judged to be
This study is analyzing a member kind after placing concrete, the location-based temperature record, and the strength development, by making insulation gang-form with application of polyurethane form to general gang-form for securing efficient concrete quality in the condition of cold weather. According to our experimental results, the member of general gang-form with curing in the same condition as the actual field didn’t drop to under 3˚C until before 24 hours in the early part, but fell to under 0˚c from 36 hours later because a large rise in temperature caused by hydration reaction didn't occur. On the other hand, in case of insulation gang-form, the temperature on the surface and the central part didn't go down to under 3˚C before 12 hours in the early part and didn't fall to under it even until 72 hours after it while the peak temperature went up to 12˚C. Thus, it could be known to definitely have excellent insulation effect compared to space heating curing, which is generally performed on the spot. In comparison with space heating curing whose error in curing temperature is big every field, it is judged to likely have great effect on improvement in concrete quality given the work construction in cold weather and on early demolding in a cast during winter.