Study On The Influence Of Wind And Ambient Temperature On Continuous-casting Length Of Large Area Slabs-on-ground

In the construction of large area slabs-on-ground, the most serious problem ofconstruction quality is cracking caused by shrinkage of concrete. And that makes someirreparable damage on structure and building function. The continuous casting length ofslabs-on-ground in every construction segment is one of those factors that determine therestraint stress. It directly related to capacity of slabs-on-ground to resist cracking. Inthe developing of construction program, determining the length of continuous casting isthe part strictly controlled for preventing cracking. Determining the length ofcontinuous casting is most importantly based on cracking spacing defined as “L”.“L”means the maximum possible spacing between two cracks on the slabs-on-groundwith a certain restraint.In addition to restraint, the value of “L” is also determined by the shrinkage, tensilestrength, elastic modulus, temperature deformation, thickness of concrete slab. Theshrinkage, tensile strength, elastic modulus and temperature deformation defined as“Four Basic Factors” are time-dependent during construction. So that “L” determinedby “Four Basic Factors” is time-dependent as well. Wind and ambient temperature areable to influence cracking on concrete slab indirectly through influencing the“FourBasic Factors” Study on the influence of wind and ambient temperature on crackingspacing of large area slabs-on-ground is useful for determining the length of continuouscasting correctly.In order to research influence of wind and ambient temperature on crackingspacing of large area slabs-on-ground, the three steps work is completed.Step number1: Based on researching mechanism of wind and ambienttemperature’s influencing on the “Four Basic Factors”, and analyzing the results of thosecomplished tests on shrinkage, tensile strength and elastic modulus of concrete testspecimen, the conclusion that increasesing of wind speed and temperature both reducesvalues of “Four Basic Factors” under conditions of no concrete curing was obtained.The reducing effect of temperature is more obvious. These characteristics and forms ofshrinkage, tensile strength and Modulus of Elasticity’s growth were taken as the basis ofanalysis on cracking Spacing. Reasonable functions were obtained by fitting the tests’result.Step number2: The process of working out the temperature field by using different method considered the influence of wind and ambient temperature on temperatureinside concrete slab. By analyzing these calculation results, conclusion shows that theincreasing of wind speed reduces the amount of temperature rise in concrete slab whilethe the increasing of ambient temperature increases it.Step number3: Based on fitting function and temperature field, the curve of “L”variation was obtained by improved calculating method. The form of wind and ambienttemperature’s influence on cracking spacing was analysed systematically. The mainconclusions obtained were that:(1) Both the increasesing of wind speed and ambienttemperature reduce the value of continuous casting length of slabs-on-ground andincrease the risk of cracking in early age.(2) The effect of ambient temperature is moreobvious.With these works and analyzings, large area slabs-on-ground’s cracking form undercertain condition of wind and ambient temperature was known. These findings arereliable basis for determining the length of continuous casting correctly...