Analysis Of Influence Factor On Concrete Strength And Research On Evaluation Method

The quality control takes the first place in construction project management,and the strength inspection and evaluation plays a critical role in the quality control for concrete.If the concrete strength can't be evaluated scientifically,the normal project construction and the final acceptance and safety of project structures will be affected.As a mixed material,the strength of concrete is affected by many factors.This paper makes a detail analysis on the factors that influence concrete strength and its evaluation,for example, the selection of raw concrete materials,design of the proportion,measuring agitation and other production process;transportation,construction process,maintenance after pouring and other construction process,specimen forming and conservation and other test control,as well as the quality control on concrete by associated supervision and regulation apartments,the analysis has shown that an easy and intuitive assessment of concrete strength while focusing supervision and regulation on concrete production,construction and test process,so as to reduce the uncertainties that influence the evaluation.The evaluation of concrete strength is mainly through the strength of "standard conservation test block" and that of "conservation test block under the same conditions".When suspecting the representatives of concrete strength of test block,the concrete strength may be evaluated by micro-destruction or non-destruction inspections according to relative standards.This paper find out by analysis that there exists a large difference in size,way of pouring,conservation conditions(temperature,humanity,age) between "conservation test block under the same conditions" and actual structural component. Therefore,the strength of "standard conservation test block" is different from the actual concrete strength of structural component."Conservation test block under the same conditions" is also different from structural body in forming process,volume and surface area ratio and conservation effect and affected easily by personal factors,so as to have difficultly "the same conditions" as the actual engineering structure,as well as the conversion coefficient is suspicious.For micro-destruction or non-destruction inspections,such as rebound,ultrasonic, acoustic velocity,drawing force,the strength is estimated by indirect evaluation of the relationship between physical quantity and concrete strength.Because of its various influence factors,poor representatives and strength measurement curve is established in the late 1980s and early 1990s,so that it doesn't apply to the current concrete.Boring method is recognized as the best method to approach proximally the actual strength of structural concrete,but various damage accumulations can affect the evaluation of concrete strength in the process of boring,drilling,cutting and grinding specimen,together with expensive equipment,uneasy operation and complicated technique,so as to become difficultly an acceptable inspection method.Considering the above analysis,a new method is proposed,that is,body sampling inspection of concrete strength.The forming and conservation conditions identical to that of actual structure can be achieved by using this method,realizing "the same conditions" as the actual structure and the reduction of influence of uncertainties from the true sense.The paper also makes a detail analysis on the relationship among conversion strength of body sampling specimen,f_cu,s,the strength of standard conservation specimen,f_cu,o,and the strength of conservation specimen under the same conditions,so as to specify their parts in evaluating concrete strength,carry out a new method of concrete evaluation of standard conservation specimen strength combined with body sampling specimen strength and conversion coefficient of conversion strength for C30,C40 concrete body sampling specimen in Harbin area. Practice has shown that this method is easy and affected by less factors so as to use widely and represent the actual structural strength more exactly.It may be an effective tool for the parallel inspection and verification of concrete strength and have greater meaning and value for widespread.