Research On Radon Exhalation Rate Limits Of Building Materials

It has become widespread consensus to achieve the purpose of control indoorradon concentration through the use of smaller radon exhalation rate building materials,as building material has become the main source of the indoor radon in the modernhigh-rise buildings. However, both at home and abroad, now there is only limited toindoor radon concentrations. Very Few countries and regions have made the limit tobuilding materials’ surface radon exhalation rate. What is more, the current lack ofrelationship research among the indoor radon concentration, the metope radonexhalation rate and the building material surface radon exhalation rate, as well as thelack of system researches on building material surface radon exhalation ratemeasurement method and the measuring effect factors. So taking these researchescould provide the basis on the controlling of indoor radon protection through buildingmaterial surface radon exhalation rate and on accurately measuring building materials’radon exhalation rate, which have very important practical significance on indoorradon protection.This paper, firstly, has theoretical studies and experimental verifications on therelationships among indoor radon concentration, metope radon exhalation rate andbuilding material surface radon exhalation rate. Then it has a consideration to theradon exhalation rates limits of the walls and the building materials in typical livingrooms which under the normal circumstances. Secondly this paper has someresearches on the effect factors of measuring building materials’ radon exhalation rateswhen using the confined test cabin taking autoclaved aerated concrete for example.The effect factors mainly include water content, temperature, humidity, number ofsamples, size of samples, surface handled of samples and so on. Then there are somediscussions about the method of measuring the building materials’ radon exhalationrates with autoclaved aerated concrete for example. Through these researches, it could provide a foundation for setting up ameasuring method of building materials’ radon exhalation rates. In this paper someconclusions were draw below:1. The researches on the ways to calculate the radon exhalation rates limitedvalues of building materials.1) The results show that the indoor radon concentration varies exponentiallywith time. The relationship between the walls and the indoor radon concentration is:2) The total of the radon which exhale from the surface of the aerated concreteblock will keep constant and the radon exhalation rate is in inverse proportion to radonexhaling surface area when the aerated concrete blocks’ thickness is less than0.4timesof the radon diffusion lengths in the samples.3) The relationship between the building materials’ radon exhalation rates andthe indoor radon concentration is:4) The radon exhalation rate limited value of the walls is34.2Bq·m^-2·h-1and theradon exhalation rate limited value of the autoclaved aerated concrete（size:200mm×200mm×600mm） is15.2Bq·m^-2·h-1in typical living rooms which under thenormal circumstances(ventilation rate is0.3h^-1; the indoor radon concentration is200Bq·m^-3).2. The researches on the measuring method of building materials.In this part the results indicate that the radon exhalation rates on autoclavedaerated concrete has a logarithmic relationship with its moisture content; thetemperature and ambient humidity is mainly through changing the moisture to changethe radon exhalation rate of the samples; the number of the samples has no influenceon the samples’ radon exhalation rate when measuring the radon exhalation rate withtest cabins, but the increasing number will improve the measurement accuracy; thesizes of the samples have a great impact on their radon exhalation rates. The radon exhalation rates on the samples’ surface would decrease with the increasing of the ratioof the sample’s radon exhaling surface area to its volume when the aerated concreteblocks’ thickness is less than0.4times of the radon diffusion lengths in the samples.