The carbonation of the concrete in the air is an unavoidable natural process

Itmakes the volume and strength of the concrete change and the alkality reduce

So the structure in-side concrete and the durability both become worse. The carbonation resistance of the autoclaved sil-icate concrete is tested by the means of speeding up the carbonation artificially and also with the ex-periment of the natural carbonation for 6 years. It is very good for recognizing it correctly andspreading.The carbonation of the new concrete material is discussed.