Abstract: The conditions and featwres of critical damage are firstly investigated for cement concrete in this paper.Futher,the renormalixation group model and stationary point equation are established. With the aid of normal treatment of damage,the area density of critical damage is obtained,which coincides with exporienccd values. The results have practicaI mean-ing to damage mechan ics an alyses of cement concrete and other brittle materials.

Key words: cement concrete, critical damage, crack evalution, density, scale, geometrical self-similarity, renormalixation

摘要： 本文分析了水泥混凝土临界损伤形成的条件和特点，进而，建立了重正化群模型和不动点方程；通过对损伤的规范化处理，求出了临界损伤面积密度，与经验值较吻合．本文结果对水泥混凝土及其它脆性材料的损伤力学分析有实际意义．

关键词: 水泥混凝土, 临界损伤, 裂纹演化, 密度, 标度, 几何自相似, 重正化