Concrete is strong in compression, but weak in tension its tensile strength varies from 8 to 14 percent of its compressive strength.
具体是在压缩强劲，但在张力弱：其拉伸强度变化从8至14%，其抗压强度。
2
The viscosity and surface tension was improved by gel structure of bentonite colloid, so the capillary force is increased and therefore the wet compressionstrength is improved.
凝胶结构提高了粘结液相的粘度和表面张力，毛细力增大，生球抗压强度提高。
3
A kind of method to evaluate and test the tension-compression fatigue strength of gray cast iron was introduced in this paper.