Gradation design method of coarse aggregate for interlocking-dense cement concrete

According to the roles of coarse aggregate in cement concrete,the aggregate filling ratio was put forward to present the relationship between coarse aggregate gradation structure and aggregate particle.Based on particle interference theory and particle filling theory,the design idea of volumetric method was consulted,the gradation design method of coarse aggregate with interlocking skeleton structure for cement concrete was put forward,and the corresponding design software was developed.On the basis of cement concrete design requirements of testing project,the coarse aggregate gradation was calculated,and the design mix proportion of interlocking-dense cement concrete was determined by using software.Furthermore,the concrete performances were tested and verified.Test result indicates that the coarse aggregate gradation with interlocking skeleton structure directly determined by using the software is more coarse than the lower limit of the gradation range recommended by the technical specification for construction of highway cement concrete pavements(JTG F30—2003),and its whole skeleton structure is better.The slump of interlocking-dense cement concrete is 25 mm and meets the workability requirement 10 to 30 mm.The 28 days flexural strength is 7.9 MPa,which is greater than the preparation strength 7.7 MPa and meets the design strength requirements.The maximum number of frost cycles tested by using quick freezing method is 250,and the froze-resistance index is 49.2%,which meets the frost cycles requirement 200 for cold region.5 tabs,2 figs,19 refs.