| The resource utilization of fly ash?FA?in coal fired power plants in the central and western regions of China should be solved urgently.FA is employed to sinter ceramsite,and developing a type of high performance concrete materials—ceramsite lightweight concrete?CLC?.CLC has many advantages such as high specific strength,light-weight,thermal preservation & insulation,fire resistance,anti-seismic property,and so on,hence CLC has broad application prospects.Based on the consideration of FA sintering ceramsite as coarse aggregate,and its water absorption properties and adhesion ability with concrete matrix,this paper prepare CLC and self compacting CLC with different content of FA to replace part of cement.The apparent density,workability?pumpability?,mechanical properties,and durability,as well as the feasibility of self compacting CLC were systematically studied,and their corresponding mix ratios were optimized.Conclusions are as follows:?1?Pressure water absorption rate of FA ceramsite is significantly higher than that in normal state;Slump loss at 15 MPa pressure is roughly same as that after 30 min,so the pump pressure of CLC should be controlled in about 15MPa;The apparent density of CLC gradually increases with increasing the amount of cementitious materials,decreased with the increase of the FA content;The 56 d compressive strength of CLC is greatly improved compared with that in 28 d,so we should recommend 56 d compressive strength to assess the strength of CLC at high dosage of FA.?2?We employ 56 d strength of CLC to assess,the cost of LC30,LC35 and LC40 grade CLC with the dosage of FA being 45% is about 221 yuan/m3,231 yuan/m3,and 245 yuan/m3,respectively;Whereas the cost of LC30 grade CLC evaluating by 28 d strength in normal curing and steam curing condition is about 295 yuan/m3,237 yuan/m3,respectively,which is higher than that in evaluating LC45 grade CLC by 56 d strength.Meanwhile,the use of steam curing can greatly enhance the effective content of FA,thereby reducing the cost of production of CLC.?3?The water-binder ratio of high-strength grade CLC is relatively low,its density is good,resulting in good anti-carbonation properties;After 150 times freezing-thawing action,the dynamic elastic modulus and mass loss rate of CLC have little change;Its chloride diffusion coefficient?DRCM?is less than 6×10-12 m2/s;Its shrinkage rate is low(only for 56×10-4);Its anti-cracking grade is L-III level after 24 h wind blowing;These above index meet durability requirements.?4?The compressive strength of self-compacting CLC has a linear increasing with doping of cementitious materials;Self-compacting CLC has high early shrinkage,7d shrinkage accounts for about 70% of the total shrinkage;The increase of FA doping has adverse effect on anti-shrinkage properties and impermeability of self-compacting CLC;when the dosage of FA is 30%,the DRCM of self-compacting CLC is more than 6×10-12 m2/s,and is 2.64 times than that with 15% FA dosage. |
PDF Full Text Request