The feasibility of using different generations recycled coarse aggregate（RCA） on structural concrete was fully evaluated by studying the performance of the recycled coarse aggregates and their corresponding concrete...The feasibility of using different generations recycled coarse aggregate（RCA） on structural concrete was fully evaluated by studying the performance of the recycled coarse aggregates and their corresponding concretes, the different generations of RCA were recycled by following the repeated mode of ‘concrete-waste concrete-coarse aggregate-concrete＇. Moreover, the focus was on ‘three generations＇ of repeated RCAs, the RCA was produced by crushing and regenerating the artificial accelerated degraded concrete, the process was designed to follow the nature degradation of the concrete with a coupling action of accelerated carbonation and bending load. The properties of x-generation（x=1, 2 or 3） of repeated RCA were systematically investigated and the compressive and splitting tensile strengths of relating structural concretes（with 70% replacement of x-generation of RCA） were studied accordingly. The results show a competent compressive and splitting tensile strength of 30 MPa at 28 th day of structural concretes with all generations of repeated RAC. And the gradual degraded performance of the repeated RCAs was observed with an increased numbers of repetition（1〉2〉3 generations）, the overall performances of all repeated RCAs fulfill the Class Ⅲ according to Chinese Standards GB25177-2010. Our gained insight demonstrates a feasibility of using at least 3 generations of repeated RCA for the production of normal structural concrete.展开更多
Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literature...Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.展开更多
基金Funded by the National Natural Science Foundation of China(No.51278073)Prospective Joint Research Project of Jiangsu Province(Nos.BY2013024-17,BY2014037-30,and BY2015027-23)
文摘The feasibility of using different generations recycled coarse aggregate（RCA） on structural concrete was fully evaluated by studying the performance of the recycled coarse aggregates and their corresponding concretes, the different generations of RCA were recycled by following the repeated mode of ‘concrete-waste concrete-coarse aggregate-concrete＇. Moreover, the focus was on ‘three generations＇ of repeated RCAs, the RCA was produced by crushing and regenerating the artificial accelerated degraded concrete, the process was designed to follow the nature degradation of the concrete with a coupling action of accelerated carbonation and bending load. The properties of x-generation（x=1, 2 or 3） of repeated RCA were systematically investigated and the compressive and splitting tensile strengths of relating structural concretes（with 70% replacement of x-generation of RCA） were studied accordingly. The results show a competent compressive and splitting tensile strength of 30 MPa at 28 th day of structural concretes with all generations of repeated RAC. And the gradual degraded performance of the repeated RCAs was observed with an increased numbers of repetition（1〉2〉3 generations）, the overall performances of all repeated RCAs fulfill the Class Ⅲ according to Chinese Standards GB25177-2010. Our gained insight demonstrates a feasibility of using at least 3 generations of repeated RCA for the production of normal structural concrete.
文摘Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.
