Experimental Study On Durability Of Iron Mine Tailings Self-compacting Concrete

The research, by the Chinese fifth big iron ore in Huoqiu as projectbackground and in response to the idea of sustainable development of greenenvironmental protection, energy-saving emission reduction,based on thepresent research situation of self-compacting concrete，develop and utilizewaste residue synthetically.Respectively by20%,40%,50%,60%and80%ofwaste iron tailings (hereinafter referred to as: IMT) as fine aggregate toreplace natural sand to configure iron mine tailings self-compacting concrete,the durability was studied deeply through the early autogenous shrinkage,freeze-thaw cycle and water permeability test.The corresponding researchworks were summarized as follows:1. The early autogenous shrinkage performance of the natural sand SCCand iron mine tailings self-compacting concrete (ISCC1~ISCC5) have beenstudied. The experimental results showed that the early shrinkage of two kindsof self-compacting concrete (SCC, ISCC) could be divided into two stages ofrapid contraction and gentle contraction.They mainly occurred in the early age.SCC and ISCC1~ISCC5showed rapid growth trend in the rapid contractionstage, and the18h autogenous shrinkage of them up to the65%~80%of72h.Except the ISCC2with40%IMT, the autogenous shrinkage of the otherkinds of iron mine tailings self-compacting concrete (ISCC1, ISCC3~ISCC5)were greater than the natural sand in SCC. And the autogenous shrinkage rateof ISCC2in each contraction age was minimum.2.Basing on the correlation analysis of loss rate of cube compressivestrength, mass loss rate and relative dynamic elastic modulus with freezingand thawing cycles (N), The durability of natural sand SCC and iron minetailings self-compacting concrete (ISCC1~ISCC5) have been researched andcompared. In the5kinds of iron mine tailings self-compacting concrete(ISCC1~ISCC5), the mass loss in frozen thawing period basically showed atrend of increase following with the increase content of IMT and IMT ratio of40%in the freeze thawing period had the least mass loss. From the curve ofrelative dynamic elastic modulus of ISCC1~ISCC5, N also follow a rule. When the IMT ratio increases in the20%to40%range, the relative dynamicelastic modulus increases gradually but freeze-thaw resistance decreased withtoo high IMT ratio. From the overall change curve of the cube compressivestrength loss, ISCC5with the largest loss value was the200%of SCC. Therelationship curves of three indicators of freeze-thaw performance showed that,the index of SCC and ISCC2had good frost resistance.3. Through the study of the correlation of the average water penetrationheight and the ratio of IMT and the compressive strength of natural sand SCCand iron mine tailings self-compacting concrete (ISCC1~ISCC5), the textdrew to conclusion that ISCC2with the least water penetration height wassimilar to that of SCC.The average water penetration height of iron minetailings self-compacting concrete (ISCC3~ISCC5) were greater than thenatural sand SCC. The average water penetration height of ISCC4and ISCC5height were relatively large and the average height was about150%of SCC.The average water penetration height of SCC and ISCC2were decline with thegrowth of strength.And by means of regression analysis, the results showedthat the correlation coefficient of cube compressive strength and the averagepenetration height of self-compacting concrete ISCC2and the self-compactingconcrete SCC were0.8545,0.8864respectively.