Experimental Study On The Strength And The Cracking Resistance At Early Ages Of High-performance Concrete Added With Lithium Slag And Fly Ash

We choose lithium slag and fly ash as the mineral admixture of high-performance concrete. This article studies the influence of water to binder ratio, lithium slag dosage and fly ash dosage on the strength and the cracking resistance at early ages of high-performance concrete added with lithium slag and fly ash by lab experiment. We’d like to find out the best proportioning, the optimum mix amount of lithium slag and fly ash and the optimal fineness of lithium slag from the experiment. The experiment including strength experiment and cracking resistance experiment. In the strength experiment, each factor has five levels while four in the cracking resistance experiment. We set the compressive strength at1day,3days,7days,28days,90days and the splitting tensile strength at28days as strength indicators of the concrete. At the same time, we make the maximal crack width and the crack area on unit area anti cracking performance indicators of the concrete. The result shows:(1) Water to binder ratio has the greatest effect on both strength and anti cracking performance indicators of the concrete. To some extent, the strength is increased first and then decreased with the increase of water to binder ratio, while the anti cracking performance at early ages is enhanced. The optimal water to binder ratios are0.30for strength and0.45for anti cracking performance.(2) Lithium slag has volcano ash activity and micro expansive performance, as a result, it affects the strength and anti cracking performance indicators of the concrete too much. Within the poraver of the experiment, both the strength and the of concrete are increased first and then decreased with the increase of lithium slag dosage. The optimum adding quantity of lithium slag are10%and15%separately.(3) Because the fly ash doesn’t join the hydration reaction at early ages and its filling effect, it can reduce the self shrinkage of concrete and make contribution to the concrete strength in the later period and anti cracking performance at early ages. The optimum fly ash dosage are15%and10%respectively.(4) With the same water to binder ratio, the strength of lithium slag and fly ash concrete is close to pure cement concrete and lithium slag concrete before28days, it’s equal to or higher than them after28days. The strength of concrete added with lithium slag and fly ash grows much in the later period.(5) Under the same condition of proportioning, the early-age anti-cracking ability of lithium slag concrete and fly ash concrete are much better than common cement concrete, and the high-performance concrete added with lithium slag and fly ash is the best among them.(6) To some extent, the cracking resistance at early ages of high-performance concrete added with lithium slag and fly ash is increased first and then decreased with the increase of the fineness of lithium slag. The optimal specific surface area of lithium slag for early-age anti-cracking ability is770m2/kg.