Experimental Study On The Mechanics Characteristics Of Double-additives Lightweight Aggregate Concrete

With many excellent characterictics of low apparent density, high strengh, heat preservation and insulation, high earthquake risistance, lightweight aggregate concrete (LAC) develops so rapidly that the quantity of LAC in use is greatest except ordinary concrete. As mineral additive and admixture are used in LAC, it has more large application in stuctural buildings, such as high-storeyed buildings and large-spanned bridges.Because of the particular characteristics of light aggregate, many scholars have researched mechanics characteristics of LAC, such as compressive strength, rupture characteristics and elastic modulus. As the double-additives techinology is in use, the changes of LAC's mechanics characteristics have great influence on the control of LAC quality. Then the paper has given research on compressive strengh, rupture characterictics and elastic modulus of LAC by experiments.At first, the research of the strength at varied age in single-addition or double-additives situation gives the rules of the compressive strength of LAC as the age goes on. On the basis of the rules, the strength of LAC is estimated by the early-aged LAC compressive strength. And the result of the estimation is exact by the formula which is constructed by experiments. What's more, the applicabilities of the rules are better.The research on the influences, which are given on 7 days' and 28 days' strength by the type and quantity of mineral additive, is done. And the experiments show that the strength of double-additives LAC is larger than that of normal LAC at the age of 7 days. However, only the best quantity of mineral additive can make the strength of double-additives LAC larger than that of normal LAC at the age of 28 days. Then the results of this situation are analyzed in macroscopical and microcosmic ways.In the next place, the rule of rupture of LAC, which displays that the brittleness of LAC goes higher as time goes on, is researched by compressive strength and tensile strength at varied age. The relation between rupture of LAC and quantity of additive and kind of additive is researched by adding varied kind additive by different quantity. The results are as follows: the rupture of fly ash LAC is highest at the percent of 20 for fly ash quantity added; the rupture of slag LAC is highest at the percent of 15 for slag quantity added; the rupture of compound admixture LAC is highest when the proportion of fly ash and slag is in the proportion of 2:4 and the total percent of additive is 30.At last, the relation between elastic modulus of LAC and quantity of minerral additive and kind of admixture is researched by adding varied kind additive and adding different quantity. The results are as follows: the modulus of fly ash LAC is highest at the percent of 20 for fly ash quantity added; the modulus of slag LAC is highest at the percent of 15 for slag quantity added; the modulus of compound admixture LAC is highest when the proportion of fly ash and slag is in the proportion of 2:4 and the total percent of admixture is 30.