SHRINKAGE OF HIGH STRENGTH NATURAL LIGHTWEIGHT AGGREGATE CONCRETES

摘要

High strength lightweight concretes are usually produced by using costly artificial aggregates. Since Turkey has rich reserves of natural lightweight aggregates a research study was undertaken to investigate the possibility of using them to obtain such concretes. Three types of pumice stones and one volcanic tuff selected from various parts of the country were used to produce a series of structural natural lightweight aggregate concretes having relatively high strengths. Lightweight stones were used as coarse aggregate and sands of normal weight were used as fine aggregate in the concrete mixtures which also included silica fume by 15% of cement and superplasticizing admixture by about 2% of total cementitious material. They attained 28-day compressive strengths reaching 50 N/mm~2,without exceeding dry unit weights of 1850-2000 kg/m~3. Laboratory tests on plastic shrinkage indicated that high strength lightweight concrete mixtures suffered more cracking compared to normal weight concrete, however on equal cementitious material basis there was not much difference. Similar conclusions could be drawn from the results of the accelerated drying shrinkage tests.