Production of synthetic lightweight aggregate using reservoir sediments for concrete and masonry

The paper reports the investigation of rotary kiln manufactured lightweight aggregates (LWA) using fine sediment deposits dredged from the Shihmen Reservoir in Taiwan. The physical and mechanical properties of the sedimentary, synthetic LWA were assessed as well as the engineering properties of the lightweight aggregate concrete (LWAC) made from the LWA. The physical properties of the concrete masonry units (CMU) made from the LWA were then measured. The investigation revealed the sediments contain all the necessary elements to enable the bloating and calcining processes within the commercial kiln. When exposed to the high heat of the kiln, the extruded sedimentary material undergoes dramatic changes, developing a hard ceramic shell and a porous core comprised of non-interconnected capillaries. The particle densities of the synthetic LWA produced from the kilning process range from 1010 to 1380 kg/m3. LWAC designs using the synthetic LWA produce compressive strengths comparable to normal density concretes and were 29-35% lighter. The test strengths and densities of the LWAC satisfied the requirements of ACI 318 code for structural lightweight concrete. Additionally, sedimentary LWA could be incorporated in automated production facilities to produce high performance CMUs complying with the requirements of the Chinese National Standards (CNS).