Use of pumice aggregate in cementitious rheoplastic lightweight concrete

Abstract

Rheoplastic lightweight concrete (RLC) is generally designed for pumping applications as fluid concrete free from segregation. Concrete is produced using polymeric admixtures to enhance concrete workability, strength, drying shrinkage, and durability. This research investigated the suitability of natural porous pumice aggregates in Turkey to obtain rheoplastic lightweight concrete with cement content in normal ranges. To produce and experience rheoplastic concrete mix design data, rheoplastic lightweight concrete mixes were tested with fine pumice aggregate (FPA) and coarse pumice aggregate (CPA) supplied from the Nevşehir region of Turkey. For rheoplastic lightweight concrete with cement contents in the 250 to 400 kg/m3 range, the percentage of fine pumice aggregates required was in the 73.6-81.0% range with complimentary water/cement ratios of between 0.53 and 0.68. The upper compressive strength limit was circa 30 N/mm2 . The research findings determined that the rheoplastic concrete samples with pumice aggregate met the design requirement of a slump value of 200 mm for fresh concrete predicted for fluid concrete forms. While technical properties of hardened concrete such as oven-dry density (1198-1362 kg/m3 ), strength values, static elasticity modulus (9236- 10756 MPa), thermal expansion coefficient (5.354 x10-6/°C - 6.929x10-6/°C) and thermal conductivity value (0.405-0.619 W/mK) decrease with increasing aggregate/cement ratios, they increase with increasing cement dosage. In addition, the high amount of fine pumice in concrete composition results in lower drying shrinkage and wetting expansion with decreasing cement dosage. The technical findings showed that RLC might be produced by using a superplasticizer and air-entraining admixtures and mixtures of different sizes of pumice aggregates.