Studying the production process and mechanical properties of reactive powder concrete: a Hong Kong study

Abstract

Reactive powder concrete is a relatively new cementitious material. Its main features include a high percentage ingredient of Portland cement, very low water-to-binder (cement + silica fume) ratio, a high dosage of superplasticiser and the presence of very fine crushed quartz and silica fume. Coarse aggregate in normal aggregate concrete is completely replaced by fine quartz sand with particle sizes ranging from 150 to 600 μm. Reactive powder concrete is characterised by ultra-high performance in mechanical properties, particularly in compressive strength; and this could be of tremendous interest to construction practitioners. However, production of reactive powder concrete is not yet available in Hong Kong and limited research is available in this area. This study is an attempt to produce reactive powder concrete using local materials under laboratory conditions. Concrete designed from reactive powder concrete and high-performance concrete is experimentally conducted and compared. The results show that the compressive strength, splitting tensile strength and static modulus of elasticity are found to be significantly higher than that of high-performance concrete using the same water-to-binder ratio. It is noted that the rate of strength development of the reactive powder concrete samples is greater than that of high-performance concrete. The difference in strength at a later age is even bigger. Compressive strength of about 200 MPa could even be achieved in 3 days for the reactive powder concrete samples when the samples were heat-treated at a temperature of about 250°C for 16 h, which can be explained by the formation of xonotlite under scanning electron microscopy investigation.