Development of Ultra High Performance Concrete and Reactive Powder Concrete with Nanosilica

L Rundt,R Hela,L Bodnarova

doi:10.1088/1757-899x/371/1/012017

Abstract

The article is dedicated to the design and production of Ultra High Performance Concrete (UHPC) and Reactive Powder Concrete (RPC) using silica fume and nanosilica. Nanosilica and fine steel fibres were used for the production of RPC. Compressive strengths of UHPC and RPC above 150 MPa have been achieved. It has been demonstrated that UHPC and RPC can be produced using standard concrete mixing system without the use of activating mixing and without a special treatment regime during maturing of the concrete. Aging of the concrete took place in a normal environment, without elevated pressure or temperature. The aging process at 20 °C allows the use of UHPC and RPC for the ready-mixed concrete when working on high volume construction projects. Even without thermal treatment, without the application of solidification pressure and without autoclaving, RPC reached a compressive strength of more than 180 MPa and a flexural tensile strength after 60 days greater than 22 MPa. The high tensile bending strength may be considered as the main advantage of RPC, as the RPC parameters allow, for instance, the use for pre-stressed structural elements where a high initial strength is also required.

Highlights

Ultra High Performance Concrete (UHPC) or Ultra High Strength Concrete (UHSC) refers to composite material with Portland cement based binder with a compressive strength of more than 150 MPa, high ductility and excellent durability
The use of UHPC and Reactive Powder Concrete (RPC) in building structures must be seen in the long term due to its excellent durability
The total consumption of cement depends on the particular building, theoretically it may be less when using UHPC, because smaller UHPC volume is needed than conventional concrete, which has a positive effect on the CO2 emissions from the cement production

Summary

Introduction

Ultra High Performance Concrete (UHPC) or Ultra High Strength Concrete (UHSC) refers to composite material with Portland cement based binder with a compressive strength of more than 150 MPa, high ductility and excellent durability. These properties are achieved by high content of cement, low water-cement ratio, using superplasticizers, additives (silica, fly-ash, blast furnace slag, metakaolin) and dispersed reinforcement. High strength is achieved by a very dense structure with optimal granulometry of all raw materials, thermal treatment at elevated pressure before and during setting and hardening, high proportion of siliceous extracts and dispersed reinforcement. The positive side of UHPC and RPC is the ability to produce supporting elements of very thin cross-sections, utilizing high strengths of these concrete, thereby relieving the whole construction and further positive is the high durability and associated sustainability and reduced need for repairs

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