Influence on Type of Cement on The SCC Formwork Pressure During and After Casting

Grzegorz Cygan,Michal P Drewniok,Jacek Golaszewski

doi:10.1088/1757-899x/471/11/112025

Grzegorz Cygan, Michal P Drewniok + Show 1 more

Open Access

https://doi.org/10.1088/1757-899x/471/11/112025

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Abstract

Formworks for SCC are usually designed under the assumption of full hydrostatic pressure. Nevertheless, current research is attempting to explain the mechanism of this phenomenon as observed pressure usually is at the lower lever than expected. This causes formworks for SCC are usually overdesigned. It was noticed the rheological properties of fresh concrete might be a key to predict the SCC formwork pressure. Therefore, knowing the influence of fresh concrete properties on formwork pressure will enable to design formworks more efficiently. This paper presents the influence of type of cement on formwork pressure caused by SCC. Mixes were design under the assumption of equal dispersion ratio. Three types of cement were investigated: portland, blast furnace and composite cement with a different w/c ratio (0.30, 0.40) and in presence of carboxyl ethers superplasticizer. Formwork pressure was determined on the element imitating a column with dimensions of 0.20x0.20m and a height of 1.20 m with casting speed of 7 m/h. Results show the formwork pressure was registered at the lower than hydrostatic level. Rheological properties had an influence on formwork pressure. It was noticed the different cement types had an influence on rheological properties. Lateral pressure reduction over time was observed with the intensity depending on the cement.

Highlights

Mixtures of self-compacting concrete are mixtures with appropriate rheological properties that ensure the ability to fill the mould, cover the reinforcement and remove the air from its volume without the influence of external loads
Current research is attempting to explain the mechanism of this phenomenon as observed pressure usually is at the lower lever than expected. This causes formworks for SCC are usually overdesigned. It was noticed the rheological properties of fresh concrete might be a key to predict the SCC formwork pressure
Lateral pressure reduction over time was observed with the intensity depending on the cement

Summary

Introduction

Mixtures of self-compacting concrete are mixtures with appropriate rheological properties that ensure the ability to fill the mould, cover the reinforcement and remove the air from its volume without the influence of external loads. The necessity to ensure appropriate fluidity and viscosity that ensures the resistance to segregation of mixture components causes many problems in the construction practice. The second reason for this is the lack of generally accepted methods for forecasting the pressure of the mix of self-compacting concrete on the formwork. Formwork for the construction of self-compacting concrete is designed with the condition of hydrostatic pressure. The rheological properties of concrete mixes are highly dependent on the cement type, superplasticizer and w/c ratio. Besides Bingham’s parameters the SCC formwork pressure depends on static yield stress and thixotropic behaviour (At index) [16]. Intensity of those decides about stiffening which leads to pressure reduction.

Materials and concrete composition

Testing procedures

Findings

Conclusions