Rheologische Messungen an Baustoffen 2019

Tagungsband zum 28. Workshop und Kolloquium, 13. und 14. März an der OTH Regensburg

Markus Greim, Oliver Teubert, Wolfgang Kusterle

• Verlag: tredition
• Jahr: 2019
• ISBN:
  9783748246534
• Thema: Technik & Maschinenbau
• Thema: Maschinenbau Allgemein

Rheological measurements help to optimize the robust application of building materials. For the past few years applied rheology has been moving increasingly into the center of attention of the civil engineering society. Advanced testing equipment, intensive research and development work have all helped to deepen the understanding of this field. Last but not least, different conferences, such as the 28th Conference on the Rheology of Building Materials at the OTH, have helped to exchange the findings and establish valuable new contacts. Finding a compromise between rheological theory and its practical application has been the main topic of these 28 conferences.In these proceedings important rheological topics are addressed: specific applications of concrete such as self-compacting concrete, tremie concrete and sprayed concrete and mortar mixes for 3D printing, which all may be classified as self-compacting concretes. The consideration of time- and temperature-dependent changes in workability are essential for a successful application of these materials. Furthermore, the influence of the mixing energy used and the way of casting/spraying is of high importance for the rheological properties. The rheology of other concrete types is drastically changed due to the compaction by vibrators.Concrete rheology is controlled by its paste content and the rheology of the paste. Tests on pastes are easier to perform, as particle migration of aggregates is not present. However, one has to ask whether it is sufficient to use the results from the paste-measurements for the assessment of concrete and how the optimized paste content will be predetermined. The other question is which admixtures or additives may help to improve the very different application processes. Apart from using superplasticizer and stabilizers, entrained air is a powerful tool to influence rheology.

The injection process – effecting mechanical properties?

B.Eng. Ludwig Hertwig, Prof. Dr.-lng. Klaus Holschemacher

HTWK Leipzig, Structural Concrete Institute, Leipzig, Germany

Phone: [phone], e-mail: [email protected]

Abstract

Injection as a novel manufacturing process for high-performance mortars in connection with fibres or textile reinforcement represents a powerful alternative to the pouring process. The subject of the investigations is the question if the use of the injection process compared to the pouring process not only provides better handling in the manufacturing process but also adds value in terms of the properties of hardened concrete. Subsequently, test specimens (cylinders with d=100 mm, h= 150 mm and cubes with edge length a = 150 mm) were produced using pouring and injection process with the mixtures SCM 1, ECM la and LWSCM 1. The influence of the manufacturing process was assessed by the evaluation of hardened concrete properties like density, compressive strength, modulus of elasticity, water penetration depth and water absorption. The used formwork allowed the production of three test specimens on top of each other. This procedure enabled the investigation of various influencing factors as a function of the concreting height. The use of SLIPER (Sliding Pipe Rheometer) provided information on pumpability and reference values of rheological parameters to estimate injectability for the tested mixtures.

1 Introduction

The development and application of high-performance concretes and mortars¹ follows the desire for slim, lightweight and load-compliant design. For the production of such constructions, the following manufacturing processes are available to the user to date: Spraying, shotcreting, spinning, laminating and pouring [2].

Table 1 shows the manufacturing processes from the textile concrete sector where HPMs are commonly used. The application of the centrifugal process is limited to rotationally symmetrical and similar cross-sections in its range of applications. The spray, shotcreting and laminating process cannot guarantee an architectural concrete quality on all component surfaces, as not all sides can be produced smooth. Now, for the production of thin-walled, 3-dimensional building products in architectural concrete quality, the pouring process is of primary practical interest.

Table 1 Manufacturing processes in the textile concrete sector with possible component types, reinforcement and areas of application according to [2]

production techniques	component geometry	textile	component
laminate	2D components	2D textile, uncoated, degree of reinforcement almost arbitrarily controllable	facades, slabs
pouring	2D and simple 3D components	2D or 3D textile, uncoated and coated, reinforcement content limited by tightness ofthe structure, spacers necessary	facades, formwork elements, sandwich panels
shotcreting	2D and 3D components	2D textile, uncoated, degree of reinforcement almost arbitrarily controllable	plates in horizontal and vertical position, shells
centrifuging	circular hollow sections	2D or 3D textile, uncoated and coated, degree of reinforcement almost arbitrarily controllable	tubes, masts, piles

The production of complex and thin components by pouring is highly dependent on the rheological properties of the mixture. However, since self-compacting concretes and mortars are susceptible to segregation [3], the formation of the maximum flowability is risky. In addition, the process is time-consuming and labour-intensive, subjective application errors can easily occur.

The injection² process meets these challenges and therefore, it is an effective process for the production of high-performance mortars. The process uses the compression and distribution energy of the applied pump pressure. This may extend processing time significantly and reduces the cement and superplasticizer (SP) contents. Filling from below ensures that the fresh concrete level in the formwork rises evenly. The fresh concrete level increases constantly and thus the pump presses the matrix from below against flow barriers (reinforcement, geometry). The entire fresh concrete is in motion and thus spreads better.

The aim of the investigations is to find out whether the injection process improves, in addition to the advantages mentioned above in the fresh concrete sector, the properties of hardened concrete in comparison to the pouring process.

2 Case studies

2.1 Materials and test setup

For the injectability of mortars, there are currently no recommendations regarding the mix design. Therefore, it was assumed within the scope of these investigations that the mixing concept of a self-compacting mortar is target-oriented. Within the experiments, four different types of high-performance mortars are used (mix designs see Table 2):

• laboratory mixes: self-compacting mortar (SCM 1) and lightweight self-compacting mortar (LWSCM 1)

• industrial products: easy-compacting mortars (ECM 1, ECM la, ECM 2, ECM 2a) and grouts (G1,G2)

Table 2 Mix designs of used mortars showing masses, water-binder-ratio (w/b) and calculated density

Table 3 Experimental program for comparison of pouring and injection regarding hardened concrete properties

To evaluate possible differences between the manufacturing process two normal concretes (SCM 1 and ECM la) and one lightweight concrete (LWSCM 1) are chosen. The workability of the easy-compacting mortar (ECM la – in...

Inhaltsverzeichnis

• Cover
• Urheberrecht
• Inhalt
• Preface
• Scherinduzierte Partikelmigration: Relevanz bei Theologischen Messungen an Mörteln und Betonen
• Effect of the mixing time on the rheological parameters of cement pastes
• Advanced Admixtures to control Rheology of Tremie Concrete for Deep Foundations
• Analysis of the effect of various limestones in the cement composition on rheological properties of mortar
• Investigations on the influence of paste composition on the rheological properties of flowable mortars and concretes
• Rotatorische und oszillatorische Scherversuche zur Ermittlung steifigkeitsrelevanter Kenngrößen von Offshore-Vergussmörteln unterdem Einfluss des Early-Age Movement
• Rheology as a Tool to Characterize Dissolution and Reappearance of Air under Pressure in Cement Pastes
• The injection process - effecting mechanical properties?
• Adhesive mortars properties: Squeeze Flow and Contact Visualization
• Rheologische Unters, an Frischbetonmischungen für Spritzbeton