The Fabrication, Testing and Application of Fibre Cement Boards

The Fabrication, Testing and Application of Fibre Cement Boards

Edited by

Zbigniew Ranachowski and Krzysztof Schabowicz

The Fabrication, Testing and Application of Fibre Cement Boards Edited by Zbigniew Ranachowski and Krzysztof Schabowicz This book first published 2018 Cambridge Scholars Publishing Lady Stephenson Library, Newcastle upon Tyne, NE6 2PA, UK British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Copyright © 2018 by Zbigniew Ranachowski, Krzysztof Schabowicz and contributors All rights for this book reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. ISBN (10): 1-5275-0576-6 ISBN (13): 978-1-5275-0576-6

CONTENTS Introduction ................................................................................................ 1 Chapter One ................................................................................................. 7 Fabrication of Fibre Cement Boards By Krzysztof Schabowicz and Tomasz Gorzelańczyk

Introduction ........................................................................................... 7 Primary raw materials ......................................................................... 11 Properties of PVA fibres ..................................................................... 11 Raw materials preparation and mixing zone ........................................ 14 Detailed operation of Hatschek machine and fibre film formation ...... 23 Details of other FCB fabrication process stages .................................. 28

Chapter Two .............................................................................................. 41 Fibre Cement Boards Testing By Zbigniew Ranachowski

Mechanical properties of FCB ............................................................ 41 European Standard EN 12467 .............................................................. 42 Measuring board dimensions, tolerances, straightness

and squareness of edges ................................................................. 44 Measuring apparent density ................................................................. 45 Measuring mechanical resistance ......................................................... 46 Testing water impermeability .............................................................. 56 Testing water vapour permeability by the determination

of the water vapour resistance value µ ........................................... 56 Testing moisture content during FCB production process ................... 58 Durability against warm water ............................................................. 65 Durability against soak–dry cycles ...................................................... 66 Moisture movement test ....................................................................... 66 Durability against freeze–thaw cycles ................................................. 68 Durability against heat–rain ................................................................. 69 Reaction to fire ..................................................................................... 69 Information on parameters determined based on standard tests

and indicated on the product label .................................................. 71 FCB testing using ultrasound ............................................................... 71 Application of Lamb waves for detecting structural defects ................ 78

Contents

vi

By Dariusz Jarząbek Application of advanced optical microscopy ....................................... 89 Examples of application of scanning electron microscopy (SEM) ...... 96 X-ray microtomography (micro-CT) application in visualization

of the fibre distribution and crack detection ................................... 98

Chapter Three .......................................................................................... 107 Applications of Fibre Cement Boards By Krzysztof Schabowicz and Tomasz Gorzelańczyk

Introduction ........................................................................................ 107 Example applications of fibre cement boards .................................... 107 Conclusions ....................................................................................... 121

References ............................................................................................... 123

INTRODUCTION Fibre cement board (FCB) is a versatile green building material, strong and durable. It serves as a substitute for natural wood and wood based products such as plywood or oriented strand boards (OSB). The properties of FCB as a construction material make it preferable for use as a ventilated façade cladding for both newly built and renovated buildings, interior wall coverings, balcony balustrade panels, base course and chimney cladding, and enclosure soffit lining. FCB can be applied to unfinished, painted, or simply impregnated surfaces [1-3].

Fibre cement components have been used in construction for over 100 years, mainly as roofing covers in the form of corrugated plates or non-pressurized tubes. They were invented by a Czech engineer, Ludwik Hatschek (1856-1914) [4]. In 1900, he developed and patented a technology for manufacturing light, tough, durable, and non-flammable asbestos cement sheeting that he called “Eternit.”

Fibre cement composite–compared to the components of concrete–shows improved toughness, ductility, flexural capacity, and crack resistance. A major advantage of the fibre reinforcement is the behaviour of the composite after cracking has started, as the fibres bridge the matrix crack (matrix-bulk material, in which the fibres are dispersed). Then, the stress is transferred to the high-resistance system of fibres, capable of withstanding the load. Post-cracking toughness allows the use of FCBs in construction. Moreover, the fibres can reduce the unwanted free plastic shrinkage within the structure, decrease the thermal conductivity, and improve the acoustic insulation and fire resistance.

For many years asbestos has been regarded as the most suitable material for reinforcing FCBs. White asbestos, a silicate mineral / Mg3(Si2O5)(OH)4 / naturally forms long and durable fibrous crystals with each visible fibre composed of millions of thin microscopic fibrils. It is found in many geological deposits throughout the world.

The fibres reinforce FCB components only when added in a specific quantity (approx. 10% wt.) and are uniformly dispersed throughout the cementitious matrix. A highly complex procedure is required to achieve this goal under efficient industrial conditions. Ludwig Hatschek solved the problem by inventing a machine with a rotating sieve and a vat containing a diluted fibre slurry, Portland cement, and mineral components. A thin

2

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CHAPTER ONE

FABRICATION OF FIBRE CEMENT BOARDS

KRZYSZTOF SCHABOWICZ AND TOMASZ GORZELAŃCZYK

FACULTY OF CIVIL ENGINEERING, WROCŁAW UNIVERSITY OF TECHNOLOGY

Introduction A modern process of FCB fabrication consists in laying thin paper-like films on top of each other until a desired sheet thickness is obtained [13, 14]. The process distributes the reinforcing fibres in planar uniformity, taking the best advantage of the reinforcing fibres to increase the in-plane strength of the sheet. Thus, the strength of sheets made using this process is approximately 50% greater than the sheets formed to full thickness in a single action using a filter press or the extruding processes. In a process detailed below, a thin film formed from a diluted fibre slurry is usually 0.25-0.4 mm thick and each FCB comprises a stack of these films. Thus, the final sheet consists of approx. 20-30 or more thin films. A large number of layers partially suppresses the imperfection of the considered method: the films formed on a sieve are not uniform in composition but due to sedimentation they have a fibre-rich side and a fibre-poor side. Additionally, 2.5-3 mm long fibres bridge the sieve holes, slightly blocking the feed of other particles and forming a fibre-rich layer. The portions formed last can be relatively fibre-poor. On this account, an advanced fibre orientation and distribution devices have been developed and introduced into the actual chain of FCB fabrication.

Fig. 1-1 shows a flowchart of a sample fibre cement board production process. The particular sub-processes named in the flowchart are detailed below.

Chapter One

8

Fig. 1-1. Flowchart of sample fibre cement board production process.

Figure 1-2 shows a sample flowchart of the technological process of fabrication of cellulose fibre cement boards, including seven zones corresponding to the specific production stages [12]. Fig. 1-3 shows a detailed diagram of zones no. 1 and no. 2 in order to outline their complexity. The moisture content of the board varies at each stage and is determined using methods described in the next chapter.

Preparing raw materials

Batching mix components

Mixing until homogenous pulp is obtained

Forming boards in special forming machine(Hatschek machine or flow-on machine)

Natural maturing in climatic chambers and in air for 7-14 days(maximally 28 days)

Taking boards off stacks and carrying

Transferring

Pressing to enhance properties

Wet cutting and stacking

Finishing – dustless cutting with water jet

PREP

ARAT

ION

ZO

NE

WA

TER

AND

WAS

TE R

ECO

VERY

SYS

TEM

Fig. 1-2. Flocement board

The fabr1), where ceuniform dispin specific phomogenousof cellulose autoclave camounts of clays, silica contain less

The mixmachine. Thboards with stage involvsuitable for board) is apcement boarcuring tunneboards can bas quickly aso they shou

Fabr

owchart of tecds.

rication of ceellulose fibrespersion is proproportions ars plastic compfibre cement

cured. Low (Portland cemfume, groundPortland cem

xture describhe Hatscheka fixed thick

ves the pressin the type ofpplied. Warmrds directly afel (zone 4) wbe taken off thas possible sinuld not be allo

rication of Fibre

chnological pro

llulose FCB ss are mixed woduced. Bulk cre added to thpound is obtai: low-tempera(air) cured foment combined limestone, o

ment and morebed above is

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f board fabricm (due to cem

fter pressing where they remhe stack and pnce the boardsowed to cool a

e Cement Board

ocess of fabric

starts in the pwith water in a

components (che batched wained. There arature cured anormulations ued with fine-gor fly ash. Aupozzolanic co

s transferredmachine is umm. The next

d boards (zoncated (exterioment hydrationor forming armain for abou

placed on a pals are still quiteand dry too mu

ds

cation of cellu

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to a boardused (zone 2)t (optional) pr

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9

ulose fibre

one (zone er) until a additives) ed until a categories erature or ain larger s such as mulations

nd fillers. forming

to form roduction

sing force cladding

lose fibre to a pre-

Next, the st be done damp, and ickly.

Chapter One

10

Fig. 1-3. Diagram of zones no. 1 and no. 2.

The boards placed on the pallets are left to mature and are cured in steady thermal-moisture conditions, e.g., in special airtight tarpaulin tents (zone 5) for about 14 days. After that time, the boards obtain the proper bending strength, and some moisture is removed naturally. After the maturation period, the boards are transferred to a final drying oven (zone 6) where they are subjected to three-stage drying at 180°C, 160°C, and

Fabrication of Fibre Cement Boards 11

120°C, respectively at stage 1, 2, and 3. Then, the boards are cooled naturally for about 20-30 minutes depending on their thickness. This is a critical stage of the fabrication process. Boards with excessive moisture content are not fit for further treatment, such as impregnation or painting. At the last fabrication stage, the boards are trimmed, and, if necessary, their surface is ground at the edges (zone 7).

Primary raw materials

Table 1-1 shows the typical primary raw materials used in the fabrication of naturally maturing fibre cement boards. Table 1-1. Typical primary raw materials used in fabrication of fibre cement boards.

Standard ratio

type of raw material approximate composition

Cement ~ 60% Cellulose (dry) ~ 8% PVA ~ 2% Kaolin or lime ~ 30% Total ~ 100% Additives & admixtures Hyperplasticizer ~ 0.1 l/t *) Didecyldimethylammonium chloride (DDAC) or bromide (DDAB)

~ 0.1 l/t *)

Perlite ~ 1 kg/t *) Mica ~ 1 kg/t *) Microsphere ~ 1 kg/t *) Antifoaming agent ~ 0.26 l/t*) *) l/t or kg/t = litres or kilograms per ton of finished product

Properties of PVA fibres

PVA (polyvinyl alcohol) fibres are a major component in the fabrication of naturally maturing cement fibre boards. The basic specifications of PVA fibres, based on the data for Kuralon (manufactured by Kuraray America Inc.) [40], are shown below. Table 1-2 shows the basic specifications of PVA fibres compared to other commercially available fibres.

Chapter One

12

Main advantages of Kuralon fibres: ▪ non-toxic, ▪ long-term presence on the market, ▪ established manufacturing process, ▪ high quality.

Table 1-2. Specifications of PVA fibres compared to other commercially available fibres [40].

Parameter type of fibre

Kuralon PET Nylon PAN PP Aramid Carbon tenacity (cN/dtex) 11-14 6-8 5 2-4 6-8 22 13-23

Young’s modulus 250-300 80-

145 40-80 30-70

30-110

400-700

1190-2370

alkali resistance X X X X

adhesion to cement X X X X X

weather resistance X

= good, = normal, X = bad

Figure 1-4 shows micrographs of the cross-sections of fibre cement boards reinforced with different fibres.

a)

b)

c)

Fig. 1-4. Micdifferent fibre

Fabr

crographs of ces [40]: a) Kura

rication of Fibre

cross-sections oalon fibres; b) p

e Cement Board

of fibre cementpolypropylene fi

ds

t boards reinfofibres; c) ARG f

13

orced with fibres.

14

Figure 1strength of f

Fig. 1-5. Relaboards [40].

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17

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24

Fig. 1-17. Ha

The sheefollowing prin the vat, wporous film moves the fis pressed toWhen the reto form a shthe roller anfilms in confilms togeth

Typical particles arethese particlwhereas thefibrous matestructure of

The effimaterial depachieved bydiameter witnetwork of particles. Th

atschek machine

ets are formedrocedure [13]water from th

of fibres andfilm onto the fo the felt. Thequired numbheet of a requind laid out flntact with eac

her and form asieve mesh si

e significantlyles can freely fibres are reterials within ththe fibre layericiency withpends on the

y a special procthout affectinfine fibres ca

his forms an i

Chapter

e diagram.

d in the Hatsch. When the cl

he slurry runsd cement onfelt. The exce

he felt transferber of films isired thicknesslat to form ach other unde continuous soizes are approy smaller (appy pass throughtained on thehe film on thers formed. which the f

e fineness ofcessing, i.e., b

ng their lengthapable of trapinitial filter la

r One

hek machine lean sieve is pthrough the

the surface oess water is rers the film onwrapped aro

, the stack ofboard. The d

er pressure isolid material.x. 0.4 mm, wrox. 50 µm inh the sieve ousieve. Thus, e

e surface of th

filter layer ref the cellulosby crushing thh. High qualitypping at leastayer on the su

in accordancepulled under tsieve to depo

of the sieve. Temoved whennto the formin

ound the formfilms is remodraining of susufficient to

whereas the non diameter). Tut of the formentrapment ofhe sieve depen

etains the nose kraft pulphe fibres to redy kraft pulp cathe larger no

urface of the s

e with the the slurry osit a soft The sieve the sieve ng roller. ing roller

oved from uccessive bind the

on-fibrous Therefore, med layer, f the non-nds on the

on-fibrous . This is duce their an form a

on-fibrous sieve and