Swimming Pool Design & Build

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Swimming Pools

Fourth edition

Philip H Perkins

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This edition published in 2000 by E & FN Spon 11 New Fetter Lane, London EC4P 4EE

Simultaneously published in the USA and Canada by Routledge 29 West 35th Street, New York, NY 10001

This edition published in the Taylor & Francis e-Library, 2003. E & FN Spon is an imprint of the Taylor & Francis Group First edition 1971

Second edition 1978

All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers.

The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made.

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data

A catalog record for this book has been requested ISBN 0-203-47788-X Master e-book ISBN

ISBN 0-203-78612-2 (Adobe eReader Format) ISBN 0-419-23590-6 (Print Edition)

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Finishing the pool shell and associated structures 7.1 Cement-sand rendering to insitu concrete walls 7.2 Cement-sand rendering to sprayed concrete walls 7.3 Cement-sand rendering to concrete block walls 7.4 Cement-sand screeds on insitu concrete floors 7.5 Cement-sand screeds on sprayed concrete floors 7.6 Ceramic tiles and mosaic

7.7 Walkways and wet changing areas 7.8 Testing the completed tiling 7.9 Marbelite

7.10 Coatings and paints

7.11 Sheet linings to swimming pools 7.12 Glass-fibre polyester resin linings 7.13 Finishes to walls of pool halls The roofs of swimming pool halls 7.14 General considerations 7.15 Pressurised roof voids 7.16 The warm-deck roof Further reading

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8 Water circulation and water treatment Water circulation

8.1 Flow-through pools

8.2 Pools where the pool water is in continuous circulation 8.3 Ducts for pipework

Water treatment

8.4 Layout of treatment plant 8.5 Filtration and filters

8.6 Chemical dosing of the pool water 8.7 The disinfection of pool water 8.8 Chlorination

8.9 Ozone 8.10 Bromine 8.11 Chlorine dioxide

8.12 Metallic ions (silver and copper) 8.13 Ultra-violet radiation

8.14 The base-exchange process for softening pool water 8.15 Sulphates in swimming pool water

Preface

Since the third edition of this book was published in 1988 there have been no startling changes in the materials used for the construction of swimming pools. A similar comment can be made about the design of reinforced concrete swimming pool shells.

The number of swimming pools has continued to increase both in the public and private sectors. This is particularly so with private club leisure centres which offer a wide range of activities.

There has been significant developments in the field of National Specifications and Code of Practice relating to construction due to the intensive work on the preparation of Euro Standards and Codes and the issue of Directives from the EEC. The latter set out minimum quality standards for a wide range of constructional materials, and establish the responsibility of suppliers and designers.

Of particular importance are The Construction (Design and Management) Regulations 1994 which became completely effective in December 1995. These Regulations make people assess risks and take precautions rather than waiting to deal with problems when they occur. They target the health and safety of those who build, maintain, install and demolish buildings and plant.

The Construction Products Regulations came into force at the end of 1991 to implement the Construction Products Directive. The potential scope of the Regulations is very wide indeed as they are applicable to all types of product which are intended for permanent incorporation in buildings and civil engineering works. The Regulations provide for the application of the European Community regulatory mark—the CE mark—to construction products. The Building Research Establishment Information Paper IP. 11/93 gives information on Ecolabelling of building materials and building products.

The British Standards Institution emphasise that the Kite Mark will continue to ensure that the level of quality is above the minimum legal requirements.

Health and Safety Regulations have been extended and tightened up and there is increasing awareness of the need for a more enlightened and professional approach to treatment of swimming pool water. The Committee which produced the publications for the Department of the Environment on the purification of swimming pool water is no longer in existence. It has virtually been replaced by the independent Pool Water Treatment Advisory Group.

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It is important to observe recognised safety precautions when using certain materials, and also all types of plant and equipment.

Concrete itself is not a hazardous material; however, Portland cement when mixed with water is highly alkaline (it has a pH of about 13.5) and is considered a caustic alkali. It can cause burns to the skin, particularly to people who are vulnerable to dermatitis. A safety warning is included as an Appendix in all British Standards for Portland cement. It recommends that precautions be taken to prevent dry cement entering the eyes, nose or mouth, and prevent skin contact with wet cement.

Polymer resins are now widely used in construction and there are hazards associated with the use of some of these compounds. Users should obtain information from the manufacturers and be aware of the requirements of the publications of the Health and Safety Executive relating to the use of substances hazardous to health.

The corrosion of steel reinforcement continues to be the number one cause of deterioration in reinforced concrete structures. Research Focus, No. 37, May 1999, states that: ‘Corrosion of reinforcing steel in concrete structures…is estimated to be costing the UK £550 million a year. Many of these structures continue to require maintenance or replacement…’

It is therefore surprising that the protection of rebars by properly formulated and applied epoxy resin coatings (see BS 7293 and ASTM Specification A775) is still only used on a comparatively small scale in the UK.

The author acknowledges with gratitude the encouragement, and many useful comments, he has received from his wife. He also records the help he has been given by numerous people, organisations and firms, and in particular, David Butler of the Sports Council, Andrew Alphick of the Pool Water Treatment Advisory Group, Ralph Riley of the Institute of Baths and Recreation Management, Geoffrey Roberts and Jim Gordon of Buckingham Swimming Pools Ltd.

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Chapter 1 The planning and layout of

swimming pools

GENERAL CONSIDERATIONS

1.1 Introduction

In the United Kingdom, the construction of the shell of a swimming pool (without ancillary buildings such as plant house, changing rooms etc.) is unlikely to require a Building Permit under the Building Regulations, but planning permission may be required. It is therefore advisable for any one wishing to build a swimming pool to consult their Local Authority, and also the water supply company as there may be special requirements, such as metering of the supply, restriction on the amount of water used etc.

While there are regulations relating to swimming pools open to the public, the legal control over the purity of water in pools for private houses, clubs and hotels is minimal. Recommendations for the treatment and quality of swimming pools water have been issued by the Pool Water Treatment Advisory Group (PWTAG), namely the Pool Water Treatment and Quality Standards. The PWTAG is an independent body supported by all the organisations involved in the operation of swimming pools.

In the United States, the position is different; for example in California regulations are in force which apply to all swimming pools except private pools maintained by an individual for use by his family and friends. The regulations specifically apply to pools belonging to hotels, clubs, schools and health establishments. Important aspects of design, layout, operation and maintenance are detailed and clear directions given. Requirements for the chemical and bacteriological quality of the water are included.

1.2 Basic requirements for all swimming pools

The recommendations given below are intended to apply to all swimming pools constructed of what may be termed ‘long-life’ materials such as concrete. 1. The pool shell (floor and walls) must be structurally sound.

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partially full, and if constructed below ground level, against infiltration of ground water when the pool is empty or partly empty.

3. The internal surface of the floor and walls must be finished with a smooth, reasonably impervious, easily cleaned, attractive material. The water must be maintained at a proper standard of purity and clarity.

4. A walkway of adequate width (minimum about 1.5 m), with a non-slip, easily cleaned and durable surface should be provided around the pool.

5. A safety step (or ledge) should be provided on all the walls of pools used by young children and non-swimmers. This safety step should be located not more than 900 mm (0.9 m) below top water level (Figure 1.1).

6. A diving board should not be provided unless the dimensions of the diving area and the water depth comply with the recommendations of the Amateur Swimming Association (ASA). For pools used for international diving competitions, the regulations of the Federation Internationale de Natation Amateur (FINA) should be followed.

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1.3 Pools for private houses, clubs, hotels and schools

1.3.1 Open-air pools: location

With pools in this category, there is generally a limited choice of location as they usually have to be built on the same plot as the main building. An exception is school pools as these may form part of sports ground facilities which are likely to be some distance from the school.

For open-air pools for private houses, and hotels, the following points should receive consideration.

1. A position should be selected which receives as much sun as possible, particularly in the afternoon.

2. The vicinity of large trees or potentially large trees should be avoided. Tree roots can cause damage to foundations, and to drains and other pipelines. Leaves can cause discolouration of the pool water and staining of the pool finish which is difficult to remove.

3. It is advantageous to utilise a natural wind-break, such as a thick hedge, garden wall, or part of the main building, and if it does not exist, to provide one as part of the landscaping.

4. The position of existing drainage, water supply, electricity and gas supply lines is important.

5. Depending on the method of construction of the pool (see Chapters 4 and 5), access for materials and plant required for the construction can be critical. 6. A small building (or room in the main building) will be needed for plant and

equipment and storage of cleaning materials and the chemicals used for water treatment.

7. It is desirable for the distance from the changing accommodation to the pool to be as short as practical bearing in mind the points mentioned above. 8. For private houses and hotels, landscaping of the area in which the pool is to

be located should be given careful thought and professional advice is usually worthwhile.

9. People often find it difficult to envisage from a two-dimensional sketch what the completed three-dimensional project will look like. The cost of a simple model and/or an isometric drawing could be justified.

Figures 1.2 and 1.3 illustrate alternative positions for a private pool.

1.3.2 The shape and dimensions of swimming pools

The shape and dimensions of a swimming pool are mutually interdependent. The primary use of the pool will be a major factor in determining both shape and dimensions.

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If the primary use is for training and swimming, then a rectangular shape is normally chosen. The length should be a simple fraction of 100 m, and the width a number of swimming lanes which are usually to be 2.0 m wide (ASA for 25 m pools).

The materials used in the construction of the pool shell will also influence its shape. Pools constructed in insitu reinforced concrete can be of any shape, but the cost of a free-formed pool would be very high due to the cost of the formwork, compared with a pool constructed in sprayed concrete (shotcrete). But this cost differential is influenced by the size of the pool, it being greater for smaller pools than for larger ones. The smaller domestic and hotel pools, constructed in sprayed reinforced concrete can be any shape, with little difference in cost between rectangular and free-formed.

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As these pools are likely to be used by children, non-swimmers and weak swimmers, the provision of a safety step around the pool at a depth not exceeding 900 mm (0.9 m) below top water level is strongly recommended. This is a standard feature of hotel pools in Switzerland (Figure 1.1).

1.3.3 Requirements for swimming

Even the smallest pool should be large enough for a swimmer to take several strokes; the minimum size would be about 6.00 m long by about 4.00 m wide with a minimum water depth of 1.00 m. However, a water depth of 1.00 m is not sufficient from a safety point of view for even a very flat dive. For general comfort, there should be an allowance of about 4.5 m2_{for each person who}

wants to swim.

1.3.4 Requirements for diving

The depth of water and the dimensions of the diving area for competitive diving are covered in the UK by the requirements of the ASA. For international events these matters are covered by the world governing body, the Federation Internationale de Natation Amateur (FINA). There are minor differences between these two sets of regulations but both provide adequate safety for diving in properly designed pools. The relevant publications of both organisations should be consulted and followed by the designers of any swimming pool which is intended to include a diving board. The designer should check and comply with the latest recommendations.

It is emphasised that the dimensions given are essential for safe diving from a position not more than 1.00 m above the water level in the pool.

A natural question is ‘What about diving from the sides of the pool?’. The only form of dive recommended into shallow water from the pool sides is what is known as a flat racing dive, which can only be safely executed by experienced swimmers; even then the minimum depth of water is 1.50 m, which must be

Table 1.1 Examples of rectangular swimming pools for private houses, hotels, clubs and

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maintained forward for a distance of 7.6 m and the water level in the pool should not be more than 0.38 m below the pool edge. These recommendations are given by the courtesy of the Institute of Baths and Recreation Management.

Diving should not be permitted nor attempted into pools which do not meet the above recommendations. Should an accident occur to a person diving into a pool from a diving board which does not meet authoritative safety recommendations, the pool owner/manager may be faced with a claim that would be difficult to contest.

1.4 Covered pools for private houses, hotels, clubs and schools

There are obviously many advantages in having a covered swimming pool instead of an open-air one. A covered pool can be used in comfort 365 days a year compared with the ‘season’ for an open-air pool of about 150 days. The conditions under which the pool has to operate are much less onerous; problems arising from freeze-thaw do not arise, staining of the walls and floor is much reduced, and discolouration of the water from leaves and air-borne dirt will be eliminated.

See Figures 1.5–1.6 for views of private house pools, and Figures 1.7–1.10 for views of hotel, club, and school pools.

A major problem with covered pools is the occurrence of condensation on the walls, windows and ceiling, and, depending on the method of construction, within the roof space.

The environment in the hall of a heated indoor swimming pool can be considered as particularly hostile to many building materials; the air temperature is relatively high—probably about 28 °C to 30 °C, and the relative humidity is also high, say, 70–75%. The surfaces in contact with the air in the pool hall will generally have a lower temperature than the temperature of the air in the hall; if the air is saturated

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Figure 1.6 Indoor private house pool. Courtesy, Buckingham Swimming Pools Ltd. Figure 1.5 Pool with Roman end and steps and fully automatic cover. Courtesy,

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Figure 1.8 Open-air pool at private club leisure centre. Courtesy, Buckingham Swimming

Pools Ltd.

Figure 1.7 Indoor hotel deck-level pool with spa pool. Courtesy, Buckingham Swimming

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Figure 1.9 Indoor, 25 m school pool. Courtesy, Buckingham Swimming Pools Ltd.

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with water vapour, condensation will occur on the contact surfaces. The temperature at which condensation occurs is known as the dew point.

The design and detailing of the roof requires special attention and this is discussed briefly in Chapter 7.

1.5 Teaching/learner pools

This section deals with general principles relating to layout and dimensions of teaching pools irrespective of whether they belong to a school or form part of a large swimming pool complex (leisure centre) run by a local authority.

The first principle is that the pool must be absolutely safe for non-swimmers. The pools are usually rectangular on plan with an almost level bottom. The water depth generally varies from 0.80 m to 1.00 m. A useful size is 12.00 m by about 7.0 m.

There are often shallow steps into the pool extending the full length of the short side.

There are different opinions as to whether the walkway around the pool should be lower than the deck to enable the teacher to carry out his duties without having to bend down, or whether the pool shell should be elevated similar to the hydrotherapy pool shown in Figure 1.15 and briefly described in Section 1.9.

In the UK, it is customary for the teaching pool to be quite separate from the main swimming pool so that the two different types of use do not interfere with each other. If the teaching pool is in a separate enclosed part of the main building, it is usual for the temperature of the water and the air in the pool hall to be a few degrees above that in the main part of the building.

1.6 Public swimming pools

1.6.1 Introduction

In the UK and most countries in the temperate zone, all new large swimming pools which are publicly owned are covered to enable them to be used throughout the year.

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There are a number of large open-air pools in the UK which are owned by local authorities, but these were built many years ago, generally before the Second World War. These are only in operation for four or five months in the year, usually from May to September. A few of these are heated. They are rectangular on plan and some contain sea water which contributes to a high rate of general deterioration.

In Europe, mainly in Switzerland and Germany, in spas, there are large open-air heated pools, some with wave-making machines.

Figures 1.11–1.13 are examples of pools in public leisure centres.

1.6.2 Location

It is not possible to lay down detailed rules for the location of public swimming pools, but the following are matters which should receive careful consideration:

1. provision of adequate public transport; 2. provision for adequate car parking;

3. provision of public sewers (foul and surface water), water supply, electricity, gas and telephone;

4. adequate access for emergency services, fire brigade and ambulance;

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Figure 1.12 View of pool in Rushcliffe Leisure Centre. Courtesy, British Cement Association.

Photographer, T.Jones.

Figure 1.13 View of pool in Swansea Leisure Centre with wave machine in operation.

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5. sub-soil conditions including water table levels, presence of aggressive chemicals and presence of contaminated ground. This is of particular importance in view of the alleged shortage in the UK of ‘good building land’, which in some cases exerts pressure to build on land-fill sites. The Environmental Protection Act 1990 should be studied. Requirement C2 of Schedule 1 of the Building Regulations 1991 states that ‘precautions shall be taken to avoid danger to health and safety caused by substances found on or in the ground covered by the building…’ Approved Document C, 1992 edition, sets out detailed requirements for dealing with containments. Reference can also be made to Section 4.2, and the list of Further Reading at the end of this chapter.

1.6.3 Types, shapes and dimensions

When the first edition of this book was published in 1971, the standard shape of public swimming pools in the UK was rectangular or L-shaped. Some large pools had two shallow ends. In L-shaped pools, the long leg can be used for swimming and the short leg for diving.

However, with the advent of the leisure centre, the shape, size and use of pools have changed considerably. Figures 1.11–1.13 show examples of public swimming pools in leisure centres. In these centres, it is usual for the main pool to be free-formed and incorporate a sloping ‘beach’ and the installation of a wave-making machine which is switched on for relatively short periods several times a day.

It is emphasised that for competitive swimming, diving and aquatic sports, the requirements of the ASA (for national events) and FINA (for international events) must be fully complied with. The requirements mentioned in this book are only a few of the very detailed requirements laid down by these two organisations. The following are examples of some of these requirements:

1. For competitive swimming (national events), the water depth in front of the starting blocks must not be less than 1.80 m and this must extend forward for a distance of 6.00 m.

2. Stairs and steps must be accommodated outside the pool dimensions, i.e. they must be recessed.

3. For water polo, the minimum depth of water over the whole playing area must not be less than 1.80 m; the playing area must not exceed 30 m× 20 m and must not be less than 20 m×8 m.

4. For life saving certificates, a water depth of 2.0 m is required and this must extend for a length of 6.00 m over the full width of the pool.

The provision of a diving pit as part of the main pool is deprecated as diving into a pool in which persons are swimming is unpleasant and can be dangerous. There are many advantages in having a separate diving pit which is used only for diving.

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By having a separate diving pit, swimming and diving events can be held simultaneously, and the same applies to training.

Pools intended for competitive swimming are normally 25 m or 50 m long with a width based on a number of swimming lanes, either 2.0 m for national events or 2.5 m for international events. Reference must always be made to the latest edition of the relevant regulations.

1.7 Floor gradients

1.7.1 The pool

The floor of the pool must be laid with a fall (slope) towards the outlet with such a gradient that the pool can be effectively emptied. However, the gradient should not be so steep that non-swimmers and learners can lose their balance and/or slip. It is generally considered that the depth of water at which boyancy is likely to affect a person’s balance is about 0.75 of the person’s height. The steeper the gradient, the sooner a person will reach the point of over-balance. As the point of over-balance varies with the height of the person, it is suggested that the maximum gradient for the floor of a pool used by children and non-swimmer/learners should be 1 in 40 (25 mm in 1.00 m).

For efficient emptying of the pool, hydraulic considerations require a gradient of about 1 in 80 (25 mm in 2.00 m). The gradient should be uniform between clearly marked locations and depth markers on all walls are essential. A further safety precaution is to provide non-slip tiles on the floor.

The above comments on gradient do not apply to the steep slope down to a diving pit as shown in Figure 1.4.

Water outlets in the floor at the deep end of the pool should be fitted with small aperture gratings. See Section 8.2.6.

1.7.2 Walkways and wet areas

In this context ‘wet areas’ include all those areas, such as changing areas, walkways around the pool, shower cubicals etc., which are made constantly wet by pool users and by cleaners. It is in these areas that injuries resulting from slipping are most likely to occur. There is a conflict between the need for a non-slip (or slip resistant) surface and the need for easy cleaning and efficient drainage (run-off). At the time of writing, there does not appear to be any formal and recognised gradients for floors in these areas.

There is also the problem of ponding. To avoid ponding, a gradient of about 1 in 40 (25 mm in 1.00 m) is normally required, but for safety a gradient of 1 in 60 (25 mm in 1.50 m) is probably needed. The frictional characteristics of the finished surface when in contact with the bare feet of pool users are relevant. It should be noted that the gradient suggested here is considerably less than for the floor of the pool in Section 1.7.1.

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1.8 The drainage of walkways and wet areas

Where walkways and wet areas form part of a covered pool complex, the drainage of these areas should not discharge into the water circulation system of the pool but should be connected to the main drainage system of the building.

1.8.1 General comments

In some cases the public sewers are designed on the ‘separate’ system in which surface water is carried in surface water sewers, but in other areas, the sewerage system is ‘combined’ and the foul and surface water is carried in the same sewer. It is important that an adequate number of inspection chambers/man-holes should be provided and drainage system laid to gradients which will provide a self-cleansing velocity.

With open-air pools, the surrounding paving should slope away from the pool. 1.9 Hydrotherapy pools

The advantages of carrying out special exercises under water have been known to the medical profession for many years; the weight of the body is reduced by the weight of water displaced and thus movements are made much easier with less muscular effort.

While spas in the UK have declined in popularity, this has not happened on the continent of Europe. There, special health resorts, with names starting with ‘Bad’ in Germany, Switzerland and Austria, continue to flourish and attract large numbers of visitors/patients. The spas are mainly situated in beautiful country and make a very pleasant location for a holiday.

Many of the special baths and swimming pools contain naturally heated highly mineralised water from springs, which in some places is slightly radio-active. There are often a number of pools which operate at different temperatures and possess therapeutic properties. Under-water massage by powerful jets located at different depths below the water surface is a common feature of many of these pools. The length of stay in the pool is strictly limited.

Figure 1.14 shows a pool at a spa in Switzerland.

Figure 1.15 shows a hydrotherapy pool at a school for pupils with severe learning difficulties. The pool is 10 m×5.00 m and the depth varies from 0.90 m to 1.50 m. It is a deck level pool and the water temperature is maintained at 32°C.

In the UK there are many therapeutic pools but these are mainly attached to hospitals, recuperation homes and similar institutions and are used for treatment prescribed by a physician. They seldom form part of a holiday resort.

Special features to be taken into account in the design of such pools include the following:

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Figure 1.14 Open-air pool with wave machine in operation Bad Vals, Graubunden,

Switzerland.

Figure 1.15 Hydrotherapy pool in school for pupils with severe learning difficulties. Courtesy,

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1. The floor should have a flat gradient of about 1 in 80 (25 mm in 2.00 m) which should be adequate for emptying.

2. The floor of the pool and all wet areas should be finished with non-slip ceramic tiles or ceramic mosaic.

3. If the pool is not deck-level, then glazed ceramic scum channels should be provided as these are more efficient in providing good water circulation than skimmer outlets.

4. The turn-over period (the time required to completely circulate all the water in the pool) should not exceed 3 hours; some pools operate on a 1½hour cycle. See Section 8.2.1.

5. The water temperature and the air temperature in the pool hall and changing areas should be maintained at a higher temperature than in normal swiming pools. A water temperature of 30–32°C and an air temperature of 33 °C is adopted in many pools.

6. All fittings should be corrosion resistant (austenitic stainless steel or phosphor-bronze).

7. As these pools will certainly be used by disabled persons, special arrangements should be included to enable such persons to enter and leave the pool easily; see also Section 1.11.

8. If the pool contains saline water, then a detailed chemical analysis should be obtained, including information on any variations in the concentration and type of dissolved salts. This is essential in order to decide whether special protective measures are needed for the pool shell, finishes and fittings.

1.10 Pools used for sub-aqua activities

Sub-aqua activities have become very popular in all parts of the world.

Training in the sea, lakes and rivers in the UK and other countries in the temperate zone is often difficult owing to low temperatures, low visibility, currents etc. Thus, there are many advantages in carrying out training in a swimming pool. The British Sub-Aqua Club (BSAC) requires that every beginner should receive basic training in a swimming pool.

The use of public swimming pools is not always permitted by Baths Managers owing to interference with public use of the pool and possible damage to the finish of the pool and walkways by the divers equipment. With reasonable care, the equipment used by the Club’s members should not cause damage if the finishes are high quality ceramic tiles or ceramic mosaic.

In any event, these finishes require maintenance and repair in the course of time. Small damaged areas can be repaired under-water which eliminates the need to lower the water level or empty the pool.

The BSAC have published a booklet giving detailed information on all aspects of aqualung diving—see Further Reading at the end of this chapter.

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The BASC Code of Conduct contains some 21 directions, including emphasis on the prohibition of dropping heavy equipment in the pool and anywhere in the pool premises.

As far as the pool itself is concerned, the requirements for sub-aqua activities are very modest. The minimum dimensions required for a group lesson are 3.60 m×5.00 m, with a minimum depth of water over this area of 1.50 m. These requirements can be increased with advantage, with special reference to water depth to 3.50 m and if possible 5.50 m.

Designers should contact the BSAC for their latest recommendations. Figure 1.16 shows sub-aqua training.

1.11 Facilities for the disabled

The absolute need to provide satisfactory arrangements for disabled persons to use public swimming pools is now recognised.

The specification and design of the necessary facilities require special study at the design stage as it can be difficult and costly to provide these facilities at a later date.

Work in this field is done by a number of organisations and reference should be

Figure 1.16 Aqualung training in public pool. Courtesy, British Sub-Aqua Club.

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made to BS 5810 1979 Code of Practice for Access for the Disabled to Buildings and to the publications of the Thistle Foundation.

1.12 Swimming pools with movable floors

The desirability of having separate pools for swimming, diving and teaching has been mentioned earlier in this chapter. Such separation entails additional capital investment and increased operating and maintenance costs; also, the teaching and diving facilities are only used from time to time.

This led to the development of hydraulically operated movable pool floors and separating walls. The depth of water can be reduced over part of the pool by raising a section of the floor thus forming a teaching/learner area.

This feature has proved more popular in Europe than in the UK where the number of public pools with movable floors is small and very few have been constructed in recent years. Figure 1.17 shows a movable floor in the raised position.

Figure 1.17 View of movable floor in public pool. Courtesy, Buckingham Swimming Pools

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1.13 Wave-making machines

The provision of equipment which generates artificial waves in swimming pools has become increasingly popular in recent years. When the first edition of this book was published in 1971, there was only one pool with wave-making equipment in operation in the UK, namely the large open-air Portobello pool at Edinburgh, which was installed in 1936.

During the past 25 years, wave-making equipment has been installed in many new leisure centre pools.

The wave-making machines are usually switched on at stated times for about 15–20 minutes.

There are several methods of creating artificial waves in swimming pools, the main methods being by (1) swing arm equipment, and (2) compressed air.

1.13.2 Swing arm equipment

The makers usually make a model of the pool so that they can assess all important hydraulic features, such as wave height, location of ‘breaking’ point, backwash, cross currents etc. The shape and sloping floor create the effect of a sloping beach with the waves breaking naturally. The shape also provides adequate area of shallow water for non-swimmers.

The wave-making equipment consists of two swing arms which operate together but not in complete unison. For example, one arm oscilates at 17.5 oscillations per minute and the other at 18.0 oscillations per minute. A specially designed screen is provided in front of the wings.

1.13.3 Compressed air equipment

There are a number of patented systems using compressed air to create artificial waves.

The creation of waves of the desired height and distance from crest to crest (wave-length) is not a simple matter and all relevant factors must be taken into account. This usually includes the making of a scale model.

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RECOMMENDED PROCEDURE FOR GETTING A POOL BUILT: CONTRACTS AND DEALING WITH DISPUTES

The recommendations which follow are intended mainly for private persons, club committees and owners of small hotels, although it is hoped that even large hotel groups and local authorities will find some of the points mentioned useful.

1.15 Contracts: how to proceed

It is not recommended that a swimming pool should be built on a do-it-yourself basis. Although there is a theoretical saving in capital cost the dividing line between success and failure is a very narrow one and the cost saving does not justify the risk.

The two procedures recommended are:

1. To engage a qualified professional person with proven experience in swimming pool design and construction who will take responsibility for the preparation of the design, drawings, specification and other contract documents, and obtaining all necessary permits. The consultant should recommend a list of, say, three contractors, send out the invitations to tender, recommend to the client the adjudication of the contract, certify the contractor’s accounts, and inspect the work at appropriate stages.

The consultant should be a Chartered Civil or Structural Engineer or Chartered Architect. In the case of large contracts for public swimming pools/ leisure centres, there will be several professional firms involved responsible for structural and civil design, heating and ventilating, electrical and mechanical and architectural, and quantity surveyors; the Architect is usually the head of the team.

2. To employ a consultant to advise on the selection of a suitable ‘package deal’ contractor. The names and addresses of swimming pool contractors can be obtained from the Swimming Pool and Allied Trades Association. The consultant, in discussion with the client (referred to as the Employer in the contract), should prepare a clear brief setting out the requirements (see Section 1.2). It is important that the contractors should submit a list of recently completed pools; these should be checked by site visits by the consultant, with the client.

The financial standing of the selected contractors should also be checked, and information obtained on the extent the contractors employ sub-contractors. A test for watertightness should be clearly described and included in the

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contract; see Appendix 2 at the end of this book for details of this test. The consultant’s brief should also include for periodic site inspections to help ensure that the contractor is carrying out the work in accordance with the contract.

1.15.1 Insurance-backed guarantees and warrantees

In recent years there have appeared on the market ‘insurance-backed guarantees’. These are offered by contractors/sub-contractors and material suppliers claiming that should the work prove defective, then the insurance company will provide the funds to have remedial work put in hand in the event of the contractor/supplier failing to do so. This suggests that the client will avoid the necessity of legal action to obtain redress. These ‘guarantees’, which are sometimes referred to as ‘warrantees’, are stated to be valid for periods of 10–20 years from the completion of the work.

A careful scrutiny of these guarantee/warrantees will usually reveal that they contain many anomalies and uncertainties. Such documents should be examined by a solicitor experienced in that particular field. A consultant would be unwise to recommend reliance on such a guarantee without first taking competent legal advice. 1.16 Dealing with disputes

The above may appear to be exaggerated, but experience suggests that caution and attention to detail is the best approach. Irrespective of which procedure is adopted, if things do go wrong, such as work unduly delayed, poor workmanship, the use of sub-standard materials, the failure of the pool to pass the leakage test etc., the building owner will find he is faced with the following limited choice:

1. He can accept the situation, which he would be most unwilling to do, or 2. He can instruct the contractor to put things right, in accordance with the terms

of the contract, and if he fails to do so he can follow the procedure laid down in the Conditions of Contract.

If the faults are serious, it is unlikely that even after completion of the remedial work, the finished job will be as satisfactory as if it had been done properly the first time.

One of the worst things that can happen is for the contractor to go into liquidation during the contract. The cost of employing another contractor to complete the project will be very high and the chance of obtaining financial compensation from the original contractor is extremely small. This is why it is important for the consultant not to feel obliged to recommend the acceptance of the lowest tender even though the tenders are from a list which he has drawn up. There can be many reasons why a contractor will submit an

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exceptionally low price. The client would be unwise to disregard his consultant’s advice in this matter.

The value of an experienced consultant, a properly drawn-up contract, and care in the selection of the contractor cannot be over emphasised.

1.16.1 General comments

The method of dealing with disputes which may arise during or after completion of a contract will depend mainly on whether the contract comes within the scope of the Housing, Grants, Construction and Regeneration Act 1996 which came into force on 1 May 1998 (known as the Construction Act 1996).

If the contract falls outside the scope of the Act then dealing with disputes would follow established procedure. However if the contract falls within the Act, entirely new procedures would have to be followed. Unfortunately, the wording of the Act in a number of important matters is lacking in clarity and at the time of writing this book, there is little reported experience in the operation of the Act.

The Act covers a very wide field, but the construction of a private swimming pool is likely to be outside the Act as it would most probably come under the exemption given to residential contracts.

The coming into force of the Construction Act has necessitated the revision of the Standard Forms of Building Contract and Sub-Contract, and the ICE Conditions of Contract.

The February 1999 issue of Construction Briefing issued by Merricks, Solicitors, London, states:

‘There has been a fundamental review of the legal system in this country over the last three years. A review carried out by Lord Woolf (“Access to Justice”) will culminate this year in major changes to come into effect on 26 April 1999 which will affect the speed and cost of legal proceedings.

The changes can be divided into three areas: (a) The restriction of legal aid;

(b) The expansion of contingency fee arrangements (‘No win, No fee’) for all proceedings except crime and family;

(c) Fundamental changes to court proceedings which should decrease costs and increase speed.

In the main, all Personal Injury work will be excluded from the new Legal Aid structure…’ Except in certain cases, ‘the case will be dealt by another route, e.g. a conditional fee arrangement, or via alternative dispute resolution.’ (This change in dealing with personal injury cases is likely to affect claims arising from accidents in swimming pools.)

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parties conduct themselves. There will be a series of preaction protocols dealing with various categories of litigation…There is a single objective to the new court rules—to enable the court to deal with the cases justly. Lord Woolf felt that the two evils of modern litigation were delay and disproportionate

costs…

Expert evidence will be more restricted and may not be adduced without leave of the court. Normally experts will not be allowed to give oral evidence but will provide a written report and answers to written questions put to them by the opposing party…’

There will be considerable control of costs. ‘Prior to taking interlocutory steps details of the costs must be given to the other side…’

All the above changes face the test of practical use and there may well be further changes in the light of experience.

1.16.2 Notes on procedure for contracts outside the construction Act 1996

As stated in Section 1.16.1 above, the situation may arise where the owner is faced with the choice of accepting an unsatisfactory swimming pool or taking legal action against the contractor, and/or the consultant. A Solicitor experienced in construction disputes would be able to advise the client on the appropriate procedure. The action to be taken is generally laid down in the General Conditions of Contract.

Action against the consultant could arise if it was considered by the employer’s Solicitor that he had been guilty of professional negligence.

The majority of construction contracts (prior to the 1996 Act), contain a provision for referring disputes as a last resort to arbitration. But subject to certain conditions, a party can apply to the Court to have the matter settled by Court action.

It is important to remember that Arbitration can be more expensive than Court action as the Arbitrator has to be paid (Arbitrators fees are high), and payment has to be made for the hire of the arbitration room. Costs usually ‘follow the event’ which means that the losing party may have to bear his own legal costs and those of the other party. Court judgments can be quite surprising. This, together with the high cost of litigation, is no doubt why so many disputes are settled out of Court (about 75–80%).

In the event of Arbitration or Court action, the employer would be advised by his Solicitor to engage a professional person to act as an Expert Witness. Some information of the duties of an Expert Witness are given in Appendix 4.

In Court proceedings, difficult technical considerations can arise if a defence of ‘Limitation’ is put forward. Such a defence is only likely to arise some years after the completion of the pool. A defence of limitation would

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involve the Limitation Act 1980 and the Latent Damage Act 1984, and the expert witness would be asked for his opinion on the following two issues: 1. When did significant damage first occur?

2. What was the earliest date on which the Plaintiff had both the knowledge required to bring an action for damages in respect of the relevant damage and the right to bring such action?

Such questions give rise to very complex technical considerations to which there is unlikely to be a clear-cut technical answer.

Due to the enormous cost of High Court actions and the very considerable delay which occurs between the time of the issue of the Writ and the handing down of the judgment, proposals have been made in recent years to find alternative methods of settling disputes. This is generally known as ‘Alternative Dispute Resolution (ADR)’.

While the majority of cases in the Official Referee’s court and in arbitration settle before trial, few do so early enough to avoid the substantial costs incurred in the preparations leading to trial.

The essence of ADR is to create a framework in which the parties involved in a dispute can reach a solution for themselves. This usually requires the assistance of a neutral third party.

There are a number of ADR techniques which include: Conciliation;

Mediation; Mini-trial;

Expert fact finding and adjudication.

The success of ADR depends entirely on the willingness of all parties to resolve their dispute in a mutually satisfactory way, and this requires considerable give and take. Some references on ADR are given under Further Reading at the end of this chapter.

1.16.3 Notes on procedure under the construction Act 1996

The comments which follow are intended to supplement those made in Section 1.16.1.

The Act gives parties to a construction contract the right to refer a dispute arising under the contract to adjudication in accordance with a clearly defined procedure. The procedure is intended to provide a fast-track method of resolving disputes. A party to a construction contract has a right, but not an obligation, to refer a dispute for adjudication under the procedure laid down in the Act.

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The Adjudicator must then be appointed within seven days of the issue of a notice by the party wishing for adjudication. The Adjudicator must reach a decision on the dispute within 28 days of referral, unless both parties agree to an extension of time. With the consent of the referring party, the Adjudicator may extend the 28–day period by up to 14 days.

The decisions of the Adjudicator are binding until the dispute is finally determined by legal proceedings or by arbitration or by agreement between the parties. The orders of the Adjudicator must be complied with and they are binding until the dispute is finally determined.

The Act contains numerous new concepts and conditions and anyone intending to have work carried out by contract after 1 May 1998 should seek legal advice on whether the contract will come within the scope of the Act.

Reference can usefully be made to the publication Construction Briefings, issued by Merricks, Solicitors, Chelmsford and London, and Notes of a

Seminar on the Construction Act, given by Lawrence Graham, Solicitors,

London.

Further reading

General

British Sub-Aqua Club. Pools for Sub-aqua Use.

Cottam, G. Adjudication under the Scheme for Construction Contracts. Thomas Telford, London, 1998.

Department of the Environment. Building Regulations (Amendment) Regulations

1998, S.I. 2561—Revision to Part M, Access and Facilities for Disabled

People.

Institute of Baths and Recreation Management. Practical Leisure Centre

Management, Vol. 2.

Institute of Baths and Recreation Management. Diving in Swimming Pools.

International Board for Aquatic, Sports and Recreation Facilities. International Standards

Swimming Pools: Part B, Construction, Finish and Equipment, 1977.

Sports Council. Safety in Swimming Pools, 1998.

State of California, Department of Public Health. Laws and Regulations Relating to

Swimming Pools, excerpts from the California Health and Safety Code and the

California Administrative Code.

Swimming Pools and Allied Trades Association. Swimming Pool Guide, 1995.

Construction Act 1996

Merricks, Solicitors. Construction Briefing—The Housing Grants, Construction and

Regeneration Act 1996, Merricks, Chelmsford and London, May 1998.

Lawrence Graham, Solicitors. Four papers at a seminar on The Housing Grants,

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Health and safety and environmental law

Fink, S. Health and Safety Law for the Construction Industry, Thomas Telford, London, 1997.

Health and Safety Executive. Slips and Trips HS (G) 155.

Stubbs, A. Environmental Law in the Construction Industry, Thomas Telford, London, 1998.

Alternative dispute resolution

McKenna and Company, Solicitors. Law Letter, Autumn/Winter 1989, McKenna, London, pp. 14–15.

McKenna and Company, Solicitors. Alternative dispute resolution, Litigation Update, May

1995, McKenna, London, pp. 6–8.

Hollands, D.E. Alternative dispute resolution, Journal CIArb, February 1992, pp. 57–9. Grove, J.B. The role of arbitration in an ADR environment, Journal CIArb, November 1997,

pp. 244–5.

The expert witness

Newman, P. Professional liability of expert witnesses, Journal CIArb, August 1993, pp. 173–81.

Lord Taylor. The Lund lecture—The expert witness, Journal CIArb, May 1995, pp. 113–17. The Times, Law Report: 6 Oct. 1999: Court of Appeal Judgement 27 July 1999; Stevens v

Gullis (Pile third party).

EEC construction legislation

Department of the Environment. Construction products directive, Euronews, Construction , Special supplement, September 1991.

Kay, T. and Wyatt, B. European Standards for protection and repair, J Concrete, September 1997, pp. 11–17.

Taylor Joynson Garrett, Solicitors. The Construction (Design and Management) Regulations, 1994, Construction Review, Issue No. 1, 1995.

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Chapter 2 Basic characteristics of the

materials used in the

construction of swimming

pools

The objective of this chapter is to provide information on the principal materials used in the construction of swimming pools, including those used in external works described in Chapter 6. The materials are:

Portland cements;

Aggregates from natural sources for concrete and mortar; Admixtures;

Additions;

Water for mixing the concrete/mortar; Steel reinforcement including stainless steel; Spacers;

Non-ferrous metals; Curing compounds;

Polymers and reactive resins; Joint fillers and joint sealants; Ceramic tiles;

Notes on bimetallic corrosion;

Notes on British Standards and Euro Codes.

The information given in this chapter is intended to be of a general nature and specifiers and users should always refer to the latest edition of the relevant National Standard.

Work is continuing at the British Standards Institution on the revision of existing Standards and Codes and the production of new Euro Standards and Codes. It is therefore essential that anyone wishing to incorporate into a contract requirements for compliance with British Standards should ensure that they are still valid and have not been replaced by a Euro Standard. Reference can also be made to BRE Digest

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2.2 Portland cements

It is made by burning at high temperature a mixture of chalk and clay in a rotary kiln. The clinker is ground and gypsum (calcium sulphate) is added to control the set. British Standard BS 12 limits the amount of sulphur (expressed as SO

3) to

3.5%. The fact that Portland cement contains sulphate is important when investigating the possibility of sulphate attack on concrete or mortar which is discussed in Chapter 3.

The addition of water to the cement results in a complex reaction accompanied by the evolution of heat.

Revised British Standards for cements were published in 1996. The new designations for Portland cements likely to be used for the construction of swimming pools and external works are as follows:

Portland cement class 42.5 to BS 12 1996 (CEM 1); Portland cement class 52.5 to BS 12 1996;

Portland cement class 42.5R to BS 12 1996;

Sulphate-resisting Portland cement class 42.5 to BS 4027 1996; Portland Masonry cement to BS 5224 1995, ENV 413.1. The letter R denotes high early strength.

The revisions were mainly concerned with methods of test and terminology and were intended to agree with the European Standard for cement, ENV 197–1. Minor changes in composition were also introduced.

In the early 1990s a complete and major revision was carried out to BS 5328

Concrete, and this was issued in four parts:

Part 1 Guide to Specifying Concrete 1995;

Part 2 Methods for Specifying Concrete Mixes 1991;

Part 3 Specification for the Procedures to be Used in

Producingand Transporting Concrete 1990;

Part 4 Specification for the Procedures to be Used in Sampling,

Testing and Assessing Compliance of Concrete 1990.

In 1993, BSI issued a Published Document PD 6534 1993 Guide to the Use in the

UK of DD ENV 206 1992.

The principal characteristics of Portland cement are:

1. A very fine powder, particle size 1–50 microns (1 micron equals 0.0001 mm). 2. The paste (cement and water) is highly alkaline, having a pH of about 13.5. The high alkalinity is relevant to the protection of steel reinforcement, and also to the occurrence of alkali-aggregate reaction. The interaction

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betweenalkalis in the cement and certain types of silicious aggregates is discussed in Section 3.9.

3. The setting time (initial and final) is in the range of 45 minutes to 10 hours. 4. The compounds which are principally responsible for the cementing action of

the cement paste are mainly the calcium silicates (the C2S and the C3S). 5. It is the hydration products of the cement which, other things being equal,

determine the strength of the concrete/mortar. The hydration products are very complex chemical compounds. The principal compounds are calcium silicate gel, calcium hydroxide (about 20%) and tricalcium aluminate hydrate. The calcium hydroxide (Ca(OH)₂) is liberated by the hydrolysis of the calcium silicates. The various hydration products hydrate at different rates, but the hydration is rapid to start with and then slows down.

6. The three major factors which influence the rate of gain of strength are the chemical composition, the fineness, and the temperature of the hydrating mix. With modern cements, the increase in strength after the first 28 days is likely to be very small and can generally be ignored.

7. The amount of water in the mix (usually referred to as the water/cement ratio, w/c) is a vital factor in determining the strength, permeability, absorption and durability of the concrete/mortar. Generally, other factors being equal, the higher the water/cement ratio the lower the strength and the higher the permeability and absorption. This is why it is often necessary to use a plasticizer in the mix when high quality concrete is required.

8. Due to its high alkalinity, Portland cement is very vulnerable to attack by acids. The reaction between the cement and the acid takes place immediately the two are in contact. See Section 3.5.2.1.

2.2.1 Sulphate-resisting Portland cement

Sulphate-resisting Portland cement (SRPC) should be specified as Low Alkali Sulphate-resisting, class 42.5 complying with BS 4027 1996.

The cement is similar in its strength and other physical properties to Ordinary Portland cement (OPC), but the tricalcium aluminate content (the C3A) is limited in the relevant British Standard (BS 4027) to a maximum of 3%. It is the C3A which is attacked by solutions of sulphates of various bases. This can have important consequences as the reaction products are expansive in character and is discussed in Section 3.5.2.2.

The low alkali content, not exceeding 0.6% equivalent sodium oxide, is useful in minimising the risk of alkali-silica reaction; this is discussed in Section 3.9.

2.2.2 Blended cements

Blended cements consisting of mixtures of Portland cement and pulverised fuel ash (pfa) and Portland cement and ground granulated blast furnace slag (ggbs) are used in concrete for special purposes such as reduction of heat of hydration and to

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improve sulphate resistance. Generally, these additions slow down the rate of gain of strength of the concrete.

2.2.3 Portland masonry cement

This should be specified as Portland masonry cement class MC 12.5 complying with BS 5224 1995. It contains an air-entraining agent which increases resistance to freeze-thaw conditions. The inclusion of additives to impart workability and improve water retention are particularly useful. It is used for mortar for brickwork and blockwork and for external rendering.

2.3 Aggregates from natural sources for concrete and mortar

The relevant British Standard for concreting aggregates, which is still valid at the time of writing, is BS 882, and covers gravel, crushed rock and sand.

The British Standards for fine aggregate (sand) for mortars and external rendering are BS 1199 and BS 1200 1976/1996, and these cover sand for mortar for plain and reinforced brickwork, blockwork and masonry.

The Standards should be referred to for their detailed requirements, which include grading limits, flakiness, shell content, and limits on clay, dust and chlorides. Regarding durability, BS 882, Appendix B makes the point that ‘No simple tests for durability and resistance to frost or wear of concrete can be applied; hence, experience of the performance made with the type of aggregate in question and a knowledge of their source are the only reliable means of assessment.’

With sea-dredged aggregates, special attention should be paid to the shell and salt (mainly sodium chloride) contents.

In the UK, aggregates from some sources in Scotland and the north of England possess high shrinkage characteristics. When there is any doubt about an aggregate, reference should be made to BS 812 Testing Aggregates; this is in 23 parts published between 1985 to 1995.

Part 120 details test methods for determining drying shrinkage of mortar prisms made with the suspect aggregates and recommendations are given for the interpretation of the results.

There are different opinions among experienced engineers on the effect of absorption of aggregates on the permeability of concrete used for water-retaining structures. The relevant Code, BS 8007 1987 Code of Practice for the Design of

Concrete Structures for Retaining Aqueous Liquids, places a limit of 3% on the

absorption of aggregates. However, published information on properly conducted tests which would justify this restriction are conspicuous by their absence.

The Standards for sands for mortar are BS 1199 and 1200: Building Sands from

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2.4 Admixtures

An admixture can be defined as a chemical compound that is added in comparatively small quantities to concrete, mortar, or grout at the time of batching or mixing, to produce some desired characteristic in the mix and/or in the mature concrete, mortar or grout.

While the use of admixtures in the UK has increased significantly in recent years, this country lags behind continental Europe, the USA and other developed countries.

The main types of admixtures in general use are: Water-reducers, plasticizers/workability aids; Superplasticizers;

Accelerators; Set retarders;

Air-entraining admixtures.

The general use of admixtures is covered by various Codes and by BS 5328 Parts 1 and 3 and by ENV 206 (draft European Standard). The ENV puts an upper limit on the use of admixtures in a mix at 5% by mass of the cement and a lower limit of 0.2%. The ENV also requires that when the dosage of admixtures in liquid form exceeds 3 litres/m3_{of concrete, this shall be taken}

into account when calculating the water/cement ratio of the mix.

The British Standards are performance specifications. The USA Standard for admixtures for concrete is ASTM C494–86. It should be noted that BS 8110 Structural Use of Concrete refers to pigments as an admixture, but PD 6534 1993 Guide to the Use in the UK of ENV 206 1992 Concrete, clause 4.5 includes pigments under the heading of Additions and this practice has been followed in this book.

2.4.2 Water-reducing admixtures/workability aids/plasticizers

For concrete, these admixtures are covered by BS 5075 Part 1. This type of admixture is a compound which increases the workability of a concrete mix with a constant w/c ratio, or permits the w/c ratio to be reduced without reducing the workability of the concrete. It should not increase the air content of the mix.

The Standard also covers ‘accelerating water/reducing’ admixtures and ‘retarding water-reducing’ admixtures.

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2.4.3 Superplasticizing admixtures

These admixtures are covered by BS 5075 Part 3, and by the draft European Standard ENV934–2.

This type of admixture is a compound which when added to a concrete mix imparts very high workability to the mix, or allows a large decrease in the w/c ratio while maintaining a given workability.

The very high workability obtained (150–200 mm) slump ensures that the concrete is virtually self-compacting. However, the super workability only lasts for a limited period, usually in the range of 2–4 hours. In the context of this book, this type of admixture can be very useful for placing concrete in positions where compaction is very difficult, e.g. in members containing congested reinforcement and repairs to honeycombed concrete.

The two main basic types of superplasticizers are sulphonated naphthalene-formaldehyde condensates, and sulphonted melamine-naphthalene-formaldehyde condensates.

2.4.4 Accelerators

These are covered by BS 5075 Part 1 and draft European Standard ENV 934–2. There is no British Standard for accelerators for mortar and grout.

This type of admixture increases the rate of reaction between the cement and water in a concrete mix, and thus accelerates the setting and rate of gain of strength of the concrete. Some accelerators contain chlorides as an active ingredient and the British Standard requires that the chloride content must be stated by the manufacturer. Standards for concrete now strictly limit the chloride ion content of concrete which contains ferrous metals, see BS 5328 Parts 2 and 3.

2.4.5 Set retorders

This type of admixture is covered by BS 5075 Part 1. It is a compound that reduces the rate of reaction between the cement and water in a concrete/mortar, thus reduces the rate of setting of the concrete/mortar.

The relevant British Standard for set retarders for mortar is BS 4887 Part 2; the draft European Standard is ENV 934–2. The British Standard covers building mortars and rendering, but not mortars for floor screeding. Suppliers of ready-mixed building mortars make extensive use of this type of admixture.

2.4.6 Air-entraining admixtures

This type of admixture is covered by BS 5075 Part 2. It is a compound which when added to a concrete mix incorporates air during the mixing; it should not significantly affect the setting of the concrete.

The draft European Standard is ENV 934–2. For mortars, the relevant British Standard is BS 4887 Part 1.

Swimming Pool Design & Build

Swimming Pools

Fourth edition

Philip H Perkins

Contents

Preface

Chapter 1

The planning and layout of

swimming pools

Chapter 2

Basic characteristics of the

materials used in the

construction of swimming

pools

Part 1

Guide to Specifying Concrete 1995;

Part 2

Methods for Specifying Concrete Mixes 1991;

Part 3

Specification for the Procedures to be Used in

Producingand Transporting Concrete 1990;

Part 4

Specification for the Procedures to be Used in Sampling,

Testing and Assessing Compliance of Concrete 1990.