Cement admixtures market and usage trends

C e m e n t Admixtures Market and U s a g e Trends Prof. P C Hewlett, Director, The British Board of Agremen~ PO Box 195, Bucknalls Lane, Garston, Watford, Herts., WD2 7NG

Abstract Unlike s o m e other chemical product groups used in building and construction c e m e n t admixtures are not well k n o w n and until early 1970's were regarded by specifiers and users as having marginal benefit giving added value to a p r o d u c t - concrete - itself rather pedestrian and routin~ This paper outlines current market demands for mater~als and the changing trends in construction us~ That situation has and still is changing as perceptions about concrete change. There is a/so a need to s e e cost in terms o f added value and that has to relate to improved performances.

Introduction There have been excellent and recent updates on admixtures1~.4~ but there is little identity given to the underlying thrust that causes change in practices and materials, namely commercial benefit. It is fair to ask 'what stimulates change' in a traditional industry that revolves around routines and well tried methods and materials. Concern for the consequences of stagnation in attitudes was expressed by R J S Sutherland5~of Harris and Sutherland at the 'Durability and design life of buildings' Symposium held at the ICE in November 1984. The position with new materials and new technology today is particularly unsatisfactory. Most designers and almost all clients representatives are so afraid of future problems, extra costs and even litigation, that they shy away from anything which is not wholly covered by codes, standards, certificates or hallowed practice. To be fair to admixtures and their manufacturers, established of standard and their incorporation into codes (eg. BS 8110) have been achieved and so the status of, and confidence in these chemicals has increased, albeit well behind that of other industrialised countries. A general willingness for materials change is usually not sufficient to effect that change. Commercial well being and appropriate technology

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are also needed. Financial benefit is perhaps the greatest spur for change - admixtures are subject to all these demands. Apart from specialised problem situations admixture usage is related to unit volume concrete cost and that in turn is inextricably linked to cement costs. These have increased steadily over the last 15 years despite substantial attempts by the cement manufacturers to alter production techniques making them more energy efficient. Cement prices have increased by more than 300% since 1973 (fig. 1) and have stimulated attention to admixtures, particularly those admixtures that allow the user/specifier to make the best use of whatever cement content is required. July 1988 figures for bulk and bagged cement being approximately .£53 and .£56 per tonne respectively. The component cement cost per cu. metre of ready mixed concrete has increased from about 20% to over 40% of retail price. Such trends stimulate interest in admixtures. There is evidence of a shift away from direct short term gain to a longer term concern for making and placing durable concrete. Ordinary Portland cement may well change over the next 10 years with price stabilised, pre blended cements becoming routine. The use of fume, slag and pfa with con-

sequential changes in admixture use and forfnulation. However, for the immediate term we have to project forward from ongoing UK usage trends. Using the 6 month and annual statistical returns from the Cement Admixtures Association* based on admixture types, money values and cement tonnage treated, it is possible to identify usage trends, market value and so make tentative forward projections. Money value figures over the 5 year period 1980-1985 are given in fig 2 covering 11 admixture categories, namely 1. Accelerators and accelerating water reducing agents 2. Retarders, retarding water reducing agents, normal water reducing agents and pumping aids 3. Air entraining agents 4. Integral waterproofers 5. Superplasticisers 6. Mortar plasticisers and integral waterproofers 7. Curing membranes The basic admixture types (air entraining agents, retarders, water reducing agents and accelerators, still dominate in money value terms, but technically subtle changes in the chemical composition have been *Contacb Dr P Bosworth, Secretary, Cement AdmL~tures Association, 2A High Stree~ Hyth~ Southampton S04 6YPZ.

CONSTRUCTION & BUILDING MATERIALS Vol. 3 No. 2 JUNE 1989

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taking place (see below). Money value trends alone can mislead since they may result simply from price increases rather than changes in usage. A better indicator is cement tonnage treated with admixtures. That can be obtained knowing the unit dosage cost and dosage levels. Cement tonnage treated figures and total c e m e n t produced are given in fig 3. Admixture usage is a percentage of total c e m e n t produced is given in fig 4. Significant trends emerge

1. Annual UK c e m e n t production (fig 3) has remained almost constant at about 14 million tons per annum. That trend remained up to 1987 but 1989 shows a substantial increase to about ] 7 million tons. S o m e 10-15% of that figure being supplied from Scandinavia and mainland Europe.

2. From fig 2 and assuming modestly - an annual rate of £% (25% for the 5 year period) a) only 3 groups of admixture have shown growth in moneyv alue terms, namely, air entraining agents, superplasticisers and mortar plasticisers/waterproofers. b) all other categories that presently comprise the Cement Admixtures Association's statistical returns have shown a decrease. I.e. accelerators, accelerating water reducers, retarders, normal water reducers, retarding water reducers and pumping aids, integral waterproofers and curing membranes. This m a y a p p e a r s o m e w h a t anomalous even so several trends can be identified. (i) from fig 4 admixture usage has oscillated from 28% to 43% of all cement produced (1981 compared to 1983). In a static market this seems to represent a real

CONSTRUCTION & BUILDING MATERIALS VoL 3 No. 2 JUNE 1989

increase in admixture use although estimates for the year ended 1985 would show a decrease to approximately 35%, contrary to previous optimistic predictions<°). (ii) from fig 2 of the admixture groups, mortar admixtures rather than concrete admixtures have shown substantial money value increases, in particular plasticisers and integral waterproofers. (iii) air entraining agents and superplasticers have also increased but curing membranes and accelerating/accelerating water - reducing agents have declined. (iv) fig 4 shows that ready mix concrete production has remained fairly static at approximatley 20 million cu. metres peryear for the same period, although it peaked in 1983. A similar trend was relfected in admixtures but whether this increase resulted from greater use in ready mix concrete cannot

93

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CONSTRUCTION & BUILDING MATERIALS Vol. 3 No. 2 J U N E 1 9 8 9

Either cost of the dosage has increased or the dosage itself increased or both. 2. The opposite trend has occurred with accelerators and accelerating water reducing agents where cost values have decreased whilst cement treated values have increased. Either unit dosage costs have decreased and/or dosages themselves. The remaining four groups have consistent trends. Fig 6 shows quite clearly that the six main admixture groups divide into major and minor categories, the split being:

be deduced (7). Excluding curing m e m b r a n e sales the average added cost per cu. metre of concrete resulting from admixture use stands at £0.35 and has shown little increase since 1981 (£0.32/cu. metre)(°). If we take the analysis of admixture sales further, other detailed trends can be identified. A distinction should be m a d e between trends based upon sales value as against changes in cement tonnage treated. The latter being the more appropriate basis, in fig 5 the main admixture groups are compared with 1980 figures on the basis of equivalent cement tonnage treated and comparative sales values corrected for inflation (approx 25% added value). S o m e unexpected trends can be identified. 1. Whilst air entrainer use has increased in m o n e y value terms their real use has remained static.

Major admixture categories Retarders, water reducing agents, retarding water reducing and pumping aids Air entraining agents Mortar plasticising/integral waterproofers

Minor admixture categories Accelerators/water reducing agents Integral waterproofers (concrete) Superplasticisers The trends are woth noting 1. Retarders etc. have shown a steady decrease since 1980. 2. Air entrainers have shown little change but mortar plasticisers/ integral waterproofers have shown a steady increase. 3. The minor category admixtures show small variations, the significance of which is difficult to judge. It might be assumed that future trends will stem from the major admixture categories. However that is not proving to b e the case. The target should be to include admixtures in all concrete and mortars, in which case the UK market value is about £ 15 - 20 million. If one concentrates on ready mix concrete

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CONSTRUCTION & BUILDING MATERIALS VoL 3 No. 2 JUNE 1989

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only then an admixtures market value of approximately 7 million would seem representative. Present trends

Technical Generally speaking natural products are being replaced by synthesised materials and there is also a growing tendency towards the production of complex admixtures with two or more active constituents: these may have either dual function or increased effectiveness. a) Combined air entrainer/water reducing plasticisers (major) used in pavement quality concrete which will provide stipulated air content (approx. 6% v/v) whilst maintaining strength levels, these are belnds of 'Vinsol' type resins or synthetic surfactants of the alkyl aryl sulphonate type with normal plasticisers and superplasticisers.

These admixtures are not without problems and current development is aimed at formulating mutually compatible ingredients which will entrain stable air in concrete under vigorous handling conditions. Experience to date has shown such a dual requiremetn to result in erratic performance which is itself perhaps stemming from the basic incompatibility of air entrainment/air void stability and the competing action of dispersion. b) Economic superplasticisers (minor) consisting of blends of modified ligno sulphonate (MLS) and sulphonated naphthalene formaldehyde condensates (SNF). These are cheaper and more effective water reducers than some standard superplasticisers and give good workability retention in flowing concrete without excessive retardation of set.

Although the use of superplasticisers has not realised earlier hopes or expectations, developments have continued to improve their performance and cost effectiveness. However the noveltyof extreme workability concrete has stimulated interest in and use of high workability concretes generally. Attempts to upgrade lignosulphonates by removing all sugars and carbohydrates in a two stage fermentation process (followed in some cases by fractionation to increse the average molecular weight) have produced excellent plasticisers but air entrainment and retardation of cement hydration have limited their use as superplasticisers except in the MLS/SNF blends described above. With such blends, the distinction between normal plasticisers and superplasticisers is becoming somewhat blurred as they can be used as

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CONSTRUCTION & BUILDING MATERIALS Vol. 3 No. 2 JUNE 1989

solely on neutralised V~nsol resin; today, these are now in the minority. Many are blends of Vinsol resin with synthetic surfactant and others comFuture trends bine anionic surfactants with calcium Commercial Product development remains a or sodium ligno sulphonate or with somewhat ad hoc activity not always hydroxycarboxylic acid salts. The increase in use of cement following the market/statistics trend, i.e. development of superplasticisers replacement materials (PFA and that does not appear justified in GGBS) has certainly stimulated a usage terms. The reasons for this are search for air entrainers that perform obscure and probably reflect market effectively and reliably with blended opportunism more than reality. cements. Similarly, the necessity of However, product development is using poorly graded sands as agoften ahead of apparent market need gregate sources become scarcer, has and that is the basis of active market extended the use of air entrainment development. to applications other than frost It is likely that admixture develop- durability. ment will be part of an overall concrete development taking regard Mortar plasticisers and of cement changes, aIternative hy- waterproofers draulic binders and changing practices. In 1980 the majority of mortar plasticisers were air entrainers based Technical

both high or low dosage levels depending on the application.

range of complex organic acids which are typified by abietic acid (i). With the production of suitable synthetic detergents on a large scale, the use of anionic surfactants has become increasingly common in mortar plasticisers. These are generaIly the sodium salts of sulphonated or sulphated atkyl-aryl and alkyl compounds such as sodium p-dodecylbenzene sulphonate (ii) and sodium dodecylsulphate. Simpler compounds with shord carbon chain lengths such as sodium sulphosuccinamate N ~ CO. CH2.

on Vinsol resin, a natural product derived from wood resin. When neutralised with caustic soda the resin gives rise to soluble salts of a

Air entraining admixtures Seven years ago, the majority of concrete air entrainers were based

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CONSTRUCTION & BUILDING MATERIALS VoL 3 No. 2 JUNE 1989

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CH2. CO. SO3Na have also been found to entrain air efficient~9~. The synthetic air-entraining agents are often a blend of surfactants. They are veb, cost effective although bubble stability in mortars is not always as good as that conferred by Vinsol resin. C h a n g e s in u s e Air-entrainers were originally introduced to replace hydrated lime (Ca (OH)2) in "lime-gauged" mortars, the plasticising action of which gives better workability and water retention when laying bricks or blocks. By entraining up to 20% air, tiny air bubbles (size range 20 - 1,000 mickrometres) are introduced into the mortar to act as spherical particles with zero coefficient of friction. The replacement of hydrated lime by entrained air has probably become more wide spread in recent years due to the increasing popularity of readymixed mortar on large building sites. Not only is the entrainment of air cheaper than adding hydralime but the dispersing of a liquid admixture at the mixing plant is easier and the retention of workability better. For this purpose, the "spacing factor" of the bubbles is not as important as it is when producing frost-resistant concrete. The aim is to produce 15-20% air-entrainment and reduce the water sufficiently to off-set most of the strength loss caused by the air voids. However, air stability is important as loss of air during handling can reduce workability drastically. Recent developments involving retarded mortars have emphasised the need

98

for air-entralners which are compatible with the retarder and which can produce a stable bubble system when subjected to discharge from a ready-mix truck into a skip. Such mortars may be required to remain plastic for 48 hours prior to being used. The setting time of these mortars depends upon absorption of excess retarder into the surrounding brickwork. Variations of this type of admixture perhaps mirroring the concrete retarders/accelerators currently undergoing extensive trails in the USA may well appear over the next few years. Other suggested future developmerits are:1. Plasticisers and superplasticisers with more efficient action, tailormade for particular applications. A greater proliferation of dual or even tri-functional admixtures m a y well occur (eg accelerating/ air- entraining/superplasticisers for pre-casting durable elements). 2. More efficient non.chloride accelerators. The commercial avail. ability of more effective accelerators, such as calcium nitrite (which is also an inhibitor of steel corrosion) will lead to increasing use in pre-casting and cold weather concreting ~1°~. 3. Emphasis on calcium rather than so~'urn salts for use as admb~tures in reponse to problems with alkali-aggregate reaction. This is important w h e n high alkali cements cause total equivalent Na20 in concrete to approach the safe limit (currently 3 kg/M 3) with sensitive aggregates. 4. Increasing use of synthetic surfactents as air-entrainers, with the emphais on cheapness and stability of the entrained air. 5. Special admixtures to increase the cohesiveness of concrete of grout placed under water. These have evolved in response to offshore and other marine requirements (such as underwater pres. sure pointing of harbour walls). The chemical industry has developed a range of long chain polymers such as the cold water soluble cellulose ethers and high molecular weight polyethylene oxides which alone (or more commonly in conjuntion with other chemicals) modify the theology in such a w a y that

cohesion of the mix is increased and cement wash. out prevented 6. Investigation of admixtures with composite materials comprising OPC and alternative hydraulic binders eg, pfa, ggbs and fume.. Perhaps in concrete technology terms this will be the most significant change. However, it will require a different attitude to concrete by user and specifier alike. The technology is available and the underlying cost trends may well demand the use of other options over the next decade. Some trends straddle both com. mercial and technical requirements, for instance the developments of codes and standards. Admixtures in the last twelve years have made considerable progress in this area. A n excellent international review was given at C182 ~w. Generally, the influence of British, European and eventually inter. national standards on the development of admixtures and their usage will be very gradual With the wider introduciton of quality assurance in the construction industry .it can be anticipated that all materials, including admixtures, will be required to conform to relevant standards, or alternatively be covered by third party performance assessment Indeed the emergence of the CE mark m a y well ease the transfer of products from Europe into the UK and vice versa. However if this trend follows those for other construction products the UK is likely to be affected more by Europe than the other w a y round With the exclusion from the market of all non.com. plying admixtures it is to be hoped that significant improvements in quality and performance will be achieved However the market in admixtures is a limited one and m a y be better served by fewer manufacturers w h o can offer the product development and technical service base rather than a large number of small turn. over manufacturers unable to offer such supporL References 1. V S Ramachandran, R F Feldman and J J Beaudoin "Concrete Science" Chapters 4, 5 Heyden 1981. 2. V S Ramachandran "Concrete Admixtures Handbook" Noyes Publications 1984. 3. M R Nixon and N P Mailvaganam "Chemical Admixtures for Concrete" second edition E

CONSTRUCTION & BUILDING MATERIALS Vol. 3 No. 2 JUNE 1989

& E F Spon, 1986. 4. P C Hewlett "'Cement Admixtures: Uses and Applications" second edition. Longman Scientific and Technical, 1988. 5. R J M Sutherland Keynote Address "Durability and Design Life- the Breadth of the Subject", proceedings of the ICE/ Concrete Society/RIBA Symposium "Design Life of Buildings", 26-27th November 1984, pages 7 - 15. 6. N. Austin, Prive Communication 2nd October 1984 (Cormix Limited) 7. "Building Materials and Components" Section 12.3 Monthly Digest of Statistics Number 481 (January 1986), Central

Statistical Office 8. P C Hewlet~and M R Rixom "Admixtures An International Review(Part 1) ERMCO 83 General Session 6, British Readymix Concrete Association VII ERM£O Congress 22 - 26 May 1983. 9. Albright and Wilson Ltd "improvements in the Production of Aerated Cement-Based Building Materials" British Patent 1534532 1978. 10. British Patent 1, 122, 497: "Cement Compositions", 7 August 1968 to W R Grace. 11. T J "Hpier "Specifications and Standards for Concrete Admixtures - an International

CONSTRUCTION & BUILDING MATERIALS Vol. 3 No. 2 JUNE 1989

Review", proceedings of the Internatianal Congress on Admixtures, Concrete International 1980 London (The Construction Press Ltd, Lancaster). 12. British Standard BS 5075: Part 1:1982 "ConcreteAdmixtures, RetardingAdmixtures and Water-reducing Admixtures". Footnote This paper was presented at The Industrial Marketing Research Association, Chemicals Group Symposium, held in London last February.

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