properties of high alumina cement grout

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26 EFFECT OF TEMPERATURE RISE ON. PROPERTIES OF HIGH ALUMINA. CEMENT GROUT. S.A. JEFFERIS. Queen Mary and Westfield College, University ...
26 EFFECT OFTEMPERATURERISE ON

PROPERTIES OF HIGH ALUMINA CEMENT GROUT S.A. JEFFERIS Queen Mary and Westfield Co11ege, University of London・ UK

R.J. MANGABHAI TH TechnoIogy Ltd, R&D Centre, Rickmansworth, UK

High alumina cement grouts of O-4 water/cement ratio were cast into moulds made from steel and pvc and of various dimenSions・ The

temperature rise of the grouts in the moulds was monitored. For moulds │ni亡ia11y at room temperature and without co○1ing peak temperatures of

over lOOOC were observed. For steel moulds irmersed in a water bath at 8OC a temperature rise of 23OC was observed. However′ for pvc moulds

similarly immersed in water the peak temperature was over 135OC demonstrating the substantial insulating properties offered by even a thin wall of pvc. The results of strength measurements on sa皿Ples cast in steel moulds

and iIIlnlerSed in water at 8OC showed the expected rapid strength development・ │n contrast uncooled samples showed considerab│e reduction

in strength.

These results show that for HAC grouts which necessarily have a high cement c○ntent as there is no dilution by aggregate the hYdration exothem can be verY SeVere・ Thus for test speci皿enS and also when

using mC grouts the exothem of the grout must be carefullY considered. 1n general, C∞ling wi11 be necessarY unless the section to

be grouted is very thin. Insulation provided by plastics etc. may be

sufficient to prevent satisfactory texperature contrOl. KeYWOrd睾: High alunina cement′ Temperature′ Peak temperature′ Moulds′

Strength, DTA"

High alunina cement grout has been used successfully on North Sea Oil

platfoms, tYPicallY for grouting the amular space between anchor piles and sleeves on struc亡ures・ This fom of structural connection has

been used since 1969 for situations where high earlY Strength is required (Ciment Special, 1980). However, there has been some concern about the temperature rise of the grout during hydration. This temperature rise maY be sufficient to cause loss of strength in addition to convers│On.

This paper reports亡he findings of a short s亡udY Of the temperature r│Se Of grout specimens when subjected亡O亡wo different extemal temperature regimes・ These regimes were: (i) grout moulds imersed in

Water imediatelY after filling′ Water maintained at 8Oc (ii) grout moulds left in free air′ r0Om temPerature l与-20OC.

2 Exper土面enta│

High alunina cement (RAC) Fondu compIYing to BS 91与obtained from

Lafarge special cement co Ltd (1989) was used in the investigation, The Chemical c○mposition and surface area∴are given in Table l.

Table l. Chemical c○mposition and surface area of mC.

Specific surface area ‥ 250 m2/kg

皿e grouts for the first series of tests were prepared in a coIcrete

SD4 high shear mixer. The procedure was as follows: 30 1itres of water Were POured into the mixer・75 kg of the cement were then added over a

Period of two minutes・ Mixing∴WaS C○ntinued for a further 3 minutes

making a total mixing time of 5 minutes. 冒he grout was then pumped from the mixer and poured into mou│ds.

軌ree types of mould were used′1与O m diameter by 30O m high steel moulds′ 100 m steel cube moulds and 125 m dianeter bY 460 m high pvc moulds with a wall thickness of the order of 5 m. After filling′ a

themocouple was inserted at the centre of each mould and the moulds either placed in water at 8。C or left in free air. The output from each

themocouple was logged using a coxputer controlled data logger∴at与

m│nute intervals for a period of 72 hours.

TYPe T thermocouples obtained from RS Components were used for these temperature measurements.

For strength measurements 100 m cubes (Without thermocouples) were CaSt in steel moulds and initially either imersed in water at 8Oc or left in free air. The cubes were demoulded at 24 hours and cured under Water at either 80C or r0Om temPerature as appropriate.

3∴Results and Discus8ion 3. 1 Peak te『Perature8

The teIやerature-time profiles for the grouts cured at 80C and at room

ヒemperature are shown in Figures la, b, 2a, b, and 3a, b. For all the

SamPles cured at room temperature there was an initial period of COOしing (the grout after mixing∴WaS alwaYS SignificantlY above r0Om

temperature) f01lowed by a plateau of relatively c○nstant亡emperature

extending to about 4 hours. This was followed bY a raPid temperature r│Se Peaking at about 5 hours and reaching 100OC for the 15O rm

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