X - HKU Libraries

4*4*2(November, 1983)4.4*2*1 Bifferences between British and Hong Kong concretesThe properties of Hong Kong concretes differfrom the properties given in BS 5400 s Part 4 forBritish concretes t probably because of the qualitiesof the local aggregate and the properties of the locallyavailable cement*Recommendations concerning suitable valuesfor use in Bong Kong are given later in this sectionfor various properties* Other concrete propertiesmentioned in BS 5400 s Part 4 way also have differentvalues in Hong Kbng t and the possibility should beborne in mind during design*The shape of the stress-strain curve givenin Figure 1 of BS 5400 s Part 4 is generally applicableto Hong Kong f but the slope of the initial tangentshould be adjusted to 5®0 x ^ftw/tfm to allow for thedifference in elastic modulus.4.4«2.2 Elastic modulusValues for the modulus of elasticity ofconcrete are significantly lower in Hong Kong than inBritain. The values used for design purposes diouldbe taken from Table 4*4®2 rather than selected fromthe values for the short term elastic modulus givenin Table 2 of BS 5400* The modulus of elasticityreferred to in Table 4*4»2 is the static modulusdescribed in BS 1881,4.4*2.3 StrengthConcrete gains strength at early ages morerapidly in Hong Kong than in Britain. After 28 days,the rate of gain of strength is lower in Hong Kongthan in Britain.Tables 3 and 19 of BS 5400 : Part 4 shouldaccordingly not be used in Hong Kong. Figure 4*4»1|giving (fn/f28) ft^e ^atio of strength at any time f n fto 28-day strength) against time, should be usedinstead*