Ultrasonic Speed Wave: Cure Type Influence on Wood-Cement CompositeCompression Strength
A.L. Beraldo, UNICAMP, Campinas, SP, Brasil
ABSTRACT Wood-cement composites are very interesting for construction purposes, mainly for rural buildings. Composites characteristics depend strongly of wood specie, wood/cement ratio, age, cement type, etc. However, composite compression strength tests show only the effect of the cement paste hardening. Non-destructive evaluating tests were utilized to evaluate the characteristics of several materials like metal, concrete, wood, etc. Physico-chemical characteristics of vegetal biomass disturb kinetic reaction of the cement paste in composite fabrication. Sometimes this reaction is delayed or eventually absents. Therefore samples can present defects (voids, cracks) mainly if the raw material is very inhibitory to the cement setting. Non-destructive evaluating tests, as ultrasonic speed wave propagation, can be utilized to survey changes in the wood-cement composite structure, provoked by the age or cement/wood ratio modification Washed particles wood (Erisma uncinatum) and a high initial strength cement (Brazilian type- CP V ARI) was utilized. Three replications of cylindrical samples for each treatment (cement/wood/water- 1/.375/.75) were carefully realized with cement paste. Ultrasonic speed waves across the samples were evaluated by means of an Ultrasonic Tester BPV. Speed of ultrasonic waves increased very quickly in the first initial aging period, mainly in the first hours, according to an exponential law, and then this value remained almost constant. Composite cure type influenced the speed of ultrasonic wave. The faster ultrasonic waves correspond to higher compression strength of the samples.
Publication Source: NDTISS '99 - International Symposium on NDT Contribution to the Infrastructure Safety Systems, Nov 1999 in Tores Brazil.
Publisher: Center of Tecnology, Federal University of Santa Maria (UFSM) - [Homepage]
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