STRENGTH AND MICROSTRUCTURES OF HARDENED CEMENT PASTES CURED BY AUTOCLAVING
THE KINDS OF CALCIUM SILICATE HYDRATES FORMED DURING AUTOCLAVING ARE IDENTIFIED AND THEIR EFFECTS DETERMINED ON THE MECHANICAL STRENGTH OR OTHER PROPERTIES OF THE AUTOCLAVED TEST SPECIMENS. FROM THE RESULTS OF THESE TESTS, BINDING CAPACITIES OF SEVERAL HYDRATE COMPOUNDS, AS WELL AS SUITABLE CONDITIONS FOR AUTOCLAVE CURING OF CEMENTS, ARE DISCUSSED. THREE CEMENTS, ORDINARY PORTLAND CEMENT /OPC/, PORTLAND BLAST-FURNACE SLAG CEMENT /PBC/ AND SPECIALLY PREPARED CEMENT /SMC/ WERE USED IN THIS STUDY. OPC AND PBC WERE OF PLANT MANUFACTURE. THE CONTENT OF BLAST-FURNACE SLAG IN PBC WAS 45 PERCENT BY WEIGHT. SMC WAS PREPARED BY MIXING 60 PERCENT OPC AND 40 PERCENT SILICEOUS ROCK POWDER BY WEIGHT. THE PROPERTIES OF EACH CEMENT ARE INDICATED IN TABLES. CEMENT PASTES WERE MADE AT WATER-CEMENT RATIO OF 0.30, MIXED FOR 3 MIN, AND MOLDED INTO 4X4X16-CM PRISMS. AFTER 1 DAY MOIST CURING AT ROOM TEMPERATURE /20C, 98 PERCENT RH/, THE PRISMS WERE REMOVED FROM THE MOLDS AND IMMEDIATELY PLACED IN AN AUTOCLAVE. FOUR CURING TEMPERATURES AND VAPOR PRESSURES WERE USED IN FIVE AUTOCLAVE CURING PERIODS. THE TIME NEEDED FOR TEMPERATURE RISE IN THE AUTOCLAVE AND THE TIME NEEDED FOR COOLING IT DOWN TO ROOM TEMPERATURE WERE ALWAYS KEPT CONSTANT /ABOUT 2.5 HR/. THREE PRISMS WERE PREPARED FOR EXAMINATION AT EACH CURING CONDITION. SPECIMENS FOR CHEMICAL ANALYSIS WERE PREPARED BY GRINDING THE HARDENED PRISMS FINELY AND DRYING TO CONSTANT WEIGHT AT 105-110 C. IT WAS DETERMINED THAT THE COMPRESSIVE STRENGTH OF HARDENED PASTE CURED BY AUTOCLAVING DEPENDS ON TEMPERATURE, PRESSURE AND DURATION OF CURING. NO RELATIONSHIP IS RECOGNIZED BETWEEN FLEXURAL AND COMPRESSIVE STRENGTHS IN THE HARDENED PRISMS OF OPC AND PBC, BUT THERE IS A FAILRY LINEAR RELATIONSHIP BETWEEN THEM IN THE HARDENED PRISMS OF SMC. THE AMOUNTS OF IGNITION LOSS AND FREE CA/OH/2 IN CURED PRISMS OF OPC AND PBC SHOW A TENDENCY TO DECREASE WITH RISE OF CURING TEMPERATURE AND PRESSURE. ACCORDING TO X-RAY IDENTIFICATION, THE HYDRATION PRODUCTS ARE MAINLY CALCIUM SILICATE HYDRATES AND FREE CA/OH/2. SMC IS CONSIDERED TO BE THE CEMENT MOST SUITED FOR AUTOCLAVE CURING.
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Supplemental Notes:
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Corporate Authors:
Highway Research Board (HRB)
Washington, DC -
Authors:
- Akaiwa, S
- Sudoh, G
- Publication Date: 1966
Media Info
- Features: Photos; References; Tables;
- Pagination: p. 36-47
- Monograph Title: Symposium on structure of Portland cement paste and concrete
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Serial:
- Highway Research Board Special Report
- Issue Number: 90
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Ash content; Autoclave curing; Binders; Blast furnaces; Calcium compounds; Cement; Chemical analysis; Compressive strength; Concrete curing; Concrete hardening; Hardness; Hydrates; Microstructure; Pastes; Portland cement; Pressure; Silicates; Slag cement; Specimens; Strength of materials; Temperature; Time; X ray analysis
- Uncontrolled Terms: Capacity
- Old TRIS Terms: Autoclaving; Binding
- Subject Areas: Highways; Materials;
Filing Info
- Accession Number: 00212451
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Dec 22 2001 12:00AM