Length Change Apparatus measures changes
in length of cast prisms due to autoclave curing,
alkali reactivity, and other causes not related to
applied load. Methods are applicable to testing
of hardened portland cement paste, mortar, concrete,
or evaluation of hydraulic hydrated lime for
HM-250 and HM-250D Length Comparators
are similar units for measuring length changes in
10in (254mm) specimens cast with special gage
studs in the ends to fit the bottom and top anvils of
the Comparator. Sensitive indicator with 0.0001in
(0.0025mm) divisions measures specimen length.
Recommended HM-250D has a quick-reading
0.5in (12.5mm) range LCD digital indicator with
in/mm switch, RS-232 port, and replaceable 200
hour battery. Economy HM-250 has a 0.4in range
mechanical dial indicator, which will convert to
time-saving digital version with purchase of a digital
indicator. Comparators include a heat treated, hardened
Invar Reference Bar for exactly zeroing the
dial indicator at regular intervals. Construction is a
sturdy upright support attached to a solid base. Test
specimens up to a 4x4x10in (102x102x254mm)
cross section, but 1x1x10in (25x25x254mm) prisms
are normal. Inquire for special adapter and shorter
Invar Reference Bar if 5in (127mm) long prism
samples are tested. Overall Comparator Dimensions:
11x11.5x17in (279x292x432mm), WxDxH.
HM-252 Cement Autoclave
(ASTM C 151,
AASHTO T 107, others) provides an accelerated
means of estimating delayed expansion of portland
cement caused by hydration of CaO and MgO. Test
bars are exposed to controlled steam pressure
and constant temperature. Unit is capable of pressures
in the 60—350psi (0.4—2.4mPa) range and
includes steam vessel, pressure regulator, pressure
gauge (0—600psi x 5psi), air vent valve, power
switches, a safety pop valve set at 350psi, MA-421F
thermometer, wrench, and package of five gaskets.
Replacement gaskets, and safety pop valves are
available as accessories. Autoclave chamber is
6-1/8in (156mm) IDx16in (407mm) H. Overall
Dimensions: 17x48x28in (432x1220x711mm),
WxDxH; 1,800 Watts/15.7 amps maximum power
demand on 115 VAC supplies. For use with 230V
service, order TR-3002 transformer.
HM-254 Test Bar Holder (order separately) holds
up to eight 1x1in (25x25mm) bars of 10in (254mm)
gage length. Bars are held vertically above water
level to expose all specimens to Autoclave steam.
Prism Molds, Gage Studs (ASTM C 490,
AASHTO M 210, others): Prism Molds are corrosion-
resistant steel (HM-258 is stainless) with
base plate, removable partitions and end plates,
designed to provide required length of 10in (254mm)
between ends of gage studs cast in ends of bars.
Dimensions from outside ends of studs (comparator
gage contact points) are 11-5/8in (296mm);
specimens are 11-1/4in (286mm) long. Select molds for specimen cross sections of 1x1in,
2x2in, or 3x3in. Molds for 5in (127mm) gage length
specimens available. Package of ten stainless steel
Gage Studs HM-268 are knurled and threaded,
1/4x13/16in (6.35x20.64mm) diameter x L.
HM-270 Mortar Bar Container (ASTM C 227), is
stainless steel with tight fitting cover to seal in water
vapor. Vertically supports up to 36 mortar bars in
container with lower end above water surface.
Box is 9x11x15.5in (229x279x394mm), LxWxH.