Modern day curing revised july 2006

Curing CMUs

Heat of HydrationLow Pressure Steam Kiln

Autoclaving

Configuration and design of curing chambers

• Sample Layout – Individual Atmosphere Chambers with moving rack system

Configuration and design of curing chambers

• Sample layout – Single Atmosphere large room system

SUBJECTS TO BE COVERED

1). STEAM CONDITIONS

2). CURING CYCLE

3). KILN DESIGN

4). BOILER SELECTION

CONTROLLED CONDITIONS OF STEAM

1). Quantity

2). Quality

3). Velocity

Quantity - Have the required boiler capacity to produce enough steam to

complete the curing cycle.

Quality - Saturated steam is a quality steam, having the correct amount of heat

& moisture present.

Velocity - Correct piping to induce steam evenly into kilns for equal

distribution.

Rate of Temperature Rise of Block Should be About:

60 deg. F or 33.3 deg. C/ hr.

5.5deg.C /10 min.or 33.3deg.C/hr

EQUILIBRIUM TEMPERATURE WILL VARY

WITH:

1). Type of Block

2). Material

3). Kiln Size

4). Rate of Temperature Rise

5). Weather

6). Kiln Insulation

AFTER SHUTTING OFF STEAM, BLOCK SHOULD BE ALLOWED

TO SOAK 6 TO 8 HOURS.

The soaking period is as important as the steam time. The longer the units are allowed to soak the better will be the final results. As long as the air in the kiln is not disturbed, the humidity of the kiln increases as the temperature decreases, because the moisture content is relatively constant. An accelerated curing condition is maintained in the kiln during the entire time the temperature is falling to 70 degrees (21.11c). Therefore, the longer soaking period is extended, the greater the compressive strength of the block.

DETERMINATION OF BOILER LOAD

1). Individual kiln requirements

2). Number of kilns being operated simultaneously

3). Plant heating requirements

4). Miscellaneous loads

In conclusion it must be remembered that theproper curing of concrete masonry is a processing problem and not a heating problem. The proper installation of a efficient curing system is the job of a person thoroughly familiar with the thermodynamic properties of steam and air, and also familiar with boilers, preheating and water treatment.