Performance of Cardboard Carton Forms
PERFORMANCE OF CARDBOARD CARTON FORMS
Abstract:
Cardboard carton forms (void boxes) are commonly used to form the void space between the bottom of grade beams and slabs over expansive soils. However, other than laboratory compression tests and 100% humidity tests, there is little documentation for the actual performance of these boxes in place. This paper summarizes field tests done in an attempt to simulate actual conditions to answer the following questions:
• Do the boxes deteriorate at an acceptable rate?
• Does the wax coating or impregnation and a polyethylene vapor barrier affect deterioration?
• Will the boxes fail under heave conditions? Are trapezoidal boxes appropriate and do they perform in an acceptable manner?
• Which type of boxes are appropriate in each situation?
• What are some of the construction considerations necessary to insure proper function of the boxes?
Two configurations of boxes were used: Vertical Cell and Diagonal Type
II. Initial Test 1 procedure:
It was initially decided to pour a test slab over 4 sets of void boxes. Each box was 4 ft x 4ft x 8 in deep. Concrete was poured on top and all around each box to simulate actual conditions. Four 1 ft x 1 ft steel forms were placed on top of each box for the purpose of loading each box at different intervals to determine if they had deteriorated. All boxes for the first test were vertical cell. Each box was placed with different conditions:
• Void box with no poly anywhere
• Void box with poly wrapped all around
• Void box with poly on top only
• Void box with poly on bottom only Test set up with boxes and loading pads Placing concrete over boxes.
The procedure was to pour the concrete and test the capacity of the boxes once a week to determine the rate of deterioration.
Description of results:
• Week 1:
Each box was loaded with 200 psf and no deflection was observed
• Week 2:
Each box was loaded with 400 psf with no deflection
Abstract:
Cardboard carton forms (void boxes) are commonly used to form the void space between the bottom of grade beams and slabs over expansive soils. However, other than laboratory compression tests and 100% humidity tests, there is little documentation for the actual performance of these boxes in place. This paper summarizes field tests done in an attempt to simulate actual conditions to answer the following questions:
• Do the boxes deteriorate at an acceptable rate?
• Does the wax coating or impregnation and a polyethylene vapor barrier affect deterioration?
• Will the boxes fail under heave conditions? Are trapezoidal boxes appropriate and do they perform in an acceptable manner?
• Which type of boxes are appropriate in each situation?
• What are some of the construction considerations necessary to insure proper function of the boxes?
Two configurations of boxes were used: Vertical Cell and Diagonal Type
II. Initial Test 1 procedure:
It was initially decided to pour a test slab over 4 sets of void boxes. Each box was 4 ft x 4ft x 8 in deep. Concrete was poured on top and all around each box to simulate actual conditions. Four 1 ft x 1 ft steel forms were placed on top of each box for the purpose of loading each box at different intervals to determine if they had deteriorated. All boxes for the first test were vertical cell. Each box was placed with different conditions:
• Void box with no poly anywhere
• Void box with poly wrapped all around
• Void box with poly on top only
• Void box with poly on bottom only Test set up with boxes and loading pads Placing concrete over boxes.
The procedure was to pour the concrete and test the capacity of the boxes once a week to determine the rate of deterioration.
Description of results:
• Week 1:
Each box was loaded with 200 psf and no deflection was observed
• Week 2:
Each box was loaded with 400 psf with no deflection