An abrasive particle includes at most three surfaces and at least one edge which has a corner at at least one end. The abrasive particle may contain a ceramic material, particularly polycrystalline -Al.sub.2O.sub.3. Abrasive particles as a whole, methods for producing abrasive particles, moulds, abrasive articles, methods for producing abrasive articles, and methods for abrading a surface are also disclosed.

A mold assembly and method for molding two concrete blocks in face-to-face non-contacting relationship forms blocks having smooth front faces. The mold assembly includes a mold box having two mold cavities configured to form two blocks in face-to-face non-contacting relationship. A common partition plate separates the two mold cavities and opposite sides of the partition plate form the smooth front faces of the blocks. The two mold cavities are each configured to form a block having a raised front face with a beveled edge around its entire perimeter and a border around the entire perimeter of the beveled edge. The portions of the border at the top and the sides of the raised front face are curved and the portion of the border at the bottom of the raised front face is straight. A core bar is slidably inserted into the mold box beneath the bottom of the partition plate, and opposite sides of the core bar extend into and form the front bottom portions of the mold cavities.

The invention comprises a concrete form. The concrete form comprises a first mold for concrete and a second mold for concrete, the first and second molds being in thermal communication with each other. The concrete form also comprises thermal insulating material substantially surrounding the first and second molds but not between the first and second molds. A method of using the concrete form is also disclosed.

A retaining wall having a plurality of courses of retaining wall blocks including a first upper course and a second lower course. Each retaining wall block has opposed front and rear faces, opposed first and second side surfaces, and opposed and substantially parallel upper and lower surfaces, and at least one weight bearing pad extends from one of the upper and lower surfaces. The at least one weight bearing pad extends substantially from the rear face to the front face of the block. The weight bearing pads are the only areas of contact between the blocks in the first upper course and the blocks in the second lower course.

A pre-stressed concrete box culvert includes a three-sided culvert top section having a pre-stressed top slab, a first sidewall and a second sidewall. The first and the second sidewalls extend orthogonally from opposite ends of the pre-stressed top slab, and the first and the second sidewalls each include a free end that has at least one male or female connector. The pre-stressed concrete box culvert includes a three-sided culvert bottom section having a pre-stressed bottom slab and a third sidewall and a fourth sidewall. The third and the fourth sidewalls extend orthogonally from opposite ends of the pre-stressed bottom slab, and the third and the fourth sidewalls each include a free end that has at least one male or female connector to mate with the at least one corresponding male or female connector arranged at one of the respective free ends of the first and the second sidewalls.

A method and mold assembly for forming a dry cast concrete corner blocks having non-parallel front and rear faces and non-parallel end faces, with a hollow central core in the blocks. The corner blocks can be used to build a square or irregular corner in a retaining wall, and can be used to build columns or pillars in the wall, without having to cut the corner blocks. Fill material may be poured into aligned cores in the stacked corner blocks which form the wall corner or column, to stabilize the corner blocks.

A method and mold assembly for forming a dry cast concrete corner blocks having non-parallel front and rear faces and non-parallel end faces, with a hollow central core in the blocks. The corner blocks can be used to build a square or irregular corner in a retaining wall, and can be used to build columns or pillars in the wall, without having to cut the corner blocks. Fill material may be poured into aligned cores in the stacked corner blocks which form the wall corner or column, to stabilize the corner blocks.

A retaining wall having a plurality of courses of retaining wall blocks including a first upper course and a second lower course. Each retaining wall block has opposed front and rear faces, opposed first and second side surfaces, and opposed and substantially parallel upper and lower surfaces, and at least one weight bearing pad extends from one of the upper and lower surfaces. The at least one weight bearing pad extends substantially from the rear face to the front face of the block. The weight bearing pads are the only areas of contact between the blocks in the first upper course and the blocks in the second lower course.

A bonded abrasive article includes elongate shaped abrasive particles. The elongate shaped abrasive particles comprise an elongate shaped ceramic body having opposed first and second ends joined to each other by at least two longitudinal sidewalls. At least one of the at least two longitudinal sidewalls is concave along its length. At least one of the first and second ends is a fractured surface.

A bonded abrasive article includes elongate shaped abrasive particles. The elongate shaped abrasive particles comprise an elongate shaped ceramic body having opposed first and second ends joined to each other by at least two longitudinal sidewalls. At least one of the at least two longitudinal sidewalls is concave along its length. At least one of the first and second ends is a fractured surface.