A lightweight composite concrete cover is provided for subgrade trenches and vaults. The lightweight cover comprises at least one low density layer that has a low density filler material such as polyethylene terephthalate beads. The low density layer substantially reduces the overall weight of the cover, and the remaining layers provide sufficient structure for the cover to pass rigorous load and chemical exposure testing. In addition, a method of manufacturing a lightweight cover is provided that promotes the combination of different layers of the cover and the cross linking of polymer chains between layers of the cover. The lightweight cover has substantial weight savings and also meets rigorous testing standards such that a worker can manually remove the cover, transportation costs are realized, and worker safety is improved.

A lightweight composite concrete cover is provided for subgrade trenches and vaults. The lightweight cover comprises at least one low density layer that has a low density filler material such as polyethylene terephthalate beads. The low density layer substantially reduces the overall weight of the cover, and the remaining layers provide sufficient structure for the cover to pass rigorous load and chemical exposure testing. In addition, a method of manufacturing a lightweight cover is provided that promotes the combination of different layers of the cover and the cross linking of polymer chains between layers of the cover. The lightweight cover has substantial weight savings and also meets rigorous testing standards such that a worker can manually remove the cover, transportation costs are realized, and worker safety is improved.

A curing agent comprising methyl isobutyl ketone peroxide and at least one peroxide.

A curing agent comprising methyl isobutyl ketone peroxide and at least one peroxide.

A curing agent comprising methyl isobutyl ketone peroxide and at least one peroxide.

A method for producing a gypsum plasterboard comprising the steps of providing bundler dust obtained from gypsum plasterboard leftovers of a plasterboard trimming process by a trimming device, in particular by a bundler saw; and adding at least a part of the bundler dust to a gypsum slurry for producing the gypsum plasterboard.

A method for producing a gypsum plasterboard comprising the steps of providing bundler dust obtained from gypsum plasterboard leftovers of a plasterboard trimming process by a trimming device, in particular by a bundler saw; and adding at least a part of the bundler dust to a gypsum slurry for producing the gypsum plasterboard.

The present invention relates to an additive for hydraulically setting compositions comprising a colloidally disperse preparation comprising at least one salt of a polyvalent metal cation with at least one organic phosphonate and/or phosphate compound as anion and at least one polymeric dispersant comprising anionic and/or anionogenic groups and polyether side chains. The additive is especially suitable as slump retainer and for improving early strength.

The present invention relates to an additive for hydraulically setting compositions comprising a colloidally disperse preparation comprising at least one salt of a polyvalent metal cation with at least one organic phosphonate and/or phosphate compound as anion and at least one polymeric dispersant comprising anionic and/or anionogenic groups and polyether side chains. The additive is especially suitable as slump retainer and for improving early strength.

A method of making a cement composition, comprising grinding a cement clinker and a strength-enhancing agent, thereby producing a hydraulic cementitious powder, wherein the strength-enhancing agent is present in the hydraulic cementitious powder in an amount of from 0.001% to 0.09% based on dry weight of the hydraulic cementitious powder. The strength-enhancing agent is a compound represented by the following structural formula (I). The definitions of variables R.sup.1, R.sup.2, and R.sup.3 as well as R.sup.10, R.sup.20, and R.sup.30 are provided herein.