Lightweight concrete

Details Lightweight concrete Lightweight concrete

2001-10-16

2003-09-09

Friedman, Carl D. (Department: 3635)

Compositions: coating or plastic

Coating or plastic compositions

Inorganic settable ingredient containing

Reexamination Certificate

active

06616752

ABSTRACT:

This application is a 371 national stage of PCT International Application No. PCT/CH00/00219 filed Apr. 14, 2000.
FIELD OF THE INVENTION
The invention relates to a flowable and settable casting compound, in particular lightweight concrete, with a binder, in particular cement, and at least one lightweight aggregate, to a prefabricated element, to a structural member that is cast in situ, and also to a process for producing structured surfaces in cast structural members and elements.
BACKGROUND OF THE INVENTION
Foam glass is offered on the market in plate form or as bulk material. For the purpose of producing plates of foam glass, new glass is mixed with a range of additives, is baked in moulds and thereby foamed, is then thoroughly cooled and cut into plates. The foam-glass lumps of the bulk material are fragments of a foam-glass layer which is produced by baking, at up to about 900 degrees, an old-glass powder which has been mixed with mineral additives. The origin of the glass plays a minor role. New glass can also be used for producing the foam-glass ballast. The process for producing this foam-glass ballast is described in European Patent No. 0 292 424, for example.
Foam glass is known as an inert insulating material with relatively high compressive strength. Foam-glass ballast is employed, inter alia, for perimeter insulations, granular subbases beneath structures, as lightweight ballast for pressure-equalising layers in road construction. In this connection the low weight per unit volume and the insulating property of the foam glass are primarily utilised, but its good and stable compressibility is also utilised. Furthermore, the permeability in respect of water even of the compressed structure of the ballast is valued in particular. The permeability in respect of water is based on the large cavity cross-sections between the foam-glass lumps of practically uniform size. Thanks to the absence of fines, the permeability in respect of water an be utilised permanently without any risk of flushing out. Since the individual foam-glass lumps in the texture interlock by claw action with the sharp edges in the innumerable broken-open gas pores of the surface of the foam-glass lumps, foam-glass ballast exhibits the very steep angle of repose of about 45°. It can therefore also be employed in the domain of securing slopes.
The term ‘glass’ in this context is to be understood to mean a broad range of vitrified and glass-like materials, such as new glass of any composition, old glass of any origin, slag from incineration plants and also, in particular, slag from blast furnaces. It has been shown that blast-furnace slag from steelworks can be processed into foam glass in a process that consumes practically no energy. The product that is obtained thereby apparently exhibits an even higher compressive strength and a lower weight per unit volume than the foam-glass product derived from old glass which is described further below. In addition, its cost is far more favourable than that of the foam glass derived from old glass with relatively high expenditure of energy.
According to the “
Enzyklopädie Naturwissenschaft und Technik
”, Verlag Moderne Industrie, Munich 1980, a normal concrete (normal heavy concrete) has a bulk density from 2.2 to 2.5 t/m
3
, a compressive strength from 16 to 60 MPa (=N/mm
2
) and a thermal conductance of 1.97 W/mK. In order to obtain a lower weight and a lower coefficient of thermal conduction, some of the aggregates constituted by sand, gravel or stone chippings can be replaced by various lighter aggregates with inclusions of gas, e.g. pumice stone or expanded clay, or a viscous ultra-fine mortar can be interspersed with gas bubbles. As a result, lightweight concrete is obtained. According to the aforementioned encyclopedia, lightweight concrete can be subdivided into four groups. 1st Group: dense lightweight-aggregate concrete which can be used structurally for high-rise and industrial buildings as well as bridges. Parameters: bulk density 1.4 to 1.9 t/m
3
; compressive strength 16 to 45 MPa (=N/mm
2
) and thermal conductance 0.58 to 1.38 W/mK. For this concrete, use is made of the normal concrete aggregates, but they are partially replaced by lightweight aggregates. Expanded clay and expanded slate are specified as special aggregates. The grain-structure type is closed. Foam-glass lumps are proposed in EP 0 012 114 and in JP-A-10 203836 as a further possible lightweight aggregate for a concrete pertaining to this first group.
In EP 0 012 114 a process is described for producing a foam-glass granulate from a powdered glass with pasty expanding agents which consist of organic and inorganic substances. The granulate consists of fragments of a foam-glass body and comprises 100,000 to 3 million small bubbles having approximately the same size per cm
3
of granulate compound. It exhibits a compressive strength of 130 kg/cm
2
. In one embodiment the grains of the granulate have beaded edges. In order to obtain the beaded edges, the granulate is worked mechanically, e.g. in a device resembling a sugar-coating drum, in such a manner that the edges are crushed. The granulate that is obtained with this process is, according to the disclosure, fine-pored and very lightweight and can be used as an aggregate for lightweight concrete or as a filler for plastics.
Proceeding from known processes for producing globular foam-glass bodies that find application as filling material for lightweight mortar and from known processes for producing plate-like foam glass, in JP-A-10 203836 a process is described which is practically identical to the process according to the substantially older patent specification EP 0 292 424. With this process, according to the disclosure, a foam glass having an undefined massive form is obtained which exhibits a relative density of 0.2, a proportion of adhering water of 7% and an average grain diameter of 3 cm. The following are proposed as advantageous uses of this foam glass:
raising of the ground level in the case of a soft and weak subsoil, whereby a lateral flowing movement can be suppressed,
drainage layer, e.g. beneath tennis courts,
thermal insulation in the roof area or floor area,
weight-reducing aggregate added to concrete,
soundproofing and earthquake protection.
A second group of lightweight concrete is constituted, according to the “Enzyklopädie Naturwissenschaft und Technik”, by particulate-pored lightweight aggregate concrete. The latter can be employed structurally and for thermal insulation in the form of cavity blocks, large slabs and large blocks. Parameters: bulk density 1.0 to 1.4 t/m
3
; compressive strength 2.5 to 8 MPa (=N/mm
2
) and thermal conductance 0.41 to 0.58 W/mK. Expanded clay and expanded slate, but also pumice slag, sintered ash and other aggregates are specified as aggregates for this concrete. The grain-structure type is open.
A third group is constituted by aerated concrete (gas-silicate concrete, foamed concrete), which can be employed structurally and for thermal insulation in the form of structural members for walls, roofing slabs and insulating concrete. Aerated-concrete blocks are also known. Parameters: bulk density 0.3 to 1.0 t/m
3
; compressive strength 0.5 to 15 MPa (=N/mm
2
) and thermal conductance 0.058 to 0.41 W/mK. Fine sand, fly ash and slag sand are specified as aggregates for this concrete. The grain-structure type is fine-pored.
According to the aforementioned encyclopaedia, insulating concrete, which can be employed merely for thermal insulation in the form of insulating slabs, constitutes a fourth group. Parameters: bulk density 0.3 t/m
3
; compressive strength inadequate for load-bearing units, and thermal conductance 0.035 to 0.35 W/mK. Kieselguhr and pearlite are specified as aggregates for this concrete.
These four concrete groups show clearly that in the case of the known types of lightweight concrete the compressive strength falls below 16 N/mm
2
as soon as the coefficient of thermal conduction falls below 0.5 W/mK or the weight per unit volume falls below 1

Affiliated with

Also associated with

Rating

Lightweight concrete does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Lightweight concrete, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lightweight concrete will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3037165