A space filler for forming a fibrous preform may comprise an additively manufactured ceramic material. The additively manufactured ceramic material may define a plurality of pores. A shape of the additively manufactured ceramic material may complement a shape of a void formed by fibrous regions of the fibrous preform.

A ceramic precursor mixtures for extrusion and firing into porous ceramics. The ceramic precursor mixtures include ceramic beads and green inorganic shear binder agglomerates. The green inorganic shear binder agglomerates can include inorganic filler particles and a polymeric binder. The green inorganic shear binder agglomerates can deform under an applied shear stress during mixing and/or extrusion such that they are smeared into a plurality of interbead gaps between adjacent ceramic beads or pore former particles. During firing, the smeared green inorganic shear binder agglomerates can sinter and react to form ribbons extending between, and interconnecting adjacent ceramic beads.

A porous refractory in the K.sub.2O—SiO.sub.2—B.sub.2O.sub.3 system is formed by chemical direct foaming by heating to over 600° C., resulting in adherent black or white foam. The foam can function as highly porous thermal insulation, a high or low thermal emissivity surface, as a sealant for deteriorated refractory surfaces, as a filler for pockmarks/holes/gaps or as a bonding agent for parts with large gaps between them.

A porous refractory in the K.sub.2O—SiO.sub.2—B.sub.2O.sub.3 system is formed by chemical direct foaming by heating to over 600° C., resulting in adherent black or white foam. The foam can function as highly porous thermal insulation, a high or low thermal emissivity surface, as a sealant for deteriorated refractory surfaces, as a filler for pockmarks/holes/gaps or as a bonding agent for parts with large gaps between them.

A porous refractory in the K.sub.2O—SiO.sub.2—B.sub.2O.sub.3 system is formed by chemical direct foaming by heating to over 600° C., resulting in adherent black or white foam. The foam can function as highly porous thermal insulation, a high or low thermal emissivity surface, as a sealant for deteriorated refractory surfaces, as a filler for pockmarks/holes/gaps or as a bonding agent for parts with large gaps between them.

A composite article is comprised of coal dust, as defined herein, and a polymer derived ceramic material that is pyrolyzed in a substantially non-oxidizing atmosphere. For example, the composite article may be made of a mixture of the coal dust and polymer derived ceramic, from particles formed of a mixture of coal dust and polymer derived ceramic or from complex particle composites comprising a plurality of particles formed of a mixture of coal dust and polymer derived ceramic.

A composite article is comprised of coal dust, as defined herein, and a polymer derived ceramic material that is pyrolyzed in a substantially non-oxidizing atmosphere. For example, the composite article may be made of a mixture of the coal dust and polymer derived ceramic, from particles formed of a mixture of coal dust and polymer derived ceramic or from complex particle composites comprising a plurality of particles formed of a mixture of coal dust and polymer derived ceramic.

A composite article is comprised of coal dust, as defined herein, and a polymer derived ceramic material that is pyrolyzed in a substantially non-oxidizing atmosphere. For example, the composite article may be made of a mixture of the coal dust and polymer derived ceramic, from particles formed of a mixture of coal dust and polymer derived ceramic or from complex particle composites comprising a plurality of particles formed of a mixture of coal dust and polymer derived ceramic.

A low density annular grout composition for filling voids. The composition may consist of cementitious fly ash, water, set retarder and cellular foam. The composition may have a compressive strength of between 100 and 600 psi at seven days and less than 1500 psi at 28 days. The composition may have a density between 20 and 75 pcf. Also disclosed is a method of filling a void with a low density annular grout composition. The method can include determining the time necessary to fill the void, adding water and set retarder to a cementitious fly ash to make a wet mixture, adding air to the wet mixture, and adding the composition to the void.

A low density annular grout composition for filling voids. The composition may consist of cementitious fly ash, water, set retarder and cellular foam. The composition may have a compressive strength of between 100 and 600 psi at seven days and less than 1500 psi at 28 days. The composition may have a density between 20 and 75 pcf. Also disclosed is a method of filling a void with a low density annular grout composition. The method can include determining the time necessary to fill the void, adding water and set retarder to a cementitious fly ash to make a wet mixture, adding air to the wet mixture, and adding the composition to the void.