Fly ash cementitious material and method of making a product

• US Patent #: 5,601,643

This invention provides rapid curing, high strength cementitious mixtures comprising fly ash and alkali metal or alkaline earth metal silicate binder, hereafter referred to as CAFA binder mixture. The alkali metal or alkaline earth metal silicate binder has a weight ratio of SiO.sub.2 :M.sub.2 O of about 0.20:1 to about 0.75:1, preferably about 0.5:1 to about 0.6:1, wherein M is any of Li, Na, K, 1/2Ca and 1/2Mg. Preferably, the fly ash is Class F or Class C fly ash, more preferably Class F fly ash. Preferably, the silicate binder comprises a sodium silicate component and a sodium hydroxide component. Preferably, the sodium silicate component is an aqueous solution that comprises about 38% to about 55% sodium silicate solids content and which has a SiO.sub.2 :Na.sub.2 O ratio of about 2:1 to about 3.22:1, and about 45% to about 62% water based on the weight of the alkali silicate component, i.e., the aqueous sodium silicate solution. Preferably, the sodium hydroxide component comprises about 25% to about 100% sodium hydroxide and up to about 75% water based on the weight of the sodium hydroxide component.

The CAFA binder mixtures can be admixed with fine aggregates to provide CAFA mortar mixtures. The CAFA mortar mixtures can be combined with coarse aggregates, optionally with fibers, to provide CAFA concrete mixtures. Any of the CAFA binder, mortar and concrete mixtures can be cured at elevated temperatures of about 40.degree. C. to about 120.degree. C. to yield high strength products.
 

Particulate rubber included concrete compositions

• US Patent #: 5,456,751

Concrete compositions are provided which contain particulate rubber, preferably recycled rubber from such sources as automobile tires, in amounts between about 0.05 and about 20 percent by weight of the concrete composition. The concrete compositions further contain portland cement, water, and an aggregate material. Additional materials such as plasticizers or superplasticizers and fly ash can also be admixed with the concrete compositions.

A preferred particle size distribution for the particulate rubber is one such that from about 50-95 weight percent of the rubber particles pass through a 3/8 inch. sieve, about 20-75 weight percent of the rubber particles pass through a No. 4 sieve, and from about 0-30 weight percent of the particles pass through a No. 8 sieve. Generally less than about 10 weight percent of the rubber particles are retained on a 0.5 inch sieve.
 

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