US 5,660,625 A · Use of basic aluminium sulphates as low-alkali set accelerators for cement

Abstract

Improved set accelerating mixtures and their use are disclosed to shorten the period after mixing hydraulically setting building materials, for example cement, up to the transition into the solid phase. The improved set accelerating mixtures comprise basic aluminum sulphates of the formula: Al(OH).sub.a (SO.sub.4).sub.b, in which the subscripts satisfy the conditions: a=3-2b and b=0.05 to 0.4. These basic aluminum sulphates are produced by parallel precipitation from solutions containing aluminum at temperatures usually less than 60.degree. C. by mixing dilute acid solutions and alkaline solutions containing sulphates in the pH range from 5.0 to 8.0 to produce an amorphous, basic aluminum sulphate.

Claims7

Dependent claims

In a process for the accelerated setting and hardening of a hydraulic bonding agent selected from cement, mortar, or concrete, the improvement comprising a set accelerating agent consisting essentially of a homogenized suspension of an amorphous basic aluminum sulphate having the formula:

Al(OH).sub.a (SO.sub.4).sub.b
the indices a and b fulfilling the condition
a=3-2b and b=0.05-0.4,
wherein said homogenized suspension contains 0.5% by weight Al.sub.2 O.sub.3 in distilled water and exhibits after the addition of 0.4% NaOH (with regard to the suspension) a pH value which drops to less than 11.8 within 60 minutes.

1 more element

Dependencies are inferred from the claim text.

Use of basic aluminium sulphates as low-alkali set accelerators for cement

Life of this patent

Use of basic aluminium sulphates as low-alkali set accelerators for cement

Life of this patent

Abstract

Claims7