Abstract:
A rapid setting cementitious composition useful for making cement boards employs an insoluble form of anhydrous calcium sulfate (anhydrite) to accelerate setting and to permit reducing the amount of high alumina cement usage. The rapid setting cementitious composition comprises as a reactive powder blend: (a) 35 to 90 wt% potland cement; (b) 0 to 55 wt% pozzolan; (c) 5 to 15 wt% high alumina cement and (d) 1 to 8 wt% insoluble calcium sulfate anhydrite.
Abstract:
A high early-strength admixture for precast hydraulic cement comprises a calcium salt and a copolymer having a carbon-containing backbone to which are attached cement-anchoring members, such as carboxyl groups, and to which are also attached oxyalkylene pendant groups by linkages selected from the group consisting of amide and imide members. The copolymers used are preferably formed by reacting an acrylic polymer with ammonia or an alkoxylated amine. The calcium salt, preferably calcium nitrite, and the copolymer can added simultaneously as one admixture, or separately. The invention relates also to methods for enhancing high early strength in concrete, cement, masonry, and mortar mixtures generally, and to precast concrete particularly, and also pertains to such hydraulic mixtures containing the calcium salt and copolymer.
Abstract:
PROBLEM TO BE SOLVED: To provide an ultrarapid hardening grout composition where a long usable time of about 60 minutes can be assured with superior strength development and without lowering compressive strength at a young material age of about 2 hours and where bleeding suppression function, defoaming function and suitable fluidity are assured. SOLUTION: The grout composition involves an admixture including a coagulation moderator consisting of sodium aluminate, an inorganic carbonate and carboxylic acids at a specified ratio to a rapid hardening ingredient in which calcium aluminate whose vitrification rate is 80% or more and an inorganic sulfate are mixed at a specified mass ratio, a cement mineral, quick lime, a defoamer and a thickener. The coagulation moderator contains first particles having a mean particle diameter of more than 45 μm and 90 μm or less of 10-45 mass%, second particles having a mean particle diameter of more than 90 μm and 150 μm or less of 30-70 mass% and third particles having a mean particle diameter of more than 150 μm and 500 μm or less of 5-30 mass%. The second particles are contained more than the third particles. COPYRIGHT: (C)2007,JPO&INPIT
Abstract:
A rapid setting cementitious composition useful for making cement boards employs an insoluble form of anhydrous calcium sulfate (anhydrite) to accelerate setting and to permit reducing the amount of high alumina cement usage.
Abstract:
PROBLEM TO BE SOLVED: To provide fly ash for cement cured body that is capable of obtaining stable and rapid coagulation of cement without inhibiting the curing of cement. SOLUTION: The fly ash for the cement cured body is obtained by dispersing 250 pts.wt. of the fly ash in 500 pts.wt. of water with stirring and adjusting the pH of the filtrate, which is obtained immediately after the stirring, to 6 or higher. Also, the fly ash for the cement cured body is obtained by dispersing 250 pts.wt. of the fly ash in 500 pts.wt. of water with stirring and adjusting the degree of pH change (B)/(A), which is acquired between the pH(A) of the filtrate obtained immediately after the stirring and the pH(B) of the filtrate obtained 30 minutes after being left to stand subsequently to the stirring, to 1.2 or less. COPYRIGHT: (C)2005,JPO&NCIPI