JPH0215510B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL FIELD OF APPLICATION The present invention relates to a rapidly hardening cement mixture containing reinforcing fibers, which is particularly suitable for the continuous production of cementitious molded bodies. BACKGROUND OF THE INVENTION When cementitious hardened materials are used to continuously or semi-continuously manufacture plates, blocks and other shaped bodies in a factory, the hardened materials maintain sufficient fluidity during the time required for shaping; After that, it is desired that the material cures rapidly and develops a strength that allows it to be removed from the mold within as short a time as possible. In many cases, the time required to maintain fluidity is on the order of several minutes to several tens of minutes. Normally, Portland cement is not suitable for such applications because it takes several hours to harden to the point where it can be demolded. Therefore, many proposals have been made for portland cement that is given rapid hardening by blending other hardening materials and hardening accelerators, as well as special rapid hardening cements. Typical examples of the former include alumina cement-Portland cement-slaked lime systems, alumina cement-Portland cement-gypsum systems, and calcium aluminate-based special admixtures; A typical example of this is jet cement (trade name). When actually molding a rapidly hardening cementitious material, a setting retarder is often added to adjust the setting time, or a fibrous material is mixed in for reinforcement. Problems to be Solved by the Invention However, with conventional rapidly hardening mixed cementitious molding materials, it is generally difficult to control the setting time, the shrinkage during the hardening process is large, and the strength after hardening is not sufficient; In the case of using a special admixture, it is expensive, and it is not easy to shorten the curing time. It was difficult to manufacture at low cost. An object of the present invention is to solve these problems in conventional rapidly hardening cementitious molding materials. Means for Solving the Problems The rapid hardening cement composition provided by the present invention contains calcium silicate, auin (3CaO・3Al ₂ O ₃・
Alumina cement, slaked lime, and reinforcing fibers are blended with low alkaline cement whose main components are CaSO ₄ ) and silicic acid, and the amount of low alkaline cement is calculated based on the total amount of the above low alkaline cement, alumina cement, and slaked lime. is 79 to 91% by weight, and the amount of slaked lime is 10 to 30% by weight based on the alumina cement. To explain each component of the rapid hardening cement mixture of the present invention, "low alkaline cement whose main components are calcium silicate, auin, and silicic acid" (hereinafter referred to as low alkaline cement) is:
It has recently been developed and commercially available mainly for use in glass fiber reinforced concrete, and is characterized by lower alkalinity than that of Portland cement and rapid hardening properties. Comparing the chemical composition of Chichibu GRC cement (product of Chichibu Cement Co. _, Ltd.), which is one example, with that of ordinary Portland cement, it is as _follows .
There are a lot of SO ₃ .

[Table] As the alumina cement, normal calcium aluminate cement can be used.
As the slaked lime, common commercially available products such as specially selected slaked lime for plasterers can be used. Gypsum is
Any of hemihydrate gypsum, dihydrate gypsum, and type anhydrous gypsum may be used, but hemihydrate gypsum is preferred. In addition, in general, rapid-setting cement essentially prevents premature setting by adding a setting retarder, and many commercial products of low-alkalinity cement already contain a setting retarder, but alumina cement and slaked lime are not included. When blending requires adjustment of setting time, a setting retarder may be further added. As the setting retarder, for example, sodium citrate, calcium 2-ketogluconate, etc. can be used. Special reinforcing fibers are not required, and alkali-resistant glass fibers, aramid fibers, carbon fibers, vinylon, nylon, etc. can be used. A suitable amount of reinforcing fibers is about 0.5 to 5% by weight based on the total amount of the cured material consisting of the above three components. The rapid hardening cement composition of the present invention may contain other auxiliary components, such as cement dispersants (water reducers), antifoaming agents, foaming agents, thickeners, anti-whitening agents, pigments, etc., as necessary. can be done. The rapid hardening cement composition of the present invention may be prepared by uniformly mixing all of its components and then kneading and shaping it by adding only water at the time of use, or by mixing while adding some components during the kneading process. Good too. Examples Hereinafter, the present invention will be explained with reference to Examples and Comparative Examples. Cement (Chichibu GRC cement, ordinary Portland cement or early strength Portland cement), alumina cement, slaked lime (special grade for plastering),
Alkali-resistant glass fiber for reinforcement (Nippon Electric Glass,
H200) and set retarder (sodium citrate)
were blended in the proportions shown in Table 1 to obtain a rapid hardening cement composition. These formulations were then mixed with No. 5 silica sand in the amounts listed in Table 1 (but only in some examples) and water (2 minutes in a mortar mixer) and immediately placed in a 4 x 4 x 16 cm mold. After curing, the mold was removed, and after curing at 35±5°C for 12 hours, it was placed in a plastic bag and left to naturally cure in a sealed state (temperature: approximately 20°C). In the above molding process, setting time (determined by touch when fluidity disappears), curing time (time when the estimated compressive strength reaches 20 kg/cm ² by touch), and dimensional change (demolding of the 16 cm side of the test piece) Table 1 shows the results of examining the dimensional changes (up to the time of strength measurement after 28 days) and the physical properties of the molded products after 28 days of curing.

[Table] Effects of the Invention The rapid hardening cement composition of the present invention has appropriate setting start time and time to reach demolding strength, and is suitable for continuous molding; does not require heating for rapid hardening; Because there is very little compression during the curing process, molded products with high dimensional accuracy can be easily obtained; because the curing material has a low alkalinity,
Even when glass fiber is used for reinforcement, there is little deterioration due to alkali; the final strength of the molded product is excellent; and so on. Therefore, by using the rapidly hardening cement composition of the present invention, high-quality cement-based molded bodies can be produced efficiently and at low cost.

Claims (1)

[Claims] 1 Alumina cement, slaked lime, and reinforcing fibers are blended with a low alkaline cement whose main components are calcium silicate, auin, and silicic acid, and the low alkalinity is low relative to the total amount of the above low alkaline cement, alumina cement, and slaked lime. Rapid hardening cement formulation characterized in that the amount of cement is 79-91% by weight and the amount of slaked lime is 10-30% by weight relative to alumina cement.