耐火混凝土研究进展论文

通过分析普通混凝土受热作用机理,各国研究表明,混凝土在火灾中受损的严重程度取决于以下六个因素:温度升高的速率、最高温度、胶凝材料和集料的组成、水分含量及火作用的持续时间。因此,提高混凝土的防火耐热性,是减少混凝土在火灾中受损以至坍塌的关键,防火耐热混凝土是一种能长期承受高温作用(200℃以上),并在高温下保持所需要的物理力学性能(如有较高的耐火度、热稳定性、荷重软化点以及高温下较小的收缩等)的特种混凝土。防火耐热混凝土已成功地由耐火骨料(粗细骨料)与适量的胶结料(有时还有矿物搀合料或有机搀合料)和水按一定比例配制而成。

看看合不合适

您好，回家您问题之前需要先问您一个问题。您说的是普通建筑用混凝土还是耐火(耐热)混凝土。这两个耐热温度差距较大。如果是普通建筑用混凝土耐高温最多不超过300℃。如果是耐火(耐热)混凝土可以耐800℃~1300℃的高温，部分材质好的可以耐1300℃以上的高温。

耐火混凝土是一种特殊的混凝土，相对普通混凝土而言，它热稳定良好、制作工艺简单，并且能够适应多种要求比较苛刻的场景，因此在许多生产生活场景中扮演者比较重要的角色。那么接下来不妨就随小编一起来了解几个关于耐火混凝土的相关文字图片信息吧。我们将为大家详细介绍耐火混凝土的简介、优点以及耐火混凝土的分类这三个方面的内容。

一、耐火混凝土的简介

由适当的胶凝材料、耐火骨料、掺合料和水按一定比例配制而成的特种混凝土。

能在900℃以上高温长期作用下保持所需要的力学性能。其性质取决于所所有骨料、掺合料和胶凝材料的材质及其配比。其材质、组成与配料与耐火浇注料相似。

耐火骨料可采用重矿渣、碎耐火砖、玄武岩、铝矾土熟料、烧结镁砂等。根据所用胶凝材料，可分为硅酸盐水泥耐火混凝土、铝酸盐水泥耐火混凝土、水玻璃耐火混凝土、磷酸盐耐火混凝土、镁质耐火混凝土等。

耐火混凝土中的粒状料和粉状料分别称为骨料和掺合料。混凝土的混合物可采用浇注、振动或捣打的方法成型，并根据胶凝材料的硬化特性(如气硬性、水硬性、热硬性等)，采用相应措施促使其硬化。

主要用于构筑工业窑炉中的整体炉衬和制成预制块。其中用于900℃以下的称为耐热混凝土，用于工业窑炉和热工设备的基础与烟囱等。

二、耐火混凝土的分类

由耐火集料、粉料和胶结料加水或其他液体配制不经煅烧而直接使用的不定形耐火材料，也称耐火灌筑材料。它可分为：①普通耐火混凝土。所用集料有高铝质、粘土质、硅质、碱性材料(镁砂、铬铁矿、白云石等)或特种材料(碳素、碳化硅、锆英石等)，也可以采用几种耐火集料组合。②隔热耐火混凝土。主要用耐火轻集料配制。所用轻集料有膨胀珍珠岩、蛭石、陶粒、多孔粘土熟料、空心氧化铝球等，也可用几种耐火轻集料组合，或与耐火集料共同组合。耐火混凝土所用胶结料有高铝水泥、磷酸盐胶结料、水玻璃胶结料、粘土等。

耐火混凝土为不烧制品，生产工艺简单，节省能源，可按照需要造型,整体性比砖砌炉衬好,适宜于机械化施工，合理利用时往往能延长炉衬寿命。耐火混凝土主要用于冶金、石油、化工、建筑材料、机械等工业窑炉中。一般使用温度为1300～1600°C。使用温度低于900°C的耐火混凝土称为耐热混凝土，主要用于热工设备的基础、烟囱、烟道等构筑物中。

三、耐火混凝土的优点

1、耐火度与同材质的耐火砖差不多，但由于耐火混凝土(浇注料)未经烧结，初次加热时收缩较大，故荷重软化点比耐火砖略低。尽管如此，从总体上衡量，性能优于耐火砖。

2、耐火混凝土优于低温胶结剂料的作用，常温耐压强度较高。同时因为砌体的整体性好，炉子的气密性好，不易变形，外面的炉壳钢板可以取消，炉子抗机械震动和冲击的性能比砖的砌体好。例如用于均热炉的侧墙上部，该处机械磨损和碰撞都比较厉害，寿命比砖砌的以高了数倍。

3、热稳定性好，骨料大部分或全部是熟料，膨胀与胶结料的收缩相抵消，故砌体的热膨胀相对来说比砖小，温度应力也小，而且结构中有各种网状、针状、链状的结晶相。抗低温度应力能力强。例如用来浇注均热炉炉口及炉盖，寿命延长到一年半。

4、生产工艺简单，取消了复杂的制砖工序。可以制成各种预制块，并能机械化施工，大大加快了筑炉速度，比砌砖效率提高十多倍。还可以利用废砖等作骨料，变废为利。

以上我们为大家详细介绍了关于耐火混凝土的相关方面的信息，主要是耐火混凝土的简介、优点以及耐火混凝土的分类这三个方面的内容。通过介绍，我们了解到耐火混凝土作为一种特殊的混凝土，最突出的特性就在于它耐高温的优势。除此之外，它还具有稳定性高、生产工艺简单等等优势。这也使得耐火混凝土能够胜任某些特殊场景的功能需求。

Dry phosphate refractory concrete materials AbstractThe present invention is directed to a dry phosphate cement mixture and process for manufacture of same. The dry mixture includes at least Al(H2 PO4)3, a group IIA metal bonded to oxygen, and an aggregate. The process for manufacturing cement includes associating the dry reagent with a substantially polar solvent, such as water. The total reagent concentration is formulated such that only nominally exothermic reactions are observed. The process accommodates variable setting times and provides resulting concrete which exhibits formidable structural integrity. Claims What is claimed: 1. A refractory cement mixture comprising a dry reagent composition including: at least one oxide of an element belonging to group IIA of the periodic table present in an amount of to percent by weight of the dry reagent composition; Al(H2PO4)3 ; and at least one aggregate, wherein the aggregate is selected from the group consisting of olivine, silica, aluminum oxide, kyanite and bauxite. 2. The refractory cement mixture according to claim 1, further including an aqueous medium. 3. The refractory cement mixture according to claim 2, wherein the aqueous medium consists of a polar solution. 4. The refractory cement mixture according to claim 1, wherein the Al(H2 PO4)3 is present in an amount of about to percent by weight of the total dry reagent composition. 5. The refractory cement mixture according to claim 1, wherein the at least one aggregate is present in the amount of from about 75 to 95 percent by weight of the dry reagent concentration. 6. The refractory cement mixture according to claim 1, wherein the group IIA oxide has a particle size range from minus twelve to positive three hundred mesh. 7. The refractory cement mixture according to claim 1, wherein the group IIA oxide comprises MgO. 8. A process for manufacturing refractory cement comprising: dry mixing active reagents so as to form a dry reagent composition, wherein the active reagents include: at least one oxide of an element belonging to group IIA of the period table present in the amount of to ; Al(H2 PO4)3 ; and at least one aggregate, wherein the aggregate is selected from the group consisting of olivine, silica, aluminum oxide, kyanite and bauxite. 9. The process according to claim 8, wherein the Al(H2 PO4)3 is present in an amount of about to percent by weight of the total dry reagent composition. 10. The process according to claim 9, further comprising the steps of: charging water into the dry mixture of active reagents and an aggregate such that an aqueous mixture is synthesized during a exothermic reaction; and curing the resulting aqueous mixture. 11. The process according to claim 10, further comprising the step of: varying the amount of one or both of the oxide of an element belonging to group IIA of the periodic table or the Al(OH2 PO4)3 to, in turn, adjust the curing time of the resulting aqueous mixture. 12. The process according to claim 8, further comprising the steps of: charging water into the dry mixture of active reagents and an aggregate such that an aqueous mixture is synthesized during an exothermic reaction; and curing the resulting aqueous mixture. 13. The process according to claim 12, wherein the process further comprises the step of: varying the concentration of one or both of the oxide of an element belonging to group IIA of the periodic table or the Al(H2 PO4)3 to, in turn, adjust the curing time of the resulting aqueous mixture. 14. The process according to claim 10 wherein the active reagents have a particle size and the curing time of the aqueous mixture is varied by varying the particle size of one of the reagents. 15. The process according to claim 12 wherein the active reagents have a particle size and the curing time of the aqueous mixture is varied by varying the particle size of on of the reagents. Description BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates in general to dry phosphate refractory concrete materials having MgO and AI(H2 PO4)3, and more particularly, to special compositions which when synthesized yield nominally exothermic reactions, and use virtually "catalytic" amounts of active materials without sacrificing either structural integrity or variable setting times. 2. Background Art Refractory concretes, also known as castables, are normally bonded with high-temperature calcium aluminate cement. Cement adlevels commonly range from one to forty percent and setting times are typically variable and range from 30 minutes to over 3 hours. In some instances, a fast setting time is desired, for example, when specialized manufacturing of uniquely-shaped burner block is desired, or, when rapid furnace repairs or patches are needed. Inasmuch as many thousands of dollars per hour are lost while a furnace is non-operational, minimizing such furnace down time is essential. Another example of when a fast set of the refractory material is desired is during the forming and pouring of furnace walls when construction time is extremely limited due to scheduling demands. Indeed, while accelerating the setting time of calcium aluminate concretes is known in the art, the ultimate structural integrity of the material does become adversely affected. Additionally, the initial dry-out and heat-up of the calcium aluminate concrete castable takes a substantial amount of time regardless of, and in addition to, the initial setting time of the mixture. In addition to the above, safety must be considered when configuring a furnace heat-up schedule. For example, refractory calcium aluminate cement develops strength after hydrating the chemical reagents. Sufficient water must be charged to a cement-bonded high-temperature concrete to hydrate the cement and allow for placement and/or movement of the mass. After the cement-bonded concrete is hardened, the water must be removed slowly before the furnace can be put back into service. Consideration must be given to the permeability of the mass, dynamics of the cement phases and its hydration level. The end result is that heating rates for concrete cure can require up to several hundred hours to reach the furnace operating temperature. As the concrete is heated, the mass functions as a "leaky" autoclave. The pressure caused by the vaporization of the free water and steam released from the dehydration of the cement can be explosive, if the pressure exceeds the tensile strength of the castable. Even if the mass does not actually explode, rapid heating can cause internal cracking and damage that will shorten the ultimate life of the concrete material. This damage is known as thermal shock damage. The long turn-around times for concrete furnace linings and possible thermal shock damage are just part of the problem associated with conventional refractory material. Indeed, if the furnace lining comes into contact with molten metal, an adverse chemical reaction can occur. This adverse reaction, as observed in calcium aluminate cement systems, is considered a weak link in the ability of refractory concretes to resist molten metal attack and/or penetration of the furnace lining. Phosphate refractory concretes, on the other hand, have several advantages over traditional calcium aluminate cement-bonded products. The first benefit is that the phosphate bond is not affected by molten aluminum. The metal is non-reactive with the phosphate, unlike the calcium aluminate of traditional cements. Another benefit is curing or firing time. Phosphate-bonded materials generally can be heated much faster than traditional cement-bonded products. Furthermore, there is a much lower chance for sustaining thermal shock damage. Phosphate-bonded concretes use many different types of phosphates and often have a basic component such as magnesium oxide (MgO) which reacts with the phosphate in the presence of water (or an aqueous liquid) whereupon hardening occurs. Although such conventional phosphate bonded concretes have exhibited various benefits over other conventional refractory materials, problems nevertheless persist. For example, when phosphate-bonded concretes are used, the reaction rate is often so fast that the concrete cannot be poured into place before it hardens. Additionally, when a liquid phosphate or phosphoric acid is used, safe handling of the toxic liquid presents a real hazard, not to mention the burden associated with working with a two-phase system. Greger, . Pat. No. 2,450,952 (hereinafter "Greger '952") appears to disclose a dry phosphate cement mixture for adhesive applications. The reagents used in Greger '952 included magnesia, olivine and or magnesium silicate mixed with water soluble aluminum phosphate. The weight ratio of the magnesium compound to the phosphate is disclosed to be 2:1 to 8:1. Inasmuch as the set is relatively fast when magnesia is used as a reagent, Greger '952, discloses substituting olivine for the magnesia, to, in turn, slow the set time for as much as 24 hours. However, olivine has limited high temperature applications due to melting point considerations and chemical reactivity at high temperature. Tomic, . Pat. No. 4,392,174 (hereinafter "Tomic '174") appears to disclose a mixture of magnesium oxide in aluminum phosphates, as well as using aluminum phosphates in liquid form. Aggregates, such as gravel or trap rock are combined with a mixture of magnesium oxide and phosphate, and then used for such applications as patching of highways. However, Tomic '174 teaches the use of high magnesium oxide concentration (as well as other high reagent concentrations). Although such a high concentration appears to provide a phosphate cement with great structural integrity, the percent composition of the active reagents is undesirably high. The result of having such high concentrations of active reagents is that undesirable levels of heat are generated as a result of the exothermic nature of the chemical reaction. Furthermore, the cost of the active reagents in phosphate concretes are quite expensive when compared to the cost of the inactive reagents. When used in such great concentrations, as taught in Tomic '174, the profitability of an installation is adversely affected. It is thus an object of the present invention to provide a dry phosphate refractory concrete which can be synthesized in a cost effective manner. It is a further object of the present invention to provide chemical compositions, such that when synthesized, liberate nominally exothermic properties. It is yet a further object of the present invention to provide phosphate concretes as described above, without sacrificing structural integrity or the necessary enhancement of variable setting times. More particularly, it is an object of the present invention that regardless of the specific active reagent concentrations (such as those experimentally identified in the present disclosure, relative to the present invention), other reagent concentrations less than conventionally known, and, which, in such relatively low concentration result in hardened refractory material maintaining excellent structural characteristics, are likewise fundamental to the objective parameters of the present invention. SUMMARY OF THE INVENTION The present invention is directed to a cement mix comprising: a dry reagent composition including; at least one active dry reagent selected from the group consisting of group IIA elements associated with oxygen, and another active dry reagent comprising Al(H2 PO4)3, wherein the concentration of the group IIA oxide ranges from about to percent by weight of the total dry reagent composition; and at least one aggregate. In a preferred embodiment of the invention, the cement mix further includes an aqueous medium. Additionally, it is contemplated that the aqueous medium is substantially polar. In another preferred embodiment of the invention, the aggregate is selected from at least one of the group consisting of Olivine, Kyanite, Silica, Bauxite, Aluminum oxide and minerals or synthesized derivatives thereof. In yet another preferred embodiment of the invention, the group IIA oxide includes MgO. The invention further contemplates that the MgO has a distribution range from minus twelve to positive three hundred mesh. Moreover, the invention contemplates that the Al(H2 PO4)3 concentration ranges from about to percent, and the at least one aggregate concentration ranges from about 75 to 95 percent by weight of the total dry reagent composition. The present invention is also directed to a process for manufacturing cement comprising the steps of: a) dry mixing active reagents, wherein the active reagents includes; at least one active dry reagent selected from the group consisting of group IIA elements associated with oxygen, and another active dry reagent comprising Al(H2 PO4)3, wherein the concentration of the group IIA oxide ranges from about to percent by weight of the total dry reagent composition; and at least one aggregate; b) charging an aqueous medium into the dry mix active reagents and aggregates, wherein the step of charging includes maintaining a net active reagent concentration equal to or less than the necessary concentration for observing nominally exothermic synthesis, to in turn, result in an aqueous mixture; and c) setting the resulting aqueous mixture. In a preferred embodiment of the invention, the process further comprises the step of varying setting times of the resulting aqueous mixture. Moreover, the invention contemplates that the step of varying setting time comprises altering one of at least the dry reagent composition concentrations and particle distribution range. In another preferred embodiment of the process, the active reagent concentration of Al(H2 PO4)3 ranges from about to percent, and the at least one aggregate concentration ranges from about 75 to 95 percent by weight of the total dry reagent composition. DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there is described in detail a specific embodiment with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment described hereinbelow. At the outset, when magnesium oxide and aluminum phosphate are charged with water, a well-known acid-base type reaction occurs. The concentration of magnesium oxide and its particle size generally determine the setting time of the concrete. The concentration of MgO and Al(H2 PO4)3 directly affects the exothermic magnitude of the chemical reaction. Indeed, when "non-catalytic" amounts of active reagents are used, a significant exothermic reaction is observed. Accordingly, in each experiment in the present invention, the peak exotherm was nominal as a result of the virtually "catalytic" amounts of active reagents. Dry phosphate concretes of high structural integrity were synthesized using significantly less MgO and Al(H2 PO4)3 than contemplated by the prior art (see, for example Tomic '174). Moreover, as shown in experiments one, two and five, variable set times were still maintained using such diminished concentrations of active reagents. Amazingly, even with virtually "catalytic" (limited) amounts of active reagents, the phosphate refractory concretes maintained a very high degree of structural integrity. In support of such an invention, several experiments were conducted. The results are summarized herein-below. Specifically, seven experiments were conducted, wherein the following common experimental procedure was used: First, the dry reagents, which include at least the aggregate, MgO, and Al(H2 PO4)3 in which the phosphorus pentoxide (P2 O5) concentration was approximately sixty percent, were charged into a reaction vessel. Second, the dry reagents were mixed via conventional agitation methods for approximately fifteen minutes. Third, the reaction vessel was charged with H2 O, which resulted in a "concrete" slurry that was agitated for an additional two minutes. Fourth, the "concrete" reaction mixture was set and cast, which provided suitable material for analytical testing. Next, test samples were analyzed primarily for structural integrity via cold crushing strength methods (CCS). Additionally, analytical test data relating to net structural composition was provided when applicable. These additional tests included compositional density (.rho.) and modulus of rupture (MOR). EXPERIMENT NO. 1 In this experiment, the following dry reagents and their respective percent composition by weight were used: ______________________________________ Dry Reagent Percent Composition ______________________________________ Olivine Silica Fume Surfactant MgO Al(H2 PO4)3 Non-Wetting Agent ______________________________________The olivine used in this experiment consisted primarily of four dimensionally different aggregates. The grain sizes of the respective primary aggregates included: 3×50 mesh, 16×70 mesh, 12×40 mesh and 140 mesh material. Furthermore, the chemical composition of the olivine used in this experiment was ninety percent forserite () and ten percent fayalite (Fe2 SiO2). Moreover, the silica fume used was approximately ninety-five percent silica (SiO2) and dimensionally less than one micron. The magnesite (MgO) was technical grade and processed from sea water which was then calcined in a shaft kiln. The grain size of the MgO was one hundred mesh. However, other particle sizes, such as positive three hundred mesh, are suitable for use as well. Anyone of a number of conventional non-wetting agents which are understood in the art can be used. After following the experimental procedure (as previously described), H2 O (by weight) was charged into the reaction vessel and a nominally exothermic reaction was observed. Thereafter, 2×2×2" cubes were formed via vibration casting. The chemical composition of the "concrete" in this experiment provided a hardening ("set") time of ninety minutes. Test data was then collected following conventional industrial method ASTM C133. The test results after drying for sixteen hours at 230° F. provided a compositional density (.rho.) of 158 pounds per cubic foot (pcf) and a MOR of 166 pounds per square inch (psi). After heating to 1,000° F. and holding the temperature constant for five hours, the MOR increased to 966 (psi), and the CCS was then measured at 3,925 (psi). EXPERIMENT NO. 2 In this experiment, the following dry reagents and their respective percent composition by weight were used: ______________________________________ Dry Reagent Percent Composition ______________________________________ Bauxite 60% Al2 O3 Aggregate Bauxite Fines Kyanite Al2 O3 MgO Al(H2 PO4)3 Non-Wetting Agent ______________________________________The bauxite used in this experiment was a South American bauxite and was elementally eighty-nine percent Al2 O3 and has a granular range from minus three to positive six mesh. The sixty percent Al2 O3 aggregate was supplied from C-E Minerals in Andersonville, Ga. and is also known commercially as Mulcoa-60. Furthermore, the Kyanite used in this experiment was supplied by Kyanite Mining

混凝土能耐300度的高温，耐热混凝土最高使用温度可达1200摄氏度。

混凝土由胶凝材料将骨料胶结成整体的工程复合材料的统称。通常讲的混凝土，是指用水泥作胶凝材料，砂、石作骨料，与水或含外加剂和掺合料按一定比例配合，经搅拌而得的水泥混凝土，也称普通混凝土，它广泛应用于土木工程。

发展历史

考古人员发现5000年前的凌家滩先民不仅能够制造精美的玉石器，而且已开始稻作农业，饲养或捕猎猪、鹿、鸟禽等多种动物丰富饮食品种。另外在房屋建设中，他们已懂得类似钢筋混凝土的：“挖槽填烧土，木骨撑泥墙”的建筑工艺。

5000年前的凌家滩人不是只会简单的搭建屋舍，事实证明，当时的凌家滩人已懂得“挖槽填烧土，木骨撑泥墙”的建筑工艺，这和如今的钢筋混凝土非常相似。工作人员说，原始先民要用经过火烧过土作为房基槽与墙体的填充材料，在基槽内用木棍作为墙体的支撑柱，然后填埋红烧的土块，并在墙体两侧表面敷上较厚的粘泥，甚至一部分还可能用芦苇杆加固。