GB1575075A

GB1575075A - Hydraulic compositions

Info

Publication number: GB1575075A
Application number: GB1044577A
Authority: GB
Original assignee: VIZGAZDALKODASI TUDOMANYOS KUTATO KOZPONT
Current assignee: VIZGAZDALKODASI TUDOMANYOS KUTATO KOZPONT
Priority date: 1977-03-11
Filing date: 1977-03-11
Publication date: 1980-09-17

Description

(54) HYDRAULIC COMPOSITIONS (71) We, VIZGAZDALKODASI TUDOMANYOS KUTATO KOZPONT, a Hungarian Body Corporate, of 1, Kvassay Jeno ut, Budapest 1095, Hungary, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention concerns hydraulic compositions.

The invention more particularly relates to a process for producing a composition with hydraulic bond of high compressive strength, typically over 60 kp/cm2, substantially volumetrically stable after curing, durably retaining its strength properties, with a low or medium bulk density between 1200 and 1900 kg/cm3, and of interest for producing concrete or the like building materials.

As background to this invention, we have noted in the technical literature several publications and proposals dealing with problem of increasing the strength of pulverised fly ash or other pozzolanic materials with cement, or in a few cases with cement and lime, as well as proposals for stabilising different soils and producing heat-treated light-concrete building elements.

From such technical literature it is abundantly clear that theoretical questions in this area have not yet been cleared up; endeavours and trials have been based on experience only. Basic problems, such as the preconditions for forming a stable system from soils of any given composition, especially with other supplemental materials for example pozzolanic materials such as trass or pulverized fly ash together with cement or lime, or using both binding materials, together with water, have not yet been answered.

In these systems, as will be seen later herein, the process of hardening is based primarily on chemical reactions of hydraulic character, whose rate is so slow at normal temperatures that rate of hardening, and the direction which the strength is changing with time cannot be readily determined on specimens of the prescribed and normally tested ages (7 and 15 and in some cases 90 days). It can be stated that by using 6--14% by weight binding material (not often a combination of both cement and lime), as has been proposed in the technical literature, in the majority of cases a stable system is not attained and such methods of testing mentioned above are absolutely unacceptable for determining the required quantity of binding material and the properties of the final product.The systems described do not comply with building requirements; the compressive strength typically amounts td not more than 840 kp/cm2 and shows a rapid decrease in strength after a year, accompanied by disadvantageous changes in volume, resulting in disintegration of the building structure in a short time; such circumstances are described in ASCE Journal of Power Division, January, 1971. K. Szepesi-J. Szilvassi: "Concrete volume change for Dworschak Dam".

In the course of our research work it was among our aims to utilize the systems other thari pozzolanic systems as basic components, as well as to coordinate the quantity of binding materials, primarily that of lime and/or cement, with the other starting materials to ensure a durable and stable product and to ensure improved homogenization.

According to the present state of knowledge and technique, starting materials usable according to our invention, including all systems containing crystalline silicate mineral components e.g. soils and soil-forming minerals such as koalinite, illite, montmorillonite and feldspars, or materials and rocks of any other composition containing aluminates, such as bauxite and laterite, are not considered - as a general rule - as silicate systems of pozzolanic character. By using lime according to known techniques the materials enumerated do not harden at all or only to a small extent and the strength properties of the products are not permanent either.In general, only silicate materials with a vitreous or amorphous structure such as trasses and other tuffs, and pulverized fly ash from coal-fired generated stations are normally considered as pozzolanic materials hardening with lime. Nevertheless, up to now it seems to have been impossible to convert these materials into durable hydraulic systems of satisfactory strength by using lime or cement as binding material. In the course of our research work resulting in the process according to the invention, conditions for inducing pozzolanic reactions and the kinetics of the reaction of silicates and aluminates of crystalline and noncrystalline structures and conditions for establishing durability (strength and constancy of volume) of hydraulically cured products have been elucidated.

It was found that under suitable circumstances nearly all silicate and aluminate crystalline minerals can be decomposed hydrothermally by using lime, yielding stable cement mineral hydrates. Said cement mineral hydrates comprise partly tobermorite i.e. monocalciumsilicatehydrate (CaO . SiO2 . H2O) and tricalciumaluminate-hexahydrate (3 CaO . A12O3 .6 H2O), both forming important components of hardened portland cement.

It is well known that portland cement in a hardened state contains an excess of free lime in the form of calcium oxide, calcium hydroxide and portlandite, as well as lime in the form of the above cement mineral hydrates. In connection with durability of concretes made from the different cements (portland cements, alumina cements and heterogenous cements) it has now been proved that the prerequisite of stability is that the hardened phase of binding material must either contain both of the cement mineral hydrates described before or at least one of them, as well as free lime in a satisfactory quantity, considering that all the cement mineral hydrates can be decomposed by weak acids, even by atmospheric carbon acid, in accordance with the following equation CaO . SiO2 .H2O+CO2=CaCO3+H2SiO3 It will be seen that from tobermorite calcium carbonate and silicic acid are formed under the influence of carbon dioxide, while from the other mineral hydrate described above calcium carbonate and hydrargillite are formed by the following reaction: 3 CaO . A12O3 .6 H2O+3 CO2=3 Cacao3+2 Al(OH)3 Due to such reactions, strength is considerably reduced within the system.

There are a number of other cement mineral hydrates that cannot be considered as independent stable products. Thus for example the mineral hydrate of alumina cement, the monocalciumaluminate-hydrate cannot be considered as stable, and use or production of this material is best avoided.

The deleterious effect of carbonic acid in the atmosphere and of other acidic materials can be avoided only if, in the case of cement mineral hydrates which are otherwise stable, the quantity of free lime present in the concrete is sufficiently high to bind primarily the carbonic acid and other acidic products in the atmosphere in the following known way (illustrated for CO2): Ca(OH)2+CO2=CaCO3+H20 By this reaction the porosity of the concrete - due to the formation of calcium carbonate -- continually decreases, and consequently the penetration of air and carbonic acid into the concrete is gradually reduced.

Besides, not only carbonic acid but other silicate and aluminate components of the concrete or other hydraulic systems are able to abstract the free lime.

Moreover, the chemically reactive SiO2 and Awl203 groups of said minerals are able to abstract calcium oxide from the above cement mineral hydrates and decompose them, when water is present in a sufficient quantity.

In the case of the silicate component, this takes place in accordance with the following schematic reactions, to form calcium polysilicate and calcium polyaluminate hydrates, respectively, of non-crystalline structure and of lower strength, and not showing a constancy of volume (i.e. either expanding or shrinking): Ca(OH)2+(SiO2)n+X . H2O=CaO(SiO2)n . X . H20 calcium-polysilicate-hydrate CaO . SiO2 . H2O+(SiO2)n+X . H2OeCaO(SiO2)n X . H2O 3 CaO . A12O3 .6 H2O+(SiO2) +X. H2OCaO(SiO2) .Z . H2O+ CaO(Al-2O3)nrnY . H20 calcium-polyaluminate-hydrate where n=2-8 and m=2-6 We have now found that substantially all disadvantageous chemical reactions discussed above, occurring in concrete, which adversely influence the stability of the concrete, caused by internal and external circumstances, as well as decomDosition caused by calciumpolyaluminate hydrate and carbon dioxide which produces further detrimental reaction products, can be avoided, by a sufficiency of lime.The lime can be added as a pure binding material or added at least partially in the form of cement, and employed in a quantity sufficient to maintain an internal state of equilibrium in the concrete, i.e. when all chemical reactions between the binding material (lime or cement) and aggregates have already taken place, mainly tobermorite and tricalciumaluminate-hexahydrates should be left together with free lime in the required quantity to avoid degradation by atmospheric CO2 or other environmental acids likely to be encountered.

In order to ensure that sufficient lime is used, we have devised a convenient test which, after less than two days, will accurately predict the long-term behaviour of a hydraulic composition containing a given proportion of lime.

One aspect of our invention provides a process for making a hydraulic composition comprising lime and a basic component which contains at least one of: silica, silicates, alumina and aluminates, said basic component hardening in the presence of lime and water, and said lime and said basic component having a particle size below 100 y or being in such physical and chemical form that they decompose to particles below 100 y on mixing with water, said method including the step of testing a sample of said composition by curing it substantially fully to the level of curing which would be attained after 32 hours at 1000 C, testing said sample for free lime by taking the pH of an aqueous dispersion of said sample, and if the free lime is less than would yield a pH of at least 11.2 in a 5 /n by weight aqueous dispersion of said composition, increasing the proportion of lime in said composition accordingly.

The sample is thus subjected, in effect, to an accelerated ageing procedure.

conveniently this is carried out at 1000C but other temperatures can of course be used provided that the sample is fully cured by the end of the test, i.e. provided that it has reached a level of cure equivalent to 32 hours at 1000C which corresponds to a level of curing at least as great as would be reached after an indefinite period under ambient conditions.

According to our research only a part of the silica and alumina in the silicate aggregate and supplementary binding material reacts with the cement or lime at a normal temperature or below 100"C, while above 100"C, for instance at an autoclave-treatment at 1600C for 6 hours, said materials react chemically with the lime to an increased extent, in dependence on temperature. As a general rule, a certain sequence of reactivity of the minerals is observed. Reactivity is furthermore affected by form, size and specific surface of grains.In general, it can be stated that grains with a diameter under 20 , containing mineral constituents of crystalline structure react with lime relatively readily, but in several cases grains with a diameter of 2060 u are reactive too. Of the crystalline mineral constituents, montmorillonite, feldspars and certain aluminate minerals, e.g. hydrargillite, and b6hmite (bauxite), are especially reactive. According to our findings, aluminium hydroxide reacts in the course of the hydrothermal reaction most rapidly with lime.

Below 100 C quartz does not react with lime or cement, but above 100"C, when subjected to an autoclave treatment, reactivity can be achieved; as a consequence, hydraulic systems formed in accordance with our invention are rich in tricalciumaluminate hexahydrate but also contain tobermorite. In several cases, especially when soils are used as starting materials, the surfaces of some silicate mineral grains are in a disaggregated state showing a non-crystalline structure, and silica and alumina groups contained therein show an increased reactivity. This applies in particular to so-called calciferous, alkaline soils.

One of the essential features of our invention lies in determining the said quantity of lime and/or cement to ensure that requirements relating to stability are achieved with any suitable kind of starting material.

Although in principle the contents of reactive silicic acid and alumina can be calculated, the quantity of the binding material required is preferably determined empirically in a simpler way based on the principles described below.

We want to produce hydrothermally the following cement mineral hydrates: CaO . SiO2 . H2O 3 CaO Al203.6 H2O Ca(OH)2 The pH values of these materials, in a 5% by weight aqueous dispersion, are respectively 11.2-11.2-12.3, while the pH values of the so-called polysilicates and polyaluminates contained in the starting material are, depending to some extent on the degree of polymerisation (values n and m above) - less than 11.2 (e.g. 10.2- 9.2-8.2). It is of utmost importance that pH-value due to the presence of lime reaches in a state of equilibrium at least 11.2, preferably even pH=12.When receiving the pH-values mentioned above, absence of polysilicates and polyaluminates from the system can be assumed and the required quantity of free lime can be assured too. Nevertheless, at normal temperatures a state of equilibrium between the lime and silicate constituents of the starting material is attained, due to the relatively low reaction velocity and depending on the quality of the starting material, only after 1--2 years. Consequently empirical determination is neither practical nor serviceable. The reaction time can be made considerably shorter according to our invention, by a hydrothermal treatment for several hours at an elevated temperature e.g. about 100"C. A period of 32 hours ensures a high degree of certainty in reaching the equilibrium.If materials with hydraulic bond are to be prepared by using an autoclave-treatment, the quantity of free lime should be determined after autoclave treatment has taken place.

According to the invention determination of lime requirement for achieving the stability takes place in small-sized specimens prepared from the starting materials selected as basic components and from lime or from lime and cement in variable quantity, the specimens being subjected to an accelerated cure e.g. by a steam-treatment for 8-16-24 and 32 hours, or in certain cases 40 hours. While the test is in progress strength and pH-values for each cure time are determined.In the case of an insufficient quantity of lime the strength and pH-values after steaming for e.g. 16 hours or more, will be less than those achieved at a steaming time of 8 hours; in case of a suitable quantity of lime, at a steaming period of 32 hours compared to previous values -- strength will increase and reach its maximum, and the pH-value remains above 11.2 at the same time. Specific surface, granular size, chemical and mineral composition all effect starting lime quantities.In case of high specific surfaces calcium oxide should not be less than 5% by weight, while about 33 /" by weight calcium oxide to be added (based on the basic components) is generally a maximal quantity; consequently, recommended variations in quantities of lime (calcium oxide) are as follows: 5-l(wl5 by weight 10--155-20 by weight 20--255-33 by weight Combined use of lime and cement is recommended when in the starting system the contents of silica and alumina reactive with lime is relatively low, as when using coarser dispersed systems (e.g. sand, quartz). In these cases, or if high initial strength is required, it seems to be expedient to use cement in addition to lime as binding material. With starting materials requiring less lime, cement to be added amounts generally to 10--150/, by weight, while with systems hardening well with lime, it amounts to 8-1 2% by weight. Experiments for determining the required quantity of binding materials should be always performed with the entirety of both materials. When performing tests, it is convenient to maintain the quantity of cement always constant, let us say 10% by weight, while the quantity of lime is varied. The lime may be used as slaked lime or quick lime.

The product will be produced with the quantity of binding material determined in the described way and may then be cured at ambient temperature for at least 7 days or converted into a final product by subiecting it to a hydrothermal treatment e.g. at a temperature between 70 and 100"C preferably to steam for 3-8 hours.

The hydrothermal treatment may be carried out by any conventional concrete hydrothermal curing technique.

Taking requirements and potentialities into consideration, often the silicic acid and alumina contents reactive with lime can be supplemented in course of mixing by adding 6-I 5% by weight portland cement.

If the starting material is rich in lime (e.g. calcium carbonate, such as when using marl, calciferous, alkaline or other soils rich in calcium carbonate, or several by-products of industry), the lime content can be formed partly or entirely from the basic component itself by calcining it at a relatively low temperature e.g. 700 850"C.

When using the coarser, dispersed systems such as soils composed of alite and/or sialite, or sedimentary rocks for which the index of plasticity (IP) determined by means of the Casagrande method is 20 or less, these preferably are homogenized with the binding material, lime and cement, similarly to concrete mixing, in a forced mixer (not based on free fall!) e.g. for three minutes in a dry state; after having admixing the required quantity of water, wet mixing may be continued for a further 5 minutes.

Where the index of plasticity (IP) determined by means of the Casagrande method exceeds the value 20 in the coarse dispersed systems used as starting material, homogenization with water and binding materials preferably takes place in a kneading-mixing equipment, preferably in a screw mixer or in a brickmoulding press.

The hydraulic compositions made by using the method described before, can be used e.g. as bulk concrete for road surfacing purposes, for covering slopes of canals, or shaped in a suitable form, as building materials.

Hydraulic systems containing lime only or cement and lime as binding materials, will show high strength, stability, durability and constancy of volume, if binding materials are mixed and homogenized with the aggregates and water in a suitable way. Performance of this operation is of utmost importance, when only lime is used as binding material and specific surface of the starting material is large, i.e. it is rich in grains under 20 y and 2 y. Examples are clays, clayey soils, bauxite and laterite. For suitable and intense homogenization of the binding material(s) and aggregates homogenizing equipment usually used in the ceramic industry as well as any kind of mixer simultaneously exerting a kneading effect can be advantageously used.Such equipment includes brick-moulding presses, which have the advantage that all raw concrete products can be shaped plastically into extrudates whose size does not exceed that of the orifice of the brick-moulding press. When using the shaping process mentioned, mainly when intense homogenization is wanted, preferably two brick-moulding presses are used following each other. The orifice of the first press is provided with a steel plate uniformly perforated with openings of about 2030 mm. From the outlet of this press the raw mixture drops direclty into the next moulding press. For premixing the binding material(s) and starting materials in a dry or semi-dry state, any known mixer can be expediently used.

With coarsely dispersed starting materials (such as sandy, pebbly materials), especially with mixed binding materials, all usual powered concrete mixers and mortar mills can be advantageously used. It is of utmost importance that in the course of mixing and homogenizing neither lime, nor aggregate lumps exceeding 100 y are left in the system. In this way the lime - as a colloidal system -- coats every grain of the aggregate.

According to our research, when carbonate soils are calcined at a relatively low temperature the calcium carbonate is completely transformed into calcium oxide, although this relatively low temperature does not reach the calcining temperature for limestone (850--900"C). We have found that in said starting materials containing natural lime, calcium carbonate is finely distributed and comes from calcium bicarbonate dissolved in water.The lime, having a large surface and being finely distributed is hydrolysed with water partly to milk of lime (calcium hydroxide), whereby the milk of lime tends to destroy certain crystalline silicates in soils in the course of time and forms calcium-polysilicates and calciumpolyaluminate hydrates, which can be considered -- as already mentioned before - precement mineral hydrates. said compositions show a slight hydraulic feature but in order to achieve a high binding capacity and stability, suitable addition of lime (calcium oxide or calcium hydroxide) is imperative. Calcium oxide formed from calcium carbonate in course of calcination serves - in dependence on the quantity - for partial or total supplement of lime.As a consequence, by calcining said material with a lime content at a low temperature, and if necessary adjusting the lime content to a value high enough for stability and by a relatively coarse grinding following calcining cement-like products may be produced, which can be stored and sold in bags and processed to concrete-like products and building materials in a moistened state.

By using the process according to the invention, many industrial by-products, e.g. combustion by-products having a high calcium oxide content, which have been inadequate for the production of stable hydraulic systems with a constancy of volume up to now, for example pulverized fly ash from power plants, slimes formed during refining and burning of crude mineral oils, or rocks containing alite and sialite and poor in lime, as well as corresponding fine-grained silicate rocks and soils, can be transformed to high-strength durable hydraulic systems by adding a binding material and/or by regulating the proportion of lime. For example, blast furnace slag and/or pulverised fly ash having a lime content equivalent to 5--200/, by weight of CaO can be usefully employed.

The invention will now be illustrated in detail by means of some examples; percentages are by weight. All products, except the first sample in Example 1, when fully cured gave a pH of at least 11.2 measured in a 5% by weight aqueous dispersion. Bulk density values relate to the compositions after curing.

Example 1 Production of Blocks From Alkaline Soils Using Quick Lime as Sole Binding Material The soil contains 35 /n fraction < 2 ,u, calcium carbonate content amounts to 10%, index of plasticity (Ip)=30, moisture content=10%.

The quantity of binding material required to achieve stability, was determined as follows: 3x200 g samples of soil (dry weight) were weighed and homogenized one by one with 20 g water and 30, 40 and 60 g respectively of 90% calcium hydroxide (equivalent to 10, 15 and 20% of calcium oxide). After having added further 20 g water to each sample (yielding a good consistency advantageous for shaping), an intensive homogenization was performed; by using cylindrical moulds 4 cm diameter speciments are made - taking 100 g from each mixture - and compacted by hand. The specimens were stored for one day and subjected to a steam treatment in the mould at 1000C for 32 hours. After hardening had taken place and the moulds had been stripped from the specimens, the compressive strength of the specimens made with varying quantities of the binding material is measured.The pH-values due to the lime content in a 5% aqueous dispersion of the pulverized material of the broken specimens are also measured. Strength and pH-values are as followings: Quantity of the binding material added 10 15 20% weight Average compressive strength (kp/cm2) 60 75 83 pH-values 10.2 11.3 12.3 From the above values 20% lime can be considered as the optimal quantity of calcium oxide ensuring stability. Production on industrial scale: As in the production of raw bricks, by using a series of brick-moulding presses, double-sized blocks are prepared by adding calcium hydroxide as binding material corresponding to 20% by weight calcium oxide. The raw bricks are piled in blocks 4.0x4.0x1.5 1.5 m, covered with a polyethylene foil and stored for 10 days at a temperature above freezing point. After having been cured for 10 days, the blocks shaving a compressive strength of 45 kp/cm2 - are transportable and ready for use. At an age of 3 months compressive strength amounts to 80 kp/cm2; bulk density is 1450 kg/m3.

Example 2 Production of Blocks from Alkaline Soils The production takes place as described in Example 1, with the difference that in the last phase instead of storing for 10 days at a temperature above freezing point the blocks are subjected to a steam treatment at 900C for 6 hours.

Compressive strength of the product prepared amounts to 80 kp/cm2, dry bulk density is 1500 kg/m3.

Example 3 Production of Bulk Concrete From Alkaline Soils The process is the same as in Example 1 with the difference that two pressed are used. The bulk material discharged from the second brick-moulding press through the orifice without profile is used as a green concrete hardening hydraulically, for road foundations, or for covering the slopes of channels and other surfaces; the material may be processed by the known mortar and concrete technological methods.

Example 4 Blocks Made of Pulverized Fly Ash Starting material: pulverized fly ash from coal-burning power plants, the ash being acidic with 4% CaO-content; fraction: 75 /n between 60 y and 2 Ju, the remainder: 60 ,u or above. The quantity of lime required: 30% CaO based on the weight of the ash. The process is entirely the same as in Example 1 or 2.

After 28 days the compressive strength of the blocks prepared in accordance with Example 1 amounts to 80 kp/cm2, at the age of 3 months compressive strength reaches 160 kp/cm2.

The compressive strength of the blocks prepared according to the method of Example 2 amounts to 150 kp/cm2 after a steaming period of 6 hours, at the age of 3 months it is 250 kp/cm2, while in both cases dry bulk density amounts to 1550 kg/m3.

Example 5 Production of Bulk Concrete From Pulverized Coal Ash Processing takes place according to Example 4 with the difference that the material discharged from the brick press in a bulk state is used directly for road construction and convering diverse surfaces, using conventional techniques of mortar and concrete technology.

Example 6 Production of Bricks and Blocks From Clay Soils Containing Humus Starting material: loam containing humus; lime-requirement: 15 CaO based on the weight of the loam. Processing takes place according to Example I or 2, giving in each case products with substantially identical physical properties.

The compressive strength of the brick so prepared amounts to 60 kp/cm2 at an age of 28 days, dry bulk density is 1300 kg/cm3. This material can also be used as described in Example 5.

Example 7 Production of Blocks, Bricks and Bulk Concrete, Respectively From Laterite Starting material: West-African Laterite: Lime requirement: 25 /n CaO based on the weight of laterite. The mixture is processed by the methods of Examples 1 or 2.

At the age of 28 days compressive strength amounts to 180 kp/cm2, at the age of' 3 months to 250 kp/cm2. Bulk density: 1250 kg/m2. The composition is usable in accordance with Example 5 as well.

Example 8 Building Elements Made of Laterite The procedure of Example 7 is followed with the difference that the lateritelime elements made in a block-like form are stored in a pile similar to a charcoalpile outdoors, covered with a polyethylene foil or any other foil, and solar heating is used to effect hydrothermal treatment. The blocks are stored under the foil tent for 5 days, at a temperature of approx. 35-550C.

Compressive strength of the product prepared amounts to 180 kp/cm2 at the age of 5 days, dry bulk density is 1800 kg/m3.

Example 9 Building Elements Made of Terra Rossa Starting material: Mediterranean terra rossa; lime requirement: (expressed in CaO): 16% based on the weight of terra rossa. Processing takes place exactly in accordance with Example 7.

At the age of 28 days compressive strength amounts to 100 kg/cm2, dry bulk density to 1650 kg/m3.

Example 10 Block and Bulk Concrete Made of Bauxite Starting material: bauxite with a modulus 4. Lime requirement: 35 /n (CaO) based on the weight of bauxite. Processing takes place exactly according to Example 1 or 2.

At the age of 28 days compressive strength amounts to 120 kp/cm2, dry bulk density to 1650 kg/m3.

Example 11 Bulk Concrete Made of Slimy Quicksand Starting material: slimy quicksand having a clay content of 10 /n; binding material requirement: 10% by weight portland cement and 10% by weight calcium oxide, based on the quicksand. Homogenization takes place in a powered concrete mixer. The composition can serve as bulk concrete for the protection of earthslopes, and allowed to cure in conventional manner.

At the age of 28 days compressive strength amounts to 120 kp/cm2, at the age of 3 months to 160 kp/cm2, dry bulk density to 1800 kg/m3.

Example 12 Bulk Concrete Made of Sandy-Loamy Soils Containing Feldspars Starting material: sandy-loamy soil, with a slight carbonate and a higher feldspar contents. Binding material requirement: 15 /n by weight portland cement and 6% by weight calcium oxide, based on the soil. Homogenization takes place in a powered concrete mixer. The composition can serve as bulk concrete for road surfacing.

At the age of 28 days (natural curing) compressive strength amounts to 135 kp/cm2, at the age of 3 months to 170 kp/cm2, dry bulk density to 1850 kg/m3.

Example 13 Brick Blocks Made of Rhyolite Tuff Starting material: rhyolite tuff. Binding material requirement: 25% by weight CaO based on the tuff. Homogenization takes place in a brick-moulding press, the orifice of which is provided with a perforated sheet. The double-sized hollow bricks are treated by natural curing.

At the age 6f 28 days compressive strength amounts to 100 kp/cm2, dry bulk density to 1100 kg/m3.

Example 14 Pozzolanic Cement Made of Pulverized Fly Ash Starting material: pulverized fly ash (ex power plant). As binding material 40 by weight based on the fly ash of calcium hydroxide (purity 90 /n) is admixed. After having been homogenized in a dry state, the composition is filled into bags and used as pozzolanic cement. The final strength of the product conforms to that of portland cement "300".

Example 15 Pozzolanic Cement Made of Pulverized Fly Ash Starting material: pulverized fly ash rich in CaO.

Processing takes place exactly according to Example 14, except that instead of calcium hydroxide, pulverized fly ash low in calcium oxide is added to the starting material.

For use as concrete and binding material, it is mixed with water using a kneader or mortar mixers.

Quality of the product corresponds to that of the products made with portland cement "300" .

Example 16 Blocks and Mass Concrete Made of Loess Starting material: loess of coarser fraction containing 30 /n clay and mud; lime requirement: 15% CaO based on the loess. Processing is exactly the same as described in Example 1 or 2, and compressive strength may amount to 890 kp/cm2, dry bulk density to 1350 kg/m3.

Example 17 White Cement Made of Alkaline Soils Iron-free, calciferous, alkaline soil is calcined in a rotary furnace at 7500C in such a manner that 90% of the 50% calcium carbonate content is calcined to calcium oxide. When cooled, the loose product is filled into bags without previous grinding. When mixed with water, the part of the binding material containing cement disaggregates spontaneously into particles with a large specific surface; thus grinding is not necessary.

At the age of 28 days compressive strength of the product amounts to 80 kp/cm2, dry bulk density to 1800 kg/m3.

Example 18 Block Made of Alkaline Soils After having granulated the alkaline soil, the granules are calcined at 7500 C.

The product is cooled and ground in a hammer mill to a fraction < 70,u; 8% calcium oxide based on the calcined soil is added; mixing and addition may take simultaneously in an edge runner. The material is processed into blocks by using the technology conventionally used for the production of lime sand bricks.

At the age of 28 days compressive strength amounts to 100 kp/cm2, bulk density to 1400 kg/m3.

Example 19 Building Extrusions Made of Alkaline Soil Process is the same as described in Example 3 with the difference that the soil calcined and ground is mixed with the original soil in a proportion of 1:1 by weight in an edge runner; after having added 14% CaO to the mixture, the material is homogenized in a homogenizing brick press and shaped in the next brick-moulding press into extrusions and hollow blocks.

At an age of 28 days compressive strength amounts to 100 kp/cm2, bulk density to 1250 kg/m3.

Example 20 Bulk Concrete Made of Soils Containing Carbonates Lebanese soil containing 45% calcium carbonate is calcined at 7500C and ground to a fraction < 100 S after having been mixed with water the material is kneaded through a brick-moulding press having a normal orifice and can be used as bulk concrete for road construction.

At the age of 28 days compressive strength amounts to 160 kp/cm2, dry bulk density to 1600 kg/m3.

Example 21 Cement Made of Blast Furnace Slag Granulated blast furnace slag is mixed with 14% calcium hydroxide (based on the slag) and filled into bags. For use as cement, processing takes place by means of a kneader or powered mixer.

Example 22 Blocks Made of Loess-Soil, With Quick Lime as Sole Binding Material The raw material is a quartzy loess soil poor in clay minerals, containing feldspars. Lime quantity required for stability and determined by autoclave test amounts to 25% calcium oxide, although this can be added as the corresponding quantity of calcium hydroxide. For large scale production double-sized blocks can be made as described in Example 1, with the difference that the raw blocks are subjected to an autoclave treatment at 1600C for 6 hours.

The compressive strength of the autoclaved blocks amounts to 160 kp/cm2, bulk density to 1700 kg/m3 and pH-value measured in a 5% dispersion equals 12.

WHAT WE CLAIM IS: 1. A method for making a hydraulic composition comprising lime and a basic component which contains at least one of: silica, silicates, alumina and aluminates,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. described in Example 1 or 2, and compressive strength may amount to 890 kp/cm2, dry bulk density to 1350 kg/m3. Example 17 White Cement Made of Alkaline Soils Iron-free, calciferous, alkaline soil is calcined in a rotary furnace at 7500C in such a manner that 90% of the 50% calcium carbonate content is calcined to calcium oxide. When cooled, the loose product is filled into bags without previous grinding. When mixed with water, the part of the binding material containing cement disaggregates spontaneously into particles with a large specific surface; thus grinding is not necessary. At the age of 28 days compressive strength of the product amounts to 80 kp/cm2, dry bulk density to 1800 kg/m3. Example 18 Block Made of Alkaline Soils After having granulated the alkaline soil, the granules are calcined at 7500 C. The product is cooled and ground in a hammer mill to a fraction < 70,u; 8% calcium oxide based on the calcined soil is added; mixing and addition may take simultaneously in an edge runner. The material is processed into blocks by using the technology conventionally used for the production of lime sand bricks. At the age of 28 days compressive strength amounts to 100 kp/cm2, bulk density to 1400 kg/m3. Example 19 Building Extrusions Made of Alkaline Soil Process is the same as described in Example 3 with the difference that the soil calcined and ground is mixed with the original soil in a proportion of 1:1 by weight in an edge runner; after having added 14% CaO to the mixture, the material is homogenized in a homogenizing brick press and shaped in the next brick-moulding press into extrusions and hollow blocks. At an age of 28 days compressive strength amounts to 100 kp/cm2, bulk density to 1250 kg/m3. Example 20 Bulk Concrete Made of Soils Containing Carbonates Lebanese soil containing 45% calcium carbonate is calcined at 7500C and ground to a fraction < 100 S after having been mixed with water the material is kneaded through a brick-moulding press having a normal orifice and can be used as bulk concrete for road construction. At the age of 28 days compressive strength amounts to 160 kp/cm2, dry bulk density to 1600 kg/m3. Example 21 Cement Made of Blast Furnace Slag Granulated blast furnace slag is mixed with 14% calcium hydroxide (based on the slag) and filled into bags. For use as cement, processing takes place by means of a kneader or powered mixer. Example 22 Blocks Made of Loess-Soil, With Quick Lime as Sole Binding Material The raw material is a quartzy loess soil poor in clay minerals, containing feldspars. Lime quantity required for stability and determined by autoclave test amounts to 25% calcium oxide, although this can be added as the corresponding quantity of calcium hydroxide. For large scale production double-sized blocks can be made as described in Example 1, with the difference that the raw blocks are subjected to an autoclave treatment at 1600C for 6 hours. The compressive strength of the autoclaved blocks amounts to 160 kp/cm2, bulk density to 1700 kg/m3 and pH-value measured in a 5% dispersion equals 12. WHAT WE CLAIM IS:

1. A method for making a hydraulic composition comprising lime and a basic component which contains at least one of: silica, silicates, alumina and aluminates,

said basic component hardening in the presence of lime and water, and said lime and said basic component having a particle size below 100 u or being in such physical and chemical form that they decompose to particles below 100 M on mixing with water, said method including the step of testing a sample of said composition by curing it substantially fully to the level of curing which would be attained after 32 hours at 1000C, testing said sample for free lime by taking the pH of an aqueous dispersion of said sample, and if the free lime is less than would yield a pH of at least 11.2 in a 5% by weight aqueous dispersion of said composition, increasing the proportion of lime in said composition accordingly.

2. A method for producing compositions with hydraulic bonds having a compressive strength of over 60 kp/m3 and having substantially a permanent constancy of volume and of strength, the method including mixing and homogenising a basic component with water and binding material(s) and subsequent curing at an ambient or elevated temperature characterised in that a basic component which contains at least one of: silica, silicates, alumina and aluminates, said basic component hardening in the presence of lime and water, and having a particle size below 100 y or being in such physical and chemical form that it decomposes to particles below 100 CL on mixing with water, adding lime having a particle size below 100 as binding material to said basic component in an amount of from 5 to 33% by weight -- related to the basic component and expressed as calcium oxide - and testing a sample of said composition by curing it substantially fully to the level of curing which would be attained after 32 hours at 100"C, testing said sample for free lime by taking the pH of an aqueous dispersion of said sample, and if the free lime is less that would yield a pH of at least 11.2 in a 5% by weight aqueous dispersion of said composition, increasing the proportion of lime in said composition accordingly, quantities of materials being selected corresponding to the composition of the specimens showing the desired compressive strength.

3. A method as claimed in Claim 1 or 2, wherein the lime added as binding material is slaked lime or quicklime.

4. A method as claimed in Claim 1 or 2, wherein the lime in said hydraulic composition has been prepared partly or entirely by calcining the basic component at a temperature between 700 and 850"C.

5. A method as claimed in any of Claims 1 to 3, wherein the lime is replaced partly or entirely with cement in an amount ranging up to 15% by weight of the basic component.

6. A method as claimed in any of the Claims 1 to 3 or 5, wherein said basic component comprises alite and/or sialite.

7. A method as claimed in any of Claims 1 to 3 or 5, wherein said basic component comprises blast furnace slag and/or pulverised fly ash having a lime content equivalent to 5-20% by weight of CaO, and wherein up to 15% by weight based on said basic component of lime and/or portland cement is included in said composition.

8. A method as claimed in any of the preceding claims, wherein said hydraulic composition after curing has a bulk density of between 1200 and 1900 kg/m3 and a compressive strength greater than 60 kp/cm2.

9. A method as claimed in any of Claims 1 or 3-8 including the step of curing said hydraulic composition in the presence of water.

10. A method as claimed in Claim 9, wherein the composition is allowed to cure at ambient temperature or by hydrothermal treatment at 70--1000C.

11. A method as claimed in Claim 10, wherein said hydrothermal treatment comprises steaming for 3-8 hours.

12. A method as claimed in Claim 1, substantially as described herein.

13. A method as claimed in Claim 1, substantially as described herein with reference to the Examples.

14. A method of testing a hydraulic composition as defined in Claim 1 which comprises curing said composition in the presence of water at an elevated temperature, the length of curing being related to the temperature such that a level of curing is reached equivalent to that obtained after 32 hours at 1000C, and testing the pH of an aqueous dispersion of the said composition to determine if the free lime content is less than would yield a pH of at least 11.2 in a 5% by weight aqueous dispersion of said composition.

15. A method as claimed in Claim 14, wherein samples of said hydraulic composition are tested after curing for various times at said elevated temperature to assess their free lime content and compressive strength.

16. A method as claimed in Claim 14 substantially as described herein and as illustrated in the Examples.