67-727: The Tinaroo Dam , officially the Tinaroo Falls Dam , is a major ungated concrete gravity dam with a central ogee spillway across the Barron River located on the Atherton Tableland in Far North Queensland , Australia . The dam's purpose includes irrigation for the Mareeba-Dimbulah Irrigation Scheme, water supply , hydroelectricity generation, and recreation . Completed between 1953 and 1958,
134-411: A calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone ). Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces , and polymer concretes that use polymers as a binder. Concrete
201-433: A French structural and civil engineer . Concrete components or structures are compressed by tendon cables during, or after, their fabrication in order to strengthen them against tensile forces developing when put in service. Freyssinet patented the technique on 2 October 1928. Concrete is an artificial composite material , comprising a matrix of cementitious binder (typically Portland cement paste or asphalt ) and
268-452: A cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely. As stated by Abrams' law , a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump . The hydration of cement involves many concurrent reactions. The process involves polymerization ,
335-400: A concrete component—and become a part of the binder for the aggregate. Fly ash and slag can enhance some properties of concrete such as fresh properties and durability. Alternatively, other materials can also be used as a concrete binder: the most prevalent substitute is asphalt , which is used as the binder in asphalt concrete . Admixtures are added to modify the cure rate or properties of
402-434: A dispersed phase or "filler" of aggregate (typically a rocky material, loose stones, and sand). The binder "glues" the filler together to form a synthetic conglomerate . Many types of concrete are available, determined by the formulations of binders and the types of aggregate used to suit the application of the engineered material. These variables determine strength and density, as well as chemical and thermal resistance of
469-525: A flood event, was placed on the downstream face. James Mulligan was the first European explorer and prospector to visit the tablelands in 1875. The area is now called the Atherton Tablelands after John Atherton who settled at Emerald End Station, at the junction of Emerald Creek and the Barron River. It is reported through popular legend that upon discovering alluvial tin at the headwaters of
536-452: A greater degree of fracture resistance even in seismically active environments. Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al- tobermorite crystals over time. The use of hot mixing and the presence of lime clasts are thought to give the concrete a self-healing ability, where cracks that form become filled with calcite that prevents
603-429: A hard matrix that binds the materials together into a durable stone-like material that has many uses. This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes performed. The hydration process is exothermic , which means ambient temperature plays a significant role in how long it takes concrete to set. Often, additives (such as pozzolans or superplasticizers ) are included in
670-415: A large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in
737-461: A large type of industrial facility called a concrete plant , or often a batch plant. The usual method of placement is casting in formwork , which holds the mix in shape until it has set enough to hold its shape unaided. Concrete plants come in two main types, ready-mix plants and central mix plants. A ready-mix plant blends all of the solid ingredients, while a central mix does the same but adds water. A central-mix plant offers more precise control of
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#1732852477178804-524: A mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish. Walsh River The Walsh River is a river located on the Cape York Peninsula of Far North Queensland , Australia. The headwaters of the river rise in the locality of Watsonville on the Atherton Tableland approximately 9.6 kilometres (6 mi) north of Herberton and then flow in
871-469: A mixture of calcium silicates ( alite , belite ), aluminates and ferrites —compounds, which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminium and iron) and grinding this product (called clinker ) with a source of sulfate (most commonly gypsum ). Cement kilns are extremely large, complex, and inherently dusty industrial installations. Of
938-424: A noxious pest species and must be destroyed and buried if caught. It is illegal to possess, rear, sell or buy tilapia. It is also an offence to release tilapia into Queensland waterways or to use them as bait, live or dead. Concrete Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in
1005-405: A number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted. The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as paste
1072-424: A semi-liquid slurry (paste) that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration . The water reacts with the cement, which bonds the other components together, creating a robust, stone-like material. Other cementitious materials, such as fly ash and slag cement , are sometimes added—either pre-blended with the cement or directly as
1139-493: A simple, fast way of getting a basic idea of the properties of the finished concrete without having to perform testing in advance. Various governing bodies (such as British Standards ) define nominal mix ratios into a number of grades, usually ranging from lower compressive strength to higher compressive strength. The grades usually indicate the 28-day cure strength. Thorough mixing is essential to produce uniform, high-quality concrete. Separate paste mixing has shown that
1206-657: A westerly direction then turning north past Mount Masterton and then veering west again near Tabacum. It crosses and then runs parallel to the Mareeba-Dimbulah Road then under Mount White and past Fumar and Dimbulah and through the Featherstone Range. It then flows to the north west crossing the Burke Developmental Road and eventually discharges into the Mitchell River of which it is a tributary on
1273-511: Is distinct from mortar . Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks , tiles and other masonry units together. Grout is another material associated with concrete and cement. It does not contain coarse aggregates and is usually either pourable or thixotropic , and is used to fill gaps between masonry components or coarse aggregate which has already been put in place. Some methods of concrete manufacture and repair involve pumping grout into
1340-542: Is only 12 because it all has been swept away. Located on the picturesque Atherton Tableland, with the Tinaroo Range and the Danbulla State Forest surrounding it, Lake Tinaroo provides a popular tourist attraction and recreation facility for over 500,000 people a year. With over 200 kilometres (120 mi) of shoreline, Lake Tinaroo offers many bays with smooth water that are protected from the wind. To this end,
1407-470: Is reported to Atherton police and Maritime safety Queensland. There are still large areas of flooded vegetation, including trees and other man-made objects such as telephone poles, which stand around in the waters of the Lake. The degree of exposure varying with the water level. The lake is surrounded by national park , rainforest , pine tree plantations and Australian "bush" . Hiking paths wind in and out of
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#17328524771781474-559: Is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment. Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (pouring, pumping, spreading, tamping, vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration ) and can be modified by adding chemical admixtures, like superplasticizer. Raising
1541-399: Is usually reinforced with materials that are strong in tension, typically steel rebar . The mix design depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure. Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar , and many plasters . It consists of
1608-480: The construction industry , whose demand is ever growing with greater impacts on raw material extraction, waste generation and landfill practices. Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in
1675-747: The Barron River to create a lake approximately 75% the size of Sydney Harbour with a capacity of 438,919 megalitres (15,500.3 × 10 ^ cu ft) of water at 670 metres (2,200 ft) AHD . The surface area of the Lake Tinaroo is 3,500 hectares (8,600 acres) and the catchment area is 545 square kilometres (210 sq mi). The ungated, central ogee spillway is capable of discharging 1,160 cubic metres per second (41,000 cu ft/s). Two 500-millimetre (20 in) radial gates serve as irrigation outlets that yields 205,000 megalitres (7,200 × 10 ^ cu ft) annually. In addition, one 500-millimetre (20 in) core valve serves as an outlet for
1742-457: The Barron River. After the dam was completed in 1958, there was expected to be another few months before the annual rains to do some final earthworks at the base of the dam, and to clear out the final settlements in the area. Unfortunately the rains began earlier than expected and to this day there are still some pieces of large construction equipment under water at the base of the dam wall, because they were not able to be removed in time. In 2011
1809-570: The Queensland government approved construction at the dam on the Atherton tablelands in Far North Queensland. It took six years to build costing them 12 million dollars . The dam supplied so much water for the 1000 people that worked there. The dam was 44.5 metres tall. The supply level was 670 metres, and the length of storage was 15 kilometres long. There would have been 100 houses but now there
1876-639: The absence of reinforcement, its tensile strength was far lower than modern reinforced concrete , and its mode of application also differed: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble . Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon
1943-498: The atmosphere each year. The dam is used to regulate the waterflow for use at the Barron Gorge Power Station , located 81 kilometres (50 mi) downstream from the dam wall. The townships of Tinaroo , Walkamin , Mareeba , Kuranda , and Yungaburra are supplied from Tinaroo Dam through the Barron River. The townships of Mutchilba and Dimbulah are also supplied by means of the irrigation channel system. In 1952
2010-610: The cisterns secret as these enabled the Nabataeans to thrive in the desert. Some of these structures survive to this day. In the Ancient Egyptian and later Roman eras, builders discovered that adding volcanic ash to lime allowed the mix to set underwater. They discovered the pozzolanic reaction . The Romans used concrete extensively from 300 BC to AD 476. During the Roman Empire, Roman concrete (or opus caementicium )
2077-526: The concrete at the time of batching/mixing. (See § Production below.) The common types of admixtures are as follows: Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures), or as a replacement for Portland cement (blended cements). Products which incorporate limestone , fly ash , blast furnace slag , and other useful materials with pozzolanic properties into
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2144-399: The concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches. Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect
2211-461: The concrete quality. Central mix plants must be close to the work site where the concrete will be used, since hydration begins at the plant. A concrete plant consists of large hoppers for storage of various ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense
2278-519: The crack from spreading. The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon . After the Roman Empire, the use of burned lime and pozzolana
2345-594: The creek, Atherton shouted " Tin, Harroo!! " to his prospecting mate. In 1952, the Tinaroo Dam and Mareeba-Dimbulah Irrigation Scheme was approved by the Queensland Government . Construction on the dam was started in 1953 and completed in 1958, at a cost of A$ 12.666 million. When the dam was filled in 1959, the old township of Kulara near Yungaburra went underwater, and all of the residents relocated to Yungaburra and surrounding towns. The area around Kulara
2412-433: The dam creates the impounded reservoir , Lake Tinaroo . The dam is located close to Lake Barrine and Lake Eacham ( Yidyam ). The dam wall, constructed with 223,000 thousand cubic metres (7,900 × 10 ^ cu ft) of concrete, is 42 metres (138 ft) high and 533 metres (1,749 ft) long. The maximum water depth is 41.8 metres (137 ft) and at 100% capacity the dam wall impounds enough water from
2479-443: The dam's owner, SunWater , completed improvements that included work on both the main dam wall and the saddle dam. The main dam wall was reinforced with the insertion of steel cable anchors within the wall and the addition of a concrete protection slab along the downstream base of the dam wall. The height of the saddle dam was increased by 30 centimetres (12 in) and filters zones, designed to minimise damage caused by seepage during
2546-472: The extensive network of 176 kilometres (109 mi) of channels using either a gravity fed system or pumps. Areas not serviced by the channels can draw water from streams that have their water replenished by the Barron River, which, in turn, is fed by the lake. The Tinaroo Hydro Power Station became operational in 2004. It generates 1.6 megawatts (2,100 hp), thereby reducing 8,450 tonnes (8,320 long tons; 9,310 short tons) of carbon dioxide from entering
2613-431: The finished product. Construction aggregates consist of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone , or granite , along with finer materials such as sand . Cement paste, most commonly made of Portland cement , is the most prevalent kind of concrete binder. For cementitious binders, water is mixed with the dry cement powder and aggregate, which produces
2680-669: The gaps to make up a solid mass in situ . The word concrete comes from the Latin word " concretus " (meaning compact or condensed), the perfect passive participle of " concrescere ", from " con -" (together) and " crescere " (to grow). Concrete floors were found in the royal palace of Tiryns , Greece, which dates roughly to 1400 to 1200 BC. Lime mortars were used in Greece, such as in Crete and Cyprus, in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete . Concrete
2747-554: The interlinking of the silicates and aluminate components as well as their bonding to sand and gravel particles to form a solid mass. One illustrative conversion is the hydration of tricalcium silicate: The hydration (curing) of cement is irreversible. Fine and coarse aggregates make up the bulk of a concrete mixture. Sand , natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while
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2814-509: The lake is often used for sailing , water skiing , houseboating and swimming . During the drought of the last few years, some of the trees that were flooded during the dam's creation have become a hazard to boats because of the receding waters. Sunwater, the owners of the dam do not cut down trees due to safety hazards. Cutting trees at water level creates less visible submerged stumps as well as underwater obstructions which can float to areas that have been mapped as clear. Illegal tree clearing
2881-628: The lake, went underwater. Most of these residents relocated to the tablelands area as their farms were resumed. Covering almost 1,200 square kilometres (460 sq mi), the Mareeba-Dimbulah Irrigation Area is spread across the valleys of the Barron, Walsh and Mitchell Rivers. Some 415 square kilometres (160 sq mi) of farmland are irrigated by the lake when it supplies its 205,000 megalitres (7,200 × 10 ^ cu ft) of water each year. Farmers access this water from
2948-406: The making of mortar. In an English translation from 1397, it reads "lyme ... is a stone brent; by medlynge thereof with sonde and water sement is made". From the 14th century, the quality of mortar was again excellent, but only from the 17th century was pozzolana commonly added. The Canal du Midi was built using concrete in 1670. Perhaps the greatest step forward in the modern use of concrete
3015-531: The material. Mineral admixtures use recycled materials as concrete ingredients. Conspicuous materials include fly ash , a by-product of coal-fired power plants ; ground granulated blast furnace slag , a by-product of steelmaking ; and silica fume , a by-product of industrial electric arc furnaces . Structures employing Portland cement concrete usually include steel reinforcement because this type of concrete can be formulated with high compressive strength , but always has lower tensile strength . Therefore, it
3082-419: The mix, are being tested and used. These developments are ever growing in relevance to minimize the impacts caused by cement use, notorious for being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions . The use of alternative materials also is capable of lowering costs, improving concrete properties, and recycling wastes, the latest being relevant for circular economy aspects of
3149-478: The mixed concrete, often to a concrete mixer truck. Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms. The forms are containers that define the desired shape. Concrete formwork can be prepared in several ways, such as slip forming and steel plate construction . Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture precast concrete products. Interruption in pouring
3216-441: The mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete. The paste is generally mixed in a high-speed , shear-type mixer at a w/c (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers , pigments , or silica fume . The premixed paste
3283-441: The mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. Most concrete is poured with reinforcing materials (such as steel rebar ) embedded to provide tensile strength , yielding reinforced concrete . In the past, lime -based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements , (water resistant) such as
3350-487: The mountains surrounding the lake and range from a pleasant walk from the parking lot to the water-front, to week-long treks around the lake and its mountains. Many species of fish and other aquatic animals populate the lake. The barramundi can grow to an enormous size in the lake because they have no natural predators. Each year, the lake is stocked with young barramundi from the Walkamin Research Station as
3417-506: The properties or increase the performance envelope of the mix. Design-mix concrete can have very broad specifications that cannot be met with more basic nominal mixes, but the involvement of the engineer often increases the cost of the concrete mix. Concrete mixes are primarily divided into nominal mix, standard mix and design mix. Nominal mix ratios are given in volume of Cement : Sand : Aggregate {\displaystyle {\text{Cement : Sand : Aggregate}}} . Nominal mixes are
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#17328524771783484-468: The quality and nature of the product. Design mix ratios are decided by an engineer after analyzing the properties of the specific ingredients being used. Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate (the second example from above), a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune
3551-473: The species is unable to breed in the lake due to the lack of access to salt water . Also present in Lake Tinaroo are eel-tailed catfish , sooty grunter, sleepy cod , mouth almighty, archer fish , spangled perch, long tom and many species of crayfish , including the red-claw and yabby . A Stocked Impoundment Permit is required to fish in the dam. Tilapia were illegally introduced into Lake Tinaroo and are now well established. They have been declared
3618-411: The strength of the concrete bonding to resist tension. The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby the crystallization of strätlingite (a specific and complex calcium aluminosilicate hydrate) and the coalescence of this and similar calcium–aluminium-silicate–hydrate cementing binders helped give the concrete
3685-497: The surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers. Admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. Admixtures are defined as additions "made as the concrete mix is being prepared". The most common admixtures are retarders and accelerators. In normal use, admixture dosages are less than 5% by mass of cement and are added to
3752-535: The surfaces of the aggregate together, and is typically the most expensive component. Thus, variation in sizes of the aggregate reduces the cost of concrete. The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete. Redistribution of aggregates after compaction often creates non-homogeneity due to the influence of vibration. This can lead to strength gradients. Decorative stones such as quartzite , small river stones or crushed glass are sometimes added to
3819-655: The various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement . Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels. The five major compounds of calcium silicates and aluminates comprising Portland cement range from 5 to 50% in weight. Combining water with
3886-439: The water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. Changes in gradation can also affect workability of the concrete, although a wide range of gradation can be used for various applications. An undesirable gradation can mean using
3953-439: The world after water , and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. When aggregate is mixed with dry Portland cement and water , the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with the water through a process called concrete hydration that hardens it over several hours to form
4020-515: Was Smeaton's Tower , built by British engineer John Smeaton in Devon , England, between 1756 and 1759. This third Eddystone Lighthouse pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. A method for producing Portland cement was developed in England and patented by Joseph Aspdin in 1824. Aspdin chose the name for its similarity to Portland stone , which
4087-485: Was among the last to flood when the dam filled. However, being on higher ground, the school building was not flooded and became a private residence at 85 Backshall Road (now in Barrine , 17°14′39″S 145°34′59″E / 17.24420°S 145.58306°E / -17.24420; 145.58306 ( Kulara State School (former) ) ). Earlier the area of Danbulla , located on Robson's Creek – which also feeds into
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#17328524771784154-622: Was built largely of concrete, and the Pantheon has the world's largest unreinforced concrete dome. Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches , vaults and domes , it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick. Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (c. 200 kg/cm [20 MPa; 2,800 psi]). However, due to
4221-602: Was greatly reduced. Low kiln temperatures in the burning of lime, lack of pozzolana, and poor mixing all contributed to a decline in the quality of concrete and mortar. From the 11th century, the increased use of stone in church and castle construction led to an increased demand for mortar. Quality began to improve in the 12th century through better grinding and sieving. Medieval lime mortars and concretes were non-hydraulic and were used for binding masonry, "hearting" (binding rubble masonry cores) and foundations. Bartholomaeus Anglicus in his De proprietatibus rerum (1240) describes
4288-448: Was made from quicklime , pozzolana and an aggregate of pumice . Its widespread use in many Roman structures , a key event in the history of architecture termed the Roman architectural revolution , freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension. The Colosseum in Rome
4355-493: Was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC. They discovered the advantages of hydraulic lime , with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble masonry houses, concrete floors, and underground waterproof cisterns . They kept
4422-614: Was quarried on the Isle of Portland in Dorset , England. His son William continued developments into the 1840s, earning him recognition for the development of "modern" Portland cement. Reinforced concrete was invented in 1849 by Joseph Monier . and the first reinforced concrete house was built by François Coignet in 1853. The first concrete reinforced bridge was designed and built by Joseph Monier in 1875. Prestressed concrete and post-tensioned concrete were pioneered by Eugène Freyssinet ,
4489-615: Was used for construction in many ancient structures. Mayan concrete at the ruins of Uxmal (AD 850–925) is referenced in Incidents of Travel in the Yucatán by John L. Stephens . "The roof is flat and had been covered with cement". "The floors were cement, in some places hard, but, by long exposure, broken, and now crumbling under the feet." "But throughout the wall was solid, and consisting of large stones imbedded in mortar, almost as hard as rock." Small-scale production of concrete-like materials
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