Introduction
Earlier articles on the Society's bridges have discussed the testing of the Woolshed Flat Bridge and the preparation of the Bridge Inventory. This article discusses the construction of the earthenware pipes, rail deck and arch culverts through the Pass and their subsequent history. A subsequent article will discuss the girder bridges.
The period during which the Pichi Richi line was built was one of great change in civil engineering. Two relatively new construction materials, concrete and wrought iron, were coming into general use and engineers were learning new methods of design and construction to produce structures, the like of which had not previously been possible. These new structures could be made larger, more quickly and more economically than ever before, and played their part in making possible the railway boom of the era.
Due to the large number of culverts required on the Port Augusta and Government Gums line and all the many other lines under construction by the South Australian Railways, standardised structures were chosen by the designers to reduce the amount of design work and to facilitate the fabrication and construction.
The development of cement and concrete
Concrete is a building material comprising a mixture of aggregate (usually gravel and sand) and paste of a cementing agent, which is bound into a solid mass as the cement hardens. Precisely measured quantities of aggregate, cement and water are thoroughly mixed and the fresh concrete is placed in moulds or forms where it gradually hardens over a period of time. Cements have a long history, and were originally developed for use as an adhesive mortar to join separate blocks into a whole masonry structure.
The name "concrete" is derived from the Latin "concretus" meaning "growing together" and cement is derived from "caementum", a term used by the Romans to refer to the stone or chips of marble from which a mortar was made. Mortar is derived from the name given by the Greeks to the large container, "mortarium", in which the mortar was ground before use.
Various cementing agents have been used through the ages, such as bitumen, clay and ordinary lime, to produce mortar for bonding masonry together. The ancient Babylonians and Assyrians used clay cements and the ancient Egyptians discovered gypsum and, later, lime cements. Lime cement is produced by burning limestone to drive off the carbon dioxide. After pulverising, the resulting fine‑grained powder is mixed with water (slaked) to form a plastic mix which gradually hardens by re-absorbing carbon dioxide from the atmosphere. The Greeks and the Romans were the first to extensively use lime cements and the Romans particularly produced some very durable cements and mortars. This was due to the thoroughness with which they mixed the mortar and the care with which it was compacted, being pounded by hand rammers. However, the resulting mortars had to be protected from rain and sea as the cements were affected by water.
For use in exposed situations, the Romans and the Greeks both developed a cement capable of withstanding the effects of water. It was noticed that, if finely ground volcanic products were added to the lime, a cement was produced which had "hydraulic" properties, in that it set and hardened under water, unlike ordinary lime, which "slakes" in the presence of water, i.e. absorbs water and crumbles. This is due to a chemical reaction between the ash and the lime in the presence of water which causes the cement to harden. Such cements are described as "pozzolanic". Until the development of modern Portland cement, pozzolanic cement remained the only hydraulic cement.
In mixing the mortar, an inert filler, such as clean, sharp sand, was used to increase the bulk of the mortar and reduce the quantity of expensive cement required. By adding gravel as well as sand, the concept of concrete was developed. Concrete was used by the Romans for pavements, harbour works, sea walls and bridges. At first, the use of concrete by the Romans for bridge works was limited to the infill core of arch bridges where it was poured into external structural masonry. As experience was gained, concrete played a more important role and later Roman bridges used concrete as the structural material with no support from the masonry.
The success of the Roman builders in building permanent concrete structures can be gauged from the many works which have survived until current times. This durability is due to the care with which they selected the best material and the skill exercised in the construction. With the decline of the Roman Empire, the art of good cement and concrete manufacture was lost and for many years lime cements and concretes were the best available. However, concrete continued to be used as a building material, and several castles in England, including Corfe Castle, built in the 12th and 13th centuries, had concrete walls and floors. In the fifteenth century, the writings of the Roman engineer, Vitruvius, were re-discovered and pozzolanic cements were again used. This led to the first known recorded use of concrete for bridge building since the fall of the Roman Empire. This was by the Italian engineer, Giocondo, in the foundations of the Pont Notre Dame in Paris, completed in 1499.
The development of modern hydraulic cements can be said to have begun in 1756, when John Smeaton investigated a wide range of mortars for use in the reconstruction of the Eddystone Lighthouse. The first commercial manufacture of modern cement was long delayed and is generally considered to date from 1824 when Joseph Aspdin patented a process in England for making a cement which he called "Portland cement". The name had been used by Smeaton and was derived from the supposition "that in 12 months it will be as hard as Portland stone", a popular building material at that time. Aspdin had set up a cement plant at Wakefield, near Leeds in England, which was the first to burn a controlled mixture of lime (prepared from a hard limestone) and clay to produce cement.
The earliest known recorded production of Portland cement in South Australia was in 1852, when the Superintending Surveyor of the North East district of the Central Roads Board, Mr Alfred Hardy, produced a specimen made by burning common blue limestone from Anstey's Hill for 60 hours. Unfortunately, no other details are known.
In 1882, South Australia was importing approximately 8000 tonnes of Portland cement each year. William Lewis, a farmer of Brighton, had taken an interest in the geology of the area, particularly its limestone, with a view to producing cement. Following favourable results from experiments, Lewis established a kiln in September, on a site at the top of Brighton Road, and the works were officially opened on 12 December 1882, being the first to commercially produce Portland cement in Australia. However, vigorous competition from overseas products forced him to close his plant in the following year. A Mr Gostling had also briefly opened a cement works in Gawler in October, but his business did not last for very long.
The industry was re-established under the name of the South Australian Portland Cement Co Ltd on 19 March 1892. The company began commercial production of cement and manufactured a range of pre-cast concrete items, such as manhole covers, kerbing stones, window sills, tanks and concrete flagstones. However, the years 1892 and 1893 were a period of economic depression and the company also faced attitudes prejudicial against the quality of colonially manufactured goods. At its own expense, the company arranged for comparative testing of two imported cements against its own, and results showed that Brighton cement gave the best performance. This resulted in the company gaining the Government's custom and production increased. However, the Government failed to impose import duty on foreign cement, and the constant lowering of prices by the importers drove the company bankrupt in December 1895. The company was re-formed in January 1896 and was subsequently more successful. The industry in the state flourished and a rival company, Adelaide Cement, was formed in 1913 and commenced operations at Birkenhead. Their product was marketed as Kangaroo Brand. In 1952, the Brighton Company established a new works at Angaston. The two companies remained competitors until their amalgamation in 1971, after which they were known as Adelaide Brighton Cement.
The earliest use of mass concrete in Britain was for a mass concrete footing poured for the West India Docks in London during 1800. This project used a cement produced from a naturally occurring mixture of limestone and clay and marketed from 1796 as Parker's Roman Cement. Concrete was also used in other ways, as, apparently as early as 1816, a bridge of (unreinforced) concrete was built at Souillac, France. In general, concrete was regarded as plastic stone and used in the same way as ordinary masonry.
Early use of concrete in South Australia tended to follow overseas practice in that it was used mainly in foundations where its ability to be moulded in any shape made it ideal to provide a level bedding for masonry on an uneven or massive excavation. One such bridge is the Mayfield Bridge on the Adelaide to Goolwa Road, near Ashbourne, built in 1866. This is a masonry arch of 8 m (24 ft) span built by the contractor, Mr William McNamee of Adelaide. "The foundations of this bridge (the site being an alluvial flat) were difficult and expensive to put in, and are of concrete."
One of the early instances of the use of concrete as a structural material in South Australian bridge building was its use as a trial substitute for masonry in culverts on the Kapunda to North West Bend (Morgan) and Port Wakefield to Kadina railway lines in 1878. It had been found that due to the scarcity and expense of skilled labour, construction of masonry culverts was a large item in the total cost of the railway. Furthermore, quarries producing good stone close to the railway could not always be found. As limestone was plentifully distributed across the state, it was decided to burn it in small kilns near the tracks to produce lime for use in concrete. The resulting culverts of up to 8 ft span were found to cost half of those of masonry and to be structurally sound.
The Pichi Richi rail deck and arch culverts
Due to this success, all the culverts on the next railway, the Port Augusta and Government Gums Railway, commenced in 1878, were built in concrete. The culverts were evidently considered to be somewhat of a novelty at the time of the original construction of the line for they are described in considerable detail in Patterson, "On the Best Methods of Railway Construction for the Development of New Country as Illustrated by the Railway Systems of South Australia", Proc. Inst. Civil Engrs., 14 January 1879.
Two types of culverts with spans between 2 ft 6 ins and 10 ft were built, an open topped type for low embankments, in which timber flitches spanned across mass concrete abutments and an arched type for high embankments. The lime concrete was placed in one foot thick layers between securely braced timber forms and well rammed to ensure full compaction. The forms were left in place for as long as possible to prevent the concrete drying out too quickly and any part left unfinished for a time was covered with wet bags to keep it moist for the next layer. Finally, the faces exposed to the rain were rendered with Portland cement. For the arch culverts, this included the first two feet length of the inside of the barrel. As standard culverts were used, the formwork was re-used many times and only unskilled labour was required to place the forms and pour the concrete. The arches of the 10 ft span arch culverts were cast in concrete mixed from Portland cement, this being several years before its manufacture in Australia.
At several locations during the construction of the line, good stone for the abutments of bridges was unobtainable, so unreinforced lime concrete was also substituted in the abutments of girder bridges of less than 12 ft in height. Suitable stone for abutments and walls was found close to the line for all bridges between Port Augusta and Quorn, but none could be found further up the railway. The two bridges north of Quorn over the Pinkerton and Cudnowie (now Stony) Creeks have abutments in lime concrete. The remains of the lime kilns used to burn lime can be seen just over the fence on the west of curve 5.
The arch style of concrete culvert in particular, was used extensively, both in railway and road building. For example, the railway through the hills built in 1883 used the same design, and details of unreinforced arch concrete culverts were still being given in a text book on road engineering in 1927. The use of reinforcing in small span openings was considered to be of doubtful utility.
The arch culverts on the Pichi Richi Railway have lasted well. One or two have required repair over the last century, but nearly all remain in excellent condition. Even the pattern of the grain in the timber used for formwork can still be seen in many of the culverts. When the track was re-aligned in several places in 1888, seven arch culverts were widened by constructing a new section to extend their width.
The rail deck or open topped culverts were a replacement superstructure. They were originally built with twin timber girders, and were replaced from about 1887 onwards with the introduction of the heavier (than the original W class) Y class locos. The design appears to have been first used by Mr A.B. Moncrieff, who was Resident Engineer on the Port Augusta & Government Gums Railway between 1879 and 1888, when he was appointed Engineer-in-Chief. Sometime during 1887 he replaced a 10 ft culvert and also a multi-span flood opening and measured the deflection under an "American Engine" travelling at 14 mph on 31 August. The design was found to be successful and was also a good way to re-use old rails, so it was adopted throughout the South Australian Railways after September 1887. Old 40 lb rails were placed edge to edge with the bottom flange down to form a ballast trough of about 8 in depth and 8 ft width. Five or six reversed rails were used inside the trough under each running rail for extra stiffness. The two rail deck culverts just below the Summit Crossing were tested under load in the 1890s.
Subsequent developments in concrete
Two decades after the construction of the Pichi Richi culverts, another advance in the use of concrete was made. The first steps towards reinforced concrete had been taken in 1808, but it was not until the turn of the century that methods of analysis were developed, and subsequently many new structures in this material were built. Australia did not lag far behind the rest of the world in introducing reinforced concrete to bridge building. The first concrete girder and slab bridge in Australia, and one of the first in the world, was built in 1896 over the Mary River at Lamington in Queensland. In South Australia, the first reinforced concrete bridge was constructed in 1906 at Watson's Gap on the railway between Port Elliot and Victor Harbor. This is a 10 m span arch and may actually be unreinforced. In the following year, the first reinforced concrete beam and slab bridge was built to carry the same railway over the Hindmarsh River at Victor Harbor.
One of the people who played a significant role in the development of concrete early this century was the Frenchman, Eugene Freysinnet. Until 1917 the method of compacting had been by pounding the concrete by hand, a labour‑intensive method unchanged since the time of the Romans. In that year, Freysinnet introduced vibration (during the construction of an airship hanger at Orly airport) as a more economical method, using at first an external vibrator. Later, immersion vibrators were developed. The pace of developments has continued to this day, and now concrete is the main structural material.
The earthenware pipes
By way of contrast, earthenware pipes have been used for many thousands of years and earthenware is one of the oldest materials used by man. It is formed from clay, a substance found in abundance in most parts of the world. Clay, free from all organic matter, is dug from the earth's surface and prepared by beating and kneading and picking out the stones and hard lumps. While still damp, the plastic clay is moulded to shape and then fired to a high temperature. This results in a transformation of its properties from the plastic state to a material which is hard and durable. By applying a glaze, the surface of the earthenware can be made impervious and resistant to attack from almost anything. The pipes were made in diameters from 4 inches up to 42 inches and in short lengths of three or four feet with a socket at one end to receive the next length.
The earthenware pipes on the Pichi Richi Railway are mostly still functioning as designed, unnoticed by most who travel along the track. They play an extremely important role, a larger role than their small size would indicate, in draining water from one side of the track to the other. Some have blocked, causing settlement in the formation, and others have broken under the weight of embankment and trains, but still have an opening to carry water under the track.
Whereas concrete has been developed into a major structural material, earthenware has disappeared from the modern engineering construction, replaced in the 1960s by a new plastic known as polyvinyl chloride (PVC).
References
H.J. Hopkins, A Span of Bridges, Praeger Publishers, New York, 1970.
R.C. Patterson, On the best methods of Railway Construction for the development of New Countries, as illustrated by the Railway Systems of South Australia, minutes of proceedings of the Institution of Civil Engineers, London, paper presented on 14 January 1879.
D.W. Penn, How Firm the Foundation: A Historical Survey of an Independent Venture that Founded the Portland Cement Industry in Australia, Concrete Publishing Co Ltd., Adelaide, 1977.
This article by Bill Stacy was published in Pichi Richi Patter Volume 12, No. 2, Summer 1984-85.