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The Greek architekton was usually the designer, as well as the builder, of architectural and engineering masterpieces. He was an architect and engineer. Craftsmen, masons, and sculptors worked under his supervision. In the classical period of Greece all important buildings were built of limestone or marble; the Parthenon, for example, was built of marble.
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The principal construction materials of earlier times were wood and masonry-brick, stone, or tile, and similar materials. The courses or layers£¨×©²ã£©were bound together with mortar or bitumen, a tarlike substance, or some other binding agent. The Greeks and Romans sometimes used iron rods or clamps to strengthen their building. The columns of the Parthenon in Athens£¨ÑŵäµÄÅĄ́ũÉñÃí£©, for example, have holes drilled£¨×ê¿×£© in them for iron bars that have now rusted away£¨ÐâÊ´´ù¾¡£©. The Romans also used a natural cement called pozzolana, made from volcanic ash, that became as hard as stone under water.
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     Both steel and cement, the two most important construction materials of modern times, were introduced£¨Íƹ㣩 in the nineteenth century. Steel, basically an alloy of iron £¨ÌúºÏ½ð£©and a small amount of carbon, had been made up to that time£¨µ½ÄǸöʱºò£© by a  laborious£¨·±¸´µÄ£© process that restricted it to such special uses as sword blades£¨µ¶ÈУ©. After the invention of the Bessemer process £¨±´ÈûÂóÁ¶¸Ö·¨£©in 1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile strength; that is, it does not lose its strength when it is under a calculated degree (Êʵ±µÄ) of  tension, a force which, as we have seen, tends to £¨ÍùÍù£©pull apart many materials. New alloys have further increased the strength of steel and eliminated some of its problems, such as fatigue, which is a tendency for it to weaken as a result of continual changes in stress£¨Á¬ÐøµÄÓ¦Á¦±ä»¯£©.
            ×÷ΪÏÖ´úÁ½ÖÖ×îÖØÒªµÄ½¨Öþ²ÄÁÏ£¬¸Ö²ÄÓëË®ÄàÔÚÊ®¾ÅÊÀ¼ÍµÃµ½ÁËÍƹã¡£Ö±µ½ÄǸöʱºò£¬¸Ö²Ä²Åͨ¹ý·±¸´µÄ¹ý³ÌÖÆÔì³öÀ´£¬»ù±¾ÉÏÊÇÌúºÏ½ð£¬²¢º¬ÓÐÉÙÁ¿µÄ̼£¬Òò¶ø±»ÏÞÖÆÔÚһЩÌØÊâµÄÓÃ;È絶ÈС£ÔÚ1856Äê·¢Ã÷Á˱´ÈûÂóÁ¶¸Ö·¨ºó£¬¸Ö²Ä²ÅµÃÒÔ´óÁ¿µÍ¼Û»ñµÃ¡£¸Ö²Ä¾Þ´óµÄÓÅÊƼ´ÊÇËüµÄ¿¹À­Ç¿¶È£¬Ò²¾ÍÊǵ±ËüÔÚÊʵ±µÄÀ­Á¦Ï²»»áʧȥǿ¶È£¬ÕýÈçÎÒÃÇËù¿´µ½µÄ£¬¸ÃÁ¦ÍùÍùÄܹ»½«ºÜ¶à²ÄÁÏÀ­¿ª¡£ÐµĺϽð½øÒ»²½Ìá¸ßÁ˸ֲĵÄÇ¿¶È£¬²¢Ïû³ýÁËһЩȱµã£¬ÈçÆ£ÀÍ£¬¼´ÔÚÁ¬ÐøµÄÓ¦Á¦±ä»¯Ïµ¼ÖÂÇ¿¶È¼õÈõµÄÇ÷ÊÆ¡£
Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone£¨Ê¯»Òʯ£© and clay, which is heated and then ground into a powder£¨Ä¥³É·ÛÄ©£©. It is mixed at or near the construction site £¨Ê©¹¤ÏÖ³¡£©with sand, aggregate (small stones, crushed  rock, or gravel), and water to make concrete. Different proportions of the ingredients £¨ÅäÁÏ£©produce concrete with different strength and weight. Concrete is very versatile; it can be poured, pumped, or even sprayed into £¨ÅçÉä³É£©all kinds of shapes. And whereas steel has great tensile strength, concrete has great strength under compression. Thus, the two substances complement each other£¨»¥²¹£©.
        ÏÖ´úË®Äà·¢Ã÷ÓÚ1824Ä꣬³ÆΪ²¨ÌØÀ¼Ë®Äà¡£ËüÊÇʯ»ÒʯºÍÕ³ÍÁµÄ»ìºÏÎ¼ÓÈȺóÄ¥³É·ÛÄ©¡£ÔÚ»ò¿¿½üÊ©¹¤ÏÖ³¡£¬½«Ë®ÄàÓëÉ°¡¢¹ÇÁÏ£¨Ð¡Ê¯Í·¡¢Ñ¹ËéµÄÑÒʯ»òÀùʯ£©¡¢Ë®»ìºÏ¶øÖƳɻìÄýÍÁ¡£²»Í¬±ÈÀýµÄÅäÁÏ»áÖÆÔì³ö²»Í¬Ç¿¶ÈºÍÖØÁ¿µÄ»ìÄýÍÁ¡£»ìÄýÍÁµÄÓÃ;ºÜ¶à£¬¿ÉÒÔ½½Öþ¡¢±ÃËÍÉõÖÁÅçÉä³É¸÷ÖÖÐÎ×´¡£»ìÄýÍÁ¾ßÓкܴóµÄ¿¹Ñ¹Ç¿¶È£¬¶ø¸Ö²Ä¾ßÓкܴóµÄ¿¹À­Ç¿¶È¡£ÕâÑù£¬Á½ÖÖ²ÄÁÏ¿ÉÒÔ»¥²¹¡£
         They also complement each other in another way: they have almost the same rate of contraction and expansion. They therefore can work together in situations where£¨ÔÚ…Çé¿öÏ£© both compression and tension are factors£¨Ö÷ÒªÒòËØ£©. Steel rods£¨¸Ö½î£© are embedded in£¨ÂñÈ룩concrete to make reinforced concrete in concrete beams or structures where tension will develop£¨³öÏÖ£©. Concrete and steel also form such a strong bond - the force that unites£¨Õ³ºÏ£© them - that the steel cannot slip£¨»¬ÒÆ£© with the concrete. Still£¨»¹ÓУ© another advantage is that steel does not rust in concrete. Acid£¨Ëᣩ corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid.