I.2. Electrical Energy Storage and Portable Power Sources
Single-use batteries
Electrical energy storage was developed by Alessandro Volta in
the late 1700s, and chemistry has contributed to subsequent
improvements in battery power. The 1890 carbon-zinc dry cell
improved upon the earlier Leclanché ’wet-cell’ design. It was
commercially produced for use in flashlights and it is still in use
today. In 1949, a new alkaline paste for the traditional battery
enhanced lifetime and allowed miniaturization. This alkaline
battery quickly found many uses in portable electronic devices and
cameras. Since then, newer battery models have used silver
oxide, mercuric oxide, or lithium.
Carbon-zinc dry battery
I.2. Electrical Energy Storage and Portable Power Sources
Rechargeable batteries
The 1859 lead-acid rechargeable battery was an
early commercial example of using a controlled
chemical reaction to produce electricity. Improved
upon in 1881 and continuously enhanced since,
the lead-acid battery continues to be the dominant
form of battery used in automobiles and trucks.
The nickel-cadmium rechargeable battery, first
built in 1899, was too expensive to compete
commercially. Modern developments have focused
on lithium. After a failed attempt to use lithium
metal in the 1980s, lithium-ion batteries are now
commonplace, finding applications in cellular
phones and laptop computers.
I.3. Materials for Roadways and Bridges
Concrete
The massive U.S. interstate construction
projects of the 1950s depended heavily on the
strength and longevity of concrete for roads
and bridges. Portland cement, first made in
1824 and patented as reinforced concrete by
the Frenchman Joseph Monier in 1877, slowsets due to a complex chemical reaction in
which the cement paste fills the void between
particulates and any reinforcements. Its
durability and strength depend on careful
control of the cement manufacturing process.
Adding different chemicals to the initial
concrete mixture can reduce shrinkage and
improve corrosion resistance.
I.3. Materials for Roadways and Bridges
Asphalt
Asphalt is a popular road construction
material today because of its cost and
performance advantages. Natural asphalt was
discovered in 1595, but it was not bound with
coal tar and used to pave roadways until
1902. Bitumen, the solid or semi-solid residue
of the refinery process to make gasoline from
petroleum, quickly replaced natural asphalt for
paving roads. Recently, synthetic polymers
have been added to improve performance and
durability. Superpave (an acronym for
Superior Performing Asphalt Pavements) is
the latest technique for making superior
asphalt that can withstand heavy loads and
adverse weather conditions.
I.3. Materials for Roadways and Bridges
Metals and alloys
Steel has become the primary structural material for bridges due
to its light weight, strength, durability, ease of maintenance and
construction, low erection costs, and resistance to natural
disasters such as earthquakes. New high-performance steels
introduced in the 1990s have superior strength and corrosion
resistance. Another technology for protecting steel in bridge
construction is a process known as metalizing in which
aluminum or zinc is sprayed onto a cleaned steel surface to form
a 30-year protective coating.
I.3. Materials for Roadways and Bridges
Maintenance and repair technique
Road infrastructure must be maintained
without significant deterioration in all
types of weather and on a long timescale.
Innovations
in
construction
and
maintenance materials have allowed
longer intervals between the rebuilding of
roads. Sealants for concrete, asphalt,
and steel are important to prolonging
road life. Other chemical and polymeric
material function as binder addictives to
enhance the performance of asphalt
roadways.
For
example,
styrenebutadiene-styrene results in less rutting
and cracking.