1. Field of the Invention
This invention relates to flexible Portland cement polymer concrete and methods for making flexible Portland cement polymer concrete.
2. Description of the Related Art
Conventional concrete is a dense hard hydrated mass produced from mixtures of Portland cement, coarse aggregate, fine aggregate, and water. Concrete mixtures generally use only sufficient water to make the mixture workable for placement and to yield hardened concrete having a compressive strength of at least 8.3 MPa (1200 psi) after 28 days. Portland cement is a well known cement that upon mixing with water binds or unites the other materials present in the mixture into concrete. The Portland cement is typically a Type I, II, III, IV and V Portland cement as defined in ASTM C 150. The coarse aggregate conventionally comprises particles such as gravel, quartzite, granite, limestone, shale, and other minerals having a particle size greater than 9.5 millimeters (0.375 inches). The fine aggregate employed in Portland cement concretes is most often sand comprised of particles less than about 0.375 inches (9.5 millimeters) in size, typically equal to or less than about 0.1875 inches (4.76 millimeters) in size. Typically, fresh concrete has mixing water exceeding the amount needed for hydration for purposes of workability, handling, and finishing.
There are many reasons for the popularity of concrete. It is relatively inexpensive, capable of taking on the shape of a mold, has exceptionally high compression strength and is very durable. However, as a building or construction material, concrete, whether it is reinforced or not, has certain disadvantages. One disadvantage is that concrete has relatively low tensile strength and therefore has little ability to flex without cracking.
A concrete road surface is a good example where concrete, under repeated loads and flexing due to vehicle traffic, eventually degrades, leading to cracks. This illustrates two primary limitations of Portland cement concrete. The first fundamental limitation is a relatively low tensile strength which primarily exhibits itself as cracks in concrete products. This limitation is addressed by adding reinforcement to the concrete typically in the form of steel fibers, steel bars or steel mesh and/or by controlling the cracking through predetermined crack locations. However, concrete structures can require large amounts of reinforcing material, thereby significantly increasing labor and material costs. The second fundamental limitation is that water intrusion into the concrete can cause both physical damage during freezing and thawing and chemical damage by instigating a series of secondary chemical reactions that can cause degradation of the concrete matrix. This type of behavior can cause surface scaling, cracking and crumbling of concrete much earlier than weather and age might be expected to cause similar degradation. Concrete that has a greater tensile strength, and is thereby able to flex more without failing, would result in surfaces and structures that are less susceptible to wear and cracking.
What is needed therefore is a method for making a concrete having greater tensile strength without requiring the addition of reinforcing materials.