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Precast Concrete Stackable Interlocking Retaining Wall Block Product Information
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Precast Concrete Retaining Wall Installation
Here in the North Eastern United States where land is at a premium and hilly or mountainous landscapes sometimes render land unusable, precast concrete retaining walls play an important role in regaining the use of otherwise worthless property.
Our precast concrete stackable, mortar less, retaining wall product / system offers the ultimate in design flexibility and quick placement. With its unrivaled strength and natural stone appearance, the uses are simply limitless. Call today for a free cost analysis and estimate. We will be glad to assist you in taking your precast concrete retaining wall project from design to completion.
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Mixtures of Precast Concrete
General Requirements - Concrete used in precast concrete retaining wall construction should be strong, of uniform quality, free from voids, and thoroughly sound. These qualities are required even more in massive precast concrete retaining walls, as the sections in precast concrete structures are comparatively small and the stability of a given precast concrete structure depends upon the strength and durability of every part of the concrete retaining wall.
The proportions commonly used in American practice vary from about 1:1 1/2:3 to 1:3:6, using either crushed stone or gravel. The rich concrete mixture is usually required in structural walls subjected to high stresses or where exceptional water tightness is also desired. On the other hand, the use of a 1:3:6 concrete requires careful grading of the materials to produce satisfactory results, even for ordinary work.
PRECAST CONCRETE RETAINING WALL CONSTRUCTION
Cement - The cement employed in precast concrete retaining walls should be of high grade; only Portland cement should be used, and the brand selected should conform to the specifications of the American Society for Testing Materials - for these specifications are now accepted as the American standard for precast concrete retaining wall construction.
Sand - The sand employed in the creation of precast concrete retaining walls should be free from clay, vegetable loam, sticks, and organic matter and should be a hard, dense, tough material. Siliceous quartz sands are the best, although sands from any durable rock will answer.
Sharp sand was formally a requirement in all important precast concrete retaining wall construction, but this property is by no means essential. To be sure, by the use of sharp sand there is a slight tendency toward a precast concrete of greater crushing strength than when sand of rounded grains is employed, but this influence on the result is of less importance than the size of grain, or granular-metric composition. Moreover, the sharper the sand employed-the relative sizes of the grains remaining the same-the greater the percentage of voids, and consequently the greater the amount of cement required to produce a given density. (The term density is here used to express the ratio of the volume of the solid particles to the total volume of the precast concrete.) It is now generally conceded that the requirement of sharpness of sand should be omitted from precast concrete specifications.
Precast Concrete Products
Tests of concrete mortar and precast concrete show that: strength and water-tightness increase with density, and so the best sand as to size is one which will produce the smallest volume of concrete of standard consistency when mixed with the given cement in the required proportions. To put it somewhat differently, - the best sand for strength, for water-tightness, and also for economy is one which is so graded from fine to coarse that the percentage of voids in the resulting precast concrete is reduced to a minimum. Such sand has a very coarse appearance as the amount of fine material required is small.
Retaining Wall / Concrete Walls
It has been found that the densest mixture of concrete occurs with particles of different sizes and also that the least density concrete occurs when the grains are all of the same size. Coarse and fine sands are thus inferior to graded sands for precast concrete, but of the two extremes the coarse sand is preferable. The reason for this is due to the fact that the coarse sand has a less total grain surface in a unit volume, even when the sands considered contain portion of solid matter and voids. Less total grain surface means less cement and water to coat the grains, and less labor required in mixing. The additional amount of cement and water required in the case of the fine sand reduces the density of the resulting concrete and likewise its strength. (The density of neat concrete ranges between 0.49 and 0.59, while the density of a sand mortar ranges from 0.60 for fine sand to 0.75 for coarse sand or well-graded sand.)
A fine sand is one containing more than 30 percent of particles that will pass a No. 40 sieve (diameter of hole =0.015 in.).
Stackable / Interlocking
The finer the sand, the more nearly uniform the size of the grains, and consequently the greater the proportion of voids in the precast concrete retaining walls. Fine sand is seldom satisfactory and should not be used in precast concrete retaining wall construction unless coarse sand is not otherwise available. Even in such cases, tests of strength should be made with the idea of determining what extra cost may be justified in securing a coarser material.
Stone Wall / Natural Walls
The most accurate method of determining the value of sand with reference to its size is by means of a sieve analysis. This consists of sifting the sand through several different sieves, and then plotting upon a diagram the percentage by weight which is passed (or retained) by each sieve - abscises - representing size and ordinates representing percentage. Note the analyses of three natural sands - fine, medium, and coarse well-graded sand. Uniform grading is indicated by an approach to a straight line. A standard size of sieve is 8 inches in diameter and 2 1/4 inches high. Woven brass wire sieves are employed for openings less than 1/10 inch in diameter; while for larger openings sheet brass is used, having circular openings drilled to the required dimensions. The woven brass wire sieves are given commercial numbers which approximately coincide with the number of meshes to the linear inch. The actual size of hole, however, varies with the gauge of wire used by different manufacturers and every set of sieves must be calibrated separately. A common defect in sieves is the displacing of the wires so that they are not perpendicular to each other; such sieves should be discarded. Sieves are made to fit together in nests, so that when a sample of sand is placed in the upper (or coarsest) sieve and the nest of sieves is thoroughly shaken, the quantity caught on each sieve can be determined at once.
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