Disclosure of Invention
Aiming at the prior art problems, the photosensitive concrete and the preparation method thereof have the advantages that the photosensitive concrete prepared by the method has better compressive strength, freezing resistance, corrosion resistance and lower carbonization depth, and simultaneously has the capability of purifying air and absorbing organic matters such as toluene in the air.
The invention discloses photosensitive concrete which comprises the following components in parts by weight:
50-70 parts of cement, 10-15 parts of fine aggregate, 5-8 parts of coarse aggregate, 3-5 parts of photosensitive material, 1-2 parts of water reducer, 1-3 parts of expanding agent, 0.5-1 part of dispersing agent and 0.3-0.5 part of stabilizer;
wherein the photosensitive material is sodium peroxide and polyacid-based inorganic photosensitizer.
Preferably, the ratio of the polyacid-based inorganic photosensitizer to the sodium peroxide is 1 (3-5) in parts by weight.
Preferably, the polyacid-based inorganic photosensitizer is a Keggin-type polyacid, a Dawson-type polyacid or an Anderson-type polyacid.
The invention also discloses a preparation method of the photosensitive concrete, which comprises the following preparation steps:
S1, preparing a photosensitive functional agent solution, namely adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, adding a multi-acid-base inorganic photosensitive agent, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 30-60 min, adding a dispersing agent, continuously stirring for 10-15 min, obtaining a mixed solution after stirring, transferring the mixed solution into an ultrasonic mixer, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after ultrasonic treatment is finished;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer after the cement, the fine aggregate and the coarse aggregate are completely mixed by low-speed stirring, uniformly mixing the photosensitive functional agent solution by increasing the rotating speed of the mixing stirrer after the photosensitive functional agent solution is added, adding a water reducing agent and an expanding agent, continuously stirring at the original speed, and finally forming photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubbles, controlling the ambient temperature and humidity to perform initial curing, demolding after the initial curing time is finished, performing secondary curing after demolding, and obtaining the photosensitive concrete after the secondary curing.
Preferably, in the step of preparing the solution of the photosensitive functional agent S1, the mass ratio of the sodium peroxide to the deionized water is 1 (15-25).
Preferably, in the step of preparing the solution of the photosensitive functional agent S1, the stirring speed of the reactor is 800-1200 rpm, the ultrasonic frequency of the ultrasonic mixer is 20-50 kHz, and the ultrasonic treatment time is 20-40 min.
Preferably, in the step of S2 photosensitive concrete preparation, the speed of low-speed stirring in the mixing stirrer is 200-400 rpm, the stirring time is 5-10 min, and the rotating speed of the mixing stirrer is increased to 600-1000 rpm after the photosensitive functional solution is added.
Preferably, in the S3 molding curing step, the ambient temperature is 40-50 ℃ during initial curing, the ambient humidity is 80-90%, and the initial curing time is 20-25 h.
Preferably, in the step of S3 molding and curing, the environmental temperature is 20-30 ℃ during secondary curing, the environmental humidity is 60-70%, and the time of secondary curing is 25-30 d.
Compared with the prior art, the invention has the beneficial effects that:
The invention provides a photosensitive concrete, which is prepared from cement, fine aggregate, coarse aggregate, photosensitive material, water reducer, expanding agent, dispersing agent and stabilizing agent, wherein the photosensitive material is added to ensure that the concrete has certain photosensitivity, and under the condition of illumination, the photosensitive material undergoes photocatalytic reaction to decompose harmful substances in the air, so that the indoor air is effectively purified, and the micro environment of a building is improved. Through photocatalysis, the corrosion of the surface of the concrete caused by environmental pollutants (such as acid rainwater, chloride and the like) can be reduced, so that the corrosion resistance of the concrete is improved, the long-term durability of the concrete is improved, and the concrete can be used for preparing novel wall materials or light building materials.
The invention also provides a preparation method of the photosensitive concrete, when the photosensitive functional agent solution is prepared, after the stabilizer is added, the photosensitive material in the photosensitive functional agent solution is uniformly dispersed by utilizing an ultrasonic mixer, and after the base materials are uniformly mixed, the photosensitive functional agent solution, the water reducer and the expanding agent are added. By optimizing the doping mode of the photosensitive material and the composition of the concrete, the defects of uneven doping amount of the photosensitive material, high porosity of the concrete and easy water absorption are effectively overcome, and the corrosion resistance and the photocatalysis efficiency of the concrete are improved.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1A photosensitive concrete, which comprises the following components in parts by weight:
50 parts of cement, 10 parts of fine aggregate, 5 parts of coarse aggregate, 3 parts of photosensitive material, 1 part of water reducer, 1 part of expanding agent, 0.5 part of dispersing agent and 0.3 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 3:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
The preparation method of the photosensitive functional agent solution comprises the steps of adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:15, the stirring speed of the reactor is 800rpm, adding Keggin type polyacid, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 30min, adding a dispersing agent, continuously stirring for 10min, obtaining a mixed solution after stirring is finished, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 20kHz, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after the ultrasonic treatment is finished, wherein the mass ratio of the sodium peroxide to the deionized water is 1:15;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 200rpm, stirring at a low speed for 5min to completely mix, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 600rpm after the addition is completed, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubbles, controlling the environment temperature to be 40 ℃, controlling the environment humidity to be 80%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 20 ℃, controlling the secondary curing humidity to be 60%, controlling the secondary curing time to be 20d, and obtaining the photosensitive concrete after the secondary curing.
Example 2A photosensitive concrete, which consists of the following components in parts by weight:
55 parts of cement, 11 parts of fine aggregate, 5.5 parts of coarse aggregate, 3.5 parts of photosensitive material, 1.2 parts of water reducer, 1.5 parts of expanding agent, 0.6 part of dispersing agent and 0.35 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 3.5:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
the preparation method of the photosensitive functional agent solution comprises the steps of adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:17, the stirring speed of the reactor is 850rpm, adding Keggin type polyacid, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 40min, adding a dispersing agent, continuously stirring for 11min, obtaining a mixed solution after stirring, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 25kHz, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after the ultrasonic treatment is finished;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 250rpm, stirring at a low speed for 5min to completely mix, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 700rpm after the addition is completed, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2.2h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubbles, controlling the ambient temperature to be 42 ℃, controlling the ambient humidity to be 80%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 22 ℃, controlling the secondary curing humidity to be 60%, controlling the secondary curing time to be 22d, and obtaining the photosensitive concrete after the secondary curing.
Example 3A photosensitive concrete, which consists of the following components in parts by weight:
60 parts of cement, 12 parts of fine aggregate, 6 parts of coarse aggregate, 4 parts of photosensitive material, 1.4 parts of water reducer, 2 parts of expanding agent, 0.7 part of dispersing agent and 0.4 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 4:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
the preparation method of the photosensitive functional agent solution comprises the steps of adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:20, the stirring speed of the reactor is 900rpm, adding Keggin type polyacid, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 50min, adding a dispersing agent, continuously stirring for 12min, obtaining a mixed solution after stirring is finished, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 30kHz, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after ultrasonic treatment is finished, wherein the stirring speed of the reactor is 900rpm;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 300rpm, stirring at a low speed for 7min to completely mix, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 800rpm after the addition is completed, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2.5h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubbles, controlling the ambient temperature to be 45 ℃, controlling the ambient humidity to be 85%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 25 ℃, controlling the secondary curing humidity to be 65%, controlling the secondary curing time to be 25d, and obtaining the photosensitive concrete after the secondary curing.
Example 4A photosensitive concrete, which consists of the following components in parts by weight:
65 parts of cement, 14 parts of fine aggregate, 7 parts of coarse aggregate, 4.5 parts of photosensitive material, 1.7 parts of water reducer, 2.5 parts of expanding agent, 0.85 part of dispersing agent and 0.45 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 4.5:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
The preparation method of the photosensitive functional agent solution comprises the steps of adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:23, the stirring speed of the reactor is 950rpm, adding Keggin type polyacid, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 55min, adding a dispersing agent, continuously stirring for 13min, obtaining a mixed solution after stirring is finished, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 40kHz, starting ultrasonic treatment after adding a stabilizing agent, and the ultrasonic treatment time to be 35min, and obtaining the photosensitive functional agent solution after the ultrasonic treatment is finished;
s2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 350rpm, stirring at a low speed for 8min, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 900rpm after the addition is finished, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2.5h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubble generation, controlling the ambient temperature to be 47 ℃, controlling the ambient humidity to be 85%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 27 ℃, controlling the secondary curing humidity to be 65%, controlling the secondary curing time to be 27d, and obtaining the photosensitive concrete after the secondary curing.
Example 5A photosensitive concrete, which consists of the following components in parts by weight:
70 parts of cement, 15 parts of fine aggregate, 8 parts of coarse aggregate, 5 parts of photosensitive material, 2 parts of water reducer, 3 parts of expanding agent, 1 part of dispersing agent and 0.5 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 5:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
The preparation method of the photosensitive functional agent solution comprises the steps of adding sodium peroxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:25, the stirring speed of the reactor is 1000rpm, adding Keggin type polyacid, stirring and mixing uniformly after the sodium peroxide is completely dissolved, continuously stirring for 60min, adding a dispersing agent, continuously stirring for 15min, obtaining a mixed solution after stirring is finished, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 50kHz, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after ultrasonic treatment is finished, wherein the stirring speed of the reactor is 1000rpm;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 400rpm, stirring at a low speed for 10min, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 1000rpm after the addition is finished, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 3h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubble generation, controlling the environment temperature to be 50 ℃, controlling the environment humidity to be 90%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 30 ℃, controlling the secondary curing humidity to be 70%, controlling the secondary curing time to be 30d, and obtaining the photosensitive concrete after the secondary curing.
Example 6 Keggin type polyacid in the raw materials is changed into Dawson type polyacid, the rest raw materials are the same as example 3, and the preparation method and parameters are the same as example 3.
Example 7 Keggin type polyacid in the raw materials is changed into Anderson type polyacid, the rest raw materials are the same as example 3, and the preparation method and parameters are the same as example 3.
Example 8A photosensitive concrete, which comprises the following components in parts by weight:
60 parts of cement, 12 parts of fine aggregate, 6 parts of coarse aggregate, 4 parts of photosensitive material, 1.4 parts of water reducer, 2 parts of expanding agent, 0.7 part of dispersing agent and 0.4 part of stabilizer. The photosensitive material is sodium peroxide and Keggin type polyacid, and the weight ratio of the sodium peroxide to the Keggin type polyacid is 4:1.
The preparation method of the photosensitive concrete comprises the following preparation steps:
S1, preparing a photosensitive functional agent solution, namely adding sodium peroxide and Keggin type polyacid into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of the sodium peroxide to the deionized water is 1:20, the stirring speed of the reactor is 900rpm, adding a dispersing agent and a stabilizing agent after the sodium peroxide and the Keggin type polyacid are completely dissolved, and continuously stirring for 42min to obtain the photosensitive functional agent solution after stirring is finished;
S2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 300rpm, stirring at a low speed for 7min to completely mix, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 800rpm after the addition is completed, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2.5h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubbles, controlling the ambient temperature to be 45 ℃, controlling the ambient humidity to be 85%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 25 ℃, controlling the secondary curing humidity to be 65%, controlling the secondary curing time to be 25d, and obtaining the photosensitive concrete after the secondary curing.
Example 9A photosensitive concrete, which comprises the following components in parts by weight:
65 parts of cement, 14 parts of fine aggregate, 7 parts of coarse aggregate, 4.5 parts of photosensitive material, 1.7 parts of water reducer, 2.5 parts of expanding agent, 0.85 part of dispersing agent and 0.45 part of stabilizer. Wherein the photosensitive material is titanium dioxide.
The preparation method of the photosensitive concrete comprises the following preparation steps:
S1, preparing a photosensitive functional agent solution, namely adding titanium dioxide into a reactor, adding deionized water, stirring and mixing, wherein the mass ratio of sodium peroxide to deionized water is 1:23, the stirring speed of the reactor is 950rpm, adding a dispersing agent, continuously stirring for 13min after the titanium dioxide is uniformly stirred and mixed, obtaining a mixed solution after stirring is finished, transferring the mixed solution into an ultrasonic mixer, setting the ultrasonic frequency of the ultrasonic mixer to be 40kHz, starting ultrasonic treatment after adding a stabilizing agent, and obtaining the photosensitive functional agent solution after ultrasonic treatment is finished for 35 min;
s2, preparing photosensitive concrete, namely cleaning and airing fine aggregate and coarse aggregate, sequentially adding cement, the fine aggregate and the coarse aggregate into a mixing stirrer, setting the rotating speed of the mixing stirrer to be 350rpm, stirring at a low speed for 8min, slowly adding the photosensitive functional agent solution prepared in the S1 into the mixing stirrer, improving the rotating speed of the mixing stirrer to 900rpm after the addition is finished, uniformly mixing materials in the mixing stirrer, adding a water reducing agent and an expanding agent, and continuously stirring at an original speed for 2.5h to finally form photosensitive concrete slurry;
And S3, molding and curing, namely pouring the photosensitive concrete slurry obtained in the step S2 into a mold, compacting by vibration to prevent bubble generation, controlling the ambient temperature to be 47 ℃, controlling the ambient humidity to be 85%, performing initial curing, demolding after the initial curing is finished, performing secondary curing after demolding, controlling the secondary curing temperature to be 27 ℃, controlling the secondary curing humidity to be 65%, controlling the secondary curing time to be 27d, and obtaining the photosensitive concrete after the secondary curing.
Example 10A concrete, which consists of the following components in parts by weight:
60 parts of cement, 12 parts of fine aggregate, 6 parts of coarse aggregate, 1.4 parts of water reducer, 2 parts of expanding agent, 0.7 part of dispersing agent and 0.4 part of stabilizer.
The preparation method of the concrete comprises the following preparation steps:
(1) The preparation of concrete comprises the steps of firstly cleaning and airing fine aggregate and coarse aggregate, then sequentially adding cement, fine aggregate and coarse aggregate into a mixing stirrer, setting the rotating speed of the mixer to 300rpm, stirring at a low speed for 7min to completely mix, slowly adding a dispersing agent and a stabilizer solution into the mixing stirrer, improving the rotating speed of the mixing stirrer to 800rpm after the addition is completed, uniformly mixing materials in the mixing stirrer, then adding a water reducing agent and an expanding agent, continuously keeping the original speed to stir for 2.5h, and finally forming concrete slurry;
(2) Pouring the photosensitive concrete slurry obtained in the step (1) into a mould, compacting by vibration to prevent bubble generation, controlling the ambient temperature to be 45 ℃, controlling the ambient humidity to be 85%, performing initial curing, demoulding after the initial curing is finished, performing secondary curing after demoulding, controlling the secondary curing temperature to be 25 ℃, controlling the secondary curing humidity to be 65%, controlling the secondary curing time to be 25d, and obtaining the concrete after the secondary curing.
Performance tests were performed on the photosensitive concrete prepared in examples 1 to 9 and the concrete prepared in example 10, and the test results are shown in the following table:
According to the above table, examples 1 to 5 are obtained by screening the parameters in the preparation method, wherein the performances of the obtained photosensitive concrete shown in examples 3 to 4 are optimal, examples 4, examples 6 to 7 and example 9 are obtained by screening the types of photosensitive materials, and according to the data in the above table, the performances of the photosensitive concrete prepared in examples 4 and examples 6 to 7 are better, and the photosensitive concrete prepared in example 9 is low in compressive strength, poor in freezing resistance and corrosion resistance and high in carbonization depth. Examples 4 and 8 are screening of the addition manner and order of the photosensitive materials during the preparation of the photosensitive functional agent solution of the preparation method S1, and it is known from the above table test data that the photosensitive concrete of example 4 has better performance than that of example 9.
And (3) purifying and detecting toluene organic matters in the air for the photosensitive concrete prepared in the examples 1-9 and the concrete prepared in the example 10. The initial toluene content in the ambient air was 5.2mg/m3, and the toluene content in the ambient air was measured after the above concrete was placed in the environment for 1d, 5d and 15d, and the measurement results are shown in the following table:
As shown in the experimental data of the table, the photosensitive concrete prepared by the preparation method provided by the invention has the effect of purifying the environment, wherein the photosensitive material is the best in purifying effect by using the mixture of sodium peroxide and the polyacid-based inorganic photosensitizer.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.