Patent Publication Number: US-2007110992-A1

Title: Block

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a block, and more particularly, to a block provided with functions for holding and absorbing water.  
      Japanese Laid-Open Patent Publication No. 2003-41509 describes a prior art example of a block used to pave roads, such as a road boundary block. The block described in this publication uses waste concrete, which is crushed into grains, as an aggregate. The block is manufactured from initial composition obtained by mixing the aggregate with cement. This forms many fine pores (fine gaps), which are continuous with each other, in the block so that the block has a continuous porous structure. To manufacture the block, the initial composition is subjected to a high level of vibration and compression and molded into a predetermined shape. The molded product is then cured for at least twenty-four hours in an atmosphere saturated with steam.  
      With the continuous porous structure in the block manufactured in this manner, a capillary phenomenon occurs in the block when the block is immersed in water. In such a state, the block has a water holding rate of 10 to 15% and a water absorption rate of about 7%. When the block is in a dry surface state (surface is dry but internal portion is saturated with moisture), the heat capacity increases and moisture vaporization is enhanced. As a result, the block produces an effect of lowering the temperature in the environment in which the block is used that continues for about one or two days. The mix rate of the aggregate and the cement of the block is set in a manner such that the block has a flexural strength of approximately 3.2 N/mm 2  so that the block complies with Japanese Architectural Standard Specification (JASS) 7M-101, which specifies the flexural strength as being greater than 3.0 N/mm 2 .  
      In view of global warming prevention, blocks used to pave roads and etc. are required to improve the temperature lowering effect. To improve the temperature lowering effect of the block described in the above publication, a natural aggregate (e.g., mordenite) having a high holding capability needs to be mixed into the initial composition of the block. If such a natural aggregate is used, the holding rate and absorption rate of the block would increase. However, the flexural strength of the block may become less than 3.0 N/mm 2 .  
      The present invention provides a block that improves the holding rate and absorption rate without lowering flexural strength.  
     SUMMARY OF THE INVENTION  
      One aspect of the present invention is a block manufactured from an initial composition produced by mixing an aggregate and cement. The block includes a plurality of fine pores forming a continuous porous structure. The fine pores with a radius of 3.7 to 6500 nm have a fine pore volume of 0.02 to 0.04 ml/g and a specific surface area of 1.3 to 4 m 2 /g when measured by performing mercury intrusion porosimetry. The fine pores of the block resulting in a gap rate of 18 to 28%.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
      The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
       FIG. 1  is a perspective view of a block according to a first embodiment of the present invention;  
       FIG. 2  is a schematic diagram of a block manufacturing apparatus according to the first embodiment;  
       FIG. 3  is a schematic partial cross-sectional view of the block;  
       FIG. 4  is a schematic view showing a vaporization heat temperature test conducted on the block;  
       FIG. 5  is a graph showing the fine pore distribution in a block of example 1;  
       FIG. 6  is a graph showing changes of the vaporization heat temperature in blocks of example 1 and a comparative example; and  
       FIG. 7  is a perspective view showing a block of a modification. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
      A first embodiment of the present invention will now be described with reference to FIGS.  1  to  4 .  
      As shown in  FIG. 1 , a block  10  of the first embodiment is used, for example, to pave a road. The block  10  has a block main body  11 , which is rectangular. As shown in  FIG. 2 , as an aggregate, the block main body  11  uses first sand  12 , second sand  13 , and a ceramic aggregate (artificial ceramic aggregate)  14 . The block main body  11  is manufactured from an initial composition  16  obtained by mixing the sands  12  and  13  and the ceramic aggregate  14  with cement (also referred to as “bulk cement”)  15 . The first sand  12  and the second sand  13  differ from each other in its grain size distribution. The second sand  13  is coarser than the first sand  12 .  
      The sands  12  and  13 , the ceramic aggregate  14 , and the cement  15 , which are used to manufacture the block  10 , will now be described with reference to table 1 shown below.  
               TABLE 1                          Distribution of First Sand, Second Sand,       Ceramic Aggregate, and Cement for Each Grain Size                         Initial Composition                                             Ceramic               First   Second   Aggregate       Grain Size   Sand 12   Sand 13   14   Cement 15                                         Large Grain C   0.1   13.4   83.1   0       Medium Grain B   90.1   85.8   16.9   0       Small Grain A   9.8   0.8   0   100                  
      First sand: Blast-furnace slag, “BFS 1.2” available from Shin Nihon Seitetsu Kabushiki Kaisha, containing 42.80 wt % of calcium oxide, 0.97 wt % of sulfur, 0.01 wt % of sulfur trioxide, and 0.28 wt % of FeO.     Second sand: Cupola slag available from Toyota Jidosha Kabushiki Kaisha, Akechi Factory.     Ceramic Aggregate: Artificial ceramic aggregate, “Ecostar No. 5” available from Kabushiki Kaisha Hoshino Sansho, containing Wustite (FeO), magnesium-iron-aluminum-oxide (MgFeAlO) and amorphous silicate.     Cement: Normal Portland cement available from Ube Mitsubishi Cement Kabushiki Kaisha.    

      Table 1 shows the distribution of the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  for each grain size as a typical example. The sands  12  and  13 , the ceramic aggregate  14 , and the cement  16 , which are used as the initial composition  16  in the preferred embodiment, are formed as grains. More specifically, the grains of the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  are all categorized into small grains A, medium grains B, or large grains C. A small grain A has a grain diameter of less than 0.15 mm. A medium grain B has a grain diameter of 0.15 mm or greater and smaller than 2.5 mm. The large grain C has a grain diameter of 2.5 mm or greater.  
      The grains of the first sand  12  are mostly categorized as medium grains B. More specifically, the first sand  12  contains 9.8 percent by mass of small grains A and 90.1 percent by mass of medium grains B. The first sand  12  further contains 0.1 percent by mass of large grains C.  
      The grains of the second sand  13  are mostly categorized as medium grains B. More specifically, the second sand  13  contains 0.8 percent by mass of small grains A and 85.8 percent by mass of medium grains B. The second sand  13  further contains 13.4 percent by mass of large grains C.  
      The grains of the ceramic aggregate  14  are mostly categorized as large grains C. More specifically, the ceramic aggregate  14  does not contain small grains A and contains 16.9 percent by mass of medium grains B and 83.1 percent by mass of large grains C. The grains of the cement  15  are all categorized as small grains A.  
      A block manufacturing apparatus for manufacturing the block  10  will now be described with reference to  FIG. 2 .  
      As shown in  FIG. 2 , a block manufacturing apparatus  17  includes a plurality of (four in the present embodiment) hoppers  18 ,  19 ,  20 , and  21 , which are arranged horizontally in line. The hopper  18  stores the first sand  12 . The hopper  19  stores the second sand  13 . The hopper  20  stores the ceramic aggregate  14 . The hopper  21  stores the cement  15 . A mixing vessel  22  is arranged below the hopers  18  to  21 . The mixing vessel  22  is supplied with the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  via openings (not shown) formed in the bottom surfaces of the hoppers  18  to  21 . The mixing vessel  22  is also supplied with a predetermined amount of water W from a water tank WT.  
      Blades  23  are arranged in the mixing vessel  22 . The blades  23  rotate when driven by a motor (not shown). This evenly agitates the sands  12  and  13 , the ceramic aggregate  14 , the cement  15 , and the water W. As a result, the initial composition  16  is produced with a slump value of zero (“slump” is an index showing the plasticity of concrete, and a slump value of zero indicates that the fluidity is close to zero).  
      A mold  24  is arranged below the mixing vessel  22 . The initial composition  16  in the mixing vessel  22  is supplied into the mold  24 . The initial composition  16  supplied in the mixing vessel  22  is subjected to vibration to increase the filling rate of the initial composition  16  in the mixing vessel  22 . The initial composition  16  is molded into a rectangular shape by the mold  24  and then removed from the mold  24 . The material is then cured for a long period of time (at least 24 hours) to complete the manufacture of the block  10 . A block  10  manufactured in this manner includes many fine pores (fine gaps)  25  that form a continuous porous structure as shown in  FIG. 3 . The continuous porous structure causes the capillary phenomenon in the block  10 .  
      In the first embodiment, the mix rate of the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  is set in a manner such that the fineness modulus of the initial composition  16  is in a range of 1.8 to 2.35. The fineness modulus is generally an index indicating the coarseness of the grain size of aggregates (the sands  12  and  13  and the ceramic aggregate  14 ). Further, the fineness modulus is a value obtained by dividing the sum of the percentage by weight of grains that remain in sieves, which have a nominal sieve size of 80, 40, 20, 10, 5, 2.5, 1.2, 0.6, 0.3, and 0.15 mm, by one hundred. However, in the first embodiment, the fineness modulus does not indicate the coarseness of only the aggregate grains and indicates the coarseness of all the grains in the initial composition  16  including the grains of the cement  15 .  
      To produce the initial composition  16  having the above fineness modulus (1.8 to 2.35), the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  are mixed, for example, in the manner described below. More specifically, the sands  12  and  13  are mixed in a manner such that the first sand  12  constitutes 58.3 percent by mass of the initial composition  16  and the second sand  13  constitutes 5.6 percent by mass of the initial composition  16 . Further, the ceramic aggregate  14  and the cement  15  are mixed in a manner such that the ceramic aggregate  14  constitutes 14.5 percent by mass of the initial composition  16  and the cement  15  constitutes 19.4 percent by mass of the initial composition  16 .  
      As described above, in the first embodiment, the cement  15 , which has been used in the prior art only as a curing material (also referred to as a “binder”) for curing the initial composition  16 , is in the form of grains like the sands  12  and  13  and the ceramic aggregate  14 , which function as aggregates. The initial composition  16  is formed by mixing the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  in the manner described above, and then mixing 2.2 percent by mass of the water W to produce the initial composition  16 .  
      A block  10  manufactured in this manner has many fine pores  25  that form a continuous porous structure. The gap rate of the block  10  (the rate occupied by air in the block  10 ) is 18 to 28% by volume of the block main body  11 . Further, the block  10  is manufactured so that when measured by performing mercury intrusion porosimetry, the fine pore volume of fine pores  25  in the block  10  having a radius of 3.7 to 6500 nm (37 to 65000 Å) is 0.02 to 0.04 ml/g (e.g., 0.025 ml/g) and the specific surface area of such fine pores  25  is 1.3 to 4 m 2 /g (e.g., 1.7 m 2 /g). When the block  10  of the first embodiment is immersed in water, a capillary phenomenon occurs with the continuous fine pores in a satisfactory manner so that water is optimally absorbed into the block  10 . The fine pores  25  having a radius of 3.7 to 6500 nm in the block  10  hold the water absorbed in the block  10 .  
      The first embodiment has the advantages described below.  
      (1) If the fine pores  25  having a radius of 3.7 to 6500 nm have a specific surface area of 1.3 to 4 m 2 /g and a fine pore volume greater than 0.04 ml/g, the hollow part of the block  10  (the gap rate of the block  10 ) would increase, and the flexural strength of the block  10  may decrease to less than, for example, 3.0 N/mm 2 . If the fine pores  25  having a radius of 3.7 to 6500 nm have a specific surface area of 1.3 to 4 m 2 /g and a fine pore volume of less than 0.02 ml/g, the amount of water entering the fine pores  25  would decrease because of the small fine pore volume. As a result, the water absorption rate of the block  10  may decrease, and the water holding rate of the block  10  may decrease.  
      If the fine pores  25  having a radius of 3.7 to 6500 nm have a specific surface area of 0.02 to 0.04 ml/g and a fine pore volume greater than 4 m 2 /g, the hollow part of the block  10  (the gap rate of the block  10 ) would increase, and flexural strength of the block  10  may decrease to less than, for example, 3.0 N/mm 2 . If the fine pores  25  having a radius of 3.7 to 6500 nm have a fine pore volume of 0.02 to 0.04 ml/g and a specific surface area of less than 1.3 m 2 /g, the amount of water entering the fine pores  25  would decrease because of the small specific surface area. As a result, the water absorption rate of the block  10  may decrease, and the water holding rate of the block  10  may decrease.  
      Further, if the gap rate of the block  10  is less than 18%, the absorption capability of the block  10 , which results from the capillary phenomenon in the block  10 , decreases. This may decrease the water absorption rate of the block  10 . Further, the water holding rate of the block  10  may decrease. If the gap rate of the block  10  is higher than 28%, the hollow part (i.e., the gap rate of the block  10 ) becomes too high. In this case, the flexural strength of the block  10  may become less than, for example, 3.0 N/mm 2 .  
      In the first embodiment, however, the block  10  is formed so that the fine pores  25  having a radius of 3.7 to 6500 nm have a fine pore volume of 0.02 to 0.04 ml/g and a specific surface area of 1.3 to 43.5 m 2 /g so that the block  10  has a gap rate of 18 to 28%. This improves the water holding rate and the water absorption rate of the block  10  without lowering flexural strength of the block  10 .  
      (2) If the fineness modulus of the initial composition  16  is less than 1.8, the rate of the large grains C mixed in the initial composition  16  becomes too small. Thus, the flexural strength of the block  10  may decrease. If the fineness modulus of the initial composition  16  is greater than 2.3, the rate of the large grains C mixed in the initial composition  16  becomes too high. Thus, the grain density in the block  10  may increase. As a result, the absorption rate and the holding rate of the block  10  may decrease compared to the first embodiment. In the first embodiment, the mix rate of the sands  12  and  13 , the ceramic aggregate  14 , and the cement  15  is set so that the fineness modulus of the initial composition  16  is 1.8 to 2.35. This increases flexural strength of the block  10  while maintaining the absorption rate and the holding rate of the block  10 .  
     Second Embodiment  
      A second embodiment of the present invention will now be described. The second embodiment differs from the first embodiment in aggregates of an initial composition. The second embodiment will be described focusing on its differences from the first embodiment. Components in the second embodiment that are the same or like in the first embodiment are given the same reference numerals and will not be described.  
               TABLE 2                          Distribution of First Sand, Second Sand,       Particulate Ceramic, and Cement of Each Grain Size                         Initial Composition                                     First   Second   Particulate           Grain Size   Sand 12   Sand 13   Ceramic 26   Cement 15                                         Large Grain C   0.1   13.4   0   0       Medium grain B   90.1   85.8   88   0       Small Grain A   9.8   0.8   12   100                  
 
      As shown in table 2, a block  10  of the second embodiment uses sands  12  and  13  and particulate ceramic  26  as aggregates. The block  10  is manufactured from an initial composition  16  that is produced by mixing the sands  12  and  13  and the particulate ceramic  26  with cement  15 . The particulate ceramic  26  has an absorption rate of 12% or greater. The particulate ceramic  26  has many fine pores forming a porous structure. The porous structure results in the capillary phenomenon in the particulate ceramic  26 . Thus, the particulate ceramic  26  has a higher water absorption rate than the first sand  12  (with a water absorption rate of substantially 1.69%) and the second sand  13  (with a water absorption rate of substantially 1.9%). More specifically, the particulate ceramic  26  functions as a high water absorption aggregate having a relatively high absorption capability, the second sand  13  functions as a medium-level water absorption aggregate having a medium-level water absorption capability, and the first sand  12  functions as a low water absorption aggregate having a relatively low water absorption capability in the second embodiment.  
      The grains of the particulate ceramic  26  are mostly categorized as medium grains B as shown in table 2. More specifically, the particulate ceramic  26  contains 12 percent of small grains A by mass, and 88 percent of medium grains B by mass. The particulate ceramic  26  used in the present embodiment contains no large grains C.  
      It is preferable that the mix rate of the sands  12  and  13 , the particulate ceramic  26 , and the cement  15  be set in the manner described below to produce the initial composition  16  with substantially the same fineness modulus (1.8 to 2.3) as that in the first embodiment. More specifically, the sands  12  and  13  and the particulate ceramic  26  are mixed so that the first sand  12  constitutes 55.8 percent by mass of the initial composition  16 , the second sand  13  constitutes 5.3 percent by mass of the initial composition  16 , and the particulate ceramic  26  constitutes 14.8 percent by mass of the initial composition  16 . Further, the cement  15  is mixed to constitute 19.6 percent by mass of the initial composition  16 .  
      The sands  12  and  13 , the particulate ceramic  26 , and the cement  15  are mixed so that the mix rate of the grains A to C are as described above. Water W is then mixed to constitute 4.5 percent by mass of the initial composition  16 .  
      The second embodiment has the advantages described below in addition to the advantages of the first embodiment.  
      (3) The initial composition  16  contains the particulate ceramic  26 , which is a high water absorption aggregate. Thus, the block  10  manufactured from the initial composition  16  of the second embodiment has a higher water absorption rate and water holding rate as compared with the block  10  of the first embodiment.  
     EXAMPLES  
      Examples and a comparative example of the above embodiments will now be described.  
     Example 1  
      The sands  12  and  13 , the particulate ceramic  26 , and the cement  15  were mixed in a manner such that the first sand  12  constitutes 55.8 percent by mass of the initial composition  16 , the second sand  13  constitutes 5.3 percent by mass of the initial composition  16 , the particulate ceramic  26  constitutes 14.8 percent by mass of the initial composition  16 , and the cement  15  constitutes 19.6 percent by mass of the initial composition  16 . The water W was then mixed to constitute 4.5 percent by mass of the initial composition  16 . The initial composition  16  was then evenly agitated in the mixing vessel  22 . Afterward, the initial composition  16  was supplied into the mold  24  and cured to complete the manufacture of the block  10 .  
     Example 2  
      The sands  12  and  13  and the ceramic aggregate  14  were mixed in a manner such that the first sand  12  constitutes 58.3 percent by mass of the initial composition  16 , the second sand  13  constitutes 5.6 percent by mass of the initial composition  16 , and the ceramic aggregate  14  constitutes 14.5 percent by mass of the initial composition  16 . Further, the cement  15  was mixed to constitute 19.4 percent by mass of the initial composition  16 . The water W was then mixed to constitute 2.2 percent by mass of the initial composition  16 . The initial composition  16  was then evenly agitated in the mixing vessel  22 . The processes performed thereafter were the same as in example 1.  
     Comparative Example 1  
      The first sand  12  and gravel were used as aggregates. The first sand  12 , the gravel, and the cement  15  were mixed to produce the initial composition  16 , and the block  10  was manufactured from the initial composition  16 . The first sand  12 , the gravel, and the cement  15  were mixed in a manner such that the first sand  12  constitutes 58.1 percent by mass of the initial composition  16 , the gravel constitutes 18.8 percent by mass of the initial composition  16 , and the cement  15  constitutes 16.6 percent by mass of the initial composition  16 . The water W was then mixed to constitute 6.5 percent by mass of the initial composition  16 . The initial composition  16  was then evenly agitated in the mixing vessel  22 . The processes performed thereafter were the same as in example 1.  
      The gravel contains 0.2 percent by mass of small grains A, 1.6 percent by mass of medium grains B, and 98.2 percent by mass of large grains C.  
      When the initial composition  16  is produced by setting the mix rate of the sands  12  and  13 , the ceramic aggregate  14 , the particulate ceramic  26 , and the cement  15  as in examples 1 and 2 and comparative example 1, the mixing rate of the grains A to C in the initial composition  16  is as shown in tables 1, 2, and 3. More specifically, the mixing rate of the grains A is higher in the blocks  10  of examples 1 and 2 than in the block  10  of comparative example 1.  
                               TABLE 3                                           Comparative           Example 1   Example 2   Example 1           (mass %)   (mass %)   (mass %)                                                            Large Grain C   0.8   9.1   27.7           Medium grain B   71.1   62.5   51.1           Small Grain A   23.6   23.3   14.7           Water W   4.5   5.1   6.5                      
 
 [Discussion]
 
      The gap rate, the fineness modulus, the fine pore volume, the specific surface area, the water absorption capability, the water retaining capability, the flexural strength, the temperature lowering effect, and the vaporization heat temperature of the blocks  10  of examples 1 and 2 and comparative example 1 were measured. To measure the gap rate of each block  10 , the total mass of the sands  12  and  13 , the ceramic aggregate  14 , the particulate ceramic  26 , the cement  15 , and the water W was first calculated (estimated) in a process performed before manufacturing the block  10 . Then, the gap rate was detected using the calculated total mass and the mass (weight) of the block  10  measured immediately subsequent to the molding process (before the water contained in the initial composition  16  vaporizes). The calculation result obtained in this way involves not only fine pores  25  that form the continuous porous structure of the block  10  but also fine pores  25  that are not continuous with other fine pores  25  (that is, fine pores that have almost no absorption and holding functions). The gap rate of each block  10  may alternatively be detected after the manufacture of the block  10  based on the mass of the block  10  in a dry surface state (surface is dry but internal portion is saturated with water) and the mass of the block  10  in an absolutely dry state (in which its holding rate is almost zero). The calculation result obtained in this way does not involve the fine pores  25  that are not continuous with other fine pores  25 . However, the measurement methods of the gap rate yield substantially equal measurement results (calculation results).  
      The radius distribution of the fine pores  25  having a radius of 3.7 to 6500 nm (37 to 6500 Å) in the block  10  is measured by performing mercury intrusion porosimetry using a mercury porosimeter (Porosimeter Series 2000 manufactured by Carlo Erba Instruments). The fine pore volume and the specific surface area were calculated based on the measured fine pore radius distribution. The water absorption capability of each block  10  was measured in accordance with the “test methods for density and water absorption rate of coarse aggregates” specified by Japan Industrial Standards (JIS) A1110. The water holding capability of each block  10  was measured by calculating the difference between the mass of the block  10  in a dry surface state and the mass of the block  10  in an absolutely dry state and dividing the difference by the mass of the block  10  in an absolutely dry state. The flexural strength of each block  10  was measured in accordance with the “precast non-reinforced concrete products” specified by JIS A5371. The temperature lowering effect of each block  10  was measured with the block  10  in a surface dry state. The vaporization heat temperature of each block  10  was measured by arranging the block  10  in a water bath  30  storing water. The block  10  was arranged in the bath  30  in a manner such that its lower portion was immersed in water for about 5 mm. The temperature in the vicinity of the top surface of the block  10  was measured.  FIG. 6  shows the vaporization heat temperature of each block  10 .  
                               TABLE 4                                           Comparative           Example 1   Example 2   Example 1                                                            Gap Rate   22.6   22.8   7.3           Fineness Modulus   2.05   2.2   3.2           Fine Pore Volume   0.0375   0.025   0.0245           (ml/g)           Specific Surface   2.54   1.7   2.21           Area (m 2 /g)                      
 
      As shown in table 4 and  FIG. 5 , the gap rate of the blocks  10  of examples 1 and 2 is 18 to 28%, whereas the gap rate of the block  10  of comparative example 1 is 7.3% (&lt;18%). Further, for the blocks  10  of examples 1 and 2, the fine pore volume of the fine pores  25  having a radius of 3.7 to 6500 nm is 0.02 to 0.04 ml/g and the specific surface area of the fine pores  25  having a radius of 3.7 to 6500 nm is 1.3 to 4 m 2 /g. The accumulated fine pore volume on the left vertical axis in  FIG. 5  represents values obtained by adding the fine pore volume of the fine pores  25  in an order starting with fine pores  25  having a larger radius. The accumulated fine pore volume is indicated by the dashed line in  FIG. 5 . Further, the fine pore volume on the right vertical axis in  FIG. 7  is indicated by a bar graph.  
                               TABLE 5                                           Comparative           Example 1   Example 2   Example 1                                                            Water Absorption   13.5   9.1   3.7           Rate (%)           Water Holding   25.1   19.3   7.6           Rate (%)           Temperature   3-4   2-3   0           Lowering Effect           (Number of Days)           Flexural Strength   3.76   6.63   5           (N/mm 2 )                      
 
      As table 5 shows, the blocks  10  of examples 1 and 2 have a higher water absorption rate and a higher water holding rate than the block  10  of comparative example 1. The blocks  10  of examples 1 and 2 have a water absorption rate of 7.5% or greater and a water holding rate of 16% or greater. The temperature lowering effect of the block  10  in comparative example 1 does not last even for one day, whereas the temperature lowering effect the block  10  in example 2 lasts for two or three days, and the temperature lowering effect of the block  10  in example 1 lasts for three to four days.  
      The block  10  of comparative example 1 has a flexural strength that is greater than 3.0 N/mm 2 . However, when, for example, mordenite, which is a natural aggregate having a high holding capability, is mixed in the initial composition  16  of the block  10  in comparative example 1 to improve the absorption rate (to or above 7.5%), the flexural strength of the block  10  manufactured from this initial composition  16  may decrease to or below 3.0 N/mm 2 . The block  10  of example 1 has a flexural strength of at least 3.0 N/mm 2  and has an improved absorption rate (15% or higher) and an improved holding capability (20% or higher) although the block  10  of example 1 is manufactured from the initial composition  16  containing the particulate ceramic  26  as a high water absorption aggregate. Further, the block  10  of example 2 has a fineness modulus of 2.05 or greater but 2.3 or less. As a result, the block  10  of example 1 has a flexural strength that is greater than 5.0 N/mm 2 .  
                                                   TABLE 6                                   0   1   2   3   4   5   6   7                                                                        Ambient Air   29   30   30   34   34   34   33.5   30       Temperature       Asphalt   36   37.5   37   45   46   45   40   35       Example 1   28   31   31   36   36   36   31   28       Comparative   30   34   34   42   44   44   38   34       Example 1                  
 
      As shown in table 6 and  FIG. 6 , the vaporization heat temperature of the block  10  in comparative example 1 increases as the ambient air temperature increases in the same manner as the vaporization heat temperature of asphalt. However, the vaporization heat temperature of the block  10  of example 1 is lower by about 10° C. than the temperature of asphalt. In this respect, the block  10  of example 1 has a better temperature lowering effect than the block  10  of comparative example 1.  
      It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms.  
      In the above embodiments, the mix rate of the sands  12  and  13 , the ceramic aggregate  14 , the particulate ceramic  26 , and the cement  15  may be set in a manner such that the fineness modulus of the initial composition  16  is 2.05 to 2.35. More specifically, when the fineness modulus of the initial composition  16  is 1.8 or greater but less than 2.05, the flexural strength of the block  10  increases to 3.0 N/mm 2  or greater but cannot reach 5.0 N/mm 2 . However, when the mix rate of the sands  12  and  13 , the ceramic aggregate  14 , the particulate ceramic  26 , and the cement  15  is set in a manner such that the fineness modulus of the initial composition  16  is 2.05 or greater, the flexural strength of the block  10  increases to 5.0 N/mm 2  or greater. In this way, the flexural strength of the block  10  is further improved.  
      In the above embodiments, the block  10  may include a water permeable layer  40  having water permeability that is greater than that of the block main body  11 . The water permeable layer  40  is arranged at the surface side of the block main body  11  (the surface side when the block  10  is arranged to pave a road) as shown in  FIG. 7 . In this case, water entering the water permeable layer  40  is readily discharged from the water permeable layer  40 . This prevents the surface of the block  10  from being stained by moss and mold.  
      In the above embodiments, for example, sepiolite may be used as a high water absorption aggregate. It is preferable that the high water absorption aggregate be mixed in the initial composition  16  in a manner such that the block  10  manufactured using such an aggregate has a flexural strength of 3.0 N/mm 2  or higher. Sepiolite is a natural material having a moisture absorption and desorption characteristic.  
      Further, crushed red roof tiles may be used as the high water absorption aggregate.  
      In the above embodiments, crushed ceramics grains, chamotte, glass cullet, incinerated ash, ferronickel slag, and copper slag may be used as aggregates.  
      In the above embodiments, the block  10  may be used as a block used for constructing walls.  
      In the above embodiments, the block  10  may have any shape (e.g., a spherical shape).  
      It is preferable that the high water absorption aggregate have an absorption rate of 12% or higher and include many fine pores that form a continuous porous structure.  
      The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.