JPH0339693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a trace collection method used for collecting various traces in forensic work, investigation work, etc.

[Prior art] For example, gypsum hemihydrate has traditionally been used as a material for collecting traces used for identification purposes such as footprints and tire marks in criminal investigations due to economic efficiency and ease of handling. ing. When you mix gypsum hemihydrate with an appropriate amount of water, it will start out smooth, but if you keep mixing it, it will gradually become more viscous. Then, the plaster paste, which has reached an appropriate softness, is poured onto the surface of the trace to be collected and left to stand until it hardens. Usually, the cured product is carefully removed after 20 minutes or more. The cured product taken out does not have sufficient strength, so when moving it immediately after curing, care must be taken to avoid applying impact, and since the surface strength is low, care must be taken to avoid scratches. Note that in order to improve the peelability when removing the cured material from the mold, it is usual to apply soap solution or spray a silicone or Teflon-based solution to the surface of the specimen before pouring the gypsum paste. It is being done.

[Problems to be solved by the invention] However, according to the conventionally used collection method using gypsum hemihydrate, the following problems are recognized due to the characteristics of gypsum hemihydrate. .

The time required for kneading to obtain a gypsum paste of appropriate softness is greatly affected by the air temperature and the temperature of the kneading water, and varies widely from 3 to 15 minutes. That is,
If it is poured before it reaches the appropriate softness,
It lacks strength after curing, is easily broken, and cannot withstand storage. On the other hand, if it is poured after it has passed the appropriate softness and begins to harden, the hemihydrate gypsum will begin to harden during the pouring process, reducing its fluidity and deforming the traces that should be collected, making it difficult to collect faithful traces. becomes impossible. As described above, it is very difficult to obtain the appropriate softness for pouring, and the trace collection method using gypsum hemihydrate requires sufficient skill.

Usually requires 20 minutes or more to cure. Particularly when the temperature is low, such as during the winter, it may take several hours, making the work extremely time-consuming.

Since strength development after curing is slow, there is a risk of breakage during transfer immediately after demolding.

The hardened material has low strength and is easily scratched.

When collecting semi-solid traces on a smooth surface, the impression surface is also washed away when the plaster paste is poured, making it impossible to obtain an accurate impression.

When taking traces in water, accurate impressions cannot be obtained because the gypsum dissolves in water.

When collecting traces in the snow, the gypsum does not harden due to the low temperature, making it impossible to obtain a hardened material.

In view of the above-mentioned problems, the present invention uses a suitable material instead of plaster as the sampling material to be poured into the trace, thereby improving workability, making it possible to collect clear impressions in a short time, and storing the hardened material for a long period of time. The purpose of this paper is to provide a possible trace collection method.

[Means for solving the problems] The present invention, as a means for realizing the above object,
It is characterized by pouring a cement-based rapid hardening material onto the surface of the trace to be collected to obtain a hardened material. That is, a paste or mortar of a cement-based rapid hardening material is poured onto various marks to obtain a hardened body in which the impression of the marks is transferred.

In general, hardened cement-based materials have higher strength and hardness than hardened gypsum-based materials, and are not soluble in water, so they basically have excellent long-term storage properties. However, regular Portland cement takes a long time to harden, so
It is simply impossible to achieve the objectives of the present invention in terms of working time.

Therefore, the present invention attempts to solve the problems of the prior art by using a cement-based rapid hardening material based on ultra-fast hardening cement that can obtain high strength in a short time.

The cement-based rapid hardening material used in the present invention is
The main component is ultra-fast hardening cement, and if necessary, fly ash, pulverized blast furnace slag powder, silica stone powder, antifoaming agent, fluidizer, and thickener are added.One suitable example is ultra-fast hardening cement. ；50～
100 parts by weight, fly ash: 50 parts by weight or less, antifoaming agent: 2 parts by weight or less, fluidizing agent: 5 parts by weight or less,
Thickener: A mixture consisting of 5 parts by weight or less. Moreover, commercially available ultra-fast hardening cements can be used.

However, this cement-based rapid hardening material has a water content of 30~
Pour 60 parts by weight, mix well to make a paste,
Pour this onto the surface of the object to be sampled and leave it standing until it hardens. The pot life of this paste after pouring water is 30
The duration is from seconds to 10 minutes, preferably from 1 to 5 minutes.
The curing time is preferably 1 to 30 minutes, preferably 2 to 15 minutes after pouring water. The curing time referred to here is
This refers to the time it takes for the cured product to become demoldable, and although it varies slightly depending on the size of the sample, it is the time required to obtain a compressive strength of 50 Kgf/cm ² or more for the cured product. The object to be collected can be easily peeled by applying or spraying a soap solution, oil, oil, silicone liquid, Teflon liquid, etc. to the object in advance.

When it comes to traces in water, cement-based quick-hardening material paste has low dispersibility in water, so the paste can be poured in and collected. in this case,
When the object to be collected is on sand or the like where it easily crumbles, it is best to sprinkle powder of a cement-based rapid hardening material evenly and harden it to reinforce it, and then pour the paste. In this case, apply the powder onto the trace,
For example, it is best to sprinkle it evenly so that it is deposited to a thickness of about 1 mm.

Traces in the snow can also be collected in much the same way as traces in water.

[Function] In the trace collection method of the present invention, water is poured into the cement-based rapid hardening material, and then kneaded into a paste or mortar in the same way as when kneading ordinary cement, which is then poured onto the object to be collected. Because it hardens rapidly after the usage time is over, it can be removed from the mold in about half the time of hemihydrate gypsum.

In addition, pastes made from cement-based rapid hardening materials have greater thixotropy than plaster pastes, so even traces on easily crumbling sand or smooth surfaces will not break or bleed, allowing accurate impressions to be taken of the hardened material. be able to. Moreover, since the collected cured material develops a compressive strength of 100 Kgf/cm ² or more in about 10 minutes, it can withstand handling such as subsequent transportation, and will not be damaged by scrubbing or brush cleaning.

[Effects of the Invention] As understood and confirmed from the above description and the results of the examples listed later, the present invention has the following effects.

In other words, the first advantage is that the work time required to collect the shape of the trace can be reduced to about 10 minutes, which is half that of the conventional method using gypsum hemihydrate.

In addition, since the paste using a cement-based rapid hardening material has a high thixotropy, it is possible to easily collect traces on easily crumbled sand or a smooth surface such as a P tile without causing deformation or smearing.

Furthermore, because the paste spreads little in water, it is also possible to collect three-dimensional footprints underwater.

Furthermore, the collected cured product has high strength in a short period of time, is easy to handle, and has high hardness and is difficult to scratch.

Furthermore, since the cured product exhibits a grayish-white color, it has the advantage that it does not cause halation even when photographed.

In addition, according to the method of first sprinkling cement-based rapid hardening material powder, the powder that does not apply a large external force to the traces is first deposited on the traces to form a layer, and that layer hardens and the traces disappear. Since the paste is introduced after reinforcement, even if the object to be collected is on sand, etc., which is easily crumbled, it is possible to collect the object without disturbing its traces.

[Example] Examples of the present invention will be listed and explained below.

<Example 1> 450g of super fast hardening cement, 50g of fly ash,
A paste made by adding 250 ml of water to a cement-based rapid hardening material containing 0.5 g of antifoaming agent and 4 g of fluidizing agent and kneading for 20 seconds was prepared by spraying powdered extinguishing agent in advance, and then soil (red soil) whose surface was sprayed with silicone spray. ) followed in the footsteps of

In addition, 800 g of plaster was applied to a similar footprint that had been sufficiently sprayed with a mold release agent consisting of 1 part detergent and 3 parts water.
A gypsum paste mixed with appropriate amount of water was poured. The air temperature at this time was 12℃ and the water temperature was 14℃.
It was hot.

The total time required to complete the footprint collection was 13 minutes when cement-based quick-setting material was used, while it was 30 minutes when plaster was used.

Reference photo 1 of footprints collected using each method
(cement method) and reference photo 2 (gypsum method).
According to the results, both impressions were clear.

<Example 2> 450 g of ultra-fast hardening cement, 50 g of blast furnace slag powder,
A paste made by adding 250 ml of water to a cement-based rapid hardening material containing 0.5 g of antifoaming agent and 4 g of fluidizing agent and kneading it for 20 seconds was lightly sprayed with silicone spray in advance, fixed with F spray, and mixed with powder fire extinguisher. A silicone spray was poured onto the sprayed footprints in the sand.

In addition, after lightly spraying a mold release agent consisting of 1 part detergent and 3 parts water in advance, it was fixed with F spray, and 800 g of gypsum was mixed with an appropriate amount of water on the same footprint that had been sufficiently sprayed with the mold release agent. Pour the plaster paste. The air temperature at this time was 12°C and the water temperature was 14°C.

The total time required to complete footprint collection was 11 minutes when cement-based quick-setting material was used and 25 minutes when plaster was used.

Reference photo 3 of footprints collected using each method
(cement method) and reference photo 4 (gypsum method).
According to the results, it can be seen that a clear impression is obtained when the cement-based rapid hardening material according to the present invention is used, compared to the case where the impression is distorted when plaster is used.

<Example 3> A paste made by adding 200 ml of water to 500 g of ultra-fast hardening cement and kneading it for 30 seconds was poured into the footprints on a smooth surface (tile).

Additionally, a plaster paste made by mixing 800g of plaster with an appropriate amount of water was similarly poured onto the footprints. At this time, the air temperature was 12℃ and the water temperature was 14℃.

The total time required to complete footprint collection was 11 minutes when cement-based quick-setting material was used and 25 minutes when plaster was used.

Reference photo 5 of footprints collected using each method
(cement method) and reference photo 6 (gypsum method).
According to the results, when plaster was used, the impression was washed away, whereas when the cement-based rapid hardening material according to the present invention was used, the impression could be taken clearly without being washed away.

<Example 4> 450 g of super fast hardening cement, 50 g of silica powder, antifoaming agent
A paste made by adding 200 ml of water to a cement-based rapid hardening material containing 0.5 g and 4 g of a superplasticizer and kneading the mixture for 20 seconds was poured into a footprint on a smooth surface (P tile).

Additionally, a plaster paste made by mixing 800g of plaster with an appropriate amount of water was similarly poured onto the footprints. At this time, the air temperature was 12℃ and the water temperature was 14℃.

The total time required to complete footprint collection was 11 minutes when cement-based quick-setting material was used and 25 minutes when plaster was used.

Reference photo 7 shows footprints collected using each method.
(cement method) and reference photo 8 (gypsum method).
According to the results, when using plaster, the impression was washed away, but when using the cement-based rapid hardening material according to the present invention, the impression could be taken clearly without being washed away.

<Example 5> 450g of super fast hardening cement, 50g of fly ash,
A paste made by adding 250 ml of water to a cement-based rapid hardening material containing 8 g of plasticizer and 10 g of thickener and kneading the mixture for 20 seconds was poured into an underwater footprint (on red clay at a depth of about 2 cm).

Additionally, a plaster paste made by mixing 800g of plaster with an appropriate amount of water was poured into the same footprint. At this time, the air temperature was 12℃ and the water temperature was 14℃.

The total time required to complete footprint collection was 15 minutes using cement-based rapid hardening material. On the other hand, when plaster was used, the plaster paste spread in the water, making it impossible to collect footprints.

As shown in Reference Photo 9, the footprints collected using the cement-based rapid hardening material according to the present invention gave a clear impression.

<Example 6> 450g of super fast hardening cement, 50g of fly ash,
Add 250 ml of water to a cement-based rapid hardening material containing 0.5 g of antifoaming agent and 8 g of thickener and mix for 20 seconds. Sprinkle 100 g of ultra-fast hardening cement in advance and record underwater footprints after 10 minutes (water depth: approx. 2 cm of sand).

In addition, 800g of plaster was mixed with 100g of plaster and sprinkled with 2% table salt, and the same footprint was sprinkled with 800g of plaster for 15 minutes.
A plaster paste made by mixing g with an appropriate amount of water was poured into the mold. At this time, the air temperature was 12℃ and the water temperature was 14℃.

The total time required to complete footprint collection was 25 minutes when using cement-based quick-setting material and 75 minutes when using plaster.

10 reference photos of footprints collected using each method
(cement method) and reference photo 11 (gypsum method).
According to the results, when plaster was used, the impression was distorted, whereas when the cement-based rapid hardening material according to the present invention was used, a clear impression could be obtained.

<Example 7> 450g of super fast hardening cement, 50g of fly ash,
A cement-based rapid hardening material containing 0.5 g of an antifoaming agent, 8 g of a fluidizing agent, and 8 g of a thickening agent was mixed with 250 ml of water for 20 seconds, and the paste was poured onto footprints in the snow.

Additionally, a plaster paste made by mixing 800g of plaster with an appropriate amount of water was poured into the same footprint. Note that the air temperature at this time was 2°C and the water temperature was 4°C.

The total time required to complete the footprint collection was 20 minutes for the cement-based rapid hardening material. On the other hand, in the case of gypsum, it was determined that it could not be collected because it did not harden even after more than 2 hours had passed, and the process was discontinued.

The footprints collected using cement-based quick-hardening material are shown in Reference Photo 12, and a clear impression could be obtained.

Claims (1)

[Scope of Claims] 1. A method for collecting traces, which comprises pouring paste or mortar of a cement-based rapid hardening material onto the traces to obtain a hardened body to which the impression of the traces has been transferred. 2. Claim 1, characterized in that the traces are three-dimensional footprints impressed on a soil surface or sand, semi- three-dimensional footprints impressed with mud on a smooth surface, underwater footprints, footprints in snow, or tire tracks. Trace collection method described in section. 3. Sprinkle cement-based quick-hardening material powder on the traces in water or snow and let it harden, and then pour cement-based rapid-hardening material paste on top of it to obtain a hardened product with the impression of the traces transferred. Characteristic trace collection method.