Materials 2015, 8, 6257-6276; doi:10.3390/ma8095306

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materials ISSN 1996-1944 www.mdpi.com/journal/materials Article

Material Performance and Animal Clinical Studies on Performance-Optimized Hwangtoh Mixed Mortar and Concrete to Evaluate Their Mechanical Properties and Health Benefits Bon-Min Koo 1 , Jang-Ho Jay Kim 1, *, Tae-Kyun Kim 1 and Byung-Yun Kim 2 1

Concrete Structural Engineering Laboratory, School of Civil and Environmental Engineering, Yonsei University, Seoul 120-794, Korea; E-Mails: [email protected] (B.-M.K.); [email protected] (T.-K.K.) 2 Department of Architectural Engineering, Catholic Kwandong University, Gangneung 210-701, Korea; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +82-2-2123-5802; Fax: +82-2-364-1100. Academic Editor: Jorge de Brito Received: 1 June 2015 / Accepted: 8 September 2015 / Published: 17 September 2015

Abstract: In this study, the amount of cement used in a concrete mix is minimized to reduce the toxic effects on users by adjusting the concrete mixture contents. The reduction of cement is achieved by using various admixtures (ground granulated blast-furnace slag, flyash, ordinary Portland cement, and activated Hwangtoh powder). To apply the mix to construction, material property tests such as compressive strength, slump, and pH are performed. Preliminary experimental results showed that the Hwangtoh concrete could be used as a healthy construction material. Also, the health issues and effects of Hwangtoh mortar are quantitatively evaluated through an animal clinical test. Mice are placed in Hwangtoh mortar and cement mortar cages to record their activity. For the test, five cages are made with Hwangtoh and ordinary Portland cement mortar floors, using Hwangtoh powder replacement ratios of 20%, 40%, 60%, and 80% of the normal cement mortar mixing ratio, and two cages are made with Hwangtoh mortar living quarters. The activity parameter measurements included weight, food intake, water intake, residential space selection, breeding activity, and aggression. The study results can be used to evaluate the benefits of using Hwangtoh as a cement replacing admixture for lifestyle, health and sustainability.

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Keywords: Hwangtoh; health benefits; Institute for Cancer Research (ICR); material properties; mix proportion design

1. Introduction A recent study by the city of Seoul, South Korea, stated that foreign and domestic ordinary Portland cement (OPC) products emitted 4.14 ppm and 13 ppm, respectively, of poisonous hexavalent chromium Cr(VI). Thus, domestic OPC is 3.25 times more hazardous than foreign OPC [1]. Since 2009 in Korea, the maximum domestic and international allowable amount of Cr(VI) in OPC cement is 20 mg/kg and 2 mg/kg, respectively. It has been reported that Hwangtoh (red clay) does not contain Cr(VI) substance [2]. Such concerns have led to a rise in the use of activated Hwangtoh as an eco-friendly construction material. As a result, much research has been conducted on Hwangtoh-mixed construction materials. However, most of it has focused on differences in the material and structural performance capacities of OPC and Hwangtoh; unfortunately, no study has yet quantified the health benefits of Hwangtoh-mixed construction materials. Published reports have considered the activation method of kaolin and activated kaolin-mixed mortar concrete as well as the development of Hwangtoh admixtures for cement mortars [3–6]. A Hwangtoh cement mortar study analyzed the effect of various firing temperatures on the compressive strength of Hwangtoh mortars and Hwangtoh concrete, suggesting an optimum firing temperature range of 500 ˝ C–1000 ˝ C. Moreover, the same study reported that Hwangtoh serves as an appropriate cementitious material, because its performance equals or exceeds that of other materials, such as blast furnace slag micropowders and flyash [7–9]. Based on mineralogical categorization, Hwangtoh is defined as a Halloysite in the kaolin or China clay group, composed mainly of SiO2 , Al2 O3 , and Fe2 O3 [3]. Hwangtoh behaves similarly to concrete admixtures and has the pozzolanic reaction when mixed with cement and water [10,11]. To increase the usability of Hwangtoh as a construction material, activated Hwangtoh is produced by burning natural Hwangtoh at temperatures of 550 ˝ C–1000 ˝ C and quickly cooling it before grinding it into powder form [12]. The published studies report that partial replacement of cement with activated Hwangtoh produces Hwangtoh mortar or Hwangtoh concrete with sufficient strength for possible use as a construction material [13]. A study evaluated the workability, compressive strength, inelastic deformation, and hydration heat of concrete mixed with Hwangtoh or blast furnace slag micropowders by analyzing stress–strain relations, flexural behavior, dry shrinkage, and the creep characteristics of reinforced concrete beams mixed with Hwangtoh or blast furnace slag [12,14]. According to that study, the long-term behaviors of concrete mixed with Hwangtoh or blast furnace slag, such as creep and shrinkage, vary depending on the choice of cementitious material. The dry shrinkage increases when Hwangtoh alone is used, but decreases when both Hwangtoh and blast furnace slag are used. Furthermore, an examination of Hwangtoh mortars without cement revealed that Hwangtoh increased drying shrinkage by 20% [15]. A study of the cytotoxicity of recycled OPC mortar powder reported that the tested powders exhibit a strong and concentration-dependent cytotoxicity of 75.5% [16]. A study assessed the effect of grouting materials on pollution by examining the fish toxicity of those materials [17]. Our review of the literature showed that most studies have focused on structure and durability issues that arise from adding a Hwangtoh

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admixture, without consideration for any potential health benefits from its use. Meanwhile, in Japan, vigorous research has been conducted on the harmful properties of construction materials such as concrete, metal, and timber. A study found that the survival rates of experimental subjects were 7%, 41%, and 81% for concrete, metal, and timber, respectively, showing that concrete had the lowest survival rate [18]. Thus, in the present study, a preliminary experiment is conducted to determine the appropriate ratio of Hwangtoh to cement and identified the properties of Hwangtoh mixed concrete. Then, a human health benefit assessment is conducted using ICR mice in cages built with either Hwangtoh mixed mortar or cement mortar [19]. We made one cage with a cement mortar floor and four cages with Hwangtoh mixed mortar floors with varying ratios of Hwangtoh to cement (20%, 40%, 60%, and 80%) and two cages with cement mortar and Hwangtoh cement mortar walls and floor to assess the experimental subjects’ choice of living environment. In addition, the subjects’ weight change, food intake, water intake, residential environment preference, fertility rate, and aggression are measured to evaluate the human health benefits of the different materials. The ultimate objective of this study was to develop environmentally friendly construction materials. 2. Material Properties of Activated Hwangtoh Mixed Concrete 2.1. Reaction Mechanism Hwangtoh in its natural state has a very low reactivity. However, when heated at high temperatures and cooled rapidly, it is activated by the preserved crystallization energy and holds latent hydraulic properties that harden under certain conditions. The chemical composition of the Hwangtoh we used is shown in Table 1. When Hwangtoh is activated by heating at 550 ˝ C–950 ˝ C, it transitions into an excited state of high pozzolanic reactivity, but it does not have a hydration reactivity when in contact with water. However, Hwangtoh does initiate hydration under alkaline conditions. Concrete is a natural alkaline material; thus mixing activated Hwangtoh in concrete will induce pozzolanic reactions. The activated Hwangtoh reacts with calcium hydroxide (Ca(OH)2 ), the hydration product of cement, and acquires latent hydraulic properties that in turn enhance the strength and water resistance of the concrete. Furthermore, mixing activated Hwangtoh into cement blocks reduces the size of internal voids by filling the spaces between the binder particles, which increases the contact area between the binder and the aggregate, reducing overall concrete bleeding and segregation. At room temperature, silicon dioxide (SiO2 ), a component of activated Hwangtoh, binds with Ca(OH)2 and produces a stable pozzolanic product that holds the same properties as other pozzolanic materials, such as blast furnace slag and flyash. Activated Hwangtoh is a material that under goes pozzolanic reaction. It has been reported that Hwangtoh in natural and activated state does not and does have pozzolanic activity, respectively [20]. However, it has not been completely proven that activated Hwangtoh has hydration capacity. From a published report on the topic, the measured hydration temperature of concrete mixed with activated Hwangtoh powder and OPC (41.0 ˝ C) was slightly lower than that of 100% OPC concrete (56.4 ˝ C), indicating that less hydration reaction has taken place by replacing a portion of OPC with activated Hwangtoh powder [21–23]. Therefore, a further study on this topic must be performed.

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Component SiO2 Al2 O3 Fe2 O3 K2 O TiO2 MgO F CaO Na2 O P2 O5 MnO SO3

Unit Mass Percentage (%) Hwangtoh

Cement

57.7 29.5 6.32 3.54 1.12 1.06 0.22 0.126 0.114 0.0620 0.0518 0.0434

22.0 5.80 3.30 – – 1.20 – 64.04 – – – –

Depending on the product formed by the reaction between activated Hwangtoh and Ca(OH)2 , the reaction can be classified as pozzolanic or stratlingite. A pozzolanic reaction between SiO2 (Hwangtoh) and Ca(OH)2 (cement) produces the pozzolanic product afwillite. The equation for the reaction is shown in Equation (1): 3CapOHq2 ` 2SiO2 Ñ 3CaO¨ 2SiO2 ¨ 3H2 O (1) SiO2 and aluminum oxide (Al2 O3 ) from Hwangtoh and Ca(OH)2 from cement can also react to form stratlingite, which makes the activated Hwangtoh into a dense mortar. The unstable Ca(OH)2 becomes stable after undergoing the stratlingite reaction, which leads to increased long-term strength, durability, and crack resistance in the concrete. The activated Hwangtoh we used was a product of the Gochang region of Korea composed of natural-state Hwangtoh sintered at 850 ˝ C. The specific gravity and fineness of the activated Hwangtoh were 2.7 cm2 /g and 3200 cm2 /g, respectively. The chemical composition of activated Hwangtoh and OPC are shown in Table 1. 2.2. Calculating the Replacement Ratio of Activated Hwangtoh Activated Hwangtoh absorbs more water than ordinary concrete. Therefore, the appropriate mixture proportion based on workability needed to be selected. The cement used in this study had a specific gravity of 3.16. As required by KS L ISO 679 [24], a standard aggregate produced for concrete and mortar with specific gravity of 2.6 and 2.7, respectively, was used for the fine aggregate. The coarse aggregate was a crushed stone aggregate with a maximum diameter of 25 mm and saturated surface-dry specific gravity of 2.65. In addition, to determine the appropriate mixture ratio of activated Hwangtoh, the compressive strength was measured by setting the water-to-binder (W/B) ratio at 43% and increasing the proportion of blast furnace slag from 0%–40% in 10% increments. As shown in Figure 1a, the proportion of activated Hwangtoh ranged from 15%–25%. Because concrete mixed with activated Hwangtoh has a lower compressive strength than ordinary concrete, a 20% ratio of activated Hwangtoh was chosen to secure maximal compressive strength. Figure 1b displays the changes in slump for the different replacement ratios.

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1.4

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Target range

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1

1

Relative slump

Relative compressive strength

Target range

1.2

0.8 GGBS 00 GGBS 10 GGBS 20 GGBS 30 GGBS 40

0.6 0.4

0.8 GGBS 00 GGBS 10 GGBS 20 GGBS 30 GGBS 40

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10

20

30

40

0

Replacement ratio of Hwangtoh (%)

10

20

30

40

Replacement ratio of Hwangtoh (%)

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(b)

Figure 1. Relative compressive strength Figure 1. Relative compressive strengthand andslump slumptest testresults resultson onconcrete concrete samples. samples. (a) Actual strength ratioratio and and (b) (b) Actual slump/required (a)strength/required Actual strength/required strength Actual slump/requiredslump slump ratio. ratio. 2.3. Slump Test 2.3. Slump Test Based on the KS F 2401 [25] and KS F 2402 [26] testing methods, the slump was measured by testing

Based on the KS F 2401 [25] and KS F 2402 [26] testing methods, the slump was measured by a sample of ordinary concrete and activated Hwangtoh mixed concrete. The ordinary concrete showed a testing a sample of ordinary concrete activated Hwangtoh ordinary concrete slump of 10 cm–13 cm, whereas the and activated Hwangtoh mixed mixed concreteconcrete. showed aThe slump of less than showed slump of cm 10 for cm–13 cm, whereas HwangtohThe mixed showed a slump 1.0 acm and 3.5 a W/B ratio of 43%the andactivated 45%, respectively. slumpconcrete was enhanced when the of less than cm for a W/Bthe ratio of 43% and 45%, respectively. The slump was enhanced W/B 1.0 ratiocm wasand set 3.5 to 50%. However, 28 day compressive strength of the concrete with a 50% W/B ratio and 20% activated Hwangtoh was significantly lower. To generate an appropriate slump, when the W/B ratio was set to 50%. However, the 28 day compressive strength of the concretea with polycarbonate-based superplasticizer was added at increasing ratios from 1%–2% in 0.5% increments. a 50% W/B ratio and 20% activated Hwangtoh was significantly lower. To generate an appropriate At 2%, the required slump was obtained, but concrete segregation occurred. The most appropriate slump, a polycarbonate-based superplasticizer was added at increasing ratios from 1%–2% in 0.5% proportion of superplasticizer for the required strength and slump was 1.5%. Table 2 shows the changes increments. At 2%, the required slump was obtained, but concrete segregation occurred. The most in slump for varying proportions of superplasticizer in the 20% activated Hwangtoh concrete mixture appropriate proportion of superplasticizer for the required strength and slump was 1.5%. Table 2 shows with a 45% water-to-binder (W/B) ratio. the changes in slump for varying proportions of superplasticizer in the 20% activated Hwangtoh concrete Table 2. Slump test results. mixture with a 45% water-to-binder (W/B) ratio. Water-to-binder ratio (%)

Water-to-binder ratio 45 (%)

45 2.4. Compressive Strength

Hwangtoh replacement ratio (%) Table 2. Slump Control test results.

Plasticizer (%) Slump (cm) – 13 – 3.5 Hwangtoh replacement ratio (%) Plasticizer (%) 6 Slump (cm) 1 20 1.5 – 9–10 Control 13 2 15–18

20

–

3.5

1

6

1.5 9–10 For the preliminary test, concrete with 20% activated Hwangtoh, three W/B ratios2(43%, 45%, and15–18 50%), and varying proportions of blast furnace slag and flyash (5%–25%) were used. Tables 3–5 show the mixture proportions of Hwangtoh concrete. The air content of the fresh concrete was measured using the pressure

2.4. Compressive Strength

For the preliminary test, concrete with 20% activated Hwangtoh, three W/B ratios (43%, 45%, and 50%), and varying proportions of blast furnace slag and flyash (5%–25%) were used. Tables 3–5 show the mixture proportions of Hwangtoh concrete. The air content of the fresh concrete was measured using

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the pressure method in KS F 2421 [27], which showed that it satisfied the criteria of 4.5%. The slump range and air content was set to 12 ˘ 2.0 mm and 4.5 ˘ 0.5%, respectively. G in Table 3 refers to the ground granulated blast furnace slag (GGBS) and F refers to the flyash. Twelve specimens were prepared for each case and wet cured each specimen at 20 ˝ C in accordance with KS F 2403 [28]. Blast furnace slag with a specific gravity and fineness of 2.90 cm2 /g and a 4306 cm2 /g, respectively, were used. In Table 3, Hwangtoh, water, cement, fine aggregate (sand), coarse aggregate (gravel), GGBS, flyash, and fine aggregate/total aggregate ratio are abbreviated HT, W, C, S, G, GGBS, F, and S/a, respectively. Table 3. Mix proportion of Hwangtoh concrete (W/B 43%, S/a 40%, HT 20%). Specimen Control G 5F25 G10F20 C15F15 G20F10 G25F 5

W

C

S

Unit (kg/m3 ) G HT

409 176

204.5

– 679

1034

81.8

GGBS

F

– 20.45 40.9 61.35 81.8 102.3

– 102.3 81.8 61.35 40.9 20.45

Table 4. Mix proportion of Hwangtoh concrete (W/B 45%, S/a 40%, HT 20%). Specimen Control G 5F25 G10F20 C15F15 G20F10 G25F 5

W

C

S

Unit (kg/m3 ) G HT

391 176

195.5

– 681

1042

78.2

GGBS

F

– 19.55 39.1 58.65 78.2 97.75

– 97.75 78.2 58.65 39.1 19.55

Table 5. Mix proportion of Hwangtoh concrete (W/B 50%, S/a 40%, HT 20%). Specimen Control G 5F25 G10F20 C15F15 G20F10 G25F 5

W

C

S

Unit (kg/m3 ) G HT

352 176

176

– 694

1062

70.4

GGBS

F

– 17.6 35.2 52.8 70.4 88

– 88 70.4 52.8 35.2 17.6

Flyash with a specific gravity and fineness of 2.19 cm2 /g and 3.490 cm2 /g, respectively, was used to mix the concrete in accordance with KS L 5405 [29]. The flyash was incorporated to improve the workability, strength, and durability of the Hwangtoh mixed concrete by reducing the heat of hydration, increasing the water permeability, and increasing the corrosion and chemical resistance. Although several types of superplasticizers are available, such as naphthalene, melamine, and aminosulfonate, the polycarbonate superplasticizer we used is the most popular option for concrete because of its excellent cement dispersing and slump maintaining characteristics. Moreover, polycarbonate superplasticizer is

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cement dispersing and slump maintaining characteristics. Moreover, polycarbonate superplasticizer is less vulnerable than other superplasticizers to changes in physical properties over time. Therefore, it was less vulnerable than other superplasticizers to changes in physical properties over time. Therefore, it was used to increase the workability of Hwangtoh mixed concrete. The particular superplasticizer used in used to increase the workability of Hwangtoh mixed concrete. The particular superplasticizer used in this experiment had a dark brownish color with a specific gravity of 1.080 and a pH of 7.0 at 20 ˝ C. this experiment had a dark brownish color with a specific gravity of 1.080 and a pH of 7.0 at 20 °C. After casting 12,100 mm ˆ 200 mm cylindrical specimens using activated Hwangtoh mixed concrete, After casting 12,100 mm × 200 mm cylindrical specimens using activated Hwangtoh mixed concrete, their compressive strengths on the 7th, 14th, and 28th days from casting were measured in accordance their compressive strengths on the 7th, 14th, and 28th days from casting were measured in accordance with KS F 2403 [28] and KS F 2405 [30]. The lowest and highest measured values were eliminated with KS F 2403 [28] and KS F 2405 [30]. The lowest and highest measured values were eliminated and and calculated average compressive strength withthe theremaining remaining10 10specimens. specimens. Figure Figure 22 shows shows the calculated the the average compressive strength with the compressive strength test results for ordinary concrete and concrete mixed with 20% activated Hwangtoh, compressive strength test results for ordinary concrete and concrete mixed with 20% activated both with aboth W/Bwith ratio of 43%. Figures 3 and 43 show compressive strength test results of the Hwangtoh, a W/B ratio of 43%. Figures and 4 the show the compressive strength test results of same concrete with a W/B ratio of 45% and 50%, respectively. The compressive strength increased the same concrete with a W/B ratio of 45% and 50%, respectively. The compressive strength increased as With the as the the W/B W/B ratio ratio decreased. decreased. With the same same W/B W/B ratio, ratio, the the differences differences in in the the compressive compressive strengths strengths of of ordinary concrete and and activated activated Hwangtoh Hwangtohmixed mixedconcrete concretewere were7.69 7.69MPa, MPa,5.47 5.47 MPa 3.48 MPa ordinary concrete MPa andand 3.48 MPa for for W/B ratios of 43%, 45% and 50%, respectively. The differences in the compressive strength W/B ratios of 43%, 45% and 50%, respectively. The differences in the compressive strength decreased decreased the W/B ratio increased. Concrete with furnace 20% blast slagflyash and 10% flyash as the W/Basratio increased. Concrete with 20% blast slagfurnace and 10% showed the showed highest the highest compressive strength, andwith concrete blast slag furnace 5% had flyash the compressive strength, and concrete 25% with blast25% furnace and slag 5% and flyash thehad lowest lowest compressive strength. follow-up are required to better examine the causes of compressive strength. Further Further follow-up studies studies are required to better examine the causes of these these differences in compressive strength. Figure 5 shows the 28-day compressive strength results differences in compressive strength. Figure 5 shows the 28-day compressive strength test test results for for ordinary concrete and Hwangtoh mixed concrete with a W/B ratio of 45%. ordinary concrete and Hwangtoh mixed concrete with a W/B ratio of 45%.

Figure Compressive strength Figure 2. 2. Compressive strength history history of of concrete concrete with with GGBS GGBS and and flyash flyash (W/B (W/B 43%). 43%).

Figure 3. Compressive strength history of concrete with GGBS and flyash (W/B 45%). Figure 3. Compressive strength history of concrete with GGBS and flyash (W/B 45%).

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Figure 4. Compressive strength history of concrete with GGBS and flyash (W/B 50%). Figure 4. 4. Compressive Compressive strength strength history history of of concrete concrete with with GGBS GGBS and and flyash flyash (W/B (W/B 50%). 50%). Figure

Figure 5. Compressive strength test results (W/B 45%). Figure 5. 5. Compressive Compressive strength strength test test results results (W/B (W/B 45%). 45%). Figure

2.5. pH pH 2.5. A thethe pH. This equipment cancan measure a pHaa range fromfrom 0–14.0–14. Flat A pH150-C pH150-Cwas wasused usedtoto tomeasure measure the pH. This equipment can measure pH range range from 0–14. pH150-C was used measure pH. This equipment measure pH surface electrodes werewere attached to the surface ofof the Flatsurface surface electrodes were attached tothe the surface of theactivated activatedHwangtoh Hwangtohmixed mixedconcrete concretespecimens specimens Flat electrodes attached to surface the activated Hwangtoh mixed concrete and measurements measurements atat three three points points from from each each specimen specimenwere wereobtained obtainedto tocalculate calculatethe themean. mean. The The pH pH and each specimen were obtained to calculate the mean. values of of the the ordinary ordinary concrete, concrete, the the concrete concrete without without activated activated Hwangtoh, Hwangtoh, and and the the activated activated Hwangtoh Hwangtoh values with W/B W/B ratio of45% 45%were wereobtained obtainedand andare areshown shownas abar bar graph in Figure 6. mixed concrete concrete with ratio of of 45% were obtained and are shown asas graph in Figure Figure 6. The TheThe pH mixed aa bar graph in 6. pH pH of ordinary the ordinary concrete for construction ranges from 12.5 13.OPC Themeasured OPC measured in the of the the ordinary concrete usedused for construction construction ranges from12.5 12.5 to to 13.to The OPC measured in the the present present of concrete used for ranges from 13. The in study had had pH ofa13. 13. The pHThe of the the concrete withoutwithout activated Hwangtoh rangedranged from 11.51 11.51 to 11.78, study aa pH of pH of without activated Hwangtoh ranged from 11.78, present study had pHThe of 13. pHconcrete of the concrete activated Hwangtoh fromto 11.51 to depending on the the proportions proportions of blast blastoffurnace furnace slag and and flyash. The pH pHThe of the the activated Hwangtoh mixed depending on of slag flyash. The of Hwangtoh mixed 11.78, depending on the proportions blast furnace slag and flyash. pHactivated of the activated Hwangtoh concrete was 10.32–10.50. 10.32–10.50. The Ca(OH) Ca(OH) produced by the the hydration hydration reactionreaction with the thewith cement forms aa concrete was The by reaction with cement mixed concrete was 10.32–10.50. The Ca(OH) by the hydration the forms cement 22 produced 2 produced passive film that that protects the rebar. rebar. However, loses alkalinity bybybinding binding totoCO CO it becomes becomes passive film protects the However, ifif ititifloses alkalinity by becomes forms a passive film that protects the rebar. However, it loses alkalinity bindingto CO22,2,, itit carbonated and and forms forms CaCO with pH ofof8–9. 8–9. The pHpH of the the activated Hwangtoh mixed concrete was carbonated The pH of Hwangtoh mixed concrete was carbonated and forms CaCO CaCO333with withaaapH pHof 8–9. The of activated the activated Hwangtoh mixed concrete 1.19–1.28 lowerlower than that that of of theof concrete withoutwithout activated Hwangtoh; the pH pH of of thepH ordinary concretes 1.19–1.28 lower than the concrete without activated Hwangtoh; the the ordinary was 1.19–1.28 than that the concrete activated Hwangtoh; the of the concretes ordinary was 1.25–1.54 1.25–1.54 higher than thanhigher that of ofthan the activated activated Hwangtoh mixed concretes. These resultsThese indicate that was that the concretes. results indicate that concretes was higher 1.25–1.54 that of theHwangtoh activated mixed Hwangtoh mixedThese concretes. results users must must pay meticulous attention notattention to expose exposenot activated Hwangtoh mixed concrete to substandard substandard users meticulous not to activated Hwangtoh concrete to indicate thatpay users must payattention meticulous to expose activatedmixed Hwangtoh mixed concrete to conditions. From From published report, poisonous and beneficial beneficial effects of ofeffects OPC and and Hwangtoh porous conditions. aa published poisonous and effects OPC Hwangtoh porous substandard conditions. From areport, published report, poisonous and beneficial of OPC and Hwangtoh

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porous livingrespectively, insects, respectively, found to be and low pH property, concreteconcrete on livingon insects, were found were to be due to high anddue lowtopHhigh property, respectively [31]. respectively is safe to assume that Hwangtoh contains less harmful substances than Therefore, it[31]. is safeTherefore, to assumeitthat Hwangtoh contains less harmful substances than OPC cement with OPC cement withissues. regards to health issues. regards to health

Figure 6. pH test results (W/B 45%). Figure 6. pH test results (W/B 45%). 3. Health Benefit Benefit Assessment 3. Health Assessment of of Activated Activated Hwangtoh Hwangtoh Mixed Mixed Concrete Concrete The benefit assessment The health health benefit assessment was was performed performed on on three-week-old three-week-old ICR ICR mice, mice, which which are are frequently frequently used used in All experimental experimental procedures procedures complied in animal animal clinical clinical studies. studies. All complied with with the the Institutional Institutional Animal Animal Care Care and and Use Committee (IACUC) mice standard operating guidelines, the Korean Food and Drug Administration Use Committee (IACUC) mice standard operating guidelines, the Korean Food and Drug Administration guidelines foranimal animalexperimentation, experimentation, manuals on experiments involving animals [32].cage Thefloors cage guidelines for andand manuals on experiments involving animals [32]. The floors with different of Hwangtoh to cement (20%, 40%, 60%, 80%) witha athickness thicknessofof33 cm cm were with different ratiosratios of Hwangtoh to cement (20%, 40%, 60%, 80%) with prepared, as shown in Figure 7. The titles for the floors made with 20%, 40%, 60%, and 80% Hwangtoh concrete are floor floor 20, 20, floor floor 40, 40,floor floor60, 60,and andfloor floor80, 80,respectively, respectively,and andthe thetitle titleofofOPC OPC concrete floor concrete floor is is floor OPC.All Allofofthe themice micewere werekept keptatatthe thesame sametemperature temperatureand and humidity humidity and and provided provided with equal floor OPC. amounts of food and water. To To alleviate alleviate their their stress, stress,exercise exerciseequipment equipmentwas wasinstalled installed cage. in in thethe cage. ForFor the the comparison of residential environments, two with casts awith a length of 122.6 cm, a of width of 51 cm, a comparison of residential environments, two casts length of 122.6 cm, a width 51 cm, a height height of 62 cm, athickness floor thickness of and 5 cm, and thickness a wall thickness 3 cmmanufactured. were manufactured. of 62 cm, a floor of 5 cm, a wall of 3 cmofwere ExactlyExactly half of half eachwas castpoured was poured ordinary cement mortar, other halfwas waspoured pouredwith with aa mixture eachofcast with with ordinary cement mortar, andand thethe other half containing either 20% 20% or or80% 80%activated activatedHwangtoh, Hwangtoh,asasshown showninin Figure Therefore, the title of cast the Figure 8. 8. Therefore, the title of the cast Hwangtoh concrete OPC concrete H20and andOPC20, OPC20,respectively. respectively. Likewise, Likewise, 80% withwith 20%20% Hwangtoh concrete andand OPC concrete areareH20 Hwangtoh and OPC OPCconcrete concreteare aretitled titledH80 H80and and OPC80, respectively. A passageway connecting the Hwangtoh and OPC80, respectively. A passageway connecting the two two allowed mice to move freely eitherside. side.The Themortar’s mortar’smixture mixture ratio ratio was: was: 0.5 0.5 (water):1 castscasts allowed the the mice to move freely to toeither (water):1 (cement):3 (fine (fine aggregate). aggregate). One One pair pair of of male casts (cement):3 male and and female female ICR ICR mice mice were were placed placed in in each each of of the the five five casts for the the floor floor experiment, experiment,and andfive fivemale maleand andfive five female ICR mice were placed in each of the casts for female ICR mice were placed in each of the twotwo casts for for the residential selection experiment. the residential selection experiment.

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(a)

(b)

Figure 7. Floor cage photos. (a) Casted bottom surfaces and (b) Floor cages. Figure 7. Floor cage photos. (a) Casted bottom surfaces and (b) Floor cages.

(a)

(b)

(c)

(d)

(e)

(f)

Figure types. Residence cagecage forms; (b) Figure 8.8. Residence Residence cage cage photos photosand andspecimen specimen types.(a)(a) Residence forms; Concrete mixing; (c) Casting and curing; (d) Sleeping spaces; (e) 20% Hwangtoh and OPC (b) Concrete mixing; (c) Casting and curing; (d) Sleeping spaces; (e) 20% Hwangtoh and mortar, and (f) 80% Hwangtoh and OPC mortar. OPC mortar, and (f) 80% Hwangtoh and OPC mortar.

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4. Temperature and 4. Temperature and Humidity Humidity Changes Changes Depending Depending on on Mixture Mixture Ratios Ratios The The external external and and internal internal temperatures temperatures of of each each cage were measured at the same time daily, as as shown shown in Figures 9 and 10 respectively. From day 21 onwards, the internal temperature surpassed the external in Figures 9 and 10, respectively. From day 21 onwards, the internal temperature surpassed the external temperature because day day 21 21marked markedthe thebeginning beginningofofwinter. winter. Until the internal temperature Until dayday 21, 21, the internal temperature was temperature because was the highest in cast 21, internal the internal temperature higher in H80. By and large, the highest in cast H20;H20; afterafter day day 21, the temperature waswas higher in H80. By and large, the the temperature higher in casts the casts prepared Hwangtoh concrete than the concrete OPC concrete temperature was was higher in the prepared with with Hwangtoh concrete than in theinOPC casts. casts. The temperature within of OPC20 was than higher in OPC80. that of OPC80. Under equal The temperature within the castthe of cast OPC20 was higher in than that of Under equal external external temperatures, the differences in internal temperature and humidity in the activated Hwangtoh temperatures, the differences in internal temperature and humidity in the activated Hwangtoh mixed ˝ ˝ mixed environment andOPC the OPC environment ranged to 1.5 and1% 1%toto5%, 5%, respectively. respectively. environment and the environment ranged fromfrom 0.1 0.1 °C toC 1.5 °C Cand Although Although those those differences differences are are small, small, the the ICR ICR mice mice were were sensitive sensitive to to them. them. Moreover, the the humidity humidity of of the external environment was lower than that in any internal environment throughout the duration of the the external environment was lower than that in any internal environment throughout the duration of the study. wasthe thehighest highestininthe theinternal internal environment H80 cast, followed by the OPC20, environment of of thethe H80 cast, followed by the OPC20, H20,H20, and study. ItItwas and OPC80 The humidity within the OPC20 and H20 fell sharply between 15 and OPC80 casts.casts. The humidity within the OPC20 and H20 castscasts fell sharply between daysdays 15 and 17, 17, because acrylic ceilings casts weredamaged. damaged.The Thestandard standardIACUC IACUCtest test guideline guideline for for live live because the the acrylic ceilings of of thethe casts were animals states states that that the the relative relative humidity humidity required required for for ICR ICR mice mice is is 80%. 80%. As As shown shown in in Figure Figure 10, 10, the the H20 H20 animals and H80 that requirement. requirement. However, humidity was was 45%–75%, 45%–75%, less less and H80 casts casts satisfied satisfied that However, the the external external relative relative humidity than the the required required 80%. was than 80%. The The relative relative humidity humidity measurements measurements show show that that the the Hwangtoh Hwangtoh environment environment was more effective effective in in maintaining maintaining an an appropriate appropriate relative relative humidity humidity than than an an ordinary ordinaryair airenvironment. environment. more

Figure 9. 9. Temperature Temperature versus Figure versus time time curves. curves.

Figure 10. Relative humidity versus time curves. Figure 10. Relative humidity versus time curves.

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4.1. Amount of Food and Water Intake 4.1. Amount of Food and Water Water Intake Intake The amounts of food and water intake measured daily from the floor cage test are shown in Figures 11 The amounts amounts of of food food and and water water intake intake measured measured daily daily from from the the floor floor cage cage test test are are shown shown in in and 12 respectively. The amounts ofThe foodamounts and water intake measured daily from the residential selection Figures 11 and 12, respectively. of food and water intake measured daily from the Figures 11 and 12, respectively. The amounts of food and water intake measured daily from the casts are shown in Figures 13 shown and 14 in respectively. amounts were calculated by taking difference residential selection casts Figures and respectively. The were calculated by residential selection casts are are shown in Figures 13 13 The and 14, 14, respectively. The amounts amounts werethe calculated by between the initial weights of food and water and the weight of leftover amounts after 24 hours. Small taking the difference between the initial weights of food and water and the weight of leftover amounts taking the difference between the initial weights of food and water and the weight of leftover amounts food to distinguish from mouse feces; therefore, the ICR mice was fed the withICR solid cylindrical after 24 hours. food to from feces; therefore, mice was after is 24difficult hours. Small Small food is is difficult difficult to distinguish distinguish from mouse mouse feces; therefore, the ICR mice was fed fed food. As shown in Figure 11, from day 1 to 21, the amount of food intake in the floor experiment was with solid cylindrical food. As shown in Figure 11, from day 1 to 21, the amount of food intake in with solid cylindrical food. As shown in Figure 11, from day 1 to 21, the amount of food intake in the the the highest on floor 80 (80% of activated Hwangtoh), followed by floor 20, floor OPC, and floor 60. The floor floor experiment experiment was was the the highest highest on on floor floor 80 80 (80% (80% of of activated activated Hwangtoh), Hwangtoh), followed followed by by floor floor 20, 20, floor floor amount of food intake initially increased moderately and reached a plateau in floor 40, possibly because OPC, and floor 60. The amount of food intake initially increased moderately and reached a plateau OPC, and floor 60. The amount of food intake initially increased moderately and reached a plateau in in the ICR mice on the floor 40 cast were infertile. From day 21 onwards, the amount of food intake was the floor 40, possibly because the ICR mice on the floor 40 cast were infertile. From day 21 onwards, floor 40, possibly because the ICR mice on the floor 40 cast were infertile. From day 21 onwards, the highest floor intake OPC, followed by flooron floorOPC, 20, floor 60, and floor 40. This trend can 60, be attributed amount of was floor followed by 80, 20, and amount on of food food intake was the the highest highest on80, floor OPC, followed by floor floor 80, floor floor 20, floor floor 60, and floor floor 40. This trend be attributed the onset of day 21, the to onset of can colder onto during whichweather the miceon gave therebywhich increasing the gave total 40.the This trend can be weather attributed today the21, onset of colder colder weather on daybirth, 21, during during which the mice mice gave birth, the amount food intake. the design of study, the the amount of foodincreasing intake. Given the design study, the Given cause of increased food intake floorof OPC birth, thereby thereby increasing the total total amountofof ofthis food intake. Given thethe design of this this study, theincause cause of the increased food intake in floor OPC cannot be pinpointed to a change in temperature or humidity or the cannot be pinpointed to a change in temperature or humidity or the increased desire for reproduction in increased food intake in floor OPC cannot be pinpointed to a change in temperature or humidity or the desire for in substandard environment. A in-depth aincreased substandard environment. A more anatomical experiment is required understandexperiment this trend. increased desire for reproduction reproduction in aain-depth substandard environment. A more more in-depthtoanatomical anatomical experiment is to this trend. ICR mice changed and before after The ICR mice changed their andThe water andtheir afterfood parturition; theintake mice consumed is required required to understand understand thisfood trend. The ICRintake mice before changed their food and water water intake before and andmore after parturition; the mice consumed more water and food during pregnancy and less after giving birth. water and food during pregnancy and less after giving birth. The large food intake of mice on the OPC parturition; the mice consumed more water and food during pregnancy and less after giving birth. The The large food intake of mice on the OPC floor might be attributable to their survival instincts. The relatively floor might be attributable to their survival instincts. The relatively lower temperature and humidity of large food intake of mice on the OPC floor might be attributable to their survival instincts. The relatively lower temperature humidity of OPC might ICR to more food and the OPC floor mightand cause ICR mice to consume more foodcause and water to supplement their energy levels lower temperature and humidity of the the OPC floor floor might cause ICR mice mice to consume consume more food and water to their levels and stronger and thus become stronger to overcome harshbecome environment. water to supplement supplement their energy energy levelstheir and thus thus become stronger to to overcome overcome their their harsh harsh environment. environment.

Figure 11. Food Food intake versus versus time curves curves (floor cages). Figure Figure 11. 11. Food intake intake versus time time curves (floor (floor cages). cages).

Figure 12. Water intake versus time curves (floor cages). Figure Figure 12. 12. Water Water intake intake versus versus time time curves curves (floor (floor cages). cages).

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Figure 13. Food intake versus time curves (residence cages). Figure Figure 13. 13. Food Food intake intake versus versus time time curves curves (residence (residence cages). cages).

Figure 14. Water intake versus time curves (residence cages). Figure Figure 14. 14. Water Water intake intake versus versus time time curves curves (residence (residence cages). cages). The showed similar upward trends in their amount The ICR ICR mice mice in in the the residential residential selection selection experiment experiment showed showed similar similar upward upward trends trends in in their their amount amount of food and water intake. day 32, the amount of food intake increased in the mice in H80, water intake. Before H80, and of food and water intake. Before day 32, the amount of food intake increased in the mice in H80, and and after day 32, the amount of food intake increased in the mice in OPC80. amount of food intake increased in the mice in OPC80. after day 32, the amount of food intake increased in the mice in OPC80. In flooring experiment, the intake was floor OPC In the the flooring flooring experiment, experiment, the the amount amount of of water water intake intake was was the the highest highest in in the the mice mice on on floor floor OPC OPC throughout the entire study duration. The mice on floor 40 showed a consistent and repetitive trend. The the entire study duration. The mice on floor 40 showed a consistent and repetitive trend. throughout the entire study duration. The mice on floor 40 showed a consistent and repetitive trend. next highest waterwater intake was was by the on floor 80, followed by floor 20, 20, floorfloor 40, 40, andand floor 60. 60. In The highest intake by the on 80, by floor The next next highest water intake was bymice the mice mice on floor floor 80, followed followed by floor floor 20, floor 40, and floor 60. the residential selection experiment, the amount of water intake followed a nearly identical upward trend In residential selection experiment, the of intake followed aa nearly identical upward In the the residential selection experiment, the amount amount of water water intake followed nearly identical upward with differences in eachin trend with differences each trendminor with minor minor differences incast. each cast. cast. 4.2. Weight Gain 4.2. Weight Weight Gain Gain Weight Weight gain at three-day intervals was measured as mandated regulations IACUC Weight gain gain at at three-day three-day intervals intervals was was measured measured as as mandated mandated by by the the regulations regulations in in the the IACUC IACUC guidelines for animal experimentation. The weight changes measured from the floor cages and residence experimentation. guidelines for animal experimentation. The weight changes measured from the floor cages and residence selection and 1616, respectively. In the experiment, the mice on floor casts are shown Figures and respectively. In the experiment, the on selection casts castsare areshown showninin inFigures Figures1515 15 and 16, respectively. In flooring the flooring flooring experiment, the mice mice on 20 showed the highest weight gain; the mice on floor 80 initially showed the lowest weight gain, but floor 20 showed the highest weight gain; the mice on floor 80 initially showed the lowest weight gain, floor 20 showed the highest weight gain; the mice on floor 80 initially showed the lowest weight gain, they ended up with the greatest weight gaingain toward the end of The The weight gaingain by the but ended up the weight toward the of the weight by but they they ended up with with the greatest greatest weight gain toward the end endthe ofexperiment. the experiment. experiment. The weight gain by mice on floor OPC was moderate in the initial and middle stages of the experiment but reached that of the mice on floor OPC was moderate in the initial and middle stages of the experiment but reached that the mice on floor OPC was moderate in the initial and middle stages of the experiment but reached that the mice onon floor 2020 byby thethe end ofof of mice floor end the experiment. The mice on floor 40 and floor 60 showed identical of the the mice on floor 20 by the end ofthe theexperiment. experiment.The Themice miceon onfloor floor40 40and andfloor floor60 60 showed showed identical identical upward trends in weight gain. Thus, the ICR mice on the concrete floor casts took in large amounts upward trends in weight gain. Thus, the ICR mice on the concrete floor casts took in large amounts of upward trends in weight gain. Thus, the ICR mice on the concrete floor casts took in large amounts of of food and water in the early and middle stages of testing to survive in their new environment. However, food and water in the early and middle stages of testing to survive in their new environment. However, food and water in the early and middle stages of testing to survive in their new environment. However, as they adjusted to the environment in the later stage of testing, as their weight gain increased significantly. as they they adjusted adjusted to to the the environment environment in in the the later later stage stage of of testing, testing, their their weight weight gain gain increased increased significantly. significantly.

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However, However, the ICR mice floor casts took in less food and water than However, the the ICR ICR mice mice on on the the Hwangtoh Hwangtoh floor floor casts casts took took in in less less food food and and water water than than the the mice mice on on the the concrete floor because of the better conditions provided by the Hwangtoh environment concrete environmental concrete floor floor because because of of the the better better environmental environmental conditions conditions provided provided by by the the Hwangtoh Hwangtoh environment environment throughout the testing. showed that all of throughout shown in in Figure Figure 16, 16, the the residential residential selection selection experiment experiment throughout the the testing. testing. As As shown experiment showed showed that that all all of of the mice initially had similar weight gains, but the mice in H20 had higher weight gain than the other the the mice mice initially initially had had similar similar weight weight gains, gains, but but the the mice mice in in H20 H20 had had aaa higher higher weight weight gain gain than than the the other other mice from the middle to the end of testing. mice mice from from the the middle middle to to the the end end of of testing. testing.

Figure 15. 15. Weight change versus time curves (floor cages). Figure Figure 15. Weight Weight change change versus versus time time curves curves (floor (floor cages). cages).

Figure 16. Weight change versus time curves (residence cages). Figure Figure 16. 16. Weight Weight change change versus versus time time curves curves (residence (residence cages). cages). 5. 5. Aggression Aggression Funase that the thelevel levelof ofstress stressand andlifespan lifespanof subjectsdiffers differsaccording according type to the type of Funase (2002) (2002) reported reported that that the level of stress and lifespan ofofsubjects subjects differs according toto thethe type of of construction material used in the subjects’ living space, such as timber, metal, or concrete. In construction construction material material used used in in the the subjects’ subjects’ living living space, space, such such as as timber, timber, metal, metal, or or concrete. concrete. In In particular, particular, particular, Funase that suggested that can reduce subjects’ lifespan years as result of Funase concrete can reduce lifespan by years as aa result of Funase suggested suggested that concrete canconcrete reduce subjects’ subjects’ lifespan by nine nine yearsby asnine result of the theaemissivity emissivity the the winter when the lowtemperature external temperature is transmitted to the internal that occurs the winter the external is to living thatemissivity occurs in inthat theoccurs winterinwhen when the low low external temperature is transmitted transmitted to the the internal internal living living environment through the walls [18]. Aggression is a particularly difficult behavior to quantitatively environment through the walls [18]. Aggression is a particularly difficult behavior to environment through the walls [18]. Aggression is a particularly difficult behavior to quantitatively measure. measure. In In the the present present study, study, itit was was measured measured by by examining examining the the level level of of damage damage to to the the equipment equipment and and structures living spaces. aggressive behavior started after day 21 (the beginning of structures within within the the living livingspaces. spaces. The The most most aggressive aggressivebehavior behaviorstarted startedafter afterday day21 21(the (thebeginning beginning of of winter), andthe theemissivity emissivitywas was considered during analysis. As shown in Figure the structures considered during the analysis. As in 17, structures within winter), and and the emissivity was considered during thethe analysis. As shown shown in Figure Figure 17, the the17, structures within within the OPC cast were more damaged than those within H80. In the residential environment selection the OPC cast were more damaged than those within H80. In the residential environment the OPC cast were more damaged than those within H80. In the residential selection experiment, the structures structures in the the H20 H20 cast cast were at however, experiment, not damaged all; the structures in the H80 cast experiment, the structures in cast were were not not damaged damaged at at all; all; however, however, the thestructures structures in in the theH80 H80cast cast sustained significant damage. ratio increased, the ICR mice felt the sustained Thus, as as the the Hwangtoh Hwangtoh admixture sustained significant significant damage. damage. Thus, Hwangtoh admixture admixture ratio ratio increased, increased, the the ICR ICR mice mice felt felt the the H80 floors and walls to be similar to soil, which brought out their natural digging and scratching instincts. H80 H80 floors floorsand andwalls wallsto tobe besimilar similarto tosoil, soil,which whichbrought broughtout outtheir theirnatural naturaldigging diggingand andscratching scratchinginstincts. instincts.

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(a)

(b)

(c)

(d)

(e)

(f)

Figure 17. Damages caused by aggression. (a) Feeding and watering containers for OPC Figure 17. Damages caused by aggression. (a) Feeding and watering containers for OPC cage; (b) Feeding and watering containers for H80 cage; (c) Protection bars for OPC floor cage; (b) Feeding and watering containers for H80 cage; (c) Protection bars for OPC floor cages; (d) Protection bars for H20 floor cage; (e) Damaged lining of H20 residence cage, cages; (d) Protection bars for H20 floor cage; (e) Damaged lining of H20 residence cage, and (f) Damaged lining of H80 residence cage. and (f) Damaged lining of H80 residence cage.

Fertility Rate The ICR mice used in this experiment were fully fertile three weeks after birth, and indeed the females in the the five five casts with different were pregnant around day 21 after birth. The fertility rates of the ICR mice in floors and and two two casts casts with with different different living living environments environments were were compared. compared. Photos Photos of of the offspring from from the the floor cage and and residence residence selection selection casts casts are are shown shown in in Figure Figure 18a,b, 18a,b, respectively. respectively. The The number number of of births births floor cage for as bar bar for the the floor floor cages cages and and the the residence residence selection selection casts castsare areshown shownininFigures Figures19 19and and20, 20 respectively, respectively, as graphs. graphs. The The regular regular and and frequent frequent pregnancy pregnancy and and reproduction reproduction shows shows that that the the amount amount of of food food and and water water provided was ample. ample. provided was

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(a) (a)

(b) (b)

Figure 18. 18. Breeding Breeding of of ICR. ICR. (a) (a) Floor Floor cages cages and (b) (b) Residence cage. cage. Figure Figure 18. Breeding of ICR. (a) Floor cages and and (b) Residence Residence cage.

Figure 19. Breeding versus time curve (floor (floor cages). cages). Figure 19. Breeding versus time curve (floor cages).

Figure 20. Breeding results curve (residence cages). Figure 20. Breeding results curve (residence cages). Figure 20. Breeding results curve (residence cages). 6. 6. Residential Residential Environment Environment Selection Selection 6. Residential Environment Selection ICR mice were allowed to choose between two different living environments, environments, one with an activated activated ICR mice were allowed to choose between two different living environments, one with an activated Hwangtoh mixed mortar and the other with an ordinary cement mortar to examine their choices mixed mortar and the other with ordinary examine their choices over over 12 12 Hwangtoh mixed mortar and the other with an ordinary cement mortar to examine their choices over 12 weeks. Equal amounts of food and water were provided in each each environment. environment. As shown in Figure Figure 21, 21, weeks. Equal amounts of food and water were provided in each environment. As shown in Figure 21, in the first experiment, experiment, all all of ofthe themice micechose chosethe theactivated activatedHwangtoh Hwangtohenvironment environmentwithin within three hours three hours of in the first experiment, all of the mice chose the activated Hwangtoh environment within three hours of of testing. They maintained selection in repetitive experiments. Furthermore, although it initially testing. They maintained theirtheir selection in repetitive experiments. Furthermore, although it initially took testing. They maintained their selection in repetitive experiments. Furthermore, although it initially took

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took three formice the mice to move to chosen their chosen environment, the selection time grew shorter with three hourshours for the to move to their environment, the selection time grew shorter with each each follow-up experiment. theexperiment, last experiment, tookthan lessone thanminute one minute for of some thetomice to follow-up experiment. In theIn last it tookitless for some the of mice move move their chosen environment. of the experiment, the amount of leftover food and in water to theirtochosen environment. At the At endthe of end the experiment, the amount of leftover food and water the in the activated Hwangtoh environment was considerably less than that in the OPC environment. Under activated Hwangtoh environment was considerably less than that in the OPC environment. Under an an equal external temperature, the temperature and humidity within the activated Hwangtoh castOPC and equal external temperature, the temperature and humidity within the activated Hwangtoh cast and ˝ ˝ OPCdiffered cast differed by °C–1.5 0.1 C–1.5 C and 1.0%–5.0%, respectively.ToTodetermine determinewhether whetherthe the differential differential cast by 0.1 °C and 1.0%–5.0%, respectively. amount of of food food and and water water intake intake in in the the two two environments environments was was caused caused by by the the differences differences in in temperature temperature amount and humidity humidity or or by by hazardous hazardous components components in in the the cement, cement, the the temperature temperature and and humidity humidity in in the the OPC OPC cast cast and were varied varied to to match match those those in in the the activated activated Hwangtoh Even under under identical identical temperature temperature were Hwangtoh environment. environment. Even and humidity humidity levels, levels, the This behavior behavior indirectly indirectly and the ICR ICR mice mice maintained maintained their their choice choice of of environment. environment. This indicates that that the the lower lower amount amount of of food food and and water water intake intake in in the the normal normal mortar mortar environment environment was was caused caused indicates by harmful harmful components componentsininthe thecement cementrather ratherthan thanthethe difference relative temperature humidity. by difference in in relative temperature andand humidity. In a further study, in-depth researchshould shouldbebeperformed performedtotoexamine examinethe thecement cement components components that that could could aInfurther study, in-depth research pose risks risks to to human human health. health. pose

(a)

(b)

Figure 21. Residence preference. (a) 20% Hwangtoh residence cage and (b) 80% Hwangtoh Figure 21. Residence preference. (a) 20% Hwangtoh residence cage and (b) 80% Hwangtoh residence cage. residence cage. 7. Conclusions Conclusions

The following conclusions are drawn from this study. study. (1) Although Althoughthe theactivated activated Hwangtoh mixed concrete showed slightly lower compressive strength (1) Hwangtoh mixed concrete showed slightly lower compressive strength than than the ordinary concrete, a suitable construction material, exceptininthose thosecases cases that that require the ordinary concrete, it is ita issuitable construction material, except require exceptionally high strength and durability. exceptionally high strength and durability. (2) Becausethethe activated Hwangtoh mixed concrete tended to absorb more the water, the addition optimal (2) Because activated Hwangtoh mixed concrete tended to absorb more water, optimal addition rate of superplasticizer for better workability was 1.5 rate of superplasticizer for better workability was 1.5 volume %.volume %. (3) The ThepH pHofofthe theactivated activatedHwangtoh Hwangtohmixed mixedconcrete concretewas waslower lowerthan thanthat thatofofordinary ordinaryconcrete. concrete. (3) (4) The The differences differences in relative humidity between OPC OPC mortarmortar and Hwangtoh cement (4) in temperature temperatureand and relative humidity between and Hwangtoh mortar measured from the residence selection casts were 0.1 °C–1.5 °C and respectively. ˝ cement mortar measured from the residence selection casts were1.0%–5.0%, 0.1 ˝ C–1.5 C and (5) 1.0%–5.0%, The amountrespectively. of food and water intake by the mice in the activated Hwangtoh environment was considerably than water that inintake the OPC Also, the mice in the activated Hwangtoh (5) The amount ofhigher food and by environment. the mice in the activated Hwangtoh environment was environment had a higher fertility rate and healthier offspring. considerably higher than that in the OPC environment. Also, the mice in the activated Hwangtoh (6) environment The ICR mice the ordinary cement castoffspring. only for food and water. At all other times, hadmoved a highertofertility rate and healthier they stayed in the activated Hwangtoh living quarter.

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(6) The ICR mice moved to the ordinary cement cast only for food and water. At all other times, they stayed in the activated Hwangtoh living quarter. Acknowledgments This study was funded by the National Research foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2011-0030040). The authors of this study would like to extend their gratitude for the support. Author Contributions Bon-Min Koo is a person who performed most of test and analysis works; a main writer of the paper. Jang-Ho Jay Kim is a PI of the research project, who provided the main idea of the study. Tae-Kyun Kim is a person who assisted the research and writing the paper. Byung Yun Kim is a consultant to the research work and writing of the paper. Conflicts of Interest The authors declare no conflict of interest. References 1. Hwang, J.P.; Hong, S.I.; Yang, H.J.; Ann, K.Y. Evaluation on hexavalent chromium content in loess additive as a inhibitive material to leachat of heavy metal. Proc. Korea Concr. Inst. 2013, 25, 281–282. 2. Lee, J.H.; Park, N.K.; Jung, Y.J.; Chu, Y.S.; Song, H.; Lee, J.K. Leaching Properties of Hexavalent Chromium in Sintering Condition of Clinker Material. Proc. Korea Concr. Inst. 2008, 20, 549–552. 3. Hwang, H.Z. Study on the Method of Activating Kaoline and the Mortar and Concrete Mixed with Active-Kaoline. Ph.D. Thesis, The Seoul National University, Seoul, Korea, February 1997. 4. Yang, K.H.; Hwang, H.Z.; Kim, S.Y.; Song, J.K. Development of a Cementless Mortar Using Hwangtoh Binder. Build. Environ. 2007, 42, 3717–3725. [CrossRef] 5. Go, S.S.; Lee, H.C.; Lee, J.Y.; Kim, J.H.; Chung, C.W. Experimental Investigation of Mortars Using Activated Hwangtoh. Constr. Build. Mater. 2009, 23, 1438–1445. [CrossRef] 6. Dinakar, P.; Sahoo, P.K.; Sriram, G. Effect of Metakaolin Content on the Properties of High Strength Concrete. Int. J. Concr. Struct. Mater. 2013, 7, 215–223. [CrossRef] 7. Choi, H.Y.; Kim, M.H.; Hwang, H.Z. Study on the Development of Hwangtoh Admixture for the Application of Cement Mortar. J. Archit. Inst. Korea 2000, 16, 95–102. 8. Choi, H.Y.; Kim, M.H.; Hwang, H.Z.; Choi, S.W. Experimental Study on the Properties of Concrete by the Kinds of Admixture and the Replacement Ratios of Activated Hwangtoh. J. Korea Concr. Inst. 2001, 13, 672–675. 9. Becknell, N.P.; Micah-Hale, W. Effect of Slag Grade and Cement Source on the Properties of Concrete. Int. J. Concr. Struct. Mater. 2011, 5, 119–123. [CrossRef]

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