KR20050038230A - Soil solidifier for week stratum containing waste concrete sludge - Google Patents

Abstract

 The present invention relates to a method for producing a high value-added soft ground soil hardener using sludge that is generated in large quantities when the recycled aggregate such as gravel and sand is recovered from waste concrete.

The sludge used in the present invention contains cement but is hardly bonded to mortar because of its primary hardening. Therefore, the sludge used in the present invention can exhibit the properties of soil hardener by mixing with blast furnace slag and portland cement to give a bond as soil hardener. In order to provide a method for producing a soft ground soil hardener using anhydrous gypsum and high purity ultra-fine silica fume to improve the initial strength, and other hydraulic irritants.

Description

Soil solidifier for week stratum containing waste concrete sludge}

The present invention relates to a soil soil hardener using waste concrete sludge. More specifically, the present invention relates to a high value-added soft ground soil hardener using sludge that is generated in large quantities and used in the recovery of recycled aggregates such as gravel and sand from waste concrete.

As a general concept, the soft ground refers to a ground composed of soft soil having low strength and high compressibility due to the nature of the soil, and its distribution location includes natural ground such as wetlands, lakes, coastal areas, and artificial ground such as landfill and fill. In addition, the definition of soft ground in an engineering concept refers to the ground requiring special treatment in consideration of the structure and characteristics of the structure constructed on the target ground.

Although the distribution of such soft grounds is not large, recent industrial development, population growth, and expansion of economic scale require comprehensive land development. The development of relatively poor areas such as landfill, sewage and sludge solidification treatment at end-of-site treatment facilities is inevitable as well as national development.

Soil hardener for soft ground is a material that improves the properties of soil by using chemical reaction or hardenability of poorly engineered soil. Other methods include forced displacement method, soil size adjustment, compaction method, drainage method, etc. However, the development of cement-based hardeners for soft ground and applied to the field shows excellent characteristics in economic and short-term.

Therefore, the present invention intends to utilize the sludge generated from recycled aggregate manufacturing process instead of portland cement as the main component of the soil hardening agent for soft ground, and water-cooled slag or fly ash, portland cement, silica fume and anhydrous for strength development. The purpose is to provide a soil hardener of excellent properties by the addition of gypsum.

The present invention comprises 20 to 30% by weight of waste concrete sludge, 25 to 50% by weight of blast furnace slag fine powder, 2 to 5% by weight of anhydrous gypsum, 10 to 30% by weight of Portland cement, 7 to 16% by weight of fly ash and It is characterized in that it is a soil soil hardener using waste concrete sludge containing 1 to 3% by weight of silica fume.

Chemical composition of the raw material used in the present invention is shown in Table 1, the physical properties are shown in Table 2 below.

Ingredient Name SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO K ₂ O SO ₃ 1g.loss Portland cement 20.70 4.49 2.90 64.33 3.76 0.86 Recycled Aggregate Sludge 27.63 22.50 0.62 42.53 6.50 - 0.60 34.50 Slag 32.26 16.57 4.11 40.63 5.47 - 0.53 - Fly ash 57.47 24.16 7.58 4.32 1.21 1.21 3.16 - Silica fume 97.10 - - - - - - - gypsum - - - 41.15 - - 58.84 -

Ingredient Name Specific gravity (g / cm 3) Powder level (㎠ / g) Compressive strength (Kgf / ㎠) Remarks 3 days 7 days 28 days Portland cement 3.15 3,450 210 262 348 Recycled Aggregate Sludge 2.53 - - - - Slag 2.83 5,580 - - - Fly ash 2.65 4,830 - - - Silica fume - 200,000 - - - gypsum - - - - -

In general, the hardening principle of Portland cement-based soft ground hardener is as follows. Cement-based hardener particles are Clinker minerals, which are composed of tricalcium silicate (C ₃ S), dicalcium silicate (C ₂ S), tricalcium aluminate (C ₃ A), tetracalcium alumino ferrite (C ₄ AF), and other trace minerals. The complex minerals are hydrate-cured, with the addition of water, producing hydrates as follows.

2 (3CaO · SiO ₂ ) + 6H ₂ O = 3CaO · 2SiO ₂ · 3H ₂ O + 3Ca (OH) ₂

2 (2CaOSiO ₂ ) + 4H ₂ O = 3CaO · 2SiO ₂ · 3H ₂ O + Ca (OH) ₂

Other hydrated lime (Ca (OH) ₂ ) liberated in this hydration reaction becomes CSH hydrate by silica and pozzolanic reaction.

Ca ⁺⁺ +2 (OH) ^- + SiO ₂ ⇒ CSH gel

The clinker minerals of CaO-containing cements hydrate and hydrate during curing.

However, since blast furnace slag contains CaO but is vitrified amorphous, hardening by hydration alone does not occur. However, it is used as a slag cement because it is hydrated and cured when anhydrous gypsum is added to the alkaline atmosphere as a hydraulic stimulant.

Poscolan materials containing a large amount of silica such as volcanic ash, fly ash, meta kaolin, silica fume, etc., are not hydrate-curable in themselves but are easily insoluble and hardenable by reacting with the free and unstable calcium hydroxide. It can produce wool and is widely used as cement mixture for stabilization of concrete. Among them, silica fume is an ultrafine particle obtained by condensing dust (by-product) suspended in exhaust gas when producing silicon, ferro-silicon (Fe-Si), etc., and is a representative pozzolanic material mainly composed of SiO ₂ . Silica fume with specific gravity of about 2.1 ~ 2.2 g / cm ³ and average particle size of about 0.1μm is composed of ultra-fine particles of 90% or more of spherical shape, which can improve the fluidity of cement. It is used a lot but it is necessary to pay attention to mixing to prevent aggregation.

The waste concrete sludge to be used in the present invention is a mixture of aggregate fine powder based on silica and hydrated Portland cement mortar. It is remarkable that a huge amount of waste concrete is generated every year in Korea, and the technology for manufacturing and utilizing recycled aggregates (gravel and sand) for recycling is greatly contributed to solving the pollution problem. However, in order to manufacture recycled aggregates, the method of crushing by impact is inevitably used, which inevitably leads to the generation of fine particles (stone powder, clay powder), as well as the hydrated and hardened cement paste constituting the concrete, which is included in the fine powder. Recycling is also difficult, and much finer powder is produced than in the manufacture of masonry aggregates.

In addition, since a large amount of washing water is used in the grinding and sorting process, the fine powder becomes a sludge state containing a large amount of water, and even a landfill becomes difficult. However, since CaO is contained in a large amount, there is a possibility of becoming a solidifying agent because there is a certain amount of binding power, but its binding strength and its strength is weak, so the waste concrete sludge is used in the mixing ratio of soil solidifying agent at about 20 to 30% by weight. In order to impart basic curing properties and strength, the blast furnace slag is blended in a range of 25 to 50% by weight.

Anhydrous gypsum is added in an amount of 2 to 5% by weight in order to improve the stimulation hardening and initial strength of the blast furnace slag, and to have a strength (3 days strength of 100 Kg / cm ² or more, 28 days strength of 180 Kg / cm ² or more). Economical soil hardener can be prepared by combining 10 to 30% by weight of Portland cement, 7 to 16% by weight of fly ash, and 1 to 3% by weight of silica fume.

The present invention will be described in more detail based on the following examples.

Example 1

Soil hardener containing 25% of waste concrete sludge, 50% of blast furnace slag and 5% of gypsum was developed by mixing fly ash and silica fume with 7% and 3% as a blending agent with 10% Portland cement for strength. Sufficient characteristics could be obtained.

At this time, the physical properties were powder 5170 (cm ² / g), the solidification time was 4:10, 8:10 for the initial and final finish, and the compressive strength (Kg / cm ² ) was 3 days 120, 7 days 178, 28 It was 215 days.

Example 2

When 25% of waste concrete sludge is reduced to 35% of blast furnace slag to 35% (3.5% of gypsum), fly ash and silica fume are blended with 10% and 1.5% as a blending agent with more than 25% Portland cement to express strength over 200 for 28 days. By this, the same characteristics could be obtained.

At this time, the physical properties of the powder 5050 (cm ² / g), the time of condensation is the final and final 4:40, 8:50, compressive strength (Kg / cm ² ) is 3 days 125, 7 days 181, 28 days 203 It was.

Example 3

When 25% of waste concrete sludge is reduced to 25% of blast furnace slag (2.5% of gypsum), the fly ash and silica fume can be reduced to 16% and 1.5% by adding 30% Portland cement and admixtures for strength of 200 or more for 28 days. By blending, the same properties could be maintained.

At this time, the physical properties were powder level 5080 (cm ² / gr), the solidification time was 4:20 and 8:40 for the initial and final finish, and the compressive strength (Kg / cm ² ) for 3 days 118, 7 days 189, 28 days It was 190.

Example 4

When the soil solidifying agent of Example 3 was mixed and solidified in a volume ratio of 2: 1 with respect to clay soil, the compressive strength (Kg / cm ² ) was about 7 to 110 and 28 days to 170, and the mixing ratio was 4: 1. In the case of 7 days 70, 28 days 110 was shown to exhibit sufficient solidification characteristics when the structure is not.

Soil solidifying agent for the soft ground of the present invention can completely recycle the sludge, which is a pollutant generated during the waste concrete recycling process, the bonding strength and initial strength by hardening (3 days strength 100kg / ㎠ or more, 28 days strength 180 kg / ㎠ Expression) can be expressed, and the physical properties are excellent and economically effective.

Claims (1)

20 to 30% by weight of waste concrete sludge, 25 to 50% by weight of blast furnace slag fine powder, 2 to 5% by weight of anhydrous gypsum, 10 to 30% by weight of Portland cement, 7 to 16% by weight of fly ash and 1 to 3 Soil hardener for soft soils containing 40% by weight of silica fume.