Low-heat high-crack-resistance mass concrete for ship lock based on ternary cooperative crack control and preparation method of low-heat high-crack-resistance mass concrete

Abstract

The invention relates to low-heat high-crack-resistance mass concrete for a ship lock based on ternary cooperative crack control and a preparation method of the low-heat high-crack-resistance mass concrete, and provides a high-speed rail phase cement mass concrete self-heating curing application technology. The high-early-strength and low-hydration-heat high-iron low-calcium cement (the content of C4AF is larger than or equal to 18%, the content of C3S is smaller than 50%, the 7d hydration heat is smaller than or equal to 230 kJ / kg, and the 3d cement mortar compressive strength is larger than or equal to 20 MPa) is applied to the mass concrete, and early hydration of the high-iron-phase cement is accelerated by means of the 40-60-DEG C self-heating curing environment in a mass concrete project so that the early tensile strength of the high-iron-phase cement can be improved, and therefore the anti-cracking performance of the concrete can be improved; and the advantages of good long-term strength increase and strong corrosion resistance are exerted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete preparation methods, in particular to a low-heat high-anti-cracking mass concrete for ship lock based on ternary synergistic crack control and a preparation method thereof. BACKGROUND

[0002] Most components of inland ship lock projects belong to mass concrete, and the crack control requirement is high and difficult. The problem of crack prevention of mass concrete for ship lock has not been well solved so far, and it is a key technical bottleneck that needs to be broken through. 1) Cement is the main source of carbon emissions in transportation construction, and green transportation construction under the double carbon strategy urgently needs cement energy saving and carbon reduction. The previous patent application team developed high-early-strength low-calcium low-heat anti-cracking cement, which has the advantages of energy saving and carbon reduction, and meets the needs of green transportation engineering construction. High-iron aluminate cement clinker is a kind of high-early-strength low-heat cement (7d hydration heat < 230J / g), and its durability is nearly 1 times higher than that of ordinary portland cement, which can improve the anti-cracking performance of mass concrete for ship lock. 2) At present, mineral admixtures (such as fly ash, mineral powder, etc.) have become an important part of the concrete industry. Due to the increasing strictness of environmental protection requirements and the increasing size of basic buildings, high-quality admixtures such as fly ash and mineral powder are in short supply. Lithium slag solid waste pollutes the environment and needs to be used in a high-quality way. 3) At present, the crack control of mass concrete (such as the Three Gorges Project) mainly uses medium and low heat cement, large mineral admixtures and air-cooled aggregates + ice to control the temperature of the mold; the above measures are costly for inland ship lock projects, and cracking is common when using ordinary portland cement; the pre-embedded cooling water pipe technology has high layout cost, is easy to seep water and affect the quality of concrete, and has the problems of poor grouting tightness and fast water cooling rate, which is easy to cause cracks; 4) It is urgent to develop new crack control technology for mass concrete of ship lock hub projects. SUMMARY

[0003] The technical problem solved by the present application is to provide a low-heat high-anti-cracking mass concrete for ship lock based on ternary synergistic crack control and a preparation method thereof to solve the above problems.

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] A preparation method of a low-heat high-anti-cracking mass concrete for ship lock based on ternary synergistic crack control, comprising the following steps:

[0006] Step 1, preparing cement raw materials, including high-early-strength low-heat cement, temperature shrinkage inducing fibers and porous lithium slag powder with a mass ratio of 100:(20-25):(0.3-0.5), and aggregates and water reducing agent;

[0007] Step 2, using gradient mixing process to mix the cement raw materials obtained in step 1, and pouring to obtain a concrete body after mixing;

[0008] Step 3, three-stage temperature control curing is carried out on the concrete blank, including a heat preservation stage of 0-24h, a spraying stage of 24-72h, and a natural curing stage of more than 72h.

[0009] Further, the temperature shrinkage induced fiber has a negative thermal expansion coefficient at 30-90℃, a shrinkage rate of no less than 1.5%, an initial shrinkage temperature of 30℃, and an interface stress transfer efficiency of no less than 85%.

[0010] Further, the porous lithium slag powder is pretreated by calcination at 800℃ and superfine grinding, has a specific surface area of no less than 500m 2 / kg, a porosity of no less than 35%, and a 90d expansion rate of no less than 0.02%.

[0011] Further, the gradient mixing process of step 2 includes the following steps:

[0012] Step 2.1, the cement raw materials and water of step 1 are added into a mixer, and high-speed stirring is carried out for 30s to obtain a cement slurry;

[0013] Step 2.2, the premixed body of the temperature shrinkage induced fiber and the porous lithium slag powder is added into the cement slurry, and medium-speed stirring is carried out for 60s to obtain a cementitious system;

[0014] Step 2.3, the aggregate, water and water reducing agent are added into the cementitious system, and low-speed stirring is carried out for 90s.

[0015] The low-heat high-anti-crack mass concrete for ship lock based on ternary synergistic crack control is prepared by the above method.

[0016] The beneficial effects of the present application are:

[0017] 1. The present application proposes the application technology of high-iron-phase cement mass concrete self-heating curing, applies high-early-strength low-hydraulic-heat high-iron low-calcium cement (C4AF content is no less than 18%, C3S content is less than 50%, 7d hydraulic heat is no more than 230kJ / kg, and 3d cement mortar compressive strength is no less than 20MPa) to mass concrete, uses the self-heating curing environment of 40-60℃ inside the mass concrete engineering to accelerate the early hydration of high-iron-phase cement to improve the early tensile strength and improve the anti-crack performance of the concrete itself, and the advantages of good late strength growth and strong corrosion resistance are also played.

[0018] 2. The present application comprehensively utilizes high-early-strength low-heat high-iron low-calcium cement (C4AF content is no less than 18%, C3S content is less than 50%, 7d hydraulic heat is no more than 230kJ / kg), porous micro-expansion finely ground lithium slag powder admixture (specific surface area is no less than 500m2 / kg), and temperature shrinkage induced fiber to synergistically prepare C20-C40 low-heat high-anti-crack mass concrete for ship lock: the adiabatic temperature rise is less than 35℃, the anti-crack grade reaches level V, and the 90d micro-expansion rate is greater than 100με. Detailed Implementation

[0019] The following embodiments are provided to better understand the present invention, but are not intended to limit the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments were purchased from conventional biochemical reagent stores.

[0020] The present invention can mainly solve the following problems:

[0021] 1. Carbon emissions: The cement industry accounts for 8% of global CO2 emissions, and the carbon footprint of traditional ship lock concrete is greater than 300 kg CO2 / m³. 3 High-speed rail low-calcium cement reduces calcination temperature (energy saving 15%), but there is a shortage of materials, especially high-quality admixtures (fly ash / mineral powder), leading to price increases of over 40%. Lithium slag solid waste can be used as a 100% substitute (cost reduction of ¥50 / m³). 3 );

[0022] 2. High crack control costs: cost of pre-cooled aggregate + cooling water pipes > ¥120 / m 3 Furthermore, the grouting was not dense enough, which led to the risk of leakage. The cooling system was cancelled, and the temperature shrinkage fiber actively controlled cracking. Cracking was widespread. The cracking rate of ordinary Portland cement used in the inland waterway lock was >60%. The maintenance cost accounted for 3-5% of the total project cost. The ternary synergy achieved Class V crack resistance (cracks ↓86.8%).

[0023] Core material technical parameters and synergistic mechanisms

[0024] 1. High early strength, low heat, high iron, low calcium cement (patented product of Wuhan University of Technology, currently available for production and procurement on the market):

[0025] With a C4AF content ≥18%, it can improve toughness and reduce brittle cracking; with a C3S content <50%, it can reduce the peak hydration heat release; with a 7-day hydration heat ≤230kJ / kg, it can suppress temperature rise from the source (a reduction of 40%); with a 3-day strength ≥25MPa, it can meet the early load-bearing requirements of the lock and improve the tensile strength of the concrete itself, thereby enhancing its crack resistance.

[0026] 2. Temperature-induced shrinkage fiber (ZL202310345788.9 authorized patent):

[0027] The negative thermal expansion coefficient is (30-40)×10 -6 / ℃, can deform in the opposite direction to the concrete matrix, shrinkage rate at 60℃ ≥1.5%, can generate effective pre-compression stress (≥2.0MPa), interfacial bond strength ≥3.0MPa, stress transfer efficiency >85%, critical fiber spacing ≤2mm, can ensure superposition and coverage of compressive stress field;

[0028] Mechanism: When the internal temperature of concrete rises to 40-90℃, the matrix expands (+10x10 -6 / ℃) while the fiber shrinks (-35x10 -6 / ℃), forming a three-dimensional pre-compression network through interfacial shear stress.

[0029] 3. Porous micro-expansion fine lithium slag powder (marketable), specific surface area ≥ 500 m 2 / kg, can improve activity, form a nanoscale water reservoir, porosity ≥ 35%, can sustain internal curing, 90d expansion rate ≥ 0.02%, can delay the shrinkage of ettringite after compensation, ettringite formation peak 28-60d, matching the cold shrinkage period of concrete,

[0030] Ternary synergistic ratio design (kg / m 3 ):

[0031] Low-heat cement, 280-320 mass parts, can provide an early-strength matrix to control the source of temperature rise, lithium slag powder, 60-80 mass parts, dosage 20-25%, can play the dual effects of internal curing + delayed expansion, temperature shrinkage inducing fiber, 0.8-1.2 mass parts, volume fraction 0.3-0.5%, used to form a pre-compression network, aggregate (5-31.5mm gradation), 1800-1900 mass parts, tightly packed to reduce shrinkage voids, water-binder ratio 0.32-0.45, to ensure workability while reducing porosity;

[0032] Synergistic golden ratio: cement: lithium slag powder: fiber = 100: (20-25): (0.3-0.5) (mass ratio)

[0033] Key steps in the preparation method

[0034] 1. Material pretreatment process

[0035] Lithium slag activation: calcined at 800℃ and then finely ground to a specific surface area ≥ 500 m 2 / kg (activate nano-pores and active SiO2 / Al2O3)

[0036] Fiber premixing: dry mix fiber and lithium slag powder for 60s (porous structure adsorbs fiber to prevent agglomeration)

[0037] 2. Gradient mixing process (time control accurate to seconds)

[0038] Blender - cement + 70% water: high-speed stirring for 30s

[0039] Cement paste - lithium slag powder / fiber premixed body: medium-speed stirring for 60s

[0040] Gelled system - aggregate + remaining water + water reducing agent: low-speed stirring for 90s

[0041] Discharge - concrete: slump 180 ± 20 mm

[0042] 3. Temperature control maintenance system (cancel the cooling water pipe in the maintenance stage, implement three-stage temperature control maintenance)

[0043] 0-24h: cover insulation film (temperature difference ≤15℃), inhibit surface heat loss, 24-72h: spray maintenance (RH≥95%), activate lithium slag internal curing effect, 72h-90d: natural curing, promote delayed ettringite formation.

[0044] The above describes the best embodiment of the present application, wherein the parts not described in detail are all the common knowledge of ordinary skilled in the art. The protection scope of the present application is subject to the content of the claims, and any equivalent transformation based on the technical inspiration of the present application is also within the protection scope of the present application.

Claims

1. A method for preparing low-heat, high-crack-resistant large-volume concrete for ship locks based on ternary synergistic crack control, characterized in that, Includes the following steps: Step 1: Prepare cement raw materials, which include high early strength low heat cement with a mass ratio of 100:(20-25):(0.3-0.5), thermal shrinkage induced fiber and porous lithium slag powder, as well as aggregates and water-reducing agents. Step 2: The cement raw materials obtained in Step 1 are mixed using a gradient mixing process, and the mixed material is then poured to obtain a concrete billet. Step 3: Perform three-stage temperature-controlled curing on the concrete billet, including a 0-24h heat preservation stage, a 24-72h spraying stage, and a natural curing stage of more than 72 hours.

2. The method for preparing low-heat, high-crack-resistant large-volume concrete for ship locks based on ternary synergistic crack control according to claim 1, characterized in that, The thermo-shrinkable induced fiber has a negative coefficient of thermal expansion at 30-90℃, a shrinkage rate ≥1.5%, an initial shrinkage temperature of 30℃, and an interfacial stress transfer efficiency ≥85%.

3. The method for preparing low-heat, high-crack-resistant large-volume concrete for ship locks based on ternary synergistic crack control according to claim 1, characterized in that, The porous lithium slag powder underwent calcination at 800℃ and ultrafine grinding pretreatment, resulting in a specific surface area ≥500 m². 2 / kg, porosity ≥35%, 90d expansion rate ≥0.02%.

4. The method for preparing low-heat, high-crack-resistant large-volume concrete for ship locks based on ternary synergistic crack control according to claim 1, characterized in that, The gradient mixing process in step 2 includes the following steps: Step 2.1: Add the cement raw materials and water from Step 1 to the mixer and mix at high speed for 30 seconds to obtain cement slurry; Step 2.2: Add a premix of thermo-shrinkage induced fiber and porous lithium slag powder to the cement slurry and stir at medium speed for 60 seconds to obtain a cementitious system. Step 2.3: Add aggregate, water and water-reducing agent to the gelling system and stir at low speed for 90 seconds.

5. A low-heat, high-crack-resistance mass concrete for ship locks based on ternary synergistic crack control, characterized in that, It is prepared by any one of the methods in claims 1-4.