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Key Facts: Engineer Concrete Exam

80 items

Official written paper length (4 subjects × 20)

Q-Net Engineer-grade grading method; Q-Net 콘크리트기사 page

120 minutes

Written timing at 30 minutes per subject

Q-Net 필기시험 접수안내 (기사·산업기사 과목별 30분)

40 / 60

Written per-subject floor and overall average

Q-Net 검정기준 및 방법 (기사)

KRW 19,400

Written registration fee on the Q-Net 콘크리트기사 page

Q-Net crf005 jmCd=1048, checked 2026-09-20

KRW 57,100

Practical registration fee on the Q-Net 콘크리트기사 page

Q-Net crf005 jmCd=1048, checked 2026-09-20

2 years

Written-pass exemption period from the pass date

National Technical Qualifications Act Enforcement Decree Article 21

콘크리트기사 is HRD Korea's Engineer-grade concrete qualification under MOLIT. The written paper features 80 four-option items across four subjects (20 each, 120 minutes total), requiring at least 40 points per subject and a 60% overall average. Passing candidates take a composite practical exam (2-hour written response + 4-hour laboratory testing). Official fees are KRW 19,400 written and KRW 57,100 practical. OpenExamPrep provides an independent English-language MCQ practice bank for written preparation.

Sample Engineer Concrete Practice Questions

Try these sample questions to review concepts for the Engineer Concrete exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which of the primary clinker minerals in Portland cement exhibits the highest rate of hydration reaction and generates the greatest amount of early heat of hydration (수화열)?
A.Tricalcium aluminate (C3A, 알루민산삼칼슘)
B.Tricalcium silicate (C3S, alite, 규산삼칼슘)
C.Dicalcium silicate (C2S, belite, 규산이칼슘)
D.Tetracalcium aluminoferrite (C4AF, ferrite, 철알루민산사칼슘)
Explanation: Tricalcium aluminate (C3A) reacts instantaneously with water, releasing approximately 866 J/g (207 cal/g) of hydration heat, which is significantly higher than C3S (~502 J/g), C4AF (~419 J/g), and C2S (~260 J/g). Gypsum is specifically interground with clinker in cement manufacturing to retard this rapid C3A hydration and prevent flash setting.
2During the grinding of Portland cement clinker, what is the primary technical objective of intergrinding calcium sulfate dihydrate (gypsum, 석고)?
A.To prevent flash setting (순결) by reacting with tricalcium aluminate (C3A) to form insoluble ettringite
B.To accelerate the hydration rate of dicalcium silicate (C2S) and enhance 3-day compressive strength
C.To lower the alkali content (Na2O equivalent) and prevent alkali-silica reaction (ASR)
D.To reduce the specific surface area (Blaine fineness) of the finished Portland cement
Explanation: Without gypsum, tricalcium aluminate (C3A) hydrates violently upon contact with water, producing instantaneous stiffening known as flash set (순결). Gypsum (CaSO4·2H2O) dissolves rapidly to provide sulfate ions that react with aluminate ions to precipitate a protective needle-like coating of ettringite (AFt phase) on the C3A surfaces, retarding the reaction to a workable dormant period.
3According to KS L 5201 (Portland Cement), which type of cement is specifically formulated with a high dicalcium silicate (C2S) content and strictly limited tricalcium aluminate (C3A) content to minimize thermal cracking in massive civil structures?
A.Type IV Low-heat Portland cement (저열 포틀랜드 시멘트)
B.Type III High-early-strength Portland cement (조강 포틀랜드 시멘트)
C.Type I Ordinary Portland cement (보통 포틀랜드 시멘트)
D.Type V Sulfate-resisting Portland cement (내황산염 포틀랜드 시멘트)
Explanation: Type IV Low-heat Portland cement (저열 포틀랜드 시멘트) contains 45-55% C2S and limits C3A to 4-7% (or lower), generating significantly lower adiabatic temperature rise. This makes it ideal for mass concrete foundations, gravity dams, and thick bridge piers where thermal stress cracking must be mitigated.
4In precast concrete production and emergency repair operations requiring rapid formwork cycle times, Type III High-early-strength Portland cement (조강 포틀랜드 시멘트) is frequently selected. What two physical and chemical characteristics primarily govern its rapid strength development?
A.Higher tricalcium silicate (C3S) content and higher Blaine specific surface area (>= 3,300 cm2/g)
B.Higher dicalcium silicate (C2S) content and lower Blaine specific surface area
C.Higher tetracalcium aluminoferrite (C4AF) content and coarser particle size distribution
D.High limestone filler replacement and reduced gypsum content
Explanation: Type III cement attains in 3 days the approximate compressive strength that Type I cement reaches in 7 days. This rapid hardening is achieved through elevated alite (C3S) concentration combined with finer grinding (Blaine specific surface area typically 4,000-5,000 cm2/g, with KS L 5201 requiring >= 3,300 cm2/g), dramatically increasing the surface area available for early hydration.
5Which statement correctly describes the performance attributes and hydration mechanism of Portland blast-furnace slag cement (고로슬래그 시멘트, KS L 5210)?
A.The granulated blast-furnace slag exhibits latent hydraulicity (잠재수경성), activated by Ca(OH)2 from clinker hydration to produce dense C-S-H with high sulfate resistance and low permeability
B.The slag reacts instantly with water upon mixing without needing any chemical activator or Portland clinker hydration products
C.It releases significantly higher early heat of hydration than Type I cement, making it unsuitable for warm-weather construction
D.It develops high 1-day early strength but suffers from severe strength loss after 91 days of moist curing
Explanation: Ground granulated blast-furnace slag (GGBS) has latent hydraulicity (잠재수경성). It does not hydrate quickly alone because of a protective aluminosilicate glass film; however, calcium hydroxide (Ca(OH)2) and alkalis released by Portland clinker hydration break down this glass network, forming supplementary calcium silicate hydrate (C-S-H) that densifies the matrix, lowers permeability, and provides superior resistance to chloride and sulfate attack.
6When the Blaine specific surface area (분말도) of Portland cement increases from 3,000 cm2/g to 4,500 cm2/g while maintaining chemical composition, how are the properties of fresh and hardened concrete affected?
A.The initial hydration rate and early strength increase, but standard water demand and drying shrinkage also increase
B.The initial hydration rate decreases, water demand decreases, and bleeding increases substantially
C.Drying shrinkage decreases significantly because finer particles reduce total capillary porosity without affecting water demand
D.Early compressive strength is unchanged, but 91-day ultimate strength decreases by more than 30%
Explanation: Finer cement particles offer greater specific surface area for contact with water, speeding up early hydration, accelerating setting, and increasing 1- to 7-day strength. However, the greater surface area demands more water to maintain a given slump, increases chemical and autogenous shrinkage, and tends to heighten long-term drying shrinkage.
7In aggregate testing and mix proportioning calculations (골재의 수분상태), which moisture condition is defined as the state where all internal permeable pores of the aggregate particles are filled with water while the exterior surfaces are completely dry?
A.Saturated surface-dry state (표면건조포화상태, SSD)
B.Oven-dry state (절대건조상태 / 절건상태)
C.Air-dry state (공기건조상태 / 기건상태)
D.Wet / moist state (습윤상태)
Explanation: The saturated surface-dry (SSD, 표면건조포화상태) state is the fundamental reference datum for concrete mix proportioning in Korean Construction Standards (KCS 14 20 10) and KS F standards. In this state, aggregate neither absorbs mixing water from the fresh paste nor contributes surplus surface water to it.
8A fine aggregate sample obtained from a ready-mixed concrete plant batching bin has a total moisture content (함수율) of 5.4% and an absorption capacity (흡수율) of 1.8%. What is the surface moisture ratio (표면수율) of this sand?
A.3.6%
B.7.2%
C.0.97%
D.1.8%
Explanation: Surface moisture ratio (표면수율) is the free water on particle surfaces that contributes to the mixing water. It is calculated directly as total moisture content minus absorption capacity: Surface Moisture (%) = Total Moisture (%) - Absorption (%) = 5.4% - 1.8% = 3.6%.
9A sieve analysis test is performed on a 500 g dry sample of fine aggregate according to KS F 2502. The cumulative percentages retained on the standard sieves are: 10 mm: 0%, 5 mm: 0%, 2.5 mm: 6%, 1.2 mm: 22%, 0.6 mm: 54%, 0.3 mm: 82%, and 0.15 mm: 96%. What is the fineness modulus (조립률, FM) of this fine aggregate?
A.2.60
B.2.85
C.3.15
D.2.35
Explanation: Fineness modulus (조립률, FM) is defined as the sum of the cumulative percentages retained on the ten standard sieves (75, 40, 20, 10, 5, 2.5, 1.2, 0.6, 0.3, and 0.15 mm) divided by 100. For fine aggregate: FM = (0 + 0 + 0 + 0 + 0 + 6 + 22 + 54 + 82 + 96) / 100 = 260 / 100 = 2.60. This falls within the KS F 2526 standard fine aggregate range of 2.3 to 3.1.
10A concrete mix proportion uses fine aggregate with a fineness modulus (FM_s) of 2.60 and coarse aggregate with a fineness modulus (FM_g) of 7.00. If the sand-aggregate ratio by absolute volume is S/a = 42% (with coarse aggregate proportion G/a = 58%), what is the combined fineness modulus (FM_c) of the total aggregate blend?
A.5.15
B.4.80
C.5.62
D.4.44
Explanation: The combined fineness modulus of an aggregate blend is calculated using the weighted linear combination: FM_c = FM_s × (S/a) + FM_g × (G/a) = (2.60 × 0.42) + (7.00 × 0.58) = 1.092 + 4.060 = 5.152 ≈ 5.15. This weighted average verifies the overall grading of the aggregate skeleton.

About the Engineer Concrete Exam

Engineer Concrete (콘크리트기사) is South Korea's premier professional technical qualification in concrete technology, administered by the Human Resources Development Service of Korea (HRD Korea / Q-Net) under the Ministry of Land, Infrastructure and Transport (MOLIT). The written examination evaluates comprehensive engineering mastery across four subjects: concrete materials and mix design, manufacturing/testing/quality control, site construction and special concretes, and structural mechanics and maintenance. Passing candidates proceed to a rigorous composite practical examination combining written descriptive problem-solving and hands-on laboratory testing (slump, air content, compressive strength, and mix calculations). This OpenExamPrep study module provides an independent English-language MCQ practice bank adapted to help engineers and candidates master the theoretical, computational, and regulatory standards of KCS and KS F.

Exam sponsor: HRD Korea (Q-Net) / Ministry of Land, Infrastructure and Transport (MOLIT). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Written paper covering 콘크리트재료 및 배합, 콘크리트제조·시험 및 품질관리, 콘크리트의 시공, and 콘크리트구조 및 유지관리 (20 items and 30 minutes each, total 80 items and 120 minutes), followed by a composite practical examination (필답형 ~2 hours, 60 pts + 작업형 ~4 hours, 40 pts). OpenExamPrep study weights match the four equal written subjects (25% each).

Time Limit

120 minutes for the four written subjects (30 minutes each); practical: composite (written response ~2 hours + laboratory testing ~4 hours)

Passing Score

Written: 40+ per subject and 60 average out of 100; practical: 60+ out of 100

Exam / Certification Fees

KRW 19,400 written / KRW 57,100 practical (Q-Net, 2026-09-20)

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

25%

Concrete Materials and Mix Design (콘크리트재료 및 배합)

Portland cements (Types I-V) and blended cements (blast-furnace slag, fly ash, silica fume), aggregate properties (density, absorption, fineness modulus FM, grading, ASR), mixing water quality, chemical admixtures (AE agents, superplasticizers, retarders), and mix proportion calculations using the absolute volume method.

25%

Concrete Manufacturing, Testing, and Quality Control (콘크리트제조, 시험 및 품질관리)

Ready-mixed concrete batching and mixing tolerances (KS F 4009), transport time limits (90 minutes), fresh testing (slump KS F 2402, air content KS F 2421, bleeding, setting time KS F 2436), mechanical testing (compressive KS F 2405, tensile KS F 2423, flexural KS F 2408), non-destructive testing (rebound hammer, ultrasonic pulse velocity), and statistical QC (X-R control charts, cumulative difference method).

25%

Concrete Construction (콘크리트의 시공)

Conveyance and pumping, concrete placement and compaction (internal vibrator insertion protocols), construction joints and waterstops, finishing and curing protocols, lateral formwork pressure and stripping criteria, and special concretes (mass concrete, cold-weather concrete, hot-weather concrete, underwater tremie concrete, high-strength concrete, and shotcrete).

25%

Concrete Structures and Maintenance (콘크리트구조 및 유지관리)

Reinforced concrete flexural, shear, and torsional behavior, crack control criteria, deterioration mechanisms (carbonation depth x = C√t, chloride ingress threshold, freeze-thaw durability factor, alkali-aggregate reaction, sulfate attack), diagnostic evaluation (half-cell potential, cover depth), safety evaluation grades (A through E), and retrofitting methods (epoxy injection, patch repair, cathodic protection, steel plate and CFRP bonding).

Preparing for the Engineer Concrete Exam

What You Need to Know

  • Passing score: Written: 40+ per subject and 60 average out of 100; practical: 60+ out of 100
  • Assessment: Written paper covering 콘크리트재료 및 배합, 콘크리트제조·시험 및 품질관리, 콘크리트의 시공, and 콘크리트구조 및 유지관리 (20 items and 30 minutes each, total 80 items and 120 minutes), followed by a composite practical examination (필답형 ~2 hours, 60 pts + 작업형 ~4 hours, 40 pts). OpenExamPrep study weights match the four equal written subjects (25% each).
  • Time limit: 120 minutes for the four written subjects (30 minutes each); practical: composite (written response ~2 hours + laboratory testing ~4 hours)
  • Exam / certification fees: KRW 19,400 written / KRW 57,100 practical (Q-Net, 2026-09-20) Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

Engineer Concrete: Suggested Study Strategy

1Master mix design calculations (absolute volume method) thoroughly: calculate water-binder ratio (W/B), unit water content (W), unit cement content (C), and fine/coarse aggregate weights (S and G) without relying on formula sheets.
2Understand the 40-point per-subject passing floor (과락): allocate balanced study time across all four subjects to avoid failing on a single weak section despite a high overall score.
3Memorize key threshold values from Korean Construction Standards (KCS): e.g., truck agitator transit limit (90 minutes), cold-weather critical compressive strength (5 MPa), maximum placement temperature for hot-weather concrete (35°C), and water chloride limit.
4Connect theoretical concepts to laboratory testing: pay special attention to standard testing procedures (KS F 2402 slump, KS F 2421 air content, KS F 2405 compressive strength, phenolphthalein carbonation testing) as they appear heavily in both the written exam and practical stages.

Frequently Asked Questions

What is Engineer Concrete (콘크리트기사)?

Engineer Concrete (콘크리트기사) is a national technical qualification certified by HRD Korea under the authority of the Ministry of Land, Infrastructure and Transport (MOLIT). It certifies professional expertise in concrete design, quality control, manufacturing, site construction management, structural assessment, and concrete facility maintenance.

How is the official 2026 examination structured?

The examination is divided into two distinct stages: (1) Written Examination: 80 multiple-choice questions (20 items across 4 subjects) conducted in a 120-minute CBT/PBT session. Candidates must score at least 40 points in each subject (과락 floor) and an overall average of 60 points or higher. (2) Practical Examination: A composite examination (복합형) consisting of a written-response test (필답형, approx. 2 hours, 60 points) and a hands-on laboratory testing exam (작업형, approx. 4 hours, 40 points), requiring 60 points or higher to pass.

What are the official fees and practical test components?

As verified on Q-Net (jmCd 1048), the written examination fee is KRW 19,400 and the practical examination fee is KRW 57,100. The laboratory testing session (작업형) typically tests candidate execution of slump testing (KS F 2402), air content determination by pressure method (KS F 2421), fresh concrete unit mass, compressive specimen preparation and capping, and mix design computation.

What language is the official examination, and how should this practice bank be used?

The official Q-Net examinations are administered entirely in Korean. This OpenExamPrep question bank provides an independent English-language study adaptation with authentic technical Korean terms in parentheses, designed to help candidates, international engineers, and students master the underlying engineering principles, KCS/KS F specifications, and quantitative problem-solving skills.

How long is a written exam pass valid for the practical exam?

Under Article 21 of the National Technical Qualifications Act Enforcement Decree, candidates who pass the written examination are granted a 2-year exemption from the written test starting from the date the written pass is officially announced, during which they may register for and sit the practical examination.