CM 4563 Exam and Quiz Notes

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Louisiana State University *

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4563

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Mechanical Engineering

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Dec 6, 2023

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Grout is a mixture of Cementitious materials and aggregate (usually fine) with pouring consistency Which of the following statements about Fly ash is accurate? One of the effects of adding Fly ash to concrete is reducing slump loss. Which of the following statements regarding supplementary cementitious materials (SCM) is correct? Class C fly ash is considered a cementitious SCM. Which of the following statements on the stress-strain relation of concrete in compression and tension is accurate? The tensile strength of concrete is approximately 10% of its compressive strength. There are different types and sizes of voids inside concrete microstructures. Which voids are more influential in determining the strength and durability of concrete? Capillary voids larger than 50 nm Hook’s law defines __________ relationship for __________ materials. Stress-strain, linear elastic Which of the following statements is correct? Using Silica Fume as an SCM in concrete significantly improves early-age strength. What is the reason for adding approximately 5% gypsum during clinker grinding? To control early setting and hardening of the cement. Which of the following is one of the main disadvantages of concrete as a construction material? Poor ductility What is the required minimum compressive strength for high- strength concrete? 40 MPa Which of the following statements is accurate about concrete shrinkage? Shrinkage is associated with the loss of concrete moisture in the plastic and hardened state. A dry-rodded unit weight test was performed on an unknown gravel sample. A 7-liter metal bucket was used, oven dried aggregates were filled and rodded in 3 layers according to ASTM C29. The weight of the full bucket was 21.1kg, and the weight of the empty bucket was 6.2kg. What is the oven dry-rodded unit weight (DRUW) of this aggregate? (1 m 3 = 1000 liters) 2129 kg/m 3

How much water reduction is usually anticipated as a result of using water-reducing admixtures (WR)? 5% to 10% What are the main reasons for specifying aggregate grading limits and maximum aggregate size? Cost and workability Which of the following does not directly affect the dimensional stability of concrete? Workability Which statement about water-reducing admixtures (WR) and superplasticizers (HRWR) is accurate? Proper use of superplasticizers can lead to a workability increase, strength increase, and reducing the cement content in concrete. Concrete curing ____________. is essential to concrete strength development and durability Which of the following statements about concrete rheology is accurate? The rheology of fresh concrete is typically described using the Bingham model. In other words, the fresh concrete has a definite shear strength, which must be exceeded before flow can occur. Which statement about the aggregate absorption and surface moisture is accurate? Effective absorption is the moisture required to bring an aggregate from air dry to SSD conditions. What are the common side effects of adding Air-Entraining Admixtures to concrete? Increased workability and reduced strength Which of the following is NOT correct? With the progress of cement hydration, the porosity of the ITZ is reduced; thus, decreasing its strength. Which of the following test methods provides information on both strength and ductility of the tested material? Uniaxial Tensile Test (Japanese Society of Civil Engineers) Datum temperature is ___________. the temperature below which the concrete will show no increase in strength over time. Which of the following statements about the interfacial transition zone (ITZ) is NOT accurate? ITZ has less porosity and more un-hydrated cement particles compared to the bulk cement past. The Maturity method is based on the fact that __________. Cement hydration (and strength development) is a function of time and temperature

What is the reason for the higher flexural strength values obtained from ASTM C78 compared to the true tensile strength of concrete? Equations used in ASTM C78 are based on a linear elastic behavior for concrete. Which of the following statements about concrete’s response to stress is accurate? Concrete/mortar response to stress is affected by the presence of microcracks in the interfacial transition zone. The Brazilian test (splitting tensile test) __________. is carried out on a standard cylinder which is tested on its side in diametral compression. The “wall effect” refers to the fact that __________. Cement particles cannot pack efficiently around large aggregate particles. Which of the following cannot be considered a limitation of the Maturity method? Does not consider the effect of curing temperature on the strength The surface wear resistance of concrete is mainly affected by __________. water-to-cement ratio and aggregate type Which of the following statements about the permeability of hardened cement paste is accurate? In hardened cement paste, the size and continuity of the pores control the coefficient of permeability. Damage from corrosion of embedded steel occurs due to__________. All of these are reasons for corrosion damage of embedded steel. Which of the following is considered an effective measure to mitigate freeze-thaw damage? Air entrainment using closely spaced small air voids The corrosion mechanism requires __________. All of these are required for a corrosion mechanism.( a metallic connection, locations within the rebar with different electrochemical potentials (anode and cathode), and an electrolyte) All of the following are effective measures to control sulfate attack in concrete, except: Using Portland cement with high C 3 A content Which of the following statements on alkali-aggregate reactions is NOT correct? The use of supplementary cementitious materials can suppress all alkali-aggregate reactions.

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When a low-permeability aggregate is introduced in a high- permeability cement paste the permeability of the system increases due to which of the following? The microcracks in the interfacial transition zone, and the interconnections established by the propagation of the ITZ microcracks. The fire resistance of hardened cement paste mainly depends on __________. degree of hydration and moisture state Cavitation is a form of physical deterioration, defined as __________. None of these define( the damage by the abrasive action of fluids with solid particles in suspension, loss of mass by the formation of vapor bubbles and their subsequent collapse due to sudden change of direction in rapidly flowing water, dry surface attrition)s The surface wear resistance of concrete is mainly affected by water-to-cement ratio and aggregate type Which of the following statements about the permeability of hardened cement paste is accurate? In hardened cement paste, the size and continuity of the pores control the coefficient of permeability. Damage from corrosion of embedded steel occurs due to All (spalling, cracking, expansion) Which of the following is considered an effective measure to mitigate freeze-thaw damage? Air entrainment using closely spaced small air voids The corrosion mechanism requires All ( metallic connection, location within rebar with diff EP, an electrolyte) All of the following are effective measures to control sulfate attack in concrete, except: Using Portland cement with high C3A content Which of the following statements on alkali-aggregate is NOT correct? The use of supplementary cementitious materials can suppress all alkali-aggregate reactions

When a low-permeability aggregate is introduced in a high- permeability cement paste the permeability of the system increases due to which of the following? The microcracks in the interfacial transition zone, and the interconnections established by the propagation of the ITZ microcracks. The fire resistance of hardened cement paste mainly depends on degree of hydration and moisture state. Cavitation is a form of physical deterioration, defined as Loss of mass by the formation of vapor bubbles and their subsequent collapse due to sudden change of direction in rapidly flowing water Which of the following statements is accurate? Low-volume fraction FRC refers to FRC mixtures with less than 1% (by volume) fiber The following are the main design criteria for UPHC High particle packing density, low W/C, high steel fiber dosage, and max aggregate size of less than 0.8mm Which of the following statements on UHPC is NOT accurate? A minimum of 20 minutes of mixing is always required for UHPC mixtures to ensure a homogenous mixture Which of the following is the most commonly used fiber in structural FRC applications? Steel fiber The properties of fiber-reinforced concrete depend on all of the following EXCEPT: Fatigue life What does strain-hardening behavior refer to? The resistance continues to increase after the cracking stress is reached Which of the following statements on moderate-volume fraction FRC is NOT accurate? Commonly used to reduce shrinkage cracking

Advantages offered by Engineered Cementitious Composites (ECC) are mainly derived form the high tensile ductility of ECC and the intrinsically tight crack width Which of the following describes the cracking behavior of ECC under tensile load? Multiple cracks with width values under 100 micrometers Based on the ACI definition, ultra-high performance concrete is defined as concrete that has a minimum specified compressive strength of 150 MPa with specified durability, tensile ductility, and toughness requirements Which of the following statements on SCC rheology is accurate? SCC rheology is characterized by a low yield stress and moderate plastic viscosity The density of concrete can be significantly reduced by …. Replacing some of the solid material in the mix by air voids Which of the following is NOT considered a typical requirement for a self-consolidating mixture? Low desnity Which of the following statements on lightweight aggregates is NOT accurate? All of the lightweight aggregates used in structural lightweight concrete are manufactured aggregates What is the most common test method to evaluate the filling ability of a SCC mixture? Slump flow test (ASTM C1611) During production SCC is more sensitive to fluctuations in the total water content than vibrated concrete. Which of the following have been successfully applied for the production of SCC and to address this issue? Moisture probes (sensors) and manual drying tests Which test method is designed to evaluate the passing ability of SCC? L-box test

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Workability of SCC is described in terms of …. Segregation resistance, filling ability, and passing ability Structural lightweight aggregate concrete has a density value between … and a minimum 28-day compressive strength of … 1100-1900 kg/m3 ; 17 MPa What does the “SCC Passing Ability” refer to? The ease with which concrete can pass among various obstacles and narrow spacing in the formwork without blockage Construction 3D printing is an automated construction technology based on specially-designed cementitious mixtures and can only be used for on-site construction. False The main advantages of Contour Crafting (compared to conventional concrete construction) result from the fact that __________. This technology eliminates the need for formwork Fused deposition modeling is a 3D printing technology based on material extrusion and uses thermal energy. True Contour Crafting can be classified as a power bed fusion 3D printing technology. False The main sources of layer deformations during concrete 3D printing are __________. Self-weight, extrusion pressure, and weight of the following layers In concrete 3D printing, interlayer adhesion (bonding) can be negatively influenced by a prolonged interlayer time gap. True Which of the following is correct about Contour Crafting and Fused deposition modeling (FDM) 3D printing technologies? FDM is a thermal based process, while contour crafting uses cementitious materials which involve chemical reactions What are the main performance requirements of printable concrete? Extrudability and shape stability

Which of the following can result in a lower mechanical strength of 3D printed concrete, vs cast-in-place concrete with the same water-to-cementitious ratio? Excessive water evaporation Which of the following cannot be considered as an implementation barrier for construction-scale 3D printing (Contour Crafting)? Technical challenges (low construction speed) Which of the following material types is the most viable for Lunar and Martian construction using construction-scale 3D printing? In- situ materials such as lunar regolith or sulfur-based concrete Which of the following correctly describes the power source for each 3D printing category? Power bed fusion (power source: high-powered laser beam or electron beam)