5-41. Of the following basic setups for a  75-tph  crushing  plant,  which  one should be used when the bulk of material from a gravel deposit is 3 inches in diameter or less? 1. Jaw crusher 2. Primary unit only 3. Secondary unit only 4. Primary and secondary units together 5-42. The entire quarry and rock production operation depends on  improper  and  inadequate maintenance  of  equipment. 1. True 2. False Learning  Objective:  Recognize the properties of and uses for various types of cement that a concrete batch plant supervisor works with. 5-43. The chemical reaction between cement and water that produces concrete is known by what term? 1. Concrete 2. Hydraulics 3. Hydration 4. Evaporation 5-44. What type of cement requires less  protection  from  freezing and  attains  normal  3-day  strength in 1 day? 1. I 2. II 3. III 4. IV 5-45. Aggregates used in concrete occupy what percentage of the mix by weight? 1. Between 90% to 95% 2. Between 70% to 85% 3. Between 60% to 75% 5-46. Stockpiles for concrete aggregates 5-47. 5-48. 5-49. 5-50. should be built up in a cone shape. 1. True 2. False What condition results if the slope  inside  an  overhead  charging bin is less than 50 degrees? 1. Aggregates discharge too quickly 2. The bottom aggregates absorb too much water 3. Aggregates segregate when discharged 4. Aggregates combine too thickly What is the primary function of the water used in a concrete mix? 1. It wets the aggregates so the cement will bind 2. It  starts  the  hardening process (hydration) of the cement 3. It makes the mix workable 4. It prevents the cement from curing too fast When an air-entraining agent is used at a site, it is added to what element of a cement mix? 1. The aggregate for the mix 2. The concrete granules for the  mix 3. The water to be used in the mix 4. The cement to be used in the mix Which of the following materials can be used to retard the set of a concrete mix? 1. Borax 2. Sugar 3. Salt 4. Each of the above 4. Between 50% to 55% 37