253.  For concreting the surface ofthe runways, roads and pavements, the aggregate impact value shall not exceedby weight
A.20%
B.25%
C.30%
D.45%

---

254.  Which one of the following tests, is used to test aggregate fonts abrasion resistance
A. Deval attrition test
B. Dorry abrasion test
C. Los Angeles test
D. All of these

---

255.  Pick up the correct statement from the following:
A. The property of expanding rocks more in direction parallel to one crystallograhic axis than another is called anisotropic property
B. The most anisotropic rock is calcite
C. The coefficeint of thermal expansion of aggregae is of prime importance for fire resistance of concrete
D. All the above

---

256.  The flankiness index of aggregates is the percentage by weight of particles in it whose thickness is less than
A. 2/5th of mean length
B. 3/5th of mean length
C. 4/5th of mean length
D. none of these

---

257.  Sea water:
A. contains a salinity of about 35 percent
B. corrodes the reinforcement of R0
C. acceleraes the setting time of cement
D. all the above

---

258.  Which one of the following pro; rties of plastic concrete is modified by the air-entraining agt-its
A. workability
B. segregation
C. bleeding
D. all of these

---

259.  Common sugar can be suitably used:
A. to delay the setting time of concrete
B. to accelerate the setting time of concrete
C. to increase the strength of concrete
D. none of these

---