A Self-Learning Manual - Institution of Engineers Mauritius

More documents

Recommendations

Info

A Self-Learning Manual Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU rainwater to the side of the road and avoid the occurrence of aquaplaning. In low speed roads the microtexture has particular significance in providing skid resistance by gripping the car tyres to the road surface. 10. What is the optimum binder content in bituminous pavement? (BM2) The amount of binder to be added to a bituminous mixture cannot be too excessive or too little. The principle of designing the optimum amount of binder content is to include sufficient amount of binder so that the aggregates are fully coated with bitumen and the voids within the bituminous material are sealed up. As such, the durability of the bituminous pavement can be enhanced by the impermeability achieved. Moreover, a minimum amount of binder is essential to prevent the aggregates from being pulled out by the abrasive actions of moving vehicles on the carriageway. However, the binder content cannot be too high because it would result in the instability of the bituminous pavement. In essence, the resistance to deformation of bituminous pavement under traffic load is reduced by the inclusion of excessive binder content. 11. How would high temperature affect the laying bituminous pavement? (T1) In general, bituminous materials are also broadly classified into two types, namely bitumen macadams and hot-rolled asphalts. During compaction, the increase of temperature causes the reduction of viscosity of binder. The binder acts as a lubricant among aggregates particles because it is mobile in a fluid state under high temperatures. The internal resistance between the bituminous materials is drastically reduced resulting in the formation of a mixture with better aggregate interlock. Bitumen macadams mainly contain continuously graded aggregates. Compaction of this type of bituminous material is eased with an increase of mix temperature as the lubricating effect of reduced viscosity of binder helps in the rearrangement of aggregates. The aggregate of hot-rolled asphalt are not well graded. With a rise in mixing temperature, the binder will stay unset and the mixture has little resistance to compaction [38]. 246
A Self-Learning Manual Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU 12. What is the desirable compacted thickness of bituminous pavement? (C2) The choice of compacted thickness is closely related to the nominal maximum size of aggregates of bituminous materials. Based on the recommendation by Dr. Robert N. Hunter [38], the rule of thumb is that the compacted layer thickness should exceed 2.5 times the maximum size of aggregate. If the layer thickness is less than 1.5 times the nominal maximum size of aggregates, the mechanical properties of bituminous material is impaired by the possible crushing of larger sizes of aggregates. Hence, controlled thickness of compaction of bituminous material should be clearly stated in works specification [38]. 13. What is the purpose of paving bituminous surfacing over concrete structures? The use of bituminous surfacing over concrete structures (e.g. existing concrete roads) is widespread to improve the skid-resistance and the general appearance of roads on one hand, and to avoid the pre-mature failure of concrete surface by frost spalling in cold countries on the other hand. In designing the bituminous surfacing over concrete, there are several areas to which engineers should pay attention. Firstly, the laying of thin bituminous material over the joints or existing cracks of concrete structure would lead to reflective cracking because the thermal movement of concrete induces swift formation of cracks in bituminous surfacing. Past research demonstrated that with the adoption of minimum thickness of 100mm bituminous surfacing the occurrence of reflective cracks would be delayed when compared with the use of thinner surfacing. Secondly, sufficient adhesion between concrete and bituminous surfacing has to be achieved. Therefore, it is recommended to apply a layer of tack coat on the concrete surface to promote bonding. 14. How do paver, steel-wheeled roller and pneumatic tire rollers carry out compaction? (C2) Paver, steel-wheeled roller and pneumatic tire roller compact bituminous material by using the following principles: (i) The static weight of the paving machines exerts loads on the bituminous material and compresses the material directly beneath the 247
Page 1 and 2:
A Self-Learning Manual Mastering Di
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196: A Self-Learning Manual Mastering Di
Page 245: A Self-Learning Manual Mastering Di
Page 297 and 298:
Page 299 and 300:
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317 and 318:
Page 319 and 320:
Page 321 and 322:
Page 323 and 324:
Page 325 and 326:
Page 327 and 328:
Page 329 and 330:
Page 331 and 332:
Page 333 and 334:
Page 335 and 336:
Page 337 and 338:
Page 339 and 340:
Page 341 and 342:
Page 343 and 344:
Page 345 and 346:
Page 347 and 348:
Page 349 and 350:
Page 351 and 352:
Page 353 and 354:
Page 355 and 356:
Page 357 and 358:
Page 359 and 360:
Page 361 and 362:
Page 363 and 364:
Page 365 and 366:
Page 367 and 368:
Page 369 and 370:
Page 371 and 372:
Page 373 and 374:
Page 375 and 376:
Page 377 and 378:
Page 379 and 380:
Page 381 and 382:
Page 383 and 384:
Page 385 and 386:
Page 387 and 388:
Page 389 and 390:
Page 391 and 392:
Page 393 and 394:
Page 395 and 396:
Page 397 and 398:
Page 399 and 400:
Page 401 and 402:
Page 403 and 404:
Page 405 and 406:
show all

A Self-Learning Manual - Institution of Engineers Mauritius

Create successful ePaper yourself

Delete template?

Save as template?