--- title: "Failures of rigid pavement" subject: "Transportation Engineering II" chapter: 4 key: "semester_7/transportation_engineering_ii:rigid-pavement-failures" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/rigid-pavement-failures site: BCT Engineering --- # Failures of rigid pavement Transportation Engineering II · Chapter 4: Highway Maintenance, Repair, and Rehabilitation - Asked in: 2070 Chaitra (old course), 8 marks; 2068 Baisakh, 4 marks (asked 2 times) - Video: [CE 308 TE 1 MODULE IV FAILURES IN FLEXIBLE AND RIGID PAVEMENTS](https://www.youtube.com/watch?v=wBOvy3S4ZgQ) — Toc H Kochi - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/rigid-pavement-failures - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-4 ## Question What are the causes that result the failure of cement concrete pavement? Explain briefly. ## Short answer Rigid pavement failures include transverse cracking (late sawing, thin slab), longitudinal cracking (differential settlement), corner breaks (unsupported corner), faulting (pumping), spalling (incompressibles in joints), blow-ups (blocked expansion joints), and scaling (poor curing). Water entry, poor load transfer, and heavy loads are common underlying causes. ## Answer #### Failures of cement concrete pavement and their causes Typical types of failure of a cement concrete pavement, with their causes: | Failure | Description | Cause | |---|---|---| | **Transverse cracking** | Cracks across the slab | Late sawing of joints, joint spacing too long, thin slab, restrained shrinkage | | **Longitudinal cracking** | Cracks along the lane | Differential settlement, warping, thin slab, poor subgrade support | | **Corner break (corner crack)** | Triangular piece at the corner within 1.5 m of joint | Load at unsupported corner, loss of support (pumping), poor load transfer | | **Diagonal cracking** | Crack at about 45 degrees | Heavy corner loads, settlement | | **Punch-out / shattered slab** | Slab breaks into many pieces | Heavy repeated loads, weak sub-base | | **Faulting** | Step between slabs at a joint | Pumping, poor load transfer (dowel failure) | | **Pumping** | Ejection of water and fines at joints | Water under slab, loose subgrade, heavy traffic | | **Spalling** | Breaking of joint edges | Incompressible material in joints, weak concrete, dowel misalignment | | **Blow-up (buckling)** | Slab lifts and shatters in hot weather | Blocked expansion joints, insufficient expansion gap | | **Scaling and crazing** | Flaking and map cracks on surface | Over-finishing, poor curing, freeze-thaw | | **Joint seal failure** | Sealant loss, weeds | Aged sealant, poor installation | ```text Faulting at a joint Corner break ______ +-------------+ ______| step | | joint | | | crack -> / +-----------/-+ ``` Remedies include full-depth repair, slab replacement, dowel retrofit, grinding of faults, crack and joint resealing, undersealing (grout) to fill voids, and improving drainage. #### General causes - **Design:** inadequate slab thickness, joint spacing too long, poor load transfer, insufficient sub-base. - **Construction:** poor compaction, honeycombing, late joint cutting, wrong dowel alignment, inadequate curing, poor quality concrete. - **Traffic:** overloading, repetitions beyond design. - **Drainage and subgrade:** water entering through joints causes pumping; soft subgrade settles. - **Environment:** temperature and moisture cycles (warping, blow-ups). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is a typical cause of transverse cracking in a concrete pavement? A. Blocked expansion joints B. Late sawing of joints or joint spacing too long C. Ageing of sealant D. Freeze-thaw only Answer: B. Late joint cutting, long joint spacing, thin slab and restrained shrinkage cause cracks across the slab. (Key point: Transverse cracking cause) 2. Blow-up (buckling) occurs because: A. Joints are blocked or have insufficient expansion gap, in hot weather B. Concrete is over-finished C. Dowels are misaligned D. Sub-base is too thick Answer: A. Expansion of slabs against blocked or too-narrow joints makes them lift and shatter. (Key point: Blow-up) 3. Pumping is: A. Ejection of water and fines at joints under traffic with water under the slab B. Flaking of the surface C. Triangular cracking at corners D. Waves across the slab Answer: A. Water and fines are forced out at joints, causing loss of support and faulting. (Key point: Pumping) 4. Spalling of joint edges is caused by: A. Incompressible material in joints, weak concrete or dowel misalignment B. Late sawing C. Thin subgrade D. High CBR Answer: A. Incompressible material in joints, weak concrete and dowel misalignment break the joint edges. 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