QUALITY MANAGEMENT SYSTEMS IN CONCRETE CONSTRUCTION

Quality management systems in concrete construction should be the essential part of the construction project. Quality management system is nothing but a set of documents that provides detailed guidelines on quality management of concrete construction. It establishes systematic way of setting quality processes and roles and responsibilities and improving quality.

Need of quality management system:

Quality of concrete construction depends on many factors. From the selection of construction materials to the curing of the structural member, each and every step must be carried to maintain the quality requirement of the project. Any deviation from the required quality may result in failure of the structure or may impose penalty on the contractor for not maintaining the quality.

Quality of concrete construction includes steps for maintaining the required strength of concrete within the deviation permitted and construction of a durable structure. A concrete member may have the required strength just after the construction, but if it not compacted well, the surface may be porous, and corrosion of reinforcement starts which reduces the life span of the structure. So, durability should also be an important part of the construction management system.

The documents prepared for quality management of concrete construction should have step by step procedure for all the activities to be carried out during concrete construction. The standard document should also contain testing procedures for construction materials such as cement, sand, coarse aggregates and admixtures if required. The testing procedures for concrete during construction such as workability test.

The quality management system should have checklist for formwork, reinforcement, embedments, etc during construction stage.

Benefits of Concrete Quality Management Systems:

1. Quality of construction activities will be tracked by quality management documents and becomes a record for future reference.

2. Quality management system improves perception of customers towards company due to credible quality personnel and quality practices.

3. Good quality construction reduces the wastage of materials, smooth function of the team and keeps the construction cost within the limit.

4. It improve job-site concrete handling, curing, sampling and testing procedures to reduce potential liability to the company.

5. Minimize cost of repair and maintenance of the structure after construction due to quality works.

5. It opens the area of improvement for quality construction rationally based on the documents from previous projects.

 

SAFE BEARING CAPACITY VALUES OF DIFFERENT SOILS & ROCKS

 

The safe bearing capacity of soil should be determined on the basis of soil test data or by performing some field test such as Standard penetration test or Plate load test etc.

However, in the absence of soil test data, the values of safe bearing capacity (S.B.C) as given in the following table may be used as a guide for preliminary analysis.

RECOMMENDED VALUES OF SAFE BEARING CAPACITY FOR PRELIMINARY ANALYSIS
Sl. No	TYPE OF ROCK OR SOIL	SAFE BEARING CAPACITY
		(kN/m2)	(kg/cm2)
ROCKS
1	Rocks (hard) without lamination and defects, for example granite, trap and diorite	3300	33
2	Laminated rocks, for example sand stone and lime stone in sound condition	1650	16.5
3	Residual deposits of shattered and broken bed rock and hard shale, cemented material	900	9
4	Soft rock	450	4.5
NON-COHESIVE SOILS
5	Gravel, sand and gravel mixture, compact and offering high resistance to penetration when excavated by tools. (Refer Note 5)	450	4.5
6	Coarse sand, compact and dry (with ground water level at a depth greater than width of foundation below the base of footing)	450	4.5
7	Medium sand, compact and dry	250	2.5
8	Fine sand, silt (dry lumps easily pulverized by fingers)	150	1.5
9	Loose gravel or sand gravel mixture; loose coarse to medium sand, dry (Refer Note 5)	250	2.5
10	Fine sand, loose and dry	100	1
COHESIVE SOILS
11	Soft shale, hard or stiff clay in deep bed, dry	450	4.5
12	Medium clay, readily indented with thumb nail	250	2.5
13	Moist clay and sand clay mixture which can be indented with strong thumb pressure	150	1.5
14	Soft clay indented with moderate thumb pressure	100	1.0
15	Very soft clay which can be penetrated several centimeters with the thumb	50	0.5
16	Black cotton soil or other shrinkable or expansive clay in dry condition (50 percent saturation) (Refer Note 2)	To be determined after site investigation
17	Peat (Refer Note 2 & 3)
18	Fills or made up ground (Refer Note 4 & 5)

NOTES

1.       Values given in the above table can be adopted for design of unimportant and lightly loaded structures only.

2.       No generalized values for safe bearing capacities can be given for these types of soils. In such area, adequate site investigation is required to be carried out and expert advice should be sought.

3.       Peat may occur in a very soft spongy condition or may be quite firm and compact. While ultimate bearing capacity may be high in the compact cases, very large consolidation settlements occur even under small pressures and the movements continue for decades.

4.       The strength of made up ground depends on the nature of the material, its depth and age and methods used for consolidating it.

5.       Compactness or looseness of non-cohesive material may be determined by driving a wooden picket of dimension 5 cm x 5 cm x 70 cm with a sharp point. The picket is pushed vertically into the soil by full weight of a person and if the penetration of the picket exceeds 20 cm, then it considered as loose state.

6.       The safe bearing capacity value may be increased by an amount equal to weight of the material removed from above the bearing level that is the base of foundation.