Laboratory Facilities

The sampling and testing of concrete and concrete component materials are a critical aspect of our company’s quality assurance and quality control.

Our company operates a laboratory accredited to document our laboratory’s qualifications.

The NRMCA Concrete Laboratory Resource Guide, provides us with the information regarding the competency, documentation, and inspection requirements for various Laboratory Accreditations.

We keep quality records in the laboratory. Laboratory testing priorities are generally directed at those tests that are most important to the acceptance of concrete by our customer. Having the capabilities of testing fresh concrete and the strength (and other properties) of hardened concrete, are extremely important to our operations.

The NRMCA Concrete Laboratory Resource Guide includes a list of the tests that may be performed in a concrete materials laboratory, the test method for each test, and the equipment that is used in conducting the test as what we follow

Testing of ingredient materials such as aggregates, cementitious materials monitoring and water tests and frequencies.

Frequent trial mix being undertaken by our Laboratory for improving the quality
Collect branded raw materials from different sources to analyze and to implement if any changes required.
To make a research in ready mix concrete by using different kind of chemicals to Attain better results and to achieve cost reduction.
Review frequently the test results to confirm to make sure no shortfall in the Quality.
Invite the experts to help our staff in development of our quality program.
In-house testing for strength mixes
Our ready-mix-concrete is subjected to ongoing testing in our purpose built controlled accredited laboratory.
Samples ofready-mix-concrete are, on a daily basis, poured from all our mixers and placed in our laboratory. The samples of concrete are slump tested and then poured in to calibrated cube moulds. These are then placed in curing tanks until they are collected on a weekly basis by a third party accredited testing house.

The strengths of the ready-mix-concrete recorded are constantly monitored and the results achieved determine the future amount ofcement that we put in to our strength concrete mixes.
The accreditation that the company holds enables the company to produce and sell concrete by strength mixes. These strength mixes range from C10 to C50. See all our design strengthmixes.

Concrete Material Basics

Concrete is basically a mixture of two components: aggregates and paste (or binder). The paste is comprised of cement, supplementary cementitious materials and water. It binds the aggregates (sand and gravel or crushed stone) into a rocklike mass. The chemical reaction of the cementitious materials and water, called hydration, is the process by which paste hardens and binds the aggregates.

Aggregates

Aggregates are generally divided into two groups: fine and course. Fine aggregates consist of natural or manufactured sand with particle sizes ranging from dust-size up to 3/8 inch; coarse aggregates are those with particles ranging in size from 6 in. down to about 0.05 in. For pavement, it is common for the maximum aggregate size to range from 1 to 1.5 in. Aggregates are sized by passing them through screens with standard openings called sieves.

Selection of aggregates for use in concrete is important since they make up about 60% to 75% of the total volume of concrete.

Aggregates should consist of particles with adequate strength and resistance to exposure conditions and should not contain materials that will cause a chemical reaction with the paste that may lead to deterioration of the concrete. Screening tests are available to determine the adequacy of aggregates for use in concrete.

Cut away of concrete showing Aggregate and Paste

Cement Paste

The paste is composed of portland cement, supplementary cementitious materials (fly ash), water, and entrapped air or purposely entrained air. Cement paste ordinarily constitutes about 25% to 40% of the total volume of concrete. The volume of cement is usually between 7% and 15% and the water between 14% and 21%. Air content ranges up to about 8% of the volume of the concrete.

There are many different types of cement, including Portland cement and blended hydraulic cement. ASTM C150 and AASHTO M85 classify Portland cements by five chemical and compositional designations: Type I through Type V. ASTM C 595 and ASTM C 1157 classify blended hydraulic cements. Blended cements contain additional ingredients, such as fly ash, or blast furnace slag directly in the cement. Presently, most concrete for use in pavement is made with a Portland cement, but use of blended hydraulic cements appears to be increasing.

Concrete Quality

The quality of any concrete is dependent upon the ratio of the quantity of water used to the quantity of cementitious materials used in the mixture (called the water-cement ratio or water-cementitious ratio). In general, concrete with a lower water-cementitious ratio is stronger and less permeable, thus more durable.

The freshly-mixed and hardened properties of concrete may be changed by adding liquid or mineraladmixtures to the concrete, during batching. Admixtures are commonly used to (1) adjust setting time or hardening, (2) reduce water demand, (3) increase workability, (4) intentionally entrain air, and (5) adjust other concrete properties, such as strength.

Air bubbles are entrained in concrete using an air-entraining admixture. The tiny microscopic bubbles provide free space within the paste to relieve hydraulic pressure when concrete freezes. Without the bubbles, the paste may crack when it freezes because water expands 9% in volume when it turns to ice. With entrained air, there is free space within the concrete to relieve pressure in the paste during freezing.

There is also some air – entrapped air – that gets trapped in the concrete during mixing. In general, entrapped air voids are much larger than entrained air bubbles and provide no real benefits. Any concrete with a large number of entrapped air voids will probably have lower strength and durability. Entrapped air is often the result of a very harsh or sticky mixture and/or lack of effort in consolidating a mixture.

Consistency

Workability is the ease of placing, consolidating, and finishing freshly mixed concrete. In general, freshly mixed concrete is plastic or semi-fluid with the consistency of thick mud. However there are degrees of plasticity necessary for different uses of concrete. This consistency is often measured by the slump of the concrete. Paving concrete has usually a low-slump (stiff consistency.)

Consolidation is the process of inducing a closer arrangement of the solid particles in freshly mixed concrete. During consolidation entrapped air is removed from the concrete. For most pavement construction processes hand-held or paving machine vibrators impart energy on concrete to achieve consolidation. The vibrators operate at a high frequency and set aggregate particles into motion in freshly mixed concrete, reducing friction between them and giving the mixture the qualities of a thick fluid. This allows the concrete to flow easily through a slipform paver, and around reinforcing steel, dowel baskets and other embedded fixtures.

Slump Test after Removing the Cone

Strength

Concrete pavement strength is usually evaluated in compression or in flexure. These values are called compressive strength and flexural strength and are determined using standardized tests.

For compressive strength, imagine placing a small sample of concrete in a vise and squeezing until it breaks. If you measure the squeezing (compressing) force necessary to break the concrete and divide by the contact area of the specimen, you will determine the compressive strength. It is generally expressed in pounds per square inch (psi) at an age of 28 days. (Concrete continues to gain strength with age. To account for this, the strength used in designing and specifying concrete is measured at 28 days.)

To determine compressive strength, tests are made on cylinders, which are often sized at 6 inches in diameter and 12 inches high. Most paving-grade concrete has a compressive strength between 3000 psi and 5000 psi. High-strength concrete has a compressive strength of at least 6000 psi and compressive strengths of 20,000 psi have been used in building applications.

Flexural strength is the strength of concrete to bending. Consider the action of holding each end of a pencil and bending the pencil until it breaks. This is an example of placing a structure in bending (flexure). In designing concrete pavements, flexural strength is often used because it better simulates what happens when a slab is loaded by a truck or other vehicle. Another term for the flexural strength is the modulus of rupture. Most general-use concrete has a flexural strength between 500 psi to 700 psi.

RESEARCH:

Frequent trial mix being undertaken by our Laboratory for improving the quality
Collect branded raw materials from different sources to analyze and to implement if any changes required.
To make a research in ready mix concrete by using different kind of chemicals to Attain better results and to achieve cost reduction.
Review frequently the test results to confirm to make sure no shortfall in the Quality.
Invite the experts to help our staff in development of our quality program.