The foundation is the cornerstone that provides support and strength to an entire structure. It is responsible for even load distribution and withstanding environmental stresses to prevent settlement, failure, and resulting safety threats to the residents and the entire structure. However, foundation failure is a common problem that causes billions of dollars in damages and foundation repairs every year.
The quality of concrete is one of the major causes of foundation issues. Some builders prioritize speed and cost and neglect the complexities and capabilities of concrete during construction, leading to structural damage and a short foundation lifespan.
In this blog, KC Waterproofing - Overland Park’s foundation repair experts - highlight how the health and durability of a foundation depend on the quality of concrete used during construction. We explore the different factors that affect the quality of concrete, how they impact foundation health, and help us build a strong and stable structure.
The Basics of Foundations
The foundation is the first structure to be constructed in the process of raising a building. It provides the required support and stability and distributes the weight of the house equally around the ground to reduce the risk of structural damage. Foundation provides insulation, protecting the home from water infiltration, mold, mildew, and structural weakening. A concrete foundation also helps maintain a consistent indoor temperature and contributes to energy efficiency. A properly maintained foundation ensures structural stability and improves indoor air quality.
Slab, crawl space, and full basement are the most common types of foundation. The quality of concrete used affects the performance and durability of all types of foundations. Slab foundations are entirely composed of concrete and require strength to avoid shifting and cracking. Basements require concrete walls and floors that are both waterproof and strong to withstand water and moisture damage. Crawl spaces require concrete piers and footing for additional support. The quality of concrete affects the durability, resistance to environmental stresses, and longevity of all these foundation types. Poorly constructed concrete usually leads to structural issues and costly repairs.
Factors That Define Concrete Quality
Concrete is a widely preferred construction material for its exceptional compressive strength. It resists compressive forces and provides stability and support to any building structure. Concrete is composed of cement, water, fine aggregates such as sand, and coarse aggregates like gravel and crushed stone. The quality of concrete is determined by each of these components doing their part.
Key Components
Here are the key elements that affect the quality of concrete.
Cement Type and Content
High-quality cement ensures the stability of concrete foundations. Insufficient cement content compromises the workability and strength of concrete. Excessive cement leads to drying and shrinkage, which impair the concrete’s durability. The right amount of cement content ensures strength, workability, and optimal cost of concrete.
Water: Cement Ratio
A perfect blend of these components creates high-quality concrete. A low water-to-cement ratio results in strong concrete, but it can also turn into a dry, crumbly mess. A water-to-cement ratio of 0.5 is ideal for home construction as it offers both workability and strength. Using clean, potable water with a pH range of 6 to 8 prevents adverse reactions. Contaminants such as oil, alkali, acids, salts, and organic materials can cause corrosion and deterioration of concrete over time.
Aggregate Quality
The type and quality of aggregates also affect the strength and performance of concrete. Fine aggregates include natural sand and crushed stone that pass through a 4.75mm sieve. Fine aggregates fill the gaps between coarse aggregates, creating a denser and homogenous concrete. The aggregates should have optimal characteristics, including shape, size, and gradation, to improve concrete strength and longevity. Clean, well-graded aggregates reduce voids and provide strength, while dirty and poorly graded ones add weakness.
Admixtures
Additives such as plasticizers and accelerators are added to improve the performance of concrete. Some are used to decrease the amount of water, while others delay the setting time of concrete. Accelerating agents speed up the curing process.
Concrete Grading
Concrete is categorized by grades, such as M20 or M25, to indicate its compressive strength. M20 grade is generally used for residential buildings, while M25 is suitable for larger or commercial buildings that have to bear heavier loads.
Workmanship and Mixing
With different innovations, the mixing process of concrete has also changed. It is possible to mix the concrete on-site or get ready-mixed concrete. Field-mixed concrete is commonly used in residential projects, but it may lack consistency. Ready-mixed concrete is prepared in a controlled environment, offering reliability and consistency.
Curing Conditions
Curing is a critical step in construction that ensures the durability of the concrete. Proper moisture retention for 7 days ensures that concrete develops its full strength. Using wet burlap, plastic sheeting, or curing compounds helps prevent dehydration. The concrete must remain cool and moist each day to achieve peak strength and resilience, and prevent crumbling in the future.
Link Between Concrete Quality and Foundation Health
The quality of concrete used is directly linked to the strength and lifespan of a foundation.
Durability and Load-Bearing Capacity
Low-quality materials and improper mixing result in poor concrete foundations. Concrete with insufficient compressive strength has a lower load-bearing capacity and may collapse under stress. A good mix of fine and coarse aggregates can significantly boost compressive strength. High-quality concrete ensures that the structure can bear both static and dynamic loads over decades without faltering. By contrast, poorly mixed concrete weakens over time, making the structure susceptible to shifting.
Cracking and Settlement
Poor-quality concrete is often indicated by cracking and a settling foundation. It is caused by improper water-cement ratios or the use of low-grade aggregates during the construction. Such concrete cannot distribute the load evenly. Improper curing and inconsistent mixing add to the problem, allowing the foundation to sink or shift.
Moisture Ingress
Moisture ingress is another foundation problem, especially in areas with freeze-thaw cycles. Porous concrete allows water to seep in, freeze, and expand, causing surface scaling and internal fracturing. Over time, the concrete deteriorates, and the entire structure is compromised.
Resistance to Environmental Factors
Inferior quality concrete lacks the resistance to environmental factors such as sulfate attack in expansive soils and corrosion in coastal regions. Such chemical reactions slowly degrade the concrete, reducing strength and cohesion.
Substandard concrete might not show its impact immediately, but it causes long-term structural damage. It compromises the building’s safety, increases maintenance costs, and shortens the building’s lifespan.
Ensuring Concrete Quality in Construction
Homeowners and builders must ensure the quality of concrete long before the construction begins. The first step is to hire reputable contractors who provide reliable products and services. Request test reports for the slump test to assess workability and the cube compression test to evaluate strength.
Regular on-site checks are equally important to ensure a mixture with uniform texture, not overly wet or dry, and free of segregations. Make sure the workers follow mixing protocols during field-mixing. If you notice rapid setting or excessive water bleeding, it indicates poor concrete quality. Concrete that adheres to building codes and standards ensures further protection. They follow detailed guidelines for concrete mix, design, and testing.
The most crucial component is the accountability of the building contractors. They should oversee mixing, pouring, and curing processes and ensure compliance with third-party inspections. Trying to save money on supervision and testing leads to serious and expensive damage in the future.
Protect Your Foundation’s Health
Concrete is treated as a basic component in construction, but its quality has lasting effects on the strength, safety, and longevity of the building’s foundation. Any deviation in the materials’ quality, mixing process, or curing practices can lead to cracking, settlement, and foundation failure. Investing in high-quality concrete is not an expense but a safeguard for your property. Purchase materials that meet standards, ensure proper mixing and curing, and follow through with verified testing and oversight to build a strong, safe, and durable structure.
