Trivias and Infographics

How To Speed Up Concrete Curing

What is Concrete Curing?
Concrete Curing is the process of keeping hydration inside the concrete to ensure that the chemical reaction between cement and water that binds sand and aggregates together is completed. Curing helps the concrete to harden and bond with internal materials and reinforcement. It delays drying shrinkage until the concrete is strong enough to resist shrinkage cracking.
What are the ways to speed up the curing of concrete?
1.Sunny weather- concreting in a sunny weather is desirable since high temperature encourages the curing of concrete
2. Add warm water- warm water in concrete mix can increase the speed of chemical reactions in concrete. However, be careful to not put blazing hot water that may damage the concrete.
3. Add Calcium Chloride- Calcium Chloride is used as an accelerator in the hydration process of cement which can increase the setting time of concrete and initial strength.
4. Reduce Water cautiously- Reduce water cautiously by adding water-reducing mixture or finding the right amount of water to add to the mix by consulting with a specialist company who can offer some insight.
5. Proper Trowelling- High intensity trowelling can cause the air pockets and vents in the concrete to collapse, therefore preventing the moisture from easily evaporating.
6. A plastic cover- Covering recently poured concrete with a plastic sheet can keep the moisture intact within the concrete and accelerate the curing process.

Types of Cement Under the Microscope

Several types of cement are characterized under the microscope based on the presence and abundance of certain cement minerals.

Standard Cement/ Portland Cement
-Relatively coarse-grained alite (C3S) grain often many and large agglomerates of belite (C2S) and ferrite (C4AF) .

Rapid Hardening Cement (ASTM Type III)
-Looks like Portland Cement but more fine grained and generally no agglomerates of belite (C2S) present. Often a high amount of Hadley holes. It is a certain type of Portland cement typically used in concrete construction to develop high strength earlier than Ordinary Portland Cement (OPC).

White cement
-contains alite (C3S), minor belite (C2S) and only very little ferrite (C4AF), making the paste looks white. Also known as snowcrete. It is the same as ordinary gray Portland cement except in respect to color and fineness.

Aluminate Cement
- is based on aluminate (and ferrite) giving the paste an orange color.

Bacterial Concrete: Living Building Materials

Researchers from the University of Colorado has created self-reproducing concrete called Living building materials (LBMs). The living concrete is made by mixing cyanobacteria with warm water, sand, and nutrients. The photosynthetic cyanobacteria eagerly absorbed the light and nutrients and began producing calcium carbonate which cemented the sand particles together. The cyanobacteria mixture can also form concrete blocks in the shape of whatever mold the research team used. These materials are capable of exponential regeneration.

When the concrete blocks are stored in a relatively dry room temperature, the bacteria die out and the blocks reach their maximum strength. The blocks need to be exposed to high temperature and humidity for the bacterial cells to come back to life. In addition to this, the blocks are naturally green, truly like a Frankenstein concrete. The research team is currently working on making the concrete stronger; re-configuring the materials so they can be flat-packed and easily assembled, like slabs of drywall; and finding a different kind of cyanobacteria that doesn’t require the addition of a gel.

Bacterial Concrete: Bio-Concrete

Cracks in concrete are inevitable. Microcracks present in concrete allow liquids to seep through causing corrosion and deterioration of concrete. Therefore, researchers are studying the development of self-healing concrete using biomaterials. One example is the Bio-concrete, developed by Dutch Researcher and microbiologist Hendrik Jonkers.

How does the self-healing concrete work?

Bacteria with calcium nutrient source (bacteria from genus Bacillus) in a microcapsule is added into concrete during mixing. Any microcracking that occurs will be sealed by the calcium carbonate precipitated by the bacteria. The bacteria also consume oxygen which prevents the internal corrosion of reinforced concrete. The strength and durability of bio-concrete is being tested under various conditions in Breda, the Netherlands since there is evidence that this biotechnological method based on calcite precipitation can reduce maintenance and increase the durability of concrete.

Magnetized Cement That Can Charge Electric Cars

The Indiana Department of Transportation and Purdue University recently announced plans to develop a highway capable of charging electric cars wirelessly. Funded by the National Science Foundation, INDOT and Purdue are working with the German firm Magment to make magnetized cement called magment.

The project is still in its first phases of testing, but the firm says that magment “offers an innovative magnetizable concrete product consisting of cement and recycled particles called ferrite.” Magment’s site adds that the product has “wireless transmission efficiency, standard road-building installation costs, enables universal charging, is all-weather, has a high thermal conductivity, and is vandalism-proof”. The testing, which will be conducted by the Purdue's Joint Transportation Research Program, is expected to begin sometime before the end of summer.

The development of magnetized cement will surely have a big impact on reducing pollution in the road, but a lot of continuous research needs to be done before mass production is approved.

What do you think of this environmental breakthrough?

Hiroshima Day: How Can Concrete Structures Protect You From Nuclear Radiation?

Today marks the 76th year since the Hiroshima Bombing during World War II. The atomic bomb, Little Boy, was detonated 580 meters above Hiroshima, Japan. The bomb was made from 64 kg of highly enriched uranium-235 which is equivalent to 16,000 tons of TNT. Ninety percent of the city was destroyed. At least 80,000 people immediately died from the explosion, some of them leaving shadows on the concrete sidewalks and buildings around them. In the next few weeks and months, tens of thousands died due to radiation exposure.

As the time passed, most of the shadows etched into the concrete of Hiroshima weathered away. Several of the nuclear shadows have been preserved and moved to the Hiroshima Peace Memorial Museum, a reminder of the harmful effects of nuclear radiation.

After the war, subsequent research and tests were conducted to improve public awareness and safety in case of a nuclear fallout. According to the American Nuclear Society, in the event of a nuclear attack, the three general guidelines for controlling exposure to radiation are as follows:

1. minimizing exposure time
2. maximizing distance from the radiation source
3. having a shield

How can concrete help you in such situations?

3D Printed Concrete Bridge opens in Venice, Italy

Striatus is a freestanding 3D Printed concrete bridge found in Venice. The 16-meter long bridge is built by Zaha Hadid Architects and the Block Research Group. Without the help of reinforcements nor mortar, the Striatus bridge uses compression and gravity to hold its form.

This 3D Printed bridge is more than just display. It is made of 3D Printed hollow blocks to reduce typical material use and consumption. The bridge aims to exhibit the capabilities of unreinforced concrete and computational design.

What is 3D Printed Concrete?

The Hamilton Fashion Building

Did you know?

The Hamilton Fashion Building (aka Olsen Building) in Ermita, Manila was the first of its kind to used reinforced concrete in its construction.

Reinforced concrete is a combination of steel (rods, bars, mesh, etc.) and concrete. The tensile strength of the steel combined with the compressive strength of concrete allows a building to better sustain different forms of stress and strain over a longer period of time. This can be observed with the Hamilton Fashion Building. While the top floor is almost completely gone and nothing remains but its outer shells, the fact that parts of it are still standing after numerous wars, earthquakes, and typhoons act as testament to its stuctural strength.

The design of the Hamilton Fashion Building is attributed to National Artist for Architecture Pablo Antonio. Several groups are working for its preservation as it still stands to be one of the most iconic buildings which reminds us of what Manila used to be.

Water to Concrete: friends or foes?

Last Friday, PAGASA has announced the onset of the rainy season. This means more frequent precipitation in the form of thunderstorms and cyclones. How does rain and moisture affect structures and building made with concrete?

Water is an important component of concrete. Water is essential for the proper curing and binding of cement and aggregates to form concrete. It is estimated that around 14 to 21% of concrete is water. However, after the mixture has hardened, water can act as a deleterious substance to concrete structures.

Alkali-silica reaction gel (ASR) is one type of concrete cancer worsened by excessive moisture in already hardened cement. The expansion and swelling of ASR could lead to the formation of cracks that would contribute to further deterioration of concrete. Sweating slab syndrome is also an effect of uncontrolled humidity which can pose a great risk to people working inside buildings.

How to prevent water damage in concrete?

Composition of Concrete

Concrete is one of the most common construction materials worldwide. It is a mixture of coarse and fine aggregates, cement, water, air, and (mineral admixtures).

Ottawa Sand: The ASTM standard sand

As with any laboratory testing, standards are important to ensure accuracy in the results. Sand is utilized in testing hydraulic cement to; increase the surface area, allowing cementing materials to adhere and spread, and to prevent shrinkage and cracks in the mortar.

One of the most famous standard sand used for physical testing of hydraulic cement, as set by international organizations such as the ASTM, is the Ottawa Sand. This is a fine to medium grained, well-rounded, pure, and white to colorless quartz deposit mined from the St. Peter Sandstone Formation in Ottawa, Illinois. What makes Ottawa sand desirable is its purity that prevents the possibility of unwanted reactions during testing and the well-roundedness that helps produce workable mortar.

Water and the Concrete mix

Water is essential for the hydration of cement particles and controlling the workability of concrete .

Impurities in the mixing water can affect both concrete strength and durability.

Presence of high amounts of chlorides and alkalies may result to corrosion of steel reinforcement and formation of alkali-silica gel with the presence of reactive aggregates, respectively. High amounts of silt or suspended particles in water can negatively impact concrete strength.

ASTM C1602 provides criteria for the acceptance of water to be used in concrete.