Dayang’s Cement Coloring which has been
together with the history of cement
Actual Sample of Full Color
Click the photo for detailed product information
Major Products
DY RED/ DY YELLOW
Mainly contains iron(III) oxide(Fe2O3), has excellent chemical properties, is cheap, and is used most in road pavement material coloring.
DY GREEN/ DY BLUE
Mainly contains the beginning color of the Copper Phthalocyanine series with added characteristics of iron(III) oxide(Fe2O3), silica(SiO2), aluminum oxide(Al2O3), and developed as a substitute for chromium oxide and cobalt blue. It has great durability such as light stability, weatherproofing, and so on, yet relatively cheap, so it is widely used for its high economic value.
DY BLACK/ DY OXIDE BLACK
DY BLACK is a product with added the appropriate characteristic of Carbon Black and surfactant for familiarity with the cement which has a cheaper cost, while IRON OXIDE BLACK mainly contains iron(III) oxide and has better light stability, weatherproofing, and thermostability.
Physical, Chemical Characteristic and Durability
Q&A
Q. What pigment is good for cement products?
Pigments used in cement, concrete products like interlocking blocks, reinforced earth, and so on need to meet certain conditions. Cement products are mostly constructed outdoors, exposed to direct sunlight, wind, rain, and temperature fluctuations, so you need to use good quality pigment that has light stability, waterproofness, and weatherproofing. It needs to stand the high alkalinity of cement, and not be affected by the hydration effect during cure. Furthermore, it to be easily combined with cement and aggregate with big special gravity, it needs adequate special gravity and hydrophile property. Pigments that meet these conditions are usually mineral pigments using metallic oxides like iron oxide, along with organic pigments with a modification process recently.
Q. How and how much pigment do we use when coloring cement product?
Pigments are put in when combining aggregates like cement, sand, and gravel. Also, the pigment is put proportionately to the cement amount. Normally, we recommend using 6~8% of cement weight to be used. Any great pigment with excellent properties cannot avoid decolorization after being exposed to long-term environmental change, it is not suggested to use an extremely minimal amount for minimal coloring
Q. What is laitance and why does it form?
Laitance is a white substance resulting from the precipitation of soluble substances in mortar or concrete passing through the solution and moving to the surface, which then gets dried up, or deposits on the surface from the combination with the carbon gas in the air. It is called a ‘white flower’ in Korean because it looks like a white flower that has bloomed. There is primary laitance which is from the precipitation of the water-dissolved laitance substance being dried up on the hardening surface like that of the concrete and secondary laitance from the precipitation of outside water intrusion and drawing out the soluble substance to the surface. Primary and secondary laitance both leave laitance substances by water that contains soluble substances evaporating and drying up on the hardening surface. The substance that causes laitance differs in location, cure, conditions, aggregate, or admixtures, but mainly is due to calcium carbonate and sodium silicate. The primary laitance happens at the beginning stage of cement and concrete hardening and mainly is due to calcium hydroxide and soluble alkali which are massively generated during the hardening. The secondary laitance may be due to the calcium carbonate only, or calcium hydroxide, silicic acid compound, and carbon compound in combination. Also, there are cases where these substances absorb the carbon gas in the air to form carbon compounds. Carbonate mineral forms when the calcium hydroxide and silicate from the cement hardening come out and absorb carbon gas. Alkaline salt is easily dissolved in water so often gets washed away by rain, but when the calcium hydroxide reacts with carbon gas in the air and form calcium carbonate, it becomes non-soluble and stays forever on the surface.
Q. What is the reason for the laitance?
The laitance occurs when the causing substance moves to the surface as a solution resulting from the water used in combination or water permeating from outside, which occurs more easily as the movement is unhindered. Also, the laitance occurs as the water on the cement hardening evaporates, so the phenomenon becomes more prevalent when the environment is suitable for surface drying. To summarize, the laitance occurs in low temperatures (calcium hydroxide is more soluble in low temperatures), high humidity, wind, and shadowy environment. The laitance never occurs where drying is unavailable. Also, the laitance is less common when the drying happens at a fast pace. This is because the surface of the cement hardening is quickly dried, preventing the inside solution from spreading, resulting in laitance happening just inside the surface, not on the actual surface. Generally, the laitance is more prevalent in the winter after rain because the aforementioned conditions are met. Another reason for laitance’s winter prevalence is likewise: 1. The hydration reaction of cement happens much slower in low temperatures, delaying the creation of a hydration reaction substance that should block the capillary tube and stop the water flow. 2. When unreacted cement remains for a long time, the calcium hydroxide is continuously supplied in large quantities. 3. The solubility of calcium hydroxide is much higher at low temperatures. The sunnier side has less laitance occurring and the shadowy side with more laitance means that the shadowy side has more conditions that are met for laitance, like drying speed, including inner drying, surface drying, hardening speed, etc. The laitance also occurs in summer but is not as prevalent as in winter. The curing period is another factor that affects the occurrence of laitance. During the early stages of curing, the surface is wet, not drying up quickly. Substances needed for laitance reside in large quantities inside the cement hardening and are not fixed. Also, the structure of the cement hardening is not concrete, so the solution moves freely supplying substance for laitance on the surface. When the exterior conditions for the laitance are met during the early stages of curing, the laitance becomes more prevalent. According to research, these facts are known excluding what has been already described: 1. It has nothing to do with the type of types of cement. 2. It is not proportional to the amount of alkalinity in the cement. 3. It is irrelevant to the fineness of the cement. 4. The free lime in the cement does not affect the laitance. 5. Choose the aggregate with low absorption and no soluble salt. 6. The water ratio is a huge factor contributing to the laitance, so construct with a low water ratio for the structure to be more concrete. 7. Some compounds are known to affect the laitance.
Q. How do you remove the laitance occurred on the interlocking blocks?
Primary laitance is a soluble substance so it can be washed with water easily, but the secondary laitance is mainly due to calcium carbonate, so it is hard to be removed unless by an acid washing with chloric acid, etc. However, even if you leave it as is, it often gets removed naturally according to this chemical equation after 2~3 months by the carbonic acid in the rain, then turned into calcium hydroxide carbonate, which is a soluble substance that can be washed away in the rain. [CaCO3 + CO2 + H2O → Ca(HCO3)2] However, with extreme cases of laitance, wash likewise with chloric acid: 1. Apply enough water on the blocks’ surface. 2. Spray chloric acid of 2~3% concentration and brush the surface. 3. Wash the surface with lots of water. 4. Dry as fast as possible. (Wash on a sunny day.
Q. What laitance inhibitors are there?
The laitance on concrete has been researched as a question for a very long time, but the fundamental solution is yet to be discovered. Hence, the realistic countermeasure is to understand why the laitance occurs and prevent the occurrence by combining available methods. On this note, these are some laitance inhibitors on the market. Currently, there are compounds and ointments as the main inhibitors, along with waterproof agents and penetrating water repellents which prevent the occurrence of laitance with its by-effect. 1. Ointment-type laitance inhibitor: LiCL as the main substance, it is an acid with pH2~3 which reacts with Ca, the main substance responsible for the laitance, and removes it and combining free lime with additional substances forming a layer, preventing another laitance. 2. Ointment-type laitance inhibitor: Forms a layer on the surface, preventing contact with carbon gas or calcium salts. 3. Compound-type laitance inhibitor: Gives water repellency, combines metallic salts by emulsifying to block the capillary tube inside, disassembles the causing substance by reacting with calcium salt that flows out, and prevents surface evaporation of water, blocking the capillary tube by creating polymer. 4. Penetrating water repellent: when applied on the concrete surface, it forms an anti-absorbent layer on the surface, preventing waterlogging from outside and penetration of chlorides to protect the structure. There are mainly silicon type, acrylic type, and compound type in sue, with silane type of silicon compound being more commonly introduced recently. The silane compound contains alkalinity which has water repellency, so when it is applied on the surface, it reacts with water and calcium hydroxide, which then penetrates inside forming a hard water-resistant layer, preventing the penetration of water, which is the cause of the secondary laitance.