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Water Retention in Plastering Mortar: How HPMC Influences Workability and Bond Strength

 1. Why Is Water Retention Critical in Plastering Mortar? Plastering mortar performance depends not only on cement, sand, and other raw materials, but also on its ability to retain water. When applied to substrates such as autoclaved aerated concrete (AAC) blocks, lightweight wall panels, or cast-in-place concrete, the substrate's water absorption characteristics directly influence moisture movement within the mortar. If the substrate absorbs water too quickly, the mortar may lose consistency and workability, while insufficient moisture may interfere with cement hydration. Under unfavorable conditions, these effects can increase the risk of poor interfacial bonding, cracking, and hollow spots. Cellulose ether, particularly hydroxypropyl methylcellulose (HPMC), is an important functional additive for improving water retention and workability in plastering mortar. HPMC increases the viscosity of the aqueous phase and helps retain moisture, slowing water migration and maintaining the ...
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Why Can Concrete Crack Even When It Is Water-Cured Frequently?

 What Really Matters in Hot-Weather Concrete Curing During summer construction, what is one of the biggest concerns for fresh concrete? Many people immediately think: insufficient moisture. So after placing concrete, they keep spraying or watering the surface, assuming that more water means better curing and fewer cracks. But sometimes, the opposite seems to happen: The concrete is watered frequently, yet cracks still appear. So, is the problem really a lack of water? Not necessarily. For concrete exposed to hot-weather conditions, curing needs to address two things together: Moisture control + temperature control. 01 | Why Is Concrete More Prone to Cracking in Summer? High temperatures, strong sunlight, low humidity, and wind can accelerate moisture loss from the concrete surface. At the same time, cement hydration continues to generate heat, which can create a temperature difference between the interior and the surface of the concrete. If the surface cools and contracts significa...
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Not All Air Bubbles in Concrete Are Harmful: Which Ones Should You Really Worry About?

After formwork is removed, air bubbles, bugholes, or small surface voids may appear on concrete. The first question is often: Was the concrete insufficiently vibrated? Not necessarily. Not all air bubbles in concrete are harmful. What really matters is their size, distribution, location, and cause. 01 | Some Air Bubbles Are Actually Beneficial Tiny air bubbles introduced by air-entraining agents are generally small and evenly distributed. In freeze-thaw environments, these bubbles can provide small pressure-relief spaces for ice expansion and help improve the concrete's freeze-thaw resistance. So, fewer air bubbles do not always mean better concrete. Beneficial microbubbles do not need to be completely removed. 02 | Large Air Bubbles Are the Ones That Need Attention Large and concentrated air bubbles may affect concrete compactness and surface appearance. They may be related to: Admixture system and dosage Mixing speed and mixing time Air introduced during mixing Placement and vibr...
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How Thick Should Plastering Mortar Be? Key Thickness Control Tips

 There is no single plaster thickness for every project. The appropriate thickness depends on the substrate, application area, mortar type, construction method and project requirements.​ In practice, three points are important: layer thickness, total thickness and reinforcement when necessary.​ 1. How Thick Should Each Layer Be? Plaster should not be applied in an excessively thick layer at once.​ According to JGJ/T 220-2010, cement plastering mortar is generally applied at 5–7 mm per layer, while cement-lime plastering mortar is generally 7–9 mm per layer.​ When greater thickness is required for leveling, use multiple layers instead of one thick application.​ 2. Typical Total Thickness Common reference values include:​ • Ordinary interior wall plastering: ≤20 mm​ • High-grade interior plastering: ≤25 mm​ • Exterior wall surface: ≤20 mm​ • Exterior plinth and similar areas: ≤25 mm​ • Cast-in-place concrete ceiling: ≤5 mm​ • Precast concrete or panel ceiling: ≤10 mm​ Actual projects...
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Concrete Curing Is Not About Using More Water: The Key Is Controlling Moisture and Temperature

 “Just add more water—the more you water concrete, the better it will cure.” This is a common idea on many construction sites. But in practice, more water does not automatically mean better curing. The real purpose of concrete curing is to maintain suitable moisture and temperature conditions during early-age hardening, allowing cement hydration to continue while reducing the risk of excessive moisture loss, shrinkage, and temperature-related cracking.                                           01 | Why Doesn't More Water Always Mean Better Curing? Fresh concrete has relatively low surface strength during the early stages. If a newly placed surface is exposed to strong water flow, especially when the water temperature is significantly different from the concrete temperature, rapid temperature changes may increase the risk of early-age cracking. Strong water flow may also disturb ...
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What Is the Difference Between Rigid and Flexible Waterproof Coatings?

 # Rigid or Flexible Waterproofing? Understanding the Differences and Applications Rigid and flexible waterproof coatings are widely used in construction waterproofing. Both help reduce water penetration, but they differ in material composition, cured properties, waterproofing principles, and suitable applications. Understanding these differences helps contractors and manufacturers select the right waterproofing system for different substrate conditions and project requirements. ## Rigid vs. Flexible Waterproof Coatings Rigid waterproof coatings are generally based on cement or other inorganic binders, combined with suitable additives and functional materials. Some products may also contain a small amount of polymer. After curing, these materials form a relatively hard and dense waterproof layer with limited elasticity and elongation. Rigid waterproofing mainly relies on the dense hardened structure formed during cement hydration to reduce water penetration. When the substrate is s...
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External Wall Insulation Installation: Key Requirements and Common Mistakes

 Cracking, hollow areas, water penetration, and even detachment are among the most common problems found in external wall insulation projects. Many people assume that these failures are caused only by the insulation material itself. However, the long-term performance of an External Thermal Insulation Composite System, or ETICS, depends on much more than the insulation board. Substrate preparation, adhesive application, insulation board installation, mechanical anchors, fiberglass mesh reinforcement, base coat application, finishing work, and final quality inspection all play an important role. ETICS is a complete building system rather than simply attaching insulation boards to a wall. A mistake in any part of the installation process can affect bonding strength, crack resistance, weather resistance, durability, and long-term safety. For this reason, external wall insulation projects should always be installed and inspected according to applicable local regulations, approved projec...
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