Frequently Asked Questions

What is the correct dose rate for Dr. Fixit Pidiproof LW+ in concrete and mortar and what happens if too much or too little is used?

The standard recommended dose rate for Dr. Fixit Pidiproof LW+ is approximately 200 ml per 50 kg bag of cement (equivalent to approximately 0.4 percent by weight of cement) for general waterproofing of concrete and plaster mixes. This dose rate applies to a standard concrete mix (1:2:4 nominal mix or equivalent M20 to M25 design mix) and to a standard 1:3 or 1:4 cement-sand plaster mix used for waterproof plastering of water tanks, toilet floors, and wet walls. For more demanding waterproofing applications such as underwater structural concrete, swimming pool shells, or foundation concrete in highly aggressive soil conditions, the dose rate may be increased to 300 to 400 ml per 50 kg bag of cement — consult the Dr. Fixit technical data sheet or contact Space Arc Engineering for application-specific guidance. If too little Pidiproof LW+ is used: the waterproofing and plasticising effect is reduced proportionally. Below approximately 150 ml per bag, the performance benefit is marginal and the cost advantage of using the product is lost. If too much Pidiproof LW+ is used: overdosing with liquid integral waterproofing admixtures beyond approximately 500 ml per bag can cause excessive air entrainment and set retardation in the concrete or mortar, leading to reduced strength, extended workability time (which may be misinterpreted by site operatives as poor quality concrete), and potential segregation in very wet mixes. Always add Pidiproof LW+ to the gauging water before mixing — this ensures uniform distribution throughout the batch. Never add it dry to the dry cement and aggregate or pour it directly into the mixer drum without pre-mixing in water, as this leads to non-uniform distribution with concentrated patches that can cause localised set issues.

Can Dr. Fixit Pidiproof LW+ alone waterproof an overhead water tank or is a surface treatment also required?

Dr. Fixit Pidiproof LW+ used as an integral admixture in all concrete and plaster components of an overhead water tank significantly reduces the permeability of the tank shell and provides a cost-effective and durable baseline waterproofing. However, for a complete and reliable waterproofing system on an overhead water tank, Pidiproof LW+ alone in the concrete and plaster mix should be supplemented with a surface-applied waterproofing treatment on the interior face of the tank. The reason is that construction joints (where two pours of concrete meet — e.g., base slab to wall joint, or pour sequence joints in large tanks), formwork tie holes, crack at corners, and any areas where the plaster coat is thin or poorly compacted are weaknesses where water can penetrate through the tank wall even if the bulk concrete is highly waterproofed with Pidiproof LW+. A complete overhead water tank waterproofing system recommended by Space Arc Engineering would be: Concrete mix: use Pidiproof LW+ at 200 ml per 50 kg cement bag throughout all concrete in the tank shell. Internal plaster: apply 12 mm two-coat cement-sand plaster (1:3 mix) with Pidiproof LW+ at 200 ml per bag on the interior walls and floor. Surface treatment: apply Dr. Fixit Pidifin 2K (two-component flexible cementitious waterproofing) or an approved crystalline waterproofing treatment over the internal plastered surface as a final water-retaining membrane layer. This combination provides redundant waterproofing protection and ensures that even if one layer has a localised weakness, the next layer intercepts the water.