Cement Admixture with Tin Sulfate for Chromium Reduction
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Solution Overview
Problem
Incinerated sewage sludge ashes in concrete products contain phosphorus and hexavalent chromium, leading to reduced initial strength and hexavalent chromium dissolution, with existing tin sulfate solutions being less effective and deteriorating over time due to reaction with free lime and moisture.
Innovation Solution
A cement admixture combining an expanding material with tin sulfates, where the expanding material is treated with carbon dioxide to form calcium carbonate, and a shrinkage reducer is used to enhance the effectiveness of hexavalent chromium reduction and maintain strength even during storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tin sulfates are used to reduce hexavalent chromium, then hexavalent chromium reduction effect is improved, but the effectiveness deteriorates during storage due to reaction with free lime and moisture
Solution Approach 1:
The patent introduces an expanding agent as an intermediary substance that reacts with free lime and moisture before tin sulfate can react with them. This intermediary action protects tin sulfate from premature reaction during storage, maintaining its effectiveness for hexavalent chromium reduction while allowing it to remain stable in the cement mixture during storage period
Solution Approach 2:
The expanding agent performs preliminary action by reacting with free lime and moisture during the storage period, creating a protective effect that prevents tin sulfate from reacting with these substances later. This preliminary reaction ensures that when the cement concrete is formed, tin sulfate remains active and effective for reducing hexavalent chromium
2Adaptability or versatility
If phosphorus is present in incinerated sewage sludge ashes, then concrete production is enabled, but initial strength is reduced due to retarding cement reactions
Solution Approach 1:
The patent extracts the harmful retarding effect of phosphorus by introducing tin sulfate, which specifically targets and reacts with hexavalent chromium (the harmful component in incinerated sewage sludge ashes). This selective extraction allows the beneficial phosphorus content to remain while removing the harmful hexavalent chromium, enabling use of incinerated sewage sludge ashes without the strength penalty
Solution Approach 2:
The patent converts the harmful effect of phosphorus (which retards cement reactions and reduces initial strength) into a beneficial situation by using tin sulfate to specifically target and reduce hexavalent chromium. The hexavalent chromium reduction becomes the primary beneficial effect, allowing the phosphorus-containing incinerated sewage sludge ashes to be used without compromising initial strength
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The cement admixture achieves high initial strength and significant hexavalent chromium reduction, maintaining effectiveness over time, even when stored, through the synergistic effect of the expanding material and tin sulfates, while preventing hexavalent chromium dissolution.
Implementation Method 1
the expanding material is treated with carbon dioxide to form calcium carbonate
Implementation Method 2
tin sulfates provide an effective material capable of reducing hexa-valent chromium dissolving out from cement concrete
Implementation Method 3
having high effects on reductions of hexavalent chromium, and keeping the effect on reductions of hexavalent chromium substantially intact
Data Source
AI summary
The invention provides a cement admixture that improves the ability of concrete to bring about high initial strength, works in favor of enhancing the effect on hexavalent chromium reductions, and is less likely to decrease in the effect on hexavalent chromium reductions even upon storage as well as a method for reducing hexavalent chromium. The invention is embodied as (1) A cement admixture, characterized by comprising an expanding material containing free lime, a hydraulic compound and calcium sulfate anhydrite, and a tin sulfate-containing substance; (2) The cement admixture according to (1), characterized in that the tin sulfate-containing substance is contained in an amount of 0.2 to 8 parts by mass - as calculated on a tin sulfate basis - in a total of 100 parts by mass of the expanding material and the tin sulfate-containing substance; (3) The cement admixture according to (1) or (2), characterized in that the expanding material has been treated with carbon dioxide gas to form calcium carbonate therein; (4) The cement admixture according to any one of (1) to (3), characterized in that the expanding material has been surface treated with a shrinkage reducer; (5) A cement composition, characterized by containing cement, and the cement admixture according to any one of (1) to (4); and (6) A method for reducing hexavalent chromium, characterized by use of the cement composition according to (5).